Sustainable soil stabilization with Nano-Silica and polypropylene fibers mechanical properties durability and microstructural analysis.

Improving soil stability is essential for geotechnical applications, yet conventional stabilizers like cement and lime often pose serious environmental challenges. This study investigates the synergistic effects of polypropylene fibers and nano-silica on soil unconfined compressive strength (UCS) and durability against dry-wet and freeze-thaw cycles. Then, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) were used to investigate microstructural behavior of treated soil. Results reveal that nano-silica and fibers exhibited synergistic effects, achieving peak UCS value of 923.1 kPa at 2% content nano-silica associated with 2% content polypropylene fibers treated soil. The fiber improvement ratio consistently outperforms the nano-silica improvement ratio, suggesting that polypropylene fibers provide a greater contribution to soil strength enhancement in the mixture. Furthermore, soil treated with 2% nano-silica and 2% polypropylene fiber exhibited significantly lower deterioration across all cycles, demonstrating enhanced resistance to both dry-wet and freeze-thaw processes. The reduction in T2 curve peaks of NMR revealed that the addition of both polypropylene fibers and nano-silica reduced soil porosity and refined the soil pore structure, with nano-silica demonstrating superior efficacy in these aspects relative to polypropylene fibers. SEM analysis revealed that nano-silica fills soil pores and binds to particle surfaces, while fibers form a three-dimensional network, collectively enhancing soil compaction and structural integrity.