Electrochemical behaviour and corrosion sensitivity of prestressed steel in cement grout

Abstract

The durability of prestressed concrete bridges primarily depends on the steel wire cables. Several disorders in these bridges are well known, such as fracture of these cables by stress corrosion cracking due to water penetration in the prestressing ducts. This water can contain various aggressive constituents with respect to corrosion (like chlorides). Its penetration inside the duct is due to the presence of sealing defects of the structure or in the concrete (like cracks). The second category of defects relates to the cement grout injection, which protects cables. This occurs due to a degradation of the grout in contact with water (problems of bleeding and segregation) leading to brittle fractures of steels. The first step of the study consisted in obtaining a corrosive liquid typical of a segregated cement paste on which electrochemical tests were done. Electrochemical tests in synthetic solutions defined from a bibliographical study and analysis of real cases of segregated cement grout were also realized. High strength and ordinary steel specimens were used and all the tests were mainly done in deaerated conditions. The main results can lead one to consider that, in oxygen free conditions, steel specimens surface can be either in active or passive state. The susceptibility of steels to stress corrosion cracking was determined by the means of models applied to potentiodynamic polarisation.

Assessment of the stress corrosion cracking in a chloride medium of cables used in prestressed concrete structures by the acoustic emission technique

“…Steel has a fully oriented fine pearlitic microstructure which is fairly different from steel reinforcement [22,23]. Steel wires were obtained by the cold drawing process.…”

Identification of steel corrosion in alkaline sulfate solution by electrochemical noise

“…[17] Pertinent references include works by Bertolini and Carsana, [15] Lee and Zielske, [7] O'Reilly and Darwin, [23] and others. [16,21,22,[24][25][26][27] Carsana and Bertolini [15] attributed the corrosion to the development of pore water pH greater than 14. Newton and Sykes [28] described how the elevated sulfate ion concentrations in alkaline solutions with excess calcium hydroxide allow for an increase in pH.…”