Performance Analysis of Sulfate Pisha-Sandstone Cement Soil Based on the Grey Entropy Theory

The exploitation of Pisha sandstone is one of the most significant strategies for environmental protection and resource saving in the border areas of Shanxi, Shaanxi, and Inner Mongolia, where Pisha sandstone is widely distributed. The goal of this research was to develop a method by which to transform Pisha sandstone cement soil into a new type of material which could be applied in saline regions, thereby achieving a wider application. The micro-pore and structural characteristics of cement soil samples which had been soaked in 0.5 mol/L of sodium sulfate solution were analyzed using nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and scanning electron microscopy methods (SEM). The results showed that the compressive strength of the sandstone cement soil decreased with the increase in the sulfate intrusion days. Under the erosion of sodium sulfate solution, the lower the cement content was, the more quickly the strength decreased. The main mineral composition diffraction peaks of sulfate sandstone, along with the diffraction peaks of sulfate corrosion products, tended to change during salt invasion. The mineral components in the sandstone can provide a material basis for the formation of the sulfate erosion products of cement soil. In addition, the grey entropy theory can be utilized to explore the correlation degree of the porosity, T2 spectrum area, bound fluid saturation, free fluid saturation, and unconfined compressive strength of the specimen. The results obtained in this research investigation provided a theoretic basis for the practical engineering applications of Pisha-sandstone cement soil in saline regions.