Lime stabilization is a widely used technique to improve weak subgrades; however, its effectiveness under freeze-thaw cycles remains a critical challenge. This study investigates the incorporation of cementitious materials to enhance the mechanical properties and environmental resistance of lime-stabilized soils under such conditions. Two types of soils, gray shale (plasticity index of 37.8) and clay soil (plasticity index of 19.0) from Nebraska, were used. Stabilization mixtures included lime dosages of 0%, 3%, and 6% by weight, combined with either 10% fly ash or 3% and 6% cement by weight. The experimental program comprised three stages: characterization of physical properties, preparation of composite specimens for unconfined compressive strength (UCS) testing, and evaluation of environmental resistance through freeze-thaw cycles (7 cycles after 14 days of curing and 12 cycles after 28 days of curing). Results showed that lime and fly ash significantly reduced the plasticity index of gray shale, with less pronounced effects on clay soil. Cement-lime stabilization demonstrated superior UCS retention and resistance to freeze-thaw cycles for both soil types, outperforming lime alone and lime-fly ash treatments. These findings highlight the importance of incorporating cementitious materials to enhance the durability and performance of lime-stabilized soils under harsh environmental conditions.

The swelling soils, also known as expansive soils, increase in volume due to an increase in moisture content. The settlement of expansive soils could be the main reason for considerable damage to roads, highways, structures, irrigation channel covers, and the protective shell of tunnels that use bentonite for wall stability. Therefore, it is important to determine the amount of swelling pressure in expansive soils. This research uses two laboratory swelling test methods with constant volume (CVS) and ASTM-4546-96 standard, the swelling pressure of lime-stabilized bentonite soil has been estimated. Based on the key findings of this study, the swelling pressure values of pure bentonite samples tested using the ASTM-4546-96 method, compared to the constant volume swelling test, show an approximately 170% increase.

Phosphogypsum, which contains toxic components (e.g., heavy metal elements and fluoride), is one of the byproducts of phosphoric acid production, and filling subgrade is one of the recycling methods for it. In this study, phosphogypsum was stabilized by lime to improve the mechanical properties [California bearing ratio (CBR), resilience modulus, unconfined compressive strength, and shear strength], water stability, and harmful substances dissolubility. Combined with scanning electron microscopy, the strength formation and water stability enhancement mechanism of lime-stabilized phosphogypsum (LSP) were explored. The results demonstrated that the mechanical properties of LSP were better with the lime content of 6%-10%. The CBR, resilience modulus, unconfined compressive strength, and shear strength were 3.35 times, 2.46 times, 8.61 times, and 1.39 times that of plain phosphogypsum, respectively. An intensity prediction model with a correlation of 97% was constructed. The CBR and resilience modulus softening coefficient of LSP reached best values when lime content was 6%-8%. The leaching concentration of arsenic, chromium, and lead of LSP with 2% lime met the quality standards of groundwater levels I, II, and IV, respectively. Fluoride and phosphate were not detected in LSP when lime content was greater than 6.0%. The results show that LSP is feasible as subgrade filler. Considering the mechanical properties, water stability, and dissolution of hazardous substances of LSP, it is recommended to add 6%-8% lime content to LSP as highway subgrade filler.

Saline soil in Northwest China is susceptible to frequent and severe freeze-thaw cycles (FTC), resulting in railway and pavement disasters, emphasizing the need for stabilizing inadequately constructed soils. The engineering characteristics of soils can be changed after FTCs, which results from the variation of microstructure. Physisorption experiments (BET), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were employed in this research to investigate how FTCs affected the micro-characteristics of lime-stabilized saline soil. According to the results, at the beginning of FTCs, the specific surface area (SSA) increased and then reduced after 3 FTCs. Moreover, the pores presented a bimodal characteristic and could be divided into inter- and intra-aggregate pores. The pore size distribution of the stabilized saline soil was altered by the FTCs. Additionally, the FTCs reduced the porosity of pores between 2 similar to 22 mu m and increased their complexity, while also creating more directional pore orientation. The results of this paper are believed to help advance soil stabilization methods and offer useful insights into the microstructural characteristics of lime-stabilized saline soil.