Effects of Hydrated Lime and Zeolite on the Mechanical Behavior of Calcareous Sand Subjected to Wet–Dry Cycles

The low bearing capacity and high erosion potential of calcareous soils are major concerns in marine environments. Lime stabilization is one of the earliest and most widely used methods for improving the mechanical properties of these weak deposits. Nonetheless, the significant amount of air pollution and high energy consumption associated with lime production have led researchers to the exploration of alternative strategies, such as the utilization of supplementary materials to partially replace lime in the stabilization process. In this study, the mechanical behavior of calcareous sand specimens stabilized with 4%, 6%, and 8% of hydrated lime and zeolite-to-lime replacement proportions of 0%, 15%, 30%, 45%, 60%, and 75% was examined through a comprehensive set of unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests. The specimens were also subjected to consecutive wetting and drying cycles so that the effects of hydrated lime and zeolite proportions on the durability characteristics of treated calcareous sands were discussed. Results indicated that, in all lime contents, the UCS and constrained modulus (D) of treated samples reached their peak values when lime was substituted with zeolite at an optimum percentage of 60%. Additionally, it was observed that after four and eight wet–dry cycles, the optimum zeolite replacement ratio decreased to 45% and 30%, respectively. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests were also conducted to achieve a better understanding of the microstructural changes in calcareous sands due to the stabilization with hydrated lime and zeolite.