Table 8-5.-Viscosity Grades at Room Temperatureviscosity grades of asphalt cutbacks andasphalt cements by means of table 8-5.Use of TarsTars are suitable for use on areaswhere asphalt is unsuitable. A goodexample is an airfield where petroleumdistillates are likely to be spilled. Tarsdo not strip easily from aggregate in thepresence of water and is preferred as aprime coat. Tars penetrate more deeplyinto the base course than will asphalt ofthe same viscosity and curing rate.Cold-tar mixes are used for road mixand patching. Hot-tar mixes are used forplant mix, surface treatment, crackfillers, and similar uses. Since tarsbecome soft at high temperatures andbrittle at low temperatures, the heaviergrades are preferred for use in warmweather and the lighter grades in coolweather.Road tar cutbacks are used forpatching mixes; however, an open flamemust NOT be used near storage tanks anddrums of road tar cutbacks because theyare flammable.FIELD IDENTIFICATION OFBITUMINOUS MATERIALSIdentifying bituminous materials canbe a problem. Stockpiled bituminousmaterials that are unmarked or improperlymarked can cause unnecessary delays inconstruction operations. Fairly accurateidentification is necessary to decide onthe type of construction that thematerials can be used for, the method ofconstruction to be used, the type andquantity of equipment needed, and theapplicable safety regulations to beobserved. Some of the tests used in thefield to identify bituminous materials asasphalt cement, asphalt cutback, asphaltemulsion, road tar, or road tar cutbackare as follows:SolubilityPourSmearHeat-OdorPenetrationStone coating8-23
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