Environmental assessment of a disruptive innovation: comparative cradle-to-gate life cycle assessments of carbon-reinforced concrete building component

Abstract

Purpose: How to build in more environmentally sustainable manner? This issue is increasingly coming to the fore in construction sector, which is responsible for a relevant share of resource depletion, solid waste, and greenhouse gas (GHG) emissions. Carbon-reinforced concrete (CRC), as a disruptive innovation of composite building material, requires less resources and enables new forms — but does it make CRC more environmentally sustainable than steel-reinforced concrete (SRC)? This article aims to assess and compare the environmental impact of 45 material and production scenarios of a CRC with a SRC double wall. Methods: The life cycle assessment method (LCA) is used to assess environmental impacts. The functional unit is a double wall and the reference flows are 1 m3 for concrete and 1 kg for fiber. CML methodology is used for life cycle impact assessment (LCIA) in the software GaBi© ts 10.0. A sensitivity analysis focuses on electricity grid mixes, concrete mixes, and steel production scenarios. Results: The midpoint indicator climate change respective global warming potential (in kg CO2e) ranges between 453 kg CO2e and 754 kg CO2e per CRC double wall. A comparable SRC double wall results in emissions of 611–1239 kg CO2e. Even though less raw material is needed for CRC, it does not represent a clear advantage over SRC in terms of climate change. In a comparison, the production of steel (blast furnace vs. electric arc furnace vs. recycled steel) and the choice of cement type are of decisive relevance. For concrete mixes, a mixture of Portland cement and blast furnace slag (CEM III) is beneficial to pure Portland cement (CEM) I. For fiber production, styrene-butadiene rubber (SBR) has an advantage over epoxy resin (EP) impregnation and the use of renewable energy could reduce emissions of fiber production up to 60%. Conclusion: CRC requires less material (concrete cover) than SRC, however, exhibits comparable CO2e to SRC — depending on the production process of steel. In the future, fiber production and impregnation should be studied in detail. Since in terms of climate change neither wall (CRC vs. SRC) clearly performs better, the two other pillars of sustainability (economic and social, resulting in LCSA) and innovative building components must be focused on. Graphical Abstract: [Figure not available: see fulltext.].