Experimental Research on Mechanical Properties and Microstructure Characteristics of Silty Clay Subgrade Filler With Red Pisha Sandstone and Carbide Slag in Seasonal Frozen Regions

As the foundation structure of highway engineering, the quality of the subgrade determines the service life of highway engineering. Under this condition, the filling soils are frequently improved for raising the stability of the subgrade. Proper utilization of lower-cost waste materials will reduce demand for natural materials and the cost of construction. In this study, the red Pisha sandstone (RPS) and carbide slag (CS) as green and sustainable materials to reinforce the silty clay. The improvement effect was evaluated through freeze-thaw cycles test, triaxial compression strength test, particle-size distribution test, X-ray diffraction test, and scanning electron microscopy test. The results indicated that the addition of 15wt.% RPS and 15wt.% CS increased about 136% of the triaxial compressive strength of silty clay. With the increase of freeze-thaw cycles, the strength loss ratio and the deformation change slightly. It also has the excellent function of freezing and thawing resistance and shear strength. The key factors for the superior mechanical performance of RPS-CS stabilized silty clay are that more sand-size particles are beneficial to the hydration reactions of RPS and CS during the entire curing time, adequate flocculation and agglomeration of soil particles occurred. Many small-sized rounded and plate-like CSH gels filled most of the soils pores and isolated pores fractures became fewer in the samples, which produced a denser and less permeable material. The outcomes of this research will contribute to the utilization of red Pisha sandstone and carbide slag as a sustainable stabilizer in highway subgrade applications in seasonal frozen regions.