Mechanical Evolution of Rubber Swelling in Bitumen

Description

Mechanical Evolution of Rubber Swelling in Bitumen

Haopeng Wang, Gordon Airey, Zhen Leng

ABSTRACT. Rubber swelling in bitumen, which is a diffusion-induced volume expansion process, plays a dominant role in the design of crumb rubber modified bitumen (CRMB) binders and their properties development. This study aims to investigate the kinetics of bitumen diffusion into cylindrical rubber samples cut from scrap truck tires, the evolution of swelling degree and mechanical properties of swollen rubber samples with time. The swelling index, defined as the mass increase of rubber samples, increases with interaction time along a logarithmic trendline. Mechanical tests by dynamic shear rheometer (DSR) reveal that swollen rubber becomes softer comparing to the dry rubber and exhibits obvious viscoelastic behaviors. With the increase of interaction time, the softening and viscous effect are more significant. The equilibrium modulus derived from the generalized Maxwell model for swollen rubber has a good correlation with the swelling index, which follows a Power law relationship. Understanding the mechanical evolution of swollen rubber will be beneficial to achieving desired CRMB mechanical properties by controlling the interaction between bitumen and rubber.

KEYWORDS: rubber, bitumen, interaction, swelling, mechanical property, micromechanics.