Mechanical behavior and microstructure evaluation of eco-friendly mortar containing ceramic wastes

This study explores the partial substitution of cement and natural sand with ceramic waste in cement-based materials. Seven mixtures were prepared at a constant water-to-binder ratio of 0.4, with 20% cement replaced by ceramic powder and five levels of ceramic aggregate substituting natural sand. Compressive strength was evaluated through mechanical testing at curing ages of 7, 28, 90, and 180 d. Hydration products and phase evolution of the blended pastes were characterized using thermogravimetric (TG) and X-ray diffraction (XRD) analysis, while pore structure was assessed by dynamic vapor sorption (DVS) and mercury intrusion porosimetry (MIP) tests. The results indicate that: (1) replacing up to 60% of sand with ceramic aggregate does not adversely affect long-term compressive strength, despite an observed reduction compared to the reference mortar at early curing ages; (2) the progressive decrease in calcium hydroxide (Ca(OH)₂) content over time provides direct evidence of the pozzolanic activity of ceramic waste; (3) with increasing ceramic content, the fraction of fine capillaries decreases while larger gel pores increase, indicating nanoscale pore structure coarsening. These results provide a theoretical and experimental basis for the practical application of ceramic waste in high-performance cementitious composites.