Influence of the Interfacial Transition Zone Properties on Chloride Corrosion in Reinforced Concrete-Characterization of ITZ

Large part of life cycle cost of reinforced concrete structures, especially infrastructures, is maintenance costs, where steel corrosion induced by chlorides is the major part [1, 2]. Normally, concrete provides the reinforcing steel an environment that preserves it in its passive state. High chloride concentration in the vicinity of the steel can lead, however, to steel activation [3]. The chloride threshold for steel activation was found to be significantly different in variety of the closely related environments of concretes, mortars, and simulated pore solution. In concretes and mortars the chloride threshold was found to be significantly higher than that in simulated pore solutions [4]. Two parameters can be the underlying mechanism for this observation: 1. Concrete chemistry is different than that of the paste and common simulated pore solutions, or 2. the micro-structure of the concrete-steel interface is different [5, 6]. Soluble silicate ions in the pore solution, which may arise from the cement, pozzolans or aggregates, also influence the chloride threshold. Several studies showed that the passivation film formed in the presence of dissolved silicate is significantly different from that created in its absence. Hence, chemical differences in concrete composition, especially in the presence of pozzolans, ca