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EMULSIONS
Figure 13-29.-Field identification of unknown bituminous materials. - 14071_308

Engineering Aid 2 - Intermediate Structural engineering guide book
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Table  13-7.—Typical  Uses  of  Bituminous  Materials bituminous coal is destructively distilled, coke and gas are formed, and tar, ammonia, light oils, sulfur, and phenol may be recovered. Coke-oven tar is produced in the greatest amount, and its chemical, physical, and adhesive  characteristics  make  it  most  suitable  for road-tar purposes. Water-gas tar is obtained in the manufacture  of  carbureted  (mixed  with  hydrocarbons) water gas. The nature of the carbureting oil largely determines  the  character  of  the  water-gas  tar  produced. This  tar  may  vary  widely  in  specific  gravities, viscosities, and other physical and chemical properties. Road tars are manufactured in 12 grades of viscosity (figs. 13-27 and 13-28). There are also some special grades  for  use  in  rubberized-tar  binders.  Grades  1 through 7 are liquid at room temperature, and grades 8 through 12 are semisolid or solid. The difference occurs because of different amounts of the liquid coal distillates in the tar; the more distillate, the more liquid (or less solid) the tar. The  road-tar cutbacks  (RTCBs)  are  the products  of  cutting  back  the  heavier  or  harder  grades with  coal  tar  distillates.  Road-tar  cutbacks  are manufactured in two viscosity grades (5 and 6) only. Tar,  which  is  insoluble  in  petroleum  distillates,  is sometimes  mixed  with  oil-resistant,  unvulcanized rubber to form a rubberized-tar binder material. CHARACTERISTICS  AND USES OF BITUMENS Selection  of  a  particular  bituminous  material depends upon the type of pavement, climatic conditions, seasonal  factors,  and  availability  of  equipment.  In general, soft penetration grades of asphalt cement are preferred for use in cold climates, medium grades in moderate climates, and hard grades in warm climates. Heavier grades of asphalt cutbacks and tars are normally used  in  warm  weather  and  lighter  grades  in  cold  weather. Tables  13-6  and  13-7  list  the  bituminous  materials, sources, curing, temperatures, and grades associated with  bituminous  operations. 13-39 .    .    .







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