added to the emulsion up to proportions of 1:3 for usein slurry seal coats. Because emulsions contain water,they have certain disadvantages. During freezingweather the emulsions can freeze, and the componentscan separate. Also, emulsions are difficult to store forextended periods because they tend to “break” even inunopened drums. When emulsions are shipped, thewater in the mixture takes up valuable space, whichcould be used to transport hard-to-obtain materials.FIELD IDENTIFICATION OF BITUMENSA fairly accurate identification of bituminousmaterials is necessary to make decisions regarding typesand methods of construction, types and quantities ofequipment, and applicable safety regulations. Field testsmust be performed to identify a bituminous material asasphalt cement, asphalt cutback asphalt emulsion, roadtar, or road-tar cutback and to field-identify the grade.Field identification of bitumens is summarized infigure 13-29.Test for SolubilityThe first procedure in the identification of anunknown bituminous material is to determine whetherit is an asphalt, an emulsion, or a tar. Bituminousmaterials may be differentiated by a volubility test. Toperform the test, you simply dissolve an unknownsample (a few drops, if liquid, or enough to cover thehead of a nail, if solid) in any petroleum distillate.Kerosene, gasoline, diesel oil, or jet fuel is suitable forthis test. One or more of these distillates is usuallyavailable to the EA in the field Since asphalt is derivedfrom petroleum, it will dissolve in the petroleumdistillate. If the material is an emulsion, it can bedetected by the appearance of small black globules, orbeads, which fall to the bottom of the container. Roadtar will not dissolve. If the sample is an asphalt, thesample-distillate mix will be a dark, uniform liquid Ifit is a road tar, the sample will be a dark, stringy,undissolved mass in the distillate. You can make a checkby spotting a piece of paper or cloth with the mix. If nostain results, the material is a tar; however, if a brown toblack stain appears, then it is asphalt. The volubility testprovides a positive method of identification.Tests for Asphalt CementWhen the volubility test determines that thebituminous material is an asphalt you should thenperform a pour test to distinguish whether the asphaltmaterial is asphalt cement or asphalt cutback. In this testyou place a small sample of asphalt into a container andattempt to pour it at mom temperature (77°F). Sinceasphalt cement is a solid at room temperature, it will notpour. Even the highest penetration grade (200 to 300)will not pour or immediately deform. The thickestasphalt cutback, however, will start to pour in13 seconds at a temperature of 77°F.The various grades of asphalt cement aredistinguished by their hardness, as measured by a fieldpenetration test. For purposes of field identification,the consistency of asphalt cement maybe approximatedat room temperature as hard (penetration 40-85),medium (penetration 85- 150), and soft (penetration150-300. These limitations are flexible, as completeaccuracy is not essential. You can make anapproximation of the hardness while in the field byattempting to push a sharpened pencil or nail into theasphalt at 77°F with a firm pressure of approximately10 pounds. When the pencil point penetrates withdifficulty or breaks, the asphalt cement is hard. When itpenetrates slowly with little difficulty, the asphaltcement is medium. If the pencil penetrates easily, theasphalt cement is a high penetration or soft grade.Tests for Asphalt CutbacksIn addition to distinguishing asphalt cement fromasphalt cutback as discussed above, the pour test willidentify the viscosity grade of the cutback at a roomtemperature of 77°F. After the pour test, the approximateviscosity grade of the cutback is known, but the actualtype (RC, MC, SC) is not. Asphalt cement is “cut back”with a petroleum distillate to make it more fluid. If thematerial does not pour, it is an asphalt cement. If it pours,it is a cutback or emulsion. It has been found that thecutbacks of a given viscosity grade will pour like thefollowing substances:30-70-250-800-30 0 0 -A smearWaterLight syrupsyrupMolassesBarely deformtest is used to distinguish an RC cutbackfrom an MC or SC cutback. The test is based on the factthat RCs are cut back with a highly volatile material(naphtha or gasoline) that evaporates rapidly. Toperform the test, you simply apply a thin smear of thematerial on a nonabsorbent surface, such as a piece of13-41
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