Soil utilization of solid waste: Small strain characteristics of coastal cement soil modified by oyster shell powder under freeze-thaw cycle

The resource utilization of oyster shell powder (OSP) holds significant implications for solid waste disposal and global carbon cycle. This study investigates the effect of OSP on the small strain characteristics and microstructural mechanisms of coastal cement soil under freeze-thaw cycle conditions. Resonant column tests and scanning electron microscope (SEM) analysis were conducted on OSP modified coastal cement soil (OSPCS) samples with different OSP contents (0, 5 %, 10 % and 15 %). The test results indicate that the dynamic shear modulus ( G ) decreases as OSP content increases, while the damping ratio ( D ) initially decreases and then increases with increasing OSP contents, reaching its minimum and maximum at 5 % and 15 % OSP content. Additionally, OSP enhances the frost resistance of coastal cement soil. Although the G and D gradually decrease with increasing freeze-thaw cycles, OSP mitigates their loss rate (approximately 9 % and 20 %). OSP not only fills the pores within the sample, but also promotes cement hydration, increasing particle density and reducing water content, thereby weakening the adverse effects of frost heave and contraction. Finally, two three-dimensional fitting models were established for G max , confining pressure and OSP content under standard curing conditions, and for G max , confining pressure and number of freeze-thaw cycles under freeze-thaw cycle conditions. The model predictions align well with the experimental data. These findings provide a theoretical basis for OSP application in coastal cement soil and a reference for solving the problem of poor frost resistance, which has a critical engineering significance for foundation treatment in coastal areas. • .A new type of foundation material in cold regions was developed. • .An effective way of OSP resource utilization was proposed. • .Small strain characteristics and frost resistance of OSPCS were investigated. • .The 3D fitting model of OSPCS G max was established.