Asphalt

“ The exposed asphalt, whether this exposure is made by printing or whether a drawing is first made and then exposed to the light, adheres more firmly to the stone or zinc plate than if it was not exposed. An asphalt drawing prepared in the dark and inked up does not adhere to the stone, and this may be explained in that the grease cannot act through the asphalt film. ”

“ But it should also be said that they share the diversity of character of petroleums, and the term asphalt represents a group of substances of which the physical characters and chemical composition differ greatly in virtue of their derivation, and also differ from changes which they are constantly undergoing. Thus at the Pitch Lake in Trinidad, the central portion is a tarry petroleum, near the sides a plastic asphalt, and finally that which is of almost rock-like solidity. ”

“ The engineers cried "Eureka!" and well they might, for experience in Paris shows that—1. The asphalt costs, in the first instance, one-third less than stone pavement; and 2. That the annual cost of maintenance is three-quarters less than that of a macadamized road.
The process of preparing the asphalt pavement is thus described by M. Léon Malo: The asphalt-stone is brought direct from the quarries, and broken up into small pieces, about the size of those used for macadamized roads; it is then heated over a stove in a drum-shaped iron vessel with feet, till it crumbles into powder. ”

“ Lunge found, from many distillations, that tar from the midland counties yields about 55 per cent, of hard pitch.
Hard pitch is used chiefly for making the following. (1) Asphalt.—The pitch is fused up—perhaps in the still which produced it—with the requisite proportion of creosote and anthracene oil, previously freed from their valuable components. Such asphalt is used for street-paving, i.e., filling up the spaces between the paving-stones, and, in admixture with sand and generally more or less of natural asphalt, for the making of footpaths and floorings generally. ”

“ Asphalt is produced artificially in making coal-gas. During the process much tarry matter is evolved and collected in retorts. If this be distilled, naphtha and other volatile matters escape, and asphalt is left behind. It is sometimes called Jew's Pitch.
Asphalte (or Asphalt) Rock, a limestone impregnated with bitumen, found in large quantities in various localities in Europe, as in the Val de Travers, Neufchâtel, Switzerland; in the department of Ain in France; in Alsace, Hanover, Holstein, Sicily, &c. ”

“ Refined Asphalt.—Refined asphalt produced from native crude asphalt shall be free from water and shall not contain an injurious quantity of light oils or foreign matter. It shall not contain more than four per cent. (4%) of organic matter nor more than thirty-six per cent. (36%) of inorganic matter other than bitumen, and not more than eighteen per cent. (18%) of fixed carbon, and not less than fifty-five per cent. (55%) of bitumen soluble in cold carbon di-sulphide. Of the bitumen soluble in carbon di-sulphide not less than sixty-three per cent. ”

“ In common with other forms of bitumen, asphalt is very widely distributed geographically and occurs in greater or less quantity in rocks of all ages. There is some divergence in the views expressed as to the precise manner of its production, but it may certainly be said that the principal asphalt deposits are merely the result of the evaporation and oxidation of liquid petroleum which has escaped from outcropping strata. ”

“ The practice of opening the street to travel for a period after the blocks are relaid and before the asphalt surface is applied, helps, under favorable conditions, to consolidate the foundation, but does not remove the objections to it. If heavy rains intervene, the sub-foundation becomes saturated with water, and its resistance so reduced that the stone blocks settle out of shape, particularly in soft spots, and they are usually hastily raised and reset just before the asphalt surface is applied. The result is an insecure foundation fatal to the durability and usefulness of the pavement. ”

“ Asphalts containing less than the former proportion have not sufficient coherence for street pavements, and those containing more than the latter proportion soften from heat in the summer. Asphalt is employed either as a mastic or compressed. The mastic is previously prepared in cakes and is melted for use in caldrons with a small quantity of bitumen, and for a street pavement is thoroughly mixed with sand or grit. It is spread in one thickness on a concre te foundation, covered with sand, and beaten to an even surface. ”

“ There is still a wide difference of opinion as to the advisability of laying the asphalt surface directly against the rail, many engineers preferring to set one or more courses of paving brick, or stone paving blocks between the rail and the edge of the asphalt. The writer’s experience is to the effect that, if the work is properly done, the first-named form of construction is preferable. If the asphalt be laid against a rail so cold that the asphalt material in contact with or near the rail is chilled before it can be compressed, the work will necessarily be unsatisfactory. ”

“ All kinds of asphalt have a pungent and peculiar smell, melt at a low temperature, are very combustible, and while dissolving in turpentine, and more readily in coal tar naphtha, are insoluble in water and in alcohol. Very little asphalt is now used as a pigment, but it continues to find a limited application in varnish making, notwithstanding the tendency of varnishes containing it to suffer from minute cracks with the lapse of time. ”

“ The practice of laying pavement surfaces, particularly those of asphalt, upon a foundation of old stone blocks, carelessly reset, with the joints unfilled with mortar, is all wrong and should never be resorted to. The integrity and durability of an asphalt pavement depends largely upon the strength and rigidity of its foundation; to lay an asphalt surface, however good, over such an old block foundation, is an inexcusable waste of money. ”

“ There are several uses to which asphalt may be applied, the most important being the one already so often referred to, namely, as paving material. In Paris about thirty-three miles of street are covered with asphalt pavement, more than three fourths of it being the so-called "compressed asphalt," while the remainder is made of cast or mastic asphalt. The use of asphalt pavements for roadways began in Paris in 1854, since which time their use has been steadily increasing until the present time. In London there are about nine miles of asphalted streets. ”

“ As soon as the whole is thoroughly incorporated, the proper consistence attained, and the vapours of the volatile oils and water come off in very minute quantities, the asphalt is run off into the moulds before described, and when sufficiently set may be removed, and is ready for use. ”

“ The surface, after the wear of a summer, during the heat of which it softens slightly, becomes nearly coherent and as continuous as sheet asphalt. On grades, the slight irregularities due to jointing offer a better foothold to the hoofs of horses than sheet asphalt and in this respect the asphalt blocks are the best. ”

“ Sheet Asphalt Roads and Streets, considering their cost, durability, smoothness, ease of riding, low tractive resistance, and general acceptability, are among the most [266] popular roads. What has been said of sheet asphalt will apply to asphaltic concrete of the Topeka specification and bitulithic types. The road is better for use. The asphalt and sand surface has the habit of swelling and cracking when not used. The proportioning and laying of a sheet asphalt surface is a particular job and requires a person of technical knowledge and experience to do it properly. ”

“ For a perfect, quick-drying asphalt varnish the purest asphalt must be used, such as Syrian, or the best Trinidad. Trinidad seconds, though better than some other asphalts, yield an inferior varnish, owing to the presence of impurities.
Of artificial asphalt, the best for this purpose is the sort known as “mineral caoutchouc,” which is especially suitable for the manufacture of elastic dressings for leather and other flexible substances. For wood and metal it is less desirable, as it never becomes as hard as natural asphalt. ”

“ Asphalt first appears in your specifications as under the item of 'damp course.' It is advisable to lay throughout the walls on the grade of the cellar-floor half an inch of asphalt, with a lap of about two inches on the inside, so allowing a connection with the asphalt finish of the cellar-floor and hermetically sealing the house from damp, noxious gases, and vermin. ”

“ Asphalt surface must not be laid when rain or snow is falling, or so long as the street surfaces are wet. Surface mixture raked out and caught in a shower before it is well enough rolled to exclude water must be taken up and discarded.
Unless unavoidable, neither binder nor surface should be laid when the street surface or the air is below 40° F. As a rule, the lower the temperature the of air the greater is the care necessary to properly lay asphalt pavement. ”

“ In constructing a roadway of this kind, a bed of mortar is first laid down, which is covered by a strong layer of asphalt; it is in this layer that the iron cakes, which are about 1.6 inch thick, are set. These cakes, it appears, preserve the homogeneity of the bitumen and prevent its depression, and render the asphalt less slippery for horses. This pavement will cost more than the compressed asphalt, but it is estimated that it will save 50 per cent. ”

“ For this purpose the asphalt, coarsely powdered, is digested for 1 to 2 days with benzine in well-closed vessels, at a moderately warm spot. Petroleum asphalt results when the distillation of petroleum continued until a glossy, firm, pulverizable mass of conchoidal fracture and resembling colophony in consistency remains. The benzine dissolves from this asphalt only a yellowish-brown dyestuff, which deeply enters the wood and protects it from the action of the weather, worms, dry rot, etc. The paint is not opaque, hence the wood retains its natural fiber. ”

“ In American cities asphalt has been adopted in a totally different form. All asphalt pavements are composed of a very large proportion, perhaps five parts in six, of a hard non-bituminous material. In America itris found cheaper to get the purer bitumen of-the island of Trinidad, and to procure in the localities the bulky material required for'~admixture-a coarse angular sand with-a little pure carbonate of lime. ”

“ Asphalt, whether a natural product or artificially obtained, as, for example, in some chemical manufactures, is a most useful material if properly employed in connexion with reservoir dams. Under sudden impact it is brittle, and has a conchoidal fracture like glass; but under continued pressure it has the properties of a viscous fluid. The rate of flow is largely dependent upon the proportion of bitumen it contains, and is of course retarded by mixing it with sand and stone to form what is commonly called asphalt concrete. ”

“ Asphalt cannot be very readily used for this purpose unless it is an asphalt oil with but little bitumen paste. A paving asphalt, for example, even applied hot, does not adhere to the masonry, but slides down the walls as fast as it is applied. A successful method, however, of using such asphalt is to build the cellar wall in two parts, separated about half an inch, and filling in the intervening space with liquid asphalt. In this way, the asphalt is held in position, and is an absolute prevention of dampness. ”

“ The exposed asphalt combines so intimately with the stone that strengthening with a greasy ink is quite unnecessary, is indeed absolutely purposeless, as the ink can neither penetrate the hard asphalt film nor combine with it. The film of asphalt alone is so resistant to every etching solution that it is for this reason absolutely useless to strengthen it. ”

“ A poor asphalt pavement offers one of the best opportunities for the study of the formation of various kinds of cracks and fissures. On the edge of a sloping sidewalk one may see the cracks due to a sliding, or lateral displacement of the surface; the effects of subsidence show a number of cracks around the area of depression; the growth of a tree crowding the asphalt shows the effect of lateral thrust, and an enlargement of a root below, or the effects of frost show cracks due to elevation. ”

“ Taking a negro boy as a guide, Stuart started [Pg 192] for the famous deposit of asphalt, about one mile inland. The countryside leading thither was not absolutely barren, but it was scrawny and dismal. A coarse sand alternated with chunks of black asphalt. A few trees managed to find a foothold here and there, and there was sparse vegetation in patches. ”

“ Asper ́ula, the woodruff genus of plants.
Asphalt, or Asphal ́tum, the most common variety of bitumen; also called mineral pitch. Asphalt is a compact, glossy, brittle, black or brown mineral, which breaks with a polished fracture, melts easily with a strong pitchy odour when heated, and when pure burns without leaving any ashes. It is found in the earth in many parts of Asia, Europe, and America, and in a soft or liquid state on the surface of the [280] Dead Sea, which, from this circumstance, was called Asphaltītes. ”

“ To prevent this, all places so situated that the water cannot of its own accord drain away are tilled with asphalt-concrete—that is, a mixture of asphalt, pitch, tar, and coarse gravel—to such an extent that all water will run off by gravity. Where this is not possible, or would lead to too much weight being put on, holes are drilled, and the asphalt so laid that the water is drained to them and away through them. ”