Investigation of macro-cell corrosion in rebar within cracked concrete beams under sustained loading conditions in the simulated marine environment

Abstract

Existing research presents the relationship between rebar corrosion and concrete transverse cracks, yet there is no clear consensus on the combined effects of crack width and marine corrosion environments on macro-cell corrosion. In this experiment, two sets of reinforced concrete beam specimens, each with different compressive strengths, were fabricated and subjected to sustained loads to induce multiple transverse cracks and to maintain their widths. Electrochemical techniques were utilized to investigate both macro-cell and micro-cell corrosion of rebar in cracked concrete beams across various simulated marine environments. The test results indicate that for crack widths up to 0.3 mm, the micro-cell corrosion current density of rebar in the full immersion corrosion zone is higher than that in the water level fluctuation zone. However, when the crack width is reduced to below 0.2 mm, the micro-cell corrosion current density decreases significantly, showing minimal variation across different corrosion zones. In the full immersion corrosion zone, cracks in the reinforced concrete beams generally do not cause macro-cell corrosion of the rebar. In contrast, in the water level fluctuation zone, macro-cell corrosion occurs, with wider cracks leading to more severe macro-cell effects. The effective macro-cell current accounts for about 40 % of the total corrosion current for rebar acting as macro-anodes. However, the macro-cell effect gradually diminishes as the cracks undergo self-healing.