Performance and Acceptability Criteria for Crumb Rubber Modified Binders with same Performance Graded (PG) Rating



This study investigated the acceptability criteria for the permanent deformation performance of asphalt binders modified with crumb rubber. The objective of this study was to evaluate if different asphalt binders when modified with crumb rubber to achieve similar PG rating would also show similar high temperature performance for the corresponding modified mixtures.
Based on the coefficient of variation and standard deviation values established for the RSST-CH test, it was observed that for the unmodified and crumb rubber modified mixes examined at 40oC test temperature, the high temperature performance characteristic of binder was found to govern the rutting performance characteristics of the mix. Mix containing binder with higher high temperature PG rating showed higher resistance to permanent deformation than the mix containing binder with lower PG rating. Mixes containing binders with same high temperature PG rating (AC20, AC10+7%CR), showed similar rutting characteristics.
At 60oC test temperature, the influence of binder on mix rutting performance characteristics was significantly reduced. It was concluded that 60oC temperature was too severe (although the PG high temperature rating was 64°C) for RSST-CH test to differentiate between mixes containing binders one or two PG grade apart.

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