A comparative cradle‐to‐gate life cycle assessment of carbon fiber‐reinforced polymer and steel‐reinforced bridges

Abstract

AbstractCarbon fiber‐reinforced polymer (CFRP) has proven to be an excellent replacement for conventionally used steel in the construction industry. This is especially relevant in bridge engineering, where its corrosion resistance, low weight‐to‐strength ratio, and outstanding fatigue properties can be put to appropriate use, for example, to prestress the bridge girders. These properties are a huge part of the success of prestressed CFRP bridges, which tremendously increase the structural and material efficiency and hence help facilitate the construction of slender and durable bridges. However, apart from the structural performance of the bridges, the aspect of sustainability (environmental viability, economic feasibility, and social acceptance) plays a vital role in determining the overall efficiency. Prior studies have illustrated that the CFRP reinforcements in themselves are relatively unsustainable as compared to conventional steel reinforcements. However, owing to the extraordinarily high material efficiency generally associated with structures built with CFRP reinforcements, it can be hypothesized that these are equally or even more sustainable as compared to their counterparts. In this study, an aspect of sustainability, namely, environmental impact, is addressed. As a first part of the study, cradle‐to‐gate CO2 emissions for conventional building materials and CFRP have been thoroughly reviewed and documented. Attributed to the heterogeneity of the data available for CO2 emissions from CFRP reinforcements, three scenarios (favorable, realistic, and unfavorable) were drawn up. Based on these values, a comparative life cycle assessment was undertaken for two bridge systems, namely, Rosensteinsteg II (already constructed) and an overpass over German highway A‐20 (design in process). For each bridge system, two separate variants with steel and CFRP reinforcements were considered. For Rosensteinsteg II, a reduction of approximately 28% was observed in the CO2 emissions (favorable global warming potential values for CFRP) once the steel was replaced with prestressed CFRP. A total of 18% reduction was observed for the A‐20 bridge with CFRP reinforcements. With the help of the current study, it could be concluded that, especially for bridges not experiencing heavy vehicular loads, prestressed CFRP bridges are the most environmentally feasible option.