Influences of Particle Size and Content on Deformation Resistance of Crumb Rubber Modified Asphalt using Dry Process Mix
Crumb Rubber Modified (CRM) is one of techniques for improving asphalt mixture performance. There are two alternatives for applying crumb rubber (CR) to Hot Mix Asphalt (HMA), “Wet” and “Dry”. In the wet process, CR is added into hot asphalt cement in a factory, then CR-asphalt cement infusion is transported to a HMA plant for blending with hot aggregates. In the Dry process, CR is blended with hot aggregates and asphalt cement directly in a HMA plant. Although the dry process is considered less efficient due to lower infusion with asphalt cement, it offers some advantages that CR content can be independently controlled and higher amount of CR can be added into the HMA. This study focuses on dry process that uses CR modification by replacing some aggregate particles in mixture. HMA is blended with CR in 3 different sizes: 1.18 - 2.36 mm, 0.6 - 1.18 mm and smaller than 0.6 mm. The x-sized CR is added to the mixture in substitution of the same x-sized aggregate particles at the amount of 1% and 2% by the whole aggregate volume in the mixture. The mixtures’ performance in deformation resistance is represented by Wheel Tracking Slope (WTS). The results of Wheel Tracking tests on the specimens are enlightening. The mixture with CR particles smaller than 0.6mm shows excellent performance on deformation resistance, indicated by significantly lower WTS than others. Secondly, mixtures with higher amounts of CR have better performance than those with lower amounts. The mixture with 2% CR with smaller than 0.6 mm provides optimal performance at 2.1 times better than conventional HMA.