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Table 13-5.-Asphalt Cutback Composition (Expressed in Percent of Total Volume)
CHARACTERISTICS  AND USES OF BITUMENS - 14071_307

Engineering Aid 2 - Intermediate Structural engineering guide book
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Table 13-6.-Characteristics of Bituminous Materials cutback  asphalt,  but  differs  in  many  specific  properties. It is used as a soil binder and dust palliative. EMULSIONS.–  Emulsification  is  the  third  process in  which  asphalt  is  liquified.  In  the  emulsification process,  hot  asphalt  cement  is  mechanically  separated into minute globules and is dispersed in water that is treated with a small quantity of an emulsifying agent, such as soap, colloidal clay, or one of numerous other organic agents. The rate at which the asphalt globules separate from the water is called the breaking  or setting time.  This  rate  is  generally  dependent  upon  the emulsifier  used  and  the  proportion  of  water  to  asphalt. Based in the breaking time, emulsions are described as  rapid  setting  (RS),  medium  setting  (MS),  and  slow setting  (SS).  They  are  also  described  by  viscosity numbers  (fig.  13-28). Emulsions  are  also  grouped  according  to  their ability to mix with damp aggregate. The RS emulsion breaks so fast that it cannot be mixed; therefore, it is called a nonmixing emulsion. The MS and SS emulsions break slowly enough to permit good mixing; that is, each particle of the aggregate is uniformly coated. Emulsions may be satisfactorily used as a tack coat for bituminous pavements. ROAD   TARS.—   Tars  are  products  of  the distillation of coal. No natural sources of tar exist.  Coal tar is a general term applied to all varieties of tar obtained from coal. It is produced by one of several methods, depending on the desired end product. When . 13-38 ---------- L–  .







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