Mechanical and Shrinkage Properties of Alkali-Activated Binder-Stabilized Expansive Soils

Expansive soil is prone to significant swelling and shrinkage deformation with changes in moisture conditions, posing serious safety hazards to engineering construction. This study focuses on alkali-activated self-compacting fluid-solidified soil (ASFS) and systematically explores the regulatory effect of expansive soil with different dosages (0–100%) on its properties. This study analyzes the influence of expansive soil on the setting time, hydration characteristics, autogenous shrinkage, and compressive strength of ASFS while verifying the feasibility of this method for solidifying expansive soil through microstructural analysis. The results show that, with the increase in content of expansive soil, the initial and final setting times of ASFS were prolonged by 0.08–1.58 times and 0.08–1.29 times, respectively. Although expansive soil inhibited the hydration of ASFS, it could compensate for autogenous shrinkage through the expansion effect of clay minerals, reducing the autogenous shrinkage by 13.4–51.2%. Furthermore, the optimal dosage of expansive soil in ASFS is 60%. Compared with the control group, the 7d compressive strength of ASFS increases by 52.4%, the strength after 3d water immersion rises by 62.6%, and the strength after eight wet–dry cycles still remains 10% higher. This optimal dosage achieves the best balance between mechanical properties, water stability, and shrinkage resistance of ASFS, providing a reliable technical reference for the efficient utilization of expansive soil in engineering.