Potential differences between passive reinforcement segments in concrete components in dependency of binder type, aeration conditions and quality of the steel/concrete-interface

摘要

For exploring the chloride threshold level of steel in concrete, respectively the onset of active reinforcement corrosion in general, the environmental and electrochemical conditions in the passive state are decisive. For reinforced concrete structures in practice, possible characteristics of the inner polarization state and the resulting potential differences, mainly forced by moisture deviations in the structure, are not commonly known. In this paper the exploration of four slab like specimens and two column bases with "real" dimensions, which are cyclically exposed to chloride solution for simulating typical moisture conditions for outdoor structures, is described. Ordinary portland cement (OPC, CEM I) and blast-furnace slag cement (BFSC, CEM III) are used. For various, decoupled segments of the reinforcing steel potential differences are determined and depolarization measurements are performed. The concrete compositions with different binder types show considerably diverging results. The maximum of the determined potential differences is 150 mV for OPC specimens and 650 mV for BFSC specimens. The extent of instant effects of changing exposure conditions also is completely different. Generally, exposure (wetting) causes a displacement of the potential to more negative values. Other impact parameters do not lead to a clear pattern of behavior or reaction.