Conjoint reuse of ceramic polishing waste and calcium carbide slag as mineral admixtures: Hydration and mechanical properties

Reusing calcium carbide slag (CCS) and ceramic polishing waste (CPW) as mineral admixtures can reduce the consumption of cement and the stockpiles of CCS and CPW. Studies on CCS improving the pozzolanic reaction of CPW have yet to be published. In this work, CCS was added to cement-based composites to provide sufficient CH for the pozzolanic reaction of CPW. The influence of CCS and CPW on the hydration, mechanical performance, and autogenous shrinkage of composite pastes or mortars was studied. The hydration kinetics, hydration products, and microstructures of the composite pastes were characterized using isothermal conduction calorimetry, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP). The results showed that the CH contents of the composite pastes at 28 d are lower than those at 7 d, that is, the pozzolanic reaction of CPW consumes a considerable amount of Ca(OH)2 in the system. Meanwhile, CCS supplies sufficient CH for this reaction and improves the CPW reaction degree. Macroscopically, the pozzolanic reaction of CPW promotes the strength development of composite mortars at a late age. Nonetheless, most composite mortars have lower compressive and flexural strengths than cement mortars, especially at an early age. In addition, the composite pastes have more micropores, which enhance the capillary pressure and further increase the autogenous shrinkage. This work contributes to the recycling of CPW and CCS, potentially lowering construction costs and increasing sustainability. •Calcium carbide slag was added to composite pastes as a calcium hydroxide source.•CCS improves the reaction degree of ceramic polishing waste.•Composite mortars have lower compressive and flexural strengths than cement mortars.•Addition of these mineral admixtures increase autogenous shrinkage.