Reducing embodied carbon dioxide of structural concrete with lightweight aggregate

An investigation was done into the development of lightweight-aggregate concrete mixes with lower embodied carbon dioxide emissions suitable for structural applications. Production requires the replacement of normal-weight coarse aggregate with a lightweight aggregate. Lytag was considered, which is a good-quality lightweight aggregate manufactured from fly ash. Lightweight-aggregate concrete for structural applications usually contains a high CEM I content owing to the requirements for workability, pumpability and strength. Consequently, its embodied carbon dioxide emissions are generally higher than that of normal-weight concrete. Mixes of LC30/33 class were developed containing up to 60% ground granulated blast-furnace slag, as well as limestone powder, and their fresh and mechanical properties were assessed experimentally. It was found that the embodied carbon dioxide of the investigated mix could be reduced by up to 40% when compared with that of neat CEM I lightweight-aggregate mixes containing Lytag aggregates and to 20% when compared with that of a mix that would be generally used in current practice in the UK containing 40% slag. It was also possible to reduce the CEM I content in the investigated mixes by approximately 40% compared with what would have been normally used