Strength and Swelling Properties of Engineered Water Repellent Treated Expansive Soils

Abstract: Expansive soils, known for their shrink-swell behavior due to changes in moisture content, pose significant challenges for pavement construction. These soils can expand significantly when wet and shrink when dry, leading to instability and structural issues in pavement systems. Despite various stabilization techniques developed to address this issue, many solutions suffer from long-term durability problems, especially when subjected to high moisture environments. With recent flooding and natural hazard events across the country, including in Florida, there is a pressing need to enhance the moisture resilience of pavement soils, particularly those with high shrink-swell potential. This study explores the potential of organosilane treatment as a means of improving the moisture resistance of expansive soils. Organosilanes, compounds that chemically bond with soil particles, create a water-repellent barrier that minimizes water absorption and promotes moisture resistance. When applied to expansive soils, the organosilane treatment inhibits the expansive and shrinking properties of clay minerals that typically drive undesirable swelling behavior. The research specifically focuses on evaluating the impact of organosilane treatment on both the strength and shrink-swell characteristics of selected expansive soils. To achieve this, a series of laboratory tests were conducted, including direct shear tests to assess soil strength, and one-dimensional (1-D) swell tests and free swell tests to measure changes in the swelling potential of treated versus untreated soils. The direct shear tests provide insights into the treated soils' ability to withstand applied stresses, while the swell tests quantify the reduction in swelling behavior achieved through organosilane treatment. The findings of this study demonstrate that organosilane-treated soils exhibit significantly reduced swelling potential compared to untreated samples. The hydrophobic barrier created by the organosilane treatment prevents excess moisture from penetrating the soil, thereby maintaining its volume and minimizing the deformation commonly associated with expansive soils. This moisture resistance is especially beneficial in flood-prone areas, where soil moisture levels can fluctuate dramatically, making untreated expansive soils particularly problematic. Furthermore, the direct shear tests reveal that the organosilane treatment does not adversely impact the strength properties of the soils, allowing them to maintain their load-bearing capacity even in challenging environmental conditions. Engineered Water Repellency treatment offers a sustainable approach to soil stabilization. Expansive soils are often discarded due to their problematic properties, resulting in significant financial, energy, and carbon costs associated with excavation, transport, and replacement. By rendering expansive soils suitable for use through moisture-resistance treatments, this study promotes the sustainable use of these materials, reducing the environmental impact of construction projects. The technique can be applied alongside existing stabilization methods to further enhance the durability and resilience of pavement structures, offering a multifaceted approach to addressing the challenges posed by expansive soils.