Production of green bricks from low-reactive copper mine tailings: Durability and environmental aspects

In response to the net-zero emissions plan for 2050, geopolymerization of mine tailings (MT) has attracted massive attention from construction material researchers and engineers. To successfully recycle or reuse MT through geopolymerization, it is essential to have a reliable understanding of the environmental and durability aspects of the geopolymer products. This study investigates the durability and leaching behavior of geopolymer bricks produced from low-reactive copper MT as the primary aluminosilicate precursor and slag as the supplementary cementitious material (SCM). Durability tests include fourteen (14) wet-dry cycles and fifty (50) freeze–thaw cycles, respectively. After the durability test, the weight loss and unconfined compressive strength (UCS) of the geopolymer brick specimens were measured. The leaching study was conducted following TCLP guidelines by immersing the geopolymer brick specimens in solutions with pH = 4 and 7, and measuring the concentration of contaminants in the solution after 120 days. After the leaching test, the wet and dry UCS of the geopolymer specimens were measured. In addition, microscopic studies including SEM/EDX and XRD were performed to study the microstructural changes and the phase composition. The results show a substantial loss in UCS after the durability tests. However, the weight loss is small compared with conventional cementitious materials. Most importantly, the contaminants in the MT are successfully stabilized within the geopolymer framework.