• Concrete in urban tunnels is exposed to high CO 2 concentrations. • CO 2 concentrations are crucial in determining the evolution of concrete carbonation. • CO 2 concentrations are dependent on traffic intensity and vehicle circulating fleet. • Concrete carbonation can affect the life span of concrete structures. Urban tunnels are exposed to high CO 2 concentrations, which can lead to concrete carbonation and considerably reduce the life span of the infrastructure. Carbonation prediction models are powerful tools to forecast the evolution of this phenomenon, with CO 2 concentration as a key input parameter. In this work, CO 2 concentrations inside a ventilation gallery of the Madrid Calle 30 urban tunnels were calculated since their construction in 2007 based on the evolution of the measured traffic intensity inside the tunnels and the evolution of the circulating fleet. A forecast of CO 2 concentrations until 2057 was also performed, considering the evolution of traffic in the area. Regarding the circulating fleet, two different scenarios were studied: one based on the evolution analysed from 2007 to 2022, and another accounting for measures to achieve climate neutrality by 2050. It was concluded that CO 2 concentrations inside an urban tunnel can be calculated and forecasted from traffic intensity data and the composition of its circulating fleet. Also, the methodology presented can be used and adapted to calculate CO 2 concentrations in other urban tunnels for concrete carbonation analysis.
Abajo et al. (Sat,) studied this question.