A study of steel rebars embedded in concrete during 65 years

Several experimental techniques were used to study the corrosion products formed on steel rebars embedded in concrete during 65 years. The research has the objective of understanding the stages of rusting of steel in concrete. Such understanding would provide information concerning the environmental conditions that produce rusting. It was found that rust was composed of two layers: an inner one composed mainly of non-stoichiometric magnetite and probably Ca and Al substituted magnetite firmly adhered to the substrate, and an outer one composed of α- and γ-iron oxyhydroxides, final steel corrosion products. The chemical and mechanical properties of steel rebars and the surrounding concrete were investigated in order to establish the causes of corrosion initiation which were the drop of the concrete pH due to a carbonation process and the loss of steel passivity.