This study examined soda residue (SR) and ground granulated blast furnace slag (GGBS) to stabilize soft soil in comparison with using portland cement (PC). The shear strength of samples was measured to study the additive dosage and curing time effect on the additive performance. Microstructural investigations were conducted using pH, thermogravimetric analyses, X-ray diffraction, and scanning electron microscopy to correlate with shear strength of the treated soil. The results indicated that the presence of SR can increase the shear strength of soft soil and the optimum content is approximately 30% to yield the highest cohesion. Soil stabilization using a mixture of SR and GGBS increased shear strength as GGBS content and curing time increased. Shear strength of SR-GGBS-stabilized soil was close to that of the corresponding SR-PC-stabilized soil after curing for 28 days. The main hydration products detected for SR-GGBS-stabilized soil included calcium silicate hydrates, calcium aluminate hydrates, ettringite, and calcium chloroaluminate hydrates. The results will contribute to the use of SR and GGBS as effective stabilizers for soft soil.

This study investigates the effect of soaking conditions on the durability of soft soil treated with soda residue and ground granulated blast furnace slag. Specimens were cured for up to 60 days and soaked in solutions for up to 28 days. Tap water (T), NaCl (N), ${\mathrm{MgSO}}_4$ (M), and $\mathrm{NaCl}+{\mathrm{MgSO}}_4$ (N-M) were selected as soaking solutions. The results indicate that the stabilized soil was durable in tap water even cured for two days. When soaked in T or N environment, the strength of the specimens increased with soaking period due to dense structure and hydrated gel filling between matrix. The strength of the specimens soaked in solutions was slightly higher than that in tap water. However it decreased slightly after soaking for 28 days in M or N-M environment due to looseness at the ends of the specimens and formation of ettringite cluster. The effects of reinforcing and filling-in of hydration products, including calcium silicate hydrates, ettringite, calcium chloroaluminate hydrates and calcium chloride hydroxide hydrate, contributed to an improvement in strength and durability.