Investigating the Mechanical and Microstructural Characteristics of Clayey- Sand Reinforced with Geopolymer Incorporating Copper Slag

This study aimed to explore the effects of stabilizing clayey-sand with mineral geopolymers, focusing on the mechanical and microstructural behavior of the treated soil. Experimental tests, including Atterberg limits (PI), pH analysis, standard proctor compaction, unconfined compressive strength (UCS), and ultrasonic P-wave velocity measurements, were conducted at different curing durations (2, 7, 14, and 28 days) under ambient temperature conditions (23 ± 2°C and ˃90% relative humidity). Additionally, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed to investigate the microstructural effects on strength enhancement. The study employed various combinations of non-traditional binders (copper slag) with an alkaline activator solution (AAS). The AAS consisted of 70% Na 2 SiO 3 and 30% NaOH, while the weight ratio of copper slag to AAS was set at 1. Different molar concentrations of NaOH (0, 2, 4, 8, 11, and 15M) and varying percentages of copper slag (0, 10, and 15%) were selected. The results revealed three distinct behaviors exhibited by the samples. Notably, the strength increased with longer curing times for 8M and 11M concentrations, indicating a significant strength gain. Numerical investigations also established a correlation between P-wave velocity and UC strength. Microstructural analysis identified the sample with 11M NaOH and 15% copper slag as having the most compacted and dense structure.