Corrosion propagation in cracked reinforced concrete structures

[摘要] ENGLISH ABSTRACT: The durability of a reinforced concrete (RC) structure is significantlyinfluenced by the presence of cracks. Cracks act as pathways that accelerate the ingress of corrosion agents into the concrete to theembedded reinforcement. This causes the acceleration of both the corrosion initiation and propagation stages of degradation. The increase in the corrosion rate in the corrosion propagation stage leads to a reduction in the residual service life of a structure. The overall effect ofcracks in RC structures is that the residual service life of a structure is remarkably shortened.In recent years, many researchers have investigated the corrosion of structures in the propagation stage. However, the majority of these investigations are focused on specimens with only one crack andreinforcement rod. This study investigates cracked RC exposed to chloride-induced corrosion. The experimental investigation considers three different reinforcement layouts, namely 1Y10, 2Y10 and 3Y10, andfour crack spacings (Sc), as follows: single crack, 70 ≤ Sc ≤ 85 mm, 85< Sc < 100mm ≤ 100 ≤ Sc ≤ 120 mm. Twenty-seven 150 x 150 x 700 mm long beams were sustained in flexural loading to maintain a consistentsurface crack width of 0.4 ± 0.1 mm. The specimens were subjected to cyclic ponding for 36 weeks, and were monitored weekly to measure the corrosion rate and corrosion potential.The results indicate that the corrosion rate of the RC members is influenced by a change in reinforcement density. For a given crack spacing, the corrosion rate decreased with an increase in reinforcementdensity. In addition, the corrosion rates were influenced by different crack spacing. It was also observed that single cracked specimens were susceptible to a higher corrosion rate than the multiply cracked specimens. The combined effect of reinforcement density and crackspacing has shown that apart from a complex relationship between the anode and cathode region, the increase in reinforcement density has a greater inuence on the corrosion rate than the increase in crack spacing.In current practice, the onset of the corrosion propagation stage conservatively marks the end of the structure's serviceable life. A model for determining the residual service life of a structure in the corrosionpropagation stage is proposed. This model may be used to gain insight regarding a structure's \corrosion state for planning maintenance and determining its remaining service life. The study recommends that reinforcement density and crack spacing, accompanied by the predictionof residual service life, should be taken into consideration in the durability design of RC structures.

[发布机构] Stellenbosch University