Frost Resistance and Shrinkage Characteristics of Soil Stabilized by Carbide Slag and Coal Gangue Powder

Abstract

With the increase of expressway construction in seasonal frozen soil region, the freeze-thaw problem of subgrade soil has attracted more and more attention. In addition, the comprehensive utilization of industrial solid waste has become an important measure to build a resource-saving and environment-friendly society. In order to improve the frost resistance of subgrade soil and realize the resource utilization of industrial solid waste, carbide slag (CS) and coal gangue powder (CG) were applied to the subgrade soil. The unconfined compressive strength (UCS) test, freeze-thaw cycle test, dry shrinkage test, temperature shrinkage test and scanning electron microscope (SEM) test were carried out on CS-CG stabilized soil with a ratio of CS:CG = 70:30 and dosages of 5%, 10% and 15%. The freeze-thaw cycle degradation model of CS-CG stabilized soil was constructed to show the freeze-thaw deterioration mechanism after the mechanical properties, pore structure, and durability characteristics of the stabilized soil were examined. The results showed that the CS-CG stabilized soil had good frost resistance. After 6 freeze-thaw cycles, the UCS at 7d and 28 d was 2.86 MPa and 3.79 MPa, respectively, which were 22.6% and 35.5% lower than in samples that underwent no freeze-thaw action. The CS-CG stabilized soil had good crack resistance, slightly better dry shrinkage strain than lime stabilized soil, and excellent temperature shrinkage performance. With the increase of CS-CG dosage, the hydration products increased continuously. After freeze-thaw cycles, however, large pores and cracks gradually appeared in the stabilized soil, which led to an increase of porosity and pore diameter, and a decrease of pore abundance. Due to the influence of hydration degree, the porosity change at 7 d was less than that at 28 d. There was a f(n)/f0=βexp−λΔh relationship between UCS residual ratio and porosity variation of the CS-CG stabilized soil, and it had a good correlation. The CS-CG stabilized soil had good frost resistance and shrinkage characteristics, and could replace traditional cementitious materials such as Portland cement (PC) and lime for subgrade soil improvement in regions with seasonal frozen soil. Future research needs to focus on the performance regulation of CS-CG stabilized soil, which can make it more widely used.