Study on the properties and microstructure of metakaolin cement mortar under microwave curing

To mitigate the reduction in early age strength associated with metakaolin (MK) incorporation, this study investigated the combined effects of MK and microwave curing on the mechanical properties and multiscale microstructure of cement mortar. Cement mortars with 0%, 10%, and 20% MK contents were subjected to standard and microwave curing. The results demonstrated that microwave curing effectively offset the early age strength deficiency of MK mortars and further improved the 28-day strength, with the specimen with 10% MK achieving the most pronounced enhancement. Multiscale characterization (scanning electron microscopy, X-ray diffraction analyses, nitrogen adsorption analysis, and nanoindentation) revealed that microwave curing promoted matrix densification, accelerated pozzolanic reactions, refined pore structures, and increased the fraction of high-density C-S-H. A notable synergistic effect was observed between 10% MK and microwave curing, leading to narrower interfacial transition zones and a higher ITZ modulus. Furthermore, the combined incorporation of metakaolin and microwave curing enhances the environmental and economic performance of cement mortars. These findings highlight a potential pathway for developing low-carbon, high-performance cement-based materials with practical relevance for accelerated construction and sustainable infrastructure.