In this study, ground granulated blast-furnace slag (GGBS) and fly ash (FA) were used as binders, while NaOH (NH) and Na2SiO3 (NS) served as alkali activators. Seawater (SW) was used instead of freshwater (FW) to develop a SW-GGBS-FA geopolymer for solidifying sandy soils. Geopolymer mortar specimens were tested for unconfined compressive strength (UCS) after being curing at room temperature. The results showed that the early strength of the seawater group specimens increased slowly less than that of the freshwater group specimens, while the late strength was 1.16 times higher than that of the freshwater group specimens. Factors including seawater salinity (SS), the GGBS/FA ratio, curing agent (CA) content, and the NH/ NS ratio were examined in this experiment. The results showed that the strength of the specimens was higher for SS of 1.2 %, G90:F10, CA content of 15 %, activator content was 15 %, and NH: NS of 50:50. The pore structure of the mortar specimens was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and computerized tomography (CT), revealing the mechanisms by which various factors influenced the microstructure. XRD indicated that SW-GGBS-FA geopolymer mortar newly produced Friedel salt and calcium silicate sulfate hydrate (C-S-S-H). The microstructures observed by CT and SEM showed that the pore radius of the seawater specimens was mainly less than 10 mu m, and the maximum crack length was 92.55 mu m. The pore radius of freshwater specimens was larger than that of seawater specimens, and the largest crack was 148.44 mu m, which confirmed that Friedel salt and C-S-S-H fill the pores and increase the UCS of the specimens.

This study developed all-solid-waste-based curing agents using industrial solid wastes-ground granulated blastfurnace slag (GGBS), carbide slag (CS), and sulfate solid wastes (electrolytic manganese residue (EMR), desulfurized-gypsum (DG), and phosphogypsum (PG))-to stabilize engineering sediment waste (ESW). Based on the simplex centroid design, three ternary curing agents (GGBS-EMR-CS (GEC), GGBS-DG-CS (GDC), and GGBSPG-CS (GPC)) were prepared. The optimal ratios for GEC, GDC, and GPC are 60:12:28, 70:27:3, and 70:21:9, respectively. Compared to ordinary Portland cement (OPC), the unconfined compressive strength (UCS) of ESW stabilized with these curing agents increased by 78 %, 178 %, and 98 %, respectively. Sulfate components synergistically activates GGBS and CS, promoting needle-like ettringite (AFt) formation, which fills pores and enhances strength. Meanwhile, COQ emissions and costs were reduced up to 99 % and 73 %, respectively. This study developed all-solid-waste-based curing agents with excellent mechanical performance, low costs, and near net-zero emissions, which provided a sustainable solution for ESW stabilization.

Four polyacrylate materials with different mass ratios of soft and rigid segment were made by semi-continuous pre-emulsified seed emulsion polymerization. Methyl methacrylate (MMA) and butyl acrylate (BA) were used as soft and rigid segments, and acrylic acid (AA) was used as the functional segment. The composite emulsifiers were composed of sodium dodecyl sulfate (SDS) and alkylphenol polyoxyethylene ether (OP-10). In this study, we successfully fabricated polyacrylate (PA). The morphology of the latex particles was spherical, with a diameter of similar to 200 nm. With the increase of BA content, the glass transition temperature (T g ) of PA decreased. The PA curing agent could significantly improve the soil's mechanical property and water resistance. The compressive strength of PA-1 solidified soil increased to 2.67 MPa, which 187 % higher than the pure soil sample (PA-0). Meanwhile, PA-1 solidified soil would not break down after being immersed in water for 30 days. This indicated that PA emulsion had an efficient solidification ability and a good water resistance, which was beneficial to sand fixation and slope protection.

Pre-mixed fluidized solidified soil (PFSS) has the advantages of pumpability, convenient construction, and a short setting time. This paper took the excavated loess in Fuzhou as the research object and used cement-fly-ash-ground granulated blast furnace slag-carbide slag as a composite geopolymer system (CFGC) to synthesize PFSS. This study investigated the fluidity and mechanical strength of PFSS under different water-solid ratios and curing agent dosages; finally, the microstructure of the composite geopolymer system-pre-mixed fluidized solidified soil (CFGC-PFSS) was characterized. The results showed that when the water-solid ratio of PFSS increased from 0.46 to 0.54, the fluidity increased by 77 mm, and the flexural strength and compressive strength at 28 d decreased to 450.8 kPa and 1236.5 kPa. When the curing agent dosage increased from 15% to 25%, the fluidity increased by 18.0 mm, and the flexural strength and compressive strength at 28 d increased by 1.7 times and 1.6 times. A large number of needle-like AFt, C-S-H gel, and C-(A)-S-H gel coagulate with soil particles to form a three-dimensional reticular structure, which is the mechanism of the strength formation of PFSS under the action of CFGC.

Guided by the solidification of loess contaminated with heavy metal ions (HMs), a natural inorganic diatomite (NID) was developed as curing agent under an alkaline activator (AA). The curing time, NID content and AA type on the mechanical properties of contaminated soil and solidification effect of HMs were investigated. The solidification source was analysed by microstructure measurement. As curing time increased, the solidification effect increased, with an optimum curing time of 28 days. The higher the content of NID, the stronger the solidification ability. Nevertheless, the strength showed a tendency of initial increase and subsequent decrease. The strength was maximum when NID content reached 10%. The AA created an alkaline environment to promote solidification. In comparison to Na2SiO3 solution, NaOH solution is more effective in the adsorption of HMs. The larger ionic radius of Pb2+ relative to Cu2+, limited HMs migration ability, thereby facilitating solidification.

The utilization of high-quality curing agents to improve loess filler can not only use local materials to cut down the project cost, but also diminishes the amount of traditional binders such as lime and cement, which is of great significance for carbon reduction. In order to explore the mechanical properties and durability of composite improved loess using CG-2 curing agent and cement, a series of tests are conducted, including triaxial shear tests, unconfined compressive strength (UCS) tests, freeze-thaw cycle tests, and water stability tests. Furthermore, the microscopic pore structure of the composite improved loess is studied by SEM NMR and XRD tests. The findings indicate that the maximum dry density and optimal water content of the composite improved loess show a trend of increasing first and then decreasing with the increase of cement and curing agent dosage (DCA), and the maximum value is obtained when a cement dosage is 6 % and a DCA of 0.020 %. The shear strength and UCS of the composite improved loess are significantly higher than those of the cement improved loess (CIL), and the greater the amount of curing agent, the higher the strength. On the premise of reaching the same strength standard, the addition of curing agent can significantly reduce the amount of cement. With the increase of the DCA and cement dosage, the durability of composite improved loess is significantly improved than that of the CIL. The addition of curing agent can also reduce the spacing of mineral crystal planes of the composite improved loess, enhance the cementation characteristics of soil particles, change the contact mode between particles, and then improve the physical and mechanical properties of the improved soil. It is recommended to use a cement dosage of 6 % and a DCA of 0.020 % for the improvement of loess filling materials of secondary and below highway base, which can achieve the optimal improvement effect.

The disposal of tailings has always been a focal point in the mining industry. Semi-dry tailings stockpiling, specifically high-concentration tailings stockpiling, has emerged as a potential solution. To enhance the stability of tailings stockpiling and minimize its costs, the incorporation of a low-cost curing agent into high-concentration tailings is essential. Therefore, this study focuses on the development of a curing agent for high-concentration unclassified tailings stockpiling. The composition of a low-cost curing agent system is determined based on theoretical analysis, and the curing reaction mechanisms of each composition are researched. Subsequently, an orthogonal experiment is designed, and the strength of the modified unclassified tailings solidified samples at different curing ages is measured. Furthermore, the rheological properties of the modified unclassified tailings slurries are tested, and the feasibility of industrial transportation of the unclassified tailings slurries modified with the optimized curing agent is analyzed. Lastly, the microscopic morphologies of each material and the modified unclassified tailings solidified samples are characterized, their chemical compositions are tested, and the action mechanism of the curing agent in the curing system is further investigated. The results show that the optimal proportions of each material in the curing agent are as follows: slag, 58%; quicklime, 15%; cement, 8%; gypsum, 9%; and bentonite, 10%. The dominance of industrial waste slag exceeding 50% reflects the low-cost nature of the curing agent. Under this condition, the modified unclassified tailings slurry with a mass concentration of 75% exhibited a yield stress of 43.62 Pa and a viscosity coefficient of 0.67 Pas, which is suitable for pipeline transportation. These findings lay a foundation for subsequent decisions regarding stockpiling processes and equipment selection.

Cement-stabilized soil is a commonly used pavement base/bottom base material. Adding a suitable curing agent to cement-stabilized soil can effectively reduce the dosage of cement, meet the strength requirements, and also greatly improve its water stability. In this paper, three kinds of cement dosage (6%, 8%, and 10%) of cement-stabilized soil were selected to add a 0.04% organic liquid curing agent, and then compared with high-dose cement (10% and 12%)-stabilized soil. The influence of wetting-drying cycles on the mechanical properties of the five stabilized soils was discussed. The mineral composition of cement-stabilized soils before and after the addition of a curing agent was analyzed by X-ray diffraction (XRD), and the microscopic morphology of 10% cement-stabilized soils with a curing agent was studied by scanning electron microscopy (SEM). The macroscopic test shows that the unconfined compressive strength of solidified cement-stabilized soil can be divided into three stages with the increase in the times of the wetting-drying cycles, which are the rapid decay stage, stable enhancement stage, and stable decay stage. The wetting-drying stability coefficient first increases, and then decreases with the increase in the times of the wetting-drying cycles. The microscopic test shows that the addition of a curing agent can enhance the content of hydration products in the cement-stabilized soil specimen; at the curing age of 28 d, with the increase in the times of the wet-dry cycles, the structure of the solidified cement-stabilized soil gradually broke down. The surface porosity P and pore diameter d showed an overall upward trend but decreased at the fifth wetting-drying cycle. The pore orientation weakened. The results show that the resistance of cement-stabilized soil with a curing agent is obviously better than that of cement-stabilized soil under wet-dry conditions.

In order to study the improvement effect of the CG-2 curing agent and cement on loess, a series of physical and mechanical property tests and microstructure tests were carried out on loess improved with different dosages of curing agent and cement to study the physical and mechanical properties, durability and microscopic pore characteristics of the CG-2 curing agent and cement-improved loess. The results show that the unconfined compressive strength of improved loess increases gradually with the increase in curing agent and cement dosage, and the higher the compaction degree and the longer the curing age, the higher the unconfined compressive strength. In the case of the same cement content, the higher the dosage of curing agent, the more the unconfined compressive strength of improved loess increases. Under the condition of reaching the same unconfined compressive strength, the addition of curing agent can significantly reduce the amount of cement. The more the content of cement and curing agent, the less the unconfined compressive strength decreases after a certain number of freeze-thaw cycles, and the higher the dry-wet cycles index after a certain number of dry-wet cycles, indicating that the addition of curing agent can significantly improve the ability of the sample to resist freeze-thaw cycles and dry-wet cycles. According to the microscopic test results, it is found that the addition of curing agent can reduce the porosity of soil particles, change the contact and arrangement mode between soil particles, and enhance the agglomeration and cementation characteristics between soil particles, and obviously improve the physical and mechanical properties of soil. The research results can provide new ideas and methods for the improvement technology of loess.