Evaluating the dual role of sea water and metakaolin in the performance, efflorescence mitigation, and phase composition of sodium silicate-activated marble powder

Marble waste (MW) poses a significant environmental challenge due to its large quantities and difficulty in disposal. This study explored the full utilization of MW powder in creating binder. Combining MW with sodium silicate (Na₂SiO₃) results in the formation of calcium silicate hydrate (C-S-H) and pirssonite. The resulting binder demonstrated a compressive strength of 15–25 MPa after 28 days of air curing. Using metakaolin provides the system with dissolved aluminosilicate, which mitigates efflorescence through a neutralization process and enhances the compressive strength of the resulting hardened binder. Seawater also proved effective in reducing efflorescence by decreasing the solubility of pirssonite. Moreover, mixing seawater with Na₂SiO₃ induced the formation of nanoprecipitates, which positively affects the mechanical performance of the resultant binder. For sustainable building practices, using seawater as a mixing water for unreinforced building products is recommended. This conserves freshwater, making it available for other critical applications.