Reducing water absorption of cement mortar by using modified clay brick waste

Abstract

Cement mortar is inherently hydrophilic due to its porous structure, which allows water penetration and adversely affects its durability and long-term performance. To mitigate this issue, hydrophobic cementitious materials can be developed by incorporating hydrophobic substances during mixing to provide hydrophobic properties throughout the material, achieved by introducing a wet chemical method using stearic acid-modified clay brick waste (MCBW) as a hydrophobic agent. The MCBW is prepared by treating clay brick waste with stearic acid (SA) and subsequently used as a partial replacement for fine aggregates. The effects of the MCBW incorporation on compressive strength and water resistance are investigated. When 30% of fine aggregate is replaced by MCBW (by weight), the optimized mortar showed substantial improvements: its 28 day cured compressive strength increased by 12% compared to the control, while achieving water resistance. Hydrophobic behavior is confirmed by a water contact angle of 145° and a significant reduction in the water penetration rate. Microstructural and thermal analyses (SEM and TG/DTG) further revealed that the incorporation of MCBW promotes cement hydration, contributing to improved performance.