Life Cycle Assessment Comparison Between Traditional and Innovative Tunnel Retrofitting Approaches

Infrastructures have a strategic role for the societal development, making it possible to move thousands of people and tons of freight that everyday needs to reach their target destinations. Considering all the structural typologies involved in the infrastructure network, tunnels can be considered among the most critical. Dealing with the Italian infrastructure network, most of the tunnels need maintenance interventions to restore their service life, having been built, in their largest share, not later than fifty years ago. To this purpose, in an era of rapid urbanization and growing environmental concerns, an important advancement must be done in the tunnel retrofitting technology, by speeding up the overall process reducing costs and time, as well as increasing the sustainability of the interventions, by reducing the CO₂ emissions and by improving the waste management. A new methodology for the regeneration of existing tunnels by means of an automated process based on slip-forming fast strength gain Steel Fiber Reinforced Concrete (SFRC) has been recently proposed. The present work focuses on the comparison between this new retrofitting methodology and the traditional approach, with the use of ordinary steel rebars in the latter, highlighting the differences in the design, material properties and construction phases. The comparison made between the two approaches is referred to a specific case of study, the Ragnaia II tunnel in the A1 highway in the Italian roadway network, and has been performed through a cradle-to-gate Life Cycle Analysis (LCA), with particular concern on the Global Warming Potential (GWP) indicator. An additional analysis explores the influence environmental and socioeconomical influence of reduced traffic congestions, emphasizing dependence on the construction duration and highlighting the importance of extending the system boundaries beyond the gate.