Potential Use of Brick Waste for the Production of Geopolymer Roof Tiles

The construction and demolition waste sector produces significant quantities of brick waste (BW), which can be repurposed for creating new eco-friendly materials. This study assesses the feasibility of utilizing waste brick in metakaolin-based geopolymers and measures their key physical and mechanical properties. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) served as the activating alkaline solution. Various formulations were developed, incorporating increasing amounts of brick waste. The molded samples were cured at room temperature for 24 hours, with their upper surfaces covered by a thin plastic film to minimize moisture loss. Following this initial curing, the specimens were demolded and further cured at room temperature for 28 days. Comprehensive analyses were conducted, including particle size distribution, chemical characterization, X-ray diffraction, specific gravity, and pozzolanic activity of the solid precursors. Additionally, physical and mechanical tests were performed on the geopolymer specimens, assessing flexural and compressive strength, ultrasonic pulse velocity, Leeb rebound hardness, real and apparent densities, water absorption, and porosity. The chemical and mineralogical analysis of the brick waste revealed a high concentration of reactive silica and alumina, essential components for geopolymer synthesis. The compressive strength achieved for geopolymers containing waste brick powder was approximately 30 MPa, with a metakaolin to brick waste ratio of 90/10, utilizing 10M NaOH and a hydroxide to silicate ratio of 1:2; the corresponding ultrasonic pulse velocity and Leeb hardness values were around 2000 m/s and 650 HLD, respectively. Geopolymeric mortars produced with a binder to aggregate of brick waste ratio of 1:3 exhibited promising mechanical properties (about 50MP) comparable to fired clay bricks. The findings suggest that incorporating brick waste into geopolymer binders and mortars can yield both environmental and economic advantages by providing an alternative to fired brick in construction.