Assessment of the potential loss of durability of reinforced concrete under climate change - Impact of the evolution of environment parameters on carbonation of concrete

The construction sector faces the dual challenge of reducing greenhouse gas emissions while ensuring the long-term durability of structures in a changing climate. Among the degradation mechanisms affecting reinforced concrete, carbonation is particularly sensitive to environmental parameters such as temperature, relative humidity, atmospheric CO₂ concentration and precipitation patterns, which are expected to evolve significantly over the coming years. However, most carbonation models used in practice are calibrated under stationary environmental conditions, limiting their applicability to nonstationary climates. This study first analyses the sensitivity of a carbonation model -based on fib ModelCode -to environmental parameters, highlighting the importance of simultaneously considering the variation of all four environmental parameters. Secondly, this study proposes a time-dependent carbonation modelling method that explicitly accounts for the temporal variability of environmental parameters and the cumulative nature of the carbonation process. The approach is based on an incremental formulation inspired by the equivalent time concept commonly used in creep modelling. Approximating analytical results, this approach ensures a better continuity of the carbonation front while preserving exposure history. An application to a case study located near Paris, subject to climate projections derived from IPCC scenarios, shows a clear acceleration of carbonation under future climate conditions compared to static assumptions. Compared to a non-incremental model, this approach significantly reduces overestimations of carbonation depth, which is consistent with the mitigation and adaptation objectives of the construction sector.