Evaluating Factors Affecting Aggregate-Bitumen Interfacial Strength Using Binder Bond-Strength Test

Abstract

The present study evaluated the effects of six different bitumen film thicknesses (0, 0.2, 0.4, 0.6, 0.8, and 1 mm); four polishing levels of aggregate [220, 400, 600, and 800 Silicon Carbide (SiC)]; three moisture conditioning temperatures (25°C, 40°C, and 60°C); and three different aging levels of bitumen (143°C, 163°C, and 173°C) on interfacial strength of basaltic-unmodified bitumen system using binder bond-strength (BBS) test. Further, two different basaltic aggregates were procured, and their interfacial bond with three different types of bitumen, namely, unmodified (VG30), polymer-modified (PMB40), and crumb rubber–modified (CRMB60) was evaluated. The results showed that basaltic aggregate with higher porosity (and thus higher rate of moisture absorption) showed lower bond strength, although the polishing level of both aggregates was kept at 220 SiC. Further, PMB40 had higher bond strength followed by VG30 and CRMB60, depicting the influence of crumb rubber particles on interfacial bonding behavior of CRMB60. The study showed that 220 SiC polished aggregates having 0.8-mm bitumen film thickness and conditioned at 40°C can provide appropriate results on aggregate-bitumen bond strength using the BBS test, which supports the recommendations provided in AASHTO T 361. Thus, the authors believe that the BBS test may be beneficial in evaluating aggregate-bitumen bond strength in the field.