An experimental study on the impact behavior of geopolymer concrete incorporating recycled asphalt pavement aggregate

This study aims to further enhance the potential environmental benefits of geopolymer concrete by incorporating recycled asphalt pavement (RAP) aggregates into the aggregate composition and to experimentally investigate the dynamic impact behavior of this eco-friendly product. RAP aggregate was substituted with fine aggregate at 0%, 33%, and 66% proportions. A total of 18 unique mixtures were formulated. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) served as the binders, with GGBFS-to-binder ratios established at 16.5%, 33%, and 66%. Sodium silicate and sodium hydroxide were employed as alkali activators at two specific ratios (Na₂SiO₃/NaOH): 2.5 and 3. The instrumented drop-weight tests were performed to evaluate the material's impact characteristics by analyzing the time histories of impact force and energy dissipation. Incorporating RAP aggregate resulted in a modest decrease in energy dissipation and impact strength. However, this reduction was effectively offset by GGBFS, resulting in enhanced impact performance relative to the control mixture. A substitution level of 33% RAP exhibited superior impact behavior compared to 66% RAP substitution. The mechanical performance observed under static and dynamic conditions demonstrated that the overall impact resistance of geopolymer concrete can be improved through the partial substitution of RAP, in conjunction with a substantial proportion of GGBFS in the mixture. These findings may indicate that RAP‑substituted geopolymer concrete could serve as a potential and sustainable option for low‑carbon geopolymer technologies requiring high energy dissipation.