Ambient Silicate Curing Transforms Compacted Recycled Concrete Powder Into a Low‐Carbon Construction Material

ABSTRACT

Recycled concrete powder (RCP) derived from demolition waste is largely underutilized due to its inherently low binding capacity. Here, we investigate a sodium silicate solution curing method that refines the pore structure of compacted RCP at ambient temperature, without thermal treatment or CO ₂ exposure. Compacted RCP specimens are cured in sodium silicate solutions at 0, 6, and 12 wt% concentrations. After 28 days, the 6% treatment reduces water absorption rate by 75%, and increases flexural strength by 69% compared to the uncured sample. Microstructural characterization reveals rapid calcium consumption to form calcium silicate hydrate and silica‐rich gels, which establish interparticle bridges and refine the capillary pore network. The 6% condition outperformed the 12% condition, suggesting a kinetic threshold at which excessive silicate concentrations trigger rapid surface mineralization that creates a diffusion‐limiting barrier, restricting further water and ion transport and hindering the continued hydration of unreacted cement. This study uses an extensive naturally carbonated RCP, indicating that the route does not depend on a high residual portlandite content. A cradle‐to‐gate assessment indicates 89%–91% lower carbon emissions than conventional autoclaved and carbonation‐cured concrete bricks.