. 1 _-..--_-_
REESE LIBRARY
:' i I K
UNIVERSITY OF CALIFORNIA
, s No.
Accessions
v u u--i
NATURAL ASPHALT
TWENTY YEARS' PRACTICAL EXPERIENCE
OF
NATURAL ASPHALT
AND
MINERAL BITUMEN
BY
W. H. DELANO
r 1
ASSOC. INST. C.E.
GENERAL MANAGER OF THE COMPAGNIE G^NlSRALE DBS ASPHALTES DE
FRANCE LIMITED
E. & F. N. SPON, 125 STRAND
Jlefo gorfe:
SPON & CHAMBERLAIN, 12 CORTLANDT STREET
1893
v
PREFACE.
IN the year 1880 the author read a paper at
the Institution of Civil Engineers, London, on
Asphalt, which was reprinted in Van Nostrand's
'Engineering Magazine,' New York, December
1880, and January 1 88 1.
Since that periodnfte use , of asphalt (also, un-
fortunately, of its various imitations) has greatly
extended indeed in all parts of the civilized world,
so that a popular exposition of its qualities, uses,
and abuses, has become a desideratum.
The author has to express his thanks to various
directors and managers in London, New York,
Berlin, Vienna, Brussels, Rome, Turin, Amsterdam,
and above all to the Municipal and Government
Engineers of Paris, for much information.
117 QUAI VALMY, PARIS.
CONTENTS.
PART I.
NOMENCLATURE OF ASPHALT AND ITS COMBINATIONS.
PAGE
ASPHALT ROCK .. 2
ASPHALT MASTIC 3
GRITTED ASPHALT MASTIC 4
BITUMEN 4
BUTUMINOUS CONCRETE o
GEOLOGY OF ASPHALT 6
ANALYSIS OF ASPHALT 4
LIST OF ASPHALT MINES 19
PART II.
USES OF ASPHALT.
ITS QUALITIES 12
FIRE- AND VERMIN-PROOF FLOORS 15
COATINGS FOR ARCHES OF BRIDGES, VIADUCTS, ETC. .. 15
CASEMATES is
RESISTANCE TO ACIDS 18
INSULATION 19
POWDER MAGAZINES 19
VIBRATION-ABSORBENT 19
ROADWAYS 23
DURABILITY 26
MALLEABILITY , 28
NON-INJURY BY HEAT OR FROST 29
NOISELESSNESS 3O
AGORAPHOBIA : NERVOUS AFFECTION CAUSED BY STREET
NOISE 13
ASPHALT ROADWAYS IN PARIS 32
WOOD PAVEMENT 32
TRACTION ON ASPHALT ROADWAYS 36
viii ASPHALT.
PART III.
MODES OF APPLYING ASPHALT.
PAGE
ROADWAYS: CAMBER 37
,, SUBSOIL 41
., CONCRETE 41
,, TIME OF LAYING 43
,, HOT ASPHALT POWDEK 43
FOOT-PATHS OF COMPRESSED ASPHALT 45
,, GRITTED ASPHALT MASTIC 45
COATINGS FOR MASONRY 52
CASEMATES 52
ROOFS 52
SILOES 53
VERTICAL APPLICATIONS 53
INSULATION OF ELECTIC WIRES 55
ASPHALT FLAGS AND SLABS 57
PART IV.
GENERAL OBSERVATIONS.
WIDTH OF TIRES FOR HEAVY TRAFFIC 58
USE OF SALT FOR MELTING SNOW .. 58
KERBS 59
SPEED OF STREET-TRAFFIC 59
TRAMCAR RAILS 60
MAINTENANCE CONTRACTS 60
CONVERSION OF OLD ROADS INTO ASPHALT ROADS .. .. 60
CAUTION MONEY AND MODE OF PAYMENT 61
MAINTENANCE 62
Low PRICES 65
IMITATIONS OF NATURAL ASPHALT 66
TRAFFIC OF PARIS 69.
WEAR OF MACADAMISED ROADS 70
WORK DONE BY PARISHES WITHOUT CONTRACTORS.. .. 71
COST OF WORK IN PARIS 72
TWENTY YEARS' PRACTICAL EXPERIENCE
OF
NATURAL ASPHALT
AND MINERAL BITUMEN.
PART I.
NOMENCLATURE OF ASPHAL7 AND ITS
COMBINA TIONS.
FOR all that concerns the origin of asphalt, its
nature, history and geological formation, and
mode of extraction, the well-known work * of
M. Leon Malo (who for thirty years has been
the prophet of natural asphalt) is the best guide.
Of this gentleman the author is an earnest and
grateful disciple.
Nomenclature. Asphalt is a natural product
(see Fig. i), a bituminous limestone in which
carbonate of lime and pure mineral bitumen are
most intimately combined by natural agency, the
proportions varying from 7 per cent, bitumen and
* ' L' Asphalte : son origine, sa preparation, ses applications, par
Leon Malo.' Baudry Si Ce., diteurs, 15 Rue des Saints Peres,
Paris.
B
NATURAL ASPHALT.
Fig. I. NATURAL ASPHALT ROCK.
Fig. 2. SECTION OF AN ASPHALT MINE.
93 per cent carbonate of lime to 20 per cent, bitu-
men and 80 per cent, carbonate of lime.
NATURAL ASPHALT. 3
It is found in seams like coal, and mined in the
same way (see Fig. 2). Heated on a hot plate it
falls to pieces (see Figs. 3, 4).
Fig. 3. ASPHALT ROCK COMMINUTED BY HEATING ON
AN IRON PLATE SIFTED.
Fig. 4. ASPHALT ROCK COMMINUTED BY HEATING ON
AN IRON PLATE UNSIFTED.
Asphalt Mastic, when pure, is composed of asphalt
rock ground to a fine powder and mixed hot with
B 2
4 NATURAL ASPHALT.
a varying proportion of hot bitumen similar to that
contained in the natural rock, the pasty product
being run into moulds, forming the well-known
cakes, which weigh about
561bs. Their diameter is
30 J inches, and they are
from 4 to 4% inches high.
Analysis should show
about 15 per cent, bitu-
Figj 5> men and 85 per cent, of
limestone in these cakes.
Gritted Asphalt Mastic is composed of pure
asphalt mastic, broken to small pieces of from \ to
I inch in diameter, remelted in a kettle (see p. 50).
There is added 5 per cent, of pure bitumen and from
30 to 40 per cent, of fine clean dry grit, the grains
of the latter above -| inch in diameter.
The author prefers limestone grit, but if silicious
grit only can be obtained it should be as fine as
sea sand.
Asphaltic or Bituminous Concrete is composed of
two parts of hot gritted mastic mixed with three
parts of flint pebbles, or rubble, about 2\ inches
diameter. The stones should also be hot.
Bitumen is a mineral product found in asphalt
rock, whence it can be extracted pure. It is found
in the Trinidad "Pitch Lake," mixed with 33 per
cent, of fine clay sand and vegetable matter, and
33 per cent, of water. It is also found in various
NATURAL ASPHALT. 5
states of purity, sometimes mixed with sand or
sulphur, in Auvergne (France), Chieti (Italy),
Avlona, Selenitza (Albania), Beyrout, Venezuela,
California, Kentucky, Utah, and elsewhere, par-
ticularly the Dead Sea (see p. n).
Bitumen is an exact synonym of mineral pitch ;
it is in fact the Latin equivalent for pitch, and the
adjectival form " bituminous " has replaced the
Saxon form " pitchy."
Bitumen is allied to petroleum, naphtha and
shale oils ; but it is not by any means identical, as
the results of their use show. It is, as M. Malo
writes, only " similar to itself."
The type and standard of mineral bitumen is
that extracted from Seyssel asphalt, which can be
subjected to 500 Fahr., or x below freezing point,
without losing its tenacity, malleability, or suffering
any deterioration.
Its composition is :
Carbon 85 parts.
Hydrogen 12 ,,
Oxygen 3 ,,
100 parts.
Bitumen is therefore the principal ingredient of
asphalt, but in that latter body is so intimately
intermixed with the limestone by Nature itself that
the result asphalt must be considered an inde-
pendent material, like granite or porphyry, Roman
cement or coal.
It may be imperfectly imitated, created it can
NATURAL ASPHALT.
never be. Bitumen, it would seem from the testi-
mony of the Seyssel asphalt mines, may have
Fig. 6. PROBABLE FORMATION OF ASPHALT.
AFTER RIVER-EROSION.
permeated, whilst in a state of vapour, the limestone,
which at that period must have been soft (see
NATURAL ASPHALT.
hypothesis below). Only the perfervent heat of
Nature can have vaporised carbon.
Fig. 7. PROBABLE FORMATION OF ASPHALT.
BEFORE RIVER-EROSION.
Asphalt is generally found in 6 to lO-feet seams,
between two layers of white hard limestone, either
8 NATURAL ASPHALT.
totally unimpregnated with bitumen or else with
mere traces of it, which have the appearance of
thin smoke or the faint stains in white marble.
Sometimes, however, layers of sand and marl are
found, which must be propped, or held up by
rubble.
Some contractors (outside Europe) have quite
recently used the term asphalt and bitumen as
though they were synonymous and interchange-
able, and even such an anomalous phrase as the
following has been seen in print : " Asphalt from
the Trinidad Pitch Lake." Such misuse of terms
should be strictly avoided in estimates and speci-
fications, as causing confusion.
Bitumen and mineral pitch are interchangeable
terms, but asphalt stands alone.
The necessity for a clear and precise nomencla-
ture is shown by the interesting ' Report on the
Geology of Trinidad/ by G. P. Wall and J. G.
Sawkins, F.G.S.,* where the words
Asphaltum,
Asphalt,
Bitumen, and
Pitch
are used to express one and the same aiticle,
viz. Trinidad Pitch.
There seems some tendency in the best human
nature to abuse synonyms and revel in tautology.
Sometimes from bad habit, sometimes from
fraudulent motives, gas-tar, Stockholm tar, petro-
leum and naphtha residuum, shale grease, hard
* Longmans, London.
NATURAL ASPHALT. 9
pitch from the distillation of animal fat, are called
asphalt. This misappropriation of terms, this
"calling evil good," should be sternly reprobated
by engineers, architects and chemists who cherish
clearness of expression and detest puzzledom.
Analysis of Asphalt (Natural product). As
mined, the rock should be of a chocolate colour, fine
in grain, evenly impregnated with bitumen, free
from sulphur, pyrites, clay, sand or other extraneous
matter. When examining with the microscope,
always look at a fresh fracture.
Rich Val de Travers rock, containing say 1 1 to 1 3
per cent, bitumen, should be mixed with one-half
of fine Seyssel rock containing 7 per cent, of bitu-
men, which is fixed and invariable, producing thus
= 9 per cent, powder, suitable for a
climate like that of London.
The same may be done with Ragusa (Sicilian
rock), which is rich in bitumen of excellent quality,
only the texture or grain of the limestone is loose,
whereas that of Seyssel is fine and dense.
Mons and St. Jean de Marvejols asphalts are
similar in structure to Ragusa, but the limestone is
much finer.
The rough and ready way ol testing asphalt is
to dissolve its powder taken from a three-ton
bulk, in carbon bisulphide, turpentine, or ether.
Stir well with a glass rod and strain through a
thick paper filter ; then let the sulphide evaporate,
CKIVEBSITT
10 NATURAL ASPHALT.
which it will do at 70 ; weigh the bitumen and
the residuum, afterwards washing the latter in
hydrochloric acid, which will cause the lime to
effervesce, leaving any silica, pyrites, &c. ; but for
an absolute test an analyst accustomed to hydro-
carbons should be called in.
The same test does for bitumen, to ascertain
the proportion of clay or other impurities in it ;
naturally the practical test for a new asphalt is to
lay it in a crowded thoroughfare and let three
winters and summers pass over it.
Refined Trinidad Pitch will always contain
from 20 to 25 per cent, of fine clay ; nevertheless it
is so tough, malleable and stringy, that for asphalt
mastic it is preferable to some other short fibred
bitumens chemically purer.
List of Asphalt Mines. Asphalt is found near
Seyssel, France, in the Rhone Valley between the
towns of Bellegarde and Seyssel, the centre of the
concession being the railway station of Pyrimont,
specially created for the important mastic works of
the Compagnie Generale des Asphaltes de France,
of 1 17 Quai de Valmy, Paris ; at Travers, belonging
to the canton of Neufchatel, Switzerland, conceded
till 1907 to an English company in London ;
Mons and St. Jean de Marvejols, near Alais,
France ; Chieti, in the Abruzzi, Italy ; Ragusa,
Sicily ; Auvergne (though here mostly bitu-
minous sandstone) ; Lobsann in Alsace (much
NATURAL ASPHALT. II
mixed with iron pyrites) ; Limmer, near Hanover,
Germany. Sandstone impregnated with bitumen
is found in Kentucky, Utah, California, and at
Maestu in Spain.
The chief source of supply of mineral bitumen
is the British island of Trinidad, West Indies, but
there are also supplies to be had from Chieti,
Italy ; Auvergne, Vallona, Albania ; Bermudez
in Venezuela ; Barraquilla in Columbia, Central
America ; Province of Oran, Algeria'; * Beyrout,
Syria, &c. The bitumen from the Dead Sea is
only used for medium or black varnish; the supply
is scanty.
Bitumen to be good should be free from dross,
non-evaporative and contain no oils that will evapo-
rate at 480 Fahr. ; be perfectly black, not brilliant,
and at 70 Fahr. have the consistency of bees'-wax.
The best way to test the quality is to draw it out
in threads ; the longer they stretch the better the
sample.
* The author saw, some ten years ago, in Algeria, an Arab
sheikh, on the borders of the Chelif River, who was pitching his
shallow flat-bottomed boat with pitch from a scanty bituminous
spring near, and was reminded of the divine command to the
Patriarch Noah " Bituminabis earn bitumine" says the Vulgate.
12 NATURAL ASPHALT.
PART II.
THE USES OF ASPHALT.
BEFORE describing, from long and varied ex-
perience, the best modes of using asphalt, the
author would express his firm belief that this
valuable and unique material was specially created
for certain ends, like coal, iron, copper, &c. It is
for man to study and utilise the gift.
Its Qualities. After the necessary manipulation,
it becomes impervious to water and air, resists fire
and acids, insulates the electric circuit, produces no
sparks by contact with iron, repels vermin, absorbs
vibration ; its vapours are antiseptic ; it is durable,
easily repaired ; so malleable that it can be applied
to any curve, so ductile that it will yield to any
ordinary pressure from whatever direction without
cracking. It is unaffected by frost, and though
slightly softened by heat, say 125 Fahr., it never
disintegrates, even at 450, and upon returning
to its normal temperature has lost none of its
qualities.
It produces no dust, consequently no mud.
It can be laid by workmen of ordinary intel-
ligence in any climate, for its malleability can be
NATURAL ASPHALT. 13
increased or decreased at will, so as to suit the
temperature of arctic or of tropical regions.
Apart from its hygienic properties, its noiseless-
ness, its harmonious tint, it is most agreeable' to
walk upon (not hard and slippery, like granite,
cement, tiles, &c.). It is in fact the street carpet.
Its duration is greater than that of granite and
flag, its first cost and annual maintenance less.
Illilllllfilli
Fig. 8.
The traction for horses on the level is easy, they
can draw from three to six times as much as on
rough coarse metal or stone pitched roads.
Imperviousness to Moisture. Let us consider the
" damp course" (Fig. 8), so simple, and so useful,
that it ought to be made compulsory in building
operations.
14 NATURAL ASPHALT.
When it is remembered that one porous brick, 8^
inches by 4J- inches by i inches, weighing say 4* 78
Ibs. avoirdupois, will absorb and hold Ib. of
water, one is astounded at the amount of water
there may be contained in an ordinary wall, drawn
up by capillarity, causing rheumatism, fever, and
other diseases, apart from discomfort and depres-
sion, shortening the lives of adults, checking the
Fig. 9.
development of children. Asphalt arrests capillarity,
and settlement of masonry does not cause it to
crack like cement.
Some twenty-five years ago, a handsome house
was built on the borders of the Lake of Enghien,
a Seyssel asphalt damp course was used, and the
walls, as far as regards the unceasing action of
capillarity, kept perfectly dry. But one day some
NATURAL ASPHALT. 15
underpinning was done ; the mason forgot to relay
the asphalt damp course, or else thought it was a
fad and wilfully neglected to repair it ; the conse-
quence was, walls saturated to such an extent, that
the house became uninhabitable.
Fire- and Vermin-proof Floors. An excellent
and springy floor is made by setting the joists in
asphalt mastic, and afterwards nailing down the
battens in various patterns, care being taken not
to leave sufficient space between the battens and
asphalt for rats and mice to pass ; the asphalt is un-
inflammable, and will not allow air to pass (Fig. 9).
Sometimes the boards or battens are laid direct
on asphalt without joists, but then the floor is not
so elastic, and may not always keep level.
Coatings of Asphalt Mastic upon the Arches of
Viaducts and Bridges of Stone or Iron keep out
moisture from above, and so prevent the action of
percolation and frost upon the joints and key-
stones, and thus arrest decay. (Figs. 10 and n.)
Water is the enemy and must be kept out well
laid asphalt is the remedy. How many accidents
are constantly occurring to railway bridges, owing
to the neglect of so simple a precaution.
Casemates should always be coated with liquid
asphalt under the bomb-proof earth covering (see
Fig. 12).
In time of war soldiers must live in dry case-
mates or they will soon be down on the sick-list.
i6
NATURAL ASPHALT. I?
Military engineers are expensive, and it pays to
take care of them.
Heavy masonry always settles, and if only a
Portland cement coating be used it will crack and
split, and be of no more use to keep water off than
a sieve.
Fig. 12.
The author once witnessed the following proof of
the correctness of this. About 20 feet of earth was
removed from the roof of a bomb-proof casemate,
and the coating of Seyssel asphalt examined, after
40 years' burial. There was no crack anywhere, it
had yielded to the settlement of the masonry, long
roots of lucerne had in vain tried to penetrate it.
The interior of the casemate was dry and habitable.
The strong room of an important Public
Company in Paris has been walled with bitu-
C
i8
NATURAL ASPHALT.
minous concrete, the walls, with books inside,
having been previously submitted to a fierce fire.
It is as impenetrable to air as to water.
When a coating of gritted asphalt is used on a
roof, it will, in case the foundations are burnt, fall
in and stifle the flames like a wet blanket.
The result has been proved by insurance
companies on several occasions,* by actual tests.
It is flame-proof.
Fig. 13. CONDUIT FOR ELECTRIC WIRES.
Resistance to Acids. Specially-made mastic will
resist the action of acids for a long time ; the
bitumen resists completely and defends the lime-
* See * Note sur 1'application de 1'asphalte coule sur les planchers
des Magasins et Greniers pour empecher la propagation de
1'incendie. Imprimerie E. Capiomont et Cie, 6 Rue des Poitevins,
Paris, 1888.'
NATURAL ASPHALT. 19
stone component. It is used for lining tanks
required in electrolysis and for electric batteries.
Insulation. Bitumen is an excellent insulator
for electric wires, at least 30 per cent, superior to
gas-tar. It will resist the action of underground
moisture.
The author has often seen leakages of
electricity completely arrested by drowning the
wires in asphalt mastic as they lay. This was
particularly the case at the National Opera House
in Paris, where condensed water, getting into the
trough where the wires were, rotted the hempen
coating and caused a leakage of 30 per cent.
Powder Magazines. Asphalt produces no sparks
by contact with steel, so is excellent for powder
magazines. The floors, often made with timber
fastened with copper nails, rot after a time, but
asphalt defies time. Of course, for powder
magazines pure compressed or pure liquid mastic
should be used, not gritted mastic.
Absorption of Vibration by Bituminous or
Asphaltic Concrete and Compressed Asphalt Powder
in Moulds. One of the most interesting applica-
tions of asphalt is that of bituminous or asphaltic
concrete for quick-speeded machinery, such as dy-
namos and their motors, grinding machinery like
Carr's disintegrator (700 revolutions per minute)
C 2
20 NATURAL ASPHALT.
hydro-extractors (1400 revolutions per minute),
printing-machines, and percussive machines like
gas - engines, stamping-presses, steam - hammers,
spring-hammers, &c.
The author has during the last twenty years
arrested many a lawsuit begun by indignant neigh-
bours against users of machinery in the crowded
houses of cities. A high-speed engine working in
a cellar will make a seven-story house tremble, and
at night prevent sleep of the inmates.
The asphalt concrete may be run in moulds to
any shape and sold by the cube.
The cure is complete, when the mass is big
enough. For instance, take the foundations for
a stamping-press, the gradual annihilation of the
concussion can be felt by placing the hand on the
side of the block of bituminous concrete which
receives it. The latest application of asphalt con-
crete for this purpose is that of the electric-light
motors at Moe't and Chan don's, Epernay, France,
where it was absolutely necessary to prevent the
8,000,000 bottles of champagne in the cellars from
shaking.
The foundations for the dynamos and their
motors in most of the Paris theatres are of bitu-
minous concrete. They are surrounded by brick
walls. No vibration is felt ; the temperature in
the cellars where the engines are is 120 Fahr.
For steam-engines the surface of the foundation
must be laid in cement, or have a layer of stone, to
avoid bad effects of oil and grease, which are pre-
Fig. 14.
22 NATURAL ASPHALT.
judicial to asphalt after a certain time. This
application of asphalt requires extra care, and
must not be attempted except by professional
asphalters, as a failure would be no trifling matter.
Only the best materials must be used. A block
may take three days or more to settle and cool.
The same effect can be obtained by successive
layers of hot asphalt powder compressed in a
strong steel frame ; and this plan is used for steam
hammers, avoiding the jarring of walls and the
breakage of glass in skylights, &c.
M. Malo was the first to use asphalt to avoid
the vibration of machinery, and has carried out at
Pyrimont Works, the centre of the Seyssel Asphalt
Concession, many ingenious applications. The
author has followed his lead in Paris. The
instances are now too numerous to detail ; they
vary from stamping-presses and printing-machines
to the heaviest engines.
At the present time (1893) an underground rail-
way is being constructed near the astronomical
observatory of Paris. The astronomers find that
their mercury bath and various delicate instruments
vibrate. Both M. Malo and the author are being
consulted as to the remedy, which will have to
be paid for by the railway company.
Either the instruments will have to be mounted on
bituminous concrete foundations, or else the whole
building of the observatory be insulated by a wall
of bituminous concrete at considerable expense.
Many useful new applications of asphalt concrete
NATURAL ASPHALT. 23
are yet in their infancy. One is to line the granite
embrasures efforts with this material, which makes
no splinters. Splinters often do more harm to
artillerymen than explosive bullets. Leaden bullets
will flatten when fired against asphalt powder
heaped up.
It is this quality, shared by indiarubber, cork,
and to a certain extent wood, which, coupled
with its impermeability aid artistic colour, renders
compressed asphalt so suitable for the streets of
crowded cities.
The din and jar of street traffic are a torment to
artists, literary men, men of business, women and
young children.
The passing at 8 miles an hour of a heavily
laden four-wheel van over a stone or cobble
roadway, will make a six-story house tremble
from top to bottom, and often dislodges bricks, tiles,
and architectural ornaments.
It is fortunate for dwellers in cities that there
exists in compressed asphalt a pavement, cheaper
than granite, that suppresses such exasperating
annoyance.
Asphalt roadways enhance the value of house
property, diminish traction, are not of themselves
slippery ; produce no dust, therefore no mud ;
absorb no liquid nor solid excremental matter,
nor filth nor putridity, therefore under the hot blaze
of a summer sun emit no miasmata. Asphalt
affords no element for fermentation, is therefore
hygienic par excellence.
24 NATURAL ASPHALT.
It should be used universally ; the only excuse
admissible for its non-use should be the want of
money and the power to borrow it. But there are
always enemies to progress those who say, What
was good enough in old times is good enough
now ; those who ignore the results of comparative
experiment ; the faddists ; and those who condemn
without examination.
Now what are the disadvantages of asphalt ?
The wise man who has to judge a new material or
process may make two columns on a sheet of paper,
inscribe in the one the advantages, in the other
the disadvantages ; the balance is one side or
the other then he knows what course to pursue.
Now a smooth pavement is unsuitable to horses
with a load to drag. There is no grip, and it
may be laid down that, in almost all circumstances,
3 in 100 is the maximum gradient for compressed
asphalt roads.
Again, in the temperate zone there will be some
days in the year when it drizzles. Then the fine
dust lying on the asphalt is at once converted
into a thin pellicle of sticky mud, which may cause
horses to slip unless well held up by their drivers ;
a heavy rain does no harm, indeed it does good by
washing the surface.
In Paris, where compressed asphalt was first
used, there are bins in the foot-paths or side-walks-
containing stores of fine red sand.
The scavengers at once sprinkle the asphalt
surface ; the men use a wheelbarrow and
NATURAL ASPHALT. 2$
shovel, giving the latter a smart twist at the
moment of throwing, which scatters the sand
uniformly, and slipping is prevented ; but the better
plan, which is also used in Paris, is to screw the
hose on to the street hydrant and flush the surface,
afterwards using the squeegee.
When a horse falls on asphalt he does not
break his knees as he would on stone setts or
macadam.
Some sand, ashes or cinders thrown will facilitate
his rising, or a cloth thrown under his fore legs.
Horses get accustomed to asphalt, and must
like it, at any rate 340 days out of the 365, as the
traction is so much easier than on stone, macadam,
or wood.
It is quite clear that when improved roadways
are made, there must be provided also improved
modes of cleansing them.
Compressed asphalt must be kept clean from
horse-dung and other impurities, and be flushed
once at least in 24 hours, either by hose and hydrant
or by water cart, and then squeegeed.
In big towns there should always be a complete
organization for street-cleaning ; dust, mud, and
filth must be removed for the health and comfort
of all citizens, tax-payers or not.
Dry east winds do not only arrest the action of
the liver, but the parched state of the roads allows
of poisonous dust being conveyed to the respiratory
organs. " Wash and be clean " applies to streets as
well as to human bodies.
26 NATURAL ASPHALT.
The author, who has lived most of his life on the
continent of Europe, was, in a recent visit to London,
walking up from Victoria Station to Westminster
Abbey by Victoria Street. During this short walk,
at four points miserable crossing-sweepers impor-
tuned him for making a passage across a coating of
slimy mud, which in Paris would have been cleared
away before 8 a.m. ; but when wishing to cross the
same roadway from the Abbey to Great George
Street, there was such a sea of slush on the spongy
wood pavement that he was compelled to carry
his twelve-year old daughter across as though it
were a river ford.
Later on the author saw a house in Trafalgar
Square, the walls of which were literally black as
soot, and was informed that it was the College of
Physicians. Dear old London ! the richest, and,
after New York and Chicago, the dirtiest city in the
civilized world. When will it be kept like Paris ?
Yet there are able-bodied paupers of both sexes
in the workhouse, doing nothing for their board and
lodging, who would make excellent sweepers.
Local Boards must learn to vote money for street
cleaning.
Durability. Compressed asphalt, subjected to
ordinary wear and tear, will last without complete
renewal from 15 to 30 years; for instance, the
compressed asphalt laid in Cheapside in 1870,
resisted the central traffic of London for over 17
years, without causing a single day's stoppage of
NATURAL ASPHALT. 2/
traffic; and there are streets in Paris where the
asphalt is over 30 years old.
Fig. 15. COMPRESSED ASPHALT FROM PARIS ROADWAYS.
Fig. l6. COMPRESSED ASPHALT FROM PARIS ROADS, REDUCED
BY WEAR FROM 2 INCHES TO T 9 F THS INCH.
The life of an asphalt roadway depends upon
the number of vehicles passing in 24 hours, their
28 NATURAL ASPHALT.
weight and speed, the use of brakes ; also upon the
amount of rainfall, of frost, of hot sun.
Repairs are made in dry weather with hot
powder, and a careful workman will not let his
jointing be visible.
Fig. 17. COMPRESSED ASPHALT FROM PARIS ROADWAYS,
REDUCED BY WEAR FROM 2 INCHES TO T VTHS INCH.
In persistently cold, wet, foggy weather, holes
can be temporarily stopped by liquid asphalt in
two layers, but a dry surface of concrete can be
obtained by spreading a thin layer of liquid
mastic over it.
Malleability. Asphalt, particularly in its form of
mastic, is slightly elastic, and at ordinary tempera-
tures (say 60 Fahr.) ductile.
This gives it the advantage over cement coatings,
which are non-elastic, and therefore crack and-
crumble. Cement once used is lost, whereas
asphalt mastic, like lead, can be used over and
over again by adding new refined bitumen.
NATURAL ASPHALT. 29
In Paris, where there are many trees in the
public thoroughfares, the roots often force up the
footpaths or side-walks, yet the asphalt mastic
rarely cracks, although it contains a large propor-
tion of grit ; it bulges up only. In a pure state,
and without grit, it might be folded double without
cracking.
Not affected by Frost. This quality allows of
snow being removed from it with ease, and there
ensues no perceptible contraction or expansion,
however sudden the changes of temperature may
be. In this respect it compares favourably with
wood pavement, which swells up after rain, or frost
following rain, the force of which expansion is
resistless, pushing up kerbs, overturning street
lamps, or in case of the over-resistance of a party
wall buckling up on itself.
Not affected by Heat. Its nature is not altered
thereby; it softens slightly under extreme day heat
(say 1 00 Fahr.), but returns to its original form at
sundown. It is a non-conductor.
Vermin. It repels rats and mice, perhaps by its
smell, but chiefly by clogging up their teeth : thus
in Paris, where there are as many rats as Parisians,
the sidewalks are undermined, but the gritted
asphalt mastic is never gnawed through, yet cement
is attacked.
This quality renders asphalt excellent for
30 NATURAL ASPHALT.
stables, granaries, stores, warehouses, corn-mills,
breweries, malting-floors, distilleries, dairies, cheese
factories, &c.
Perfection is not of this World. Asphalt has, as
the French say, " the defects of its qualities," as
being impervious to water ; condensed atmospheric
water remains upon it instead of being absorbed.
The only remedy for this inconvenience is a coarse
sponge, or an oakum swab. Asphalt does not
hide damp, it discovers the enemy which, being
seen, can be grappled with.
The best tool for removing moisture from a hori-
zontal asphalted surface is the invaluable squeegee.
It is also well to remember that asphalt, like
indiarubber, has no great powers of resistance per
se, but is strong when supported by solid founda-
tions or defended outside by vertical masonry.
Noiselessness. It is of course owing to the pre-
sence of mineral bitumen in the limestone which
causes percussion and vibration to be absorbed ;
also to this peculiar fact, that in a compressed
asphalt the roadway is always of closer texture
than the underlying parts. This is just as per-
ceptible in asphalt worn to less than half its
original thickness. (See Figs. 15 and 1 6 ante.)
The sound of the horses' hoofs is heard as a
sharp "toc-toc," without vibration or resonance,
warning the pedestrian of an approaching vehicle,
while the rolling of the wheels is noiseless, for the
NATURAL ASPHALT. 31
wheels do not bump on asphalt as they do on stone
or macadam.
On wood pavements the sound of the horses'
hoof is not heard a danger for deaf or careless
crossers.
It has been said indeed, that wood pavement
cures deafness by killing off the deaf.
Agoraphobia. In these modern times a new
malady has arisen. Agoraphobia is the mental
suffering caused by street noises of all kinds, but
particularly the rumbling of heavy vehicles on
granite setts or cobble pavements.
In Paris, for the last twenty-five years, land-
lords, managers and heads of schools, churches,
theatres, banks, as well as private householders,
have clamoured for compressed asphalt road-
ways, in some cases, where the stone road was new,
paying 2s. 6d., or say 60 cents, per foot run for the
substitution.
Since the cholera scare (1892), a large number of
narrow streets and blind alleys, and small yards
have been asphalted for hygienic reasons.
The imitation of natural asphalt will be treated
further on.
It is an old adage that "imitators always fall
short," and when the difference in price is so slight
between the two articles, it is not worth while to
encourage the imitation.
The only excuse for using imitations is their
low first cost, and that is false reasoning, for the
32 NATURAL ASPHALT.
increased cost of repair is infinitely greater than
would have been the interest on the additional
outlay for the real article, besides which, the com-
plete break-up which always ensues, involves the
cost of relaying, after all the annoyance to the
neighbouring householders and shopkeepers caused
by the repairs.
Asphalt Fiasco in Paris. In 1878, the City
of Paris let its tried contractor go, tempted by
the low prices of a reckless bidder, with the result
than in 1883, Paris asphalted streets had gone to
the dogs, and had to be relaid in 1884, at a cost of
6,000,000 francs (240,0007.) or 1,200,000 dollars.
The contractor, who had deceived himself as well
as the town, died in a mad-house, leaving a host of
creditors with zero for assets, who blamed the town
authorities for being the indirect cause of their
losing their money, they believing that a munici-
pality only employed solvent and honourable
contractors.
Wood Pavement. About the year 1840 wood
was used for roadways, found wanting and aban-
doned ; but since about ten years ago, owing princi-
pally to the failure of bad asphalt in Paris alluded
to above, it has been largely used. When laid upon
a Portland cement concrete bed, it is certainly a
great improvement upon macadam, indeed, when
first laid it is admirable ; but it is not a hygienic
pavement, because it is porous. As animals have not
NATURAL ASPHALT,
33
yet been trained to use water-closets and urinals
the public highways are defiled with their dung
Fig. 1 8. WOOD PAVEMENT CUT FROM PA'RIS STREETS.
and their urine ; these, as well as other filth, are
absorbed by the wood, and ferment in its fibres.
D
34 NATURAL ASPHALT.
Under a hot sun, morbid germs are drawn up
into the atmosphere and inhaled by the inhabitants,
stunting the growth of children and debilitating
adults.
The surface of wood pavement becomes, after
one, two, or three years, according to traffic, like a
Fig. 19. PULVERIZED WOOD FIBRE MIXED WITH HORSE-DUNG
AND OTHER IMPURITIES, FROM WOOD PAVEMENT.
worn-out tooth-brush (see Fig. 18, representing a
block taken from a Paris street after one year's
wear).
The fibres from this disintegrated surface, mixed
with horse-dung and filth, are pounded and ground
up by the traffic (see Fig. 19), and in this form, on
a dry day, are swallowed by the citizens, or carried
home in their hair and garments.
Since the introduction of wood pavement in
London and Paris, oculists have found inflamma-
tion of the white of the eye (conjunctivitis) greatly
on the increase. Such a fact is not astonishing, as
dust from decayed wood pavement is poisonous.
NATURAL ASPHALT. 35
Wood pavement, to last, should be kept always
wet, but wet wood has a most lugubrious appearance.
In winter, when the frost gets into it, the surface
becomes glazed to such an extent that horses
cannot move on it without slipping ; it is dangerous.
An eminent English engineer once said of wood
pavement ; first year excellent, second year good,
third year bad, fourth year very bad, fifth year
take it away. As before said, when laid on
concrete with a certain slope, wood has its advan-
tages, the joints give a foot-hold to the horses on
an incline, and the water can get away, but on the
flat, the rain water which percolates down to the
concrete, but cannot penetrate it, rots the wood at
its base.
In New York, Berlin, and the City of London,
wood is no longer used, but it is employed in the
London suburbs and in Paris, in which latter
streets, the municipal authorities lay it themselves
without the intervention of a contractor, as do also
certain London parishes.
Dr. J. B. Fonssagrives in his excellent and most
interesting work ' Hygiene et Assainissement des
Villes '* says (p. 19), " Hygiene cannot approve of
the covering of a road by a porous substance, apt
to become impregnated by organic matter, and
supplying by its own decomposition miasmata,
which, let loose from such an extended surface,
cannot be disregarded. / am convinced that in a
* Paris, J. B. Bailliere et fils, Rue Hautefeuille.
D 2
36 NATURAL ASPHALT.
damp town entirely paved with wood, marsh fever
would become endemic?
There is another danger, viz. that in case of riots
the wood blocks smeared with petroleum and set
alight, might aid the criminal design of incendiaries,
as in the case of the Paris Commune in 1871.
Traction on Compressed AspJialt Roads. Many
dynamometrical experiments have been made to
arrive at the coefficient of traction for each kind of
road, and have yet to be scientifically carried out.
Evidently, such experiments should be made with
vehicles of the same weight and diameter of wheels,
same width of tire, on same level, with same condi-
tions of temperature and dryness, same speed,
horses shod the same without calkins or toe-pieces ;
but it may be taken roughly that the traction on
asphalt, say at 75 Fahr., being I, that of stone'setts
will be 2, of rough granite and ordinary macadam
3, on rough macadam 5 to 6.
37
PART III.
MODE OF SETTING OUT COMPRESSED ASPHALT
ROADS.
THE first thing to be considered is the camber,
which is pitched much lower than for wood, stone,
or macadam, because the asphalt surface being
smooth, as well as impervious, the water runs
away to the gutters more easily.
After trials of many cambers during the last
twenty years, the author concurs generally with
the following formula, drawn up by the late
M. Saint-Ange Allard, Chief Engineer of the City
of Paris. The figures are millimetres, and are thus
given because the metrical system is now so much
used.
W 2
R = 0-012 metre ^rr^.
R = rise of camber, the perpendicular at
highest point.
W= width of roadway.
Thus, supposing a roadway to be 12 metres or
13 yards wide from kerb to kerb, the rise would be
0*157 metre at the centre or crown, or 6^ inches,
but as we take off I metre or 3 feet 3 inches from
3$ NATURAL ASPHALT.
the kerb to form the gutter measuring from that
last limit, the rise is nearly 0*109 metre, or
4^- inches.
The best way to lay out a 12-metre or 1 3-yard
wide road is to take the centre, measuring from
inside the kerbs, which are presumed to be on
same level. Then take a plank, say 6 metres or
ipj- feet long, i foot in width, and say ij inches
thick, upon the side of which trace the following
diagram :
Fig. IQA. MODE OF SETTING OUT CONTOURING-BOARDS.
N.B. Vertical scale much exaggerated.
Let A B C D (Fig. IQA) be the configuration, A C
the side of the granite kerb, which is 1 2 inches high,
and B D the centre or crown of the road at the
highest point, where it is divided thus into two
equal parts.
Measure 3 feet 3 inches (i metre) from the kerb to
form the gutter, which requires a greater fall, other-
wise in rain storms, and flushing, the water would
spread too far over the road ; raise a perpendicular
0*048 m. or ij- inch high, then by joining E and
F we have the gutter, which is not steep enough
NATURAL ASPHALT. 39
to cause cart and horses to slide towards the
kerb, but sufficiently so to keep the flushing water
from spreading and becoming too shallow to carry
away the street rubbish, when not too bulky, to the
gullies.
At the point D, we trace the perpendicular to
get the rise, after deducting the width of gutter,
which gives o* 157 m. 0*048 m. = 0*109 m. or
6 inches ij inch = 4f inches is the height of the
perpendicular D O. Joining O to F by a hori-
zontal straight line we obtain the subtense of the
curve. To obtain the intermediate rise we" take
the fourth o* 109 m. = 2^ inches at the point H ;
at half the distance from E to D we raise the
perpendicular H I, where it is prolonged to J. By
joining the points O J and F C as carefully and
regularly as possible, the camber of half the road-
way is obtained. One can always get other points
by making further similar subdivisions, but in
practice it is hardly necessary.
Now, to get the camber edge all that is
necessary is to saw the plank according to the
curve ; C O D then comes away as waste.
In cases where one kerb is higher than the other,
the highest point, or watershed, of the roadway is
of course no longer in the middle, but, propor-
tionately to the difference between the height of
the kerbs, is advanced towards the higher one, but
the formula is applied in the same way.
In old cities there are tortuous narrow streets
where sometimes the left kerb, sometimes the right
40 - NATURAL ASPHALT.
one, is the higher, which causes a good deal of
trouble in setting out. (Fig. 20 represents a road-
way in which one kerb is 4 inches higher than the
other) ; the highest rise of the camber is no longer
!3 Yards
. 20.
23'. O"
______________ 36'. O" _____________________________________
Fig. 21.
the centre A. A longer slope must be given to the
side of the inner kerb, so as to correct the inequality.
The rise would be at B, from which point the usual
fall of 2 in a hundred would be given to the points
M and N, and from thence to the kerb a fall of
3^ in a hundred.
For a cross road where the kerbs of each street
are unequal, by drawing a straight line from each
rise we obtain at their intersection the highest
point of the cross road, from which the usual fall
of 2 in 100 must be given, so that the water may
run off freely.
.As cross ways have about double wear and tear,
they should have extra thicknesses of concrete and
NATURAL ASPHALT. 41
asphalt. It is generally the engineer or surveyor
who gives the points, and the case is one where much
practice and experience does as well as science.
18.0"
24-'. CL*_
Figs. 22, 23, and 24. IMPLEMENTS USED IN CONTOURING
ROADWAYS.
The Soil. After removing all plaster and soft
clay, the soil must be well rammed to camber
and well watered to indicate holes ; should any
holes be found they should be filled in with sound
material.
Concrete. From 1871 to 1878 the author was
greatly troubled by being compelled to work
with hydraulic lime concretes which were never
dry, and formed the opinion that only the best
Portland cement concrete could be used with
safety for compressed asphalt. Cases of failure
in laying stone setts, or wood blocks, can be put
42 NATURAL ASPHALT.
right at the expense of the labour ; but a failure in
compressed asphalt means a much more serious
loss, namely labour and material, which latter
must be carted away, cleaned, and ground up for
mastic. Relaying annoys the householders, who
blame the engineer or architect as well as the
contractor.
The best mode of making concrete for asphalt
roads is, to say one part of fine-ground Portland
cement of best quality add three parts of clean sharp
river sand, and four parts of clean pebbles that will
go through a ring of 2j inches diameter, or one
part of cement as above to seven parts of clean river
ballast, mixed dry, well shovelled together and
then just sufficient water added to make it moist
(too much water lets the heavy cement fall to the
bottom). This mixture is laid out with a flat oblong
shovel and afterwards levelled off with a straight-
edge and smoothed off with the flat shovel so
that the fluid part comes to the top, and thus the
application of a floating is avoided ; of course, a
little mortar must be handy to fill up any cavities
after passing the straight edge.
The old plan of spreading a floating over the
concrete is injurious, because (i) it does not set at
the same time as the concrete, and (2) it gets
crushed under the blows of the rammers when the
powder is laid.
Some contractors increase the proportion of
flint pebbles and sand. One part cement to nine
of ballast is used often.
NATURAL ASPHALT. 43
In very hot weather such a concrete will be
ready in four days, but in winter seven days is not
too much. If it is white on the surface one may
be sure it is dry.
Latterly, concretes have been laid during the
existence of 20 Fahr. of frost, by using water heated
to 85 Fahr., in every gallon of which I Ib. of
carbonate of soda has been dissolved. It is certain
that concrete made thus in the depth of winter
is dry and apparently sound. The Portland
cement mortar sets rapidly, as if it were Roman
cement. The action of the soda seems to set
back the freezing-point. Whether the process is
absolutely safe, only experience can decide.
Time of Laying Asphalt. In Europe the best
time is between the months of May and October,
but work often gets done much later, provided
there be no frost and snow or continuous wet.
Hot Asphalt Powder. The powder should be
heated from 275 to 280 Fahr., not only to soften
its contained bitumen, but also to evaporate the
natural moisture contained in the crude rock or
powder, which may amount to from I to I J per cent,
of the weight.
Great care must be taken to rake out all burnt
or charred lumps, which are inert matter.
While the powder is in the carts it must be well
covered with tarpaulins of asbestos, or other cloth,
and after being transferred to the wheel-barrows
for spreading should be covered with cocoanut
44 NATURAL ASPHALT.
sacking, as soon as spread it should be rammed
with the hot rammers ; the less heat lost by the
powder before ramming or tamping the better. No
foreign bodies should ever be left in the powder or
concrete.
The powder along the kerbs must be rammed
with a special oblong rammer, which is also used
for making joints, and a 12-foot wooden straight-
edge should be pressed close home to prove that a
level surface has been obtained, so that no hollows
for puddles can remain. Any bumps must be at
once rammed down while the material is still hot.
When the whole surface just rammed is level it
must be smoothed with the hot smoothing-irons so
as to glaze it and leave no rough face to hold
water, then a little fine Roman cement may be
sprinkled over and swept in with a soft broom, and
the whole rolled with a heavy roller.
If the job can be left for three days so much
the better, the atoms will cohere and take their
permanent set, but in cities it is difficult to get more
than 24 hours, during which time, if the weather be
hot, the new road may be rolled with two-wheel
carts or trumbrels, first empty, then gradually
loaded up ; this will consolidate the asphalt and
prevent wheel-marks when the street is thrown
open to traffic, but in cool or wet weather the cart
rolling is not necessary.
The following is the composition of a gang for
the laying, say of 500 square yards in a day of ten
hours.
NATURAL ASPHALT. 45
2 men (first and second foreman) to rake out the powder when
dropped from the barrows, and spread it in a layer of equal
density.
2 men to make the joints along the kerbs or drain openings,
fire plugs, c.
12 rammers.
8 smoothers or ironers.
2 men to roll the heavy hand roller.
4 men to roll the wheelbarrows of powder from the horse carts
to the site.
Supposing that a 2-inch layer of compressed
asphalt be ordered, it is well to trace with a
chalked string two chalk lines along the kerb, the
upper one for the loose powder, the lower one for
the layer after full compression. Some asphalt
powders are denser than others, so it is v/ell to get
the weight of say 24 Ibs. to the square foot.
The plate (see p. 46) shows a square 100,000
square feet in extent, in which can be observed the
operation of concrete-making and powder-laying.
If the proper weight per square foot be given,
the roadway will roil down level and to a uniform
thickness of two inches under traffic.
Footpaths or Sidewalks of Compressed Asphalt are
often laid instead of gritted mastic. The light
colour is agreeable to the eye and harmonizes with
stone buildings ; no surface can be nicer or less
fatiguing to walk on.
Gritted Mastic Footpaths or Sidewalks. A slope
of i in 50 from ' hreshold to kerb is about what is
Fig> 25. ASPHALT OF THE SQUARE IN FRONT OF NOTRE DAME, PARIS-
ioO,000 SQUARE FEET, EXECUTED BY THE COMPAGNIE GENERALE DES
ASPHALTES DE FRANCE. CONCRETE BEING LAID SIMULTANEOUSLY
OPPOSITE THE WEST FRONT OF THE CATHEDRAL.
NATURAL ASPHALT.
47
necessary to let the water run off, and a fillet of
pure mastic should be laid alongside the thresholds
where there is any danger of infiltration, paid for
extra.
A 4-inch depth of Portland cement concrete and
layer of mastic is sufficient, except for courtyard
Fig. 26.
entrances, where 6-inch concrete and 2-inch layer
of mastic is necessary, the latter in two layers, first
smooth, second chequered or cross-cut to afford a
foothold to horses.
As before mentioned, in case of repairs, gas
trenches, &c., the old materials can be used over
again.
Twenty minutes after laying, the surface can be
walked over ; it is agreeable to the foot, not hard
NATURAL ASPHALT.
49
nor slippery like cement or granite flags, which in
dry weather are slippery, even dangerous.
These famed asphalt promenades are like an
impermeable carpet, only never dusty nor dirty if
regularly washed down and squeegeed.
The broad Parts Boulevards would lose half
Fig. 28. PORTABLE FURNACE AND BOILER FOR TRANS-
PORTING HOT MASTIC.
their charm were they laid in any other material
than asphalt ; it is the cheapest and the best non-
absorbent, smooth and safe.
In hot climates, where frost is not dreaded, more
than the usual proportion of 40 per cent, grit may
be added to the mastic paste ; the gritted mixture
UNIVERSITY )
/
V f**..
5O NATURAL ASPHALT.
should be run hot, pressed, and rubbed in with
slate powder or fine sand.
In the large European towns London, Paris,
Brussels, &c. the gritted mastic is cooked in
Fig. 29. ASPHALT MASTIC KETTLE WITH ACCESSORIES.
MASTIC CAKES BEHIND.
boilers holding 5 tons, driven by steam-power, and
the hot material sent out in heated portable boilers
(Fig. 28) holding above I ton.
This saves blocking the street, and the old
materials are carted away by the same vehicle,
which has a box for the purpose.
NATURAL ASPHALT. 5 1
Asphalt kettles are used for work inaccessible to
portable boilers.
When used on the public roads, they are put
on a layer of sand to prevent damage to the road
from the heat and cinders.
A cake of Seyssel mastic, weighing say 56 Ibs.,
will lay about n square feet of surface, -fg inch
thick, when the grit and bitumen has been added.
First, the kettle being heated, and the cake
broken into small pieces by blows from a small
sledge hammer, about one-half of the bitumen to be
used, say from 5 to 6 per cent, of the weight of the
pure mastic, is put in, then when the paste is made
by the addition of the pieces of mastic to the bitu-
men, the dry grit and half the remainder of the
bitumen is added (one-fourth of the whole), the
rest being kept till the end of the mixing.
The grit is laid on the top of the mastic, and
allowed to sink in, and must afterwards be kept
constantly stirred. A regular heat must be kept
up, not less than 280 Fahr. nor more than
360 Fahr.
Wood or coal or even coke may be used as fuel,
and the kettles kept clean by a chisel and hammer.
The bottoms are movable, as they wear out soon.
In spreading the mastic, there must be no steam
bubbles, which arise from wet concrete.
Fine sand dries a wet concrete, and during wet
weather, if spreading is compulsory, the mastic
should not be too hot.
There must be no hollows where water can lodge.
E 2
52 NATURAL ASPHALT.
To get the thickness an iron rule may be used, which
as it lies on a rough surface should be a little less
thick than the layer to be spread.
Inexperienced asphalters sometimes manage to
make the surface-water run in the wrong direction,
for instance into a house instead of from it.
It must never be forgotten that we are dealing
with an impermeable material.
Mastic is ready to lay when it does not stick to
the wooden spatula used for spreading, or by the
workman's test, when it instantly evaporates
spittle.
For Coatings of Masonry. Mastic should be
used pure, and laid in two layers, each about J inch
thick, taking care to cover the first joints i. e.
that the joints of the two layers may not be directly
superposed.
A recess cut in the masonry and filled with
mastic is an extra precaution.
For Casemates. Military engineers will some-
times have a brass rose and drain-pipe inserted in
the mastic where several seams meet, so that the
water may be carried off. The rose is surrounded
with rubble to keep the dirt off. Otherwise the
water remains underneath the bomb-shell proof
earth covering till absorbed by same.
When a flat roof is asphalted, as is so often the
case in countries where no snow falls, and is used
NATURAL ASPHALT.
53
as a belvedere or a drying ground, it is well to lay
two layers of mastic the first pure, the second
gritted.
The palace of the Trocadero at Paris was laid
thus in 1877, and forms an excellent promenade for
the public.
Fig. 30.
For Siloes (Figs. 3 i, 32). The application here is
the reverse of a casemate, and where green fodder
is earthed for winter use or grain stored. No
moisture from the surrounding earth nor any
vermin can get in.
Vertical Applications are made in pure asphalt
mastic to keep out rising surface-water and dampness
generally from walls ; the material is smeared on
and rubbed in as though it were plaster, and with
54
NATURAL ASPHALT.
Fig. 32.
NATURAL ASPHALT. 55
plasterer's tools. The wall must not be damp at
the time of the application, and it is well to dash
some hot liquid bitumen against the wall surface.
Two men are required, one to spread and the other
to briskly rub in.
Such work is worth nearly double the price of
horizontal spreading.
It must always be borne in mind that asphalt has
not much power of resistance of its own it must
be supported by a wall built up progressively
with the vertical application.
Electricity. Now that underground wires are so
much used, it has been found difficult to obtain a
good conduit ; cement-concrete cracks and lets in
water, iron causes the current to reverse ; if the
wires are placed naked in the earth there is too
much leakage.
The author submits a plan with a drip-groove
at each end of the lid (Fig. 13, ante, p. 18), which
will be watertight and not subject to crack.
From the wires that convey the fluid for lighting
purposes at the Paris Opera House (1890), there
was 30 per cent, leakage, owing to the condensed
water from the engine getting into the covered
conduits and rotting the hempen and gutta-percha
coating off the wires.
As there was no time for making proper repairs,
the author rilled up the conduit with hot gritted
mastic, drowning the wires. This was a rough and
ready remedy, but absolutely efficacious.
NATURAL ASPHALT.
NATURAL ASPHALT. 57
Asphalt Flags and Slabs (Fig. 33).
A is a wrought-iron tank containing hot
water.
B is a wooden tray on which the asphalt slab
is laid for immersion.
C is a stove.
D, D, jointing irons with sharp edge for remov-
ing overflow.
E is a ladle for melting the special jointing
mastic it fits on the stove.
F is a wooden rule for proving level surface.
H, I, are slabs, smooth and chequered.
The flags can be sent by railway any distance,
and any intelligentlabourer can lay them in towns,
stables, out-houses, schools, &c.
58 NATURAL ASPHALT.
PART IV.
GENERAL OBSERVATIONS.
Width of Tires Heavy Goods Traffic. There is
a proportion between the width of the tires of
four-wheeled vehicles and the weight they carry :
thus
Weight carried on four wheels. Width of Tire.
2 tons 2 inches to 2^ inches.
2j ,, to 4 tons 2j ,, to 4
5 4 to 6 ,,
7J 6
The diameters of wheels of course vary ac-
cording to class of goods carried and width of
streets.
If such rules were carried out, roads would last
longer, but to avoid friction some carters and van-
drivers use narrow, rounded tires, which cut like a
knife, particularly if the gauge of the fore wheels
be the same as the hind ones.
When a powerful lever brake is applied, locking
the two hind wheels and causing a heavy vehicle to
slide along in varying directions for a distance,
say, of half a dozen yards, the road suffers ; the trace
left by the wheel is hot.
Spreading Salt on Roads in Snowy Weather.
NATURAL ASPHALT. 59
This is a deplorable practice, snow and salt make, a
freezing mixture some 28 Fahr. lower in tempera-
ture than the air.
This mixture runs down into cracks and joints,
and causes disturbance by the expansion of any
wet substance with which it may come in contact
during the congelation of the other.
It does great harm to shoe leather, and chills the
life out of many an unsuspecting wayfarer.
The suffering to dogs who may wade in the
mixture is pitiable.
The medical profession have declared against it.
It certainly melts the snow on tram-rails. It de-
prives frozen-out workmen of the job of clearing
away snow a valuable resource for them.
Kerbs should be laid on a concrete foundation
and be 12 inches wide and of a proportional depth.
Grey granite is the most sightly material, but it
requires facing with wrought iron at corners of
streets where there is heavy traffic.
Where water lies on the concrete near the kerbs,
the author has inserted small iron drain pipes
J inch in diameter. A film of water in a crack
will act like a wedge under heavy traffic.
Speed of Street Traffic. From the experience
of horse dealers, the pace of draught horses has
increased above 25 per cent, since 1872, which
of course means more bumping and consequently
more wear and tear.
6O NATURAL ASPHALT.
Tramcar Rails increase the cost of mainten-
ance of roads, by concentrating the traffic on either
side and augmenting the number of joints.
Tramway companies in Paris have to pay all
repairs within 20 inches distance of each rail or
double rail.
In towns the track should always have an over-
lapping foundation of 20 inches thick Portland
cement concrete, on which the chairs should be laid
direct.
Longitudinal sleepers on ballast are a mistake in
towns.
Contracts for the Maintenance of AspJialt Roads
and Sidewalks require to be made on a fair basis,
to avoid law-suits, oppression, fraud and bank-
ruptcy.
To take an example, a householder buys a
carpet. He of course also pays for laying it down,
keeping it clean, beating it, repairing the holes
which will appear in course of time, and finally
when worn out he buys and pays for another one,
getting for the old one what he can. A munici-
pality must do the same for its roads and foot-
paths, or sidewalks.
Conversion of Old Road Surfaces into Compressed
Asphalt. Supposing a roadway in old stone setts or
cobbles, in macadam or wood, is to be converted
into a roadway of compressed asphalt. The first
thing is to be sure that the drain is made ; then to
NATURAL ASPHALT. 6l
put the gas pipes, electric wires, &c., under the
footpaths,* level up the kerbs and put them on a
Portland cement foundation, cart away the old
materials at the expense of the parish, make the
communication with the water-closets and surface
water pipes with the main drain at the expense of
the householders ; then relay the footpath or side-
walk, and after that, if there be any trouble in the
roadway, it should be well rammed, watered, and an
extra thickness of concrete laid to prevent settle-
ments, which will often occur after three years or
more ; after that the contractor levels the road,
lays the concrete under the superintendence of the
authorities, and in due time lays the asphalt as
before stated.
The job must be stoutly barricaded and the
public kept off, to avoid accidents and let the work
be expedited. There must be a watchman at night
to keep the lamps alight and prevent accidents.
Guarantee. In Paris a road laid as ' above in
August is taken over provisionally on the following
1st May, then, if in good order, it is passed, but
left in the contractor's hands at his risk till the'
3 ist December following; after which, if still in
good order, it is taken over definitively by the
municipality and parish as their own property, and
all repairs are at their charge.
* Unless there be subways, a most valuable adjunct to a road,
of which Colonel Haywood, the City of London Engineer, has
made many.
62 NATURAL ASPHALT.
Payment. Sums on account are paid upon the
engineer's certificate as the work progresses, but one-
tenth is always retained till the definitive reception
has taken place.
Maintenance is of two kinds, 1st that of gas and
water and electricity trenches, changes of levels,
widenings, &c, which is paid according to the
schedule of prices, with a premium for surfaces
from i to 100 yards, also for settlements ; trenches
should always be measured from the bottom not
the top, the contractor removes the earth and old
materials at schedule prices ; (2) Maintenance for
wear and tear.
Now according to the simile of the house-
holder's carpet, the municipality or parish would
keep paying the necessary repairs as caused by
the traffic or " wheel wear," until at a given time it
would have to relay the entire asphalt surface and
level up the concrete bed, if there had been many
trenches, at its own expense. Of course the old
asphalt has a certain value, but it has to be carted
to the contractor's yard, stored, cleansed, ground
up, all of which means expense to the contractor,
who has also to wait the opportunity of using it, so
that it is often given for the cartage as its storage
on expensive land soon eats up its value.
But, instead of paying for its repairs by surface
as required, the town of Paris resolved to pay a
fixed sum per square measure of surface, a sum
based upon its expenses during three years, leaving
NATURAL ASPHALT. 63
all the rest to the contractor, who is at the beck
and call of its engineers, for all necessary repairs,
whatever they may be in extent, which is an easy
method in a large city, and causes a large saving in
figures and red tape.
This sum is 2 francs per square meter, or say
is. ^d. or 32 cents per square yard for compressed
asphalt roadways, and 35 centimes per square meter,
say ^d. or 6 cents per square yard for gritted
asphalt footpaths or sidewalks.
The contract is made for ten years, and at the
end of that time the surface must be in good order,
but of the thickness no note is taken.
It may happen under such a contract that the
contractor may lose money upon the maintenance
of certain streets, but others will give him a profit
and so compensate.
Of course under such a system the contractor is
not supposed to lose, still he often does, owing to
prolonged bad weather, unusual traffic, bad con-
crete, &c., so that it is usual to give him all new work
up to 3OOO/. or 1 5,000 dollars, without rebate.
The system of paying a fixed price for repairs
of whatever extent is a risk for the contractors, and
if undue severity is exercised by the authorities
may lead to his ruin, but it is never the interest of
a municipality to punish an honourable contractor.
Still, coercive means are reserved for dishonourable
contractors, and caution money is required for
large contracts which may rise to I2,ooo/. or 60,000
dollars, bearing 3 per cent, interest.
64 NATURAL ASPHALT.
The city of Berlin requires a 5 years' guarantee,
and pays maintenance for 15 years afterwards.
Caution money is required, for which 4 per cent, is
paid ; but the traffic of Berlin is easy compared to
that of London, and above all to that of Paris,
which is the heaviest known.
The city of New York requires a 5 years'
guarantee for some work and a 15 years' guarantee
for other, maintenance of which must be included
in the bid for the whole time.
New York does not vote annual sums for main-
tenance as other towns do, and instead of caution
money requires bondsmen ; two-thirds of the money
is paid down and the other third paid in small
sums until the guarantee is expired.
The system is not so good as that of Paris or of
London (which latter is nearly the same as that of
Paris), or of Berlin, because contractors cannot
calculate how much the wear and tear of a big
town increases. It is certain that many streets at
the end of ten years will have cost as much to
repair as was paid for the asphalt, including con-
crete, when laid.
One well-known contractor in New York has
preferred (1892) to abandon say 142,000 dollars
owing to him by the municipality rather than con-
tinue repairs, which at the end of 1 5 years will have
cost three times that sum or more.
The only one who can gain by this is the out-
side contractor called in to do repairs as long as the
funds last.
NATURAL ASPHALT. 65
The city of London requires two years' guarantee
for new work, after which it pays a fixed sum for
maintenance per square yard during 15 years,
according to the traffic of the street.
Thus, Cheapside, London 2j-inch compressed
asphalt on 9-inch Portland cement concrete was
paid iSs. or 4*32 dollars per square yard, and, the
guarantee time expired, is. 6d. or 36 cents mainte-
nance per square yard during 15 years.*
The author has been informed that Cheapside,
which was and is a marvel of endurance, was a loss
to the contractors in the latter years before it was
relaid.
During the whole of the 17 years this important
thoroughfare was never stopped for repairs, i.e. from
1870 to the end of 1887, although when the old
granite setts were used, it had to be relaid every
4 years.
It was relaid at the rate of 800 square yards a
day with comparatively little inconvenience to the
public.
Low Prices. It is not well for a contractor's prices
to be cut too low ; experience has shown that very
low prices mean one of two things, either ruin to the
contractor, which is a public misfortune of frequent
* See the report of Colonel Haywood, Engineer and Surveyor to
the City of London, Engineer's Office, Guildhall, London. It
was this distinguished engineer who introduced compressed
asphalt into London, in 1869 a boon indeed for those old narrow
streets and alleys.
F
66 NATURAL ASPHALT.
occurrence, or else cheating, i. e. substitution of
second class materials, insufficient thicknesses,
&c., when the town suffers sometimes found
out too late. Fraud is always more active than
supervision.
Poor human nature must not be tempted too far.
High duties produce smuggling; excessive income
tax leads to false returns of income ; very low
prices in contracting lead to cheating.
Municipalities should encourage honourable con-
tractors who do good work, by only allowing those
contractors to compete for important jobs who
have capital, plant, good materials, and an un-
blemished reputation.
A needy, incompetent and dishonest contractor
does infinite harm to those who trust him, whilst
doing no good to himself.
Imitations of Natural Asphalt. These are of
two classes, the first and foremost is a material
made of white limestone sand, and Trinidad or
other mineral pitch.
Trinidad pitch always contains 25 per cent, of
clay, whereas the bitumen or pitch naturally con-
tained in asphalt rock is chemically pure.
Bitumen can be added to natural asphalt, be-
cause nature has shown the way.
If you have an oil stain in a piece of cloth,
and pour fresh oil on, it will soak into the part
already stained much more readily than into the
part still intact.
NATURAL ASPHALT. 67
The fact is, that it is about as easy to imitate
natural asphalt as to imitate granite or coals.
There is no chemist like nature. However, in
the United States, a man of great natural gifts and
extraordinary energy, Mr. Barber, has founded a
powerful company for making roadways of the
Trinidad pitch compound above alluded to.
Of this artificial compound, more than 5,000,000
square yards have been laid in various towns of
the great continent. It resists well enough where
there is little traffic, but tried in Paris, Berlin, and
the heavy traffic streets of New York, like Wall
Street and Chambers Street, it scales away at the
surface and breaks up rapidly.
Mr. Barber is preparing the way for a better pave-
ment, i.e. compressed natural asphalt. In America,
as elsewhere, the best article always comes to the
front in the end, and the best is always the cheapest
in the long run.
Some engineers will argue that it is well to use
a cheap though inferior material for streets with
little traffic.
The author, however, would venture to assert
that it is always advantageous to use the best
material, and arrive at lower prices by modify-
ing the thicknesses of the concrete and asphalt
layer.
Yet in Berlin the town engineers have always
laid 8-inch Portland cement concrete, and 2-inch
asphalt, and probably in the end their plan is most
economic, as streets with small traffic often become
68 NATURAL ASPHALT.
streets with heavy traffic in the course of 20 years,
say.
In London, during the year 1871, many imitation
asphalts were tried such anomalies as "iron as-
phalt," " india-rubber asphalt," " granite asphalt,"
" slate asphalt." They have all disappeared only
the real article remains.
In Paris, about 1880, a plan of sprinkling asphalt
powder with collodion to soften the bitumen was
tried, instead of heating, the object being to allow
of repairs being done in wet weather without
vaporising the water, as the hot asphalt powder
does, thus causing nodulous formation in the com-
pressed layer.
The inventor had used collodion for moistening
gunpowder, and of so obtaining a greater com-
pression in the cartridge, but he forgot that
heating was necessary, not only for softening
the bitumen, but also for chasing away the i
per cent, of water contained in the natural rock,
and which, if left in, would cause breaking up in
frosty weather.
This so-called cold asphalt has long disappeared
from the streets of Paris.
The second imitation of natural asphalt is made
by using shale-oil, or petroleum-still bottoms,
instead of Trinidad, and mixing sand with lime-
stone. This compound goes soft in summer, and
has little power of resistance.
The third and most redoubtable imitation is that
in which gas-tar is used instead of bitumen, on
NATURAL ASPHALT. 69
account of its cheapness. Mastic made with gas
tar, is soft in summer and brittle in winter.
When used under its own name of gas-tar mastic,
nothing can be said ; unfortunately, having nearly
the same colour as natural asphalt mastic, it gets
palmed off as the real article, although the ap-
pearance, the fracture-colour and smell are not the
same. That does harm, as the engineer and
architect, once deceived by an unprincipled con-
tractor, may afterwards taboo real asphalt, and
prefer to it cement, tiles, bricks, &c.
Gas-tar mastic can be detected otherwise than
by the result it gives ist, by its acrid odour ; 2nd,
its metallic sound when cold, its fluidity when hot.
Gas-tar contains the aniline dyes, which are not
found in mineral pitch.
It would be better for gas-tar to be used for its
chemical derivatives, or for agglutinating coal-dust
(compressed fuel), than for making imitation as-
phalt, which is not trustworthy, even when free
from atmospheric influences.
Traffic of Paris. Asphalt streets laid by the
Compagnie Generale des Asphaltes de France, the
originators of the system :
RuedeRivoH ..
Rue Croix des Petits Champs do. 20,480
Rue St. Honore do. 19,672
Rue Auber do. 14,082
Avenue de la Grande Arrnee .. do. 8, 149
70 NATURAL ASPHALT.
Whereas the highest traffic in London for as-
phalted streets is
King William Street
("number of vehicles)
\passing in 24 hours/
26,793
Gracechurch Street..
do.
15,585
Queen Victoria Street
do.
i6,53i
Cheapside . ..
do
i 5 , 206
Aldgate
do.
14,200
Holborn Viaduct
do.
12,158
Newgate Street
do.
13,128
Moorgate Street
do.
n,398
Cornhill
do.
9,572
These figures are taken from a report by
M. Barabant, late chief engineer of the city
of Paris, now general manager of the Eastern
Railway Company of France.*
Macadam. The wear and tear of macadamised
roads in Paris, the extent of which is, say 2,167,800
square yards, or -f^ of the entire surface of Paris
roadways,f absorbs daily 390 cubic yards of
materials or a train-load of thirty- six waggons.}:
Where does the detritus of this immense daily
cube of broken stone go ? Into the respiratory
organs of the Parisians, their hair, clothes, houses ;
into the street gutters, thence to the drains, and
* ' Note sur les questions de viabilite, par M. Barabant, Ingenieur
en chef de la voie publique.' Chaix, 29 Rue Bergere, Paris.
t ' Note sur 1'entretien des voies publiques de Paris, par M.
Allard.' 1 1 Rue Cadet, Paris.
J ' Variations de la circulation dans les rues de Paris de 1872 a
1887, par M. Andre, Ingenieur en chef.' 17 Rue Cadet, Paris.
NATURAL ASPHALT. 71
thence again to the river Seine, to form therein
banks of silt and mud, which must be dredged
away or navigation would eventually be stopped.
No wonder that its suppression is desired. Its
cost is terrible ; the maintenance of a crowded
thoroughfare being half the cost of laying a new
asphalt road, including the concrete foundation.
Work done by Parishes and Municipalities without
the Intermediary of Contractors. It may be laid
down, that work done by the parish or municipality
is in the end always dearer than that done by
honourable contractors, although by the way of
stating the case, it may appear at first sight
cheaper. A parish has the inherent right to do
its own work, be its own contractor in fact, only it
certainly should not compete with the contractor
for public and private work.
In Paris the city lays its own wood, rolls its
own macadam, does its own paving repairs, though
not those for kerbs, does its street-cleaning, but
not the carting away of dung, detritus, rubbish, and
snow.
The parish or municipality pays no rates and
taxes, buys its raw material as cheap as the con-
tractor, uses its engineers and staff engaged for
control without extra payment, but it is hampered
by the system of accounts, has to pay its staff at
the depots, the rent of same, and interest on cost
of machinery plus repairs, whether work is going
on or not, and in case of failure has no one to hold
72 NATURAL ASPHALT.
responsible. The result is invariable work is slow,
labour dear and inefficient.
It is a well known fact in Paris that the con-
tractor gets three times more work out of his men
than a parish ; he has picked men and pays them
proportionately. Then supposing wood pavement
laid in Paris by the town staff to cost apparently
20 per cent, less than the contractor's price ; the
maintenance in any case will cost three and a half
times as much.
It is, however, probable that if instead of making
an estimate of the first cost, the actual figures were
taken rent, taxes, loss of time owing to lack of
materials (a frequent case), and a fair apportion-
ment of engineer's salary and that of the staff, the
cost would be 20 per cent, more.
It seems only fair that if a parish exacts poor-
rates and taxes from contractors, it should not
deprive them of the means of earning something.
Cost of Work in Paris. Paris being the town
in which the asphalt trade took its rise, the author
thinks it well to give the prices paid there, of
course premising that in other countries there is
additional carriage from the mines, and sometimes
custom duties, as in Amercia, Canada, and Austria,
on the manufactured material, but not the raw
rock.
Wage of an asphalter, per hour .. .. *]\d. or 15 cents,
help , 5fc/. n
NATURAL ASPHALT.
73
Portland cement concrete, 6 in. thick..
,, ,, 8 ..
Liquid asphalt mastic gritted, in. thick
pure, no grit, T 9 g ,,
,, when laid vertically ..
Natural compressed asphalt, 2 in. thick
For jobs up to 10 yards on surface ..
,, of I o to 20 yards on surface
Fillets extra, canvass or paper when spreading on wood, extra.
Grey granite kerbs, 12 inches by 12 inches, on concrete and
jointed complete, 13^. 2.d. or 3*64 dollars the running yard.
Per square yard.
$s. %d. or 88 cents.
4^. %d. i'i2 dollars
qs. 2d. ,, I *co ,,
4.5-. 2d. I'oo ,,
$s. 6d. ,, 1*32 ,,
gs. 2d. ,, 2*20 ,,
20 per cent, cubic.
10 ,,
Old gritted mastic, old pure mastic, old com-
pressed, are taken back by special arrangements.
Chicago World's Fair, 1893. Specimens of all
the natural substances described in foregoing pages
will be found in Class 12, Mines; and the author
will be happy to receive any correction or notice
in view of a second edition later
LONDON: PRINTED BY WILLIAM CLOWES AND SONS, LIMITED,
STAMFORD STKEET AND CHARING CROSS.
THIS BOOK IS DUE ON THE LAST DATE
STAMPED BELOW
AN INITIAL FINE OF 25 CENTS
WILL BE ASSESSED FOR FAILURE TO RETURN
THIS BOOK ON THE DATE DUE. THE PENALTY
WILL INCREASE TO SO CENTS ON THE FOURTH
DAY AND TO $1.OO ON THE SEVENTH DAY
OVERDUE.
.JAN 2b 1941
"50
LD 21-100m-7,'39(402s