Effect of Crumb Rubber and Polymer Modifiers on Performance Related Properties of Asphalt Binders

Abstract

Crumb rubber modified bitumen (CRMB) has been generally used to improve the high temperature performance of asphalt mixtures in the past decades. Besides, the addition of a certain percentage of polymers into asphalt binders has been known to enhance their engineering characteristics. This study aims to investigate the rutting and fatigue cracking performance of CRMB, and polymer modified asphalt binders by means of Dynamic Shear Rheometer (DSR), Multiple Stress Creep Recovery (MSCR), and Bending Beam Rheometer (BBR). Different percentages of Crumb rubber (5, 10, 15, and 25%) obtained using the ambient grinding process were blended with a PG70-16 asphalt binder using the wet process. Small percentages ranging from 0.5 to 2% of polymers (LSBS, PPA, Elvaloy, and CBE) were added to a PG64-16 asphalt binder. It is demonstrated that mixing a specified percentage of crumb rubber from scrap tires, with the proposed optimized laboratory protocol, will result in an improved high-temperature performance reflecting higher rutting resistance complying with certain needs of regions with warm climates, especially the Mediterranean area. However, crumb rubber content should be restricted to 10% to limit the effect of the CR on the low-temperature performance grade. In the case of polymer modification, significant benefits were observed for rutting resistance of the resulting modified asphalt binders without jeopardizing fatigue cracking resistance criteria.