Improvement of mechanical strength of low-plasticity clay soil using geopolymer-based materials synthesized from glass powder and copper slag

Due to the environmental issues associated with the production of binders such as cement and lime, finding alternative materials or binders for geotechnical applications is crucial. Therefore, developing low-carbon-footprint cementitious materials by replacing cement and lime with recycled waste-based geopolymers can provide environmental and economic benefits. Incorporating recycled waste materials or green binders in soil stabilizations can not only reduce the construction cost and alleviate environmental issues, but also improve the mechanical properties of the soils. Although the idea of using recycled glass powder (RGP) as a reclaimed material for stabilizing clay soils is not new, the adoption of copper slag (CS) or combination of CS and RGP for the treatment of low-plasticity clay soil has rarely been studied. In this research, various molarities of sodium hydroxide as an alkaline activator and different combinations of CS-RGP were used to assess the mechanical and microstructural behavior of the stabilized low-plasticity clay soil. Moreover, the effects of two different curing conditions (i.e., oven-dried content (DC) and optimum water content (OC)) and curing time on the mechanical properties of the soil (i.e., unconfined compressive strength and California bearing ratio) were evaluated. The results clearly indicated that CS influenced Atterberg Limits and compaction parameters more than RGP. Also, it was observed that by applying 5% CS at a fixed alkaline activator, the UCS at 56 curing days and CBR at 7 curing days increased 3.11 and 1.68 times, respectively, while these values were 4.03 and 1.90 times, respectively, by applying 5% RGP.