Experimental study on sulfate resistance of shotcrete with different liquid accelerators

The shotcrete used as the initial lining of tunnel was easily damaged by sulfate attack in groundwater environment. The purpose of this study was mainly to explore the deterioration and mechanism of shotcrete mixed with different liquid accelerators under the conditions of semiimmersion and dry-wet cycles sulfate attack. Through comparative analysis of the test results of mass loss, compressive strength, relative dynamic elastic modulus and surface morphology of shotcrete specimens, it was obtained that different liquid accelerators had obvious differences in the performance of shotcrete deterioration. Among them, the shotcrete with 5.0% AR (alkaline liquid accelerator based on sodium aluminate) was the most severely degraded, while the shotcrete with 8.0% AS (alkali-free accelerator based on aluminum sulfate) had the strongest resistance to sulfate attack. In addition, combined with XRD, TG and SEM to analyze the corrosion products on the surface of shotcrete, it was found that the sulfate attack of shotcrete with 5.0% AR might be mainly gypsum and ettringite corrosion, but the deterioration of shotcrete with 8.0% AF (alkali-free accelerator based on fluoroaluminate) and AS was basically caused by little ettringite corrosion.