Influence of recycled clay brick and ceramic tile replacements on the mechanical performance of alkali-activated mortar

This study evaluates synergistic effects of alkali activator concentration, recycled clay brick powder (CBP), and ceramic tile powder (CTP) on alkali-activated mortars (AAMs). Sodium hydroxide (NaOH) concentrations ranging from 8 to 16 molarity were utilised. CTP replaced CBP at levels of 0, 20%, 40%, 80%, and 100%. As an amorphous reactive, glass powder was included in all mixtures. Water absorption, sorptivity, and compressive strength were measured at 28, 56, 90, and 120 days. The results exhibited that while having lower early-age reactivity than clay brick powder, ceramic tile powder contribution to strength enhancement and durability increased with longer curing durations. Compared to CBP-only mixes, highest increases were observed after 90 days, when compressive strength rose by up to 216% and water absorption dropped by 9.96%. Conversely, mechanical and transport properties were consistently compromised by raising the NaOH concentration over 8 M; mixes containing 16 M exhibited reduced compressive strength and increased sorptivity. The 8 M NaOH generated the best balance between matrix densification and reactivity, resulting in the maximum compressive strength and the lowest water absorption and sorptivity. These results demonstrate a distinct relationship between precursor composition and activator concentration, validating CBP and CTP as practical, high-performing precursors for AAMs.