Over the past few years, soil‐cement has been widely used in marine geotechnical engineering; meanwhile, the safety of soil‐cement in marine environment has attracted wide attention. In order to study the influence of composite ferronickel slag powder on the strength and micro morphology of soil‐cement in marine environment, the composite nickel iron slag powder was added into the soil‐cement in this paper. The unconfined compressive strength test, erosion resistance coefficient analysis, SEM, and EDS test analysis of soil‐cement were carried out.. Results showed that the marine environment had great influences on the strength of soil‐cement, and the addition of compound nickel‐iron slag powder can enhance the strength of soil‐cement, and the deterioration of the strength of soil‐cement is reduced. In addition, the compound ferronickel slag powder has microaggregate effect, morphological effect, and activation effect, which not only improves compaction rate of soil‐cement and prevents invasion of erosive ions in marine environment but also has positive effects on the performance of soil‐cement.

In coastal areas, structures such as cement-soil dams are often eroded by seawater, so it is significant to study how to improve the impermeability of cement-soil. Basalt fiber with a strong tensile property, good stability and a high-performance price ratio was selected as the additive to study the influence of the basalt fiber content on the permeability of soil-cement. The permeability test and the chloride ion permeability test were used to evaluate the best mixing amount. The results of the permeability test showed that, although the permeability coefficient of soil-cement decreased with the increase in the basalt fiber content, the decreased rate of the permeability coefficient showed a slowing trend. The results of the chloride ion permeability test indicated that the chloride ion-related impermeability of soil-cement was enhanced with the increase in the basalt content, which was confirmed by the consistent findings of the contrast permeability test. The comprehensive analysis shows that the optimal content ratio of the basalt fiber was 1.5%. Furthermore, a SEM analysis established that the addition of the basalt fiber reduced the soil-cement porosity, improved the structural compactness and formed a more stable whole. This study could serve as a valuable reference for soil-cement used in projects with impermeability requirements.

To promote the recycling of industrial waste residues in the reinforcement of foundation soil, the anti−seawater erosion of cement soil with ferronickel slag powder in the marine environment was studied. Specifically, this paper employed ferronickel slag powder to partially replace the cement. Then, the apparent morphology, unconfined compressive strength, and nuclear magnetic resonance (NMR) tests were performed on specimens of cement soil with ferronickel slag powder soaked in purified water and seawater. The research results reveal that with the rise in the content of ferronickel slag powder, the erosive effect of seawater on cement soil weakens, while the compressive strength of cement soil increases first and then decreases. With an excessive amount of ferronickel slag powder added to the cement soil, its chemically active effect decreases, leading to a decrease in the strength of the cement soil. When the admixture of ferronickel slag powder in cement soil is 45%, it achieves good performance. The addition of ferronickel slag powder improves the plasticity of cement soil. The higher the content of ferronickel slag powder, the greater the failure strain and residual strength of the cement soil. Microscopic studies indicate that with the increase in the content of ferronickel slag powder, the pores in the cement soil become smaller and smaller, the total pore volume decreases, the continuity of the pore size distribution improves, and the structure becomes more compact, thus enhancing the erosion resistance of cement soil.

In order to study the law of evolution of erosion time on the impermeability of soil-cement in the marine environment, permeability tests, X-ray diffraction (XRD) tests, and scanning electron microscopy (SEM) tests were conducted on ferronickel slag powder (FSP) soil-cement. The changes in the permeability properties of the soil-cement under different soaking age conditions were investigated. The results show that the marine environment has little influence on the impermeability of soil-cement at an early age, and that their permeability coefficient is essentially identical to that of clear water. The impermeability of soil-cement in the marine environment decreases significantly after 28 days, and it continues to decrease with age. However, the deterioration in impermeability of soil-cement caused by the marine environment can be alleviated after FSP is added to the soil-cement, and a better mixing value of 40% is obtained. At the same time, the regression curve equation of the permeability coefficient of soil-cement with the change of age is established. FSP exerts a microaggregate effect and chemical activity in the soil-cement. It not only improves the compactness of the soil-cement matrix but also prevents the penetration of corrosive ions into the soil-cement, thereby improving the impermeability of the soil-cement.

In this research, Ni-Fe slag powder and mineral powder are blended into mineral admixtures and added to soil cement, with the aim of investigating the mechanical property of soil cement under a dynamic environment, and the dynamic properties of Ni-Fe slag powder soil cement after impact compression are obtained by conducting split-Hopkinson pressure bar (SHPB) test. The results show that under the same age and different admixture conditions, the dynamic stress of Ni-Fe slag powder soil cement increases first and then decreases and reaches the maximum when the admixture ratio is 40%, and the dynamic stresses at 7 d, 28 d and 60 d were 5.10 MPa, 9.73 MPa and 13.51 MPa, respectively. Under the same admixture ratio, Ni-Fe slag powder soil cement shows an increasing trend in dynamic stress with age, and its growth rate at the curing age from 7 d and 28 d is significantly higher than that at the curing age from 28 d to 60 d. After comparison, it is concluded that the best admixture ratio for Ni-Fe slag powder is 40%, which is close to the maximum value of 45% for mineral admixtures to replace cement as specified in the national standard.

The influence of basalt fiber on the impermeability of soil-cement is studied by the tests of permeability, anti-chloride ion resistance and scanning electron microscope. The mixing basalt fiber mass fractions for different tests are 0, 0.5%, 1.0%, and 1.5%, respectively. The permeability coefficients and electric fluxes of basalt fiber soil-cements are obtained. Results show that the addition of basalt fiber can obviously enhance the impermeability of soil-cement. With the increase of basalt fiber content, both the permeability coefficient and the value of electric flux decrease. The optimal mass fraction of basalt fiber is 1.5%. The incorporation of basalt fibers can effectively connect the discrete soil particles and make the basalt fibers, soil particles and cement form a more stable whole.