Experimental feasibility study of geopolymer as the next-generation soil stabilizer

In many civil engineering constructions, soft and weak soils are often stabilized with ordinary Portland cement (OPC) and lime. The production processes of traditional stabilizers are energy intensive and emit a large quantity of CO2. Geopolymer, with its high strength, low cost, low energy consumption and CO2 emissions during synthesis, offers a promising alternative to OPC. In this study, a lean clay was stabilized with metakaolin based geopolymer at different concentration (ranging from 3 to 15 wt.% of unstabilized soil at its optimum water content) to examine the feasibility of geopolymer in stabilizing soils. Geopolymer stabilized soil specimens were characterized with compressive strength testing, volume measurements during curing, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The testing results indicated that with geopolymer concentrations, compressive strength, failure strain and Young’s modulus of the stabilized soil specimens increased, and shrinkage strains during curing decreased. The microstructural analyses confirmed the formation of geopolymer gels in the stabilized soil, and showed the soil tended to form more homogeneous and compact microstructures after stabilization. This study illustrated that metakaolin based geopolymer can be an effective soil stabilizer for clayey soils. Further studies on the long-term performance of geopolymer stabilized soils, the use of geopolymers synthesized from industrial wastes, and the financial and environmental cost of applying geopolymer in soil stabilization are worth being conducted.