Abstract
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.
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