Quantitative assessment of rebar corrosion and bond deterioration in reinforced concrete

Corrosion of reinforcing steel is a critical factor affecting the durability of reinforced concrete structures, as it weakens both the steel’s electrochemical stability and its bond with concrete. This study evaluates the influence of rebar diameter (16 mm, 20 mm, and 25 mm) on corrosion behaviour and bond strength degradation under accelerated corrosion for 3, 6, and 9 days. Corrosion potential (E_corr) measurements were used to monitor steel depassivation, while pull-out tests quantified bond strength, along with residual and loss of bond strength. The results showed a clear dependence on bar diameter. The 16 mm rebars exhibited the highest initial bond strength (8.8 MPa) but suffered the most rapid deterioration, reducing to 3.3 MPa with 55% loss after 9 days. The 25 mm rebars, despite the lowest initial strength (6.4 MPa), showed a steady and predictable decline to 2.6 MPa (59% loss). The 20 mm rebars offered the most balanced performance, combining a high initial bond (7.9 MPa) with slower deterioration, retaining 4.2 MPa (46% loss) at 9 days. E_corr trends supported these outcomes, with smaller rebars depassivating earlier while larger bars sustained passivity longer.