Deterioration Mechanism of New Grouting Materials Under Coupling Effect of Heat Damage and Sulfate Attack

Aiming at the typical high temperature sulfate environment in underground engineering, the degradation mechanism of the new grouting material under the coupling action of heat damage and sulfate erosion was studied. Forty-four groups of specimens with different water-binder ratios were prepared. The changes of appearance, mass, compressive strength and sulfate ion content of the specimens under the action of different temperature (20°C, 30°C, 60°C, 90°C) and different sulfate concentration (0, 5%, 10^%) were detected, the microstructure was observed by electron microscope (SEM), the content model of sulfate ion was established. The results show that: in the environment of sulfate erosion, high temperature has a significant effect on the deterioration of new grouting materials, the higher the temperature, the more obvious the deterioration. With the increase of water-binder ratio, the deterioration of new grouting materials becomes more and more serious. At the early stage of erosion, ettringite and other materials are gradually formed and continuously filled with pores and microcracks. At the later stage of erosion, the expansion stress of ettringite and the crystallization pressure of sulfate make the material gradually expand and destroy. The model of sulfate ion content established is in good agreement with the experimental results.