To enhance the shear strength of soil, geopolymers were prepared using quicklime as the alkaline activator and used to solidify the soil. The influence laws of the dosage of quicklime, the mass ratio of blast furnace slag to fly ash, the dosage of solidifying agent, and the curing age on the shear strength of geopolymer-solidified soil were studied through direct shear tests. The microstructure of the soil was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the dosage of quicklime has a significant threshold effect on the shear strength of geopolymer solidified soil. When the dosage of quicklime is 10%, the shear strength of the soil reaches the peak. With the increase of the mass ratio of blast furnace slag to fly ash, the shear strength of the soil gradually increases. With the increase of the dosage of the curing agent and the extension of the curing age, the cohesion and shear strength of the soil gradually increase, and the internal friction angle shows a changing trend of first increasing and then tending to stabilize. Adding an appropriate amount of quicklime can promote the polycondensation reaction, generating a large amount of C-A-S-H gel, thereby improving the soil structure and enhancing the soil strength. The research results can provide a reference for the application of quicklime-activated geopolymer solidified soil.
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