Laboratory Study on Stiffness and Strength of Cement Stabilized Clay Subjected to Four-Season Durability Cycles

The Unified Facilities Criteria (UFC) 3-250-11 is a widely recognized standard among United States government agencies for providing guidelines on soil stabilization in pavement construction, including applications for aircraft and heavy military vehicles. To assess long-term strength degradation due to environmental stressors, the UFC 3-250-11 mandates wetting-drying and freezing-thawing durability cycles for the design of cement-stabilized soils. However, a limitation of this standard is that the prescribed methodologies, derived from the American Standard for Testing and Materials (ASTM), may not fully represent the conditions experienced in regions with all four seasons, such as the midwestern United States. This research addresses this limitation in adjacent with the ongoing need to investigate carbon-friendly stabilizers for soil such as Portland Limestone Cement (PLC). This study examines the effects of combined wetting-drying-freezing-thawing (WDFT) and freezing-thawing-wetting-drying (FTWD) environmental stressors on the engineering properties of cement-treated soil stabilized with Ordinary Portland Cement (OPC) Type I and PLC. A low plasticity clay (CL) soil was treated with both OPC and PLC at an 11% dosage under modified Proctor compaction conditions. Following a seven-day curing period, durability studies were conducted. WDFT and FTWD durability methods were developed by integrating the wetting-drying and freezing-thawing conditions as specified by UFC 3-250-11 for a total of 10 cycles. Post-durability engineering tests included repeated load triaxial testing to determine the resilient modulus and unconfined compressive strength (UCS) tests. Results indicated that durability cycles caused an increase in specimen volume for both stabilizers. Engineering tests showed reductions in stiffness and strength as durability cycles progressed. Specifically, repeated load triaxial testing and unconfined compressive strength results demonstrated reduced stiffness and strength, respectively, for all cement-treated specimens. Notably, PLC-treated specimens exhibited lower stiffness and strength compared to OPC-treated specimens. The findings suggest that while PLC warrants a promising alternative to OPC, its resistance to environmental degradation under four season durability conditions warrants further investigation into its suitability as a soil stabilizer as it may not be as durable as OPC.