This research explores the stabilization of clay soil through the application of geopolymer binder derived from silicomanganese slag (SiMnS) and activated by sodium hydroxide (NaOH). This research aims to evaluate the effects of key parameters, including the percentage of slag, the activator-to-stabilizer ratio, and curing conditions (time and temperature), on the mechanical properties of the stabilized soil. Unconfined compressive strength (UCS) tests were conducted to assess improvements in soil strength, while scanning electron microscopy (SEM) was employed to analyze the microstructural changes and stabilization mechanisms. The results demonstrated that clay soil stabilized with SiMnS-based geopolymers exhibited significant strength enhancement. Specifically, the sample stabilized with 20% SiMnS and an activator-to-slag ratio of 1.6, cured at room temperature for 90 days, achieved a UCS of 27.03 kg & frasl;cm2. The uniaxial strength was found to be positively correlated with the SiMnS content, activator ratio, curing time, and temperature. Additionally, the strain at failure remained below 1.5% for all samples, indicating a marked improvement in soil stiffness. SEM analysis revealed that geopolymerization led to the formation of a dense matrix, enhancing soil particle bonding and overall durability. These results emphasize the potential of SiMnS-based geopolymers as a sustainable and effective soil stabilizer for geotechnical applications.

The freeze-thaw damage of cementitious coarse grained fillings (CCGFs) significantly affects the firmness, stability, and durability of high-speed railway subgrades. It is favorable to employ geopolymer binders to improve the engineering performance of coarse grained fillings (CGFs), further ensure the safety of high-speed railway subgrades in cold regions due to their excellent mechanical and environmental-friendly performances. This study conducted a series of freeze-thaw and mechanical tests on geopolymer stabilized coarse grained fillings (GSCGFs). The influence of gradation, compaction degree, and freeze-thaw cycles on the integrity, strength, and stiffness of GSCGFs was investigated. The evolution law of their freeze-thaw damage was discussed quantitatively based on an improved damage factor. The results show that the mass loss rate of Group B GSCGFs with a fine-grained particle content of less than 15% was lower than that of Group A GSCGFs with a fine particle content between 15% and 30% overall. When other conditions remain unchanged, the mass loss rate of GSCGFs decreased with the increase of compaction degree but increased nonlinearly with the freeze-thaw cycles. The strength and stiffness of GSCGFs decrease nonlinearly with the freeze-thaw cycles and presented a first fast and then slow-down change trend, their stiffness evolution at different compaction degrees revealed a big difference due to the weakening bite effect and enhancing overhead structure among rock blocks. The strength reduction of Group A GSCGFs was less than that of Group B under the high compaction degree. The stiffness deterioration of Group A GSCGFs was about twice that of Group B. There seemed to be no absolute correlation that the strength of GSCGFs was positively correlated with their stiffness. By building an exponential relationship between the compressive strength of GSCGFs and the freeze-thaw cycles that followed the findings of previous several studies, an improved exponential damage evaluation model was proposed to represent the performance degradation of GSCGFs. The outcomes of this study can provide theoretical support for understanding the physical and mechanical behaviors of GSCGFs and applying them in engineering practices.

In cold regions, the soil temperature gradient and depth of frost penetration can significantly affect roadway performance because of frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil index properties, temperature, and availability of water. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous flow of water from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration toward the freezing front, where ice nucleates, coalesces into lenses, and grows. This study evaluates the frost heave potential of frost-susceptible soils from Iowa (IA-PC) and North Carolina (NC-BO) under different temperature gradients. One-dimensional frost heave tests were conducted with a free water supply under three different temperature gradients of 0.26 degrees C/cm, 0.52 degrees C/cm, and 0.78 degrees C/cm. Time-dependent measurements of frost penetration, water intake, and frost heave were carried out. Results of the study suggested that frost heave and water intake are functions of the temperature gradient within the soil. A lower temperature gradient of 0.26 degrees C/cm leads to the maximum total heave of 18.28 mm (IA-PC) and 38.27 mm (NC-BO) for extended periods of freezing. The maximum frost penetration rate of 16.47 mm/hour was observed for a higher temperature gradient of 0.78 degrees C/cm and soil with higher thermal diffusivity of 0.684 mm(2)/s. The results of this study can be used to validate numerical models and develop engineered solutions that prevent frost damage.

Soil stabilization using polymers and fibers has been widely investigated in recent years. This study introduces an innovative approach by integrating synthetic polymer (AH polymer) with natural fibers (sisal fiber) for sand stabilization. A comprehensive experimental framework was established to assess the impact of varying polymer content (1%, 2%, 3%, and 4%) and fiber content (0.2%, 0.4%, 0.6%, and 0.8%, by the mass of dry sand), and densities, on the mechanical properties of stabilized sand, including compressive strength (UCS), tensile strength (TS), and flexural strength (FS). The synergistic stabilization effects of the polymer and fibers were elucidated through SEM. The findings indicate that the synergistic application of AH polymer and sisal fibers significantly enhances the structural integrity of sand. Notably, the UCS, TS, and FS exhibited a well-linear relationship with both the polymer and fiber content. The strengthening effect of fiber was particularly pronounced in samples with higher polymer content. According to the strength increase rate, the optimal polymer content is 2%, and optimal fiber content is 0.6% for the UCS, 0.4% for the TS and 0.8% for the FS. An increase in density was observed to linearly augment the UCS and FS. For sand with 2% polymer and 0.8% fiber, the TS increased linearly with the increment in density, however, for sand with 4% polymer and 0.4% fiber, TS kept a non-monotonic relationship with density. The study also revealed that augmenting the content of polymer and fibers diminishes the brittleness of the stabilized sand, whereas an increase in density has the opposite effect. Furthermore, the incorporation of polymer and fibers resulted in an elevated deformation modulus. The polymer functions as an adhesive, binding fibers to sand particles, while the fibers create a network-like structure that amplifies the effective contact area among sand particles, thereby substantially improving the mechanical properties of the sand.