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

Abstract

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. The stabilization of noncohesive soils such as marine calcareous sands with lime has been a subject of interest among geotechnical engineers in recent decades. Due to the significant air pollution and high energy consumption associated with lime production, alternative strategies, such as using supplementary materials to partially replace lime, are deemed an attractive approach. In this study, the mechanical behavior of a calcareous sand (obtained from Hormuz Island as a strategic island in the Persian Gulf) stabilized with 4%, 6%, and 8% of hydrated lime and zeolite-to-lime replacement proportions of 0%, 15%, 30%, 45%, 60%, and 75% was evaluated through a series of UCS and UPV tests. Additionally, the influence of wetting and drying cycles on the strength and stiffness characteristics of treated Hormuz Island soil has also been studied; the topic which can be very significant due to the effects of waves and sea tides on the soil and structures of marine regions. Based on the experimental results, replacing lime with zeolite could efficiently improve the mechanical behavior of calcareous sand specimens, specifically when subjected to consecutive wet–dry cycles. In particular, 45% and 30% of zeolite replacement were shown to be the best substitutes for lime after four and eight cycles of wetting and drying, respectively.