Behaviour of asphalt rubber mixtures with different crumb rubber and asphalt binder sources

Abstract

This study evaluates the performance in laboratory of gap graded mixture prepared with different crumb rubber types and different conventional grade asphalt binders. The asphalt rubbers were prepared via wet process (continuous blend) and their properties were measured through the current tests: (i) penetration;(ii) softening point: (iii) resilience; (iv) apparent viscosity using a Brookfield viscometer. The rheological properties for conventional asphalts were measured too, in order to evaluate their mechanical behaviour. The gradation used for the asphalt rubber mixtures was a gap graded (ARHM-GG) specified by Caltrans. ARHM-GG is a surface course with an aggregate gradation that has a gap in the continuous grading. Using this gradation, from the mix combination of rubber types and conventional asphalts, six asphalt rubbers were made from which resulted six asphalt rubber mixtures. All mixture selected were evaluated through complex modulus al1dfatigue test. The results showed that the mixture prepared with crumb rubber from cryogenic process with asphalt binder with higher grade performed better than the other mixtures.