1. a.L Rasha jasim Mohamed Lec.7
Highway engineering
12/6/2017
a.L Rasha jasim Mohamed
Lec.7
Al. Rasha j. mohammed

2. Lec.7 Asphalts
Asphalts are the most common and most widely used bituminous materials The term “asphalt” refers to a black cementitious material which varies widely in consistency from solid to semisolid at normal temperatures Asphalts are found as natural deposits or are produced from petroleum crude.
Tars do not occur in nature and are obtained as condensates in the processing of coal, petroleum, oil-shale, wood or other organic materials.
12/6/2017
Al. Rasha j. mohammed

3. Sources of asphalt 1. Natural asphalt-
1. Natural asphalt
a. Native asphalt: The largest amounts of native asphalt have existed in Iraq several thousand years ago.
b. Rock asphalt: it is sandstone or limestone rocks filled with asphalt.
c. Petroleum asphalt: Obtained from refining (distillation) of petroleum
12/6/2017
Al. Rasha j. mohammed

4. TYPES OF PETROLEUM ASPHALTS
Following types of petroleum asphalts are used in pavement construction:
Asphalt cement
cutback asphalt
Emulsified asphalt
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Al. Rasha j. mohammed
Composite Camber

5. Emulsified asphalts are increasingly being used instead of cutback asphalts for the following reasons: Emulsions are relatively pollution free When cutback asphalts cure, the diluents which are high energy, high price products are wasted into atmosphere Emulsions are safe to use Lower application temperature: Emulsions can be applied at relatively without use any heat this lead to save the fuel costs. Emulsions can also be applied effectively to a wet pavement, whereas dry conditions are required for cutback asphalts
12/6/2017
Al. Rasha j. mohammed

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Al. Rasha j. mohammed