Abstract:
Premature pavement failures due to uncontrolled axle loads and high ambient temperature are observed throughout Pakistan leading to high preservation lifecycle costs. Crumb Rubber Modified Bitumen (CRMB) in asphalt mixtures improves the properties of binder by reducing the binder’s inherent temperature susceptibility. This research investigates the effect of various proportions of crumb rubber on performance based properties of binder and Hot Mix Asphalt (HMA). The experimental design included the use of aggregate source of Margalla quarry, two penetration grades bitumen of 60/70 and 80/100, five crumb rubber proportions (0%, 4%, 6%, 8% and 12%) and National Highway Authority’s commonly practiced wearing course gradation with nominal maximum aggregate size of 19 mm. Laboratory tests characterized unmodified (controlled with 0% rubber) and various proportions of CRMB samples based on the conventional consistency and Superpave performance based tests. Hot asphalt mixtures including crumb-rubber-modified bitumen were then evaluated by determining stiffness moduli (using Indirect Tensile Strength and Resilient Modulus test) and the permanent deformation potential (using Hamburg Wheel Tracker test). The research findings indicated that, an increase in the rubber content in the modified mixture increases the viscous characteristics and improves the aging resistance of the modified binder. Two-level factorial design of experiment was conducted to analyze the performance of mixtures and it was revealed that mixtures with 8% CRMB (with 60/70 grade) and 12% CRMB (with 80/100 grade) show maximum resilient modulus and least rut susceptibility. Thus, the research findings advocate that mixtures prepared with CRMB lead to better rutting resistance, and encourage the use of crumb rubber in asphalt modification through sustainable technology in an environment friendly way.
