NRLF 
 
 54 
 

 
 CONCRETE 
 REVIEW 
 
 GERMAN METHODS IN 
 PORTLAND CEMENT 
 MANUFACTURE 
 
 DRY AND WET PROCESSES 
 By DR. OTTO SCHOTT 
 
 PUBLISHED BY 
 
 THE ASSOCIATION OF AMERICAN PORTLAND 
 CEMENT MANUFACTURERS-IANDTITLE BLDG'PHILA- 
 
 SUBSCRIPTION 50 CENTS PER YEAR SINGLE COPIES SCENTS 
 
German Methods in Portland Cement 
 
 Manufacture. Dry and Wet 
 
 Processes. 
 
 BY DR. OTTO SCHOTT, 
 
 TECHN. CHEMIST, HEIDELBERG. 
 
 Gentlemen: Last year, when seeking information concerning 
 the manufacture of cement in the United States of America, I had 
 the opportunity of inspecting a large number of your cement works 
 and studying American equipment and methods of manufacture. 
 The impressions I gathered are probably known to you for the most 
 part from the publication of some of the lectures I have given in 
 Germany and Austria on the subject. Although it is difficult from a 
 mere inspection to form a correct picture of the working methods of 
 the different factories, still I think that on the whole I have correctly 
 judged the American Portland cement industry. 
 
 To-day I want to give you a picture of the German cement 
 industry, based not only on the inspection of various factories, but 
 also on an experience of many years in this industry. In many 
 respects the German cement industry has a different manner of work- 
 ing from the American, and I think it will interest you all if in my 
 remarks I refer particularly to these divergencies. I think that in 
 this way you will learn more than by visiting different factories in 
 Germany. 
 
 Although the German cement industry is considerably older than 
 the American, and Portland cement was manufactured in Germany 
 more than fifty years ago, the total production has to-day only 
 reached the figure of 30,000,000 barrels, which are made in about 
 100 factories, of which 96 factories are united in the Association of 
 German Portland Cement Manufacturers. In comparison with the 
 enormous increase of the young American cement industry, with its 
 production of 73,000,000 barrels last year, it might seem that the 
 German cement industry has not made the progress it ought to have 
 
 M12991 
 
made. But you should bear in mind that Germany is only a small 
 country, not even as large as the State of Texas. In proportion to 
 its area, it still holds the first place with its cement production. You 
 should further bear in mind that, partly on account of narrow- 
 minded building regulations and partly through the presence of 
 sufficient quantities of natural building stone, Portland cement is 
 not nearly so much used in Germany as in America. The Germans 
 have not yet engaged in the use of cement in such an admirable 
 manner as I have found in your country. As regards the quality 
 ..of tbe.* ertje}it: and the cost of manufacturing, I think I can con- 
 ''scienttoilsly* assert that Germany is ahead of many countries. With 
 
 ; ijje'iaj'l^ qv.erjDrotluction, which greatly exceeds the demand, the 
 * 'ma'nufacturers *w*ere forced to manufacture the cement as cheaply 
 as possible, and constantly to improve the quality. 
 
 I will first give you a picture of how the cement works are dis- 
 tributed over all Germany. You see that in various places the 
 factories lie close together, as is the case in the Lehigh district 
 or in Kansas. If you bear in mind that the area of Germany is not 
 larger than the States of Pennsylvania and New York together, 
 and if you also consider that the adjoining countries, as Belgium, 
 France, Austria, and Switzerland, also produce cement, and are able 
 to import it free of duty into Germany, while, on the other hand, 
 the countries levy a high duty on Portland cement from Germany, 
 you can then form an idea of the great difficulties with which the 
 German cement industry has to contend. About one-fourth of the 
 cement works are in Rheinland and Westphalia, where they are as 
 close together as here in the Lehigh district. The proximity of the 
 coal mines and an excellent raw material have favored the building 
 of so many works in one spot. Similar groups of cement works 
 are found near Hannover, Hamburg and in Silesia, only the 30 fac- 
 tories situated in south Germany being fairly evenly distributed. 
 That, with this large number of factories and their large producing 
 capacity, the German cement industry still prospers to a certain 
 degree, is to be attributed, in the first place, to the formation of syn- 
 dicates, which fix " quotas "for the various factories and take care 
 that no more cement is manufactured than can be sold, and which 
 also regulate the prices by fixing minimum prices at the commence- 
 ment of each year. 
 
 We have at present in Germany five syndicates, the oldest and 
 firmest of which is the South German Cement Syndicate, which was 
 prolonged last year until the year 1925. Each factory is given a 
 
"quota" in proportion to its producing capacity, and it participate 
 in proportion to its " quota" in the increase in consumption. The 
 sale of the cement is done through a central office, which has five 
 further sales-offices under it to facilitate the transaction of business. 
 No factory can sell direct to the consumers, and all sales must be 
 made through the sales-offices. The sales territory of each syndicate 
 is carefully defined by contract, so that each syndicate may only sell 
 within a definite circuit of the factories belonging to it, whereby 
 large economies in freight are made. The price of a barrel of cement 
 is at present $1.00 to $1.25. 
 
 The fixing of the price is determined so that the smaller factories 
 belonging to the syndicate shall have a normal profit, but the price 
 of foreign cement and of other building materials has also to be con- 
 sidered. 
 
 It would certainly be wrong to assume that the regulation of 
 prices is done arbitrarily for the sole object of getting the highest 
 possible prices. The principal merit of the syndicates is that they 
 balance the production of the factories with the sale of the cement. 
 The syndicate in Rheinland and Westphalia operated its factories 
 last year 57 per cent, of their producing capacity, and the South 
 German syndicate 78 per cent. 
 
 The syndicates in the different districts of Germany are connected 
 by agreements, which determine how far each factory can sell in its 
 environs. 
 
 Raw material for Portland cement is found pretty nearly all over 
 Germany, principally limestone with shale, and it frequently has 
 naturally the proper combination for Portland cement. Such de- 
 posits you will find in south Germany, principally in Wurttemberg, 
 in the Swabian Jura, around Hannover and also on the Rhine. Some 
 factories, principally in central Germany, use limestone with clay, 
 which is mostly very damp. The cement works on the northern 
 coast around Hamburg and Stettin use wet chalk and clay as raw 
 material and work on the wet process. 
 
 Such pure limestone as is used for cement-making in many places 
 in America is not met with in Germany. On this account white 
 Portland cement is not made in Germany on a large scale. 
 
 The quarry of a German cement factory presents quite a different 
 aspect from an American one. The steam-shovel, which is found 
 here in almost every cement factory, is not yet used in Germany, 
 as the factories are mostly so small that the purchase of a steam- 
 shovel would not pay. Where the lime stratum, as in Westphalia, 
 
is only 20 feet thick, the stone is loosened by hand and shoveled into 
 the cars. Only small tip-cars containing about 1 square yard are 
 used, and they are hauled direct into the factory by means of a wire 
 rope-way. You will find nowhere in Germany such large locomotives 
 as are customary here in many places. The wire rope-way and the 
 suspended rail are preferred, as by them smaller quantities of raw 
 material are regularly transported to the factory at quite even inter- 
 vals, and can then be tipped direct into the crusher without any 
 interruption. 
 
 Fig. 1. Gallery- work. Wall of Quarry Prepared for Blast. 
 
 When the limestone strata is thicker, i. e., from 65 to 100 feet 
 high, the so-called "gallery-work" is applied. 
 
 The entire wall of the quarry is undermined to a breadth of 65 
 to 160 feet by driving single horizontal galleries 65 feet long into the 
 wall. At a depth of 33 feet these are joined together by a cross- 
 drift, so that finally the whole side of the quarry rests only on single 
 pillars 6J^ feet high and 6J^ feet in diameter. Each of these pillars 
 is then bored in three places and the drill-holes are charged with 
 donarit, dynamite not being used in Germany on account of its 
 dangerous properties. 
 
 4 
 
As soon as the so-called "fall" is prepared, the charges are all 
 fired simultaneously by electricity, the pillars are all blown away at 
 the same time, the side of the quarry loses its support and falls to 
 pieces, at the same time breaking up the large rocks. The material 
 is then shoveled into cars by hand. This work could certainly be 
 done profitably by one of the steam shovels used in America, and 
 which have recently been introduced into Germany. The prepara- 
 tions for such a "blasting" take up months, but the material loosened 
 and broken up in this way lasts for months, and while it is being 
 loaded off and worked up, preparations are made for the next blast- 
 
 Fig. 2. Gallery-work after the Blast. 
 
 ing. The heap of material you see here contains 50,000 square yards, 
 and sufficed for the making of 300,000 barrels. This way of quarry- 
 ing has many advantages : above all things, all danger to the workmen 
 is eliminated, as they do not need to climb about the steep sides of 
 the pit. All work is done at the bottom of the pit. A fairly uniform 
 mixing takes place in the pit by the rock all falling down together. 
 The layers rich in clay are mixed with those rich in lime. 
 
 A disadvantage, however, is that with frequent rains the heap of 
 material often gets wet, and the drying is rendered difficult. On 
 
 5 
 
this account some cement works in Germany have recently intro- 
 duced the glory-hole method. At the foot of the quarry a single 
 passage 100 to 130 feet deep is driven into the quarry side, and from 
 the end of the same a shaft is bored straight upward, until the surface 
 is reached. At the foot of this shaft there is fitted a horizontal door 
 sliding on rails, which can be opened and shut by means of a lever. 
 They then start to widen the top of the shaft funnel-shape by 
 loosening the material around the shaft and letting it simply roll down 
 to collect on top of the closed sliding door. 
 
 Fig. 3. Floor of Quarry with Passage for Glory-hole and Wire Rope-way. 
 
 The wire rope-way is brought right up to this slide, the cars are 
 run under, the slide opened until a car is filled and then closed. The 
 full car now runs automatically on the wire rope into the works. 
 Such a glory-hole yields with four men (two up above, two down 
 below) 300 square yards of material in a twelve-hour day. The 
 benefit of this method lies in avoiding the picking up of the material 
 with the hand or steam shovel, and at the same time it has the ad- 
 vantage of safety and of blending the different layers. Besides, 
 in rainy weather the water runs off down the steep sides, so that 
 the material keeps dry. Boring is generally done with compressed 
 
 6 
 
air and small boring machines, similar to those you have here in 
 America. 
 
 As I have already remarked, the material forwarded by wire .rope 
 or suspended monorail direct into the works is tipped direct into the 
 crushing machinery. Unlike America, the Blake crusher is still 
 preferred in Germany, and the Gates crusher is very seldom met 
 with. If the material is not so hard, the so-called crushing- worm 
 is often used. The same consists of a thick shaft provided with 
 
 Fig. 4. Car being Filled from the Glory-hole through the Sliding Door. 
 
 grooves, which rotates between horizontal bearings inside a casing 
 lined with steel plates. 
 
 For drying, the Cummer rotary drier is much used in Germany. 
 In general, the German rotary drier has a much smaller diameter 
 
 7 
 
than the American, usually only 39 inches. In America coal-dust 
 has been applied in recent years for heating the rotary driers, an 
 arrangement which the Portland Cement Works of Heidelberg and 
 Mannheim introduced twelve years ago in all their works, except 
 that there was built in front of the cylinders a chamber with grating 
 in which the firing took place. It has been proved that with the use 
 of coal-dust the drying of the raw material is much more thorough 
 and the coal consumption less. 
 
 Fig. 5. View from Top of Glory-hole. The Material is Loosened and Rolls down 
 before the Closed Sliding Door. 
 
 I should like to make mention here of a special rotary drier, with 
 which the utilization of the hot gases is profitably increased by the 
 division of the inside of the cylinder in separate cells. By this 
 means a more uniform distribution of the material in the interior 
 of the cylinder is obtained, and the surface is also increased, which 
 facilitates the drying. With very wet material there is naturally the 
 danger of some of the cells getting blocked up, but for drying coal a 
 more ideal rotary drier cannot be imagined. 
 
 With such a drier, 6 feet 6 inches in diameter and 33 feet long, 
 180 tons of rather small moist coal are daily dried at Heidelberg. 
 
 8 
 
For grinding the raw material the same systems of mills are used 
 in Germany as here in America, namely, ball-mills, Kominor, tube, 
 Griffin, and Fuller mills. 
 
 The Portland Cement Works, Heidelberg, have nothing but 
 Griffin mills running in six of their seven factories, on both raw ma- 
 terial and cement. They are extremely well satisfied with them, 
 and get a larger output with them than the Americans. However, 
 some improvements have been made on the mills. Recently two 
 large Fuller mills were started running at Heidelberg; the trials with 
 them have not yet been concluded. In Germany the Kominor with 
 the tube mill is most met with, though this does not by any means 
 prove that this system of grinding is especially economical. But, 
 on the other hand, the ball and tube mill is a very reliable method of 
 grinding, and it requires little attention. 
 
 It will interest you to know that in Germany experiments have also 
 been made with burning the material before grinding. It was also a 
 success when the raw material was crushed to 1-inch lumps. This burnt 
 raw material proved, however, very difficult to grind. The output 
 of the mills was reduced by one-half, and on this account the matter 
 was not followed up. In any case the burning of the raw material 
 is nothing new. 
 
 On the other hand, I have seen in another factory the very soft 
 and wet material similar 10 that in Sandusky being dried in a 
 rotary drier 120 feet long and 6 feet 6 inches in diameter and slightly 
 burnt at the same time. In front of the furnace there is a special 
 combustion chamber. The firing is done with coal-dust. This 
 factory, which formerly could never get its raw material dry, is now 
 working very successfully. 
 
 The mixing of the raw material in most factories in Germany 
 differs from the American method. The arrangement you have here 
 in many places, of weighing the clay and the lime and then mixing 
 it, is rarely met with in Germany. 
 
 Most works are able, on account of their favorable raw material, 
 to make approximately the correct composition and mixing in the 
 pit, where the removing of the raw material is done exactly in accor- 
 dance with the instructions of the chemist. The chemist knows 
 exactly which layers contain more lime and which contain more clay. 
 In accordance therewith he has the proper proportion of clay and 
 lime sent up. In the German works the chemist takes the first place, 
 and he also supervises the whole of the machine plant. You will 
 therefore mostly find at the head of the cement works in Germany a 
 
so-called technical chemist, who has a few assistants at his disposal 
 in the laboratory. Every two hours the percentage of lime in the 
 raw material is determined in the laboratory, and according to 
 whether it turns out high or low, instructions are given to send up 
 more clay or more lime. Frequently it is not necessary to make any 
 change for days together, as the lime and clay strata are fairly uni- 
 form in their composition. No importance is attached to the mixture 
 being absolutely even as it comes from the quarry, as usually the real 
 mixing is done only after the grinding of the raw material. For 
 this purpose there are large mixing silos, which hold 25,000 barrels 
 and which are filled up in regular layers during the course of a week, 
 and are then mixed together when withdrawing the ground material. 
 The ground material can be laid in horizontal or vertical layers. A 
 small example will best illustrate this. 
 
 A factory has to adjust its mixture to from 76 to 77 per cent, 
 carbonate of lime. The ground material is passed for seven days 
 into the same bin, and care is taken to spread the ground material 
 in uniform layers by means of suitable conveying machinery. 
 
 If the material has been stowed in horizontal layers, the different 
 layers fall together when emptying the bin, and so give an average of 
 76.6 per cent, carbonate of lime. 
 
 With vertical layers the conveyor is placed under the bin, and the 
 material is allowed to run regularly into it from each layer through 
 special openings, and by this means an average of all the different 
 layers is obtained. As the composition of each layer is determined 
 daily in the laboratory, a calculation can be made in advance as to 
 what the average of the seven layers will be. There are usually two 
 bins, and while the one is being emptied the other is being filled. 
 The great advantage of this mixing plant is that very large quantities 
 are mixed together, by which great uniformity is obtained. Besides, 
 no machinery is required and the making of the proper mixture is 
 entirely in the hands of the chemist. 
 
 In Westphalia the raw material has naturally nearly the correct 
 composition, and the ground material is only once more passed 
 through a mixing machine. 
 
 The burning of the cement is to-day done in rotary kilns in two- 
 thirds of the German factories. Vertical kilns and Hoffmann ring 
 kilns are still found, but only in places where wages are very low. As 
 the latter do not come into question in America, I will not dwell 
 upon them. Regarding the construction of the rotary kilns, they 
 differ only slightly from the American kilns. The first kilns were 
 
 10 
 
built 81 feet long and 6 feet diameter, but the length was gradually 
 increased to 120 feet, and recently kilns have been erected 150 feet 
 long. These are the longest up to the present. People in Germany 
 are not yet quite clear as to whether the long kilns are better, espe- 
 cially as they have been able to use the waste heat with advantage 
 for other purposes. The economy of a kiln and not the output turns 
 the scale in Germany, and people would sooner put up two kilns of 
 smaller capacity, if the burning can be done therewith more economic- 
 ally than with one large kiln. 
 
 Fig. 6. Dreadnaught-Kiln; 240 feet Long, 10.5 feet Diameter. 
 
 The engineering works, it is true, recommend long kilns, 250 feet 
 feet in length and 9 feet in diameter, as with these the end gases have 
 a temperature of only 200 centigrade, and the heat is best utilized in 
 these long kilns. But no kiln of such length is in operation in Germany. 
 
 In Germany, where, as you know, fuel is very dear, it was 
 sought from the commencement to utilize the heat as much as 
 possible. On this account each rotary kiln is provided with a cooler, 
 in which the clinker is cooled by drawing air through it. The same fan 
 which blows the coal-dust into the kiln draws the air through the 
 cooler, which is thus heated to 250 centigrade. Thus the fuel is 
 saved which would be required to heat the large quantity of air 
 
 n 
 
required for burning to 300 centigrade. Many works also use this 
 hot air to dry the coal. Coolers with a double casing have also been 
 constructed, so that the clinker, after having passed through the inner 
 cylinder, is led back through the outer cylinder, and so perfectly 
 cooled. The air, which in this case is forced from the front into the 
 cooler, reaches a temperature of 300 centigrade. 
 
 One company uses water very successfully for cooling the cylinder, 
 the hot water being utilized for feeding the boilers and for the bathing 
 arrangements of the workmen. 
 
 Fig. 7. Installation of Fourteen Rotary Kilns; Largest Installation in Germany, 
 Producing 4500 Barrels a Day. 
 
 The waste heat is utilized in three ways either to dry the raw 
 material, to warm the air for the kilns, or to raise steam in the 
 boilers. 
 
 When drying the raw material with the waste gases from the 
 kilns, the difficulty for a long time was that considerable dust and 
 fine material went out of the chimney, but this is now arrested by 
 water, producing mud which is burnt under the kilns. 
 
 When the waste gases are utilized for heating the air of com- 
 bustion, there are built behind the kilns so-called blast-heaters, 
 
 12 
 
Fig. 8. Rotary Kiln for Thick Slurry in the Weisenau Plant near Mainz, Ger- 
 many. A double cooler with cooling by compressed air is shown below kiln. 
 
 Fig. 9. Rotary Kiln Installation for Thick Slurry Process. Kilns 150 feet long, 
 9 feet diameter. A newly patented shaker is shown at the end of the kilns. 
 
 13 
 
which are said to heat the air to 600 centigrade. Many attempts 
 have been made to utilize the waste gases for raising steainy but 
 in most cases without success, as no means were known of keeping 
 
 Fig. 10 Coal-feeder and Fan for Rotary Kiln. 
 
 the dust from the tubes of the boilers. However, three factories 
 are to-day using the waste gases of the kilns for raising steam. Two 
 of these factories have kilns 90 feet long, while one uses kilns 120 
 
feet long. The production of steam even with the 120-foot kiln is 
 satisfactory. The steam raised by the waste heat not only suffices 
 to drive the whole of the rotary kiln plant and the coal mill, but also 
 furnishes the power for the larger part of the raw mill. However, 
 special devices of a rather simple nature must be used to keep the 
 dust from the boilers. 
 
 The injection of the coal is done by fans, which, as I have already 
 mentioned, draw the air from the coolers. In order to obtain perfect 
 and uniform combustion the coal-dust is fed into the air-current of 
 the fan by means of a system of double worms. By this means the 
 
 Fig. 11. Concrete Lining of a Kiln. 
 
 same effect is said to be arrived at as that aimed at by Dunn's uni- 
 form pulverized fuel feeder. But according to my observations the 
 problem appears to be better solved by Dunn's apparatus. 
 
 Compressed air is not used in Germany for injecting the coal-dust. 
 Experiments therewith showed no benefit. The pipes through which 
 the coal is injected are generally wider than here usually 8 inches. 
 
 The clinkering zone is 13 to 16 feet distant from the head of the 
 kiln. 
 
 The lining of the kilns is done either with adhesive sandbricks, 
 firebricks, or bricks made of clinker and cement. 
 
 Adhesive sandbricks are useless unless a crust is formed in the kiln, 
 
 15 
 
as otherwise the hard clinker causes heavy wear. But if a protective 
 layer of clinker is deposited, then they are the cheapest kiln lining. 
 
 In some factories attempts have been made to simply line the 
 kilns with concrete made of a mixture of rotary kiln clinker and 
 cement. It has been found that the concrete in the kiln will last a 
 long time (one year), if the kiln is allowed to stand a few days after 
 the lining, so that the concrete can harden properly. 
 
 As you are aware, a patent has been taken out in Germany for a 
 so-called widened clinkering zone. According to this patent, the 
 front part of the kiln, in which the clinkering proper takes place, 
 
 Fig. 12. Burner-stand with Fans and Pipes. 
 
 and which otherwise was only 6 feet 6 inches in diameter, is enlarged 
 to 8 feet 2 inches diameter. It is asserted that by this the output 
 of the kiln is increased and the coal consumption reduced. It is 
 very difficult to get an opinion on this point from actual experience. 
 The manager of a factory who works with such kilns told me the only 
 advantage he saw was that a very thick crust formed in the widened 
 part and protected the kiln-lining very well. In general, the ad- 
 vantages of the widened clinker zone are not yet clear, and preference 
 is given to a kiln the diameter of which is at the outset made wide 
 enough in its entire length. 
 
 16 
 
Whereas formerly the opinion prevailed that the ground raw 
 material should be moistened before being ^ed into the kiln, many 
 factories have found out a device to burn the dry material. The 
 material falls direct from the conveyor through a pipe into the kiln. 
 By this means the mixing worm, which required attention and much 
 power, is no longer required, fuel is saved, and the output of the kilns 
 is increased by being fed with dry material. Rotary kilns without 
 coolers are not found in Germany, and vertical coolers are also 
 unknown. 
 
 Fig. 13. Cooler, Weighing Machine, and Shaking Conveyor. 
 
 The cooling-cylinders are always placed under the kilns and above 
 the floor. The foundations of the kilns are therefore much higher 
 than is usually the case in America. 
 
 The lubrication of the bearings is done with calypsol grease. 
 Some works have central lubrication, by which eight to ten bearings 
 are automatically greased by a grease pump. 
 
 In general, three kilns are attended to by one burner. Ordinary 
 workmen are usually trained as burners, and on account of their easy 
 work they are paid comparatively low wages. Most works train two 
 
 17 
 
or three times more men as burners than they require, and set them 
 to other work. 
 
 When the waste heat of the kilns is used for raising steam in the 
 boilers, one man can attend to six boilers, his sole duty being to feed 
 the boilers with water. 
 
 The front end of the cooler is perforated like a screen to sort the 
 clinker, and only the coarse clinker requires to be crushed for the 
 cement mill. In front of each cooler an automatic weighing machine 
 is placed, which also makes automatic records, so as to afford an exact 
 check on the output of each kiln. The coal-dust for each kiln is 
 weighed in the same manner, and coal consumption and output are 
 noted hourly on a special board. 
 
 We now have in Germany a drum weighing machine, with which 
 everything can be weighed pulverized coal, cement, and hot clinker. 
 It is very exact and reliable. 
 
 As regards conveyors, preference is given in Germany to the belt 
 conveyor and to the worm or spiral conveyor. For hot clinker the 
 so-called shaking conveyor is much used, and it has proved very 
 satisfactory; it is not the type oscillating on wooden spring legs, 
 however, but a shaking trough running on small wheels. This con- 
 veyor can transport any quantity, even up slight inclines. I know 
 of a factory which formerly took the clinker away in tip-cars, and 
 now saves fifty workmen after installation of a shaking conveyor. 
 
 Some large works have so-called clinker stores, where the clinker 
 is stored and allowed to season. 
 
 The clinker is raised by means of a bucket elevator to a height of 
 about 33 feet, and then distributed over the store by means of a 
 shaking conveyor, which is designed to drop the clinker in different 
 places. The removing of the clinker from the store to the cement 
 mill is also done by means of such a shaking conveyor placed in a 
 channel under the clinker store and covered with boards. When 
 the boards are taken up (which one man can do) the clinker falls from 
 the store into the conveyor and is carried away. 
 
 The storing and seasoning of the clinker has many advantages. 
 In the first place, the clinker, being dry, grinds better, and the large 
 lumps become soft through storage and easily break. Further, the 
 storage is good for the quality of the cement, and greater uniformity 
 is obtained by being able to again mix the burnt product of several 
 days before grinding. 
 
 The cement mill in a German works has the same appearance as 
 
 18 
 
in American works. Ball-mills, Kominor, tube-mills, Fuller mills, 
 and Griffin mills are used. 
 
 The finished ground cement is stored in large square bins of 25,000 
 to 100,000 barrels. Preference is given to the largest bins possible. 
 This is to get, when withdrawing the cement, as large a quantity as 
 possible, by which great uniformity is obtained. Round concrete 
 silos, which of late are frequently met with in America, are seldom 
 used in Germany. On the other hand, a large stock of cement ready 
 packed in bags is kept, the bags being piled twenty-five high. 
 
 The piling of the sacks is done by a band conveyor. 
 
 Fig. 14. "Solomill" for Cement Grinding; a Combination of Ball- and Tube-mill. 
 
 For packing, the automatic twin scales, system iron-work Ahle- 
 feld, are much used, which weigh very correctly. Capacity, 1800 
 bags in ten hours. 
 
 Last year I heard that certain American cement manufacturers 
 who had visited German cement works expressed astonishment at 
 the primitive way in which the cement is packed and loaded in 
 Germany. I presume that the gentlemen in question had only visited 
 some unimportant cement works. 
 
 With the high wages of $1.25 to $1.50, which have to be paid in 
 Germany to men in the packing house, you will find to-day well 
 
 19 
 
designed plants in the larger cement works. I will give you a de- 
 tailed description of one. 
 
 The storage house is built so that thirty railway cars go direct into 
 the middle of the house on two tracks running side by side. The 
 room in which the cement is packed is situated on the second floor 
 directly over the railway cars. The cement is taken from the bins 
 by elevators and conveyors to the thirty automatic packing machines 
 on the second floor, where it is put into bags. The workmen who 
 fill and tie the bags simply let them slide from the second floor down 
 curved tubes, which may be turned around, and which lead into the 
 opened railway wagon. In each case there is a man who takes the 
 
 Fig. 15. Clinker Store-house with Shaking Conveyor. 
 
 bag from the tube and drops it into its place. The packers on the 
 second floor fill the bags as quickly as the man down in the wagon 
 can stow them. 
 
 In other works where the railway siding is a long way distant 
 from the packing shed, a belt conveyor leads from the packing shed 
 to the railway cars, and the bags slide down an inclined chute directly 
 into the car, where they are stowed by one man. The belt conveyor 
 runs directly in front of the packing machines on a level with the 
 floor, so that the workmen can lay the bag directly on the conveyor 
 as soon as it is filled and tied up. If six automatic scales are at work, 
 
 20 
 
the bags follow one another on the belt conveyor at intervals of 
 feet, and a car can be filled in ten minutes, though I should here 
 remark that the German railway cars do not hold more than 300 bags. 
 
 A special arrangement for packing cement, invented and intro- 
 duced by the firm of Smith & Co., has been running in some works 
 for about a year. The cement is put into the bags by vacuum. 
 
 Gentlemen, you are aware that Germany exports one-tenth of 
 its production. Exports are chiefly from the factories which lie 
 on the coast and the big rivers. As cement is only exported in 
 barrels, all these works have a special cooperage and packing plant 
 for barrels. In order that the barrels may withstand a long oversea 
 voyage, the cement must be tightly pressed. In most factories the 
 packing of these barrels is done by hand, the filled barrels being well 
 beaten with clubs until the cement has thoroughly settled. But 
 there are also machines for this work. The barrel stands on a 
 revolving plate and is kept rotating while receiving a number of 
 powerful shakes from a mechanical device. In order to render them 
 perfectly water-tight, the barrels are lined with water-tight paper. 
 
 The making of these barrels forms a special department, which, 
 on account of its liability to catch fire, is usually in a building 
 separated from the other buildings. In Heidelberg, for instance, over 
 a hundred workpeople are employed in this department. With 
 the exception of the putting on of the wooden hoops and the fitting 
 of the lids, the barrels are all made by machinery. The large works 
 have their own saw mills, where the wood, as it comes from the forests, 
 is sawn into cylindrical staffs, grooved, molded, and fitted together 
 by special machinery. The making and putting on of iron hoops is 
 also done by machinery. 
 
 Bags made of jute are mostly used, rarely of canvas. Paper bags 
 are still too dear in Germany and therefore not used. The cleaning 
 of the bags is done in the same way as in America, namely, in large 
 revolving drums. Electric sewing machines, with dust exhausters, 
 are used for sewing and mending. It will interest you to know that 
 a group of twenty cement works in Westphalia have a so-called "bag 
 central," where new bags are made and the old ones cleaned and 
 repaired. The empty bags are sent by the customers to the "cen- 
 tral," where they are sorted, repaired, cleaned, and returned to the 
 different works. 
 
 The cost of the whole work does not amount to quite half a cent 
 per bag. Only women are employed for mending. 
 
 The same group has also its own barrel factory, in which the bar- 
 
 21 
 
rels for about twenty works are made. This, of course, can be done 
 only when the works are close together. 
 
 As the German cement works are mostly somewhat old, you will 
 find in them, in contrast to American factories, long, complicated 
 line-shafting, from which the mills are driven. Compared with 
 America, the motor drive is much rarer, but it is gradually being 
 introduced, especially in the more recent works. The firm of Dycker- 
 
 Fig. 16. The Music Hall under Con- 
 struction. 
 
 Fig. 17. The Music Hall Inside with 
 the Stage. 
 
 Fig. 18. Swimming Bath for the Laborers. 
 
 hoff has installed in its new works steam-turbines, and for driving the 
 grinding machinery nothing but motors. 
 
 For raising steam you will find all boiler and stoking systems 
 represented. The stoking is mostly automatic. 
 
 The Leimen factory has a swimming bath 100 feet long by 50 feet 
 wide for the workpeople. Slipper-baths and shower-baths are con- 
 nected with it. The picture shows you that it has been fitted up 
 
 22 
 
rather luxuriously in order to encourage the workpeople to make use 
 of it. 
 
 The same works built a music hall two years ago for the workmen, 
 in which they hold their festivities every week. Connected with it 
 there is a " kindergarten," a library, and a reading-room. 
 
 Gentlemen, the same as here in America, many factories have 
 built houses in the neighborhood of the works, in which the work- 
 people can live at a low rent. Recognizing that it is a great ad- 
 vantage for a factory to have old, well-trained workmen, they 
 are given every consideration. Almost every factory has its own 
 
 Fig. 19. Cement Factories in Leimen near Heidelberg. In the foreground is 
 shown a Music Hall and Houses for the Laborers. 
 
 sick fund, saving club, pension fund, eating houses, and canteen. 
 It is nothing unusual for workmen to remain twenty-five to forty 
 years in one factory. Following the example set by America, almost 
 every factory has its own repair shop, and at the Portland Cement 
 Works of Heidelberg and Mannheim, for instance, the repair shop is 
 as large as an engineering works. Not only are all repairs and 
 improvements on mills and machinery made there, but the works 
 have their own foundry, to which a steel foundry is now being added. 
 New machinery is also made there; it is a sort of experiment station 
 for new ideas. 
 
 23 
 
As far as I can judge, the cost of production is lower in Germany 
 than in America, and for this the lower wages are not alone respon- 
 sible. To counterbalance this, fuel is dearer in Germany. But the 
 German does more calculating; he tries to save every cent, and makes 
 full use of every advantage, as, for example, the temperature of the 
 waste gases, new conveyors, etc. But what gives a special advantage 
 to the different works are the monthly actual cost calculations, which 
 show clearly and to the smallest detail how high the actual cost is 
 in every single branch. The art of correctly calculating the actual 
 costs, of studying the same, and drawing from them the proper con- 
 clusions as to where the lever should be applied to lower the cost of 
 production, this art enables many factories to manufacture much 
 cheaper than others, who otherwise are just as favorably placed. 
 
 A well-managed works sees from this statement of actual costs 
 where faults are to be corrected, and is urged by it to make the cost 
 still cheaper in the following month by the application of improve- 
 ments and by making use of certain advantages. And in this manner 
 people have managed in Germany continually to reduce the actual 
 cost of a barrel of cement, in spite of higher wages and dearer fuel. 
 A limit will no doubt be reached in time, but from what I have seen 
 my conviction is that in America you are much further from this 
 limit than in Germany. The Germans have taken lessons from the 
 Americans with regard to their kilns and grinding machinery; let 
 the Americans learn from the Germans how to make use of everything 
 in order to save every cent and make cement as cheap as possible. 
 
 I cannot predict offhand which will eventually prove to be more 
 advantageous for America, the wet process with thick slurry or the 
 dry process. But it is possible that in America the wet process may 
 prove cheaper, because fuel is considerably cheaper than in Ger- 
 many, and therefore the cost of burning the cement, which in any 
 case is higher with the wet process than with the dry, may not be 
 of so great account. 
 
 As I am aware that the American cement industry is greatly 
 interested in the wet process, I will say a few words about it at the 
 close of my lecture. 
 
 Many of the works situated in the north of Germany make their 
 cement from the chalk on the coast and on the Baltic islands, and 
 are forced to use at the same time a clay containing much sand 
 and flint, and they have, like most of the works in England, 
 always given preference to the wet process. Chalk and clay contain 
 naturally a high proportion of moisture, and are also so soft that they 
 
 24 
 
can be reduced to the requisite fineness without mills, simply by wash- 
 ing. In these factories the raw materials are washed very thin with 
 about 80 per cent, of water, and, according to the arrangement of 
 the plant, the stones and the coarse sand either settle to the bottom 
 as the heavier constituents, or they are separated from the thin 
 slurry by screens. The slurry runs from the washing basins into large 
 settling basins, where it is allowed to settle. The water collecting 
 on top is let off from time to time, and the sun and air help gradually 
 to dry out the water remaining in the slurry until it becomes stiff 
 enough to be dug out with a spade and pressed into bricks for the 
 shaft or ring kilns, which are still used by most of the factories that 
 work on the wet process. Some of these factories, however, have 
 recently installed rotary kilns, and pump the slurry containing 40 to 
 55 per cent, water direct from the settling basins into the kilns. It 
 is often months before the slurry gets the consistency desired, and 
 it is certainly a disadvantage of this wet process that so much time 
 is lost before the product made months ahead can be actually turned 
 to value. Enormous values are often represented by this half- 
 finished product. 
 
 The wet process is considerably more advantageous, when pure 
 chalk and clay are to be had, and it is not necessary to pay attention 
 to eliminating impurities in the shape of quartz sand and flint. 
 The addition of 40 per cent, water then suffices to grind the material 
 in the wash-mills. This slurry is then simply run into the so-called 
 mixing basins, where it is stirred up until the mixture is uniform. 
 It is not necessary to thicken further this 40 per cent, slurry, and 
 it can be pumped direct to the kilns. 
 
 With these two ways of wet preparation it is presumed that the 
 chalk and clay are naturally so soft that no special mills are necessary 
 for grinding. 
 
 But it should especially interest you in America that recently 
 some works have started to prepare hard materials like limestone 
 in the wet way by using special mills. This so-called thick slurry 
 process has so far been introduced in Germany into seven factories, 
 of which I inspected five during my last stay in Germany. 
 
 Before I give you a full explanation of why, according to the opin- 
 ion at present prevailing in Germany, thick slurry preparation is to 
 be preferred to dry preparation, I should like to give you a short 
 description of the working of a thick slurry plant. 
 
 Such a plant is mostly built in four stories, one above the other. 
 
 The material comes from the pit to the top floor. The large 
 
 25 
 
pieces of limestone are here crushed to the size of a fist and fall directly 
 onto the wet-kominors placed below. The soft wet clay and marl 
 are fed directly into this wet-kominor, and roughly ground with the 
 addition of water. The rough slurry, which has 35 to 45 per cent, 
 moisture, runs into the wet tube-mills, which are placed in the floor 
 below under the wet-kominors, and here it is ground quite fine. The 
 factory has, according to its size, a number of large mixing basins, 
 which lie below and in front of the wet tube-mills, and the slurry 
 runs through pipes into these basins. A factory producing 1000 
 
 G.Potysii 
 
 Fig. 20. Triple Mixer with Practicable Gangway all Round. 
 
 barrels daily requires at least four mixing basins of 500 barrels capacity 
 each. As soon as a basin is three-quarters full, the mixture is made 
 by testing the slurry every two hours and then grinding material 
 either richer in clay or richer in lime and allowing it to run into the 
 basin. The final adjustment can also be done by letting the slurry 
 run from one basin into the other. The mixing basins are usually 
 oval in shape; three stirrers run in each basin to keep the slurry 
 in constant motion and mix it. 
 
 The slurry is then pumped by means of special pumps to small 
 slurry bins over the kilns, and is burnt in the rotary kiln in exactly 
 
 26 
 
the same manner as dry material. The feed pipe to the kiln must 
 be steep and wide, so that it does not choke. A difficulty with the 
 burning is that the slurry is apt to roll together into large balls, which 
 pass through the clinkering zone too quickly and do not get thoroughly 
 burnt inside. These are called " runaways." 
 
 The kilns for the thick slurry process have in Germany generally 
 a length of 122 to 148 feet, and are 7 feet 6 inches to 8 feet 2 inches 
 diameter. Only the kilns in the Dyckerhoff works are longer 150 
 feet long and 9 feet in diameter. Otherwise they are exactly the 
 
 G.Potysms, Dessau. 
 
 30/17. 
 
 Fig. 21. Slurry Storage and Mixing Tanks, with Feeders, and Slurry Worm 
 Conveyor above the Rotary Kilns. 
 
 same as kilns for the dry process. The clinker is just as hard as 
 the clinker made from dry material, and there is no difference in 
 the further process of manufacture. Last year I often heard the 
 view expressed here in America that people in Germany were 
 going over to the thick slurry process quite generally. This is a 
 mistake. As I have already told you, there are at the present time 
 in Germany only seven such works, and with all of these special 
 reasons led to the introduction of the thick slurry process. Two of 
 these works used the wet process from the beginning. At the moment 
 
 27 
 
only a single factory is altering its plant to the wet process, and 
 from this you may see that the majority of the German cement makers 
 still consider the dry process better, and in any case more econom- 
 ical. Only very special reasons, such as peculiarities of location 
 or a naturally very wet raw material that could not be dried, 
 have induced the German cement maker to introduce the thick 
 slurry process in a few places, although three engineering works 
 are already making wet mills, and on this account are, of course, 
 advocating the wet process. The best German cements with the 
 highest degrees of strength are still the cements made with the dry 
 process, so the question of quality is no inducement to go over to the 
 wet process. With proper attention just as good cement can be 
 made in the dry way as in the wet, if the correct arrangements are 
 made for a thorough mixing. Still there may be instances where 
 the wet process is to be preferred to the dry, but such cases can only 
 be decided separately after a thorough testing of the raw material. 
 I will give you the points of view to be considered before deciding, 
 especially in Germany, where fuel is very dear and forms a consider- 
 able part of the cost of manufacturing. In this respect the position 
 in America may differ somewhat, as you have cheap coal and oil at 
 your disposal for burning the cement. But if you can save only a 
 few cents a barrel with the dry process compared with the wet process, 
 then here, too, you must give the preference to the dry process of 
 making cement. 
 
 The economy in burning cement in rotary kilns depends on the 
 following four points: (1) Cost of the installation; (2) wages; (3) 
 power consumption; (4) coal consumption. 
 
 The cost of plant is undoubtedly lower for the wet process, as 
 various arrangements are not required which are necessary for the 
 dry process. No rotary driers are required nor bins for ground raw 
 material, the latter being substituted by the cheaper mixing basins. 
 There is not required for the wet process the dust-collecting ar- 
 rangements for the raw mill. The buildings for the dry process also 
 take up rather more room. The opinion that with the wet process 
 the kilns would have to be longer and larger has proved wrong, so that 
 with the dry process the same cost of installation has to be taken 
 into account for the kilns as with the wet process. However, the 
 extra cost of a dry plant compared with a wet plant is not as much 
 as might be assumed from the foregoing. It amounts to 3 to 5 per 
 cent, on the complete plant, and plays no great part when calculated 
 on the barrel. f/- 
 
In America an important consideration is whether the wet pro- 
 cess will reduce labor costs. According to the experience in Germany, 
 this is not the case. As many people are required for attending 
 to the wet grinding machines and the mixing basins as with the 
 dry process for attending to the mills and ground material bins. 
 The power consumption of the mills is generally lower with the wet 
 process, especially with materials which are not of a hard nature, 
 such as marl, clay, chalk, etc. With such stuff the washing with 
 water is effective and divides the material into its finest parts, so 
 that the mills have little work to do. But it is a different thing 
 if hard limestone and shale are to be ground wet, as the water is 
 then of no assistance, and the mills have to do the same work as 
 with the dry process. The economy in power is then very low and 
 out of proportion to the higher coal consumption necessary to evapo- 
 rate in the kiln the added water; and the higher the proportion of 
 water in the slurry, the higher the coal consumption naturally is. 
 
 In judging the relative economy of the two systems, the main 
 question is the coal consumption. Because, as the situation lies in 
 Germany, coal is the chief factor in the actual cost of manufacture, 
 amounting from one-third to one-half of same, according to price 
 and other circumstances. Thus when making cement consideration 
 must be given in the first place to saving coal. 
 
 Most of the factories with the thick slurry process work with a 
 40 per cent, proportion of water. It depends on the nature of the 
 raw material whether more or less water must be added. Occasion- 
 ally slurry with 45 per cent, water is still so stiff that it can hardly 
 be pumped. There are works which burn even 55 per cent, slurry 
 in the rotary kilns. 
 
 With 55 per cent, water there has to be evaporated 190 parts of 
 water to 100 parts of finished cement, which is a very unfavorable 
 ratio. With a thick slurry containing 40 per cent, water the ratio 
 is much better, but 104 parts of water have still to be evaporated 
 to 100 parts of cement. It is clear that an increased expenditure of 
 coal is necessary to burn cement out of a material containing so much 
 water. Experience has shown that with the kilns mostly used in 
 Germany, 115 to 148 feet long and 7 feet 2 inches to 8 feet 2 inches 
 in diameter, the burning of a slurry containing 35 to 40 per cent, 
 moisture requires in round figures for every 100 kilos of cement 5 
 kilos more coal of medium quality than the burning of a slightly 
 damped ground raw material, including the preliminary drying of 
 material from the quarry with the average moisture in the pit. 
 
 29 ' 
 
The bill for fuel is therefore increased by fully 20 per cent, with 
 the wet process. 
 
 These figures thus result from the comparison of the burning of 
 thick slurry and dry raw material in kilns of the same length and 
 diameter, and after taking into account the amount of coal required 
 by the dry process for drying the raw material before grinding. 
 Besides this, the dry ground raw material was moistened with 8 to 
 10 per cent, water before burning. All these are very unfavorable 
 conditions for the dry process. In a properly managed kiln plant 
 with the dry process the result will turn out much more unfavorable 
 to the wet process than I have shown to you. 
 
 In the first place, it is not necessary to damp the raw meal with 
 8 to 10 per cent, water when running it into the kiln. Some factories 
 have long had a device which renders it possible to burn directly 
 the dry meal, so that the fuel for evaporating this 8 to 10 per cent, 
 water can also be saved. There has also btei left out of considera- 
 tion the fact that with kilns 115 to 148 feet in length the waste 
 heat when burning thick slurry only amounts to 250 centigrade, 
 whereas with the dry process the waste heat has a temperature of 
 500 centigrade and over. As I have previously explained to you, 
 this waste heat can be utilized for warming up the air of combustion 
 in blast-heaters, or, better still, for raising steam in the boilers. 
 On the other hand, when burning thick slurry the heat produced by 
 the fuel is all used up in evaporating the water, so that the waste 
 gases have a temperature of only 250 centigrade, and cannot be 
 further utilized. 
 
 But it is precisely the utilization of the waste heat that enables 
 further economies to be made, which I estimate very high if properly 
 planned. The firm of Polysius, in Germany, which, as the first fac- 
 tory for the construction of rotary kilns, has much experience in 
 this line, explained a year ago, through their Director Bruhn, the 
 advantages of the dry process in a lecture given at the meeting of 
 the German Portland Cement Makers, and the theories set forth 
 coincide exactly with the statements made by me to-day. Dr. 
 Bruhn also comes to the conclusion that the dry process is to be pre- 
 ferred to the wet process, unless the raw material has naturally more 
 than 15 per cent, moisture and by its softness is specially suitable 
 for wet grinding and washing. This firm builds at the same time 
 wet mills and kilns for thick slurry. 
 
 But Dr. Bruhn is not of my opinion that it is best to utilize the 
 waste heat for the driers or boilers, as this makes the plant compli- 
 
 30 
 
cated, and he recommends building the kilns of such a length that 
 all the heat is thoroughly utilized in the kiln itself in burning the 
 raw meal, so that the waste gases have a temperature of only 250 
 centigrade. It was ascertained by experiments that to fulfil these 
 conditions a kiln must have a length of 262 feet by 8 feet 2 inches 
 diameter. 
 
 When the firm of Polysius now builds new works, it seeks to 
 introduce these long kilns, which are said to reduce the coal con- 
 sumption and to increase the output of the kiln. 
 
 However, the wet preparation has in any case several advan- 
 tages, the principal of which is that the plant is much simpler with 
 wet grinding, and the adjustment of the proper mixture is easier 
 with thick slurry than with raw meal. Any mistakes can be cor- 
 rected without difficulty in the mixing basins. But I do not mean 
 to say that on this account the quality of cement burnt from thick 
 slurry is better than that made from raw meal. With the employ- 
 ment of proper mixing arrangements and with care the same uni- 
 formity and accuracy in the composition of the raw meal can be at- 
 tained with the dry process. When this is not the case, it is not the 
 method but the arrangements that are at fault. 
 
 The disadvantage of the thick slurry process is thus undoubtedly 
 in the extra expenditure in fuel and the increased cost of manufacture 
 caused thereby, which will become the more palpable in comparison 
 with the dry process when the burning of dry meal and the utilization 
 of the waste heat are properly understood. 
 
 On the other hand, the thick slurry plant has some advantages 
 which may be briefly stated as follows : (1) Smaller capital investment 
 in the installation. (2) Little dust. (3) The possibility of proper 
 adjustment of the mixture without difficulty. (4) A simpler plant 
 and fewer conveyors. (5) Saving of power in wet grinding. 
 
 The saving in power is very small, however, and is not nearly com- 
 pensated for by the larger expenditure in coal required for the burning 
 of the thick slurry, and it would not be right, therefore, to give the 
 wet process the preference over the dry on account of the saving 
 in power. Dr. Bruhn gave in his lecture last year the following 
 explanations, which will show you the position clearly: "With our 
 steam-engines of to-day 0.7 kilo of medium quality coal is sufficient 
 to produce 1 horse-power-hour. With kilns of equal length, 5 kilos 
 less coal per 100 kilos clinker are used when burning raw meal than 
 when burning slurry containing 35 to 40 per cent, water. These 
 5 kilos of coal are thus equal to 7 HP-hours. With a production of 
 
10,000 kilos per hour, equal to 300,000 barrels per year, this higher 
 consumption of fuel in the thick slurry kiln is equivalent to a constant 
 higher expenditure of 700 PS per hour. But the whole plant for 
 this production only requires some 300 to 400 HP for crushing, drying, 
 and grinding the raw meal." 
 
 Gentlemen, I can only confirm this from the experience made 
 by a company to which I formerly belonged, and which altered one 
 of its works to the thick slurry system. The factory in question 
 works at much greater cost than the other factories with the dry 
 process. 
 
 It is very difficult to give a general opinion as to whether the 
 dry process or the wet process is more advantageous. Where err- 
 phasis is placed on having a plant as simple as possible, and that 
 can be easily supervised, or where there are difficulties in attaining 
 a good mixing with the dry method, in such cases the wet process 
 is perhaps suitable, even if the raw material is naturally hard and 
 not too damp. But in any case it must be taken into account that 
 the cost of manufacture will be considerably higher than if the same 
 material were worked dry. The method of making is certainly simple 
 and easy, but it costs more. 
 
 It is somewhat different if the materials are naturally soft or 
 impure and contain much moisture, so as to render the drying difficult. 
 In such a case the wet process would be preferable. As far as I had 
 the opportunity of examining the raw materials used in America for 
 making cement, I am convinced that most of them are more suitable 
 for the dry process than for the wet process. 
 
 I have already mentioned that a cement works in Germany is 
 now about to change from the dry process to the wet; the reasons 
 are that the factory in question has to work a clay containing 15 
 per cent, moisture, and adds 12 per cent, water to the raw meal before 
 it runs into the kiln. Under such circumstances the superintendent 
 said that it did not matter so much whether he added a further 10 
 per cent, water and introduced the thick slurry system, especially 
 as he was never able to dry the clay properly. But I know of another 
 works which is at present making alterations, but is retaining the 
 dry system, although the clay contains nearly 20 per cent, water. 
 The works in question has constructed for itself a special cylinder 
 drier with coal-dust firing, and as they know how to burn the raw 
 meal dry, I do not doubt that this factory will manufacture cheaper 
 than the other factory with the thick slurry system. You see, 
 gentlemen, that also in Germany the question as to whether the wet 
 
 32 
 
or dry process is better has not been sufficiently cleared up. My 
 personal view is that wet preparation should only be chosen if the 
 raw materials are not hard or plastic, and if the natural proportion 
 of moisture already approaches that necessary for wet working. I 
 consider it a mistake to work hard, dry material according to the 
 wet process simply for the purpose of facilitating the mixing or of 
 avoiding the dust. For to solve both these problems it is not neces- 
 sary to introduce the more expensive wet process; it can be done 
 just as well with the dry process. 
 
 I hear that a factory is being changed in America to the wet 
 system, and it will then be seen whether the wet system is pref- 
 erable for your country, which is not impossible, as fuel does not 
 play such a large part in the cost of manufacturing as with us in 
 Germany. 
 
The Laboratory of the Association of Ger- 
 man Cement Makers and the New 
 German Rules for the Uniform Test- 
 ing and Delivery of Portland Cement. 
 
 BY DR. OTTO SCHOTT 
 
 When in the year 1877 the representatives of the German cement 
 industry, which at that time hardly produced two and one-half 
 million barrels, joined together to form an Association of German 
 Cement Makers, this association set itself the task of furthering all 
 interests touching the Portland cement industry, and of contributing 
 by scientific work to the knowledge of the properties of Portland 
 cement. How energetically it went to work is probably best seen 
 by the rules it laid down on a scientific basis in the same year for 
 uniform methods of testing Portland cement, and which have become 
 a pattern for the cement industry of the whole world, although they 
 have undergone many changes in the course of time. Notwithstand- 
 ing that Portland cement had been made in England for fifty years, 
 it is rather remarkable that this was the first attempt, with the help 
 of experience and researches made up to that time, to lay down 
 uniform methods for the testing of Portland cement. This meant 
 immense progress for the cement industry, as the users of cement were 
 thereby enabled to test and work the cement in a proper manner, and 
 to judge the quality correctly. 
 
 The laying down of the rules had, however, a further advantage 
 for the cement makers in that they showed that much was still to be 
 cleared up with regard to the properties of cement, and that next 
 to nothing was known regarding the constitution and cause of hard- 
 ening of Portland cement, so that the impulse was given to study these 
 questions. The German cement makers applied themselves with much 
 diligence and zeal to these questions. Many works appeared which 
 gave explanations regarding the properties of Portland cement, and so 
 
 34 
 
contributed to clear up the questions as to the proper way of making, 
 testing, and treating Portland cement. The value of a chemical lab- 
 oratory for the Portland cement industry came to be recognized, and 
 as early as the seventies every German cement factory had a well- 
 founded laboratory and one or two chemists. The progress of the 
 German cement industry is largely to be attributed to the close and 
 fertile work in these cement laboratories. The laboratories offered 
 their services unselfishly when it was a question of carrying out 
 scientific work for the "Association." Shortly after the establish- 
 ment of the first rules in 1877, a committee was elected to work out 
 new rules, and the whole of the scientific work which was necessary 
 for this purpose was done by the chemists of the different cement 
 factories. How conscientiously and thoroughly this was done is 
 best proved by the fact that the new rules set up in 1887 on the basis 
 of this work were fully valid until 1909; that is, for more than twenty 
 years. 
 
 Many matters which are nowadays looked upon as self-explanatory 
 had at that time to be cleared up by troublesome and tedious experi- 
 ments. With the growth of the German Portland cement industry, 
 constantly increasing calls were made by the Association of German 
 Portland Cement Makers on its members for collaboration in tests 
 and chemical experiments, especially after the Association decided in 
 1885 to watch permanently over the quality of the German Portland 
 cements. For this purpose every cement had to be bought in the 
 open market at least once a year and submitted to the standard test. 
 
 With the 86 different brands of cement which existed in 1898 this 
 was no small task, but it was willingly done up to that time by a 
 few of the large German works free of expense in the general interest. 
 You will be interested to learn that the chief reason for this purpose 
 was to see that no foreign matter, such as ground slag or limestone, 
 was mixed in the cement by works belonging to the German Cement 
 Association, which they bound themselves by signature to refrain 
 from doing. 
 
 Up to the year 1909 there was only allowed an addition of 2 per 
 cent, gypsum or coloring-matter to regulate the setting time and to 
 color the cement. The new rules allow 3 per cent. And even to-day 
 every member must bind himself by signature to mix no kind of 
 foreign matter with his cement, on pain of being expelled from the 
 Association. The Association of German Portland Cement Makers 
 has by this step won in a high degree the confidence of the users of 
 cement. 
 
 35 
 
The question became more acute when, at the end of the last 
 century, the so-called iron Portland cement works came into existence, 
 which added 30 to 70 per cent, of ground blast-furnace slag to the 
 cement after grinding. New methods of analysis had to be found 
 to show in an approved manner any adulteration, and in connec- 
 tion with this a lot of other work cropped up, which could not all 
 be done in the laboratories of the different cement works. At the 
 same time the Association was confronted with the task of making 
 numerous tests for the purpose of revising the rules, and the question 
 of the constitution of Portland cement gained more interest, so the 
 building of its own laboratory was decided on in the year 1899. The 
 
 Fig. 22. Laboratory of the Association of German Portland Cement Manufac- 
 turers at Carlshorst. 
 
 cost of it was defrayed by each factory belonging to the Association 
 paying an extra subscription of $50 per share. Here I should explain 
 that each factory has one share and one vote in the Association for 
 every 50,000 barrels production. A factory with a production of 
 1,000,000 barrels has thus twenty shares. 
 
 In consideration of the meetings of the Association being always 
 held at Berlin, and of the royal material testing office, with which it 
 was desired to collaborate, being also at Berlin, it was decided to 
 establish the laboratory there. The plans for the Association labora- 
 tory were submitted to the next general meeting, and the building 
 of the same was commenced the same year. 
 
 36 
 
The building is carried out in concrete and cement bricks, and it 
 is covered with cement tiles. On the ground floor there is a large 
 room for the preparation of test matter, and a small room for storing 
 the same. There are also in separate rooms testing ovens, an electric 
 motor, a compressor, and the boiler for the steam heating. 
 
 On the first floor are the rooms of the laboratory proper, consisting 
 of a large chemical laboratory, a weighing room, a physical laboratory, 
 and the room where the testing matter is broken and the cubes are 
 crushed. Here is also the manager's office. The second floor is 
 
 Fig. 23. The Office of the Manager. The picture shows the first President, 
 
 Delbriick. 
 
 built as a dwelling for the laboratory manager. The laboratory is 
 fireproof; all the floors are made of concrete and covered with lino- 
 leum. Next to the building is a small shed for keeping the cements 
 in, and also for storing the standard sand, which is sold by the 
 Association laboratory to all factories, builders, and officials. The 
 land cost $7000, the house itself $15,500, the shed $1000, and the 
 inner fittings about $3000; altogether, about $27,000. 
 
 The mechanical, chemical, and physical laboratories are fitted 
 up with all necessary apparatus, but without extravagant equip- 
 ment. 
 
 37 
 
Fig. 24. The Chemical Laboratory. 
 
 Fig. 25. The Physical Laboratory. 
 
 38 
 
The laboratory possesses further an extensive library, containing 
 all books and papers on cement. A small museum has also been fitted 
 up, in which everything worthy of notice concerning cement is 
 collected. 
 
 The " Association Laboratory" is under a management-council, 
 composed of seven members of the Association of German Portland 
 Cement Makers. There are certain rules for the management of the 
 laboratory. Paragraph No. 1 says that the laboratory is to serve, 
 
 Fig. 26. Making the Cubes with the Hammer Apparatus. On the Left the 
 
 Steinbriick Mixer. 
 
 in the first place, for the working out of scientific problems which are 
 in the general interest of the entire cement and concrete industry. 
 
 It is further stated in the rules that tests of chemical and physical 
 nature and breakage tests are to be carried out against payment of 
 fixed fees. But, above all things, all the German cements are to be 
 bought by the laboratory as often as possible from the trade, and 
 tested according to the rules, whereby a check is exercised on the 
 German cements by the Association. A complete analysis is made 
 each year of all German cements. 
 
 The management of the laboratory is in the hands of a chemist, 
 
 39 
 
who has under him other chemists, laboratory workers, and assis- 
 tants. He has to report every month to the management-council 
 on the work done in the laboratory. 
 
 In the reports to the management-council the cements tested are 
 to be distinguished by numbers and not by the names of the factories. 
 
 Fig. 27. Crushing the Cubes with the Amsler-Laffon PRESS. 
 
 The strictest attention is given that business interests shall in no 
 manner be prejudiced by the reports. 
 
 However, if it happens that a cement does not pass the standard 
 test, then the name of the factory and the tests are communicated 
 to the management-council, which then takes further steps. With 
 this exception no factory learns anything of the tests of the other 
 factories. On the other hand, the manager of the laboratory com- 
 
 40 
 
municates every year to each factory the results ascertained in the 
 Association laboratory with its cement as bought from the trade. 
 But no advertisement may be made of these tests. 
 
 To ascertain whether the cement contains any foreign admixture, 
 a special process, the so-called suspense analysis, has been worked out. 
 Cements which are at all suspected of being adulterated are frequently 
 bought from the trade and tested. 
 
 The tests naturally embrace also slag cements, foreign cements, 
 natural cements, and iron-Portland cements, which are regularly 
 bought and tested. 
 
 I can probably best give you an idea of the activity and utility 
 of the Association Laboratory by naming some of the work which has 
 been done in it during the last eight years. 
 
 1. The influence of a slight uncleanness of the standard sand, 
 through brown coal products. 
 
 2. Regarding the Ljamin methods of determining the free hydrate 
 of lime in hardened Portland cement. 
 
 3. Analyses respecting the constitution of Portland cement. 
 
 4. Methods for determining the free hydrate of lime in hardened 
 Portland cement. 
 
 5. Influence of the addition of blast-furnace slag to Portland 
 cement. 
 
 6. Influence of the hardness of water on the setting time and 
 strength of cement mortar. 
 
 7. Swelling phenomena of Portland cement in distilled water. 
 
 8. The behavior of cements on the addition of various means of 
 adulteration, such as trass, ground sand, blast-furnace slag, and 
 artificial slag. 
 
 9. Concerning the question of mixing slag. 
 
 10. Influence of ground water on concrete channels. 
 
 11. Experiments regarding the permissible percentage of sulphuric 
 acid, made with ninety different cements. 
 
 12. Storage of cement bodies exposed to the weather. 
 
 13. Testing process with atmospheric hardening. 
 
 14. Methods of recognizing foreign admixtures in cement. 
 
 15. Working out of a method for determining the sulphide sulphur. 
 
 16. Comparative strengths with different manners of seasoning- 
 made on over ninety cements. 
 
 17. Testing of ninety cements with increased proportion of gypsum. 
 
 18. Testing of ninety cements with combined atmospheric and 
 water-hardening. 
 
19. Finding of shortened ways of testing the constancy in volume 
 of hydraulic cements. 
 
 20. Comparative tests of Portland cements with iron-Portland 
 cements. 
 
 21. Comparative strength tests of " Association " cements with 
 different methods of hardening. 
 
 22. Concrete experiments with different sands and gravels. 
 
 23. Concrete experiments with ground-damp and plastic mixture. 
 
 24. Experiments on the setting of all " Association" cements in a 
 fresh state, and after three, six, nine, and twelve months' storage. 
 
 25. Chemical analysis of sea-water testing bodies. 
 
 26. Uniform testing of hydraulic cements by means of prisms. 
 
 27. Experiments on bending, crushing and tensile strength of 
 prismatic test bodies according to Schule and Ferret. 
 
 28. Attempts to make test bodies out of pure cement with the 
 hammer apparatus. 
 
 29. Regarding the storage constancy of Portland cement. 
 
 30. Experiments with Belgium natural cements. 
 
 31. Experiments on the calcination loss and the specific weights 
 of Portland, natural, and slag cements. 
 
 32. Experiments on the water porosity of mortars. 
 
 33. The behavior of Portland and slag cements when hardened 
 in salt solutions. 
 
 34. Testing of Portland cement mortars with regard to water 
 porosity with addition of ground limestone, hydrate of lime, hydraulic 
 lime, and trass. 
 
 35. Establishment of a uniform method of analysis for Portland 
 cement. 
 
 36. Influence of the proportion of sulphide sulphur with atmos- 
 pheric hardening. 
 
 37. The oxidation of sulphide sulphur in iron-Portland cement. 
 
 38. Testing of mortar mixtures of iron-Portland cement with 
 pumice sand. 
 
 39. Testing of all " Association " cements according to the Le 
 Chatelier test. 
 
 40. Experiments on the increase in temperature with the setting 
 of cement. 
 
 Gentlemen, this is an extract from the scientific work done in 
 recent years by the " Association " laboratory. The chief activity 
 of the " Association" laboratory is directed to the regular testing of 
 the " Association " cements, to the making of tests for private parties, 
 
 42 
 
and to work ordered by and together with the different commissions 
 of the Association of German Cement Makers. Of such commissions 
 we have: (1) The sea- water committee; (2) the rules committee; 
 (3) the sand committee; (4) the setting time committee; (5) the 
 committee for concrete experiments in moorland; (6) the committee 
 for reinforced concrete. 
 
 For all these committees the " Association " laboratory has to 
 carry out the experiments, which are generally very comprehensive. 
 
 The rules committee ordered in one year alone the making of 
 14,000 test bodies. The standard sand is also under the supervision 
 of the " Association " laboratory. 
 
 Within a few years the sale of standard sand has been transferred 
 to the " Association " laboratory, which derives a considerable income 
 therefrom. 
 
 Besides this, the laboratory is being in recent years more and 
 more employed by the factories of the " Association " and by private 
 parties. The number of tests asked for from this side in the past year 
 amounted to over 500. Most of these were tests according to the 
 rules, but there were also raw meal analyses, suspension analyses, 
 tests of trass, tests of concrete, sand samples, oil samples, tests of 
 building bricks, tests of caloric values, and tests of feed-water for 
 boilers. Various cement works have subscribed to have their cement 
 tested every fourteen days in the " Association " laboratory. 
 
 The cost of up-keep of the laboratory is covered by the revenue 
 from these testing fees, together with the profit on the sale of standard 
 sand. 
 
 The greatest amount of work done by the laboratory is, however, 
 the testing according to rules of all the brands of cement belonging 
 to the " Association," the number of which has now risen to 96. 
 
 Each cement is subjected to all the tests prescribed by the rules. 
 It is tested for fineness, specific weight, volume weight, setting time, 
 volume constancy, tensile and crushing strength both with water- 
 hardening and combined atmospheric and water seasoning. There 
 are further made with each cement accelerated tests for volume 
 constancy, including the Heinzel ball test, the kiln test, and the 
 boiling test. The last was not passed in the year 1909 by thirty- 
 two cements, which otherwise were of the best quality and showed 
 great strength. No objection was, of course, made to these, and the 
 boiling test is only made to show its uselessness. 
 
 A complete analysis is also made of each cement. In this way 
 very abundant and valuable analytic material is obtained, from which 
 
 43 
 
conclusions can be drawn with regard to the making of a good Port- 
 land cement. In the year 1909 it was ascertained that the mean lime 
 percentage of all German cement brands reached 63.47 per cent., 
 the highest point up to that time. The maximum contained in a 
 cement was as much as 66.47 per cent. CaO. It will interest you 
 to know that although the German rules call for only 250 kilos pressure 
 strength at the end of twenty-eight days, more than half of all German 
 cement brands had 350 kilos, and of these eight cements showed as 
 much as 450 kilos pressure strength at the end of twenty-eight days. 
 
 The annual results of all cement tests arid analyses of all German 
 cements are tabulated and published every five years in a special 
 pamphlet, which enables cement investigators to have at their dis- 
 posal very conscientiously prepared and copious material. In this 
 summary the various cement brands are, of course, not designated by 
 names but by numbers. 
 
 Gentlemen, I can to-day only draw for you in bold lines a picture 
 of the activity of the " Association" laboratory; if I went into details, 
 a whole book could be written about it, although it has hardly been 
 ten years in existence. I think, however, you will already have 
 formed an idea as to how very useful it is to the German cement 
 industry. The laboratory would have fulfilled its purpose if it had 
 done nothing further than supervise the quality of the German 
 cements. The " Association " laboratory has, however, far exceeded 
 the expectations that were placed in it. At the commencement 
 there were, of course, difficulties to be overcome; the proper man 
 could not be found at the start to manage it, and the revenue did 
 not suffice to cover the expenses. But the laboratory has now stood 
 for a number of years under the management of an able and cautious 
 chemist, who succeeded in a short time in making the laboratorj- pay 
 for itself. 
 
 If I have indicated to you to-day the importance of this institu- 
 tion, I have done so with a special intention. When I had the oppor- 
 tunity last year of studying the American cement industry, I admired 
 nearly everywhere the splendid arrangement of the factories, and I 
 was impressed by the fact that the young American cement industry 
 had made enormous progress in a short time. But on the whole it 
 seemed strange to me that here in America so little laboratory work 
 is done in the general interest by the cement makers, and that you 
 have no " Association " laboratory, such as has been founded in 
 different countries after the pattern of the German. Some of your 
 members inquired at that time about our " Association " laboratory, 
 
 44 
 
and I therefore thought it would be of interest to you to learn some- 
 thing about its arrangement and activity. 
 
 The preliminary work which was necessary for the establishment 
 of the new German rules was mostly done in the " Association" 
 laboratory, and it was only when the work was sufficiently advanced 
 to enable definite methods of testing to be built up, that the latter 
 were further worked out and completed by the members of the rules 
 committee. You all know the new German rules which have been 
 in force since last year for all German states, but it will interest you 
 to learn the early history and to hear the reasons which led to the 
 fixing of the different specifications. 
 
 As I have already mentioned, rules for testing Portland cement 
 were first laid down in 1877. In the rules of that time the following 
 was determined : 
 
 The cement should be sold in barrels of 180 kilos (396 Ibs.). It 
 should be constant in volume and seasoned. 
 
 Cement which had not set in half an hour was considered slow 
 setting. Every cement should set in two hours at the most. The 
 fineness of grinding was fixed at 20 per cent, on the 900-mesh sieve, 
 which corresponds to your sieve No. 100. 
 
 The cement was tested for tensile strength only, as is to-day still 
 the case in America, and the briquettes were rammed by hand, as 
 you do it here. The tensile strength was to amount to ten kilos 
 per square centimeter. These rules were in force in Germany until 
 1887. 
 
 But it was soon seen that the tests made on the basis of these rules 
 were not reliable. A cement which was tested in accordance with the 
 rules in six different places gave six different results. The reason of 
 the poor agreement was soon recognized, first in the impossibility 
 of ramming the briquettes uniformly by hand, and in the great 
 influence of the sand on the strength. 
 
 The problem had now to be solved to make the testing procedure 
 as uniform as possible, and to eliminate all sources of error in the 
 preparation of the samples. A sharp, fine quartz sand of as uniform 
 a grain as possible was first sought for. Such a deposit was found at 
 Freienwalde, and it was brought to a definite fineness by screening. 
 The preparation of this standard sand is under the control of the 
 royal material testing office and the " Association " laboratory. 
 
 The elimination of the sources of error could only be obtained 
 by substituting machinery for hand work, and therefore Steinbrtick's 
 mortar-mixer was tried for mixing the mortar, and Bohme's hammer 
 
 45 
 
apparatus for ramming the briquettes in the molds. It was also 
 attempted to regulate the addition of water. In the meantime the 
 conviction was arrived at that the testing of the concrete for pressure 
 strength was just as important as for tensile strength; an apparatus 
 was sought to crush the cubes, and it was found in the Amsler Laffon 
 press. When the new rules were introduced in the year 1887, the 
 terms of the same had been so well worked out by experiments that 
 they stood proof for twenty-two years with success. These rules, 
 which were in force until 1909, differed from the old rules chiefly in 
 the following points : 
 
 1. A definition for Portland cement was laid down. The object 
 of this was to exclude from the definition " Portland cement" all 
 cements which had been diluted by the admixture of blast-furnace 
 slag or limestone. The members of the Association were bound to 
 bring into the market nothing but pure, unmixed Portland cement. 
 The declaration they had to sign ran: "The members of the Associa- 
 tion may only bring into the market under the designation of 'Port- 
 land cement ' a product made by an intimate mixing of finely ground 
 calcareous and argillaceous materials or calcareous and argillaceous 
 silicates burnt to incipient fusion and ground to a flour. They bind 
 themselves to not acknowledge as Portland cement any product made 
 in a different way from that described above, or to which foreign 
 matter is added during or after burning, and to look upon the sale of 
 such products as deception of the buyer. But this bond does not 
 apply to slight additions up to the amount of 2 per cent, which may 
 be required for the regulation of the setting time or for other special 
 purposes." 
 
 2. In addition to tensile strength, the pressure strength was intro- 
 duced. At the same time the claims on the strength were raised con- 
 siderably, namely from 10 to 16 kilos per square centimeter. For 
 the pressure strength 160 kilos per square centimeter was fixed. 
 
 3. The standard sand was introduced as uniform sand, and the 
 preparation of the briquettes by machinery was determined on. 
 
 4. The residue permissible on the 900-mesh screen was reduced 
 from 20 per cent, to 10 per cent. 
 
 5. The Vicat needle was introduced for the determination of the 
 setting time, and it was resolved that slow-setting cements should have 
 at least two hours' setting time. 
 
 The old rules regarding the volume constancy were retained 
 unchanged. 
 
 At the commencement of this century concrete construction and 
 
the use of concrete for building found a larger field; it was soon 
 recognized that the claims on the strength would again have to be 
 increased, and that the preparation of the test bodies would have to 
 be more suited to the practice. If with the previous rules the season- 
 ing in water was laid down, it was done because the results agreed 
 closest with this method. In years of work, in which many hundred 
 thousand sample bodies were stamped and crushed by members 
 of the Association, a serviceable method was at last found in the so- 
 called combined seasoning, that is, immersion for six days in water 
 and then keeping for twenty-one days at room temperature. 
 
 As cement is now often worked in a plastic condition, endeavors 
 were made to test sample bodies made of plastic cement mortar. 
 But all the results from many thousands of experiments were insuffi- 
 cient. No conformity could be attained. So it was decided to again 
 make the briquettes out of ground-damp cement mortar the same as 
 before. You are aware that the International Commission is trying 
 for the testing of plastic cement mortar, but according to the results 
 yielded by the experiments in Germany it will hardly be possible, 
 especially if value be placed on agreement in the results of the tests, 
 which is the chief thing. 
 
 In accordance with actual practice, the briquettes have been kept 
 in the open air, exposed to heat, cold, rain, and sunshine, and tested 
 after twenty-eight days. The degrees of strength ascertained were 
 very high, but did not at all agree with each other. This method was 
 therefore abandoned. 
 
 Trials were then made with simply leaving the samples to harden 
 at room temperature. But even with this method the tests made in 
 different laboratories did not show the desired conformity. Dr. 
 Michaelis then proposed to imitate actual practice by placing the 
 samples alternately in cold water, in the atmosphere, and in a box 
 at high temperature, and testing after twenty-eight days of such 
 treatment. The results were favorable, and much higher strengths 
 were determined than by immersion in water. In spite of this, how- 
 ever, the method was not adopted, owing to it being so complicated. 
 The method proposed by Dr. Goslich met the same fate; his sugges- 
 tion was to let the bodies harden in a closed box over burnt lime, 
 while excluding the carbonic acid. 
 
 The only serviceable way of seasoning the samples proved to be 
 the combined seasoning, that is, six days in the water and then twenty- 
 one days in the atmosphere. This method was again checked by the 
 making and testing of several thousand sample bodies. 
 
 47 
 
Concrete work has chiefly to withstand pressure, and it was 
 therefore decided to meet the natural conditions in this respect, 
 and the pressure test was introduced as the conclusive test. The 
 test for tensile strength is now only of minor importance, and has 
 only been retained as a preliminary test for the building place. After 
 seven days' water seasoning the minimum strength shall be at least 
 12 kilos per square centimeter. 
 
 As it is often important for the concrete builder to make sure as 
 soon as possible of the quality of the cement, this circumstance was 
 taken account of in the new rules by the introduction of a crushing 
 test after keeping the cube one day in moist air and six days under 
 water. The crushing strength must amount to at least 120 kilos 
 per square centimeter. 
 
 As, however, with the laying down of the new rules it was especially 
 a question of increasing the minimum strength after twenty-eight 
 days, which up to then had amounted to 160 kilos per square centi- 
 meter, it became necessary to test all the German cements after the 
 new combined seasoning, and to fix the minimum strength in ac- 
 cordance. The result was that in place of 160 kilos per square centi- 
 meter in force up to that time, the minimum strength was fixed at 
 250 kilos per square centimeter in the new rules. Otherwise the 
 only further change made in the new rules was that the fineness of 
 the cement was again increased, and not more than 5 per cent, residue 
 allowed on the 900-mesh sieve. You will be interested to hear that 
 in Germany the grinding is done much finer. The residue on the 
 900-mesh sieve in 1909 averaged 1 .39 for all the factories. Cement was 
 bought from the trade which had only 0.1 per cent, residue, and was 
 thus very finely ground. Five per cent, magnesia is permitted and 
 2.5 per cent, sulphuric acid. These limits were, of course, not intro- 
 duced until the conviction had been arrived at by numerous experi- 
 ments that neither 2.5 per cent, sulphuric anhydride nor 5 per cent, 
 magnesia are in any way harmful to the quality of the cement. 
 According to the new rules, an addition of 3 per cent, is allowed to 
 regulate the setting time, in consequence of rotary kiln cements often 
 requiring more gypsum to make them slow than ring kiln cements. 
 The new rules no longer contain any stipulation as to when the setting 
 must be finished; they propose, as of much more importance, to fix 
 the commencement of the setting, which has been put down as one 
 hour at the outside. The definition of Portland cement has been 
 drawn up very carefully in the new rules, so that it is impossible in 
 the future for other hydraulic cements to be mistaken for it. It runs: 
 
Portland cement is a hydraulic cement with not less than 1.7 
 parts in weight of lime (CaO) to 1 part in weight of soluble silica 
 (SiO 2 ) plus alumina (A^Oa) plus oxide of iron (Fe 2 O 3 ) made by 
 fine grinding and intimate mixing of the raw materials, burning to 
 at least incipient fusion and fine grinding. 
 
 Owing to the tests for the new German rules being spread over a 
 number of years, and to the tests being made with all the German 
 cements in ten different places, the Association of German Portland 
 Cement Makers possesses an enormous quantity of data on results 
 of tests, which give very interesting conclusions as to the behavior 
 of cements under different conditions of testing. 
 
 Ktfo- 
 
 /<??*. 0*3 
 
 b* 
 
 or 
 
 tec^ 
 
 4Z 
 
 &. 
 
 -&J& 
 
 G 
 
 260 
 
 nfl 
 
 * '.3# 
 
 *& 
 
 
 
 ^ 
 
 \/ 
 
 Average Crushing Strength of all German Cements During the Last Nine Years. 
 
 The 96 cements were tested in twelve different testing stations 
 for both tension and pressure, according to the old and the new rules. 
 It turned out that the results with combined seasoning agreed ex- 
 cellently. 
 
 The minimum of 120 kilos pressure strength was reached by 
 all the cements with the exception of three. I would emphasize the 
 fact that these tests were made before the new rules came into force, 
 solely to ascertain how many cements at the time of the old rules 
 corresponded to the higher standards of the new rules. Nearly all 
 the cements already came up to the new standard. 
 
 Only one cement remained under 160 kilos, the standard of the 
 
 49 
 
old rules, while all cements with the exception of seven showed over 
 200 kilos pressure strength, so that it was decided to take this figure 
 as the minimum strength. The seven factories had therefore to 
 improve the quality of their cement to reach at least 200 kilos pres- 
 sure resisting strength after twenty-eight days. 
 
 It is expressly stipulated in the new rules that this manner of 
 testing with twenty-eight days' water-seasoning is only to be applied 
 to those cements which are to be used for waterworks. Otherwise 
 the combined seasoning is taken, that is, six days in water and twenty- 
 one days in the air. As only nine of the 96 cements did not attain 
 a strength of 250 kilos after twenty-eight days, it was decided to 
 introduce 250 kilos as the minimum strength, in consideration that 
 
 CJL 
 
 '*$- 
 
 JL'L 
 
 -te 
 
 tt 
 
 43* 
 
 /\ 
 
 ^L 
 
 Average Percentage of Lime in All German Cements During the Last Nine Years. 
 
 the manufacture of these nine cements could be so far improved as 
 to bring them up to this limit. This test for pressure resistance with 
 combined seasoning is thus laid down in the new rules as the most 
 important and conclusive one. After its introduction all German 
 cements passed the test made last year by the Association laboratory. 
 
 In scientific interest all cements have been tested in the same 
 manner for tensile strength. 
 
 It is very interesting to see how the average strength of all the 
 German cements tested in the Association laboratory during the 
 years 1902 to 1909 considerably increased, in view of the probability 
 of the introduction of new standards. 
 
 The average figure in 1902 was 240 kilos; then in 1904, 242 
 
 50 
 
kilos; in the year 1906, nearly 249 kilos; and after a slight decrease 
 in 1907, it amounted to 290 kilos in 1909 at the time of the introduc- 
 tion of the new rules. These are the values of the tests according 
 to the rules valid at the time, which only called for 160 kilos. 
 
 But with the efforts constantly to make better cement, the average 
 lime percentage of the German cements has also considerably in- 
 creased of late years, so that it now amounts to 63.4. You see what 
 interesting comparative material is produced by the work in the 
 " Association " laboratory. 
 
 31 
 
 _e 
 
 'o5 
 
 or 
 
 /) 
 
 
 05 
 
 "22 
 
 /D^ 
 
 
 :=^kX 
 
 7^^ 
 
 Of? 
 
 Average Fineness on Screen of 5000 Mesh per Square Centimeter of All German 
 Cements for the Last Nine Years. 
 
 I think that from my remarks you will have formed an idea 
 of the persistent and splendid manner in which for years the tests 
 were carried out and which finally led to the establishment of the new 
 German rules. A copious material, which probably exists in no 
 other association of cement makers, has been collected, making it 
 possible on the basis of the experience gained to establish new founda- 
 tions for testing cement, which call for a better quality of cement, 
 and which are more suited to actual practice than formerly. It is 
 therefore to be hoped that the new German rules will stand proof 
 for years and guarantee a satisfactory testing of Portland cement. 
 
 51 
 
The Association of American Portland Cement Manufacturers is an 
 Educational and Scientific Body, composed of the following Members: 
 
 ALLENTOWN PORTLAND CEMENT 
 
 CO., Allentown, Pa. 
 
 ALMA CEMENT CO., Wellston, Ohio. 
 ALSEN'S AMERICAN PORTLAND 
 
 CEMENT WORKS, 45 Broadway, 
 
 New York, N. Y. 
 AMERICAN CEMENT CO. OF NEW 
 
 JERSEY, Pennsylvania Building, 
 
 Philadelphia, Pa. 
 ASH GROVE LIME & PORTLAND 
 
 CEMENT CO*. R. A. Long Building, 
 
 Kansas City, Mo. 
 ATLAS PORTLAND CEMENT CO., 30 
 
 Broad St., New York, N. Y. 
 BATH PORTLAND CEMENT CO., Bath, 
 
 Pa. 
 CALIFORNIA PORTLAND CEMENT 
 
 CO., Los Angeles, Cal. 
 
 CASTALIA PORTLAND CEMENT CO., 
 
 Publication Building, Pittsburg, Pa. 
 CAYUGA LAKE CEMENT CO., Ithaca, 
 
 N. Y. 
 CHICAGO PORTLAND CEMENT CO., 
 
 1 08 La Salle Street, Chicago, HI. 
 COLORADO PORTLAND CEMENT CO. 
 
 Denver, Colo. 
 CONTINENTAL PORTLAND CEMENT 
 
 CO., St. Louis, Mo. 
 COPLAY CEMENT MFG. CO., Coplay, 
 
 Pa. 
 DEWEY PORTLAND CEMENT CO., 
 
 Scarritt Building, Kansas City, Mo. 
 DEXTER PORTLAND CEMENT CO., 
 
 Nazareth, Pa. 
 
 DIAMOND PORTLAND CEMENT CO., 
 Williamson Building, Cleveland, Ohio. 
 
 DIXIE PORTLAND CEMENT CO., 
 Richard City, Tenn. 
 
 SDISON PORTLAND CEMENT CO., 
 
 Stewartsville, N. J. 
 FREDONIA PORTLAND CEMENT 
 
 CO., Fredonia, Kansas. 
 GERMAN-AMERICAN PORTLAND 
 
 CEMENT WORKS, La Salle, III. 
 
 GLENS FALLS PORTLAND CEMENT 
 
 CO., Glens Falls, N. Y. 
 GREAT WESTERN PORTLAND 
 
 CEMENT CO., Kansas City, Mo. 
 HELDERBERG CEMENT CO., 78 State 
 
 Street, Albany, N. Y. 
 HURON PORTLAND CEMENT CO., 
 
 Ford Building, Detroit, Mich. 
 IOLA PORTLAND CEMENT CO., lola, 
 
 Kansas. 
 IOWA PORTLAND CEMENT CO., De 
 
 Moines, Iowa. 
 LAWRENCE PORTLAND CEMENT CO., 
 
 Siegfried, Pa. 
 
 LOUISVILLE CEMENT CO.,Speed*,Ind. 
 MARQUETTE CEMENT MFG. CO., 
 
 La Salle, III. 
 MONARCH PORTLAND CEMENT CO., 
 
 Humboldt, Kansas. 
 NAZARETH CEMENT CO., Nazrth,Pa. 
 
 NEW AETNA PORTLAND CEMENT 
 
 CO., Detroit, Mich. 
 NEWAYGO PORTLAND CEMENT CO., 
 
 Grand Rapids, Mich. 
 NORFOLK PORTLAND CEMENT 
 
 CORPORATION, 604 Pennsylvania 
 
 Bldg., Philadelphia, Pa. 
 NORTHWESTERN STATES PORT- 
 LAND CEMENT CO., Mason City, 
 
 Iowa. 
 OGDEN PORTLAND CEMENT CO., 
 
 Ogden, Utah. 
 OKLAHOMA PORTLAND CEMENT 
 
 CO., Ada, Oklahoma. 
 OMEGA PORTLAND CEMENT CO., 
 
 Jonesville, Mich. 
 PEERLESS PORTLAND CEMENT CO., 
 
 Union City, Mich. 
 PENINSULAR PORTLAND CEMENT 
 
 CO., Jackson, Mich. 
 PENNSYLVANIA CEMENT CO., 29 
 
 Broadway, New York, N. Y. 
 PHOENIX PORTLAND CEMENT CO., 
 
 Nazareth, Pa. 
 PORTLAND CEMENT COMPANY OF 
 
 UTAH, Salt Lake City, Utah. 
 RIVERSIDE PORTLAND CEMENT 
 
 CO., Los Angeles, Cal. 
 SANDUSKY PORTLAND CEMENT CO., 
 
 Sandusky, Ohio. 
 SECURITY CEMENT & LIME CO., 
 
 Baltimore, Md. 
 
 SOUTHWESTERN STATES PORT- 
 LAND CEMENT CO., Dallas, Texas. 
 STANDARD PORTLAND CEMENT CO., 
 
 Charleston, S. C. 
 STANDARD PORTLAND CEMENT 
 
 CORPORATION, Crocker Bldg., San 
 
 Francisco, Cal. 
 SUPERIOR PORTLAND CEMENT CO., 
 
 THE, Cincinnati, Ohio. 
 TEXAS PORTLAND CEMENT CO., 
 
 Cement, Texas. 
 U. S. PORTLAND CEMENT CO., 
 
 Kansas City, Mo. 
 UNION SAND & MATERIAL CO., 
 
 Liggett Bldg., St. Louis, Mo. 
 UNITED KANSAS PORTLAND CE- 
 MENT CO., lola, Kansas. 
 UNITED STATESPORTLAND CEMENT 
 
 CO., Coors Building, Denver, Colo. 
 UNIVERSAL PORTLAND CEMENT 
 
 CO., 1x5 Adams Street, Chicago, HI. 
 VIRGINIA PORTLAND CEMENT CO., 
 
 5 Nassau Street, New York, N. Y. 
 VULCANITE PORTLAND CEMENT CO. 
 
 Land Title Bldg., Philadelphia, Pa. 
 WABASH PORTLAND CEMENT CO., 
 
 Ford Building, Detroit, Mich. 
 WESTERN STATES PORTLAND CE- 
 MENT CO., Jackson, Mich. 
 WHITEHALL PORTLAND CEMENT 
 
 CO., Land Title Bldg., Phila., Pa. 
 WOLVERINE PORTLAND CEMENT 
 
 CO., Coldwater, Mich. 
 
 Foreign Member 
 
 CANADA CEMENT CO., LTD., Mont- 
 real, Canada. 
 
Binder 
 
 j Gaylord Brou- Inc. 
 I Stockton, Calif. 
 
 M \ 2<)9 f 
 
 THE UNIVERSITY OF CALIFORNIA LIBRARY