Waste Brick as Partial Replacement of Gypsum in Mortars: Mechanical Performance and Environmental Benefits for Sustainable Construction

Abstract

Replacing virgin raw materials with recycled waste in construction products is a key strategy for advancing sustainable development. This study explores the partial substitution of commercial gypsum with powdered waste brick (WB) in gypsum mortars, assessing its impact on mechanical performance, water absorption, and environmental footprint. Mortars were prepared with 0%, 5%, 10%, 20%, and 30% WB by weight. Results indicate that a 20% replacement level enhances flexural strength by 56% and compressive strength by 33% at 28 days, compared to the reference mix. SEM and XRD analyses revealed no formation of new crystalline phases, suggesting that the performance improvement is primarily due to physical interactions and microstructural effects. However, at 30% WB, a significant reduction in adhesion strength was observed, falling below the typical threshold for gypsum-based coatings, which may constrain practical application at higher replacement levels. Environmental assessment showed that both CO2 emissions and energy consumption decreased by up to 20% with a 30% substitution. A 20% WB content is therefore proposed as the optimal compromise between mechanical performance and environmental benefit. This approach supports circular economy principles by promoting the reuse of ceramic construction waste in the development of new sustainable materials.