Review and comparison of methods to assess the storage stability of terminal blend rubberized asphalt binders

Abstract

Terminal Blend (TB) rubberized asphalt binders exhibit excellent storage stability compared with conventional rubberized asphalt binders, but there is still a phase separation in TB rubberized asphalt binders. Previous studies have developed different assessment methods to examine the phase separation of polymer modified asphalt binders, but it is still unclear whether these methods are suitable for TB rubberized asphalt binders. In this study, current commonly used assessment methods of storage stability were examined with TB rubberized asphalt binders that were prepared with two types of crumb rubber in various particle sizes and contents. After storage stability tests, non-dissolved crumb rubber particles were extracted from TB rubberized asphalt binders. The relationships between non-dissolved crumb rubber particles and different assessment methods were then examined with the help of Spearman’s rank correlation coefficient. It was found that crumb rubber content has a positive effect on the storage stability of TB rubberized asphalt binders and the effect of particle size on the storage stability is highly dependent on rubber source. Additionally, softening point difference, separation index, separation and degradation ratios at intermediate temperatures are not reliable indicators for assessing the storage stability of TB rubberized asphalt binders. Conversely, separation and degradation ratios at high temperatures and low frequencies are better indexes to characterize the storage stability compared with the other indexes, followed by percentage of separation.