Description
This paper describes the interaction between crumb rubber and various penetration grade bitumens in terms of the absorption of the light fractions of the bitumen by the rubber and the chemical composition and rheological properties of the residual binder. Eight bitumens from two crude oil sources and four penetration grades ranging from 200 pen to 35 pen have been mixed with 2 mm to 8 mm sized crumb rubber at three rubber to binder ratios of 1:8, 1:6 and 1:4 by mass. The increased mass of the crumb rubber was used to determine the loss of volatiles and light fractions that have been absorbed from the different bitumens. The residual binders were then subjected to dynamic mechanical analysis using a dynamic shear rheometer to determine their rheological properties following the interaction with crumb rubber. The results show that the rate of adsorption is directly related to the penetration grade (viscosity) of the binders as well as to the chemical composition of the bitumen (crude source) but that the total amount of absorption is controlled by the nature of the crumb rubber. In terms of the rheological properties of the residual bitumen, all the binders showed an increase in stiffness (complex modulus) as well as elastic response with these changes being consistent for both crude sources and all four penetration grades.
