International Journal of Engineering and Technology

Along with other polymers, Crumb Rubber (CR) obtained from scrap tyres has also resulted in enhanced performance of the virgin binder to meet the increased traffic density. However, the nature of reaction between the primary components has been reported to be different compared to the other polymer modification resulting in an heterogeneous blend of primary components. Despite the enhanced physical and performance characteristics of CRMB such as improved rutting and fatigue resistance, the product is still not widely accepted; the reason being inadequate and inconsistent observations from different researchers and agencies around the world. This has also led to a gap, where industry and the research community are still trying to understand and control the reaction mechanism between CR and bitumen to obtain consistent results. To understand the reaction mechanism, a total of 27 CRMB blends with different material combinations were prepared in the laboratory. To examine the changes, samples were collected after different intervals of blending and further subjected to laboratory observations for volumetric changes. The collected samples were then put through the separation processes to recover binder residue and swollen CR for further laboratory analysis. Results demonstrated that the aging of bitumen make it harder due to oxidation. Equally CRMB production also contributes to the hardening of base bitumen due to the diffusion of lighter fractions of bitumen into the CR particles. This resulted in changes in volumetric of the blend, bitumen and CR. The main factors responsible for these changes were; proportion of the primary components, CR size, base bitumen grade and volatilisation during production. As a result, a maximum increase of up to 0.42% and 3.9% was observed in the densities of CRMB and bitumen residue respectively. However, a significant reduction of 19% in the densities of the CR phase was observed.