Experimental Study on Moisture Susceptibility of Subgrade Soil with Superabsorbent Polymers

In this study, superabsorbent polymers (SAP) were introduced as an admixture in subgrade soils for the potential of improving their moisture susceptibility under moisture variation conditions. A series of experiments was performed on the soil samples to investigate the feasibility and influences of SAP on their fundamental physical properties and mechanical performance. In addition, wetting-drying (W-D) cyclic tests were conducted on the samples to simulate the moisture varying conditions that subgrade soils could experience in service. Compaction tests showed that SAP decreased the maximum dry density, but had no effect on the optimum moisture content. Soil amended by SAP exhibited superior uniformities in moisture distribution and grain size distribution. SAP helped enhance the direct shear behaviors of subgrade soils and increased the cohesive strengths and internal friction angles. The W-D cycles obviously degraded the mechanical properties. During the W-D cycles, SAP could also remarkably improve shear strength and the larger the SAP content, the better the shear performance. Results proved that a proper content of SAP (<= 0.75%) added in the subgrade soils had no apparent impact on the volume stability, however a high content of SAP could significantly increase the volume by as much as 12.35%. Based on the test results, an optimal SAP content of no more than 0.75% is recommended. (c) 2019 American Society of Civil Engineers.