Effect of gemstone polishing waste on hydration, strength development, and electrical/thermal properties of cement-based materials: A multiscale study

Gemstone polishing waste (GPW), a non-biodegradable by-product rich in silicon carbide (SiC), poses significant environmental challenges when landfilled. Its incorporation as a partial cement replacement offers a sustainable strategy to mitigate pollution and reduce CO2 emissions associated with cement production. This study employs a multiscale approach to investigate the effects of GPW on the hydration behavior, microstructure, mechanical properties, and functional attributes of cement-based materials. At the nanoscale, zeta potential measurements reveal GPW’s low affinity for Ca2+ ions, which delays early-stage ion interactions and hydration kinetics. Microscale analyses, including scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, and mercury intrusion porosimetry, indicate reduced C–S–H nucleation efficiency, phase stability without new product formation, weak interfacial bonding, and a coarser microstructure with increased porosity. At the macroscale, GPW incorporation leads to prolonged induction periods and decreased compressive strength due to dilution and poor bonding, but enhanced thermal conductivity and reduced electrical resistivity. These improvements stem from SiC’s inherent properties and the resultant higher pore solution content from incomplete hydration. Overall, while GPW compromises mechanical performance, it enhances multifunctional properties, positioning it as a viable additive for smart or energy-efficient cementitious materials.