FROM LEFT TO RIGHT: KEROSENE,KEROSENE PLUS TAR, KEROSENE PLUSASPHALT CEMENT OR ASPHALT CUTBACK.BEADS FORMED BY ASPHALT EMULSION INKEROSENE.Figure 8-22.—Solubility test for asphalt, tar,and emulsion.Pour TestWhen you perform the volubility testand the bituminous material dissolves, anasphalt product–asphalt cement or asphaltcutback–is present. At room temperature(77 F) asphalt cements are solids, and asphaltcutbacks are fluids. With these facts in mind,you may run a second test, a pour test, todetermine whether a sample is an asphaltcement or an asphalt cutback.In the pour test, an attempt is made to pourthe material from a small container. Asphaltcements are solids and will not pour. Asphaltcutbacks are fluids at 77 F and will pour (fig. 8-23).A pour test is also used to identify the 12viscosity grades of tar. Viscosity grades of road tarare comparable to the viscosity grades of asphaltcutbacks and asphalt cement (table 8-5). RT-1, themost fluid, is similar in viscosity to the grade 30 ofthe rapid-curing, medium-curing, and slow-curingtypes of asphalt cutbacks. RT-8 is similar to grade800 asphalt cutback. RT-12 has the approximateconsistency of asphalt cement of 200-300penetration.Road tar grades 4, 5, and 7, which are identicalin appearance to road tar cutback grades 5 and 6 may bedistinguished through a smear test. Like asphaltASPHALT CEMENT ON LEFT.ASPHALT CUTBACK ON RIGHT.LEFT TO RIGHT: ASPHALT CUTBACKS GRADE30, 70, 250, 800, AND 3,000 THREE SECONDSAFTER TIPPING FULL JARS.THIRTEEN SECONDS AFTERTIPPING FULL JARS.143.179Figure 8-23.—Pour test for asphaltand cutbacks.cutbacks, road tar cutbacks cure rapidly since theyare thinned with highly volatile materials thatevaporate quickly and leave a sticky substance withina 10-minute period. On the other hand, because thefluid coal oil in road tars evaporates slowly, road tarswill remain at the same consistency at the end of anidentical period.8-25
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