Analysis of material changes in Pisha sandstone geopolymer composite cement-cured soil under dry–wet-salt intrusion coupling based on TG/DTA-FTIR

This research analyzed the characteristics of the microscopic pore structure of the soil cured with Pisha sandstone geopolymer composite cement under dry and wet cycling conditions. And the internal microstructure of the eroded Pisha sandstone geopolymer composite cement-cured soil was carried out by XRD physical phase analysis and simultaneous thermal analysis—Fourier infrared spectrometry. XRD and simultaneous thermal analysis Fourier infrared spectroscopy were used to analyze the internal microstructure of the cement-cured soil with a Pisha sandstone ground polymer composite under the erosion of magnesium salt, and to obtain the mineral evolution mechanism of the soil. The internal void structure was measured using the mercury intrusion method.The results show that, under the action of magnesium chloride, dry and wet coupled erosion. The strength of the cement-cured Pisha sandstone geopolymer composite soil decreases faster after 7 cycles of dry and wet salt erosion coupling and there is a tendency to soften the load. The porosity of Pisha sandstone geopolymer composite cement-cured soil has increased by 3.88% after 30 cycles of the action of total porosity, of which the percentage of pores in the interval of 10–100 nm decreases. The percentage of pores in the 1000 nm interval decreases. The percentage of pores in the > 1000 nm interval increased significantly. The increase in the proportion of large pores and the decrease in the proportion of small pores caused the specimen structure to become loose, which in turn led to a decrease in strength. The structure of potassium A-type zeolite and dolomite of Pisha sandstone ground polymer composite cement cure soil was damaged under erosion of magnesium salt, and less stable Sepiolite was generated and the CaCO₃ content in the system decreased, which gradually evolved into the MgCa (CO₃)₂ composite system. This study can provide a theoretical basis for the cement-cured soil of Pisha sandstone geopolymer composite for the construction of agricultural water conservancies in a salt-magnesium environment.