From Lime to Geopolymers: Emerging Trends and Advances in Sustainable Soil Stabilization

Soil stabilization remains a critical challenge in geotechnical engineering, particularly for weak and expansive soils that compromise the safety and serviceability of infrastructure. Traditional stabilizers such as lime and cement have been widely applied; however, their limitations in terms of long-term durability, carbon footprint, and performance under aggressive environmental conditions necessitate alternative approaches. In recent years, geopolymer-based stabilizers derived from industrial by-products such as fly ash (FA), slag, and bottom ash (BA) have emerged as promising substitutes. This review critically examines the comparative performance of lime and geopolymer stabilization with respect to strength development, durability, compressibility, environmental impact, and economic viability. Emphasis is placed on their influence on unconfined compressive strength, resistance to wetting–drying and freeze–thaw cycles, and improvements in bearing capacity. Furthermore, the review highlights the environmental advantages of geopolymers, including reduced greenhouse gas emissions and valorization of waste materials, against the well-established field performance and low initial costs of lime stabilization. Key challenges such as activator cost, curing sensitivity, and field-scale application of geopolymers are also discussed. The paper concludes with perspectives on integrating both methods and advancing sustainable soil stabilization practices. The insights provided are intended to guide researchers, practitioners, and policymakers toward more durable and environmentally responsible ground improvement strategies.