The effect of mixed cement types on steel in mortar at different environments

摘要

Corrosion of steel in concrete is affected by two processes taking place in concrete: carbonation and contamination or ingress of chloride ions. Although Carbonation allegedly increases mechanical strength of concrete, it also decreases its alkalinity. At a pH below 10, the steel's passivation layer dissolves and corrosion of steel initiates. With chloride ion presence at the surface of steel rebar, the self-catalytic reaction leads to voluminous ferrous (hydro)oxides growth, which causes spalling and delamination of surrounding concrete. The aim of this study is to monitor the early changes of the possible different corrosion mechanism of steel embedded in mortar, made from different cement compositions regarding the amount of clinker and used mineral admixture types and exposed to different enviroments. In the study, the effect of different cement compositions will be obsereved in relation to corrosion processes caused by carbonation and contamination by chloride ions. The effect of mixed cements with different clinker content and mineral admixture types on corrosion process of steel in mortar will be explored with Electrochemical Impedance Spectroscopy (EIS) measuring technique. Results of corrosion susceptibility to carbonation and ingress of chloride ions will be evaluated in relation to corrosion of steel surface, mechanical properties, porosity, resistance of capillary absorption, chloride content and chemistry properties of mortars prepared with CEM I-CEM V.