Evaluation of fracture resistance of asphalt mixes involving steel slag and RAP: Susceptibility to aging level and freeze and thaw cycles

This paper investigated the effects of concurrent recycling of fine reclaimed asphalt pavement (RAP) and coarse steel slag aggregate (SSA) on fracture resistance of asphalt mixes. To this end, a set of 576 Semi-circular bending (SCB) specimens with different ratios of these two marginal materials with and without warm mix asphalt (WMA) additive were prepared in two aging levels and underwent up to five freeze and thaw (FT) cycles. Following, specimens were tested at 25 °C in three-point bending configuration and their critical strain energy release rate (Jc) and flexibility index (FI) were determined and statistically compared to each other. Results disclosed that FT cycles, long-term (LT) aging and the inclusion of RAP decrease the fracture resistance, while the inclusion of SSA increases it. Moreover, incorporation of RAP improves the moisture susceptibility of asphalt mixes, while incorporation of SSA increases this susceptibility. Overall, concurrent incorporation of SSA and RAP was found to be beneficial in improving the fracture resistance and moisture susceptibility of conventional asphalt mixes.