Physico-chemical, microstructure, mechanical properties, and mechanism of dispersive saline soil treated with nano-silica sol

Abstract

Rapid disintegration and loss of structural stability characterizes dispersive soils in contact with water and are the cause of many engineering disasters. However, the use of traditional soil chemical additives suffers from environmental pollution, difficulty in sustainability, soil sclerosis and higher alkalinity. Therefore, this paper proposes the use of environmentally friendly materials nano-silica sol to reduce the exchangeable sodium ion (Na⁺) content and cement soil particles in order to modify dispersive soil. Prepare experimental samples by thoroughly mixing nano-silica sol with dispersive saline soil at a mass ratio of 0.5–5 %. Using unconfined compressive strength (UCS) and direct shear test (DST), pinhole and crumb tests, Atterberg and particle size analysis tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) to investigate the mechanical properties, dispersion, physico-chemical properties, and microstructure of the treated soil. Results showed that nano-silica sol can effectively improve the mechanical properties and dispersibility of dispersive saline soil. When the nano-silica sol content was 5 %, the UCS of the treated soil was 416.97 kPa, and the cohesion was 46.03 kPa, compared to 66.97 kPa and 21.29 kPa for untreated soil, the UCS and cohesion increased by 523 % and 116 %. Additionally, at the optimal content of 2.5 %, the pH and Na⁺ concentration of the pore water solution in the treated soil decreased from 8.2 and 8.80 mmol/L in the untreated soil to 7.0 and 6.26 mmol/L, and the soil dispersion completely disappeared. SEM, XRD, and FTIR indicated that the calcium silicate hydrate (C-S-H) generated by the reaction in the treated soil cemented the soil particles. At the same time, when the silica sol content exceeded 2.5 %, a large amount of amorphous silica gel filled the soil pores. Both processes improved the microstructure of the soil and enhanced its mechanical properties. This research provides deeper insights into the application of nano-silica sol in soil improvement and the sustainable management of dispersive saline soils.