Abstract: To address the issues of low early strength in cement-stabilized soft soil, as well as the high pollution, energy consumption, and costs associated with cement binder application, one-part geopolymer (OPG) is prepared by using solid sodium silicate (Na2O·SiO2, NS) to activate a mixture of binary precursors, namely fly ash (FA) and ground granulated blast furnace slag (GGBFS), along with water. The factors, including FA dosage, solid NS molarity, alkali molar concentration, and water-cement ratio, are considered for assessing the physical and mechanical properties of OPG. Based on this, optimized proportioning tests were conducted to determine the best mixing ratio of OPG for soft soil stabilization. The effects of the FA/GGBFS ratio in the precursor and curing ages on the unconfined compressive strength (UCS), porosity, and pore size distribution of OPG-stabilized soft soil were further investigated. Micro-analysis was performed using mercury intrusion porosimetry (MIP), scanning electron microscope-energy dispersive spectrometer (SEM-EDS) to reveal the stabilization mechanism. The results indicated that the OPG prepared with solid NS could effectively stabilize soft soil, with hydrated gels (N-A-S-H, C-A-H, C-S-H, and C-A-S-H) effectively bonding soil particles and contributing to the formation of a denser soil skeleton. The mixing proportion of FA/GGBFS of 0.1, water-cement ratio of 0.8, NS molarity of 1.0, and molar concentration of 3 mol/L was found to be optimal for soft soil stabilization. The corresponding OPG had good workability and achieved a UCS of 4.4 MPa. This study extends the application of solid sodium silicate-inspired one-step geopolymers in deep mixing techniques, providing guidance on the theoretical basis for the reinforcement treatment of soft ground foundations.

Key words: solid sodium silicate, one-part geopolymer, micro-analysis, unconfined compressive strength, curing mechanism