Utilization of industrial waste—based geopolymers as a soil stabilizer—a review

Ordinary Portland cement (OPC) and lime (L) are widely used in the soft and weak soil stabilization. Various studies have suggested that the production of cement produces high amount of CO₂ gas which is mainly responsible for global warming. An alternative to OPC and L are geopolymers which are less costly, have high strength and durability and produces lesser CO₂ in comparison with OPC and L. Moreover, the production of a geopolymer consumes less energy. This review paper focuses on the studies about the utilization of industrial waste-based geopolymers as a soil stabilizer. In this review, only the geopolymers derived from industrial solid waste have been considered. Effects of different parameters of geopolymers such as different percentage mixes (%), molarity (M), temperature (T), curing time (days), alkaline activator ratio (AA) and water/binder (w/b) ratio on the geotechnical properties of soil have been discussed. Further, effects of morphological and microstructural behavior of geopolymers on the geotechnical properties of soil have also been discussed. In this review, it has been found that 5–20% mixing of geopolymer, 8–12 M molarity, 25–45 °C T, 7–28 days of curing, 1.5–2.5 AA ratio and 0.35–0.85 w/b ratio are the optimal range of parameters of geopolymer which gives a significant improvement in the geotechnical properties of soil. Further, morphological and microstructural analysis studies show that the formation of C–S–H gel, silicate, calcite and aluminate compounds are mainly responsible for the improvement in the geotechnical properties of soil. The soil stabilized using industrial waste-based geopolymers have potential applications in the ground improvement, subbase and base course of flexible pavements. Moreover, this soil stabilization technique not only utilizes the industrial solid waste in a more purposeful manner but also is very cost-effective and eco-friendly.