Utilization of ceramic and brick waste in geopolymers: A preliminary study of physical and mechanical properties

Geopolymers represent a sustainable alternative to traditional binders, as they utilize industrial and construction waste, contributing to a reduction in the environmental impact. In this context, the present research focuses on the fabrication of geopolymers from ceramic and brick powder obtained from construction waste through milling and fine sieving, resulting in particles smaller than 150 μm. The study evaluated the influence of three factors on the physical and mechanical properties of the geopolymers: sodium hydroxide (NaOH) concentration, the mass ratio of sodium silicate (Na₂SiO₃)/NaOH, and the curing method. Mixtures were prepared with mass ratios of 2:1 and 2.5:1 (Na₂SiO₃:NaOH), using dry NaOH dissolved in concentrations of 5, 7.5, 10, and 12 mol/L. A constant liquid-to-solid ratio of 0.4 was used and this was adjusted with additional water to improve workability. Three curing conditions were tested to determine the optimal method: air curing for 7 days, curing in a humid environment for 7 days, and mixed curing (6 days in air and 1 day at 60 °C before the compressive strength test). The characterization of the hardened samples included tests for density, absorption, and voids, as well as compressive strength. The preliminary results indicate that mixed curing produces higher mechanical strength and that the workability of the mixtures vary depending on the NaOH concentration and the Na₂SiO₃/NaOH ratio. This work provides criteria for optimizing the preparation and curing of geopolymers made with ceramic and brick waste, promoting their application in civil engineering within a sustainable context.