Experimental Investigation on Crack Initiation and Propagation Due to Corrosion of Reinforcement

Abstract

In this research, an investigation was carried out through experimentation to explore the mechanism of concrete cover cracking because of expansive pressure induced by corrosion products. The study aimed to monitor structural health by monitoring the crack width and crack propagation in the cover concrete so that the level of corrosion might be discovered. Concrete prisms of 200 by 200 by 300 mm reinforced with 60-grade 12-mm-O plain mild steel bar were used to simulate reinforced concrete beams having various cover thicknesses of 20, 37.5, 50, and 75 mm, respectively, to observe the mechanism of crack initiation, propagation, and level of corrosion with respect to the width of surface crack. The level of corrosion was measured in mg/cm2 following Faraday’s law and by gravimetric loss method, and the width of crack was measured by image analysis. For a cover thickness up to 37.5 mm, crack was initiated from the outer face and propagated inward, whereas for a cover thickness of 50 mm and greater, crack was initiated at the steel-concrete interface and propagated outward. A linear relationship was found between crack width and level of corrosion. For cover thicknesses of 20 and 37.5 mm, the critical corrosion amount (CCA) needed to initiate crack was about 22 mg/cm2. However, a sudden increase in CCA was noticed when the cover thickness was 50 mm and greater. For a cover thicknesses of 50 mm and 75 mm, the CCA values were 129 and 211 mg/cm2, respectively.