Demonstrating circular life cycle sustainability assessment – a case study of recycled carbon concrete

Abstract

To counter the high consumption of resources and environmental emissions in the construction sector, innovative materials such as carbon-reinforced concrete (CRC) are needed. CRC has the potential to lower the resource use and emissions of the construction sector and lead to a circular economy (CE). To understand the overall circularity and sustainability performance of such materials, holistic assessments are needed. This study demonstrated the application of the newly developed circular life cycle sustainability assessment (C-LCSA) framework that is based on CE indicators and life cycle sustainability assessment (LCSA). The framework was applied to an industrial floor that was made from recycled CRC scrap (R–CRC industrial floor) in its development phase – using both the concrete faction and the carbon fiber fraction. The material circularity indicator (MCI) was used for the circularity assessment. It was applied in parallel to a life cycle assessment (LCA), life cycle costing (LCC), and a social hotspot assessment, using the same functional unit and system boundaries. The cut-off approach used was in line with the technical system boundaries. The results showed that the contribution to the circularity of the R–CRC industrial floor was high (0.8184) due to the use of recycled material and the potential of being recycled again. The global warming potential (GWP, 167 kg CO2 eq.) was lower while the human toxicity potential (HTP) was higher compared to similar products. The production costs far exceeded the current price of a comparable product which might be related to the inefficiencies in the production at the laboratory scale in the development phase of the R–CRC industrial floor. Social risks were found for health and safety, as well as for the social acceptance of the floor due to technical uncertainties. Increasing the circularity further by only using recycled aggregates mostly showed positive effects on the environmental impacts. However, HTP and costs increased. General statements on the interlinkages between a higher circularity and positive impacts on sustainability performance cannot necessarily be made. Instead, a robust and holistic assessment of new products is needed. C-LCSA has demonstrated its effectiveness as a reliable framework for identifying interlinkages and trade-offs between the different sustainability dimensions and circularity. Further studies should be conducted to validate and demonstrate the C-LCSA framework on different products.