LABORATORY MANUAL OF TESTING MATERIALS % Qraw'3/illBook (a 7n& PUBLISHERS OF BOOKS F O R_/ Coal Age * Electric Railway Journal Electrical World * Engineering News-Record American Machinist; v Ingenieria Internacional Engineering & Mining Journal ^ Power Chemical 6 Metallurgical Engineering Electrical Merchandising LABORATORY MANUAL OF TESTING MATERIALS BY WILLIAM KENDRICK HATT, C.E., Pn.D. MEMBER AMERICAN SOCIETY CIVIL ENGINEERS; PROFESSOR OF CIVIL ENGINEERING, AND DIRECTOR OF LABORATORY FOR TESTING MATERIALS, PURDUE UNIVERSITY AND H. H. SCOFIELD, M.E. ASSISTANT PROFESSOR OF CIVIL ENGINEERING IN CHARGE OF TESTING MATERIALS, COLLEGE OF CIVIL ENGINEERING, CORNELL UNIVERSITY. MEMBER: AMERICAN SOCIETY FOR TESTING MATERIALS, SOCIETY OF AUTOMOTIVE ENGINEERS SFCOND EDITION McGRAW-HILL BOOK COMPANY, INC. NEW YORK: 239 WEST 39TH STREET LONDON: 6 & 8 BOUVERIE ST., E. C. 4 1920 COPYRIGHT, 1913, 1920, BY THE MCGRAW-HILL BOOK COMPANY, INC. THK M > >' 1. K PREHS YOKK PA PREFACE TO SECOND EDITION The methods of tests, specifications and related data have been revised and brought up to date. This has been particularly necessary in the field of concrete where developments have been rapid in recent years. It has been the intention to make the new edition use- ful in more than one institution by eliminating certain details of directions and apparatus which would be more or less peculiar to any one laboratory. It is felt that the generalized directions while being helpful as a guide in class work and investigations, should also lead to a more independent character of work upon the part of the student. 435851. PREFACE TO FIRST EDITION This manual is the outcome of the operation, through eighteen years, of the Laboratory for Testing Materials of Purdue University. During this time several in- structors, temporarily serving the laboratory, have improved its practice. Especial mention should be made of the services of the late Professor Hancock, whose untimely death deprived the science of testing materials of a very able and patient investigator, and his colleagues of a good friend. Professor Yeoman, now of Valparaiso University, did valuable service in the organization of the work of the cement laboratory. The authors are indebted to Professor Poorman of Purdue University, for valuable suggestions. In its original form the manual was published by the senior author of this volume ; and later, with the assist- ance of Professor Scofield, the manual was enlarged, and was found useful in several universities. Now the authors have availed themselves of the assistance of the present publishers to enlarge the work. The list of ex- periments has been increased, and a more complete treatment of machines and apparatus added. One purpose of the manual is to relieve the instructor from the necessity of explaining the details of mechanical procedure, and so to free his time for matters of greater educational importance. It is also hoped by the authors that the practitioner will find the volume of convenient use. LAFAYETTE, IND., August, 1913. VI CONTENTS PAGE PREFACE ..... v CHAPTER I. GENERAL 1 CHAPTER II. GENERAL INSTRUCTIONS 4 Instructions for Writing Reports 7 CHAPTER III. DEFINITIONS 10 Stress 10 Elasticity 12 Resilience 14 CHAPTER IV. MATERIALS STRESSED BEYOND THE ELASTIC LIMIT 16 Fractures under Tension 17 Fractures under Compression 17 Fractures under Shear 19 CHAPTER V. TESTING AISD TESTING MACHINES ..... 20 Technical Qualities of Materials 20 Testing Machines 21 (a) Holding the Specimen 21 (6) Method of Applying Lead 27 (c) Weighing Mechanisms 35 Extenso meters and Other Deformation Instruments . . 37 CHAPTER VI. LIST OF EXPERIMENTS 44 Experiments for Advanced Work 46 CHAPTER VII. INSTRUCTIONS FOR PERFORMING EXPRRI MENTS . 48 Article 1. Testing Machines 48 A-l. Study of Testing Machines 48 A-2. Calibration of Testing Machines 50 A-3. Calibration of Extensometers 51 vii Vlll PA.GK Article 2. Iron and Steel .............. 52 B-l. Tension Test of Iron and Steel ....... 52 B-2. Tension Test of Cast Iron or Steel Castings . . 55 B-3. Autographic Tension Test of Iron or Steel . . 50 B-4. Tension Test with Extensometer ...... 57 B-5. Experiment in Torsion ........... 59 B-6. Test of Wire Cable ............ 01 B-7. Compression of Helical Spring ....... 02 B-8. Effect of Overstrain on Yield Point of Steel . 03 J3-9. Flexure Test of Cast Iron or Steel ...... 04 B-10. Flexure Test of Brake Beam ........ 05 B-ll. Vibration Test of Staybolt Iron ...... 05 Articles. Test of Wood. ...... .......... 60 C-l. Instructions for Laboratory Exercise for the Identification of Woods .......... 66 C-2. Compression of Short Wood Blocks Parallel to Grain .................. 67 C-3. Compression of Wood Perpendicular to Grain . 69 C-4. Test of Wood Columns .......... 70 C-5. Flexure Test of Small Wooden Beams .... 71 C-6. Flexure Test of Large Wooden Beams .... 73 C-7. Impact Test of Wooden Beams ....... 74 C-8. Abrasion Test of Wood ...... .... 75 Article 4. Tests of Cements ............. 70 D-l. Test of Specific Gravity of Cement ...... 82 D-2. Test of Fineness of Grinding ........ 83 D-3. Normal Consistency ............ 85 D-4. Time of Setting .............. 88 D-5. Tests for Soundness ............ 87 D-0. Cement and Cement Mortars in Tension ... 89 D-7. Cement and Cement Mortars in Compression 92 Articles. Study of Aggregates ............ 93 Notes on Sampling of Aggregates ......... 93 E-2. Test of Sand for Cleanness ......... 90 E-3. Weight of Aggregates . . . ' ....... 99 E-4. Specific Gravity of Various Materials Used as an Aggregate in Concrete ......... 102 E-5. Determination of Voids in Aggregates .... 105 E-6. Effect of Moisture in Aggregates on Per Cent. of Voids . . . 106 CONTENTS ix PAGE E-7. Study of Sieves 107 E-8. Sieve Analysis of Aggregates 109 E-9. Hand Mixing of Concrete 113 E-10. Mixing Concrete by Machine Mixer . . . .114 E-ll. Amount of Water Required for Mixing . . .115 Article 6. Proportioning Mortars and Concretes . . . .119 E-12. Theory of Proportioning Concrete 119 E-13. Mixture of Fine and Coarse Material . . . . 121 E-14. Proportioning Concrete by Method of Sieve Analysis ... 122 K-15. Strength in Relation to Density 127 E-16. Surface Area of Aggregates 128 E-17. Fineness Modulus of Aggregates 130 Article 7. Tests of Concrete and Other Brittle Materials 132 F-l. The Value of a Sand or Other Fine Aggregate as Shown by Strength Tests 132 F-2. Compressive Strength of Concrete 133 F-3. Compression Test Brittle Materials 134 F-4. Compression of Brittle Materials with Defor- mation Measurement 136 F-5. Reinforced Concrete Beam Test 137 F-6. Bond Strength of Steel in Concrete . . . . .138 F-7. Test of Concrete Reinforcing Fabric 139 F-8. Cross Bending and Compression Tests of Building Brick 139 Article 8. Tests of Road Materials 140 G-l. Rattler Test of Paving Brick ........ 140 G-2. Absorption Test 142 G-3. Abrasion Test of Road Materials 142 G-4. Cementation Test of Rock or Gravel or Materials of Like Nature 143 G-5. Hardness Test of Rock Road Materials Dorry Test , 145 G-6. Standard Toughness Test for Road Rock . . . 146 APPENDIX I. COMMON FORMULAS 148 APPENDIX II. Specifications for Materials 151 Steel and Iron 151 Methods for Metallographic Tests of Metals . ... 155 Portland Cement .156 x CONTENTS PAGE A.R.E.A. Aggregates 159 Indiana State Highway Commission for Concrete Roads ICO APPENDIX III. STANDARD FORMS OF TEST PIECES ... 163 APPENDIX IV. STRENGTH TABLES 165 Iron and Steel 166 Copper and Alloys 167 StructuralTimber 168 Stone and Brick 166 INDEX ... . 171 LABORATORY MANUAL OF TESTING MATERIALS CHAPTER I GENERAL 1. The student should obtain a knowledge of materials by handling them and watching their behavior under stress. From the appearance before and after test, he is led to recognize the nature of normal and defective samples. This knowledge will give character to the work of engineering design, and will be of service in work of inspection. 2. A knowledge of the technique of testing materials should be gained, by which he may know afterwards if proper methods are being used in cases that come under his inspection, and by which he may judge the signifi- cance of results of the tests of material submitted to him. 3. A training should result in precise methods of observation. 4. The class-room instruction in Applied Mechanics which should precede or accompany this course, is rein- forced with concrete knowledge of things and properties, which are otherwise only words denned in text-books. The application of theoretical analysis to the tests per- formed in the laboratory becomes of individual interest and is fixed in the mind. Discrepancies between theoret- ical deductions and results of tests of actual material as 1 MATERIALS supplied to the market also become evident. Many of the fundamental facts relating to metals, such as the relative stiffness of hard and soft steel, the elevation of the yield point, and the lowering of the elastic limit through overstrain can also be brought to the student's notice by a few well-selected experiments. 5. The report which accompanies the investigational features of the work, affords practice in setting forth re- sults in a clear business-like way and should aid the student in forming at least the fundamentals of a style which will be later useful to him. 6. The student should refer to standard text-books and specifications to compare the results obtained with recorded data. A partial list of specifications suitable for use is as follows : Specifications in Year Book of American Society for Testing Materials. Specifications in Year Book of State Highway Commissions. Materials of Construction by A. P. Mills. Materials of Construction by J. B. Johnson. Materials of Construction by Thurston. Materials of Construction by Upton. Mechanics of Materials by M. Merriman. Applied Mechanics by A. P. Poorman. Concrete Plain and Reinforced by Taylor and Thompson. Reinforced Concrete by G. A. Hool. Concrete Engineers' Handbook by Hool and Johnson. Mechanical Properties of Woods grown in the United States Bulletin No. 566 U. S. Dept. of Agriculture. 7. Thesis work in testing materials presents a read} r and attractive medium by which students can receive some training in proper methods of planning and execut- ing experimental investigations. The work may be individual, or performed by groups of students, and GENERAL O the expense of material is small. If the professor is interested in some one field of investigation and system- atically plans for a term of years, the theses in time are of use in extending knowledge. The method of administering thesis work in general involves the following steps: A list of problems, to which, on account of limitations of equipment and the desire to concentrate, the work of the laboratory should be confined, is prepared early in the year. Theses sub- jects are generally chosen from this list by students. When a subject is chosen by a student, a thesis outline is prepared by the professor in consultation with the student, in which the problem is clearly stated; the authorities, if any, cited ; a list of literature, or directions to main source of information given; and the main plan of attack fairly definitely indicated. Details of apparatus, etc., are generally left to the student. A student may present a subject of his own choice. The written thesis covers a clear and logical account of the purpose of the thesis; the material tested; the methods and machines, with a discussion or error; the actual results; the analysis and presentation of the results; and the conclusions therefrom. CHAPTER II GENERAL INSTRUCTIONS Preliminary Notes. In all tests, first carefully ex- amine the material. Measure, and note characteristics and defects, if any. If this is not done before the speci- men is broken, the test is useless. Note the serial number if any. The character of the log sheet will be considered in grading the report. The student should understand the manipulation and reading of all instruments used in each test. Enough readings should be taken to accurately deter- mine the stress-strain curve. Calculate from table of average strengths of materials, see appendix, the incre- ment of loading required to give at least 18 readings. When quantities being measured are changing rapidly, intervals must be shortened. Specimens upon which further observations are to be made should be carefully marked and place in assigned case. If the reports are to be written in the laboratory during the assigned period, all notes and data, together with unfinished reports, must be left in the filing case. Operation of Machines During Test. Preliminary to every test, each student should become familiar with the operation and mechanism of the testing machine to be used. Balance poise at zero with test piece in the machine but free from the pulling head in every way. GENERAL INSTRUCTIONS All readings upon test piece for a certain load should be taken when the beam is balanced at the load and at no other time. The finger may be used to lift the beam slightly and so give warning which will prevent the loads being exceeded. The speed of applying the load should be such that the beam may be kept balanced, otherwise the readings will be of doubtful accuracy. Often after the elastic limit has been reached a faster speed may be used and much time saved. Any consist- ent speed is allowable if the load readings are accurate, except in experiments for which the machine speed to be used is stated in the instructions. Students should be sure that machines are properly thrown out of gear when the test is finished. CAUTION. Testing machines have upon different occasions been left by the operators with countershaft running and the friction clutches thrown in, so that the machines continued running. The result has usually been that some part of the machine was broken. The operator will take especial care that this does not occur with machines for which he is responsible. He will be charged with all the repairs made necessary by careless handling. Note Keeping.- The standard data sheets will in most cases be used for note keeping. In the case of most of the experiments the original log of the test will be required as a part of the report. Carbon copies of the original log made in the laboratory will be acceptable in case the work is of such a character that only one of two men can record the data obtained. Neat and orderly notes and test logs will be insisted upon. Reports. Reports will be written in ink or type- written on one side only of the standard 8" X LABORATORY MANUAL OF TESTING MATERIALS paper and placed in the regular manila cover. On the outside of the cover will appear the required information in lettering. Clearness and order of statement, legibility of writing, lettering and neatness will receive due attention in marking the report. In plotting stress-strain curves, select such a scale as can easily be read by inspection, in decimals. State plainly the scale of coordinates. Use the bow pen to circle the points plotted, and draw curves with instru- ments. Use India ink for curves and lettering on the curve sheets. Avoid lines from point to point. Max. Y.P. ^ Deformation > > Deformation ^ FIG. 1. FIG. 2. FIGS. 1 AXD 2. Stress diagrams The general form of load-deformation curve should be noted. Figure (1) represents a characteristic curve of ductile materials where the curve is drawn a straight line to the elastic limit averaging the plotted points. Figure (2) represents the curve for brittle materials. Select scales of coordinates so that the slope of the portion below the elastic limit is about 60. As in Fig. 1 when curve does not start at origin draw a parallel line through origin to the elastic limit. The title of the curve sheet should be placed in the lower right-hand corner and should contain such in- formation that a busy man unacquainted with the GENERAL INSTRUCTIONS I experiment, glancing at the curve sheet, would grasp the main facts without aid of the written report. The student will note carefully any characteristics of the curve that are peculiar and state reasons for their appearance and how they can be avoided if they seem to be errors. INSTRUCTIONS FOR WRITING REPORTS The clerical part of the report should be suitable for submission to a practising engineer, who would naturally judge of the qualifications of the writer by the neatness and system of the report. The sequence and the form in which the results are presented must be such as to enable a busy man to ascer- tain in a few moments just what was done and what was determined. A careful study should be given to economy of language in writing the report. SUGGESTED FORM OF REPORTS Title.- The title should indicate briefly what is covered by the report. Purpose. Under this heading the purpose, or pur- poses, of the tests should be concisely stated. - Materials Tested.- It is important that the materials tested should be concisely and definitely described. It is ordinarily sufficient to define the material as to its kind, size, shape and condition, although any other essential descriptive facts should be stated. Dimensioned sketches are frequently necessary to properly describe the test specimens. Reference should here be made to any sketches, descriptive of the material, appearing in an appendix or elsewhere in the report. Give page. Apparatus. Important special apparatus, only, should be listed and concisely and accurately described. 8 LABORATORY MANUAL OF TESTING MATERIALS Diagrammatic sketches are frequently necessary to properly describe apparatus as used. Reference should be here made to diagrams or sketches descriptive of apparatus appearing elsewhere in, the report. Method of Test. Only the essential details of the testing procedure will be concisely and accurately given. It is not usually necessary to include in this division the unessential details of manipulation and measurement which are more or less common to all experimental work of this nature. It is important, however, to use good judgment in the selection and statement of such details of procedure, as to afford a proper and clear interpretation and comprehension of the results obtained. Results of Tests. The summarized results of the tests should be given under this heading. The results are usually most conveniently and clearly shown in sum- mary tables. Care should be taken that summaries should be accurate and concordant with the facts shown elsewhere in the report. Averages should be accompanied by a statement as to how many and what data are included. Discussion and Conclusions. Explain the significance of the curves used to present graphically the results of the tests. (It should be here emphasized that curve sheets should be clear and as far as possible self-explana- tory.) Where there are standard specifications for the material and test, a comparison with these standards should be shown. The standards should be quoted and authority and reference given. The specifications of the American Society for Testing Materials and other national societies should be consulted. Comparisons with published data by other authorities, along similar lines, are generally necessary for the proper GENERAL INSTRUCTIONS 9 interpretation of the test results. Give references. Attention should be called to the factors affecting the accuracy, uniformity and validity of the results as shown. The significance and importance of the test and results should be discussed. The conclusions drawn should take all, of the above considerations into account, particularly those which are affected by the limitation of the testing apparatus used, the personal factor involved in ijie methods and special or unusual characteristics, or defects, in the test speci- mens visible either before or after the completion of the tests. CHAPTER III DEFINITIONS As supplementing the text-books in mechanics the fol- lowing definitions are recorded for reference : For formulas and symbols see Appendix. Stress is the internal, equal and opposite, action and reaction between two portions of a deformed body. Stress is a distributed force, and is expressed in force units. As in case of deformations, stresses are: (1) normal, S, either tensile (+) accompanying a lengthen- ing of a bar, or compressive ( ) accompanying a shortening of a bar; and (2) tangential or shearing, S v , when acting parallel to a section and accompanying achange of angle of the faces. Uniformly distributed normal stress accompanies a load that acts along a geometric axis of a bar. Unit stress (pounds per square inch) is the amount of stress per unit of area of surface. The word strain is often used to express both deforma- tion and stress. When used below it means deformation. Stress-strain diagrams (Fig. 3) are drawn from data obtained in tests of materials in which gradually increas- ing loads are applied from zero until rupture occurs. Unit deformations are shown as abscissae, and unit stresses as ordinates, tension (+) and compression ( ). Such diagrams display the most important mechanical properties of materials. Figure 3 shows sev- eral such diagrams. The tension deformations at small loads are shown in magnified scale to the right and the 10 DEFINITIONS 11 FIG. 3. 12 LABORATORY MANUAL OF TESTING MATERIALS relative values of S p for various materials to the left. The stresses are not actual but nominal, because the load is divided by the original, and not by the actual, deformed area. ELASTICITY Elasticity is the tendency of deformed bodies to resume their former shape. Elastic Limit is the limit of stress within which the deformation completely disappears after the removal of the stress. As measured in tests, and used in design this term refers to the proportional elastic limit, S p , which is the unit stress within which stresses and defor- mations are directly proportional. At the Commercial Elastic Limit or Yield Point, S v , some materials experience a sudden and large increase of deformation without in- crease of stress. S p is from 0.75 S y (hot-rolled steel) to 0.90 ^^(annealed steel). Location of S y depends upon speecffrf stress. KEY TO CURVES IN UPPER LEFT CORNER FIG. 3. Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. annealed Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. Curve No. 11 A Soft O. H. Steel, as rolled. B Soft O. H. Steel, oil tempered and annealed. C Soft O. H. Steel, oil tempered. A Axle Steel, as rolled. C Axle Steel, oil tempered A O. H. Steel, forged disc. B O. H. Steel, forged disc, oil tempered and C O. H. Steel, forged disc, oil tempered. B Heavy Steel Casting, annealed A Cast Copper, annealed. B Cast Copper. C Hard Rolled Copper. Iron. ;eel Casting, rim of small gear. Chrome Tungsten. Vanadium Steel. DEFINITIONS 13 Hooke's Law states that, within the elastic limit, the deformation produced is proportional to the stress. NOTE. Unless modified, the deduced formulas of me- chanics apply only within the elastic limit. Beyond this the formulas are modified by experimental coefficients, as for instance, modulus of rupture. Modulus of Elasticity (pounds per square inch) is the ratio of the increment of unit stress to increment of unit deformation within the elastic limit. The Modulus of Elasticity in Tension, or Young's Modulus, E, is graphically measured by the slope of OP (Fig. 3); the compression modulus by the slope of OP'. The inverse values of E for several materials express the relative unit deformations of these materials under the same unit stress. E is a measure of stiffness. Modulus of Elasticity in Shear, F, is the shearing unit stress divided by the angle of distortion exps^ed in radians. Theoretically, F = n/2E(n -f 1); and when n = 3, F = %E. (See Poisson's ratio.) Bulk Modulus of Elasticity, B, is the ratio of unit stress, applied to all side faces of a cube, to the unit change of volume. Theoretically, B = ^ En/(n 2); and when n = 3, B - E. Lateral Deformation, e' ', accompanies longitudinal de- formation, e. Poisson's Ratio, m, is the ratio of e' to e. The inverse value of m is denoted by n, that is, n = l/m. Values of m given by Unwin are: Flint Glass, 0.244; Brass, 0.333; Copper, 0.333; Cast Iron, 0.270; Wrought Iron, 0.278; Steel, 0.303; Concrete, according to Talbot, 0.10. Change of volume, under long^J^nal deformation. /, d, b, = length, width and thicflHs; m = Poisson's ratio; s = unit deformation. Deformed volume - sms)b(l - ms)d=(l+s-2ms)lbd. 14 LABORATORY MANUAL OF TESTING MATERIALS Fractional change of volume = (1 2m) s. When m is less than J^ the volume is increased in tension and decreased in compression. For steel, (m = }), change of volume is about J^ooo part at the elastic limit. A bar under stress does not at once assume the length due to its modulus of elasticity E. Deformation pro- ceeds for days and weeks. These phenomena of residual elasticity or elastic afterworking do not seem to be of prac- tical importance. RESILIENCE Resilience, K, (inch-pound) is the potential elastic energy stored up in a deformed body. For instance, a falling weight compresses a spring; the stored energy, or resilience, of the material is a source of work and will produce return motion in the weight. The amount of resilience i equal to the work required to deform the volume of material from zero stress to stress S. For longitudinal deformation ^Fig. 3), P load, e = deformation, S unit stress, E = modulus of elasticity, I = length, A = area cross section, V = volume. Resilience = work of deformation = average force X deformation = %Pe = ^AS Sl/E, or K = vy 2 &/E. The resilience for any other kind of stress such as shear- ing, bending, torsion, is the volume times a constant C times one-half the square of the stress divided by the appropriate modulus of elasticity. Resilience of solids of varying section cannot be ex- pressed per unit ojayolume. Modulus of rWMfence, K p (inch-pounds per cubic inch), or unit resilience, is the elastic energy stored up in a unit volume at the elastic limit. For longitudinal DEFINITIONS 15 deformation K p is graphically measured by the area OPP". (Fig. 3.) K p = H S*/E. RESILIENCE PER UNIT OF VOLUME K S = longitudinal stress, Sv = shearing stress, E = tension modulus of elasticity, F = shearing modulus of elastfcity 1. Tension or compression y t s-/E SPRINGS. 2 Shear }$Sv*/F Carriage 1 ^-i O O OC O 00 O O5 O Gi GS C^ fit III es^sessssss&s sa CuCCCGflCCCMC csaJco3c8c8o3cSc8ci3a!a3 13 13 "3 la Is 13 Is "c 13 S13 . -S ^"3 S 2 S U'U MWW WfflW W 333 ^ ^ 222 2 jooooo; lllll 111 :* : :S : 88 rf ^ -CO ^-11 ill ill ;IM22fiiiIl!* ;/ %?%!%%!%%%^^ Base of Machine Ifia. 6. Spherical bearing plate and method of supporting test piece in com- pression. 24 LABORATORY MANUAL OF TESTING MATERIALS is applied as nearly as possible in the axis of the test piece. This implies that the specimen should be ac- curately centered in the testing machine. The common method of holding the test bar is by serrated wedges with flat face, which is suitable for ductile materials. For brittle materials, or short specimens, it is customary to use a spherical, or universal, joint between the speci- men and the testing machine. These if correctly designed do away with bending and buckling in the specimen. Incorrect Correct FIG. 7.' Method of gripping test specimen in tension. Fig. 5 and 6 illustrate the adaptation of the universal joint to tension and compression tests. 1 Fig. 5 shows a convenient apparatus for gripping the standard short screw-end test piece and Fig. 6 shows the common method of supporting concrete or other like material in compression. A bedding of Plaster of Paris or blotting paper is used between the specimen and the surfaces of the machine, to give an even application of the load. Fig. 7 indicates a correct and an incorrect way to grip a specimen in tension. The test piece should extend 1 NOTE : For compression tests of concrete the spherical bearing plate should be placed on top of the specimen. TESTING AND TESTING MACHINES 25 through the grips and these should have their full bearing over their entire length in the heads of the testing machine. FIG. 8. An apparatus for testing small beams in flexure. FIG. 9. A method of testing large beams in flexure. Flexure tests require freedom of specimen to bend and rollers should be placed between supports and 26 LABORATORY MANUAL OF TESTING MATERIALS specimen. In case an auxiliary straining beam in used, rollers are especially necessary to prevent compounding of straining beam and specimen through the horizontal shear at the loading points. Figs. 8 and 9 show apparatus as used by the Forest Service in the tests of timber, In Fig. 8, the supporting beam is conveniently laid across the weighing table of a small capacity testing machine. The rollers and plates FIG. 10. A shearing apparatus for wood. between supports and specimen prevent local failure and binding at the supports. In testing large beams, Fig. 9, it is customary to apply the loads at the third points by means of an auxiliary beam with rollers and plates. The knife edge supports are, in this case, so constructed that they rock freely as the beam bends downward. Shear Tests. Shearing shackles and tools should pro- duce pure shear without bending. Fig. 10 shows a simple and reliable shearing tool for tests of timber. It is supported directly on the weighing table of the TESTING AND TESTING MACHINEvS 27 testing machine and the plunger comes in direct contact with the under side of the movable head. ; (b) METHOD OF APPLYING THE LOAD Loads are applied mainly by screw power (Olsen or Riehle); or (2) hydraulic power (Emery or Amsler). Fio. 11. Diagrammatic view of a Riehld testing machine. (Modified frojn Marten's Handbook of Testing Materials.) Screw Machines.- American machines are commonly of screw power. Old screw machines should be ex- amined to see if the wear of the threads produces an oscillatory motion of the testing heads. Fig. 11 represents by diagram a Riehle testing ma- chine. This is a two-screw machine. By rotation of 28 LABORATORY MANUAL OF TESTING MATERIALS the screws about their axes, the pulling head is moved up and down. Suitable gearing gives a variety of speeds in either direction. Fig. 12 shows an Olsen machine. This is generally a four-screw machine, sometimes three. In this type, the pulling head is made to move up or clown by the rotation of large geared nuts stationary in the base of FIG. 12. Diagrammatic view of an Olsen machine. (Modified from Marten's Handbook of Testing Materials.) the machine. Through these nuts pass the main screws to which is attached the pulling head. The screws do not turn on their axes. Hydraulic Machines Hydraulic machines, now becoming more popular, have many advantages in maintenance, steady loading, and in design of central TESTING AND TESTING MACHINES 29 power plant for laboratory! These sometimes involve friction of packing in cylinder, which is not important in large machines, and which is obviated in small ma- chines (Amsler) by use of a floating piston and a viscous fluid like castor oil. Proper provision should be made to hold a steady load. Fig. 13 shows the Amsler machine of small capacity. FIG. 13. Diagram of Amsler testing machine. (From Wawrziniok.) As shown, the machine is equipped with a hand pump and a mercury column load indicating device. To the right is shown the more common pendulum method of indicating load. Fig. 14 is a diagrammatic sketch of a vertical Emery testing machine. The hydraulic cylinder A is fixed to 30 LABORATORY MANUAL OF TESTING MATERIALS the frame D of the machine by the main rods SS. The plunger B is attached to the gripping apparatus. The weighing system is independent of the power system. Impact Machines.- Impact testing machines are (1) with vertical guides, or (2) of pendulum type. Pro- vision should be for meas- uring energy remaining in hammer after rupture of specimen. For this pur- pose, the hammer may fall on a spring (Fremont ma- chine), or, a pencil attached to the hammer may write a velocity d isplacement curve on a revolving drum (Turner machine). Method of release and hoist and mechanical details differ. Machines should be ex- amined for: (a) fit of ham- mer in guides; friction; proportion of height of hammer to clear width be- tween guides ; proportion of weight of hammer to foun- dation; perfection of release; shape of striking edge. Hammer should deform specimen as a whole. Loss of energy at surface of impact and in foundation due to inertia of specimen should be small. Fig. 15 illustrates the Turner vertical type of impact machine as used by the Forest Service in impact bending of small specimens. The pencil on the falling hammer makes a record on the revolving drum. The drum record, Fig. 16, represents a test of a spcci- FIG. 14. Diagram of a vertical Emery testing machine. (From Unwin.) TESTINU AND TESTING MACHINES 31 men broken in seven blows of increasing heights of hammer drop. The record gives the rebound heights and the deflection and set of the beam for each blow. The drum record, Fig. 17, represents a test of a speci- men broken in a single blow of the hammer. The drum velocity is given by the tuning fork record T-T. The FIG. 15. The Turner impact machine. datum line 0-0 is the position of the hammer at instant of striking the specimen. The velocity of the hammer at that point may be obtained from the slope of the curve at the point of crossing. Distance up from the datum line represents free fall of the hammer. Distance down from the datum line to point of rupture C repre- sents restrained fall of the hammer and deformation 32 LABORATORY MANUAL OF TESTING MATERIALS of the specimen. Below the point of rupture, the ham- mer has free fall and the residual energy may be com- puted from the velocity as given by the curve slope. Endurance Machines. The ability of metals to withstand a rapid reversion of stress is an important property. Heat-treated automobile or other machine Fro. 1C. Drum record, Turner impact machine. Specimen broken by seven blows of hammer. parts are tested for this quality by means of the endur- ance testing machine as shown in Fig. 18. The test piece A, accurately machined to size and shape, is rigidly gripped in the pulley B. The pulley is seated and free to turn in ball bearings in the frame F. By means of the yokes C-C and their weight supporting TESTING AND TESTING MACHINES 33 FIG. 17. Drum record, Turner impact machine. Specimen broken in single blow. FIG. 18. The White-Souther endurance testing machine. 34 LABORATORY MANUAL OP TESTING MATERIALS standards, a load may be applied to each end of the test specimen. The pulley is made to rotate by belt connection to a motor. The speed of rotation is usually 1300 r.p.m. The stress in the top and bottom is alter- nately tension and compression in rapid succession. Complete failure occurs at the edge of the fillets after a varying number of revolutions and at a stress below the elastic limit of the metal. Special Test. Hardness is not well defined, nor uniformly measured. Unwin defines it as resistance to permanent or plastic deformation. In this definition it is distinguished from resistance to abrasion which is a compound of other qualities. The best test for hardness is the Brinell Ball test. A hardened spherical ball (10 mm. diam.), is forced into a flat surface under a static pressure of 3000 kg. and 500 kg. for soft metals. The time of pressure should be at least 30 seconds. The specimen is 10 mm. thick and 35 mm. wide. Hardness = pressure / curved area of de- pression. A fixed ratio exists between hardness and ten- acity of steels. Martens uses the depth of the impression. With balls 5 mm. in diameter the ratio of load to depth is constant within a depth range of 0.05 mm. The hardness number is the load necessary to indent material to 0.05 mm. For instance, Brinell hardness number is as follows. Acid Bessemer steel, carbon 0.10, hardness number: rolled, 100; annealed, 96. Basic Bessemer steel, carbon 0.12, hardness number: rolled, 76; annealed, 81. A more recently perfected method for determinations of hardness is by means of the Scleroscope. In this instrument the height of rebound of a small diamond pointed tup is taken as a measure of the hardness of the surface upon which it is caused to fall. The height of TESTING AND TESTING MACHINES 35 drop is a fixed distance. The area of contact of the diamond point is so small that the metal upon which it strikes is stressed beyond the elastic limit. The tensile strength of steel in pounds per square inch is obtained from the following equations. TABLE 1. EQUATIONS CONNECTING MAXIMUM STRENGTH AND BRINELL NUMBERS Kind of steel Equations Carbon steel M = 73 B - 28 Nickel steel Chrome-vanadium steel M M = = 71 71 B B - 32 - 29 Low-chrome-nickel steel High-chrome-nickel steel M M = = 08 71 B B - 22 - 33 All steels grouped together M = 70 B - 26 TABLE 11. EQUATIONS CONNECTING MAXIMUM STRENGTH AND SCLEROSCOPE NUMBERS Kind of steel Equations Carbon steel Nickel steel M M = 4 = 3 4 ^ S - S - 28 fi Chrome-vanadium steel Low-chrome-nickel steel . M M = 4 = 3 2 7 S - ,s - 21 1 High-chrome-nickel steel M = 3 7 ,sr - 3 All steels grouped together M = 4 ,s - 15 M is maximum strength in 1000 pound per square inch units. Reference. Proceedings of the American Society for Testing Materials, 1915. (c) WEIGHING MECHANISMS 1. The most common type is the lever system. These are illustrated in Figs. 11 and 12, diagrammatic representations of the Olsen and Riehle testing machines. LABORATORY MANUAL OF TESTING MATERIALS All lever bearings and connections are hardened steel knife edges and plates. Load is indicated by the posi- tion of the poise p on the weighing beam. 2. A gage or manometric column indicates the pres- sure in the cylinder of hydraulic machines. Sometimes a pendulum lever is employed to serve the same purpose. These types are illus- trated in Fig. 13 in the diagram of the Amsler machine. 3. The pressure from the weighing table is transmitted to a hy- draulic pad H, in Fig. 14, and thence to a mano- metric column or as in the Emery machine, to a separate lever system the fulchra of which are elastic plates. 4. A less common type is that in which the de- formations of a portion of the frame of the ma- chine are measured. FIG. 19. The load is indicated by a measuring apparatus or by the change in volume of a hydraulic chamber which in turn is recorded on a fluid column. A diagram- matic view of this is shown in Fig. 19. The view shows one of the main rods B-B of the machine. This is fixed to the frame A of the machine. As the load comes on B, the deformation of B changes the volume of the chamber C-C, and is registered by a fluid column or TESTING AND TESTING MACHINES 37 other convenient means. The load value of the column is determined by calibration. EXTENSOMETERS AND OTHER DEFORMATION INSTRUMENTS For the determinations of yield point of tension bars and deflection of beams, instruments reading to 0.01 in. are sufficient. But for the determination of elastic FIG. 20. Yale-Richl6 extensometer. FIG. 21. Johnson roller cxtensomcler. limit and modulus of elasticity and for many other purposes, deformation instruments reading to 0.0001 in. are required* Extensometers may be classified: 1. Micrometer screw, see Fig. 20. These are very reliable for experienced laboratory use but are seldom 38 LABORATORY MANUAL OF TESTING MATERIALS v\ FIG. 22. Marten's mirror extensometer. FIG. 23. The Berry strain page. TESTING AND TESTING MACHINES 39 used for practical work. The contact of the micrometer points is best determined by means of an electric circuit and a telephone receiver in series. 2. Roller dial (Johnson type), See Fig. 21. A simple Enlarged HoU for Berry St" Gage, in Steel Bar FIG. 23a. ert iu Concrete t'er Compression FIG. 235. A type for laboratory use but unreliable on account of slippage at the roller. There is also error introduced by the wear of the roller. The readings are given direct on the dials. 3. Roller mirror, see Fig. 22. This is very delicate and reliable, but unsuited to student or routine work of the laboratory. The in- strument must be used where there is little vibration or jar. 4. Lever type, examples of these are the Olsen Ewing and Berry. The last of these is particularly well adapted to a large variety of practical work both in the lab- oratory and in the field. In Fig. 23 is shown this instrument as made with contact points for use in reinforced concrete work and with adjustable gage length. The contact points are placed in small counter-bored holes in the test piece. In some cases, the instrument may be fixed and held in testing position throughout the loading, FIG. 23c. Extensometer with Ames dials. 40 LABORATORY MANUAL OP TESTING MATERIALS but generally it is removed after each reading is taken. In using the instrument, proper correction must be made for changes in temperature. The instrument reads directly to 0.0002 in. and closer by estimation of parts of a graduated division. The following precautions are taken in using the Berry strain gauge: 1. The instrument is seated in the hole 5 times for an observed length. 2. A preliminary series is taken in new holes. FIG. 24. Diagrammatic representation of an Olsen deflection instrument. 3. After five sets of readings, the instrument is read on a standard bar to check up changes in the instrument. 4. To reduce observations for temperature changes, readings are made on a specimen which is without load, and which is exposed in the same manner as the specimen under test. 5. A single observer should make any set of readings and always in the same order. 6. The instrument should be applied at right angles to the bar and with uniform pressure. Compressometers. The simplest type of compres- someter is shown by diagram in Fig. 24; this is a good practical instrument for rough work. It reads directly to 0.01 in. and by estimation to 0.001 in. TESTING AND TESTING MACHINES 41 Fig. 25 illustrates an instrument designed for closer more accurate determinations. This compressometer needs very careful handling for the best results. Better service may be accomplished by replacing the electric bell by a telephone receiver, to give the micrometer contact. The instrument reads directly to 0.0001 in. FIG. 25. The Olsen compressometer. A compressometer for short columns of timber which has been found very useful for student work by the authors, is shown in Fig. 26. Two yokes bearing Ames dials are attached to the specimen by four contact screws each. As the piece is deformed, the readings are given on both sides by the Ames dials. These read direct to 0.001 in. and by estimation to 0.0001. 42 LABORATORY MANUAL OF TESTING MATERIALS FIG. 26. Author's compression instrument for short wood columns. FIG. 27. Autographic apparatus. (From Wawrziniok.) TESTING AND TESTING MACHINES 43 Autographic Recording Apparatus. A drum, Fig 27, is fixed on the frame of the testing machine and put in gear with the specimen so that the rotation of the drum is proportional to the stretch of the specimen. A pencil in gear with the poise moves parallel to the axis of the drum. As the test proceeds, the diagram on the drum has abscissae of deformation and ordinates of load. In some types, the poise is replaced by a spring at the end of the scale beam. As the load is applied the scale beam rises and the spring measures the load. The rise of the beam actuates the pencil on the drum. This type yields delicate load measurements. A home-made simple autographic device is made of a steam-engine indicator on this plan. Autographic recorders are not suitable for the delicate measurements for elastic constants and are of limited use. CHAPTER VI LIST OF EXPERIMENTS PAGE ARTICLE 1. TESTING MACHINES , 48 A-l. Study of Testing Machines. A-2. Calibration of Testing Machines. A-3. Calibration of Extensometers or other Measuring Device. ARTICLE 2. IRON AND STEEL. 52 B-l. Commercial Tension Test of Wrought Iron and Steel. B-2. Commercial Tension of Cast Iron or Cast Steel. B-3. Autographic Tension Tests of Metals. B-4. Tension Test of Iron or Steel with Extensometers. B-5. Torsion Test of Iron or Steel. B-6. Tension Test of a Wire Cable. B-7. Compression Test of a Helical Spring. B-8. Effect of Overstrain on Strength and Elasticity of Steel and Iron. B-9. Flexure test of Cast Iron or Steel. B-10. Flexure Test of Brake Beam. B-ll. Vibratory Tests of Stay Bolts. ARTICLE 3. TESTS OF WOOD G6 C-l. Study and Identification of Woods. -C-2. Compression of Wood Parallel to Grain. C-3. Compression of Wood Perpendicular to Grain. C-4. Compression of Wood Columns. C-5. Flexure of Small Wood Beams. C-6. Flexure of Large Wood Beams. C-7. Impact Tests of Wood. C-8. Abrasion Tests of Wood. C-9. Shearing Test of Wood. 44 LIST OF EXPERIMENTS 45 PAGE ARTICLE 4. TESTS OF CEMENTS 76 D-l. Tests of Specific Gravity of Cements. D-2. Fineness of Grinding. D-3. Normal Consistency. D-4. Time of Setting. D-5. Soundness. D-6. Strength of Cement and Cement Mortars in Tension. D-7. Strength of Cement and Cement Mortars in Compression. ARTICLE 5. STUDY OF AGGREGATES 93 E-l. Sampling. E-2. Cleanness of Sand. E-3. Weight of Aggregates. E-4. Specific Gravity of Aggregate. E-5. Voids in Aggregate. E-6. Moisture in Sand. E-7. Study of Sieves. E-8. Sieve Analysis of Aggregates. E-9. Hand Mixing of Concrete. E-10. Mixing Concrete by Machine. E-ll. Water Required for Mixing. E-12. Theory of Proportioning. E-13. Proportioning Mortars and Concretes. E-14. Proportioning by Sieve Analysis. E-15. Strength in Relation to Density. E-l 6. Surface Area of Aggregates. E-l 7. Fineness Modulus. ARTICLE 7. TESTS OF CONCRETES AND OTHER BRITTLE MATERIALS 132 F-l. Strength of Mortars Made up of a Given Sand. F-2. Compressive Strength of Concrete. F-3. Test of Brittle Materials Determining Strength at First Crack and Ultimate. F-4. Test of Brittle Materials Determining Strength and Elasticity. F-5. Flexure Test of Reinforced Concrete Beams. 46 LABORATORY MANUAL OF TESTING MATERIALS PAGE F-6. Bond Strength of Steel in Concrete. F-7. Test of Reinforcing Fabric. F-8. Cross Bending and Compression Tests of Build- ing Brick. ARTICLE 8. TESTS OF ROAD MATERIALS ; 140 G-l. Rattler Tests of Paving Bricks. G-2. Absorption Test of Paving Brick. G-3. Abrasion Test of Stone. G-4. Cementation Test of Stone or Gravel. G-5. Hardness of Stone as Determined in Dorry Test. G-6. Impact Test of Stone, Standard Test for Toughess. EXPERIMENTS FOR ADVANCED WORK The following list of experiments represents subjects for special tests to be carried out by the student. Some of these may also be made the subject of thesis investigation. Iron and Steel. Tension test of wire. Shearing tests of steel or iron. Tests of chains, hooks and rings. Tests of effect of shop methods on strength of steel and iron. Flexure test of I-beams. Tests of car bolsters, side frames, etc. Tests of flat springs in bending. Tests of built-up columns. Tests of metals in rapid reversion of stresses using White-Souther machine. Tests of various forms of joints. Tests of hardness of metals using Sclcroscope. Tests of alloy steels. Tests of steel plates. Wood. Tension of various wood splices and joints. Indentation tests of wood. Wood in shear. Torsion of wood. Spike pulling tests of wood. Plate and washer bearing in wood. Tests of wood paving blocks. Tests of treated timbers. Cement. Determination of weight per cubic foot of cement. Effect of fineness of grinding on properties of LIST OF EXPERIMENTS 47 cement. Effect of varying amounts of gaging water. Effect of waterproofing methods upon strength and hardness. Tests for adulterants in cements. Effect of oils on properties of cements and cement mortars. Concrete. Strength of concrete with clay admixtures. Tests of concrete columns, plain and reinforced. Con- crete in shear. Bond of steel in concrete. Tests of concrete T-beams. Concrete arches. Tests of porosity and permeability of concrete. Electrolysis of steel in concrete. Machine vs. hand mixed concrete. Brittle Materials. Compression tests, fire tests, freezing tests. Absorption tests^ Test of patent roofing, flooring or other building material. CHAPTER VII INSTRUCTIONS FOR PERFORMING EXPERIMENTS Article 1 TESTING MACHINES Experiment A-l STUDY OF TESTING MACHINES In this experiment, the student becomes acquainted with various types of testing machines and gains skill in their operation. References. Standard Methods for Testing, E 1-18, A. S. T. M. Standards 1918. Johnson's Materials of Construction-rewritten by Withey and Aston. Page 49. Materials. No material to be tested. Special Apparatus.- Various types of testing ma- chines as assigned. For each machine assigned, tabu- late: capacity of machine; name of builder; vertical or horizontal; number of screws; drive, i.e., belt, direct connected motor, hydraulic? Procedure. (a) Study operation of machine. Each student should become familiar with operation of ma- chines as he is responsible for breakage due to ignorance and carelessness. General Rules for Operators. 1. Do not start machine into a continued motion without first ascertain- ing the direction and speed with which it will move. Extra precaution in this respect must be used if the 48 INSTRUCTIONS FOR PERFORMING EXPERIMENTS 49 movable head is near top or bottom of its range of movement. 2. Do not start the machine with too sudden a motion as there is danger of stripping a gear, throwing a belt, or injury to electrical equipment. 3. Do not reverse direction of motion or change speed without first stopping the machine. 4. Stop and start the motion with the lever provided on the machine, not with the counter-shaft shifter, nor with the electric switch. 5. When leaving the machine always see that the motion is stopped and counter-shaft is shifted to loose pulley. (b) Tabulate number and direction and value of the various speeds with which moving head can be moved. (c) Study and sketch the weighing table with lever system and weighing device. Measure and record all lever arm lengths. Sketch the various positions of control and speed levers. Discussion of Results. In the report, answer the following questions: 1. Why is there need for centering the specimen in the testing machine? (a) With regard to effect on test piece. (6) With regard to effect on machine. 2. Why can not the friction drive and main .clutch drive be used simultaneously? (This refers to Olsen friction type of machines only.) 3. The slow speeds in the Olsen type of machine are sometimes obtained by a friction drive. In the Riehle type they arc obtained by a system of gearing. (a) Give advantages and disadvantages of the fric- tion drive for slow speeds. 50 LABORATORY MANUAL OF TESTING MATERIALS (6) Give advantages and disadvantages of the geared drive for slow speeds. 4. How is shock arising from rupture of specimen absorbed in the machine? 5. Where are the main wearing surfaces in the machine ? 6. What is the purpose of (a) the counter-poise, (6) the counter-weight? 7. Upon what does the accuracy of a testing machine depend? 8. Upon what does the sensitiveness of a testing machine depend? Experiment A-2 CALIBRATION OF TESTING MACHINES References. Standard Methods for Testing, E 1-18. A. S. T. M. Standards, 1918. Johnson's Materials of Construction Rewritten by Withey and Aston, page 50. Testing machines should be calibrated at least once a year. This experiment will show the common methods of- calibration. I. Accuracy of Machine Over a Part of Its Range of Load. The testing machine may be tested for accu- racy by loading the weighing table with standard weights. The weights should be placed uniformly on the table and beam readings taken for the various weights applied. This is the easiest and simplest manner of calibration of a testing machine but on account of the limited size of weighing table only a small part of the total capacity of the machine can be applied. However, the propor- tionality of the levers and weighing beam can be estab- lished and if the machine is correctly designed, the relation will hold constant for all loads. Auxiliary levers are also commonly used for this purpose. INSTRUCTIONS FOR PERFORMING EXPERIMENTS' 51 II. Accuracy of a Machine Over a Part or All of Its Range of Load. If the accuracy of the machine over its whole range is desired, a known load may be applied by a standard calibration bar whose modulus of elasticity has been accurately determined. The bar should be of sufficient strength so that the load desired should not stress it to or near the elastic limit. The bar should be carefully centered in the machine and gripped with the spherical bearing nut at the end. The length of the bar measured by the extensometer shall be sufficient that the smallest division on extensometer shall correspond to a difference in loading of 0.2 per cent, of the capacity of the machine or less. The extensometer shall read deformations to 0.0001 in. or less. The percentage of error in the testing machine may be determined by comparison of ihe determined modulus of elasticity (see Experiment B-4) with the previously known correct modulus of the standard bar. III. Tests of Sensitiveness of the Machine at Differ- ent Loads, Place in the machine a tension bar or a com- pression block of such size that the maximum load will not stress it to the elastic limit. Load the specimen to Mo> MJ an d ?lo the capacity of the machine. At each load, balance the weighing beam and place standard weights upon the weighing table. A weight ^50 of the load applied on the machine should produce a readable movement of the beam. Experiment A-3 CALIBRATION OF EXTENSOMETERS OR OTHER MEASURING DEVICE Reference. Johnson's Materials of Construction Withey & Aston, page 100. Refer to Experiment B-4, 52 LABORATORY MANUAL OF TESTING! MATERIALS Case I. Use a testing machine known to be accurate and a standard calibration bar whose modulus of elas- ticity is known. The extensometer to be calibrated is placed upon the bar in the usual manner and the modulus of elasticity determined in the usual way. The variation of the computed modulus from the correct modulus gives the error in the extensometer used. Case II. Using any bar and any machine determine the modulus with the extensometer to be calibrated and also with an extensometer which has previously been accurately calibrated. The variation in the modulus gives the error in the extensometer being calibrated. A convenient method is to use a bar of sufficient length to provide for both a standard extensometer and that to be tested. For greater refinement the extensometers may be interchanged in a second test. Case III. Direct comparison with any form of accu- rate measuring device may be made. Care must be taken to eliminate the effect of temperature changes, lost motion or other variables. Article 2 IRON AND STEEL Experiment B-l TENSION TEST OF IRON AND STEEL The experiment is intended to represent the condi- tions obtaining in an ordinary commercial test with the exception that the speed of descent of the pulling head of the testing machine is much slower than customary in commercial laboratories. The experiment will deter- mine the strength and ductility of the material. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 53 References. Materials of Construction Upton, Ar- ticles 48-75. Johnson's Materials of Construction Withey & Aston, page 104-110. Standard Methods for Testing, E 1-18; and Standard Specifications for Materials, of Amer. Soc. for Testing Materials, 1918. Material. Bars of iron or steel as furnished. Special Apparatus. Micrometer calipers, scale, di- viders. Procedure. 1. Give specimen a number and record this. 2. With vernier or micrometer calipers determine the average dimensions of the cross section. Use average of three readings. 3. Lay off gage length of 8 in., each inch being marked by a light center punch mark. 4. Carefully balance the testing machine at zero of weighing beam after first loosening recoil nuts on weigh- ing table. Then insert the test-piece in the wedges, being careful that the test-piece is centrally disposed in the axis of the machine, and that the specimen is gripped to within 1 in. of the end gage marks. Tighten specimen in grips by applying a load of about 500 Ib. Chalk a small area of the bar near the upper gage mark. Before proceeding with the test allow the instructor to inspect the work. One student should insert one leg of a pair of dividers in the lower gage mark and scribe a line with the upper leg on the area previously chalked. Apply the load at a medium speed and operate the poise so as to keep the scale beam floating. The requirements of the Amer. Soc. for Testing Mate- rials as to speed are as follows: 54 LABORATORY MANUAL OF TESTING MATERIALS Specified minimum tensile strength of material, Ib. per sq. in. Gage length, in. Maximum crosshead speed, in. per minute, in determining Yield point Tensile strength 80,000 or under < Over 80 000 { 2 8 2 8 0.50 2.00 0.25 0.50 2.0 6.0 1.0 2.0 The operator with the dividers should continue to scribe the line and notify the operator at the poise when the width of the scribed line increases perceptibly due to sudden increase in the rate of stretching of the test bar under the load. At this time the beam may be expected to drop suddenly and remain down for an interval; also rough mill scale will fall from the specimen. This in- crease in elongation without a corresponding increase in load is the "yield point." It is a point beyond the true elastic limit as obtained in experiment B-4. During a further stretching of the bar the beam will again rise and should be kept floating up to the maximum load. At this maximum load the bar begins to neck in, the material becoming plastic at the point of the forma- tion of the neck. Leave poise at the maximum load, do not attempt to get actual breaking load. The stretching of the specimen should be continued until fracture occurs. Record in data sheet the load at yield point and the maximum load. Measurements after Tests. Lay the broken ends of the bar together and determine the increase in elonga- tion of the gage length. Measure the dimensions of the fractured area. Determine the rate of descent of the pulling head of the machine. Describe the appearance . INSTRUCTIONS FOR PERFORMING EXPERIMENTS 55 of the fracture (see page 18) and determine the distance from the extreme gage point. Calculations. Calculate the ultimate tensile strength. Calculate the stress at yield point. Calculate the per cent, of elongation in gage length and per cent, of contraction of area at the fracture. In case the fracture is outside the middle third of the gage-length, the per cent, of elongation is to be measured and computed although a re test may be allowed in certain cases. This should be noted in the report. REPORT. See instructions for writing reports, page 7. Experiment B-2 COMMERCIAL TENSION TESTS OF CAST IRON OR STEEL CASTINGS References. Specifications of Amer. Soc. for Testing Materials. Standards 1918. Serial A 27-16 and A48-18. The materials in this test are generally as follows: Cast Iron. Specimen in the rough, no machining; standard arbitration bar machined to standard size. Steel Casting. Standard machined test-piece using 2-in. gage length. PROCEDURE. The method of test of cast iron is same as for Experiment B-l except that maximum load only is obtained. The method of test of steel castings is the same as for Experiment B-l except that a gage length of 2 in. is used. Computations. Make all computations as in regular test B-l, for steel casting specimens. For cast-iron speci- mens compute tensile strength. DISCUSSION OF RESULTS. Compare results with speci- fications and show in tabular form. 56 LABORATORY MANUAL OP TESTING MATERIALS Experiment B-3 AUTOGRAPHIC TENSION TESTS OF IRON OR STEEL This experiment may be performed by the instructor in front of the class to exhibit method used in commercial test B-l, and also by use of autographic diagram to show the general behavior of iron and steel when tested to rupture in tension. Materials to be Tested. The specimen should be a round bar of steel or iron. Apparatus. Besides the regular tension apparatus there should be the collars by which autographic appara- tus is attached to specimen. Procedure. All dimensions and descriptions of speci- mens should be noted as in the regular tension test. After attaching the collars to the ends of the gage length, the specimen should be placed in the machine and a small initial load applied to hold it. Arrange the auto- graphic apparatus so that the pencil is at the origin of diagram at zero load and zero stretch. Then apply the load continuously in a medium speed keeping the poise beam balanced. This may be done by the operator or by the mechanism in automatically balanced machines. Observe and record the load at yield point as given by the diagram, by drop, of the beam and scaling of the specimen. Observe the maximum load as given by the beam and diagram. Ascertain the elongation as given by the diagram and by actual measurement of specimen. Compute all results as obtained in regular commercial tension test. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 57 Experiment B-4 TENSION TEST WITH EXTENSOMETER In this experiment the strength and elastic properties of iron and steel in tension are determined. References. Standard Methods of Testing in 1918 Standards of Amer. Soc. of Testing Materials. Materials of Construction Upton articles 39-48. Johnson's Materials of Construction Withey and Aston, page 111. Material. Wrought iron or steel. Special Apparatus. Extensometer reading to at least 0.0002 inches. Note. The extensometers are delicate instruments and must be handled carefully. Any roughness of usage or lack of delicacy in manipulation will result in unsatis- factory diagrams. Be sure that the test bar is straight. PROCEDURE. Carefully measure and prepare each specimen as for regular tension test. See B-l. Tighten specimen in grips by applying an initial load equivalent to a stress of 2000 Ib. per sq. in. (the machine having been previously balanced). Apply and adjust the extensometer, noting the length between the contact points, and (after having had the apparatus inspected by the instructor) proceed with the test. Apply load in increments equivalent to a stress of 4000 Ib. per sq. in. for steel and 2000 Ib. per sq. in. for "iron and measure the total elongation at each load increment. When a stress of 30,000 and 20,000 Ib. per sq. in. for steel and iron respectively has been reached, apply loads in increments of one-half the former amount until, by the behavior of the beam, it is seen that the yield point is reached. After reaching a sudden and large increase in elonga- tion, remove the extensometer and apply load continu- 58 LABORATORY MANUAL OF TESTIXO MATERIALS ously until specimen is ruptured, keeping beam balanced. Record maximum load. An actual stress instead of the commonly used nomi- nal tensile stress may, if desired, be obtained by taking readings of the new specimen diameters at each incre- ment of load. This may be continued through to the breaking point and readings of total stretch made by dividers. Construct a diagram with stress in pounds per square inch as ordinates and strain in inches per inch as abscissae. Draw a straight line averaging the points up to the more rapid increase in elongation (the elastic limit), and, tangent to the straight line draw a smooth curve averaging the remaining points. Ordinarily, the straight line of plotted points will not pass through the origin. Draw through the origin a line parallel to the straight line of plotted points. This line represents the true relation between stress and strain. Mark the elastic limit where the strain ceases to be proportional to stress. Calculations. Calculate stress at elastic limit, ulti- mate tensile strength, per cent, elongation and con- traction, modulus of elasticity, and modulus of elastic resilience. The modulus of elasticity is the stress in pounds per square inch divided by the elongation in inches per inch at any point on the straight line through the origin. It is most convenient to- select an abscissa of elongation of one part in 1000, and multiply the corresponding stress by 1000 to obtain the modulus of elasticity. The modulus of elastic resilience is the amount of work done on each cubic inch of the specimen in deforming it to the elastic limit. It may be taken as the equivalent in inch-pounds of the area under the straight line up to elastic limit; or it may be calculated by formula. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 59 REPORT, The report should follow the standard form. It should be noted that this test is not a commercial test. Experiment B-5 EXPERIMENT IN TORSION The object of this experiment is to study the behavior of materials under torsion, and to obtain such data as will enable the shearing strength of the material and its modulus of elasticity in shear to be computed. References. Materials of Construction Mills. Articles 490. Materials of Construction Upton. Articles 76-110. Johnson's Materials of Construction Wit hey and Aston. Articles 140-142. Bulletin No. 115, Engineering Experiment Station, Univ. of Illinois. Material. The material may be steel, iron, wood, or other material. Special Apparatus. Torsion Deformation instrument. Procedure.- Carefully measure the dimensions of the cross-section and lay off gage length. Then adjust the specimen in the heads of the machine, being careful that the specimen is fixed in the axis of rotation of the machine. Then apply the deformation instrument to the specimen and adjust the clamps of the latter so that the center of the circle of the graduated arc will be in the axis of the machine. Measure the distance from the axis of the specimen out to the graduated arc. Apply a small initial moment of about 100 in. Ib. and set to zero or record an initial reading of the graduated arc, and also the permanent scale on the twisting head of the machine. Measure the distance betweenVgrips. Experiment. Apply the loads by Increment of 200 in. Ib. Read on the graduated arc the movement of the 60 LABORATORY MANUAL OF TESTING MATERIALS pointer in inches for each increment. When tjie increase in the angle of torsion is found to be rapid, the elastic limit has been reached. The graduated arc and index should then be removed. If only the elastic properties of materials are to be determined the specimen may be removed. Ordinarily the tests are to be continued until the specimen is rup- tured. Read load every 180 turn. The whole angle of the twist is read from the fixed scale on the movable head of the machine. The scale beam should be kept bal- anced and the maximum load determined. Curves. Plot diagrams to suitable scales with the twisting moment in inch-pounds as ordinates and the unit deformation in radians per inch as abscissae. One of these curves will be drawn with the magnified abscissa and will show the points up to the elastic limit. The other curve will be on a small scale and will show the complete angle-moment diagram up to the rupture. As in other experiments, the straight line portion in the beginning should pass through the origin. If it does not, a straight line parallel to the straight line passing through the plotted points should be drawn through the origin and terminating at the elastic limit. Mark the points corresponding to the elastic limit and maximum load on the curve. Calculations. Compute (1) the shearing stress de- veloped at the elastic limit and the maximum load, using formula. (2) Calculate the modulus of elasticity in shear. (Use the coordinates of any point on the corrected curve of the magnified scale.) (3) Compute also the elastic resilience per cubic inch. Report. The report should follow standard form on p. 7. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 61 Experiment B-6 TEST OF WIRE CABLE The purpose of this test is to determine the strength of a wire cable by testing the separate wires. References Johnson's Materials of Construction, pages 69 and 94. Material. One piece of a wire cable about one foot long. Be sure it is a full strand. Procedure. Note strands in rope, number of turns per foot in strand, number of turns per foot in cable. Untwist wires of strand, note number of wire, determine the diameter in two places on each. Test each ^ire to rupture. Note breaking load. Calculate. 1. Ten- sile strength of wires in pounds per square inch. 2. Strength of cable. 3. Would cable be as strong as the sum of all the strengths of the individual wires? Why? Tests of wire rope as a whole may be made by properly brooming the ends, cleaning and tinning the wires and casting in babbitt metal in conical sockets so designed as to be gripped or held in the heads of the testing machine. The wires may be cleaned by dipping in gasolene followed by hot caustic potash. After cleaning, the wires should be dipped in zinc chloride and then tinned in molten babbitt. Report above items and submit in regular form. NOTE.- Tabulate the number of wires whose strengths are within 5 per cent., 10 per cent., 15 per cent., 20 per cent, 25 per cent, of average strength, etc. 62 LABORATORY MANUAL OF TESTING MATERIALS Experiment B-7 COMPRESSION OF HELICAL SPRING References. Unwin's Strength of Materials. 1918 Standards, Amer. Soc. for Testing Materials, serial A 61-16, page 124. OBJECT. A helical spring under load is a case of torsion. Springs are tested to determine their capacity and travel. The modulus of elasticity in shear and the resilience of the springs may be computed. Material. Two helical springs. Apparatus. Deflection instrument . Procedure. Measure height of spring, diameter of coil, diameter of wire and number of free turns. Place spring in testing machine as for compression. Deter- mine the following items as prescribed by the Amer. Soc. for Testing Materials: (a) Solid Height. The solid height is the perpendicu- lar distance between the plates or the testing machine when the spring is compressed solid with a test load at least \Y times that necessary to bring all the coils in contact. The solid height shall not vary more than % in. from that specified. (6) Free Height. The free height is the height of the spring when the load specified in Paragraph (a) has been released, and is determined by placing a straight edge across the top of the spring and measuring the perpendi- cular distance from the plate on which the spring stands to the straight edge, at the approximate center of the spring. The free height shall not vary more than } in. from that specified. (c) Loaded Height. The loaded height is the distance between the plates of the testing machine when the specified working load is applied. The loaded height INSTRUCTIONS FOR PERFORMING EXPERIMENTS shall not vary more than J^ in. over nor more than in. under that specified. (d) Permanent Set. The permanent set is the differ- ence, if any, between the free height and the height (measured at the same point and in a similar manner) after the spring has been compressed solid three times in rapid succession with the test load specified in Para- graph (a). The permanent set shall not exceed J^2 m - Apply 100 Ib. initial load; adjust the deflectometer. The load is applied by increments of pounds taking travel or compression at each load. Plot load-deformation curve, and energy-travel curve. Calculations. 1. Load at instant spring becomes solid (Maximum load). 2. Fiber stress in shearing at maximum. 3. Resilience per cubic inch at maximum. 4. Modulus of elasticity in shear. Report should cover above elements and appear in general form. Experiment B-8 EFFECT OF OVERSTRAIN ON YIELD POINT OF STEEL Reference. Burr's Elasticity and Resistance of Engineering Materials. Johnson's Materials of Construction Withey and Aston, page 661. Material. Steel bar about 18 in. long. Apparatus. Autographic extensometer. Procedure. Measure the dimension of the test piece and lay off a gage length of 8 in., marking each inch with a light prick punch mark. Fasten into machine, let automatic apparatus draw axis on sheet. Calculate probable elastic limit. Apply load to about two-thirds of this amount, keeping beam carefully balanced. Re- lease the load slowly, noting the path taken by the pencil 64 LABORATORY MANUAL OP TESTING MATERIALS point. Apply load again until past yield point. Release as before. Repeat three or four times. Take all measurements as in B-3. For accurate work, a regular extensometer must be used. Note slope of curves. REPORT. Report should include analysis and discus- sion of results. Experiment B -9 FLEXURE TEST OF CAST IRON OR STEEL This experiment is intended to show method of testing cast iron or steel in flexure and to give data for the com- putation of transverse strength. References. Standards 1918 of Amer. Soc. for Testing Materials, Serial A 48-18. Mills Materials of Construction, Art. 374 and 491. Johnson's Materials of Construction Withey and Aston, Art. 764. Material. A round, or rectangular bar of iron or steel of sufficient length to give a span of at least 10 in. The ''Arbitration Bar" of cast iron is a bar 1}^ in. in diameter and 15 in. long. The bars are in the rough and molded with special treatment. Special Apparatus. A deflectometer reading to 0.001 in. Procedure. Arrange testing machine for transverse test with supporting knife edges at least 10 in. apart (12 in. for the " Arbitration Bar". See Appendix III). Compute breaking load (using table of strengths in appendix) and use an increment of load equal to Jf 5 of the breaking load. Measure deflection at center of span for each increment of load. Results and Conclusions. The report should be written in usual form and contain a comparison with INSTRUCTIONS FOR PERFORMING EXPERIMENTS 65 specifications or other reliable data. Show load-de- flection curve. Experiment B-10 FLEXURE TEST OF BRAKE BEAM Brake beams are required to pass certain specifications of the Master Car Builders' Association. Reference. Report of Master Car Builders' Associa- tion, Vol. 41, 1907. Material. Any brake beam complying with the M. C. B.- Standard Specifications for dimensions. "All beams must be capable of withstanding a load of 7,500 Ib. at the center without more than ^{e i n - de- flection; where it is necessary to use a stronger beam, it must be capable of standing a load of 15,000 Ib. at the center without more than Jle m - deflection." Plot load-deformation curve. Results. Compare with M. C. B. specifications. See general form of report. Experiment B- 11 VIBRATION TEST OF STAYBOLT IRON Staybolt iron should pass certain vibratory tests. Reference. Proceeding of American Society for Test- ing Materials, Volume 5, page 134. Material. Threaded staybolt iron of % in. to 1J in. in diameter. Apparatus. Olsen vibratory testing machine. Method. A threaded specimen, fixed at one end, has the other end moved in a circular path while stressed with a tensile load of 4000 Ib. The circle described shall have a radius of %2 m - at a point 8 in. from end of specimen." The speed of the machine shall be about 100 r.p.m. 66 LABORATORY MANUAL OK TKSTINC MATH III A I ; S Results. Compare results with specifications of the American Society for Testing Materials. See H)ll Year Book. See general form of report. Article 3 TESTS OF WOOD Experiment C-l INSTRUCTIONS FOR LABORATORY EXERCISE FOR THE IDENTIFICATION OF WOODS Purpose. The purpose of this experiment is practice in identification of timbers by appearance. References. Identification of the Economic Woods of the United States Samuel T. Record. Bulletin No. 10 of the Forest Service; and a pamphlet entitled " Trees of the United States Important in Forestry." Material. The material will consist of specimens ex- hibited in the Laboratory for Testing Materials, num- bered in consecutive numbers, including the common species of soft and hard woods; a key to these. Outline of Work. 1. Take the key to these woods and examine each in turn with reference to the material in the text mentioned above. Make notes concerning (a), in the hardness of the material, (6), the character of the grain as shown on the cross section, (c), the kind and distribution of pores, (d) t the relative proportion of spring and summer wood in the rings, (e) } color and appearance of the surface, together with whatever other external features will aid in the identification. Addi- tional short sections of the specimens on exhibit will be found hanging behind the large specimens. The large INSTRUCTIONS FOR PERFORMING EXPERIMENTS 67 specimens should not be damaged, but the smaller duplicates may be cut with a jack knife to determine their working qualities. After this work is performed, the instructor will test the knowledge of the student by asking him to identify selected specimens of the woods. Report/ Report will describe six selected species, together with drawings of the structure of the wood as seen through the magnifying glass. The uses and sources of supply of the wood will also be described. Six SELECTED SPECIMENS I. White Oak. II. Red Oak. III. Yellow Pine (Longleaf). IV. White Pine. V. White Hickory. VI. Hard Maple. Experiment C-2 COMPRESSION OF SHORT WOOD COLUMNS PARALLEL TO GRAIN References. Johnson's Materials of Construction Withey & Aston, page 196. Forest Service Circular No. 213. Timber, its Strength, Seasoning and Grading Betts, page 10, Table 3. This experiment may be preceded by the flexure of short beams C-5 and the material for this test taken from ends of short beams used in C-5. Materials to be Tested/ The columns to be tested are to be about 2 in. X 2 in. X 8 in. They should be sur- faced four sides with the ends squared and smooth cut. 68 LABORATORY MANUAL OP TESTING MATERIALS The wood may be in the air dry, kiln dry, green, or resoaked condition as to moisture content. Apparatus. A compressometer reaching to at least 0.0001 in. Collars, by means of which compressometer is attached to specimen. See Fig. 26. Deformations are more simply but less accurately measured by resting the measuring apparatus on the weighing table, and determining the travel of the move- able head of the testing machine. Procedure. Ascertain and record the following data: (a) Kind of wood, (b) Per cent, of heart and sap wood, (c) Per cent, of summer wood, (d) Annual rings per radial inch, (e) Dimensions of the test piece. (/) Note defects. Lay off the gage length, usually 6 in., on specimen and attach the collars at the ends of gage length. Place in the machine on the spherical bearing plate and center. Apply initial load equal to the first increment (gener- ally 1000 Ib. for the hard woods). After adjusting the compressometer to a zero reading apply the load by mere ments until the elastic limit has been reached. This is seen from the increased increments of deformation at that point. Take a reading for at least two loads beyond the elastic limit. Remove the compressometer and loosen the collars and then, applying the load continuously in the slow speed, obtain the maximum load. Carry the loading far enough to develop the character of fracture. Computations.- Plot a diagram for each specimen with load in pounds as ordinates and deformation in inches as abscissae. If the straight portion of the curve below the elastic limit does not pass through the origin, draw a parallel straight line through the origin. The load at elastic limit should be taken from this curve. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 69 Compute. (a) Unit compress! ve strength at elastic limit. (6) Compressive strength at maximum load. (c) Modulus of elasticity, (d) Modulus of elastic resilience. The report should show sketches of fractured specimens. Experiment C-3 COMPRESSION OF WOOD PERPENDICULAR TO GRAIN This experiment may be preceded by C-5 and the material for this test may be taken from ends of beams used in C-5. References. Johnson's Materials of Construction Aston & Withey, page 197. Forest Service Circular No. 213. Timber, its Strength, Seasoning and Grading Betts, page 10, Table 3. Materials/ Blocks about 2 in. X 2 in. X 8 in. finished four sides. The wood may be in the air dry, kiln dry, green or re- soaked condition as to moisture content. Apparatus. A compressometer reading to 0.0001 in. A rectangular finished loading plate of cast iron or other metal 1 in. X2 in. X4 in. Procedure. Ascertain and record the following data: (a) Kind of wood. (6) Per cent, of heart and sap. (c) Per cent, of summer wood, (d) Annual rings per inch, (e) Dimensions of the block. Place the specimen in the machine flatwise and center. The loading plate should be placed on the specimen flatwise and long axis perpendicular to long axis of specimen. Apply an inital load equal to the first increment of load. Apply the load continuously, preferably by means of a 70 LABORATORY MANUAL OF TESTING MATERIALS spherical bearing directly upon the loading plate, taking readings of compressions for increments of load as follows : 800 Ib. for heart hard woods, and 400 Ib. for sap hard woods and 200 Ib. for soft woods. The loading should be carried to the elastic limit of the specimen. This may be seen from the increased incre- ments of deformation at that point. Do not try to obtain maximum load as there is none in specimens of this size across grain. Computations. Plot a diagram for each specimen with load in pounds as ordinates and deformations in inches as abscissae. The load at elastic limit should be taken from this curve. Compute unit compressive strength at elastic limit. Experiment C-4 TESTS OF WOOD COLUMNS In this experiment, the behavior of the wood under column action may be learned together with constants of strength of columns. Reference. Church's Mechanics of Materials. Merriman's Strength of Materials. Material. Small wood columns of any species. They should be dressed on four sides, true to dimensions and have a slenderness ratio between 20 and 150. At least two columns of each species of wood of different slenderness ratios should be available for test. Procedure.- Ascertain and record all data as in Ex- periment C-2. Stretch a wire along the neutral axis of the narrow side of column. Any convenient method may be used to measure side bending or buckling of the columns. Great care must be taken in centering specimen in the INSTRUCTIONS FOR PERFORMING EXPERIMENTS 71 machine. Apply small initial load and then determine zero reading of deflector at center of column. Apply load in increments of 1000 Ib. per square inch, taking readings of deformation for each instrument. The condition at ends may be one of the two cases: flat ends, hinged ends. Test in each condition of ends, two columns of different slenderness ratios. Calculations. Compute values of S and for each species of wood and for each condition of ends. Use Rankines formula. Experiment C-5 FLEXURE TEST OF SMALL WOOD BEAMS This experiment gives the strength and elasticity of woods as shown in tests of small specimens. Johnson's Materials of Construction Withey and Aston, page 196. Forest Service Circular No. 213. Timber, its Strength, Seasoning and Grading. Belts, page 10, Table 3. Materials. Two or more pieces of wood of oak, pine or other species. The size is about 2 in. X 2 in. X 28 in. The specimens are finished on four sides. The wood may be in the air dry, kiln dry, green, or re-soaked condition as to moisture content. Apparatus. Deflection Instrument reading to 0.001 in. Procedure. Ascertain and record the following data : (a) Kind of wood. (6) Per cent, heart wood and sap wood, (c) Per cent, summer wood, (d) Annual rings per radial inch, (e) Dimensions of piece. (/) Weight of specimen in grams, (g) Note defects such as knots, season checks, rot, etc. On one side of specimen mark the neutral axis and 72 LABORATORY MANUAL OF TESTING MATERIALS span-length and mid-span lines. The span to be used is ... in. Place the beam upon the knife edge supports, using short iron plates to prevent local crushing of the wood and binding between the supports. If there is clearance enough, two plates with two rollers between should be used at each support to allow freedom of bending. Apply an initial load of 100 Ib. and adjust deflection in- strument to read zero. See Fig. 8. NOTE. Common methods of measuring deflections are as follows: (a) Place a deflectometer on base of machine under- center of beam. (Fig. 24.) This is equivalent to having a scale or vernier attached to the loading yoke as in some special flexure machines. (6) Hang a special deflectometer on pins or tacks in the neutral axis over supports and attach the wire of needle to tack in neutral axis at mid-span. See that wire is vertical. (Fig. 8.) (c) Stretch a wire between tacks over supports and scale attached to beam at mid-span. A mirror or polished scale should be used so that image of wire may be seen, thus avoiding parallax. (Fig. 9.) Of these methods, the second is the most accurate but the first and last may be used in certain work. Apply the load continuously at a slow speed and take readings of deflection for increments of 100 Ib. load. If care is exercised, in keeping the beam balanced near the point of failure, it will be possible to read the correct load and deflection at failure even though this does not occur at one of the regular load increments. After obtaining the maximum load, carry the loading only far enough to develop the point and character of fracture. INSTRUCTIONS FOB PERFORMING EXPERIMENTS 73 Sketch and describe fractures. Moisture Content of Specimen. Cut from the specimen near the point of failure a disk about 1 in. in thickness. Trim off all loose wood and weigh on sensi- tive balances. This moisture disk is to be oven-dried and again weighed. The loss in weight expressed as a per cent, of dry weight gives the per cent, of moisture in beam. For Tests in Compression. Saw from the beam al- ready tested, two test pieces 8 in. in length to be used in Experiments C-2 and C-3. Computations. Plot a diagram with load in pounds as ordinates and deformation in inches as abscissae. Draw the correction curve through the origin, if necessary. The load at elastic limit is taken from this curve. Compute.- (a) Fiber stress at elastic limit. (6) Mod- ulus of Rupture. (Fiber stress at maximum load.) (c) Modulus of Elasticity. (Use corrected deflections.) (d) Elastic Resilience per cubic inch, (e) Rupture work per cubic inch (/) Per cent, moisture, (g) Specific gravity. Discussion of Results. See general form of report. Experiment C-6 FLEXURE TEST OF LARGE WOOD BEAMS The strength and elasticity of timber in full size speci- mens are determined in this test. References. Circular No. 38, of Forest Service. Johnson's Materials of Construction Aston and Withey, Articles 230-232. Bulletin of Forest Service No. 108. Material. Full size specimens of any wood in which span length does not exceed 16 ft. The specimens 74 LABORATORY MANUAL OF TKSTIMi MATKKIAI^ may be finished or in the rough but should be sawed true to size and squared. Procedure. Ascertain and record all data as in Ex- periment C-5. The method of testing is the same as in C-5 except that the load is applied at the third points, to approach as nearly as possible to conditions of uni- form loading. Moisture content is obtained as in C-5. Computations. Make all computations as in Experi- ment C-5. Discussion of Results. Compare results with aver- age of other . tests upon same and different kinds of timber. Experiment C-7 IMPACT TEST OF WOODEN BEAMS In determining the relative brittleness of different tim- bers, tests in impact bending will be made. Reference. Circular No. 38, Forest Service. Material/ Two 2 in. X 2 in. X 30 in. sticks. Any timber. Special Apparatus/ Impact machine. Procedure The resistance of a specimen of wood under impa t is usually determined by dropping a given weight from successively increasing heights. The suc- cessive amounts of deformation and set of the specimen and rebound of the hammer are recorded on the drum. The elastic strength of the specimen is fixed at that limit at which the deflection suddenly increases. At this limit a sudden increase in the set of the specimen, as well as a maximum amount of rebound of the hammer, usualh r occurs. In making the test the hammer is allowed to rest upon the upper surface of the specimen, and a zero or datum line is drawn on the drum. The deflection under the dead load of the hammer is obtained from a static cross- INSTRUCTIONS FOR PERFORMING EXPERIMENTS 75 bending test of similar material. A corrected zero line can thus be drawn. Then blows of a weight dropped from increasing heights are delivered to the specimen, and records taken on the drum. A sample record is seen in Fig. 16. The height of the drop at which any rupture of the specimen occurs is noted, together with other phenomena of test. Sample log sheets and calculations will be found in the Appendix of Circular 38, Forest Service. The machine is calibrated in advance to determine the proportion of the height of fall which is not effective because of friction and lag of magnet. Occasionally the beam is ruptured under a single blow of the hammer falling from a height greater than that necessary to rupture the specimen. In this case the resi- dual energy resident in the hammer, after rupture of the specimen, must be determined in order that the amount of energy used up in rupturing the specimen may be known. The zero or datum line is determined as before, the hammer is released from a height greater than that neces- sary to rupture the specimen, and a record is* taken of the circumstances of the impact. The tuning fork must be held on the drum during impact. A sample record is shown in Fig. 17. Calculations. Determine rupture-work, height of drop at elastic limit and maximum. Specific gravity, etc. Experiment C-8 ABRASION TEST OF WOOD Purpose. The purpose of this test is to determine^ the relative wearing ability of different woods. Material. 2 in.X2 in.X2 in. cubes of wood, three specimens, and three standard maple blocks. 76 LABORATORY MANUAL OF TKSTING MATERIALS Apparatus. Dorry abrasion machine for wood. Methods. Measure blocks carefully at the four corners. Place blocks in machine in one of the six pos- sible ways (see instructor). The standard maple block and test specimens must be exactly the same and wear against the same portion of the paper. Run the machine at 68 r.p.m. until the standard or test specimen wears down about Y in., or, in time units, 15 minutes. Results. Measure again at four corners. Calculate volume worn away and per cent, of wear of test specimen in relation to that of standard specimen. Compare with other tests. Caution. Take care that weight of the holder is always on both pieces. Article 4 TESTS OF CEMENTS 1 VI. SAMPLING Number of Samples 16. Tests may be made on individual or composite samples as may be ordered. Each test sample should weigh at least 8 Ib. 17. (a) Individual Sample. If sampled in cars one test sample shall be taken from each 50bbl. or fraction thereof. If sampled in bins one sample shall be taken from each 100 bbl. (6) Composite Sample. If sampled in cars one sample shall be taken from one sack in each 40 sacks (or 1 bbl. in each 10 bbl.) and combined to form one test sample. If sampled in bins or warehouses one test sample shall represent not more than 200 bbl. 1 Authorized Reprint from the Copyrighted A. S. T. M. Standards (1018), American Society for Testing Materials, Philadelphia, Pa. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 77 Method of Sampling 18. Cement may be sampled at the mill by any of the following methods that may be practicable, as ordered: (a) From the Conveyor Delivering to the Bin. At least 8 Ib. of cement shall be taken from approximately each 100 bbl. passing over the conveyor. (6) From Filled Bins by Means of Proper Sampling Tubes. Tubes inserted vertically may be used for sampling cement to a maximum depth of 10 ft. Tubes inserted horizontally may be used where the construc- tion of the bin permits. Samples shall be taken from points well distributed over the face of the bin. (c) From Filled Bins at Points of Discharge.- Sufficient cement shall be drawn from the discharge openings to obtain samples representative of the cement contained in the bin, as determined by the appearance at the dis- charge openings of indicators placed on the surface of the cement directly above these openings before drawing of the cement is started. Treatment of Sample 19. Samples preferably shall be shipped and stored in air-tight containers. Samples shall be passed through a sieve having 20 meshes per linear inch in order to thor- oughly mix the sample, break up lumps and remove foreign materials. VII. CHEMICAL ANALYSIS Loss on Ignition 20. One gram of cement shall be heated in a weighed covered platinum crucible, of 20 to 25c.c. capacity, as follows, using either method (a) or (b) as ordered: (a) The crucible shall be placed in a hole in an as- 78 LABORATORY MANUAL OF TESTING MATERIALS bestos board, clamped horizontally so that about three- fifths of the crucible projects below, and blasted at a full red heat for 15 minutes with an inclined flame; the loss in weight shall be checked by a second blasting for 5 minutes. Care shall be taken to wipe off particles of asbestos that may adhere to the crucible when with- drawn from the hole in the board. Greater neatness and shortening of the time of heating are secured by making a hole to fit the crucible in a circular disk of sheet platinum and placing this disk over a somewhat larger hole in an asbestos board. (6) The crucible shall be placed in a muffle at any temperature between 900 and 1000 C. for 15 minutes and the loss in weight shall be checked by a second heating for 5 minutes. 21. A permissible variation of 0.25 will be allowed, and all results in excess of the specified limit but within this permissible variation shall be reported as 4 per cent. Insoluble Residue 22. To a 1-g. sample of cement shall be added 10 c.c. of water and 5 c.c. of concentrated hydrochloric acid; the liquid shall be warmed until effervescence ceases. The solution shall be diluted to 50 c.c. and digested on a steam bath or hot plate until it is evident that decompo- sition of the cement is complete. The residue shall be filtered, washed with cold water, and the filter paper and contents digested in about 33 c.c. of a 5 per cent, solution of sodium carbonate, the liquid being held at a temperature just short of boiling for 15 minutes. The remaining residue shall be filtered, washed with cold water, then with a few drops of hot hydrochloric acid, 1:9, and finally with hot water, and then ignited at u red heat and weighed as the insoluble residue. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 79 23. A permissible variation of 0.15 will be allowed, and all results in excess of the specified limit but within this permissible variation shall be reported as .85 per cent. Sulphuric Anhydride 24. One gram of the cement shall be dissolved in 5 c.c. of concentrated hydrochloric acid diluted with 5 c.c. of water, with gentle warming; when solution is complete 40 c.c. of water shall be added, the solution filtered, and the residue washed thoroughly with water. The solution shall be diluted to 250 c.c., heated to boiling and 10 c.c. of a hot 10-per cent, solution of barium chloride shall be added slowly, drop by drop, from a pipette and the boiling continued until the precipitate is well formed. The solution shall be digested on the steam bath until the precipitate has settled. The precipitate shall be filtered, washed, and the paper and contents placed in a weighed platinam crucible and the paper slowly charred and consumed without flaming. The barium sulfate shall then be ignited and weighed. The weight ob- tained multiplied by 34.3 gives the percentage of sulfuric anhydride. The acid filtrate obtained in the determina- tion of the insoluble residue may be used for the estima- tion of sulfuric anhydride instead of using a separate sample. 25. A permissible variation of 0.10 will be allowed, and all results in excess of the specified limit but within this permissible variation shall be reported as 2.00 per cent. Magnesia 26. To 0.5 g. of the cement in an evaporating dish shall be added 10 c.c. of water to prevent lumping and then 10 c.c. of concentrated hydrochloric acid. The liquid 80 LABORATORY MANUAL OF TESTING MATERIALS shall be gently heated and agitated until attack is complete. The solution shall then be evaporated to complete dryness on a steam or water bath. To hasten dehydration the residue may be heated to 150 or even 2dOC. for one-half to one hour. The residue shall be treated with 10 c.c. of concentrated hydrochloric acid diluted with an equal amount of water. The dish shall be covered and the solution digested for ten minutes on a steam bath or water bath. The diluted solution shall be filtered and the separated silica washed thor- oughly with water. 1 Five cubic centimeters of concen- trated hydrochloric acid and sufficient bromine water to precipitate any manganese which may be present, shall be added to the filtrate (about 250 c.c.). This shall be made alkaline with ammonium hydroxide, boiled until there is but a faint odor of ammonia, and the precipitated iron and aluminum hydroxides, after settling, shall be washed with hot water, once by decantation and slightly on the filter. Setting aside the filtrate, the precipitate shall be transferred by a jet of hot water to the precipi- tating vessel and dissolved in 10 c.c. of hot hydrochloric acid. The paper shall be extracted with acid, the solution and washings being added to the main solution. The aluminum and iron shall then be reprecipitated at boiling heat by ammonium hydroxide and bromine water in a volume of about 100 c.c., and the second precipitate shall be collected and washed on the filter used in the first instance if this is still intact. To the combined filtrates from the hydroxides of iron and alumi- num, reduced in volume if need be, 1 c.c. of ammonium hydroxide shall be added, the solution brought to boiling, 25 c.c. of a saturated solution of boiling ammonium 1 Since this procedure does not involve the determination of silica, .1 second evaporation is unnecessary. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 81 oxalate added, and the boiling continued until the precipi- tated calcium oxalate has assumed a well-defined granu- lar form. The precipitate after one hour shall be filtered and washed, then with the filter shall be placed wet in a platinum crucible, and the paper burned off over a small flame of a Bunsen burner; after ignition it shall be redissolved in hydrochloric acid and the solution diluted to 100 c.c. Ammonia shall be added in slight excess, and the liquid boiled. The lime shall then be reprecipitated by ammonium oxalate, allowed to stand until settled, filtered and washed. The combined filtrates from the calcium precipitates shall be acidified with hydrochloric acid, concentrated on the steam bath to about 150 c.c., and made slightly alkaline with am- monium hydroxide, boiled and filtered (to remove a little aluminum and iron and perhaps calcium). When cool, 10 c.c. of saturated solution of sodium-ammonium- hydrogen phosphate shall be added with constant stirring. When the crystallin ammonium-magnesium orthophosphate has formed, ammonia shall be added in moderate excess. The solution shall be set aside for several hours in a cool place, filtered and washed with water containing 2.5 per cent, of NH 3 . The precipitate shall be dissolved in a small quantity of hot hydro- chloric acid, the solution diluted to about 100 c.c., 1 c.c. of a saturated solution of sodium-ammonium-hydrogen phosphate added, and ammonia drop by drop, with constant stirring, until the precipitate is again formed as described and the ammonia is in moderate excess. The precipitate shall then be allowed to stand about two hours, filtered and washed as before. The paper and contents shall be placed in a weighed platinum crucible, the paper slowly charred, and the resulting carbon care- fully burned off. The precipitate shall then be ignited 82 LABORATORY MANUAL OF TESTING MATKIMAI/* to constant weight over a Meker burner, or a blast not strong enough to soften or melt the pyrophosphate. The weight of magnesium pyrophosphate obtained multiplied by 72.5 gives the percentage of magnesia. The precipitate so obtained always contains some cal- cium and usually small quantities of iron aluminum, and manganese as phosphates. 27. A permissible variation of 0.4 will be allowed, and all results in excess of the specified limit but within this permissible variation shall be reported as 5.00 per cent. VIII. DETERMINATION OF SPECIFIC GRAVITY 28. The determination of specific gravity shall be mude with a standardized Le Chatelier apparatus which con- forms to the requirements illustrated in Fig. I. 1 This apparatus is standardized by the United States Bureau of Standards. Kerosene free from water, or benzine not lighter than 62 Baume, shall be used in making this determination. 29. The flask shall be filled with either of these liquids to a point on the stem between zero and 1 c.c., and 64 g. of cement, of the same temperature as the liquid, shall be slowly introduced, taking care that the cement does not adhere to the inside of the flask above the liquid and to free the cement from air by rolling the flask in an inclined position. After all the cement is introduced, the level of the liquid will rise to some divi- sion of the graduated neck; the difference between read- ings is the volume displaced by 64 g. of the cement. The specific gravity shall then be obtained from the formula Weight of cement (g.) Specific gravity = Disp] - ced ; volume (c ; c .) 1 American Society for Testing Materials, Standards 1918, page 511. INSTRUCTIONS FOR 1'KRFORMING EXPERIMENTS 83 30. The flask, during the operation, shall be kept im- mersed in water, in order to avoid variations in the tem- perature of the liquid in tihe flask, which shall not exceed 0.5 C. The results of repeated tests should agree within 0.01. 31. The determination of specific gravity shall be made on the cement as received; if it falls below 3.10, a second determination shall be made after igniting the sample as described in Section 20. IX. DETERMINATION OF FINENESS Apparatus 32. Wire cloth for standard sieves for cement shall be woven (not twilled) from brass, bronze, or other suitable wire, and mounted without distortion on frames not less than 1J2 in. below the top of the frame. The sieve frames shall be circular, approximately 8 in. in diameter, and may be provided with a pan and cover. 33. A standard No. 200 sieve is one having nominally an 0.0029-in. opening and 200 wires per inch standardized by the U. S. Bureau of Standards, and conforming to the following requirements : The No. 200 sieve should have 200 wires per inch, and the number of wires in any whole inch shall not be outside the limits of 192 to 208. No opening between adjacent parallel wires shall be more than 0.0050 in. in width. The diameter of the wire should be 0.0021 in. and the average diameter shall not be outside the limits 0.0019 to 0.0023. The value of the sieve as determined by sieving tests made in conformity with the standard specification for these tests on a standardized cement which gives a residue of 25 to 20 per cent, on the No. 200 sieve, or on other similarly graded material, shall not show a varia- 84 LABORATORY MANUAL OF TESTING MATERIALS tion of more than 1.5 per cent, above or below the stand- ards maintained at the Bureau of Standards. Method 34. The test shall be made with 50 g. of cement. The sieve shall be thoroughly clean and dry. The cement shall be placed on the No. 200 sieve, with pan and cover attached, if desired, and shall be held in one hand in a slightly inclined position so that the sample will be well distributed over the sieve, at the same time gently strik- ing the side about 150 times per minute against the palm of the other hand on the up stroke. The sieve shall be turned every 20 strokes about one-sixth of a revolution in the same direction. The operation shall continue until not more than 0.05 g. passes through in one minute of continuous sieving. The fineness shall be determined from the weight of the residue on the sieve expressed as a percentage of the weight of the original sample. 35. Mechanical sieving devices may be used, but the cement shall not be rejected if it meets the fineness re- quirement when tested by the hand method described in Section 34. 36. A permissible variation of 1 will be allowed, and all results in excess of the specified limit but within this per- missible variation shall be reported as 22 per cent. X. MIXING CEMENT PASTES AND MORTARS 37. The quantity of dry material to be mixed at one time shall not exceed 1000 g. nor be less than 500 g. The proportions of cement or cement and sand shall be stated by weight in grams of the djry materials; the quantity of water shall be expressed in cubic centimeters (1 c.c. of water =1 g.). The dry materials shall be weighed, INSTRUCTIONS FOR PERFORMING EXPKRIMENTS 85 placed upon. a non-absorbent surface, thoroughly mixed dry if sand is used, and a crater formed in the center, into which the proper percentage of clean water shall be poured; the material on the outer edge shall be turned into the crater by the aid of a trowel. After an interval of Yi minute for the absorption of the water the operation shall be completed by continuous, vigorous mixing, squeezing and kneading with the hands for at least one minute. 1 During the operation of mixing, the hands should be protected by rubber gloves. 38. The temperature of the room and the mixing water shall be maintained as nearly as practicable at 21C. (70F.). XI. NORMAL CONSISTENCY 39. The Vicat apparatus consists of a frame A, Fig. 2, page 514, Year Book 1918 bearing a movable rod B, weighing 300 g., one end C being 1 cm. in diameter for a distance of 6 cm., the other having a removable needle D, 1 mm. in diameter, 6 cm. long. The rod is reversible, and can be held in any desired position by a screw E, and has midway between the ends a mark F which moves under a 'scale (graduated to millimeters) attached to the frame A. The paste is held in a conical, hard- rubber ring G, 7 cm. in diameter at the base, 4 cm. high, resting on a glass plate H about 10 cm. square. 40. In making the determination, 500 g. of cement, with a measured quantity of water, shall be kneaded into 1 In order to secure uniformity in the results of tests for the time of setting and tensile strength the manner of mixing above de- scribed should he carefully followed. At least one minute is necessary to obtain the desired plasticity which is not appreciabty affected by continuing the mixing for several minutes. The exact time necessary is dependent upon the personal equation of the operator. The error in mixing should be on the side of over mixing. 86 LABORATORY MANUAL OF TESTING MATERIALS a paste, as described in Section 37, and quickly formed into a ball with the hands, completing the operation by tossing it six times from one hand to the other, main- tained about 6 in. apart; the ball resting in the palm of one hand shall be pressed into the larger end of the rubber ring held in the other hand, completely filling the ring with paste; the excess at the larger end shall then be removed by a single movement of the palm of the hand; the ring shall then be placed on its larger end on a glass plate and the excess paste at the smaller end sliced off at the top of the ring by a single oblique stroke of a trowel held at a slight angle with the top of the ring. PERCENTAGE OF WATER FOR STANDARD MORTARS Percentage of water for neat cement pa^te of normal consistency 15 Percentage of water for one cement, three standard Ottawa sand Percentage of water for neat cement paste of normal consistency Percentage of water for one cement, three standard Ottawa sand 9.0 1 23 10.3 16 9.2 24 10.5 17 9.3 25 10.7 18 9.5 26 10.8 19 9.7 27 11.0 20 9.8 28 11.2 21 10.0 29 11.3 22 10.2 1 30 11.5 During these operations care shall be taken not to com- press the paste. The paste confined in the ring, resting on the plate, shall be placed under the rod, the larger end of which shall be brought in contact with the surface of the paste; the scale shall be then read, and the rod quickly released. The paste shall be of normal consis- tency when the rod settles to a point 10 mm. below the INSTRUCTIONS FOR PERFORMING EXPERIMENTS 87 original surface in % minute after being released. The apparatus shall be free from all vibrations during the test. Trial pastes shall be made with varying percent- ages of water until the normal consistency is obtained. The amount of water required shall be expressed in percentage by weight of the dry cement. 41. The consistency of standard mortar shall depend on the amount of water required to produce a paste of normal consistency from the same sample of cement. Having determined the normal consistency of the sample, the consistency of standard mortar made from the same sample shall be as indicated in Table I, the values being in percentage of the combined dry weights of the cement and standard sand. XII. DETERMINATION OF SOUNDNESS 1 42. A steam apparatus, which can be maintained at a temperature between 98 and 100C., or one similar to that shown in Fig. 3, Standards Amer. Soc. for Test. Materials, 1918, p. 516 is recommended. The capacity of this apparatus may be increased by using a rack for holding the pats in a vertical or inclined position. 43. A pat from cement paste of normal consistency about 3 in. in diameter, ^ in. thick at the center, and tapering to a thin edge, shall be made on clean glass plates about 4 in. square, and stored in moist air for 24 1 Unsoundness is usually manifested by change in volume which causes distortion, cracking, checking or disintegration. Pats improperly made or exposed to drying may develop what are known as shrinkage cracks within the first 24 hours and are not an indication of unsoundness. These conditions are illustrated in Fig. 4. See American Society for Testing Materials, page 517. The failure of the pats to remain on the glass or the cracking of the glass to which the pats are attached does not necessarily indi- cate unsoundness. 88 LABORATORY MANUAL, OF TESTING MATERIALS hours. In molding the pat, the cement paste shall first be flattened on the glass and the pat then formed by drawing the trowel from the outer edge toward the center. 44. The pat shall then be placed in an atmosphere of steam at a temperature between 98 and 100C. upon a suitable support 1 in. above boiling water for 5 hours. 45. Should the pat leave the plate, distortion may be detected best with a straight edge applied to the surface which was in contact with, the plate. XIII. DETERMINATION OF TIME OF SETTING 46. The following are alternate methods, either of which may be used as ordered : 47. The time of setting shall be determined with the Vicat apparatus described in Section 39. 48. A paste of normal consistency shall be molded in the hard-rubber ring G as described in Section 40, and placed under the rod B, the smaller end of which shall then be carefully brought in contact with the surface of the paste, and the rod quickly released. The initial set shall be said to have occurred when the needle ceases to pass a point 5 mm. above the glass plate in Y^ minute after being released; and the final set, when the needle does not sink visibly into the paste. The test pieces shall be kept in moist air during the test. This may be accomplished by placing them on a rack over water contained in a pan and covered by a damp cloth kept from contact with them by means of a wire screen; or they may be stored in a moist closet. Care shall be taken to keep the needle clean, as the collection of cement on the sides of the needle retards the penetration, while cement on the point may increase the penetration. The time of setting is affected not only by the percentage and temperature of the water used and the amount of knead- INSTRUCTIONS FOR PERFORMING EXPERIMENTS 89 ing the paste receives, but by the temperature and humid- ity of the air, and its determination is therefore only approximate. 49. The time of setting shall be determined by the Gillmore needles. The Gillmore needles should prefer- ably be mounted as shown in Fig. 5 (6). 1 50. The time of setting shall be determined as follows : A pat of neat cement paste about 3 in. in diameter and 12 in. in thickness with a flat top (Fig. 5 (a)), 2 mixed to a normal consistency, shall be kept in moist air at a tem- perature maintained as nearly as practicable at 21C. (70F.). The cement shall be considered to have acquired its initial set when the pat will bear, without appreciable indentation, the Gillmore needle ^{2 i n - in diameter, loaded to weigh J^ Ib. The final set has been acquired when the pat will bear without appreciable indentation, the Gillmore needle ^4 in. in diameter, loaded to weigh 1 Ib. In making the test the needles shall be held in a vertical position, and applied lightly to the surface of the pat. XIV. TENSION TESTS 51. The form of test piece shown in Fig. 6 1 shall be used. The molds shall be made of non-corroding metal and have sufficient material in the sides to prevent spreading during molding. Gang molds when used shall be of the type shown in Fig. 7. 3 Molds shall be wiped with an oily cloth before using. 52. The sand to be used shall be natural sand from Ottawa, 111., screened to pass a No. 20 sieve, and retained 1 Standards, 1918, Amer. Soc. for Test. Materials, p. 519. 2 Standard 1918, Amer. Soc. for Test. Materials, p. 519. 3 See 1918 Standards, Amer. Soc. for Testing Materials, p. 520, 521. 90 LABORATORY MANUAL OF TESTING MATERIALS on a No. 30 sieve. This sand may be obtained from the Ottawa Silica Co., at a cost of two cents per pound, f.o.b. cars, Ottawa, 111. 53. This sand, having passed the No. 20 sieve, shall be considered standard when not more than 5 g. pass the No. 30 sieve after one minute continuous sieving of a 500-g. sample. 54. The sieves shall conform to the following specifica- tions : The No. 20 sieve shall have between 19.5 and 20.5 wires per whole inch of the warp wires and between 19 and 21 wires per whole inch of the shoot wires. The diameter of the wire should be 0.0165 in. and the average diameter shall not be outside the limits of 0.0160 and 0.0170 in. The No. 30 sieve shall have between 29.5 and 30.5 wires per whole inch of the warp wires and between 28.5 and 31.5 wires per whole inch of the shoot wires. The diameter of the wire should be 0.0110 in. and the average diameter shall not be outside the limits 0.0105 to 0.01 15 in. 55. Immediately after mixing, the standard mortar shall be placed in the molds, pressed in firmly with the thumbs and smoothed off with a trowel without ram- ming. Additional mortar shall be heaped above the mold and smoothed off with a trowel; the trowel shall be drawn over the mold in such a manner as to exert a moderate pressure on the material. The mold shall then be turned over and the operation of heaping, thumb- ing and smoothing off repeated. 56. Tests shall be made with any standard machine. The briquettes shall be tested as soon as they are re- moved from the water. The bearing surfaces of the clips and briquettes shall be free from grains of sand or INSTRUCTIONS FOR PERFORMING EXPERIMENTS 91 dirt. The briquettes shall be carefully centered and the load applied continuously at the rate of 600 Ib. per minute. 57. Testing machines should be frequently calibrated in order to determine their accuracy. 58. Briquettes that are manifestly faulty, or which give strengths differing more than 15*per cent, from the average value of all test pieces made from the same sample and broken at the same period, shall not be considered in determining the tensile strength. XV. STORAGE OF TEST PIECES 59. The moist closet may consist of a soapstone, slate or concrete box, or a wooden box lined with metal. If a wooden box is used, the interior should be covered with felt or broad wicking kept wet. The bottom of the moist closet should be covered with water. The interior of the closet should be provided with non-absorbent shelves on which to place the test pieces, the shelves being so arranged that they may be withdrawn readily. 60. Unless otherwise specified all test pieces, immedi- ately after molding, shall be placed in the moist closet for from 20 to 24 hours. 61. The briquettes shall be kept in molds on glass plates in the moist closet for at least 20 hours. After 24 hours in moist air the briquettes shall be immersed in clean water in storage tanks of non-corroding material. 62. The air and water shall be maintained as nearly as practicable at a temperature of 21C. (70F.). 92 LAUOHATOHY MANUAL OF TESTING MATERIALS Experiment D-7 STRENGTH OF CEMENT MORTARS IN COMPRESSION This experiment will give the quality of a cement as shown by compression tests of standard Ottawa sand mortars. References. Proc. Amer. Soci for Testing Materials, 1919, Part I. Hool and Johnson Handbook, page 10. Mills Material of Construction, page 164 . Material : Any brand of cement. Special Apparatus: At least six cylindrical molds, 2 in. in diameter and 4 in. in height. Standard metal tam- per 1 in. in diameter and % Ib. in weight. Procedure. Using standard Ottawa sand mix a 1 to 3 mortar of Normal Consistency. (See Table, p. 86). NOTE. If sufficient mortar for six 2 by 4-in. cylinders is to be mixed in a single batch, 750 g. of cement and 2250 g. of standard sand will be required.. In this case the mixing shall be continued for 1^ minutes. (See standard methods of mixing and molding, page 84.) Place the empty mold on an oiled glass plate and fill with the mortar in layers of 1 in. tamping each layer with the standard metal tamper. The top should be carefully finished by heaping up the mortar and smooth- ing off with the trowel. An oiled glass cover plate should be placed on top and remain until molds are removed (after 1 day storage in moist air). Test the specimens at the end of 6 and 27 days' storage in water. The testing machine should be capable of applying the load continuously and uniformly to failure. The moving head of the testing machine shall travel at the rate of not less than 0.05 or more than 0.10 in. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 93 per minute. During the test, a spherical bearing block, accurately centered, shall be used on top of the cylinder. Report : Follow the standard form on page 7. TABLE ON UNIT STRESSES FOR LOADS ON 2-iN. CYLINDERS (3.14 SQ. IN.) Total load Unit stress 10 3 20 6 30 40 10 13 50 16 60 19 70 22 80 25 90 29 Total load (lb.)- 000 100 200 300' 400 500 600 700 800 900 Unit stress (lb. per sq. in.) 0000 32 64 95 127 159 191 223 255 286 1000 j 318 350 382 413' 445 477 509 541 573 604 2000 637 669 701 732 764 796 828 860 892 923 3000 955 987 1019 1050 1082 1114 1146 1178 1210 1241 4000 1273 1305 1337 13681 1400 1432 1464 1496 1528 1559 5000 1592 1624 1656 1687 1719 1751 1783 1815 1847 1878 6000 1910 1942 1974 2005 2037 2069 2101 2133 2165 2196 7000 2228 2260 2292i 2323 2355 2387 2419 2451 2483 2514 8000 2546 2578 2610 2641 2673 2705 2737 2769 2801 2832 9000 2865 2897 2929 2960 2992 3024 3056 3088 3120 3151 Article 5 STUDY OF AGGREGATES Notes on the Sampling of Aggregates Used in Con- crete Construction. The value of tests of the constituent materials entering into a concrete construction depend almost entirely upon whether the samples obtained are thoroughly representative of the aggregates used. When it is positively certain that the material sampled is the material shipped and used in the construction then the samples may be taken at the pit or quarry. When there is uncertainty as to this point, samples for test 94 LABORATORY MANUAL OF TESTING MATERIALS should be taken from shipments as they arrive where they are to be used. SAMPLING OF STONE FROM LEDGES OR QUARRIES FOR QUALITY Inspect ledge or quarry face closely to determine any variation in different layers. Observe any difference in color or structure, and if necessary to secure unweathered specimens, break pieces from different layers. For standard stone test take separate samples of at least 30 ,lb. each of fresh unweathered specimens from all layers that appear to vary in color or structure. When more than one piece is taken, the minimum size shall be 2 in., except that there shall be one piece of a minimum size of 4 in. X 5 in. X- 3 in. on which the bedding plane is marked. This latter piece shall be free from seams or fractures as it is used in the toughness or compression test. The size of sample for concrete test will have to have special instruction as it depends on the kind of tests to be made and the number of specimens necessary. SAMPLING OF GRAVEL OR SAND Sampling at a pit which has exposed vertical faces may be done by scooping out a small uniform vertical channel from bottom to top of faces. If the material excavated from this channel is more than desired it may be reduced by the method of quartering. Samples taken in this way from the various faces of a pit should be kept separate with the proper identification as to location, inasmuch as it may happen that some parts of the same bank may yield an undesirable material. The pit should be carefully examined before selecting INSTRUCTIONS FOR PERFORMING EXPERIMENTS 95 the location of a sample. It frequently happens that a bank is not of a homogeneous mixture throughout and that layers or pockets are found in which is a material of of uniform size or perhaps of clay. Boulders may be present in one section and not in another. If the pit is a large one more than one sample must be taken to properly represent the deposit. Deposits that have no open face shall be sampled by means of test pits. The number and depth of these will depend on local conditions and the amount of material to be used from the source. Sampling the aggregate after it has arrived on the job may be done by collecting and mixing a small quantity from many different parts of the pile, or bin. These small quantities should be obtained by digging into the pile not by collecting what rolls down the outside as that is likely to be composed of only the coarser particles. The test samples themselves should always be acquired from the larger samples by the method of quartering. Quartering. To quarter a sample of Aggregate it is spread out on a clean flat surface in the form of a circular disc of uniform thickness. Care should be taken that particles of different size are distributed through the mass. The material is then divided into four quarters and two opposite quarters removed completely. The remaining quarters are then mixed together and the operation repeated. This is done until the quantity remaining is the size required for the experiment. Shipping and Storing of Samples. The samples should be shipped and stored in such a way as to retain as much as possible of the natural moisture of the material. 90 LABORATORY MANUAL OF TESTING MATERIALS Experiment E-2 TEST OF SAND FOR CLEANNESS References. Engineering News, Feb. 4, 1915, page 204. Engineering Record, Jan. 8, 1916, pages 48 and 49. Abrams-Harder Field test for Organic Impurities in Sands, Proc. Amer. Soc. for Testing Materials, Vol. XIX, Part 1, 1919. Comment. The impurities in sand are: (1) Silt, the fine scum that settles on sand that has. been shaken in water. Silt may contain organic matter, such as loam, sugar, sewage, that may prevent concrete from harden- ing. (2) Clay, an inorganic, fine material that may assist in filling up the pores in a clean concrete. A dirty sand will stain the palm of the hand, but- specific tests should be made: 1. Method of Washing. Dry a 220 gram sample obtained by quartering and at room temperature to avoid baking the clay. Extra care must be taken in dividing the material after drying to prevent separation of fine from coarse. Weigh 200 grams on the 100 sieve, soak in water to soften any lumps; wash on the sieve in a gentle stream of water; dry under a gas burner, and reweigh. Per cent, of silt is loss in weight divided by 200 and multiplied by 100. 2. Method of Decantation or Elutriation (for field use) . Place 20 c.c. of sand, obtained by quartering, in a 100 c.c. cylinder with 30 c.c. of lukewarm water. Stir with u wire for 30 seconds; allow to settle for 30 seconds. Decant water in a second 100 c.c. cylinder. Stir up sand in 1st. cylinder with fresh portion of water, and repeat process 3 times. Settle the two cylinders for 1 hour. Note silt in cylinder L No, 2 and sand in Cylinder No. 1, INSTRUCTIONS FOR PERFORMING EXPERIMENTS 97 Per cent, of Silt = Number of c.c. in Cyl. No. 2 y 100 c7c. of silt in Cyf. No. 2 + c.c. of sand in No. 1 A more accurate expression is perhaps obtained by dividing amount of silt by original volume of sand. NOTE. A rough method is to stir up sand in Cyl. No. 1 and allow silt to settle on top. Measure height of sand and of silt on top. NOTE. The per cent, of silt by volume is from one to two times the per cent, by weight. 3. Silt Determination of Road Sands and Gravel. PROPOSED TENTATJVE TEST, AMER. Soc. FOR TESTING MATERIALS 1920 1. Scope. This test covers the determination of the quantity of clay and silt in natural sands and gravel to be used in highway construction. 2. Treatment of Sample. The sample as received shall be moistened and thoroughly mixed, then dried to constant weight at a temperature between 100 and 110C. (212 and230F.) 3. Method. A representative portion of the dry material, weighing 500 g. for sand and not less than 50 times the weight of the largest stone in the sample for gravel shall be selected from the sample, and placed in a dried and accurately weighed pan or vessel. The pan shall be 12 in. (30.2 cm.) in diameter by not less than 4 in. (10.2 cm.) deep, as nearly as may be obtained. Pour sufficient water in the pan to cover the gravel and agitate vigorously for 15 seconds, using a trowel or stirring rod. Allow to settle for 15 seconds, and then pour off the water into a tared evaporating dish, taking 98 LABORATORY MANUAL OF TESTING MATERIALS care not to pour off any gravel. Repeat until the wash water is clear. Dry the washed material to constant weight in an oven at a temperature between 100 and 110C. (212 and 230F.), weigh, and determine the net weight of gravel. The percentage of clay and silt shall be calculated from the formula: Percentage of Clay and Silt = Original weight weight after washing Original weight For a check on the results, evaporate the wash water to dryness and weigh the residue: 4. Test for Organic Matter. Organic matter in the silt is determined by the Colorimetric Test. Fill a 12 oz. prescription bottle to the 4J/2 oz. mark with the sand to be tested, then add 3 per cent, solution of sodium hydroxide until the bottle is filled to the 7 oz. mark. Allow mixture to stand over night and then examine color of liquid above sand. A very dark orange is objectionable, a dark brown or black color indicates that the sand is badly contaminated, while a white or light yellow color indicates that there is little organic impurity present. NOTE Proportionate amounts may be used and the test made in any clear glass container. 5. Strength Test of Mortars. A common test for sand is in a mortar briquette as indicated in the specifications below. Note that fine soft limestone dust from quarry screenings may cause failure in a structure, without showing defects in this test. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 99 FINE AGGREGATE FOR CLASS "A" CONCRETE Strength. Mortar composed of one (1) part, by weight, of Portland cement and three (3) parts, by weight, of sand* mixed in accordance with methods referred to in Page 84 shall have a tensile strength at the age of seven (7) and twenty-eight (28) days of not less than one hundred (100) per cent, of that developed by mortar of the same proportions and consistency, made of the same cement and standard Ottawa sand. In testing aggregates care should be exercised to avoid the removal of any coating on the grains, which may affect the strength; bank sands should not be dried before being made into mortar, but should contain natural moisture. The percentage of moisture may be determined upon a separate sample for correcting weight. From 10 to 40 per cent, more water may be required in mixing bank or artificial sands than for standard Ottawa sand to produce the same consistency. Experiment. Select 5 samples of sand to include Ottawa Sand; bank sand; same sand washed; sand containing loam, limestone screenings. Apply the 4 tests and report which sands are suitaible for use in concrete. Has the strength test indicated the cleanness of the sand. Experiment E-3 WEIGHT OF AGGREGATES The weight per cubic foot gives a close estimate of the value of sand or other aggregate. Some general considerations must be understood in this experiment. Sizing. The weight per cubic foot of sand or of peb- bles of graded sizes would be greater than if of uniform 100 LABORATORY MANUAL OF TESTING MATERIALS size. Why? Likewise the weight per cubic foot of the mixture of the fine and coarse aggregate will be greater than of either alone. The volume produced by mixing a cubic foot of coarse aggregate with a cubic foot of fine aggregate will be less than 2 cu. ft., about 1%. Moisture. A film of water forces sand particles apart. Therefore dry sand swells when damp and weighs less per cubic foot. The amount of the swelling depends 25 0123456789 Moisture Per Cent by Weight FIG. 28. Voids in sand and gravel when moisture and unit weight are known. upon (a) the amount of water; and (6) the fineness of the sand. The maximum bulking effect in sand occurs at a "per cent, of water from 5 to 6 per cent, by weight, and is 30 per cent, for fine sand, 25 per cent, for medium sand, and 20 per cent, for coarse sand. Pebbles are only slightly affected. 1 per cent, of water may in- INSTRUCTIONS FOR PERFORMING tia&tWKiU$1t9' J * i i \ 101 crease the volume of fine sand 10 to 15 per cent. As the amount of water increases, filling the voids, a flood stage is reached and the sand return to its former dry volume. For Example Coarse Sand: dry, 107^ Ib. per cu. ft.; wet, with 3 per cent, of water, 94 Ib. per cu. ft. Medium Sand: dry, 99 J-^ Ib. per cu. ft; wet with 5 per cent, of water, 90 Ib. per cu. ft. Above cases are for compacted sand. When sand that has been in a rain storm is re-shoveled in a loose pile, the increase in volume may be % to J^ more. Evidently the test for weight per cubic foot must be standard as to moisture and compacting. DETERMINE THE WEIGHT PER CUBIC FOOT BY STANDARD ROD METHOD Measure Rod 100 c.c .................................. }-i inch X 18 inches. 1000 c.c ................................. y inch X 18 inches. H cu. ft ........................... , ..... y 2 inch X 18 inches. 1 cu. ft ................................. inch x 18 inches. The Rod method is operated as follows: Fill the measure one-third full of the aggregate, then, with a pointed iron rod of a prescribed size, jab or puddle the aggregate twenty-five times, distributing the strokes over the surface of the aggregate and avoiding penetrat- ing through the layer of aggregate so as to hit the bottom of the measure. Then add another one-third to the contents of the measure and again jab with the iron rod twenty-five times, penetrating only the last layer of aggregate placed in the measure. Next, fill the measure to overflowing and repeat the jabbing, then strike off the surplus sand with the iron rod and weigh. .102 'MANUAL OF TESTING MATERIALS THE PROPOSED TENTATIVE TEST FOR UNIT WEIGHT OF AGGREGATES, AMER. Sot. FOR TESTING MATERIALS 1920 Measures. The measure shall be of metal, preferably machined to accurate dimensions on the inside, cylindri- cal in form, watertight, and of sufficient rigidity to retain its form under rough usage, with top and bottom true and even, and preferably provided with handles. The measure shall be of Ko> % or 1 cu. ft. capacity, depending on the maximum diameter of the coarsest particles in the aggregate, and shall be of the following dimensions : Capacity, cu. ft. Inside diameter, in. Inside neight, in. Minimum thickness of metal, U.S. gage Diameter of largest particles of aggregate, in. Ko 6 00 6 10 No. 11 Under ^ y 2 10.00 11.00 No. 8 Under 1> i 14.00 11.23 No. 5 Over iy 2 Tamping Rod. The tamping rod shall be a straight metal rod % m - m diameter and 18 in. long, with one end tapered for a distance of 1 in. to a blunt bullet-shape point. Report the weight per cubic foot of the several sands provided by Instructor to include : Medium Sand: (a) dry, (6) with 5 per cent, water; Ottawa Sand; Mixed fine and coarse gravel aggregate; bank run gravel; crushed stone. If the specific gravity and voids of these have been determined by previous experiments, report the extent to which these weights are a measure of the voids. Problems. The Air Dry Sand, (a) is bought by the ton to be used in a 1-2-4 concrete proportioned by INSTRUCTIONS FOR PERFORMING EXPERIMENTS 103 volume. It becomes damp through exposure as in (6). Report the additional amount of sand (6) that should be used in mixing the concrete. Freight charges are paid for sand by the ton. What would be the proportionate amounts of freight charges on a car load of sand (a) dry and (6) damp with 5 per cent, water. Experiment E-4 THE SPECIFIC GRAVITY OF VARIOUS MATERIALS USED AS AN AGGREGATE IN CONCRETE Object. The object of this test is to determine the specific gravity of the various materials used as an aggre- gate in concrete. References. Taylor & Thompson, pages 122 to 123. Concrete Engineer's Handbook Hool & Johnson, p. 25. Materials. The following materials will be used: sand or gravel, stone. A porous material should first be moistened to fill the pores and the surfaces of the par- ticles be dried by means of blotting paper. A correction for the weight of absorbed moisture can be made by dry- ing the material in an oven. American Society for Testing Materials Standard Tests are as follows : 1. Fine Aggregates. (a) Le Chatelier Test using approx. 64 g. of mate- rial as in test for cement except that liquid may be water or kerosene. (6) Jackson Test using about 55 g. of material in the following apparatus : The determination shall be made with a Jackson specific gravity apparatus, which shall consist of a burette, with graduations reading to 0.01 in specific 104 LABORATORY MANUAL OF TESTING MATERIALS gravity, about 23 cm. (9 in.) long and with an inside diameter of about 0.6 cm. (0.25 in.), which shall be con- nected with a glass bulb approximately 13 cm. (5.5 in.) long and 4.5 cm. (1.75 in.) in diameter, the glass bulb being of such size that from a mark on the neck at the top to a mark on the burette just below the bulb, the capacity is exactly 180 c.c. (6.09 liquid oz.); and an Erlenmeyer flask, which shall contain a hollow ground- glass stopper having the neck of the same bore as the burette, and shall have a capacity of exactly 200 c.c. (6.76 oz.) up to the graduation on the neck of the stopper. 2. Coarse Aggregates. The apparent specific gravity shall be determined in the following manner : 1. The sample, weighing 1000 g. and composed of pieces approximately cubical or spherical in shape and retained on a screen having 1.27-cm. (J^-in.) circular openings, shall be dried to constant weight at a tempera- ture between 100 and 110C. (212 and 230F.), cooled, and weighed to the nearest 0.5 g. Record this weight as weight A. In the case of homogeneous material, the smallest particles in the sample may be retained on a screen having lj^-in. circular openings. 2. Immerse the sample in water for 24 hours, surface- dry individual pieces with aid of a towel or blotting paper, and weigh. Record this weight as weight B. 3. Place the sample in a wire basket of approximately j/4-in. mesh, and about 12.7 cm. (5 in.) square and 10.3 cm. (4 in.) deep, suspend in water 1 from center of scale pan, and weigh. Record the difference between this weight and the weight of the empty basket suspended in 1 The basket may be conveniently suspended by means of a fine wire hung from a hook shaped in the form of a question mark with the top resting on the center of the scale pan. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 105 water as weight C. (Weight of saturated sample im- mersed in water.) 4. The apparent specific gravity shall be calculated by dividing the weight of the dry sample (A) by the differ- ence between the weights of the saturated sample in ai r (B) and in water (C), as follows: A Apparent Specific Gravity = p _ /v 5. Attention is called to the distinction between appar- ent specific gravity and true specific gravity. Apparent specific gravity includes the voids in the specimen and is therefore always less than or equal to, but never greater than the true specific gravity of the material. APPROXIMATE METHOD. Weigh graduate and fill half full of water and weigh again, being careful to see that weight of water and volume check. Add an equal volume of the dry aggregate after weighing, and note the exact rise of the water level. Let W = weight of material, and G weight of water displaced. Then specific gravity of the W material = S = -~- if metric units are employed. Report should be in standard form. Experiment E-5 DETERMINATION OF VOIDS IN AGGREGATES References. Johnson's Materials of Construction, 5th Ed. p. 409, 417. Taylor & Thompson, 5th Ed. p. 181. Hool & Johnson, pages 25, 26, 27. The voids in an aggregate are the interstices between the particles. The total volume of hollow spaces constitute the abso- lute voids. The total volume of hollow spaces minus 106 LABORATORY MANUAL OF TESTING MATERIALS volume occupied by moisture constitute the air filled voids. Material. Any aggregate, usually sand, gravel or broken stone, thoroughly dried. Special Apparatus. For coarse materials: Use a vessel which is water tight and capacity is at least J^ cu. ft. Volume of water may be determined by weighing. Fbr finer materials: Use a 1000 c.c. graduate or 500 c.c. graduate if very fine materials are being measured. Vol- ume of water may be either measured or weighed. Procedure. (a) Determination of Voids by Direct Measurements.- In this method determine a known volume (varies with size, being larger for coarser sizes) of aggregate in the state in which the percentage of voids is required, i.e., loose, shaken or packed. The method of determining the volume of hollow spaces varies with the character and size of particles. COARSE AGGREGATE (contains no particles under Y in.) . Pour water directly into the aggregate till the voids are filled, the volume of the water poured in equals the volume of the voids. AGGREGATE CONTAINING PARTICLES UNDER M-IN. DIAMETER. Either introduce the water slowly from the bottom by means of a special apparatus, thus keeping out entrained air or pour a known volume of aggregate slowly into a known volume of water, noting the rise in level of water. The last two methods are not exact inasmuch as they allow some entrained air, but they will be found sufficiently accurate for practical purposes. (6) Determination of Voids by Specific Gravity Method. In this method the apparent specific gravity must be known or be determined as in Experiment E-4. Knowing the specific gravity of the aggregate, the INSTRUCTIONS FOR PERFORMING EXPERIMENTS 107 weight of a cubic foot of the solid material may be determined. Then determine the weight of a known volume of the aggregate usually in pounds per cubic foot as determined in Experiment E-3) in the state in which the percentage of voids is required, that is, loose, shaken or packed. From these weights the percentage of voids may be figured. Experiment E-6 EFFECT OF MOISTURE IN AGGREGATES ON PER CENT. OF VOIDS Object. The object of this test is to determine the effect of moisture on concrete aggregates with respect to the per cent, of voids. References. Taylor and Thompson, pages 137-140. Proc. Am. Soc. T. M. Vol. 20. Hool and Johnson, page 26. Material. The following materials will be used: Fine sand, coarse sand, gravel. Apparatus. 1000 c.c. graduate, 100 c.c. graduate, metric scale, pan. Method. Weigh a large 1000 c.c. graduate flask and fill half full of the dry material to be tested). Record the weight and the level of the material. Pour dry material into a pan and add 2 per cent, (by weight) of water to dry sand, and agitate thoroughly. Return dampened material to flask. Shake well and uniformly (one batch no more than the others) and record the new level of the sand. Add water in like increments of 2 per cent, until the material is thoroughly saturated, recording the new level after each addition of water. This determination may be made using the apparatus and methods as in E-3. Note how sand feels to the touch at different per cents, of moisture. 108 LABORATORY MANUAL OF TESTING MATERIALS Curves. Show by curves the relation between per cent, moisture and weight per cubic foot. Show also the relation between per cent, voids and per cent, moisture. Calculations. Assume specific gravity equal to 2.65, calculate per cent, absolute voids, per cent, air voids, weight per cubic foot for each per cent, of moisture. Report should be in regular form. Experiment No. E-7 STUDY OF SIEVES The results of sieving tests will not be comparable and specifications cannot be applied properly unless the standard sieves present the same spacing and diameter of wires. The commercial numbers designating the sieves are approximately the number of meshes per linear inch. There are three standard series in use at the present time. I. Tyler Series EACH OPENING DOUBLE THE NEXT LOWER No. or size Size of clear opening, in. Diameter of wire, in. 200 0.0029 0.0021 100 0.0058 0.0042 48 0.011G 0.0092 28 0.0232 0.0125 14 0.0460 0.0250 8 0.0930 0.0320 4 0.1850 0.0650 % 0.3700 0.0920 H 0.7500 0.1350 i; 1 . 5000 INSTRUCTIONS FOR PERFORMING EXPERIMENTS 109 II. The A. S. T. M. Standards SEE A. S. T. M. 1916 D-7-16 No. or size j Size of clear opening, in. Diameter of wire, in. 100 . 0055 0.0046 80 0.0067 0.0059 50 0.0114 0.0083 40 0.0142 0.0102 30 0.0197 0.0130 20 . 0335 0.0153 10 0.0790 0.0220 In sieving observe the following directions: Aggregate should be dry. Use 100, 250, 500, or 1000 grams of the sample since the results are then more easily turned into per cents. The samples to be tested and placed on the coarsest sieve, which is the top one in the nest. The sieving is complete when not more than 1 per cent, passes after one minute shaking. The results are plotted in a curve showing the per cents, retained in the various sieves. The most con- venient diagram is on the logarithmic scale. Sieve Analysis of Aggregates. A well graded aggre- gate contains particles of different sizes. Specifications prescribe the amounts of the various sizes of aggregates entering into a desired concrete. Experiment E-8 SIEVE ANALYSIS OF AGGREGATES The experiment gives graphically the gradations of sizes in an aggregate and by comparisons with a theoretical ideal aggregate the improvement of the aggregate may be known. 110 LABORATORY MANUAL OF TESTING MATERIALS Reference. Trans. American Society Civil Eng'rs, Vol. LIX, p. 90. Proc. Amer. Concrete Institute, 1917 pages 432 and 440. Concrete Eng'rs Handbook, Hool and Johnson, page 23. Engineering Record, Jan. 8, 1916. Material. Gravel and sand or broken stone with screenings, or stone and sand, well dried. Apparatus. Any standard sieves or screens may be used. The clear opening in inches must be known. The Amer. Soc. for testing materials prescribes circular openings for sizes y in. and larger. Procedure. A representative sample of the aggre- gate should be chosen weighing 1000 or 2000 gram. The coarser the aggregate, the larger should be the size of the original sample. The sample should be separated into its sizes by sieving, beginning with the largest sieves. The amount remaining on each sieve after five minutes, shaking should be weighed, also the amount passing the finest sieve. If the sum of these is not equal to the original weight, distribute the error proportionately. Note the actual size of the largest particle in the sample. Computations/ Plot a diagram with per cents, pass- ing the sieve as ordinates and size of mesh of the differ- ent sieves as abscissae. Plot also on this diagram, curves representing the specifications in Appendix II; and also a curve de- scribed as follows : The curve starts upon and is tangent to the zero alxis of percentages a't 7 per cent., and runs as an ellipse to a point on a vertical ordinate whose value represents a size about one-tenth of the diameter of the largest particle, and thence by a tangent straight line INSTRUCTIONS FOR PERFORMING EXPERIMENTS 111 to the 100 per cent, point on the ordinate of largest size of particle in the sample. NOTE. This latter curve is Fuller's Maximum Density Curve and contains also the cement in an assumed proportion. The equation for the ellipse is : (y - 7) 2 = ~(2a* - * 2 ) b a For stone and screenings 29.4-j-2.2Z) 0.055+0.147) For gravel and sand 26.4+1.3D 0.04 +0.1 6D For stone and sand 28.5-fl.3D 0.04 +0.16D NOTE. The above constants vary with the different materials which may be used in concrete constructions, and to be strictly accurate must be determined for each material. However, these values may be considered average and used as such may be considered accurate enough for practical purposes. Discussion of Results. In what sizes of particles is the aggregate deficient? How may this be remedied in a practical way? If the aggregate should be screened into two or more parts and these recombined in new proportions, indicate on what sieves to screen, and' the new proportions of each size to use. Give the proportions for an assumed concrete. INFORMATION YIELD OF CONCRETE AND QUANTITIES REQUIRED The volume of mixed concrete is approximately two- thirds of the total volume of the separate cement, sand and coarse aggregate. The volumetric shrinkage of 112 LABORATORY MANUAL OF TESTING MATERIALS sand and gravel when mixed together is about 15 per cent. These are rough approximates. The actual shrinkage will depend upon the character and sizing of the aggregate, consistency, richness of mix, etc. Fuller's Rule. Fuller's rule is a simple rule advanced by W. B. Fuller as follows: Barrels of cement per cubic yard of concrete = 10.5 C+S+G Number of cubic yards of sand = r . eyTTT X S Number of cubic yards of coarse aggregate L55 XG C+S+G Where C = number of parts of Cement. S = number of parts of Sand. G = number of parts of Coarse Aggregate. Thus for a 1 :2 :4 mix Bbls. of Cement = -= -7^7-7 = ^=1.50 i -f" -\ t Cubic Yards of Sand = -y- X 2 = 0.45 This rifle is approximate. The sizing of the different aggregates is not considered. Approximate amounts of Materials required for 1 cu. yd. of concrete. Proportion Cement, bbl. Sand, cu. yd. 1 Gravel or stone, cu. yd. 1:2:4 1.50 0.45 0.89 1:2.^:5 1 . 24 . 46 0.92 1:3:6 1.05 0.47 0.93 1:4:8 0.81 0.48 0.96 INSTRUCTIONS FOR PERFORMING EXPERIMENTS 113 On account of settlement of stone in transit, from 8 to 12 per cent., it is usual to order it by the ton. Weight of broken stone at the crusher is : for limestone, 2300 - 2600 Ib. per yd; for trap 2400 - 2700 Ib. per yd. Extensive tables will be found in " Concrete, Plain and Reinforced" by Taylor and Thompson, pages 213 to 217. Caution. The Aberthaw Construction Company re- marks that on account of waste on the job, the direct use of these tables will result in a shortage of material. The Company estimates the same amount of sand and coarse aggregate for 1:2:4 concrete as for 1:1:2, varying only the cement. Thus for 1 yd. of concrete. Proportion Cement, bbl. Sand, cu. yd. Stone, tons 1:2> 2 :5 1.36 0.50 1.30 1:2:4 1.66 0.50 1.30 1:13^:3 2.00 0.50 1.30 1:1:2 2.86 0.50 1.30 1.3 tons of broken limestone is approximately 1 yd. Experiment E-9 HAND MIXING OF CONCRETE Hand-mixed concrete is not under so good a control as machine-mixed concrete and, therefore, not so uniform. The student should learn the appearance and behavior of well mixed concrete with respect to consistency, uniform- ity, harshness, etc. The following directions from the Manual of the Ameri- can Railway Engineering Association should be carried out. First, however, determine in advance the amount 114 LABORATORY MANUAL OF TESTING MATERIALS of material needed and the proper consistency. (See Exper. No. E-ll, E-16, E-17 or F-2). " When it is necessary to mix by hand, the mixing shall be on a watertight platform of sufficient size to accommodate men and materials for the progressive and rapid mixing of at least two batches of concrete at the same time. Batches shall riot exceed J^ cu. yd. each. The mixing shall be done as follows: the fine aggregates shall be spread evenly upon the platform, then the cement upon the fine aggregates, and these mixed thoroughly until of an even color. The water necessary to mix a thin mortar shall then be added and the mortar spread again. The coarse aggregates, which, if dry, shall first be thoroughly wetted, shall then be added to the mortar. The mass shall then be turned with shovels or hoes until thoroughly mixed and all the aggregates covered with mortar. Or, at the option of the Engineer, the coarse aggregates may be added before, instead of after, adding the water." Notice that a concrete that appears dry at first will become easily flowing after longer mixing. If the concrete works harsh and the aggregate tends to sepa- rate, more cement or more fine sand is needed. NOTE. (1) Does free water appears when the mass is struck with a shovel. (2) At what angle with the horizontal will the concrete flow off the shovel. (3) If the concrete will hold a level surface in a wheelbarrow while the aggregate does not sink below the surface. (4) If the concrete quakes while it is being tamped to position. See that the tools are cleaned after use. A convenient method for mixing concrete by one man is as follows: The materials are mixed dry in a mortar box with high sides and a sloping end. With the hoe draw the dry materials toward the sloping end and supply water as INSTRUCTIONS FOR PERFOHM1NG EXPERIMENTS 115 needed, mixing a small batch of concrete thoroughly. When the batch has been used, another small batch is mixed in the same manner. Experiment E-10 MIXING CONCRETE BY MACHINE MIXER References.- Johnson's Materials of Construction, 5th Ed. pp. 439-441. American Concrete Institute Proceedings. Final Report of Joint Committee, Proc. A.S.T.M., 1917, p. 219. Obtain catalogue of type of mixer under operation and study design and operation of the machine. Check the following: Type: batch; continuous; Discharge: tilting, spout. Loading: state method. Shape of Drum, Arrange- ment of Interior Blades. Control. Speed of Drum Recom- mended. Movement of Concrete in Mixer. Measurement of Water. Time. Condition of Blades. Cleanness of Interior. Observe action of mixer and report following: Time Required to Discharge. Does Mixer Scatter Con- crete in Discharging? Proportion of Drum Capacity filled with Concrete, Time of Mixing. Water, Gallon per Bag of Cement. Uniformity of Mixing. What is the remedy when the mix separates or works too harsh. Output of mixer in cubic yards per hour. In mixing with batch machines, it is desirable to admit the sand, cement and stone in the order named a'nd mix dry for at least 10 or 15 seconds. The water should then be rapidly added and the mixing continued for at least one and one half minutes. For machines of two or more cubic yards capacity the minimum time of mixing should be two minutes. The speed of rotation 116 LABORATORY MANUAL OF TKSTING MATERIALS should be approx. 16 r.p.m. A speed at the periphery of the drum of about 200 ft. per minute is a general average for different types of mixers. Experiment E-ll AMOUNT OF WATER REQUIRED FOR MIXING Cement and water form a paste that binds the aggre- gate together and lubricates the aggregate to permit thorough mixing. An excess of water unduly dilutes and weakens the cement paste. Therefore, the minimum amount of water should be used that will give the re- quired work ability, mobility, or consistency to the con- crete. This consistency is kept constant on any one job but varies with the job. A thin wall with steel rein- forcements requires a wet concrete; concrete road, a medium concrete; sidewalk base, a dry concrete. The richer the mix, the more water required (22 per cent, by weight) to hydrate the cement. The amount of water in concrete is best expressed as the volume of water relation to the volume of cement. A volume, RULES FOR USUAL CASES OF USUAL AGGREGATES Kind of work Mix Gallons of water per bag of cement Slump test, in. Relative con- sistency 1-2-3 tamped concrete 123 concrete road Work Work S^'-G 5-G .0 10 1-2-3 reinforced concrete . . . Work 8-10 .25 1-2-4 tamped concrete 1-2-4 concrete road .Work Work 6 -G.H 5-6 .0 .10 1-2-4 reinforced concrete . . . Work 73^-8 8-10 .25 ratio of 0.8, is 0.8 cu. ft. of water to 1 cu. ft. of packed cement, i.e., nearly 6.4 gal. per bag of cement. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 117 The water absorbed in a porous aggregate, and the moisture in an aggregate that has been exposed to the weather, must be added to or subtracted from the above table. The finer the aggregate the more water is required to wet the surface of the particles. For instance, fine sand requires more water than coarse sand and, therefore, the cement must be increased if the same strength of paste is expected. METHODS OF MEASURING CONSISTENCY Such methods are not well standardized. Experiment/ Determine the amount of water re- quired to bring about a consistency, described below, of a 1-2-3 mix, using a local aggregate from the field. Consistency. The consistency of the concrete shall be such that when a cylinder 6 in. in diameter and 12 in. in length is filled with concrete and tamped until all voids are filled and a slight film of mortar appears on the sur- face and the cylinder then removed, the vertical settle- ment or "slump" of the concrete shall not exceed 2 in. when a mechanical finishing machine is used, nor more than 4 in. when the finishing is done by other methods permitted in these specifications. Consistency is usually judged by the general behavior of the concrete but sometimes tests are specified. Description of Slump Tests/ (a) By the Slump Test development of Abrams, which is thus performed. Mix the concrete thoroughly, adding the estimated amount of water. Tamp the concrete into a galvanized iron mold which is a cylinder 6 in. in diameter and 12 in. high. The cylinder is filled in two layers. Each layer is tamped for 40 strokes with a % in. round steel rod. 118 LABORATORY MANUAL OF TESTING MATERIALS Then draw the mold up, off the specimen, and note how much the specimen shortens or slumps in height. The consistency is expressed by the slump. Consist- ency = 1.0, slump is % to 1 in. Consistency = 1.10, slump is 5 to 6 in. Consistency = 1.25, slump is 8 to 10 in. This test applies to sands and gravels rather than to sand and broken stone. It is more reliable for wet mixes. (b) The Roman Cone Test for Consistency. In place of the cylinder a truncated cone is used, 8 in. diameter of base, 4 in. diameter of top and 12 in. high. The concrete shall be lightly tamped with a rod as it is placed in the mold, which when filled is to be immediately removed by means of handles on either side of the mold and the slump or settlement of the concrete noted. For concrete to be finished by a mechanical tamping machine the slump shall not be less than % in. nor to exceed 1 in. If the concrete is to be finished by hand methods the slump may be as much as \ l /2 in. Experience in deter- mining the consistency of concrete with the truncated cone apparatus would indicate the following " slumps:" Very dry consistency, no "slump;" fairly dry consistency, % to 1 in.; medium to wet consistencies, 1 to 4 in.; wet to sloppy consistencies, 4 to 8 in.; very sloppy consisten- cies, above 8 in. (c) Bureau of Standards: Jigging or Flow Table Test. The Jigging Test developed by the Bureau of Standards employs a table top raised vertically to a fixed height by means of a cam working at the end of a vertical shaft. A mass of concrete is molded in the center of the table in a sheet metal mold which has the shape of a hollow frus- tum of a cone. For aggregates up to 2 in. maximum size this cone has a height of 6 in., upper diameter of 8 in. and lower diameter of 12 in. For smaller aggregates a mold INSTRUCTIONS FOR PERFORMING EXPERIMENTS 119 having a height of 3 in., upper and lower diameter of 4 in. and 6 in. respectively may be used. After molding with as little tamping as is needed to fill the form, it is with- drawn and the table top is raised and dropped 15 times through J<2 inch after which the new diameter of the mass is measured. Usually the mass flattens and spreads con- centrically. Two diameters at right angles, the long and the short if difference is apparent, are measured by means of a proportional caliper which is so graduated that the sum of the two readings gives directly the " relative flowability," which may be expressed as the new diameter, divided by the old, multiplied by 100. Using a mass of the size and shape described above we find that a flowability of 180 is probably as stiff a con- crete as can be chuted and placed for reinforced concrete work in practice. A flowability of 240 is probably as great as is ever needed or should ever be permitted since the addition of more mixing water may result in excessive segregation. ARTICLE 6 PROPORTIONING MORTARS AND CONCRETES Information -12 Theory of Proportioning Concrete A critical study of methods of proportioning concrete is at present (1920) under way. The problem may be thus stated: For construction: Given Conditions. 1. The strength. 2. The consist- ency. 3. The exp'ected aggregate, (which may vary in sizing of particles). 120 LABORATORY MANUAL OF TESTING MATERIALS Factors to be Adjusted.-!. The amount of cement. 2. The amount of water. 3. The relative proportions of fine and coarse aggregate. 1. The usual practice is to specify the arbitrary mix of 1-1^-3, 1-2-3, 1-2-4, 1-3-6, thus decreasing the proportion of cement as a weaker concrete is desired. The sizes of the aggregates are specified in advance. 2. Formerly a rough idea of the mix was obtained from the measured voids in the aggregate. Void determinations are subject to so many errors that this method is not used. 3. The method of volumetric synthesis uses trialmixtures. That mix is selected which will produce the densest concrete, i.e., one which will yield the least volume in relation to the quantities entering into the mix. 4. Proportioning by adjusting the relative amounts of the particles of different sizes to follow the distribu- tion indicated by an ideal curve, as for instance an ellipse. See Experiment No. E-14. 5. Proportioning gravel concrete by increasing the cement when the per cent, of sand in the aggregate increases. Deposits of gravel necessarily vary in rela- tive amounts of sand and pebbles. Usually there is an excess of sand which may all be used, if a richer mix is specified. Crum's Method (see Am. Soc. T.M.) gives the amount of cement to produce a concrete of standard quality. The amount of sand and its weight must be measured. (See Table Rec. by Crum, Amer. Soc. for Test Mat. 1919, pp. 462.) 6. Proportioning by Surface Area, Edwards and Young, (see Proc. 1918 A.S.T.M.) indicate that the surface area of the aggregate is the most important determining factor in the proportioning. The cement paste must cover the surface of the particles. The surface area is actually INSTRUCTIONS FOE PERFORMING EXPERIMENTS 121 calculated, for example 700 sq. ft. per 100 Ib. of aggregate. An amount of cement is supplied to fit the job, thus for a first class concrete 2J Ib. of cement for each 100 sq. ft. of surface, or in this case, 7J^ Ib. cement for 100 Ib. of aggregate, or roughly 0.186 of cement per 100 Ib. of aggregate, or roughly 1 :4.6. For details of this process see Experiment No. 16. 7. Proportioning by Fineness Modulus Abrams (Bul- letin No. 1. Structural Materials Research Laboratory, Lewis Institute, Chicago) discovers that a certain grada- tion of aggregate accompanies the maximum strength. The gradation is expressed by the Fineness Modulus. The Fineness Modulus is calculated thus Sieve a sample of the aggregate through the following set of Tyler sieves: \Y 2 , %, %, Nos. 4, 8, 14, 28, 48, 100. Add the percentages retained on the sieves and divide by 100. The Fineness Modulus is an expression of the area under a curve representing the sieve test. Evidently a number of curves, sizings of fine and coarse aggregate rather than one ideal curve, will produce a given Fineness Modulus, and therefore a given strength. If the Fineness Modulus and water-ratio are kept con- stant, a constant strength will result. But if the con- sistency is changed by the addition of water, the cement must be increased to preserve constant the water-ratio. See Experiment on Fineness Modulus, E-17. Experiment E-13 MIXTURE- OF FINE AND COARSE MATERIAL Purpose.- The purpose of this experiment is to de- termine the increase in volume in an aggregate caused by the addition of a given volume of a finer material. References. Tayler & Thompson, Concrete, Plain and Reinforced,, 1907, Chapter VI, p. 10. 122 LABORATORY MANUAL OF TESTING MATERIALS Baker's Masonry Construction, 1910, Paragraphs 297 to 300. Special Apparatus. For fine materials. A 500 c.c. graduate. Scales for weighing with gram weights. A small wood tamper. For coarse materials. An iron vessel (an 8-in. pipe 1 ft. long with one end closed water tight is a convenient appara- tus). A steel scale or other means of measuring con- tents of vessel. \ Method of Test. The coarser material should be in the condition in which it is being used on the work. A given volume of this should be determined by tamping into the measuring vessel in small quantities. It should then be emptied out upon a non-absorbent surface or pan and to it the desired volume of finer material be added and the whole thoroughly mixed. The mixed materials should then be tamped back into the measuring vessel and the increase in volume determined. Report. The report should be in the standard form. What is the significance of the results of these tests in the proportioning of concrete materials? Experiment E-14 PROPORTIONING CONCRETE BY METHOD OF SIEVE ANALYSIS The cases which may arise are in general, the folio wing: CASE 1. A single aggregate is separated into two or more sizes and re-combined. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 123 CASE 2. Two or more aggregates are to be combined. (a) When their analysis curves meet, but do not overlap. (6) When their analysis curves wholly or partly overlap. Procedure. Case 1. Perform the operation of me- chanical sieving upon the aggregate and draw sieve analysis curve together with curve for ideal mixture as directed in Experiment E-8. Study the curves to decide how many and what sizes to screen the aggregate into so that the re-combination of parts may be as near as practicable to the ideal curve. NOTE. It is not. practicable in most cases, on account of extra expense, to screen into more then three sizes of aggregate. Now treat each size of aggregate as a complete sample and re-draw its curve to the original scale. This is most easily done by manipulation of values by slide rule. See Fig. 28a. There are now represented on diagram sheet, two or more aggregates, as the case may be, whose curves do not overlap in sizes, and drawn to the same scale. These should be combined according to the demands of the ideal curve for the mixture. Give the percentages of each to use and draw the combined curve. For methods, see Reinforced Concrete Construction, Vol. I by Hool, p. 7. or Concrete, Plain and Reinforced, p. 190-200 by Taylor and Thompson. Give the proportions by weight for an assumed con- crete, i.e., 1 to x concrete. CASE 2. (a) Perform the operations and draw the curves as in Experiment E-8. The curves of the dif- ferent aggregates should be drawn to the same scale on 124 LABORATORY MANUAL OF TESTING MATERIALS INSTRUCTIONS FOB PERFORMING EXPERIMENTS 125 the same sheet. The Ideal curve for the mixture should be drawn from the 100 per cent, point on the ordinate of the largest size of particle and the coarsest aggregate. The method of combining the different aggregates is given in Case 1. (6) Perform the operations and draw the curves as directed in E-8 and (a) above. For method of combination and drawing combined curves see Concrete, Plain and Reinforced, by Taylor and Thompson. ILLUSTRATION OF METHOD or PROPORTIONING CON- CRETE BY SIEVE ANALYSIS In Fig. 28 (a) the following curves are shown: Curve A represents the ideal curve of maximum den- sity for a mixture of cement, sand and gravel where the size of the largest particle is 1J^ in. Curve B represents an ordinary "Run of Bank" sample of gravel in which the size of the largest particle is 1J in. Curve C represents a 1 to 5 (by weight) mixture of cement and gravel as shown in Curve B. Curve D represents the sand finer than Y in. in the Run of Bank gravel, plotted to the same scale. Curve E represents the gravel coarser than % in. in the "Run of Bank" as represented by Curve B and plotted to the same scale. Curve F represents a 1 to 5 (by weight) mixture of cement and sand as represented by Curve D and gravel as represented by Curve E. Any mixture of cement and the run of bank gravel as represented by Curve B, will be far from the ideal maxi- mum density mixture as represented by Curve A. If, however, the run of bank is screened into two parts, i.e., 126 LABORATORY MANUAL OF TESTING MATERIALS sand finer than J4 m - represented by Curve D and gravel coarser than y in. represented by Curve E, the mixture of cement plus aggregate may be made to conform closely to the ideal. The ratio of cement to aggregate must be assumed in any case and depends upon the quality of concrete desired . In Fig. 28a the ratio of cement to aggre- gate was assumed to be 1 to 5 by weight. In any mixture of 1 to 5 concrete the cement is 1 divided by 6 equals 16.6 per cent, by weight of the whole. The ideal calls for 37 per cent, finer (equals sand plus cement) than a J in. size and 63 per cent, coarser than J4 m - size. To give a still closer approach to the ideal 35 per cent, finer than J4 in. and 65 per cent, coarser than J in. were taken. The mixture, to conform closely to the ideal, will have then 35 per cent, by weight finer than Y in. and this will be made up of sand plus cement, and since the cement in a 1 to 5 mixture is 16.6 per cent, of the whole, then 35 16.6 = 18.4 per cent, is the per cent, by weight of sand smaller than Y in. in the mixture. The pro- portions of cement, sand, and gravel for the total mixture of 1 to 5 concrete are then 16.6 per cent, cement, 18.4 per cent, sand as represented by Curve D and 65 per cent, gravel as represented by Curve E. This corresponds to the proportion by weight of 1 : 1.1 : 3.9. The propor- tions by volume as used on the work will be determined from the unit weights of the materials. The bulking effect of moisture should be taken into account in this transformation of proportions. See Exp. E-3 and E-6. And the curve of the mixture (Curve F) is seen to con- form much closer to the ideal maximum density curve than a 1 to 5 mixture (Curve C) of cement and the original "Bank Run" gravel. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 127 Experiment E-15 STRENGTH AND DENSITY The object of this test is to determine which of two or more sands will give the denser, and the stronger, mortar in any given proportion. References. Natl. Assoc. of Cement Users, Vol. II, p. 24. Taylor & Thompson, Concrete, Plain and Reinforced. Johnson's Materials of Construction, 5th Ed. p. 411- 413, 429. Hool & Johnson, Handbook, p. 68. Materials. Two or more sands or other fine aggre- gate to be used in concrete construction. The test should be made on a dry sample of the sand, but if sand as used in the work contains moisture, correction of the propor- tions found, must be made for the amount of moisture present. Method. The proportions of cement and sand should be such by dry weight as to give the desired proportion by moist volume, that is the proportions actually to be used on the work. This will of course have to be ascer- tained in any given case. A batch of ... grm. of the dry materials should be well mixed for about one minute in a clean shallow pan. An amount of clear water should be then added to give a plastic mortar and the whole well mixed for 4 minutes. The mortar should then be lightly tamped into a 500 c.c. graduate or any form of graduated yield apparatus with a light wood tamper. About 20 c.c. of the mixture should be introduced at a time. After allowing the mortar to settle for some time the volume of mortar should be read. 128 LABORATORY MANUAL OF TESTING MATERIALS The other sands should be treated in the same way using the same proportions by dry weight and enough water to give the same consistency. The sand which gives the least volume of mortar, i.e., which has the least volume of voids is the best sand pro- vided there is no other ingredient present to affect the strength and setting. If desired, strength test specimens may be molded from the resulting mortar in each case. The method of molding specimens should conform to the best practice as given in standard methods of testing cement. See Experiments D-6 and D-7. Tests should be made at end of 7 or 28 days. Report. The report should be in standard form. Experiment E-16 EXPERIMENT ON SURFACE AREA OF AGGREGATES References: Proceedings of Amer. Soc. for Testing Materials, Vol. 18, page 235 and Vol. 19, page 444. The surface area of aggregates is sometimes used as a measure of their value for concrete. A coarse sand, for example, has less surface area to be covered with cement paste, and requires less water for mobility than a fine sand of equal volume. Method of Determination of Surface Area. 1. Sieve a sample of gravel; determine its weight per cubic foot. Sieve it through the following Tyler sieves 1^2, %, %, No. 4, 8, 14, 28, 48, 100. 2. Count the number of particles per gram or fraction for extreme small sieves per ounce between the smaller intermediate sieves, and per pound between the larger sieves. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 129 3. Determine the specific gravity of the aggregate and calculate the weight of solid cubic inch. See Exp. E-4. 4. Calculate the number of particles required to form this solid volume and therefrom the average volume of one particle. 5. Assuming this volume to be a sphere, calculate its diameter and surface area, and total surface area of the particles per unit weight. 6. Express the result in square feet per 100 Ib. of aggregate between each sieve and for entire sample. The following formula may be conveniently used: = 236.1^/1 where A = Surface Area in square feet per 100 Ibs. S = Specific Gravity of material. N = Number of grains per gram in any size of separation. 7. Make graph with diameter of particle as abscissa and square feet per 100 Ib. as ordinate. If 3 Ib. of cement are to be used for every 100 sq. ft. of surface of aggregate, how many bags of cement will be used to a cubic yard of this mixed aggregate? With water ratio of 0.85, how many gallons of water per bag of cement? If the proportions are stated in terms of mixed aggregate, as 1 : 4.2, how can this be ex- pressed in terms of separate volumes of sand and coarse aggregate? The Hydro-Electric Commission of Ontario propor- tions concrete on the basis of surface area. (See Eng- ineering News-Record, Vol. 84, page 33.) 130 LABORATORY MANUAL OF TESTING MATERIALS Experiment No. E-17 EXPERIMENT ON FINENESS MODULUS The Fineness Modulus is used as an expression of that gradation of sizes of aggregates which will produce good concrete. A Fineness Modulus of 5)^ to 6 is favorable. With same aggregate as in Experiment No. E-16 on Surface Area, determine the Fineness Modulus, i.e., the sum of the per cents, retained on the sieves divided by 100. (1) Report Fineness Modulus of sand and pebbles separately and combined. (2) Report per cent, of sand and pebbles in mixture. (3) Check application of following formula. Fineness Modulus of mixed aggregate = F. M of sand x per cent, of sand + F.M. of pebbles x per cent, of pebbles. Work following numerical problems. (1) The F. M. of sand is 3.05, and of pebbles is 7.50. Required per cent, of sand to produce a mixed aggre- gate whose F. M. is 6.0. (2) When sand and pebbles are mixed the resulting volume will be about 0.86 of the total separate volumes, (a) a mix of 1^-2): 4 will be a proportion of 1 : 6X0.86 or 1 : 5.16 combined, (6) a mix of 1 :4.2 combined aggregate will be what? When expressed as separate 4 2 or loose volumes? -^ = 4.9 loose volumes. .ou The aggregate sieves to show 40 per cent, sand and 60 per cent, stone. Therefore 4.9X40 per cent. =1.96 sand 4.9X60 per cent. =2.94 sand, or approximately 1:2:3 INSTRUCTIONS FOR PERFORMING EXPERIMENTS 131 (3) Concrete for a road construction is specified to be mixed 1 : 2 : 3, that is 40 per cent, sand and 60 per cent, pebbles. The available sand is finer than the specifications allows. What should new proportions be for a concrete of equal strength, and the fine sand used? Tests on the aggregate show the following;: . F. M. fine sand =2.40 Weight Ib. per cu. ft. = 102 F. M. coarse sand =3.30 Weight Ib. per cu. ft. = 116 F. M. pebbles =7.25 Weight Ib. per cu. ft. = 112 Weight of mixed aggregate with coarse sand = 130 Ib. per cu. ft. Calculations. Real Mix =1 : (2+3) 0.86 = 1:4.3. F. M. of mixed aggregate (coarse sand) =3.30 X. 40+ 60X7.25 = 5.67 The F. M. of the aggregate with fine sand must also be 5.67. Per cent, fine sand = 7 05 _ 5 A 7 7726=230 Per cent, of pebbles = TTvT^.S per cent. The mix will be as before 1 : 4.3 mixed or 1 : 5 loose volumes. The proportions will be Sand 5 X .325 = 1.62 Pebbles 5X,67 = 3.38, or 1: 1.62: 3.38. We have thus added coarse material by adding more pebbles. This mix should be tested to see if it works properly on the job. Repeat this calculation for the material tested in this experiment. 132 LABORATORY MANUAL OF TESTING MATERIALS Article 7 TESTS OF CONCRETE AND OTHER BRITTLE MATERIALS Experiment F-l THE VALUE OF A SAND OK OTHER FINE AGGREGATE AS SHOWN BY STRENGTH TESTS Purpose. This test is to determine the strength of a natural sand mortar as compared with strength of a standard Ottawa Sand Mortar. References. Indiana State Highway Common Speci- fication in appendix, page 160. Material. Any sand or fine material used as a con- crete aggregate. This material should all pass a J^-in. sieve. The original moisture in the sand should be pres- ent if possible, in which case a correction for weights must be determined by drying a separate sample. The cement used should be a mixture in equal parts of several standard Portland cements. Method. In determining the strength, nine test specimens of standard Ottawa sand and cement in the proportion of 1 part cement by weight to 3 parts Ottawa sand, should be made in the regular way. See Experi- ment D-6 and D-7. The same number of specimens should be made using the sand under test. The correction for weight due to moisture should be made. This damp sand should first be thoroughly mixed with the required amount of cement until the whole is a uniform color. Water should then be added until the consistency is the same as that of the standard sand mortar. Care should be used in this determination. Test 3 at 72 hours, 3 at 7 days and 3 at 28 days age. Report the strength of each and the average of the three. INSTRUCTIONS FOR PERFORMING EXPERIMENTS Report. The report should be in standard form. The ratio of the strength of the test sand to that of the standard sand mortar should be noted. If the sand proves to be defective what tests should be made to ascertain the cause? Experiment F-2 (See also Exp. F-3) COMPRESSIVE STRENGTH OF CONCRETE The object of this experiment will be to determine the compressive strength of concrete. References. Hool & Johnson " Concrete Engineers Handbook." Baker's Masonry Construction, pp. 194 to 217. Material. Use broken stone (or gravel) up to 1% in. sand and Portland cement. Apparatus. Six cylindrical molds. Method of Making Test Specimens. Make three cylinders 8 in.XlG in. or 6 in.X!2 in., using one ^of the following proportions : 1 part cement 1^ parts sand 3 parts broken stone. 1 part cement 2 parts sand 4 parts broken stone. 1 part cement 3 parts sand 6 parts broken stone. 1 part cement 4 parts sand 8 parts broken stone. In computing amounts necessary use the rule shown on p. Ill, or obtained by methods shown in Experiments E-16 or E-17. For method of mixing, see Experiment E-9 or E-10. Tamp concrete in cylinders in layers of 4 in. A % in. diameter steel rod is recommended for rodding the con- 134 LABORATORY MANUAL OF TESTING MATERIALS crete into place. Carefully smooth off the top and make cylinder stand vertical. Be sure top and bottom bases are both perpendicular to axis of cylinder. Test in 7 or 28 days. For method of test see F-3 and F-4. Experiment F-3 COMPRESSION TEST BRITTLE MATERIALS The purposes of this experiment are : To obtain knowl- edge of the proper methods of testing materials in com- pression; of the crushing strength of such materials; and of the characteristic forms of fracture. Material. Three concrete cylinders, or three bricks, or terra cotta, or any building material in proper form for compression test. Preliminary. (1) Before testing any specimen care- fully measure its height and cross section. 2. When brick, stone, concrete, or cement specimens are to be tested they should be carefully bedded either with blotting paper or with plaster of Paris. (See Fig. 6.) To bed a specimen with plaster of Paris, have the testing machine balanced, and the head down so far that it will clear the specimen only about 1 in. or 2. Then mix some plaster of Paris and water to a very thick, creamy consistency. Spread a thin layer of this on paper placed upon the spherical bearing block of the machine and cover it with a piece of tough sized paper, upon which the specimen should then be placed. The paper is to keep the water of the plaster out of the specimen. Upon another similar piece of paper a similar pad of the plaster should be spread covered with another piece^of paper to form a pad, and the pad then placed upon^the specimen. The head of the machine should INSTRUCTIONS FOR PERFORMING EXPERIMENTS 135 then be run down rapidly until it presses upon the plas- ter sufficiently to cause it to flow, thus insuring a good bedding. With the trowels now fill up all the open spaces about the edges of the specimen near the faces of the machine. The surfaces of the specimen may be shellaced and the plaster of Paris applied directly to them. If it is riot desired to cap the specimen in the testing machine, oiled plate glass may be used to give a smooth plane bearing surface on the plaster of Paris. After letting the plaster set until hard, the specimen is ready to be com- pressed. Have the work inspected by the instructor before proceeding. Another method of capping specimens is as follows: Make a paste of neat cement or rich mortar at or before making the concrete and place the paste on the specimen after 2 or 3 hours has elapsed. This should then be covered by plate glass or other plane surface until the paste hardens. In the case of all materials see that the ends of the specimen admit of a good even bearing in the machine. The Test. Using the slowest speed available, now compress the specimen, meanwhile keeping the scale beam floating; and watch carefully the behavior of the specimen. Computation. Compute the stress in pounds per square inch at first crack, and at maximum load. Results. Load and crushing strength at first crack and at maximum load or failure, Sketch form of fracture. Comparison of results with standard values. See general form of report. 136 LABORATORY MANUAL OF TESTING MATERIALS Experiment F-4 COMPRESSION OF BRITTLE MATERIALS WITH DEFORMA- TION MEASUREMENT References. Walker on " Modulus of Elasticity of Concrete" Proceedings A.S.T.M Part II, 1919. Hool, Reinforced Concrete Vol. I. Object. In addition to determining the maximum strength in compression, as in other compression tests, it is intended in this experiment to find the strength at elastic limit, the modulus of elasticity, and the modulus of elastic resilience. Material. The material should be of a cylindrical form if possible. A gage length of at least 8 in. should be available. Apparatus. Compressometer reading to 0.0001 in. Operations in Testing. Proceed as in other compres- sion tests except that the load is applied in increments of pounds (about one-twentieth of the probable maxi- mum load) and the total amount of compression at each increment is measured by a compressometer. (Use slowest speed of the machine.) Computations. Plot points with load in pounds for ordinates and compression in inches for abscissae. Draw a straight line averging the points preceding the elastic limit, if any; and, tangent to this straight line, draw a smooth curve averaging the remaining points. Mark the points of maximum load and elastic limit, which latter is the point of tangency of the straight line and the smooth curve. Then draw a line through the origin par- allel to the straight line previously drawn through the plotted points. (Do not continue this line beyond elastic limit.) Mark the point of elastic limit, if any, on cor- rected line. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 137 The modulus of elasticity is calculated from the PI formula E = ^- where P and X are the load in pounds and r A compression in inches respectively, for any point on the corrected line; F is the square inches of cross-sectional area of the specimen, and / is the gage-length in inches. Consult above references for various methods of com- puting Mod. of Elasticity. The moduli of elastic resilience and of rupture-work are the work done on each cubic inch of material in deform- ing it up to the elastic limit and ultimate strength re- spectively. These moduli may be obtained from the curve of plotted points by multiplying the area under the curve up to the point considered by the scale value of each unit area of the coordinate paper or by computation from observed data. Experiment F-5 REINFORCED CONCRETE BEAM TEST NOTE. This experiment may be made to apply to column or slab tests by changing certain details as to shape and arrangement of specimen and reinforcement and also measurement of deformations. This experiment follows compressive strength test. The same proportions will prevail. The object of this test is to investigate the action of a reinforced concrete beam. Material. Same as in Experiment F-2 with the ad- dition of steel for reinforcement. Method of Making and Test. Make concrete as in Experiment F-2 only a little wetter. Place two taper- ing wooden plugs on bottom of forms under each rein- forcing rod and spaced 10 inches center to center in middle of length of beam. Wet forms and cover bot- 138 LABORATORY MANUAL OF TESTING MATERIALS toms of mold with about 1 in. of concrete, then place the rods in position. Ram and spade the concrete well about forms and rods. Level off the top and cover with damp cloth. Sprinkle every day for ten days. For compression measurements small iron plugs should be set flush with top of concrete, directly over the rein- forcement and spaced 10 inches center to center in the middle of the beam. Drill holes in the reinforcing and plugs as directed. The test will be under supervision of the instructor. Determine the load-deflection curve and stress in steel and concrete, if possible, by means of the Berry strain gage. Report will cover: 1. Description of materials, kind, brand, voids, strength of cement, etc. 2. Proportions. 3. Design of beam. 4. Per cent, of steel 5. Stresses in concrete and steel at first crack and maximum by formula, and by test. 6. Location of neutral axis. Experiment No. F-6 BOND STRENGTH OF STEEL IN CONCRETE Bond strength is the resistance to withdrawal offered by the surface of a steel bar embedded in concrete. At low loads this resistance arises from the adhesion between steel and the film of cement, as in case of a polished bar. When this is overcome, the roughness of surface intro- duces bearing and shearing resistance, as in case of a de- formed bar with shoulders. An ordinary plain bar with uneven surface is a partially deformed bar. Select 2 round rods 20 in. long and % in. in diameter from each of the following : cold drawn steel with smooth surface; ordianry plain reinforcing steel; deformed bar. Embed these in cylinders. Pull out the bars at age of INSTRUCTIONS FOR PERFORMING EXPERIMENTS 139 28 days, observing (1) stretch of bar, and (2) withdrawal from concrete at increasing loads. Draw curves of slip against bond stress per square inch of embedded surface. Report (1) bond stress at first slip, (2) maximum bond, (3) stress in bar at maxi- mum bond, and (4) number of diameters of length of embedment necessary to develop maximum strength of bar. Did the cylinder split? Did the bar reach its yield point? Consult references and report how the results would have varied with richer concrete and bars of square or oblong shape. Experiment No. F-7 TEST OF CONCRETE REINFORCING FABRIC Report on sample furnished the following: Weight per 100 sq. ft.; ultimate strength of metal; distribution of area of cross-section between longitudinal and trans- verse directions. Consult catalogue of manufacturer and determine uses for which this fabric is recommended. Report. See standard form p. 7. Experiment F-8 CROSS BENDING AND COMPRESSION TESTS OF BUILDING BRICK Reference. Tentative Specifications for Building Bricks. Proc. A.S.T.M., 1919, I. Purpose. The purpose of the tests is to determine the quality of various grades of building bricks. 140 LABORATORY MANUAL OP TESTING MATERIALS Materials. Various kinds and grades of building brick as assigned. At least five of each kind should be available for each test. The bricks should be dried to constant weight. Procedure. Transverse Test. Test flat-wise on a span of 7 in. with the load applied at midspan. Use standard apparatus. Determine maximum breaking load. Compression Test. Test half -brick on edge. 1" Cut the brick into halves with mason's chisel. 2. Apply coat of shellac to upper and lower edges and allow to dry. 3. Apply thin coat of plaster of paris mixed with water to the consistency of thick cream. 4. Apply oiled plate glass and allow to harden. 5. Test in compression using spherical bearing block. Determine the maximum breaking load. Report. Follow the standard form on p. 7, referring to the above reference for computations and specifications. Additional Reference: Bulletin No. Ill, Bureau of Standards. Article 8 TESTS OF ROAD MATERIALS Experiment G-l RATTLER TEST OF PAVING BRICK Purpose. To determine the effects of impact and abrasion in a standard rattler test. NOTE. Differentiate these effects in comparing differ- ent samples of brick. References.- Specifications of the American Society for Testing Materials, 1918, p. 549. Judson Roads INSTRUCTIONS FOR PERFORMING EXPERIMENTS and Pavements; Tillotson Paving and Paving Materi- als; Baker Roads and Pavements; Bryne Highway Construction. Specifications of N. B. M. A. Extract from standards of A.S.T.M., 1918, p. 555: "The number of bricks per test shall be ten for all brick of so-called "block size" whose dimensions fall between 8 and 9 in. in length, 3 and 3% in. in breadth, and 3% and 4}^ in. in thickness." NOTE.' Where brick of larger or smaller sizes than the dimensions given above for blocks are to be tested, the same number of brick per charge should be used, but allowance for the difference in size should be made in setting the limits for average and maximum rattler loss. Note any surface evidences of lamination. Select brick which are free from chipped corners and other defects. Apparatus. The standard rattler of the Amer. Soc. for Testing Materials shall be used. (See Standards 1918, of Amer. Soc. for Testing Materials, p. 551.) The abrasive charge shall consist of cast iron spheres of stand- ard composition and of two sizes. Ten large spheres 3.75 in. in diameter when new weighing approx. 7.5 Ib. each. The smaller spheres shall be 1.875 in. in di- ameter when new. The collective weight of the charge shall be as nearly 300 Ib. as possible. Procedure. Weigh and place the required number of bricks in the rattler. See that the shot makes up the re- quired weight for each size; if they do not, place an ad- ditional small shot in the rattler. Record the reading of the counter. Close the rattler and start. Note the rate which should be as near 30 r.p.m. as possible. Only one start and stop per test is generally acceptable. Results. The loss shall be calculated in percentage of 142 LABORATORY MANUAL OF TESTING MATERIALS the initial weight of the brick composing the charge. In weighing the rattled brick, any piece weighing less than 1 Ib. shall be rejected. Report should be in general form. Experiment G-2 ABSORPTION TEST Procedure. Place 5 rattled brick in dry kiln 48 hours and weigh each brick separately to nearest gram. Then place in water completely submerged for 48 hours. Place strips H X Y beneath the bricks and between them so that faces shall not be in contact. When re- moved from water, allow the water to drip from the surfaces for aboufc 2 minutes, then weigh separately to nearest gram. (Note: When rattled brick are not available, use half-brick.) Absorption. Subtract the weight of the dry bricks from the weight of the wet bricks. Find the per cent, of gain in weight, which is called the per cent, of absorption. See general form of report. Experiment G-3 ABRASION TEST OF ROCK FOR ROAD MATERIALS AND BALLAST This test is intended to determine the wearing value of road materials. References. 1918 Standards of American Society for Testing Materials, p. 623. Bulletin, No. 347, U. S., Dept. of Agriculture. Office of Public Roads. Materials. Any rock or like material used in road construction. At least 30 Ib. of the material should be available for a test. INSTRUCTIONS FOR PERFORMING EXPERIMENTS 143 Procedure. The material to be tested should be broken in pieces as nearly uniform as possible. There should be 50 pieces in the charge, the total weight of which shall be 5 kg. All test pieces shall be washed and thoroughly dried before testing. The charge is then placed in the Deval Abrasion machine and given 10,000 revolutions at the rate of 30 to 33 r.p.m. The Deval Abrasion machine consists of one or more hollow iron cylinders, closed at one end and furnished with a tightly fitting cover at the other. The cylinders are 20 cm. in diameter and 34 cm. in depth inside dimen- sions. They are mounted on a shaft at an angle of 30 with the axis of rotation of the shaft. At the end of 10,000 revolutions, the charge is removed and those particles retained on a Jf g-in. mesh sieve, are thoroughly washed and dried again. Computations. Compute the loss in per cent. Compute the French Coefficient of wear. The French Coefficient of wear for any material = 20 X 7j7 = i r = 7 - where W equals the per cent, of wear loss in weight under Jf g-in. in size per kilogram of rock used. Experiment G-4 CEMENTATION TEST OF ROCK OR GRAVEL OR MATERI- ALS OP LIKE NATURE This test is intended to determine the comparative value of dust from different rocks or gravels as a binder in the surface of roads. Materials. The materials consist of 1500 grm. of coarsely crushed rock broken to pass a J^-in. sieve or 1500 grm. of gravel as it comes from bank. 144 LABORATORY MANUAL OF TESTING MATERIALS Special Apparatus. A Ball Mill for grinding the materi- als. Cementation impact machine for testing briquettes. Procedure. Place 500 grm. of the rock together with 90 c.c. of water in the ball mill. The mill is then revolved at the rate of 30 revolutions per minute for two and one- half hours, the action of the chilled iron balls in the mill grinds the sample to a stiff dough. Place about 25 grm. of the dough in the cylindrical metal die for molding. The die is 25 mm. in diameter. By applying a load directly to the plunger of the die, run the plunger down to a maximum pressure of 132 kg. per square centimeter. This load is applied only for an instant and then released. Remove the briquette and measure the height, if it is not 25 mm. in height, the req- uisite amount of material should be added or subtracted to make the next briquette the required height. At least 5 briquettes should be made from each sample. These are allowed to dry in room air for 20 hours and dried in air of approximately 100C., for 4 hours. After cooling 20 minutes in a desiccator they should be tested in the impact machine. The briquette is placed directly on the anvil under the plunger. By placing a drop of shellac on the anvil under the briquette, it can be made to stay in its position. After adjusting the recording paper and needle, the motor is started. The mechanism is such that the briquette receives the blow of a 1 kg. hammer at the rate of 60 per minute. The number of blows it takes to break the specimen is recorded on the drum. The number of blows necessary to destroy the resilience of the briquette, so that no action is recorded on the drum, is taken as the cementing value of the specimen. There should be obtained an average of at least five speci- mens to fix the cementing value of the material. INSTRUCTIONS FOR PEKFOBMING EXPERIMENTS 145 Experiment G-5 HARDNESS TEST OF ROCK ROAD MATERIALS. Dorry Test This test indicates the comparative hardness of rocks as indicated by their ability to withstand an abrasive force. Special Apparatus. A diamond core drill for cutting out test pieces. A Dorry Abrasion Machine for testing hardness. Materials to be Tested. Any rock in pieces large enough so that cylinders 25 mm. in diameter and about 25 mm. in height may be cut from them. Procedure. Cut out specimens from rock by means of a diamond core drill. The ends may be squared by the diamond saw. At least two and preferably four speci- mens should be tested from each material. These specimens should be dried to a constant weight at 100C. Before placing in the machine they should bo weighed. After placing two specimens in the machine start the motor and allow to run for 1000 revolutions at 30 r.p.m. Reweigh the specimens and determine the loss. The operation is repeated with the specimen reversed. Calculations. Express the loss as a per cent, of the original dry weight. Compute the coefficient of hardness, by the formula: loss in grams 20 - -- HJ 146 LABORATORY MANUAL OF TESTING MATERIALS Experiment G-6 STANDARD TOUGHNESS TEST FOR ROAD ROCK In this connection, toughness of rock is taken to mean the power to resist fracture by impact. Special Apparatus. A core drill 1 in. in diameter for cutting specimens. An impact machine in which the anvil weighs 50 kg., the hammer weighs 2 kg., the intervening plunger weighs 1 kg. The plunger should bear upon the test piece with spherical surface of hardened steel having a radius of 1 cm. Materials. Quarry samples of rock from which test specimens are to be prepared shall measure at least 6 in. on a side and at least 4 in. in thickness, and when possible shall have the plane of structural weakness of the rock plainly marked thereon. Samples should be taken from freshly quarried material, and only from pieces which show no evidences of incipient fracture due to blasting or other causes. The samples should preferably be split from large pieces by the use of plugs and feathers and not by sledging. Commercial stone-block samples from which test specimens are to be prepared shall measure at least 3 in. on each edge. Specimens for test shall be cylinders prepared as described in Section 4, 25 mm. in height and from 24 to 25 mm. in diameter. Three test specimens shall con- stitute a test set. The ends of the specimen shall be plane surfaces at right angles to the axis of the cylinder. One set of specimens shall be drilled perpendicular and another parallel to the plane of structural weakness of the rock, if such plane is apparent. If a plane of structural weakness is not apparent, one set of specimens shall be INSTRUCTIONS FOR PERFORMING EXPERIMENTS 147 drilled at random. Specimens shall be drilled in a man- ner which will not subject the material to undue stresses and which will insure the specified dimensions. The ends of the cylinders may be sawed by means of a band or diamond saw, or in any other way which will not induce incipient fracture, but shall not be chipped or broken off with a hammer. After sawing, the ends of the specimens shall be ground plane with water and carborundum or emery on a cast-iron lap until the cylin- ders are 25 mm. in length. Procedure. At least three and preferably four or more specimens should be tested for each rock. These should be dried in a constant weight before testing. The specimen should be adjusted in the machine, so that the center of its upper surface is tangent to the spherical surface of plunger. The test shall consist of 1 cm. fall of the hammer for the first blow and an increased fall of 1 cm. for each succeeding blow, till the piece is ruptured. Calculations. Compute the energy of the final blow. The toughness is represented by the number of blovvs necessary to break specimen. APPENDIX I FORMULAS IN MECHANICS OF MATERIALS Tension. Relative contraction of area at fracture equals Original area area at fracture original area Relative elongation in gage length equals: Length after fracture gage length gage length Tension and Compression. Church's Mechanics. Merriman's Strength of Materials. P P P= F S =a F F PI P PI 8 E < = E < = F X = E = ae = 1 1 T"- 1 1 iSf 2 TT T"*V - V K SfV V ~ 2 1 "2 E l "2^ c ~2E ' V Mod. of Res. =\~ Mod. of Res. = \ 2 & 2 ft Torsion (Round solid shafts) Pae Me Ppc P. = -j- = y- 8 = j~ IP IP J E - PaL F - Ppl Es ~ ~ Mod. of Res. = - r Cross Bending. Me Me P= "T $ = "T o r>7 q r>/ p = rr 2 (Center Loading, Rectangular Section) v^- 1 P/ 3 1 P/ 3 E = 48 ^U ^ Center Loaflin s) ^ = 48 77 148 APPENDIX 149 ^3 PL 3 4) 3 PI 3 E = (Third Point Loading) E ? 1296 57 Mod. of Res. = \ 2 Hi Impact Bending (Rectangular Beams). Approximate formulas. GHl p *~ E = ZA-on" Road Materials Formulas DEVAL ABRASION TEST , Original weight final weight Loss per cent, (per cent, wear) = - >. . . , =-T"T Origmal weight 20 French coefficient of wear = 20 X w Where w is the weight in grams of the detritus under 0.1G cm. (}>{ e m -) m si ze P er kilogram of rock used. HARDNESS TEST Coefficient of hardness = 20 Y% loss in weight after 1000 revolutions at 28 r.p.m. LEGEND FOR ABOVE FORMULA Church Merriman Width b b Height h d Gage length or span I I Area of cross section F a Moment of inertia 7 7 Polar moment of inertia I p J Radius of gyration k r Distance from neutral axis to extreme fiber .... e c Total load (concentrated) P P Unit stress p S Unit stress at elastic limit tension T" Total elongation in gage length at or before elastic limit . . X e 150 LABORATORY MANUAL OF TESTING MATERIALS Church Merriman Unit elongation e e Twist in gage length (radians) a $ External moment in torsion Pa Pp Deflection d f Mod. of elasticity (ten. and compression) E E Mod. of elasticity (shear) E s F Resilience (work done on specimen) U K IMPACT BENDING: Weight of hammer G Span length I Fiber stress p Modulus of elasticity E Total height of drop // Deflection (total) due to static load G + deflec- tion due to blow. . A APPENDIX II STRENGTH SPECIFICATIONS FOR STEEL AND IRON AMERICAN SOCIETY FOR TESTING MATERIALS, STANDARDS, 1918 Metal Tensile strength, Ib. per square inch Minmum elon- gation, per cent Con- trac- tion of area per cent. Ultimate Yield point in 8 in. in 2 in. Bridges: Structural steel Rivet steel 55- 65,000 46- 56,000 55- 65,000 46- 56,000 58- 68,000 45- 55,000 55- 65,000 52- 62,000 45- 55,000 70- 80,000 85-100,000 95-110,000 90-105,000 55- 65,000 68,000 85,000 100,000 100,000 70,000 105,000 115,000 125,000 1,500,000 22 22 16 20 1,60 40 25 25 35 0,000 ultimate 1,500,000 Buildings- J-2 ultimate Yi ultimate H ultimate >2 ultimate Y% ultimate 3-3 ultimate H ultimate 45,000 50,000 55,000 52,000 ultimate 1,400,000 Rivet steel ultimate 1,400,000 Ships: Structural steel Rivet steel ultimate 1,500,000 ultimate 1,400,000 Boiler and rivet steel for loco- motives: Flange steel ultimate 1,500,000 ultimate 1,500,000 Fire box steel Boiler rivet steel Structural nickel steel: Rivet steel Plates, shapes, bars Eye bars, rollers, un- annealed ultimate 1,500,000 ultimate 1,500,000 ultimate 1,500,000 Eye bars, pins, annealed. . . Steel splice bars: Low-carbon ultimate 20 25 Medium carbon High-carbon Extra-high carbon Quenched high carbon Axles: Cold rolled steel Tens 14 10 10 18 12 10 8 !. str. 35 16 14 12 65,666 60,000 (El. Lim.) Tires driving: Passenger engines Freight engines Switching engines Steel forgings: See Serial, A 18-18, Stand- ards, 1918. ::::::::: 151 152 LABORATORY MANUAL OF TESTING MATERIALS QUENCHED-AND-TEMPERED CARBON-STEEL AXLES, SHAFTS, AND OTHER FORCINGS FOR LOCOMOTIVES AND CARS For forgings whose maximum outside diameter or thickness is not over 10 in. when solid, and not over 20 in. when bored. Size Tensile strength, Ib. per sq. in. Elastic limit, Ib. per sq. in. Elongation in 2 [ Reduction of in., per cent. I area, per cent. Inverse ratio Not under Inverse ratio Not under Up to 4 in. outside diameter or thickness, 2-in. max. wall Over 4 to 7 in. in outside diameter or thickness, 3^2-in. max. wall Over 7 to 10 in. in outside diameter or thickness, 5-in. max. wall 90,000 85,000 85,000 82,500 55,000 50,000 50,000 48,000 2,100,000 20.5 20.5 19.5 19.0 4,000,000 39 39 37 30 Tens. str. 2,000,000 Tens. str. 1,900,000 Tens. str. 3,800,000 Tens. str. 3,600,000 Outside diameter or thickness not over 20 in., 5 to 8-in. wall Tens. str. 1,800,000 Tens. str. 3,400,000 Tens. str. Tens. str. APPENDIX 153 QUENCHED-AND-TEMPERED ALLOY-STEEL AXLES, SHAFTS AND OTHER FORCINGS FOR LOCOMOTIVES AND CARS For forgings whose maximum outside diameter or thickness is not over 10 in. when solid, and not over 20 in. when bored. Class Size Tensile strength, Ib. per sq. in. Elastic limit, min., Ib. per sq. in. Elon- Re- ga- duc- tion tion in 2 of in., area, min., min., per per cent. cent. Up to 2 in. in outside diameter or thickness, 1-in. max. wall 95,000-115,000 70,000 20 50 Over 2 to 4 in. in outside K diameter or thickness, Alloy 2-in. max. wall 90,000-110,000 65,000 20 50 steel, I Over 4 to 7 in. in outside quenched diameter or thickness, and i SH-in. max. wall 90,000-110,000 65,000 20 50 tempered Over 7 to 10 in. in out- side diameter or thick- ness, 5-in. max. wall. . . 90,000-110,000 65,000 20 50 I Outside diameter or thickness not over 20 in., 5 to 8-in. wall 85,000-105,000 60,000 20 j 50 | Up to 2 in. in outside diameter or thickness, 1-in. max. wall 105,000-125,000 80,000 20 50 Over 2 to 4 in. in outside | L diameter or thickness, Alloy 2-in. max. wall 100,000-120,000 75,000 20 50 steel, Over 4 to 7 in. in outside quenched diameter or thickness, and SH-in- max. wall 100,000-120,000 75,000 20 50 tempera! Over 7 to 10 in. in out- side diameter or thick- ness, 5-in. max. wall. . . 100,000-120,000 75,000 18 45 Outside diameter or thickness not over 20 in., 5 to 8-in. wall 9.-),00()-l 1 5,000 70,000 18 45 154 LABORATORY MANUAL OF TESTING MATERIALS Metal Tensile strength Ib. per square inch Minimum elon- gation per cent. Con- trac- tion of area per cent. Ultimate Yield point in 8 in. in 2 in. Steel castings: Hard castings 80,000 70,000 60,000 55-70,000 70-85,000 80,000 min. 55-70,000 70-85,000 80,000 min. Recorded only 80,000 80,000 48-52,000 50-54,000 48,000 45,000 18,000 21,000 24,000 45,000 1 0.45 r t ultimate j 33,000 40,000 50,000 30,000 40,000 50,000 55,000 50,000 50,000 0. 6 ultimate 0. 6 ultimate 25,000 0.5 ultimate 15 18 22 22 in. 4 in. 7H 20 25 30 48 40 30 Medium castings Soft castings Concrete reinforcement bars, billet steel: Plain, structural grade. . . . Plain intermediate grade. . Plain, hard grade Deformed, structural grade Deformed, intermediate grade Deformed, hard grade Cold twisted 1,400,000 ultimate 1,300,000 Tens. str. 1,200,000 Tens. str. 1,250,000 Tens. str. 1,125,000 Tens. str. 1,000,000 Tens. str. 5 1,200,000 Concrete reinforcement bars, rail steel: Plain bars Deformed and hot twisted. Wrought iron: Staybolt iron Tens. str. 1,000,000 Tens. str. 30 25 22 1 Engine bolt iron Refined wrought iron Forgings for locomotives and cars Gray cast iron: Light castings Medium castings Heavy castings Malleable cast iron NOTE. When not otherwise stated values are the minimum allowed. APPENDIX METHODS FOR METALLOGRAPHIC TESTS OF METALS 1 MICROSCOPIC EXAMINATION For unhardened iron and steel, the following process has given satisfaction: 1. After polishing, examine under a magnification of 50 to 150 diameters. Look for slag or cinder in wrought iron, manga- nese sulphide, etc., in steel, and size and shape of graphite in cast iron. 2. Etch with a saturated solution of picric acid in alcohol for 15 seconds. This reveals the pearlite by turning it darker than the accompanying ferrite or cementite. In wrought iron, any pearlite present shows up, and the general appearance will some- times show whether the material was puddled, etc., or made from reheated scrap. Those who wish to bring out the ferrite grains can do so easily and quickly by etching with nitric acid. To this end, nitric acid of 1.42 specific gravity should be diluted with either : (a) 90 parts by volume of water to 10 of acid, (6) 75 parts by volume of water to 25 of acid, or preferably (c) 96 parts by volume of amyl alcohol to 4 of acid. 3. Near the eutectoid point, that is, 0.6 to 1.0 per cent, of carbons it is often difficult to distinguish between thin envelopes of ferrite and cementite. This difficulty can be overcome by etching with a solution of sodium picrate, which turns cementite dark brown or black but does not color the other constituents. The solution is made by adding 2 parts of picric acid to 98 parts of a solution con- taining 25 per cent, of caustic soda, and is used at 100C. 4. In order to interpret the results of such an etching, they should be compared with standard etched specimens. 5. In the case of hardened and tempered steel the indica- tions are less decisive than in the case of unhardened steel, probably because the former class has been studied less than the latter. Coarse grain, segregation of constituents, presence of oxide, etc., are all signs of bad material. For etching use a solution of 4 parts of nitric acid, specific gravity 1.42, in 96 of amyl alcohol. The time needed has to be found by trial in each case. Hence etch for 5 seconds, examine, re-etch if necessary, etc. 6. Macroscopic examination shows up defects due to segregation, 1 From Standard Methods for Testing. Amer. Soc. for Test- ing Materials, 1918. 156 LABORATORY MANUAL OF TESTING MATERIALS blowholes, piping, and the like, and when used in connection with microscopic examination yields valuable information. A section is cut with a saw, filed smooth, and polished with No. and No. 00 emery paper; it is then ready for etching. Quite a number of etching reagents have been used to develop the structure. Whichever solution is chosen, the specimen is first carefully washed with a strong caustic potash solution, well rinsed under the tap, and then immersed in the etching solution. The following may be mentioned : (a) Freshly prepared solution of 20 g. of I and 30 g. of Kl, in 1000 g. of water. (6) Dilute HC1 or H 2 SO 4 up to 30 per cent, acid, using the 1.2 and 1.84 specific gravity respectively. (c) Nitric acid, from 10 to 30 per cent, of the 1.42 specific gravity acid in 90 to 70 per cent, of water. (d) Concentrated HC1, specific gravity 1.2. (e) A solution of 10 or 12 parts of double copper-ammonium chloride in 90 or 88 parts of water. To bring out the structure of wrought iron rapidly, (d) is used, while (c) or (6) will bring it out more slowly. For steel, first etch with (a), which shows up the segrega- tion of carbon very well. Take care not to over-etch; 5 seconds is enough for some materials. To show up the impurities and the. segregation of MnS, slag, etc., (d) acts quickly, but (6) gives better results though taking longer. Some prefer light etching, say after 1 or 2 minutes, but an older method is to etch with (6) very deeply, indeed to a depth so great that several hours may be needed to reach it. In this way the segregation of the carbon and the impurities like slag and MnS are shown simultaneously. A picture of the object thus etched can be had by treating it like an engraving, that is, inking it with printer's ink, and printing on white paper directly from it. A common letter-copying press is convenient for this printing. STANDARD SPECIFICATIONS FOR PORTLAND CEMENT' SERIAL DESIGNATION: C 9-17 1. Definition. Portland cement is the product obtained by finely pulverizing clinker produced by calcining to incipient fusion an intimate and properly proportioned mixture of argillaceous and Authorized Reprint from the Copyrighted A.S.T.M. Standards (1918), American Society for Testing Materials, Philadelphia, Pa. APPENDIX 157 calcareous materials, with no additions subsequent to calcination excepting water and calcined or uncalcined gypsum. L CHEMICAL PROPERTIES 2. Chemical Limits. The following limits shall not be exceeded : Loss on ignition, per cent . 4 . 00 Insoluble residue, per cent . 85 Sulfuric anhydride (SO 3 ), per cent 2.00 Magnesia (MgO), per cent 5.00 //. PHYSICAL PROPERTIES 3. Specific Gravity. The specific gravity of cement shall be not less than 3. 10 (3.07 for white Portland cement) . Should the test of cement as received fall below this requirement a second test may be made upon an ignited sample. The specific gravity test will not be made unless specifically ordered. 4. Fineness. The residue on a standard No. 200 sieve shall not exceed 22 per cent, by weight. 5. Soundness. A pat of neat cement shall remain firm and hard, and show no signs of distortion, cracking, checking, or disintegration in the steam test for soundness. 6. Time of Setting. The cement shall not develop initial set in less than 45 minutes when the Vicat needle is used or 60 minutes when the Gillmore needle is used. Final set shall be attained within 10 hours. 7. Tensile Strength. The average tensile strength in pounds per square inch of not less than three standard mortar briquettes (see Section 51) composed of one part cement and three parts standard sand, by weight, shall be equal to or higher than the following : Veeat Tensile -Age ell ofrAnirtVi test, Storage of briquettes ,, ' ' dav4 lb- per sq. in. 7 1 day in moist air, 6 days in water ! 200 28 j 1 day in moist air, 27 days in water j 300 8. The average tensile strength of standard mortar at 28 days shall be higher than the strength at 7 days. 158 LABORATORY &ANTJAL OF TESTING MATERIALS ///. PACKAGES, MARKING AND STORAGE 9. Packages and Marking. The cement shall be delivered in suitable bags or barrels with the brand and name of the manu- facturer plainly marked thereon, unless shipped in bulk. A bag shall contain 94 Ib. net. A barrel shall contain 376 Ib. net. 10. Storage. The cement shall be stored in such a manner as to permit easy access for proper inspection and identification of each shipment, and in a suitable weather-tight building which will protect the cement from dampness. IV. INSPECTION 11. Inspection. Every facility shall be provided the purchaser for careful sampling and inspection at either the mill or at the site of the work, as may be specified by the purchaser. At least 10 days from the time of sampling shall be allowed for the completion of the 7-day test, and at least 31 days shall be allowed for the completion of the 28-day test. The cement shall be tested in accordance with the methods hereinafter prescribed. The 8-day test shall be waived only when specifically so ordered. V. REJECTION 12. Rejection. The cement may be rejected if it fails to meet any of the requirements of these specifications. 13. Cement shall not be rejected on account of failure to meet the fineness requirement if upon retest after drying at 100C. for one hour it meets this requirement. 14. Cement failing to meet the test for soundness in steam may be accepted if it passes a retest using a new sample at any time within 28 days thereafter. 15. Packages varying more than 5 per cent, from the speci- fied weight may be rejected; and if the average weight of pack- ages in any shipment, as shown by weighing 50 packages taken at random, is less than that specified, the entire shipment may be rejected. APPENDIX 159 TENTATIVE SPECIFICATIONS ANJQ TESTS FOR COM- PRESS1VE STRENGTH OF PORTLAND-CEMENT MORTARS AMERICAN SOCIETY FOR TESTING MATERIALS Serial Designation : C 9-16T These specifications and tests are issued under the fixed designa- tion C 9; the final number indicates the year of original issue, or in the case of revision, the year of last revision. ISSUED, 1916 SPECIFICATIONS 1. Compressive Strength. The average compressive strength in pounds per square inch of not less than three standard mortar test pieces (see Section 4) composed of one part cement and three parts standard sand, by weight, shall be equal to or higher than the following: Com- Age at pressive test, Storage of tost pieces strength, days , Ib. per sq. in. 7 1 day in moist air, 6 days in water 1200 28 1 day in moist air, 27 days in water 2000 2. The average compressive strength of standard mortar at 28 days shall be higher than the strength at 7 days. 3. The requirements governing the preparation of standard sand mortars for tension test pieces .shall apply to compression test pieces. SPECIFICATIONS FOR AGGREGATES (1) American Railway Engineering Association, 1920, for Structures Fine Aggregate. The fine aggregate shall consist of sand, crushed stone or gravel screenings, graded from fine to coarse, and passing when dry, a screen having holes one-quarter (^) inch in diameter. Not more than 25 per cent, by weight shall pass a 160 LABORATORY MANUAL OF TESTING MATERIALS No. 50 sieve, and not more than per cent, a No. 100 sieve when screened dry, nor more than 10 per cent, dry weight shall pass a No. 100 sieve when washed on the sieve with a stream of water. It shall be clean and free from soft particles, mica, lumps of clay, loam or organic matter. Coarse Aggregate. The coarse aggregate shall consist of gravel or crushed stone, which, unless otherwise specified or called for on the plans, shall, for plain mass concrete, pass a screen having holes two and one-quarter (2^) inches in diameter, and for reinforced concrete a screen having holes one and one-quarter (1^) inches in diameter; and be retained on a screen having holes one-fourth (K) m ch diameter, and shall be graded in size from the smallest to the largest particles. It shall be clean, hard, durable and free from all deleterious matter; coarse aggregate containing dust, soft or elongated particles shall not be used. (2) Indiana State Highway Commission for Concrete Roads Fine Aggregate. The fine aggregate shall consist of sand con- forming to the following requirements : The sand shall consist of clean, hard, durable grains. When dry, it shall pass a laboratory screen having circular openings one- quarter ()4) of an inch in diameter. Not more than 50 per cent, by weight, shall pass a No. 30 laboratory sieve, and not more than 10 per cent, by weight, shall pass a No. 100 sieve. It shall be free from organic matter and not more than five (5) per cent, by weight, shall be removed by the elutriation test. Gravel. Gravel shall consist of clean, sound, hard stone, reasonably free from soft, thin, or elongated pieces. Gravel containing clay or coatings of any character shall not be used. It shall show high resistance to abrasion, and no gravel shall be used which, in the opinion of the Engineer, does not show wearing qualities at least equal to crushed stone having a French coefficient of wear of seven (7). Pit run gravel shall not be used. When tested by means of laboratory screens having circular openings, gravel shall meet the following requirements : Passing 2^ inch screen 100 per cent. Passing 2 inch screen, not less than 95 per cent. Passing % inch screen, 30 to 70 per cent. Passing l / inch screen, not more than 5 per cent. If the Engineer deems it advisable, he may permit the use of material that conforms to all the requirements of the specifications for coarse aggregate excepting that of gradation APPENDIX 161 of sizes, and then provided sufficient additional cement is used to produce concrete of a quality equal to that resulting from the use of similar aggregate of the specified grading. PROPOSED TENTATIVE SPECIFICATIONS FOR COMMERCIAL SIZES OF- GRAVEL, BROKEN STONE AND BROKEN SLAG, AMER. Soc. FOR TESTING MATERIALS 1920. 1. These specifications cover the standard size designation 8 and maximum permissible range in mechanical analyses for nine commercial grades of broken stone and broken slag, when used in the construction of plain or bituminous macadam, bituminous concrete, sheet asphalt and cement-concrete roads and pavements. Gravel : MAXIMUM PERMISSIBLE RANGE IN MECHANICAL ANALYSES FOR EACH SIZE Percentage by Weight Passing Each Screen Diameter of screen openings, in. Designated size, . ___ . YA. : '2 a 4 1 I, 1 -J 2 2H I 3H - >ia 95-100 - y^b 85-100 X- 1 A c 95-100; Yi- H c 95-100 y-\ c 25- 75! 95-100J y-\Y-i > ' 25- 75 i 195-100 H-2 c 25- 75J 95-100 *-2M c I : 125- 75 95-100 1 -2 0-15' 85-100; 2 -3y z \ '' i 0- 15 185-100 a Additional requirements for grading shall be as follows: Passing 20-mesh sieve 25 to 75 per cent. Passing 50-mesh sieve not over 25 per cent. Passing 100-mesh sieve not over 5 per cent. b Limits for silt and clay content may be inserted if desired. Any percentage from to 10 per cent, may be designated, with a maximum permissible variation therefrom of not more than 2> per cent. Broken Stone and Broken Slag. The designated size for each grade together with the corresponding maximum permissible variations in mechanical analyses as determined by the use of laboratory screens, are given in the following table: 11 162 LABORATORY MANUAL OF TESTING MATERIALS MAXIMUM PERMISSIBLE RANGE IN MECHANICAL ANALYSIS FOR EACH SIZE Percentage by Weight Passing Laboratory Screens Designated size, in. Diameter of screen openings, in. H H ' m 2H m - K o - y* o - x Mr X x-iy* K-VA K-VA 1X-W 2K-3M a 85-100 0- 75 40- 80 0- 15 3- 10 0- 5 95-100 25- 75 95-100 95-100 65- 85 0- 15 95-100 25- 75 95-100 0- 15 95-100 95-100 0- 15 95-100 25- 75 a In the case of light or porous slags a 4-in. maximum size may be specified instead of 3> in. APPENDIX III STANDARD FORMS OF TEST PIECES U-About 3^1 a !? ion not le *s than 9 _ J_ r? T ? ^ Etc. About 18" FIG. 1. Wrought iron, structural steel and boiler plate. Plate metal in general. k 3 FIG. 2. Malleable cast iron. Radios &ot less than U" 214 H ! D 1 -2 Gage Length-^- Kote;-The Gage Length, Parallel Portions and Fillets shall be as Shown, but the Ends may be of any Form which, will Fit the Holders of the Testing Machine . FIG. 3. Structural steel, wrought iron, steel castings and forgings, axle and tire steel. FIG. 4. Screw end test piece, 163 104 LABORATORY MANUAL OF TESTING MATERIALS Kadi as not less ["* than '4. 4-U- i i . _ ~^ 1 i r r - T 1 ? U 4-Gage Length- - Note '.-The Gage Length, Parallel Portions and Fillets shall be as Shown, but h.e Ends ihay b of any Form which will Fit the Holders of the Testing Machine . FIG. 5. Wrought iron forging for locomotives and cars. Mold for Gray Cast Iron Test Specimens. The form and dimen- sions of the mold for the arbitration test bar shall be in accordance with Fig. 1. The bottom of the bar shall be KG in. smaller in dia- meter than the top, to allow for draft and for the strain of pouring. The pattern shall not be rapped before withdrawing. The flash shall be rammed up with green molding sand, a little damper than usual, well mixed and put through a No. 8 sieve, with a mixture Pattern ,*" r*i U..! ; i\ Pouring L'asin /'' ^I^^Js^^i Cope i U mj& i 1 s ^-10 Pipe L. ?.-:--. Borod with H Hi II" Teut Holes J;V^ %PSl an %$iA 5 f ^^^^^^^M FIG. 6. Mold for arbitration test bar. of 1 to 12 bituminous facing. The mold shall be rammed evenly and fairly hard, thoroughly dried, and not cast until it is cold. The test bar shall not be removed from the mold until cold enough APPENDIX -Standard Thread' 165 FIG. 7. Arbitration test bar. Tensile test piece. to be handled. It shall not be rumbled or otherwise treated, being simply brushed off before testing. APPENDIX IV 1 z * "3 M_ . 83' U J-.2-3 STRENGTH TABLES Us (NCNCO CO II II II II COCOCO CO - J V) spa^s ^jos-fpaBq Joj tug -o = eg II II II pe}fld$~ff aaput^a ^joqs u'aq^) Ag = g CO 00 CO v o 2 n T I! ^43 II I! o -8 -ut 'bs -q{ OOO'OOO'OS = ; 2 :jg '000'000'I8-8S tuojj 7 ; i eauBA siao^s HB jo A^iopSBia jo sninpoi\r csi . co 00 OOX5000M '^ COOiCOOU? O,(NCO CC'CO CO -CO O iO CO ' do d -odd 6 ' o ^ uig o; dg jo OKJBH n-OOO t>-t^- &O5 CO O OCO O *OJ &s CO M r^ -r- -t^ Ii > oM . 166 APPENDIX 167 it 00 CO* 'O s 10 r^ 2 2 <* O 00 II ^ Jj ci 00 t* C^ CO "" 1 rJH CO rH ^ ^ 00 O5 s 5 S H OS 00 CO CO C. CO (M -(MO rH (N CO (M tO tO rH tO 00 O^ t^ ^f tO rH IO C^ to s ^0 o o oo oo o Li tO CO rH CO CO W CO O^ to rH rH CO C +j ^o Tt< co H S tQ i t ^ p ^^ a (^ O 1 CO ^O 1 S rH 4*j ;r * s coto o >> &s 00 C5 O t^* C^l O 00 O !> O ~ 1 Ol OQ CO ^ ^ co oe 00 00 00 C^ C^l CO t> l^ t^ 00 00 . l^ : : 73 : : : : : ** fl|a . . . ^ : : 3 - : : :- : : : : fl 2- 1 S -r rC ' bC ' !l| 0) CJ N 111 8 6 PQ *2! :' ;; ; 1 ""' : S : : ^ ^' - b , fl fi ^ ' *o3 S'.fl'i : f3 1 6 : JJPlfJS ^ ^ Q N S H O Phosphor bronze . Manganese bronze Tobin bronze Aluminum bronze Cu, 10 per cent 168 LABORATORY MANUAL OF TESTING MATERIALS .^ IJ -?8 I. ft >o aJ ^ I M I S la' 1 PH - s !| c ^ O 00 "t< O COOO * >> ai -w ! : O O O O O O 3'S 1 ^ i O O O O O O 00 I-H 00 *-H TP IQ ^O 00 (M l> S : ^ .S ^ J ^|5^ ^^ ^5 OO ft Tf< ^ II O O iQ lO 00 CO O r^ CO !> CO O I ^^ ^ c^ ^[} ^Q -% , ,no W _ : ; rH CO CO x^-s : : od d d O HH o i>- i>- co o o Oi O5 r -C C^ O5 T^ (N rH rH rH CO ^n ^fi co 00*0*0 -*' cq t^." co 11 5 ^N? 02 | -d .S rS W ^. 1^ S i 3- U Pq PH OJ rH rH rH INDEX PAGE Abrasion test of stone (experiment) 142 of wood (experiment) 75 Absorption test of paving brick (experiment) 142 Accelerated tests of cement (method) 87 (specification) 157 Accuracy of testing machines 21, 51 Aggregates, study of 93 determination of silt in (experiment) 96 of voids in (experiment) 105 effect of moisture on volume of (experiment) 106 notes on sampling of 93 sieve analysis of (experiment; 109 specific gravity of (experiment) 102 specifications for 159 weight of 99 Amsler testing machine 29 Amer. Soc. Testing Materials; methods for testing cements .. 76 Amer. Soc. Testing Materials, specifications for cement 156 strength specifications for steel and iron 151 methods for metallographic tests of metals 155 Amount of water required for mixing concrete 115 Analysis of cement (method) 77 Apparatus for gripping test pieces in tension 21 Appendix I, common formulas 148 IT, strength specifications, iron and steel 151 specifications, for cement 156 III, forms of test pieces 163 IV, strength tables 165 iron and steel 165 copper and alloys 166 timber 167 stone and brick 168 171 172 INDEX- PACK Applying the load, methods of, in testing machines 27 Autographic recording apparatus 42 tension test of iron and steel (experiment) 56 B Bond strength of steel in concrete 138 Brake beam, flexure test of (experiment) 65 Brick, strength of (table) 1 68 cross bending and compression tests of (experiment) .... 139 Brinell test for hardness 34 Briquettes, cement 89, 91 Brittle materials compression tests of (experiment) 134, 136 C Calibration of extensometers 51 of testing machines 50 Cast iron, flexure of (experiment) 64 tension of (experiment) 55 Cement, Amer. Soc. Testing Materials, methods of testing . . . 76 Amer. Soc. Testing Materials, specifications for 156 chemical analysis 77 compressive strength of (determination) ; 92 constancy of volume (soundness) 87, 157 fineness of (method) 83 (specification) 157 mixing and molding (method) 84 mortar, consistency for 86 specification for 159 standard sand 89, 90 tensile strength of 89 normal consistency neat, Vicat method 85 sampling, instructions for 76 specific gravity of (method) 82 (specifications) , 157 storage of test pieces 91 time of setting of, Gil more method 89 Vicat method 88 specifications for 157 INDEX 173 PAGE Cementation test of road materials (experiment) 143 Columns, test of wood (experiment) 70 Compression of brittle materials (experiment) 134, 136 of helical springs (experiment) 62 short wood blocks parallel to grain 67 perpendicular to grain 69 Compressive strength of cement and cement mortars 92 Compressometers 40 Concrete, compressive strength of (experiment) 132, 133 proportioning by sieve analysis 122 by fineness modulus (experiment) 130 by surface areas (experiment) 128 Cone test for consistency 117 Consistency for cement mortars 86 Consistency, method of measuring 116 Constancy of volume of cements 87, 157 Copper and alloys, mechanical properties of (table) 166 D Definitions 10 stress 10 elasticity * 12 resilience 14 Density and strength 127 Drum records from Turner impact machine 31 E Elasticity, definition of 12 Endurance testing machine 32 Extensometers, calibration of (experiment) 51 description of .-. 37 tension test with (experiment) 57 F s Fatigue testing machine 32 Fineness modulus 130 Fineness of cements (determination) 83 (specification) . 157 174 INDEX PAGB Flexure tests 25 test of brake beams (experiment) 65 of cast iron (experiment) 64 of large wood beams (experiment) 73 of small wood beams (experiment) 71 of reinforced concrete beam (experiment) 137 Forms of test pieces for iron and steel 163 Formulas, common 148 Fractures, materials under compression 17 under tension 17 Fuller's maximum density curve 110 G General instructions 4 Grips, proper arrangement of in tension test 24 H Handmixing of Concrete 113 Hardness 34 Brinell ball test 34 Scleroscope test 34 test of road materials (experiment) 145 Helical Spring, compression of 62 Holding the specimen in tension and compression 21 in flexure 25 in shear 26 Hydraulic testing machines 28 I Identification of woods, laboratory exercise 66 Impact test of wood beams 74 Iron and steel, autographic tension test of 56 fractures of 17 mechanical properties of (table) 165 commercial tension test of (experiment) 52 L s List of experiments 44 Load, method of applying, in testing machines 27 INDEX 175 PAGE Loss on ignition, for cement (determination) 77 (specification) 157 M Material stressed beyond elastic limit 16 Metals, methods of metallographic tests of 155 Method for testing cement, Amer. Soc. Testing Materials ... 76 Mixing and molding cement test pieces (method) 84 Mixing concrete by hand 113 Mixing concrete by machine 114 Moisture in aggregates, effect of on voids 106 N Normal consistency for cements (determination) ........... 85 Note keeping O Organic matter in silt (test) 98 Ottawa sand 89 Overstrain, effect of on yield point of steel 63 P Paving brick, absorbtion test (experiment) 142 rattler test of 140 Portland cement, definition of ( 156 specification for 156 Proportioning concrete by sieve analysis 122 by fineness modulus (experiment) 130 by surface areas (experiment) 128 theory of 119 Q Quartering, sampling aggregates by method of 95 Quantities required for concrete Ill R Rattler test of paving brick (experiment) 140 Reinforced concrete beam, test of (experiment) 137 176 INDEX Reinforcing fabric, test of concrete ....................... 139 Reports ............................................... 5 instructions for writing .............................. 7 Resilience, definition of .................................. 14 Road materials, cementation test ......................... 143 hardness test ................... . .................. 1 45 toughness test ...... ............................... 140 S Sampling aggregates, notes on ........................... 93 cement, method of ................................. 76 Sand, strength tests of (experiments) . . . ........... 98, 127, 132 Sands, yield or volumetric test of (experiment) ............ 127 Scleroscope, test for hardness with ....................... 34 Setting of cement, time of (determination) .............. 88, 89 (specification) ...................................... 157 Shear tests ............................................ 26 Shipping and storage of samples of aggregate .............. 95 Sieve analysis of aggregates (experiment) .................. 109 proportion concrete by .............................. 122 Sieves, sizes of commercial (table) ........................ 108 study of ................................... ........ 107 Specific gravity of aggregates (experiment) ................ 102 of cement (determination) ........................... 82 (specification) .................................... 157 Specifications for cement, Amer. Soc. for Test. Mat ........ 156 Standard sand ....................................... 89, 90 Staybolt iron, vibration test of ........................... 65 Steel and iron, mechanical properties of ................... 165 castings, tension test of .............................. 55 effect of overstrain on yield point of .................. 63 fracture of ......................................... 17 tension test of iron and (experiment) ................. 52 Stone, abrasion test of (experiment) ...................... 142 strength of (table) ................................. 168 Storage of cement test pieces ............................ 91 Strength specifications steel and iron, A. S. T. M .......... 151 Strength and density ................................... 127 Stress, definition of ..................................... 10 INDEX 177 PAGE Study of testing machines (experiment) 48 Surface areas of aggregates (experiment) 128 T Tensile strength of cements (determination) 89 (specifications) 159 Tension test of iron and steel (experiment) 52 Testing machines 29 accuracy of 21, 50 calibration of 50 endurance 32 hydraulic 28 impact 30 operation of, during test 4 screw 27 sensitiveness of 21, 51 study of (experiment) 48 table of large, in United States 22 weighing mechanisms of 35 Test piece, standard forms of, iron and steel , 163 pieces, storage of cement 91 Timber, strength of structural (table) 167 Torsion, experiment in 59 Toughness test of road materials (experiment) 146 Two inch cylinders, unit stresses for (table) 93 Vibration test of stay bolt iron (experiment) 65 Voids in aggregates, determination of 105 Volumetric tests of sands 127 W Weighing mechanisms of testing machines 35 Wire cable, test of (experiment) 61 Wood, abrasion test of 75 beam, flexure of large 73 of small 71 178 INDEX PAGE Wood, beam, impact test of 71 columns, test of 70 compression of, parallel to grain 07 perpendicular to grain 69 determination of moisture content in 73 Woods, identification of (experiment) 66 Y Yield or volumetric test of sands 127 Yield of concrete . . .111 THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO 5O CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. SEP 10 1932 32 UV4 UNIVERSITY OK CALIFORNIA LIBRARY