The Effect of SBS Asphalt Modifiers on Hot Mix Asphalt (HMA) Mixture Cracking Resistance

This paper presents a laboratory investigation conducted to evaluate the effect ofboth radial and linear SBS modifiers on the cracking resistance of Hot Mix Asphalt(HMA) mixtures. Three types of asphalt mixtures composed by the same aggregate typeand gradation but different asphalt binders (one unmodified and the others obtained byadding linear and radial SBS polymers to the unmodified one) were produced in thelaboratory. The cracking performances of the mixtures were evaluated using a crackingmodel developed at the University of Florida called “HMA Fracture Mechanics Model”,based on the principles of visco-elastic fracture mechanics. The model requires onlyfive tensile asphalt mixture properties which are obtained using the Superpave IDT:resilient modulus, creep compliance power law parameters, tensile strength, fractureenergy and dissipated creep strain energy to failure.All the results presented show the benefit of SBS modifiers to mixture’s crackingresistance in terms of reduced rate of damage accumulation (m-value) and increasedtensile limits to failure (tensile strength, fracture energy and dissipated creep strainenergy to failure). No influence was observed in the elastic response but rather on thetime-dependent response. Finally, SBS linear polymers have shown to better improvecracking performances of HMA mixes than SBS radial ones.