Influence of Particle and Interaction Effects of Different Sizes of Crumb Rubber on Rheological Performance Parameters of Binders

Improvement in rheological performance of asphalt binder with the addition of crumb rubber (CR) depends on the interaction between CR and the asphalt binder matrix. Overall, the change in any rheological property of asphalt binder with the addition of CR can be attributed to two factors: the chemical interaction between CR and the asphalt binder matrix, termed the interaction effect (IE); and the filler nature of CR particles, termed the particle effect (PE). The present research was undertaken to quantify the relative contribution of IE and PE to various parameters responsible for changes in mixing and compaction temperature, high-temperature properties, and intermediate-temperature properties through various rheological approaches. Accordingly, viscosity, G*/Sin, multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) were tested using base binder modified with two CR particle sizes (ASTM# 30-40 and ASTM# 60-80) and keeping the amount of CR constant at 15% by base binder weight. In order to understand the contribution of IE and PE on different rheological parameters, three sets of samples for each CR size were prepared: (1)base binder, (2)undrained CR-modified binder, and (3)drained CR-modified binder. The effect of CR particle filler nature (through PE) was found to be significantly greater than the effect of chemical interaction (through IE) on viscosity, G*/Sin, recovery, and fatigue life. On the other hand, along with PE, the chemical interaction between CR and asphalt binder matrix (IE) was found to play a significant role in improving nonrecoverable creep compliance response. Additionally, based on comparative analysis of IE and PE in various performance-related parameters, the filler effect produced with the addition of 30-40CR particles was found to be more than the filler effect produced with the addition of 60-80CR particles. This indicates that increased CR particle size may cause changes in the filler nature of the CR-asphalt binder composite. Additionally, high-temperature storage stability was evaluated. Base binder with 60-80CR particles exhibited better stability than base binder with 30-40CR particles