Stabilization of soft soil using low-carbon alkali-activated binder

Soft soils pose significant challenges to the constructions on or within them, which are commonly stabilized with lime or ordinary Portland cement. However, these two binders are energy-intensive with high-carbon footprint. The current study presents an investigation of using an alkali-activated binder (AAB), a low-carbon cementitious material, for soft soil stabilization. Experiments including unconfined compressive strength test, compressibility test and hydraulic conductivity test were carried out to investigate the mechanical and hydraulic properties of soils stabilized with AAB of different concentrations. Microstructural characterizations of soil samples before and after AAB stabilization were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The experimental results show that the AAB can greatly improve the strength of the stabilized soil and meanwhile significantly reduce its compressibility and permeability. The strength of the stabilized soil increases with curing period and higher AAB concentration; the compressibility potential of original soil is noticeably reduced from medium to a low level after AAB stabilization; the hydraulic conductivity of soft soil stabilized with 20% AAB is more than 700 times smaller than that of the untreated. The microstructural characterizations using XRD, SEM and EDX confirm the formation of calcium aluminosiliate hydrate (CASH) gel in the stabilized soil matrix. This gel binds the soil particles and fills the voids between them and, therefore, increases the strength and reduces the compressibility and permeability of stabilized soil.