Climate limit state (CLS) for building structures: A possible companion of ULS, SLS and durability limit states

The production of building materials and here especially of concrete and its constituent cement is afflicted with substantial CO₂ emissions, currently amounting to more than 8% of the world’s total anthropogenic CO₂ footprint. Following the world’s climate goals agreed upon in the UNs climate conferences, a pronounced reduction in emissions from cement and concrete production is mandatory. Substantial progress in developing emissions-reduced concretes have been reported in the literature. However, these solutions are only hesitantly being used in practical applications. This on the one hand has to do with the unknown risks going along with new concrete mixtures such as a reduced robustness. On the other hand – and more importantly – incentives and requirements to use new solutions are lacking. This is especially true when looking into the design process of concrete structures, where ecological requirements currently only play a minor role or are completely neglected. To counteract this negligence, within this paper a new limit state termed ‘Climate Limit State (CLS)’ is proposed, in order to amend the currently established limit state considerations Ultimate Limit State (ULS), Serviceability Limit State (SLS) and Durability Limit State. The CLS considers the CO₂-emissions resulting from the production of a defined concrete member and references them to the potential service life of the structure. The limit state is introduced by comparing this result to a reference state and additionally introducing mankind’s CO₂-budget to limit the global warming. With the proposed CLS, risk for the structure as well as the users resulting from climate change can be considered.