Clayey sand soils require improvement in civil engineering projects due to their low density, high porosity, and inadequate shear behavior. On the other hand, the extensive use of cement in soil stabilization is associated with environmental concerns such as high COQ emissions. In this study, the effect of partial replacement of cement with zeolite (up to 50 %) and the addition of polyvinyl alcohol (PVA) fibers (up to 0.8 wt%) on improving the mechanical, microstructural and environmental properties of clayey sand soil was investigated. Samples were prepared with different cement contents (3 and 6 %) and, after 7 and 28 days of curing, were subjected to compaction, unconfined compressive strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity (UPV), scanning electron microscope (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and toxicity characteristic leaching procedure (TCLP) tests. The compaction test results showed that maximum dry density (MDD) decreases and optimum moisture content (OMC) increases with increasing zeolite content. The performance of different mixtures showed that the optimum mixture consisted of 6 % cement, 20 % zeolite, and 0.8 % fibers, which increased UCS, ITS, and UPV by 320 %, 194 %, and 35 %, respectively, compared to unstabilized soil. Micro-structural analyses showed the formation of CSH and CAH gels and improved interfacial transition zone bonds. Also, TCLP results showed that zeolite reduced heavy metal leaching. This study, with an innovative approach, investigated the simultaneous effectiveness of zeolite, cement, and fibers and introduced the potential of the UPV method as a non-destructive method for evaluating the mechanical performance of stabilized soil.

This study presents the results of consolidated drained triaxial tests conducted to investigate the influence of various parameters on the volumetric change behavior of cemented sand reinforced with polyvinyl alcohol (PVA) fibers. The primary objective is to explore the interaction between fiber weight ratio, cement weight ratio, confining pressure, and relative density on the dilatation behavior of cemented sand reinforced with PVA fibers. PVA fibers were incorporated into dry sand-cement mixtures at weight ratios of 0.0%, 0.3%, and 0.6%. The specimens were prepared with cement content of 0%, 2%, and 4% by weight of dry sand and cured for 7 days. Two relative densities were used in specimen preparation, and triaxial compression tests were conducted under different confining pressures. The results reveal that decreasing relative density, increasing cement content, and adding fibers all contribute to a reduction in sample dilatation. Specifically, the peak dilation rate increases with higher relative density and cement content, while it decreases with higher fiber content and confining pressure. A notable aspect of this study is its investigation of how these parameters interact when combined, offering a deeper understanding of their collective effects on soil behavior.

Adding cement to soft soils may lead to brittle behavior and the occurrence of sudden damage. Methods to further improve the tensile and flexural properties of cemented clay are noteworthy topics. This paper mainly focuses on the effect of cement and moisture content on the strength and flexural properties of cemented clay reinforced by PVA fiber. The selected clayey soil was a kaolin with cement content of 5%, 10%, and 15% and moisture content of 50%, 56%, 63%, and 70%. The results show that the incorporation of 0.6% fiber can effectively improve the deformability of cemented clay in unconfined compression tests (UCS). The strengthening effect of fiber, as seen in the peak strength and post-peak strength of UCS, was significantly related to cement content. As the water content increased, the compressive strength of the fiber-reinforced cemented clay decreased, but its load-bearing capacity enhanced. When the cement content was 15%, the splitting tensile strength of fiber-reinforced cemented specimens increased by 11% compared to cemented soil, but the deformability of the specimens became poor. In the cement-content interval from 5% to 10%, the bending toughness was significantly improved. Sufficient cement addition ensures the enhancement of PVA fibers on strength and flexural properties of cement-stabilized clayey soil.