Mechanical and Behavioral Properties of Boubyan Clay Mixed with Styrofoam

Introduction This research investigated the effects of incorporating Styrofoam grains (Expanded Polystyrene, EPS) into Boubyan clay (Kuwait) to develop a lightweight, sustainable geotechnical material. Materials and Methods The soil was classified as CL (lean clay) based on the Unified Soil Classification System (USCS). Samples were mixed with 0%, 10%, 15%, 20%, and 25% Styrofoam (2–5 mm grains) by volume. Standard Proctor compaction tests were used to determine maximum dry unit weights and optimum moisture contents. consolidation tests measured swelling pressures and displacements. Coefficients of volume compressibility (m_v) and consolidation (c_v) were calculated. Finally, consolidated-undrained triaxial tests assessed shear strength parameters (cohesion C′ and friction angle φ′). Results The addition of EPS reduced the maximum dry unit weight and increased the optimum water content. Swelling pressures and displacements decreased with higher EPS content; m_v and c_v both declined, indicating reduced compressibility and slower consolidation. Void ratios decreased, while final settlements and strains increased with Styrofoam. Triaxial tests showed a decrease in cohesion (C′) and an increase in friction angle (φ′) as the Styrofoam content increased, resulting in lower maximum shear and normal stresses. Discussion Introducing EPS into Boubyan clay improved its strength-to-weight ratio by reducing compressibility and slowing consolidation, though at the expense of increased settlements and reduced cohesion. These trade-offs suggest an optimal EPS content (around 10–15%) and point to future work, such as adding bonding agents ( e.g ., cement), to mitigate strength losses. Conclusion Integrating Styrofoam grains into Boubyan clay offers a viable method for producing a lightweight additive by reducing compressibility, aiding densification, and modifying strength parameters for specialized civil engineering applications.