City roads and pavements suited to cities of moderate size. . The processof failure may then be as follows: The material composing the sheet of asphalt expandsslightly with the suns heat, as all other substances do;but unlike most other substances, it does not of itselfat once return to its original thickness when the heat 124 CAUSES OF FAILURE OF is lost, because the asplialt becomes rigid as it cools,and unless compressed by force, tends to remain in itsexpanded form. In the center of the roadway, wheremost of the wheels pass, the asphalt is at once re-com-pressed, but at t
City roads and pavements suited to cities of moderate size. . The processof failure may then be as follows: The material composing the sheet of asphalt expandsslightly with the suns heat, as all other substances do;but unlike most other substances, it does not of itselfat once return to its original thickness when the heat 124 CAUSES OF FAILURE OF is lost, because the asplialt becomes rigid as it cools,and unless compressed by force, tends to remain in itsexpanded form. In the center of the roadway, wheremost of the wheels pass, the asphalt is at once re-com-pressed, but at the sides this is not done so promptly,with the result that there is a tendency to becomesomewhat porous or spongy where there is little at last the asphalt has thus actually becomeporous, water can permeate it, and this soakage ofwater is helped by the fact that the surface-drainage istoward the sides, where the material is most likely toabsorb some of it. Having thus absorbed ever so littlemoisture, of course both heat and frost have increased. JEFFERSON AVENUE, HROOKEYN, effects of gas leaks on sheet-asphalt pavement. CITY ROADS AND PAVEMENTS. effects upon the material, and ultimately it shows signsof disintegration. Seventh.—When a failure of asphalt is so completeas to include several of these features, it will usuallybe found that the pavement was built by some localpaving company, wdthout previous experience, whosebid should not have been considered and whose workand guarantee proved to be equally worthless. EightJi.—Disintegration of surface may also resultfrom defects in the mixture of asphaltum and flux orfrom the laying of the pavement during freezingweather; disintegration is frequently caused, espe-cially in Brooklyn, New^ York and Kansas City, by theescape of illuminating gas from leaky mains. Thehydrocarbons which are now used in these cities toenrich and cheapen illuminating gas, are solvents ofasphaltum; leaks of this destructi
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectstreets, bookyear1902
