The chemical stabilization is well-recognized for improving mechanical properties of problematic soils. In this study, sodium alginate was investigated as an environmentally friendly soil-surface stabilizer to enhance the unconfined compressive strength (UCS) of a high plasticity clay. The compacted soil samples were surface-stabilized with sodium alginate at various concentrations of 0%, 0.25%, 0.5%, 0.75%, 1%, and 1.25% by two methods (soaking and spraying). The UCS of stabilized samples was measured after 1, 14, and 28 days of curing. The soaking method of sodium alginate significantly improved the UCS of the samples at the one day of curing; however, beyond this time, the UCS decreased with the increased curing time. The soil stabilized by soaking method had higher 1-day UCS than the soil stabilized by spraying method at the optimum sodium alginate concentration of 1.25%. But the soil stabilized by spraying method had higher long-term UCS than the soil stabilized by soaking method. Microstructural analysis results indicated that a novel cementitious material, sodium aluminosilicate, improved the soil structure by filling the pore space and enhancing interparticle bonding strength; hence the strength improvement. The outcome of this study will promote the surface-stabilization process using the environmental-friendly sodium alginate in infrastructure applications.
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