Delayed ettringite formation in the marine environment and its relationship to sulphate attack

Abstract

This study demonstrates how sulphate attack on exposed marine concrete structures causes ettringite formation in the water environment. Creating ettringite is linked to concrete's ability to repel and expand. The early formation of ettringite, which happens immediately, is the process that controls stiffening without damaging expansion and is linked to the management of time in the Portland cement paste environment (within hours). Though it does not show any reaction in a marine environment, this mechanism will cause a harmful expansion later after several seasons of exposure (DEF). Delayed ettringite formation (DEF) formed at late stages due to cracking and spalling in forms. For both external and internal attacks on sulphate-containing cells, DEF can be tested. Magnesium sulphate (MgSO4) must first be converted before being used another way (ettringite) to make hydrated calcium aluminate sulphate. DEF may occur at marine concrete structures, but it is not linked to sulphate attack but instead to seawater chloride intrusion, which causes corrosion of the concrete structures. As a result, the reaction of DEF is linked to sulphate and another mechanism that can contribute to concrete cracking and spalling.