Sulphate resistance of geopolymer mortars incorporating waste clay brick powder.

The high carbon emissions and environmental impact associated with ordinary Portland cement have driven the search for sustainable alternative binders. In this context, waste clay brick powder, generated in large quantities from construction and demolition waste, offers a promising aluminosilicate source for geopolymer production. This study investigates the long-term durability performance of geopolymer mortars incorporating waste clay brick powder in terms of resistance to aggressive sulphate exposure, highlighting the potential of waste clay brick powder geopolymer as a potential sustainable building material. Mortars with 0-60% waste clay brick powder content were immersed in 5% Na₂SO₄ solution for up to 180 days to assess the chemical resistance, dimensional stability, and mechanical performance. Microstructural and phase analyses using X-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy revealed a cohesive matrix with limited microcracking and minimal sulphur ingress, indicating strong chemical and structural stability. Moderate waste clay brick powder incorporation enhanced matrix durability, with compressive strength peaking at approximately 69 MPa after 180 days, compared to 63 MPa for the control with a decline in strength at higher waste clay brick powder contents. After 180 days of sulphate exposure, compressive strength reduction ranged from 10 to 19% across all mixes. Mixture W40 showed the lowest expansion of 0.0516%, compared to 0.0632% in the control and 0.0757% in W60. The mass gain was 1.91% for mix W40 compared to 2.8% for the control, indicating reduced susceptibility to sulphate ingress. These results indicate the potential of waste clay brick powder as a sustainable binder for durable building materials, contributing to enhanced performance in aggressive environments.