To ameliorate the performance of recycled aggregate concrete (RAC) by pre-treating aggregate in sulfoaluminate cement slurry and water glass solution

This work proposes to ameliorate the performance of recycled aggregate concrete (RAC) by enhancing the interfacial transition zone (ITZ). In light of this, the recycled aggregate was pre-treated by the sulfoaluminate cement (SAC) slurry and water glass (WG) solution at varying water-to-SAC (w/s) ratios and WG concentrations, respectively. The optimum modification efficiency was observed at a w/s ratio of 0.8 and a WG concentration of 3 wt%. It was found that the SAC-treatment of RA led to a layered, sandwich-shaped new ITZ which presented an overall higher microhardness compared to the normal ITZ in the reference RAC. The WG-treatment enhanced both the new and old ITZ but its modification on RAC's mechanical/durability performance was less stable than the SAC-treatment. The SAC treatment is thereby suggested to be more appropriate for RAC's modification in practical use, also considering its lower risk of alkali-silica reaction than the WG treatment.