Crack propagation characterization of concrete under non-uniform corrosion of steel strand using digital image correlation

The steel strands in pretensioned prestressed concrete are susceptible to corrosion and expansion due to threatening environmental conditions, leading to concrete cracking, reduction in the bearing capacity and durability of structures. This paper presents an electrochemical accelerated corrosion test on steel strands. The internal strain, surface strain, and crack propagation in concrete specimens during the entire corrosion process of steel strands are continuously monitored using the digital image correlation (DIC) method and strain detection methods. The study investigates the effects of concrete cover thickness and stirrup arrangement on the surface strain field and crack propagation in concrete. A mesoscopic numerical model of concrete cracking under non-uniform corrosion of steel strands is established. The reliability of the constructed model is verified using experimental data. The results show that compared with traditional strain detection methods, the DIC method can detect initial cracks on the concrete surface 20 hours in advance. The proposed non-uniform mesoscopic simulation model can accurately simulate the entire process of concrete cracking induced by non-uniform corrosion of steel strands. The finite element (FE) model is consistent with the results obtained from DIC monitoring.