Influence of hemp fiber on the mechanical characteristics and freeze-thaw durability of LKD-nano silica-stabilized kaolin soil

This study deals with assessing the incorporation of lime kiln dust (LKD), nano-silica (NS), and hemp fibres (HF) as sustainable reinforcement materials for soil stabilization in civil engineering applications. Unlike conventional stabilizers, LKD, NS, and HF introduce a natural and environmentally friendly alternative. These additives enhance soil strength while reducing reliance on cement-based binders. For this purpose, unconfined compressive strength (UCS) tests were conducted on kaolin soil with varying amounts of LKD (4%, 6%, and 8%). UCS tests were also performed after 3, 7, and 28 days of curing. The results showed that a concentration of 6% LKD was best, which raised the compressive strength to 1680.16 kPa after 28 days of curing. Then, four amounts of NS (5, 10, 15, and 20%) were replaced with the optimal content of LKD. After 28 days of curing, the UCS test results showed that the incorporation of 6% LKD and 10% NS into kaolin soil elevated the compressive strength from 302.46 kPa to 1899.96 kPa. After finding the optimal mixture, 0.2%, 0.4%, and 0.6% HF were added to these mixtures. The stabilized-reinforced kaolin soil was subsequently subjected to UCS, indirect tensile strength (ITS), Freeze-thaw (F-T) cycles, ultrasonic pulse velocity (UPV), X-ray diffraction (XRD), scanning electron microscopy analysis (SEM), and Fourier transform infrared spectroscopy (FTIR). The findings indicated that the inclusion of 6% LKD, 10% NS, and HF improved the compressive strength and the greatest enhancement of UCS, UPV, and ITS was seen in the samples reinforced with 0.4% HF after 28 days. The UCS, UPV, and ITS tests without F-T cycles, respectively were 1979.68 kPa, 691.68 m/sec, and 502.12 kPa for stabilized-reinforced kaolin soil. Microscopic analysis confirmed enhanced performance, particularly in freeze-thaw (F-T) cycles, with HF-stabilized soil outperforming LKD-NS-stabilized soil. SEM analysis revealed the formation of calcium silicate hydrate (C-S-H) gels, strengthening the soil structure, while XRD confirmed the presence of crystalline phases like calcite and calcium hydroxide, indicating hydration and a cementitious matrix. According to the results, LKD, NS, and HF act well to make soil much more cohesive, flexible, and long-lasting. This study underscores hemp fiber’s potential as an eco-friendly soil reinforcement, contributing to sustainable geotechnical engineering solutions.