Improving asphalt concrete resistance to rapid freeze–thaw effect using HIPS polymer

Two methods of high-impact polystyrene (HIPS) polymer addition to asphalt concrete (AC) mixtures were used to evaluate the effect of freeze–thaw (FT) cycles on the performance of unmodified AC and AC modified by using supplementary and additional HIPS polymer as asphalt aggregates. Various polymer contents were used to modify AC in both methods – namely, 0 (control), 5, 10, 15 and 20%. Marshall stability, flow, bulk density and indirect tensile strength (ITS) tests were performed on control and modified samples. A non-destructive test was performed by using the ultrasonic pulse velocity method. In the first method, replacing the mineral filler in AC with 10% HIPS polymer increased the density by 1%, the stability by 113%, the retained stability by 52% and the ITS by 56% compared with those of the control specimen. The results also show a 14% reduction in the damage caused by 8 weeks of FT cycles for modified AC compared with that of unmodified AC. However, modifying AC by using the second method did not provide promising results. The velocity within the specimen dropped by 20.9% at 10% HIPS addition before the FT effect compared with that of the control. The results of the first method revealed the feasibility of improving AC by using HIPS polymer to resist effective FT cycles.