Strength and Fracture Properties of Sandy Subgrade Soil Treated with Sodium Polystyrene Sulfonate

Organic polymers have been extensively studied over the last decades, and most of the research focused on the mechanical performance of the soils treated with polymer at different dosages without addressing the effects of the unique polymer characteristics such as molecular weight and concentrations of polymer solutions. This paper investigates an anionic polyelectrolyte, sodium polystyrene sulfonate (PSS) as a soil stabilizer. The effects of the molecular weight of PSS, concentrations of PSS solutions, and the dosages on the strength of a siliceous sandy subgrade soil are examined. Fracture toughness of the PSS-treated soil is determined and discussed based on semicircular bending test. Three molecular weights (1,000,000, 200,000, and 70,000 g/mol) along with solution concentrations of 10%, 17%, 23%, and 30% by weight are considered. The dosages of PSS solutions at 2%, 4%, 6%, and 8% by weight of dry soil are discussed. All the dosages studied showed strength improvement of the sandy soil that increased with concentrations of the PSS solutions as well as the increasing dosages. PSS with the highest molecular weight performed the best among all three molecular weights. The addition of the organic polymer also improved the fracture toughness of the soil, indicating better resistance to crack propagation. The stabilization mechanism in terms of particle linkage and aggregation morphology are examined using scanning electron microscope. Aggregation of the fine soil particles and binding between the fine and coarse soil grains are observed and discussed, which contribute to the improvement of mechanical strength of the soil.