Time evolution of corrosion-induced cracking in reinforced concrete under chloride exposure

The time-dependent initiation and propagation of corrosion-induced cracking in reinforced concrete (RC) was investigated, considering key material and geometric parameters. Accelerated corrosion tests were conducted on RC pull-out specimens with varying concrete compressive strengths (f_c = 21–35 MPa), rebar diameters (d_b = 12 mm, 16 mm and 19 mm), water/cement (w/c) ratios (0.41–0.60) and concrete cover depths (c = 20–92 mm). The crack initiation time (t_crack) and crack propagation rate (r_crack) were used as primary indicators. The results showed that crack initiation was strongly influenced by d_b and c, with D16 bars initiating cracks earlier than D12 bars, while an increased cover depth delayed crack initiation. For example, t_crack increased from 213 h for a 40 mm cover to 339 h for a 92 mm cover. Contrarily, f_c and the w/c ratio primarily affected crack propagation. Specimens with a lower w/c ratio exhibited higher crack propagation rates, with r_crack = 0.17 mm per 100 h for w/c ratio = 0.41 compared with r_crack = 0.07 mm per 100 h for w/c ratio = 0.48, indicating that denser concretes accelerate crack growth once corrosion is initiated. These results demonstrate that corrosion-induced cracking is governed by the interaction of reinforcement geometry, cover and material properties, rather than any single parameter. A regression-based model to estimate the crack initiation time was developed using experimental data, incorporating f_c, d_b and c. The proposed model showed strong predictive capability (R = 0.906, R² = 0.82), providing improved estimation of crack initiation in RC structures.