The Effect of Polymer Modification on Hot Mix Asphalt (HMA) Fracture at Tensile Loading Conditions

A laboratory investigation was conducted to evaluate the effect of both cross-linked and linear Styrene-Butadiene-Styrene (SBS) modifiers on the cracking resistance of Hot Mix Asphalt (HMA) mixtures. Five types of asphalt mixtures composed by the same aggregate gradation but different asphalt binders were produced in the laboratory. The cracking performances of the mixtures were evaluated using a visco-elastic fracture mechanics-based model entitled “HMA Fracture Mechanics”. Crack localization and crack growth were investigated performing the Indirect Tensile Test (IDT) and the Semi-Circular Bending (SCB) test. A Digital Image Correlation (DIC) System capable of providing full field strain maps was applied. The results show the benefit of SBS modifiers to mixture’s cracking resistance in terms of reduced rate of damage accumulation and increased tensile limits to failure. No influence was observed in the elastic response but rather on the time-dependent response. Finally, significant damage and first fracture have shown to be strongly more localized in modified specimens than in the unmodified one.