Essential Role of Rubber Viscosity in Cuplump Modified Bitumen (CMB) for Pavement Application

Abstract Polymer modification of asphalt binders has become a more widely accepted strategy for alleviating pavement deterioration. Heavy vehicles, traffic volumes, and increasing tyre pressures have induced to consideration of polymer modification for asphalt pavement applications. The modified binder based on natural rubber (NR) produced from cuplump (CMB) has proven comparable to commercial modified bitumen. Results showed that NR modification improved the base bitumen’s conventional properties such as penetration, softening point, and temperature susceptibility. Optimizing the rheological behavior of rubber by controlling mixing times and conditions is essential for achieving the desired processing characteristics and final product properties. A key property considered in this study is viscosity. Raw natural rubber with varying Mooney viscosity values was altered using mixing techniques to characterize changes in rheological properties, Superpave rutting parameters, and conventional properties of the CMB binder. The study findings revealed that a low rubber viscosity led to a reduction in the complex shear modulus value, the rutting parameter, and the storage modulus (|G*|, |G*|/sin δ, and |G*|sin delta respectively) of the asphalt binder. The results revealed that a reduction in properties correlated with the structural changes due to the rubber mixing. Viscosity changed as mixing progressed, which was attributed to rubber’s intrinsic low tensile strength and rheological qualities. Rubber with low viscosity which results in a shorter polymer chain, reduces chain crystallization during stretching and size of crosslinked networks. This later influenced the deformation-induced crystallization and structural homogeneity of the crosslinked NR, which in turn affected the CMB properties