Production of green bricks from low-reactive copper mine tailings: Chemical and mechanical aspects

To achieve sustainable construction and respond to the ever increasing demand for construction materials, including bricks, it is in an urgent need to use innovative technologies, like geopolymerization, to produce green and sustainable construction materials. Therefore, this study investigates the utilization of low-reactive copper mine tailings (MT) with slag (SG) as a supplemental cementitious material to produce green bricks based on the geopolymerization technology. To this end, the effects of several parameters including NaOH molarity (10 and 15 M), Na₂SiO₃/NaOH ratio (0, 0.5, 1, 1.5, 2, 2.5, and 3), slag (SG) content (0, 10, and 20 wt% of MT + SG), forming pressure (0, 5, 10, 15, 20, and 30 MPa), water-to-solid ratio (0.12, 0.14, and 0.16), and curing temperature (60, 75, 90, 105, and 120 ℃) on the physical and mechanical performance of geopolymer brick specimens are investigated through unconfined compression and water absorption tests. In addition, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses are conducted to understand the changes in microstructure and phase composition after geopolymerization. The results show that using only MT does not lead to a durable geopolymer product because of the low leaching of Si and Al species from the MT. However, with the incorporation of SG as a supplementary cementitious material, geopolymer bricks that satisfy the ASTM requirements can be produced.