Corrosion potential: influence of moisture, water-cement ratio, chloride content and concrete cover

• Published in: Revista IBRACON de estruturas e materiais 2017-08, Vol.10 (4), p.864-885
• Main Authors: Medeiros, M. H. F., Rocha, F. C., Medeiros-JUNIOR, R. A., Helene, P.
• Format: Article
• Language: English
• Subjects: cloretos; cobrimento; ENGINEERING, CIVIL; potencial de corrosão; relação água-cimento; teor de umidade do concreto
• ISSN: 1983-4195; 1983-4195
• DOI: 10.1590/s1983-41952017000400005

ABSTRACT The method of measuring the corrosion potential is used as an electrochemical tool for helping the monitoring of the corrosion of reinforcements of concrete structures. As a criterion for evaluating results it is common to use intervals of corrosion potential and their correlation with corrosion probability, as precognizes ASTM C 876:2015. With this criterion, it is possible to establish an overview of the thermodynamic situation of corrosion in the structure or in the test specimen in laboratory. However, the method is influenced by several factors related with the concrete, the environment and with procedures adopted at the moment of executing the readings. Aiming to provide information to guide the technical and scientific environment regarding the right use of this type of non-destructive testing, the objective of this work is to evaluate some possible factors influencing the reading of corrosion potential, such as: moisture content of the concrete, water/cement ratio, thickness of the concrete cover and degree of contamination by chlorides. Results indicate that moisture and degree of contamination of the concrete by chloride ions had a tendency of making the corrosion potential more electronegative. Besides, it was verified that the influence of the cover is different for the case of contaminated concrete (1% of chlorides by mass of cement) and not contaminated with chlorides: the influence of the thickness of the cover, in the case of concrete contaminated by chlorides, was inversely proportional, in other words, the greater the cover thickness is, the less electronegative the value of the corrosion potential will be. On the other hand, in cases of concretes without chlorides, the effect of the cover thickness in the readings or corrosion potential was irrelevant. All this information was proved with 95% of statistical significance. RESUMO O método de medida de potencial de corrosão é utilizado como uma ferramenta eletroquímica de auxílio ao monitoramento da corrosão das armaduras de estruturas de concreto armado. Como critério de avaliação dos resultados, é comum que sejam adotados os intervalos de potencial de corrosão e sua correlação com a probabilidade de corrosão, preconizadas pela ASTM C 876:2015. Com este critério é possível estabelecer um panorama da situação termodinâmica de corrosão na estrutura ou no corpo de prova em laboratório. Porém, o método é influenciado por inúmeros fatores relacionados ao concreto, ao ambiente e aos pro