The study examines the effects of pressmud (PM), an innovative, sustainable, and beneficial alternative for soil treatment, on the hydromechanical behaviors of sand-bentonite (SB) through a series of laboratory tests, including unconfined compressive strength (UCS), free swelling, and 1D consolidation. SB mixtures with 10 and 15% bentonite (by sand weight) and PM at 4, 8, and 12% (by SB weight) were evaluated. Additionally, microstructural analyses using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to elucidate the mechanisms of soil improvement. The results indicate that PM incorporation reduces the maximum dry unit weight while significantly enhancing the UCS of SB mixtures, with maximum strength increases of 111.5 and 65.5% observed in mixtures containing 10 and 15% bentonite, respectively, after 28 days of curing. These changes help not only enhance the strength properties but also decrease the self-loading on the landfill liner. Moreover, higher PM contents exhibit a dual impact of reducing swelling strain while slightly increasing both compressibility and permeability. Despite the marginal increase in permeability, it still meets the necessary criteria for serving as a landfill liner (< 10(-7) cm s(-1)). The observed effects of PM on SB behavior can be ascribed to the synergistic effects of natural fibers and cementitious gels, as confirmed by microstructural analyses. The natural fibers mainly contribute to the shear resistance of the interface, while the cementitious gels bridge and interlock the solid particles, thereby enhancing the hydromechanical performance of SB. It is concluded that the reuse of PM in soil stabilization not only enhances the hydromechanical performance of SB but also results in better PM management.

This paper utilizes both the ionic soil stabilizer (ISS) and sand to strengthen bentonite, as ISS effectively reduces its expansive properties and sand rapidly improves its strength to reduce cracks. Various experiments are conducted to analyze the changes in physical and mechanical properties of the bentonite strengthened by ISS-sand (ISB). The results show that not only do the sand particles enhance the strength of bentonite, but also the ISS significantly reduces its expansibility. Furthermore, the mass ratio of sand to bentonite has different effects on the unconfined compressive strength (UCS) and the freeze-tolerance of sand-reinforced bentonite (SB) and ISB. These findings suggest that a comprehensive consideration of the sand mixing rate is necessary when implementing ISS reinforcement on natural expansive soil.