Stability of Friedel's salt in carbonated concrete structural elements

It is of significant scientific and engineering benefit from the corrosion view point, to know the state of Friedel's salt in concrete structures subjected to the simultaneous attack of chlorides and atmospheric carbonation. An attempt is made in the present experimental investigation to elucidate the role of atmospheric carbonation on the stability of the Friedel's salt in chloride contaminated structures. For this purpose, four different types of concrete slabs, were subjected to chloride penetration over a total period of about three years and then exposed to atmospheric carbonation for almost the same period. The stability of Friedel's salt, based on XRD and DTA results is shown to be pH dependant. The solubility of Friedel's salt increases with the degree of carbonation of the concrete. It is also concluded that the stability of ettringite is also pH dependant.