Investigating the resistance to severe environmental erosion of modified Pisha sandstone composite materials

Pisha sandstone (PS) was the main resource of the Yellow River coarse sediment. This study aimed to investigate the microstructural evolution and the erosion resistance of modified Pisha sandstone composite materials (PCM) in severe environmental erosion, including water, alkali, acid, and sulfate solutions. The mechanical properties of the PCM were assessed using a universal testing machine, while the erosion resistance of the PCM in different environments was compared through the softening coefficient and strength loss rate. Additionally, the study examined the enhancement effects of blast furnace slag and cement admixture on the erosion resistance of the material. Mineralogical composition and microstructure were analyzed using XRD, SEM and TG. The results indicated that the mechanical properties and the erosion resistance of the PCM increased significantly with the addition of blast furnace slag, with the softening coefficient of 0.78 and a strength of 16.3 MPa. After exposure to erosion, the compressive strength of the PCM can reach up to 16.6 MPa, 18.1 MPa, and 17.1 MPa in acidic, alkaline, and sulfate environments, respectively. Further analysis revealed that the types of montmorillonite minerals in the PS has been altered by modification treatment, subsequently the erosion resistance of the PCM has been enhanced. PCM exhibits distinct reaction mechanisms in different environments. The recrystallization of feldspar and calcite enhances structural integrity in water and alkaline environments. The montmorillonite and gel of PCM are subjected to further erosion in the acid environment, which leads to the formation of microcracks. The microscopic morphology of PCM appears layered and convex in sulfate environments.