Experimental study on the engineering performance of LSP stabilized expansive soil under cyclic drying-wetting condition

Conventional binders to treat expansive soil commonly present challenges of high cost and significant environmental burdens. To address these limitations, this study proposes an environmentally sustainable binder termed LSP (lime-sodium silicate amended phosphogypsum) based on the valorization of phosphogypsum (PG). Systematic laboratory tests were conducted to evaluate the engineering performance of LSP stabilized soil under drying-wetting cycles. Results indicate that the expansive soil stabilized with LSP obtains a higher maximum dry density and a lower optimum moisture content. The swelling-shrink potential is weakened as well. However, the successive D-W cycles imposes detrimental impacts on the development of all the geotechnical indexes, including free swelling index, unconfined compressive strength (UCS), shear strength, compressibility and permeability. LSP reduces FSI from 58.6% to 32.1%; UCS decreases by 26.5% after 15 cycles; permeability increases 1.65-fold. XRD and MIP analyses reveal that physical filling by PG powder constitutes the primary mechanism for the improvement of soil engineering properties, while micro-crack development is the controlled mechanism for the deterioration induced by D-W cycles.