Mechanical and microstructural analysis of soft kaolin clay stabilized by GGBS and dolomite-based geopolymer

Abstract

The utilization of industrial waste-based geopolymer has emerged as an environmentally sustainable approach with a low carbon footprint in place of ordinary Portland cement (OPC) for ground improvement. This study aims to investigate the impact of ground-granulated blast furnace slag (GGBS) and dolomite-based geopolymer on the mechanical and microstructural properties of soft clays. A series of unconfined compressive strength (UCS) tests and pH tests were conducted to evaluate the effect of precursor (binder) content, GGBS and dolomite (S:D) ratio, NaOH:Na2SiO3 (NH:NS) mass ratio, and curing period on the strength development of GGBS and dolomite based geopolymer treated kaolin clay. A series of consolidated undrained (CU) static triaxial tests were performed on 28 days cured specimens with different S:D ratios and optimum NH:NS mass ratio to determine the axial stress-strain characteristics. Moreover, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) tests were conducted to analyze the microstructure characteristics of GGBS and dolomite-based geopolymer. Experimental results indicate that the optimum NH:NS ratio for only GGBS (S:D ratio of 20:0) treated clay was 50:50, whereas, for S:D ratios of 18:2, 16:4, and 14:6, the ratio was 25:75. The addition of dolomite up to 4% with GGBS and NH:NS ratio of 25:75 significantly enhanced the 28 days compressive strength to 116.8% compared to pure GGBS-based geopolymer treated clay. Furthermore, the compressive strength of the clay stabilized with a precursor of S:D ratio of 16:4 and NH:NS ratio of 25:75 was 26.30%, 32.59%, and 38.35% higher than the 20% OPC stabilized clay for the 7, 14, and 28 days curing period, respectively. Moreover, the toxicity characteristic leaching procedure (TCLP) results showed that heavy metals concentration was much lower than their respective US Environmental Protection Agency (USEPA) specified standard limit. The findings of this study provide effective utilization of GGBS and dolomite as a new eco-friendly geopolymer for stabilizing soft soil. © 2024 Elsevier Ltd