ZHOU Zhiyao¹，CHENG Yinyin¹，ZHANG Zhe¹，WANG Zi¹，LAN Yongjun¹，LI Hongbo^1，2，3

1. School of Civil and Hydraulic Engineering， Ningxia University， Yinchuan 750021， China；2. Ningxia Engineering Technology Research Center of Water-saving Irrigation and Water Resources Regulation， Yinchuan 750021， China；3. Engineering Research Center of Ministry of Education for Efficient Utilization of Modern Agricultural Water Resources in Arid Regions， Yinchuan 750021， China

Abstract

Objective The saline soil foundation in the Ningxia region experiences significant strength deterioration due to salt-frost heave and salt corrosion. This poses a substantial threat to buildings and infrastructure. To address this， researchers have proposed a novel approach that utilizes solid waste to partially replace cement in stabilizing saline soil. This method not only promotes the use of solid waste resources but also significantly improves the compressive and shear resistance of the saline soil foundation. By addressing both environmental and structural concerns， this approach presents a sustainable solution to the challenges posed by saline soil in Ningxia.

Methods This study investigated the use of various curing agents， including cement， fly ash， silica fume， and brick powder，for stabilizing saline soil. To assess the effectiveness of these materials， unconfined compressive strength and triaxial shear tests were conducted based on an orthogonal test scheme. This comprehensive testing approach ensured that the effects of different curing agent contents on the unconfined compressive strength and shear strength of saline soil were thoroughly analyzed.Advanced techniques such as X-ray diffraction （XRD） and scanning electron microscopy （SEM） were employed to examine the microstructural changes in the soil samples. These analyses provided detailed insights into the optimal curing combination for enhancing the properties of saline soil.

Results and Discussion The research investigated the impact of various admixtures on the unconfined compressive strength of solidified saline soil. The findings revealed that cement and silica fume significantly enhanced the unconfined compressive strength of the treated saline soil. Cement， known for its strong binding properties， contributed to the formation of a robust matrix that effectively resisted compressive forces. The addition of silica fume， characterized by its fine particle size and high pozzolanic activity， acted as a supplementary cementitious material， further strengthening the matrix and improving the overall strength. Silica fume enhanced the density and durability of the soil by filling voids and contributing to the formation of additional cementitious compounds. Fly ash exhibited a complex effect. Initially， an increase in strength was observed with increasing fly ash content， likely due to its pozzolanic activity and its contribution to the formation of additional cementitious compounds. However， beyond a certain point， further addition of fly ash led to a decrease in strength. This decline was possibly due to the dilution of the cement paste and the formation of weaker hydration products. This suggested that there was an optimal content of fly ash that maximizes its beneficial effects without compromising the overall strength of the soil. Brick powder， while possessing potential pozzolanic properties， required an alkaline environment provided by the hydration reaction of cement to activate its reactivity. Consequently， its contribution to the strength of solidified saline soil was limited compared to the other admixtures. The study found that brick powder， although beneficial in certain contexts， did not perform as effectively as cement， fly ash， or silica fume in enhancing the strength of the soil. Overall， the effectiveness of the four curing agents in enhancing the strength of cured saline soil followed the order： cement > fly ash > silica fume > brick powder. This ranking reflected the varying degrees of pozzolanic activity， binding capacity， and reactivity of each admixture in the context of solidified saline soil. These insights are crucial for developing effective soil stabilization strategies.

Conclusion The optimal composition for cement-based materials used to stabilize saline soil was found to be 3% cement，5% fly ash，5% silica fume， and 6% brick powder. This specific composition significantly enhances the strength of the solidified saline soil through the interaction of various crystalline compounds， including calcium silicate hydrate （C-S-H）， calcium aluminate hydrate （C-A-H）， and ettringite. These crystals， through their interconnectivity， contribute to a transformation in the soil’s structure. Initially， soil particles exist as individual units or small clusters. The introduction of these crystals facilitates the development of a more complex， three-dimensional network structure. This interconnected network enhances the adhesion between soil particles， salts， and the gelled substances present in the cement-based material. The findings of this research provide valuable insights for the design of cement-based materials， specifically tailored for curing saline soil. Understanding the optimal composition and the underlying mechanisms of strength enhancement paves the way for more effective and durable soil stabilization solutions. This study not only addresses the immediate challenge of strengthening saline soil foundations but also contributes to the broader goal of sustainable construction practices. By promoting the use of solid waste materials in soil stabilization， this research supports environmental sustainability while ensuring the safety and durability of infrastructure in saline soil regions. The innovative approach outlined in this study represents a significant advancement in the field of soil stabilization and has the potential to be applied in other regions facing similar challenges.

Keywords：solidified saline soil； unconfined compressive strength； mechanical property； microscopic analysis

DOI：10.13732/j.issn.1008-5548.2025.01.012