Concrete cover cracking caused by steel reinforcement corrosion

The paper reviews previously reported predictive models on corrosion-induced crack initiation and propagation and presents new additional results of ongoing accelerated corrosion tests conducted at The University of Newcastle. In addition to eight concrete specimens previously tested, six new specimens were tested to study the effect of reinforcement confinement, concrete strength (24 and 8 MPa), cover (10 and 20 mm) and reinforcing bar diameter (16 and 27 mm) on corrosion-induced cracking. Time-dependent crack widths were measured for different reinforced concrete slabs for corrosion rates up to 169 μA/cm². It was found that predictions of time to crack initiation are highly scattered and can differ by as much as two orders of magnitude. It was also found that crack initiation and propagation times increase with increasing cover and decrease with increasing reinforcing bar diameter and compressive strength. In addition, the rate of crack propagation is 10–50% higher for reduced reinforcement confinement such as at the edge of a slab or corner of a column. The experimental results are compared with existing crack initiation and propagation predictive models allowing for the accuracy of existing models to be assessed and showing potential areas for further research.