Probabilistic assessment of carbonation-induced depassivation in Brazilian reinforced concrete structures under climate change

Corrosion has long been recognized as a critical issue affecting the durability of reinforced concrete (RC) structures. Recent studies indicate that climate change is accelerating corrosion processes worldwide through rising temperatures, increasing atmospheric CO 2 concentrations, and variations in relative humidity. However, how these changing environmental conditions affect the spatial distribution of carbonation-induced depassivation risk remains poorly quantified in Brazil, despite its importance for service-life design and maintenance planning. This study addresses this gap by assessing carbonation risk in Brazilian RC structures exposed to diverse regional microclimates under historical and projected environmental conditions. Monte Carlo simulations were performed to estimate the probability of depassivation for structures built under different Brazilian design codes, construction periods, and exposure classes across 500 representative geographic locations. The resulting database was used to train a surrogate model capable of predicting depassivation probability for any Brazilian location and construction condition, achieving an R 2 of approximately 0.99 with low prediction error. Results show that older structures, designed under earlier codes with lower concrete cover and higher water-cement ratios, exhibit substantially higher depassivation probabilities than newer structures, especially under high-emission scenarios. In the Central-West region, structures built around 2000 may exceed a 50% probability of depassivation within 30 years under SSP3-7.0, whereas comparable structures built around 2020 remain below 30%. The North and Central-West regions show the highest risks. The proposed framework supports region-specific durability design, service-life assessment, and maintenance prioritization in Brazil.