Characterization of a Binary Alkali-Activated System Based on Ceramic Waste and Metakaolin

The red ceramics industry is a significant generator of solid waste, which can be reused in construction to reduce the consumption of natural resources and lower CO₂ emissions associated with Portland cement production. However, red ceramic waste (RCW) as a precursor in alkali-activated materials remains underexplored. This study aimed to evaluate a binary mixture of RCW and metakaolin (MK) for producing alkali-activated cements. Four pastes were prepared with varying proportions of RCW and MK. In the fresh state, mini-slump tests, setting time measurements, and fresh density determinations were performed. In the hardened state, compressive strength was evaluated at 7, 28, and 91 days, along with water absorption. Additionally, Scanning Electron Microscopy (SEM) analysis was conducted. The paste composed of 100% RCW exhibited the greatest spread (94.5 mm), whereas the mixture with 75% MK and 25% RCW achieved the highest compressive strength of 42.79 MPa at 7 days. SEM analysis revealed the formation of binder gels, confirming the viability of using RCW and MK in alkali-activated cement pastes.