Experimental investigation on enhancing the geotechnical properties of sabkha soil using sodium silicate and waste glass powder to reduce collapsibility.

Abstract

Sabkha soils, widely distributed in arid coastal regions, are characterized by high salinity, metastable structure, and low bearing capacity, posing significant challenges for geotechnical applications. Although sustainable stabilization methods have been increasingly explored, the application of alkali-activated waste glass powder (WGP) to highly saline sabkha soils, with emphasis on linking engineering performance to microstructural characteristics, remains insufficiently investigated. This study investigates the effectiveness of alkali-activated WGP as a sustainable and environmentally beneficial stabilizer for sabkha soil. WGP was incorporated at 10-30% by dry soil mass and activated using a sodium silicate-sodium hydroxide solution (Na₂SiO₃: NaOH = 2:1). The treated soils were evaluated through Standard Proctor compaction, California Bearing Ratio (CBR) under soaked and unsoaked conditions, and unconfined compressive strength (UCS) at curing periods up to 90 days, complemented by Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS) analysis. The results reveal a property-dependent optimum WGP content. The highest CBR was achieved at 10% WGP (290% under soaked conditions and 180% under unsoaked conditions), while maximum UCS was obtained at 20% WGP, reaching 3550 kPa at 90 days. Although the untreated sabkha soil exhibited relatively high soaked CBR due to temporary salt-induced bonding, alkali activation provided a more stable cementation mechanism, resulting in improved mechanical performance. This distinction indicates that bearing resistance and compressive strength are governed by different mechanisms of stabilization. Excess WGP content (30%) led to reduced performance due to incomplete activation and disruption of particle interlocking. SEM-EDS observations indicated the development of a denser and better-bonded matrix that is consistent with the possible formation of sodium aluminosilicate hydrate (N-A-S-H) gel, accompanied by reduced pore connectivity and improved load transfer. The findings demonstrate that alkali-activated WGP provides an effective and more sustainable approach for stabilizing highly saline sabkha soils, highlighting the importance of property-dependent binder optimization for ground improvement in saline environments.