Chloride Transport Resistance, Concrete Cover Performance, and Service-Life Assessment of Reinforced Concrete under Brazilian Durability Requirements
Abstract
Chloride-induced corrosion is one of the main causes of premature deterioration in reinforced concrete structures exposed to marine and industrial environments. In such conditions, durability depends not only on the quality and transport resistance of the cementitious matrix but also on the adequacy of the reinforcement cover thickness. Although ABNT NBR 6118:2026 prescribes minimum concrete cover requirements according to environmental exposure classes, experimental validations of these recommendations under severe chloride exposure conditions remain limited. This study evaluates the effectiveness of the minimum reinforcement cover thicknesses specified for high environmental aggressiveness classes (EC III and EC IV) through accelerated chloride migration testing and the analysis of concrete quality parameters. Concrete specimens were produced using ordinary Portland cement (PC V ARI RS) with water-to-cement (w/c) ratios ranging from 0.43 to 0.68. The experimental program included compressive strength, ultrasonic pulse velocity (UPV), water absorption, void index, chloride penetration depth, and non-steady-state chloride migration coefficient (Dns) measurements. Chloride penetration fronts were determined by colorimetric analysis after accelerated migration testing and compared with the nominal concrete cover thicknesses prescribed by ABNT NBR 6118:2026. The results demonstrated that all investigated mixtures presented chloride penetration depths lower than the minimum cover thicknesses specified for EC III and EC IV, even for concretes that exceeded the maximum w/c ratio limits established by the standard, indicating the conservative nature of the Brazilian prescriptive durability approach. Chloride penetration depths decreased from approximately 25 mm to 13 mm as the w/c ratio decreased, while Dns values were reduced from 12.08 × 10–12 to 4.11 × 10–12 m2/s, indicating substantial improvements in chloride transport resistance due to matrix densification and reduced transport pathways. Strong correlations were observed between chloride penetration behavior and Dns, compressive strength, void index, and UPV, demonstrating the influence of pore connectivity and internal concrete quality on chloride transport. Additionally, the experimentally obtained Dns values allowed comparative interpretations regarding the long-term chloride resistance and potential service-life performance of the investigated concretes.