Effects of Nano-SiO2 and Nano-CaCO3 on Mechanical Properties and Microstructure of Cement-Based Soil Stabilizer

Soil stabilizers are environmentally friendly engineering materials that enable efficient utilization of local soil-water resources. The application of nano-modified stabilizers to reinforce loess can effectively enhance the microscopic interfacial structure and improve the macroscopic mechanical properties of soil. This study employed nano-SiO2 and nano-CaCO3 to modify cement-based soil stabilizers, investigating the enhancement mechanisms of nanomaterials on stabilizer performance through compressive and flexural strength tests combined with microscopic analyses, including SEM, XRD, and FT-IR. The key findings are as follows: (1) Comparative analysis of mortar specimen strength under identical conditions revealed that nano-SiO2 generally demonstrated superior mechanical enhancement compared to nano-CaCO3 across various curing ages (1-3% dosage). At 1% dosage, the compressive strength of both modified stabilizers increased with curing duration. Early-stage strength differences (3 days) remained below 3% but showed a significant divergence with prolonged curing: nano-SiO2 groups exhibited 10.3%, 11.3%, and 7.2% higher compressive strengths than nano-CaCO3 at 7, 14, and 28 days, respectively. (2) The strength enhancement effect of nano-SiO2 on MBER soil stabilizer followed a parabolic trend within 1-3% dosage range, peaking at 2.5% with over 15% strength improvement. (3) The exceptional performance of nano-SiO2 originates from its high reactivity and ultrafine particle characteristics, which induce nano-catalytic hydration effects and demonstrate strong pozzolanic activity. These properties accelerate hydration processes while promoting the formation of interlocking C-S-H gels and hexagonal prismatic AFt crystals, ultimately creating a robust three-dimensional network that optimizes interfacial structure and significantly enhances strength characteristics across curing periods. These findings provide scientific support for the performance optimization of soil stabilizers and their sustainable applications in eco-construction practices.