Multi-parametric characterization of mode I fracture toughness of asphalt concrete: Influence of void and RA contents, binder and aggregate types

This study aims to evaluate the fracture toughness (KIc) in mode I cracking using semi-circular bending test (SCB). Experiment has been performed to investigate the influence of bitumen grade (using P15/25 and P50/70 bitumens), reclaimed asphalt (RA) content (using 0%, 20% and 40% RA contents) and temperature (using −20 °C, −5 °C, 10 °C test temperatures), through ANOVA. Additional investigations have been performed: (i) to evaluate the effect of the use of polymer modified bitumen (PMB), (ii) to evaluate the effect compactness using 5% and 8% air void contents, (iii) to evaluate the effect of aggregate type using siliceous-limestone and porphyry aggregates. The results show an important decrease in KIc when temperature increases from −5 °C to 10 °C and a slight decrease between −20 °C and −5 °C. The results also show that increasing RA content increases slightly the KIc. It was found from the ANOVA that the influent parameters can be ranked as follows: temperature, RA content and binder grade. The investigations show that PMB increases the KIc value than pure bitumens. Porphyry aggregates increase the KIc by about 16% than silica-limestone aggregates at low temperatures between −20 °C and −5 °C. However, this ranking is slightly inverted at 10 °C. In addition, KIc decreases by about 12% at 10 °C with an increase in air voids (by 5% to 8%). Void content effect is more significant at −5 °C and 10 °C, and negligible at −20 °C. Keywords: Fracture toughness, SCB, Bituminous mixture, Reclaimed asphal