Influence of asphalt rubber on the crushing of recycled aggregates used in dense HMA

This paper presents preliminary results of a research that investigates the feasibility of using aggregates recycled from civil construction and demolition wastes for manufacturing dense graded hot mixed asphalts (HMA) to be used in highways with low or medium traffic volume. Previous results showed that the tested material meets all Brazilian standard requirements for use in base layers, but it was prone to grain crushing, what is a major concern in the case of HMA. It is supposed that modified asphalt rubber binders might help to mitigate this potential problem. In order to check this hypothesis, several samples were prepared using binders with different amount or crumb rubber (0, 10 and 20%). The compaction energy was also investigated by varying the number of blows (35, 50, 75) during the Marshall compaction tests. The results were analyzed in terms of Marshall Degradation Index and show that the particle crushing is reduced with increasing amount of crumb rubber.