Carbon dioxide equivalent (CO2-e) emissions: A comparison between geopolymer and OPC cement concrete

Concrete for construction has traditionally been based on an Ordinary Portland Cement (OPC) binder. Geopolymers, an alternative binder based on fly ash (a fine waste collected from the emissions liberated by coal burning power stations) that is activated by an alkaline activator, have potential to lower the significant carbon footprint of OPC concrete. This paper presents the results of comprehensive carbon footprint estimates for both geopolymer and OPC concrete, including energy expending activities associated with mining and transport of raw materials, manufacturing and concrete construction. Previous studies have shown a wide variation of reported emission estimates: the results of this study are benchmarked with data from those studies.

► Ordinary Portland cement (OPC) has high embodied energy arising from manufacturing.
► Carbon footprint of geopolymers, an alternative binder to OPC, was estimated.
► CO2-e of geopolymer concrete is 9% less than OPC: unlike past studies (26–80%).
► Key factors for high CO2-e of geopolymers: energy expended on alkali activators.
► Geopolymers need high temperature curing for strength: a further source of CO2-e