Experimental study on compressive strength of clay soil stabilized with construction and demolition waste-based geopolymer

This study investigated soil stabilization on clay soil using construction and demolition waste (CDW) as a geopolymer binder. The mechanical performance of stabilized soil was investigated under various CDW-based geopolymer amounts, curing times, and alkali activator concentrations. Unconfined compressive strength (UCS) testing was conducted to determine the shear strength of soil samples. The UCS capacities of soil samples were approximately 8.1, 12.2, and 14.6 times higher than the unstabilized soil sample for 7, 28, and 91 days of curing. Moreover, it is observed that increasing the molarity of alkali activators, especially NaOH, enhanced the UCS capacity of geopolymer-stabilized soil. However, using Na2SiO3 in combination with NaOH had a negative impact on UCS capacity. Because the water in the Na2SiO3 content increased the water content of the soil sample and caused it to have a softer consistency, this was also observed with the increase in activator solution to binder (s/b) ratios. SEM–EDX and XRD tests were performed to investigate the microstructure of stabilized samples. These tests showed that there was agreement with the UCS test results. Finally, a Multiple Linear Regression (MLR) and Artificial Neural Network (ANN) analysis were performed to estimate UCS capacity of geopolymer-stabilized soils. © The Author(s) 2025.