Durability and Permanency Studies in Sulfate-Laden Soils Treated with Nano- and Crystalline Silica-Based Admixtures

Abstract

A research study was performed to assess the durability and permanency of chemical treatment in sulfate-rich expansive soils with novel silica-based admixtures and calcium or Ca-based stabilizer. Crystalline Silica (CS) and Nanosilica (NS) admixtures were selected and used with a traditional dolomitic-hydrated lime to treat problematic high-sulfate expansive soils. The chemically treated soils were investigated for the changes in plasticity at different curing periods, and subsequently, strength tests were performed before and after subjecting the soil specimens to moisture conditioning through capillary soaking. The values of strength, volumetric swell strains, and weight changes after moisture conditioning were compared with those of control specimens. To study the permanency of treatment method, leaching studies were performed using internal flushing on the chemically treated soils to simulate the moisture ingress/digress into subsoils. The effects of different silica-based admixtures with lime were analyzed after 7 leaching cycles. Test results indicated that the normalized specific surface area (SSAN) of 1.05 with CS phases has better moisture susceptible durability and long-term permanency as compared to NS treatment (SSAN of 0.70) or traditional treatment methods. Overall, the paper provides a comprehensive understanding of the durability and permanency aspects of the novel treatment techniques, which may be of enormous benefit to geotechnical and transportation practitioners in enhancing the durability of chemical treatments.