Carbon footprint of self-healing geopolymer concrete with variable mix model

Carbon footprint analysis of geopolymer concrete can be used to determine its advantages over conventional Portland cement concrete. However, the influence of allocation assumptions has been neglected in previous geopolymer life cycle assessment studies. This research gap is addressed here through an analysis of the effect of allocation scenarios in the assessment of self-healing geopolymer concrete made from coal fly ash and ground granulated blast furnace slag feedstocks. In addition, an empirical, variable-mix “gray box” model was integrated into the life cycle assessment to allow different blends that meet product property specifications to be considered. The cradle-to-gate life cycle assessment was done using OpenLCA and MS Excel, using inventory data from databases and literature. The allocation assumptions are found to significantly affect the results, with carbon footprints ranging from 208.72 kg eq. CO₂ to 395.72 kg eq. CO₂ per cubic meter of concrete. Using allocation based on economic value, the price of coal fly ash has a greater effect than that of ground granulated blast furnace slag. The implications of this result on the commercial use of geopolymer concrete are discussed, as well as the potential application of the “gray box” approach as a generic methodology in life cycle assessment.