Normally 60/70 penetration grade, and provides cohesion to the mixture and increases its stability.
The mix design is done by the Marshall test, in which a specimen compacted at standard conditions is loaded (Figure 7). The load at failure is noted as the stability value. By trials involving the use of various percentages of binder, the optimum binder is selected which gives the maximum stability, maximum density, 4 per cent voids and 80 per cent of voids filled with bitumen. The binder content varies from 5-7 per cent. The stability values specified are 9.0 kN (900 Kg) for highway pavements.
Figure : Marshall Test Apparatus
The mixing is done in a hot-mix plant and laying is done by pavers.