Research on internal monitoring of reinforced concrete under accelerated corrosion, using XCT and DIC technology

Abstract

Reinforcement corrosion and induced cracking of concrete is the major durability problem for concrete structures in the marine environment. And the evolution of expansion stress produced by reinforcement corrosion is a crucial parameter for the cracking of concrete. However, it’s difficult to directly measure the expansion stress by traditional measurement techniques since reinforcement is embedded in the concrete. In this study, concrete specimens mixed with seawater and reinforced by two kinds of steel bars, Q235 carbon steel bar and corrosion-resistant steel bar, were subjected to accelerated corrosion. X-ray computed tomography (XCT) was used to in situ and in real-time monitor the corrosion process of concrete, what digital image correlation (DIC) is for analyzing the inner expansion strain variation of reinforced concrete. The results show that the images collected by XCT can directly reflect the cracking position and the whole corrosion process of reinforced concrete. Meanwhile, the internal strain evolution can also be quantitatively calculated via DIC based on CT images. And the feasibility of combing XCT and DIC can be verified by the existing corrosion expansion cracking model. The correction coefficient of the non-uniform corrosion of carbon steel bar and corrosion resistance steel bar is KS1 = 9.3 × 10−4, KS2 = 2.4 × 10−4, respectively. The corrosion expansion stress that causes the initial corrosion expansion and cracking of the concrete is 2.5 Mpa and 3.0 Mpa, respectively. Furthermore, it can be observed that the uneven corrosion of steel bars, as well as the compressive stress or tensile stress caused in different parts of concrete. Additionally, the corrosion delay effect of corrosion resistance steel bar is not obviously under potentiostatic accelerated corrosion.