Abstract
Shotcrete is the primary material for tunnel support due to its early rapid hardening characteristics. During tunnel construction in a sulfate environment, the hardening law of concrete will be affected. In this study, samples were prepared at six different curing times and immersed in four different concentrations of sulfate solutions. A uniaxial test was conducted and analyzed to investigate the effect of sulfate attack on the mechanical properties of early aged shotcrete materials. Results indicated that waterlogged shotcrete does not have apparent cracks on the outside. The stress–strain curve or ultimate compressive strength of the samples showed that the effect of sulfate on shotcrete should be differentiated into chemical and physical sulfate attacks, according to the concentration of sulfate ions. The two parameters in the equation of the hardening behaviors of sulfate attack samples, ultimate compressive strength, and time constant, are related to sulfate concentration. The crack damage stress threshold of samples demonstrates that high-concentration sulfate corrosion leads to an impact on the durability of shotcrete.
Highlights
As a significant component of an initial support structure, shotcrete is often used in tunnels and slope engineering projects
The properties of early aged shotcrete have attracted the attention of researchers
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Summary
As a significant component of an initial support structure, shotcrete is often used in tunnels and slope engineering projects. According to the mechanical properties of accelerated concrete at different early ages, researchers could determine the parameters and the specific times for the following construction step; they tend to choose a more conservative approach, both in terms of design and in numerical simulations, which assumes that the initial shotcrete model is elastic and its properties are unchanged. Engineering practices sometimes have to deal with corrosive environments, e.g., the passing of the tunnels through underground areas or marine environments In these situations, sulfate ions will affect the early age properties of shotcrete. The effect of the chemical process on the accelerator has been studied, the effect of the sulfate environment on the early age properties, especially the mechanical properties of shotcrete, is not apparent. It constitutes the need to study early age behaviors of shotcrete under sulfate attack
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