Enhancing the Rheological Performance of Crumb Rubber Modified Bitumen Through Oxidative Pre-Treatment

Crumb rubber (CR) can be used as a performance modifier on bitumen and has important environmental and performance advantages, but there are still problems with the consistency and storage stability of binders. This paper examines the effect of pre-treating the Crumb Rubber Modified Bitumen (CRMB) with a pre-treatment of potassium permanganate, which is an oxidizing agent, on increasing the physical and rheological properties of the pre-treatment. Bitumen (60/70 and 40/50) penetration grades were modified by two CR sizes (#30 and #40 mesh) at 10% and 15% concentrations in terms of binder mass. The obtained binders were tested with regard to physical characteristics (penetration, softening point, viscosity) and rheological performance with the help of a Dynamic Shear Rheometer (DSR). The findings indicate that the oxidative pre-treatment has a major effect on improving the interaction of rubber and bitumen. The CRMBs pre-treated had low penetration, higher softening points, and viscosity as opposed to their counterparts, which were untreated. DSR analysis showed that there is a significant enhancement of the high-temperature performance, where pre-treated samples exhibited a significant increase in the complex shear modulus, and a reduction in the phase angle, resulting in a significant increase in the rutting parameter. The combination of the 40/50 grade bitumen with 15% pre-treated #40 mesh crumb rubber resulted in the best rheological performance, thus showing that this pre-treatment technique could be used to form high-performance, rut-resistant binders that can be used in demanding pavement applications.