Water stability mechanism of silicification grouted loess

Silicification is one of the chemical stabilisation methods used in the treatment of collapsible loess soils. The water stability therein is a key parameter in the silicification of grouted loess. Based on slaking tests, permeability measurement, X-ray diffraction spectra, X-ray energy dispersive spectroscopy, and scanning electron microscopy, the water stability mechanism inherent in the CO2-silicification grouted loess was investigated. Samples of original, compacted, and CO2-silicification grouted loess in 30 days curing were tested. To assess the long-term water stability, CO2-silicification grouted loess samples in 13, 19, and 24 years of curing were analysed. The study showed that the CO2-silicification grouted loess had good water erosion resistance, no disintegration, and good water stability over time. The water stability of CO2-silicification grouted loess depended on the strong bond strength of the grains and a low permeability. The complex physicochemical reactions among CO2, water, alkali earth metal salts, clay minerals, and organic matter in loess produced hydrate calcium (and magnesium) silicate gels, which were mainly coated on the surface of the soil skeleton grains and original cements. A few filled in the trellis pores. The gels coated on the soil skeleton limit the hydrophilicity of clay minerals and organic matter and improve water resistance, and if coated on original cements reinforce bond strength, consequently, the water stability of CO2-silicification grouted loess was improved.