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 (fc = 21–35 MPa), rebar diameters (db = 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 (tcrack) and crack propagation rate (rcrack) were used as primary indicators. The results showed that crack initiation was strongly influenced by db and c, with D16 bars initiating cracks earlier than D12 bars, while an increased cover depth delayed crack initiation. For example, tcrack increased from 213 h for a 40 mm cover to 339 h for a 92 mm cover. Contrarily, fc and the w/c ratio primarily affected crack propagation. Specimens with a lower w/c ratio exhibited higher crack propagation rates, with rcrack = 0.17 mm per 100 h for w/c ratio = 0.41 compared with rcrack = 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 fc, db and c. The proposed model showed strong predictive capability (R = 0.906, R2 = 0.82), providing improved estimation of crack initiation in RC structures.