Sulfate resistance and phase composition of shotcrete

Shotcrete is often in direct contact with groundwater containing sulfate. The resistance to sulfate attack of modern sprayed concretes produced non-alkali aluminate-based accelerators combination different cement types related their microstructure, transport properties, porosity and phase composition. A characterization these properties allows a comprehensive assessment the shotcrete identification relevant physical chemical influencing factors. As conventional concrete, type water binder ratio are also decisive for shotcrete. On one hand, capillary diffusion coefficient show cement-specific differences, accordingly solution uptake sulfur profile test specimen w/b different. other defines potential ettringite formation thus damage concrete. Sulfate expansion caused by conversion monocarbonate/hemicarbonate/monosulfate (AFm phases) ettringite. application sulfate-resistant cements does not guarantee each case. Their use, however, minimizes potential. In tests, causing drop dynamic modulus elasticity occurs at higher compared concrete due volume hardened paste smaller maximum aggregate size. studied alkali-free accelerators, currently used practice, found have no adverse effect on dosage investigated behave more favorably than aluminate based alkali-containing accelerators. However, influence indirectly permeability an increased