EVALUATION OF CORROSION IN CRACKED HIGH PERFORMANCE CONCRETE EXPOSED TO A NATURAL CHLORIDE ENVIRONMENT

ORAL EXAMINATION Doctor of Philosophy

Herwing Z. Lopez-Calvo

DATE: Wednesday, Sept 21, 2011
TIME: 2:00 pm
LOCATION: ADI Studio – HC 25

ABSTRACT:

Chloride-induced corrosion of reinforcing steel is the most serious maintenance concern facing the construction industry. Although several strategies, such as the use of corrosion inhibiting admixtures (CIAs) and supplementary cementitious materials (SCMs) or the application of protective coatings either on the reinforcing steel or the concrete surface have been proposed to control this destructive process, there are still several uncertainties about their effectiveness in cracked high performance concrete (HPC).

In this research program, effects of corrosion in cracked HPC exposed to a chloride environment were evaluated. Three phases of investigation in the laboratory and in the field were developed. In the first phase, the effects of the addition of CIAs and SCMs on the short and long-term compressive strength and certain durability properties of HPC were studied. In the second phase, the performance of different corrosion control methods (CIAs alone or in combination with SCMs, a silane surface pre-treatment and five types of epoxy coated rebars) in protecting steel in cracked HPC was evaluated. Finally, the third phase, evaluated the effects of chloride-induced corrosion on the tensile properties of reinforcing bars embedded in cracked HPC.

Results demonstrated that the addition of CIAs and SCMs, alone or in combination was not detrimental to the HPC properties; in fact, their combination tended to improve both the compressive strength and the durability properties of concrete. It was also found that HPC in its cracked state does not always provide corrosion protection to the steel in a chloride environment even when CIAs and SCMs were used in the mixtures. Nevertheless, the combination of two or more corrosion mitigating strategies, selection of an adequate w/cm, and an appropriate concrete cover were found to be relatively effective in controlling corrosion in cracked HPC; and thus, effective to mitigate the effects of chloride-induced corrosion on the tensile properties of the reinforcing steel.

http://www.unbf.ca/clubs/acegs/documents/HerwingLopez-Calvo.pdf