Valorization of tile waste in geopolymer mortars: A sustainable approach using marble powder, fly ash, and silica fume

Abstract

The increasing accumulation of construction and industrial waste presents environmental and disposal challenges, underscoring the need for sustainable construction materials. This study explores the use of finely ground roof tile waste powder as a primary aluminosilicate precursor in geopolymer mortars, supplemented with fly ash, silica fume, and marble powder to enhance performance. Tile waste was partially replaced with fly ash and marble powder (10-30 %) and silica fume (5-15 %), while sodium hydroxide served as the alkali activator at varying Na/binder ratios. Physical, mechanical, and durability tests revealed substantial improvements compared with the control mix: compressive strength increased by up to 390 % with marble powder, 316 % with fly ash, and 94 % with silica fume, while porosity decreased by 91 %, 75 %, and 40 %, respectively. Higher Na/ binder ratios further improved unit weight, ultrasonic pulse velocity, and compressive strength while reducing porosity and water absorption. Microstructural and chemical analyses (FTIR, XRD, SEM, and EDS) confirmed enhanced geopolymerization, denser matrices, and stronger bonding through aluminosilicate and calcium-based phases. Overall, the findings highlight the potential of tile waste valorization in producing high-performance