Alkali-activated cementitious materials present an environmentally beneficial and high-performance option in the domain of soil solidification and stabilization. This research focused on granulated blast-furnace slag (GGBFS), a predominant byproduct and solid waste from iron manufacturing that has a limited utilization rate. Due to its high content of calcium (Ca), silicon (Si), and aluminum (Al), slag has emerged as an effective soil curing agent. This study investigated sandy silt by employing alkali-activated slag to examine its solidification and stabilization properties. We assessed the unconfined compressive strength (UCS), deterioration strength, and solidification mechanism of alkali-activated slag-stabilized sandy silt through unconfined compressive strength tests and various microscopic analyses, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FITR), and scanning electron microscopy (SEM). These findings indicate that using slag alone for solidifying sandy silt is inefficient. However, following alkali activation, the UCS of solidified soil with sandy silt generally increases with increasing GGBFS content and initially increases, then decreases with increasing alkali-activator content. The ideal proportions of GGBFS and alkali-activator are between 12 %-14 % and 6 %-9 %, respectively. Upon exposure to ordinary and triple-concentration artificial seawater, the strength of the solidified soil generally diminishes over time. It is worth noting that the strength of the samples in group GGBFS14 exhibited an initial increase, followed by a decrease, as the deterioration time increased. With alkali-activator contents of 6 % and 9 %, the strength and durability of the solidified soil remain relatively stable, maintaining robust mechanical properties even after seawater erosion. The resistance of the solidified soil to seawater deterioration increases as the GGBFS content increases. Microscopic tests revealed the presence of amorphous hydration gel products (C-A-S-H). The optimal GGBFS and alkali-activator contents for sandy silt solidification in this study were determined to be 12 %-14 % and 6 %-9 %, respectively. At these optimal levels, the strength of the solidified soil at a curing age of 28 days can reach 13.49 MPa (GGBFS16AA6). This suggests that alkali-activated slag holds potential as a substitute for ordinary Portland cement (OPC) in engineering applications and offers a strategy for reusing GGBFS.

Using silty clay as roadbed filling can lead to roadbed diseases. In this paper, silty clay was modified with lignin and BFS (GGBS). Then, the mechanical properties, freeze-thaw characteristics, and microscopic mechanisms were investigated using unconfined compression tests, California bearing ratio tests, rebound modulus tests, freeze-thaw cycling tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The results showed that as the curing age increased, the unconfined compressive strength (UCS) of modified silty clay gradually increased, and the relationship between the stress and axial strain of the samples gradually transitioned from strain-softening to strain-hardening. As the lignin content decreased and the BFS content increased, the UCS, California bearing ratio (CBR), and rebound modulus of the modified silty clay first increased and then tended to stabilize. Adding lignin and BFS can effectively resist volume increase and mass loss during freeze-thaw cycles. When the ratio of lignin to BFS was 4%:8%, the growth rate of the UCS, CBR, and rebound modulus was the largest, the change rate in volume and mass and the loss rate of the UCS under the freeze-thaw cycle were the smallest, and the silty clay improvement effect was the most significant. The microscopic experimental results indicated that a large amount of hydrated calcium silicate products effectively increased the strength of interunit connections, filled soil pores, and reduced pore number and size. The research results can further improve the applicability of silty clay in roadbed engineering, protect the environment, and reduce the waste of resources.

Expansive soils pose various problems to the existing transportation infrastructures by causing damages to pavements, railways, and embankments due to differential settlement, and volume changes in soils. Therefore, expansive soil if used in pavements must be stabilized by using some suitable means. The present study investigates the strength and durability of expansive soil stabilized with alkali-activated GGBFS (ground granulated blast furnace slag). In order to accelerate the hydration process, an alkali activator of low molarity (i.e., 5 M NaOH) is used to stabilize the subgrade expansive soil. GGBFS and alkali-activated GGBFS were added in the proportions of 5, 10, 15, 20, 25, and 30% to check the improvement in the strength properties of expansive soils after different periods of curing. The strength properties of stabilized soil were assessed by conducting various laboratory tests like unconfined compressive strength (UCS) and California bearing ratio (CBR). Durability study was also done by subjecting the soil specimens to 12 wet-dry cycles. The utilization potential of alkali activated GGBFS has been assessed from the mechanical, mineralogical, and morphological properties of stabilized soil. It was found that alkali-activated GGBFS can be effectively utilized for highway subgrade and sub-base applications.

In this study, the effects of fly ash and granulated blast furnace slag based geopolymer on the mechanical properties of high plasticity clayey soils were investigated. For this purpose, experimental studies were carried out using the Taguchi Method. The Taguchi L16 orthogonal array was used with various amounts of class F fly ash (12%, 16%, 20%, and 24%), granulated blast furnace slag (8%, 10%, 12%, and 14%), and alkaline hydroxide solution NaOH molarity (6, 8, 10, and 12). After 7 and 28 days of curing, unconfined compressive strength (UCS) and California bearing ratio (CBR) were carried out. Permeability test was carried out as well after 28 days of curing. The effects of the variables on the experimental results were determined using S/N and variance analyses (ANOVA). The microstructure and phase composition of geopolymer samples were identified via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The findings indicate that the strength of geopolymer-stabilized soil is significantly affected by the stabilizer content, fly ash-slag ratio, and molarity of alkaline activator (M). The optimal mix proportions for geopolymer-stabilized high plasticity clayey soil were found to be as follow: 38 % geopolymer content (24 % fly ash, 14 % slag) and an alkaline activator content of 25.75 % with a molarity of 12 M. This study concluded that fly ash and granulated blast furnace slag based geopolymer can serve as a feasible alternative material to cement, being sustainable and applicable. It could be utilized to enhance the strength characteristics of high-plasticity clay soil, while simultaneously, reducing permeability.