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

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.