Influence of shotcrete accelerators on the hydration of cement pastes and their impact on sulfate resistance

Alkali-free, aluminium-based accelerators are often used for shotcrete linings in tunnels and mines, where external sulfate attack can occur. Therefore, it is essential to know, if the influence of on cement hydrate assemblage negatively impacts resistance. This study focuses effect hydration consequences attack. Aluminum sulfate-based cause rapid setting due very early formation ettringite accelerate alite hydration. At late ages, significant more AFm phases formed compared reference without accelerator, which during storage sodium solution react ettringite. A significantly higher volume increase additional exposure was calculated by thermodynamic modelling accelerated paste reference. Alkaline based aluminate form mainly amorphous calcium (sulfo-) hydrates at age, while seems be destabilized. The quantities than with alkali-free accelerator. finding compares well experiments concrete specimens, mixture alkaline accelerator deleterious expansion observed.