Mechanical properties of loess subgrade treated by superabsorbent polymer

Moisture variation is one of the crucial factors affecting the strength and deformation of loess. In this study, superabsorbent polymer (SAP) was introduced as moisture regulator to enhance the ability of accommodating moisture variations of loess and then to improve the stability of loess subgrade. Water migration test was first performed to evaluate the variation law of the effect of SAP on the moisture content of loess in a closed system. Then mechanical tests were carried out to investigate the influence of SAP on the mechanical properties of loess. Besides, microscopic tests were conducted to find out chemical and physical behavior of SAP on the loess. Test results demonstrated that SAP can significantly reduce the water content of loess by 8.26–26.42 %. The unconfined compressive strength (UCS) of loess increased by 37 % after 14 days curing with an optimum SAP content of 1 %, reaching 100 kPa. The dynamic resilient modulus (MR) gradually decreased as a result of SAP addition. The dissipated energy and damping ratio of loess reached the maximum values (100 mJ and 5 %, respectively) at 1.0 % SAP content, which were 10 times and 5 times higher than that of pure loess, respectively. The treatment of loess by SAP was mainly caused by the coupling of physical and chemical water absorption of SAP in the water environment. The incorporation of SAP had no effect on chemical functional groups and mineral composition of loess, but caused water redistribution, thereby changing the mechanical properties.