Real-time strain monitoring of reinforced concrete under the attacks of sulphate and chloride ions based on XCT and DIC methods

Abstract

In this work, the influences of different sulphate and chloride laden environment on the corrosion of reinforced concrete have been examined in real time by the digital image correlation (DIC) technology combined with a traditional strain measurement, and the applicability of DIC technology for monitoring the entire life cycle of reinforced concrete is verified. The main testing parameters include: (1) electrical current between steel bar and stainless steel sheet are measured by ampere meter, (2) expansion strain values are obtained by the traditional strain measurement, (3) micro-strain fields are obtained by the DIC technology. According to the above parameters, the influence of chloride and sulphate ions on the corrosion process of concrete reinforcement can be compared and analysed. The obtained results reveal that sulphate ions inhibit the corrosion of steel bars and suppress the corrosion effect produced by chloride ions. In addition, a model for predicting the corrosion-induced expansion stress at the steel–concrete interface is established, and its time variation is accurately quantified. The critical corrosion-induced expansion stress generated in reinforced concrete under the action of a single chloride salt solution is 2.25 MPa, and the corresponding initial cracking time is equal to 100 h. Meanwhile, the corrosion-induced expansion stress of the reinforced concrete specimen exposed to a composite solution of chloride and sulphate ions is 2.0 MPa, and its initial cracking time equals 150 h.