Abstract
In regions characterized by abundant water, the surrounding rock exhibits a high water content, which leads to calcium leaching in the shotcrete of the tunnel. This poses a significant hazard to the safe operation of the tunnel. The experimental design focuses on three commonly used accelerators in the market and investigates the leaching process of samples under accelerated leaching conditions. By integrating XRD, TG, and SEM-EDS testing, the calcium leaching mechanism of shotcrete was elucidated. Results revealed that sodium aluminate-based liquid accelerator exhibits the highest detrimental effect on mortar resistance against calcium leaching, followed by fluoroaluminic acid-based liquid accelerator. Additionally, an appropriate amount of aluminum sulfate-based liquid accelerator can effectively mitigate performance degradation during leaching processes in shotcrete. The addition of aluminum sulfate reduces CH content and C-S-H Ca/Si ratio of hydration products, leading to wrapping AFt generated by cement hydration with C-S-H and thereby slowing down solid calcium-containing substance dissolution in hydration products. A moderate accelerator can enhance shotcrete porosity so that corrosive products like CaCl2 accumulate in existing pores first, reducing shotcrete performance deterioration rate.
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