Low Carbon Strategies for Reinforced Concrete Buildings:Insights from Life Cycle Assessment of a Swedish Case Study

Sammanfattning

The building sector is a major contributor to global carbon emissions, with reinforced concretestructures playing a significant role due to the high carbon intensity of cement production. In Sweden, where construction accounts for approximately 20% of national greenhouse gas(GHG) emissions, recent regulations such as the mandatory climate declaration of buildingshave intensified focus on life cycle-based carbon assessments for buildings.This thesis examines the life cycle carbon footprint of a semi-high-rise reinforced concretebuilding in Sweden and explores strategies to reduce the building’s climate impact. The fourpotential strategies investigated to reduce the building’s climate impact are: (i) improving ma-terial efficiency through the use of precast hollow core slabs (PHCS), (ii) using alternativebinders instead of conventional ordinary Portland cement (OPC), (iii) applying circular econ-omy practices via structural element reuse, and (iv) deployment of innovative low-carbon ce-ment (Evozero cement) produced with implementation of carbon capture and storage (CCS)technology. The study uses a Life Cycle Assessment (LCA) methodology according to the European stan-dard EN 15978, and follows cradle-to-grave and also cradle-to-cradle approaches. In additionto static LCA, a dynamic LCA which addresses the time profile and decay of GHG emissionsis also performed for the reinforced concrete building in this study. The system boundary forthe LCA includes the product stage (A1-A3), construction stage (A4-5), use stage (B1 and B2),end-of-life stage (C1-C4) and post-use stage (D). The life cycle carbon footprint is analyzedover a 50-year time horizon, considering the emissions of all the life cycle stages, includ-ing carbonation and maintenance activities linked to the building. The data used in the LCAare mainly from the Environmental Product Declaration (EPD) in the IMPACT Environmentalsoftware and the Ecoinvent database.The results show that the life cycle carbon footprint of the building is 120 kg CO2-eq/m2 whenthe calculations is based on static LCA approach. Regarding the potential strategies to re-duce the building’s climate impact, the analyses demonstrate that PHCS implementation couldreduce the building’s embodied carbon by 21%, while using Evozero cement achieves couldgive 60% reduction in production-phase GHG emissions, compared to conventional concretebased on OPC. The circularity strategy of the precast elements through reuse results in a carbonfootprint savings (-147.1 kg CO2-eq/m2) in the end-of-life module.The dynamic LCA approach reveals that building’s climate impact varies over time, reachingapproximately 175 kg CO2-eq/m2 when accounting for cumulative radiative forcing of GHGemissions. Hence, the dynamic LCA and the static LCA results for the studied building differsignificantly. The findings highlight how dynamic LCA captures essential temporal variationsin climate impacts that conventional static methods overlook, particularly the delayed effectsof end-of-life emissions and the long-term persistence of concrete’s carbon footprint. This thesis provides analytical evidence and strategies to considerably reduce the climate im-pact of reinforced concrete buildings, while offering a comprehensive methodological frame-work for life cycle-based carbon assessment of buildings. The findings underscore the signif-icant potential for GHG emissions reductions in reinforced concrete buildings through design,circular construction, and technological innovations in the concrete construction industry.