Effect of calcium content on geopolymer consolidation of saline soils in the seasonally frozen zone

Geopolymers have long been used to stabilise unique soils, and the stabilising conditions and freeze-thaw cycles (FTs) have a substantial impact on the engineering qualities of stabilised soils. The mechanical characteristics and microstructure of lime (Ca(OH)₂) fly ash (FA) stabilised saline soils were investigated in this study using the Unconfined Compressive Strength (UCS), Splitting Strength, and Residual Strength (I_R) tests in conjunction with X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Thermogravimetry (TG). The results indicated that the mechanical properties were optimal at 3% Ca(OH)₂ with constant 13% FA content and stabilised soils with UCS and splitting strength of 8.78 MPa and 1.43 MPa, respectively. The stabilised soils strength showed a trend of rapid decrease and then stabilisation with increasing FTs, and frost resistance was optimal at 3% Ca(OH)₂. At FTs = 20, the UCS and splitting strength I_R were 40.94% and 32.51%, respectively, which were higher than those of other proportions of stabilised soils. This was attributed to the fact that calcium assisted FA stabilisation was primarily attributed to the formation of dense network structure of hydrated calcium silicate and hydrated calcium aluminate gels, as well as the generation of ettringite with sulphate.