The impact of CO2 uptake rate on the environmental performance of cementitious composites: A new dynamic Global Warming Potential analysis

The sustainability of cementitious composites is currently analyzed by static methods, with little consideration of changes over time. In terms of Global Warming Potential (GWP), increasing the CO2 concentration in the atmosphere may negatively affect the planet. Therefore, estimating the imbalance between CO2 emitted and CO2 captured by these materials may be critical when assessing their environmental performance. This is the first study that proposes a new dynamic GWP method to analyze the sustainability of materials with the ability to uptake CO2 during their service life. For that, three main concrete mixtures are assessed: (i) a reference concrete with 100% Ordinary Portland cement (OPC); (ii) a concrete with 25% Fly Ash Class C (FA) + 75% OPC; and (iii) a concrete with 40% Ground Granulated Blast Furnace Slag (GGBFS) + 60% OPC. The investigation quantifies the GWP associated over a 100-year timeframe of a concrete mixture made at year 0 and based on four different CO2 uptake rates (reference, nano-modified A and B, and CO2 curing). Results demonstrate that while CO2-cured concretes exhibit the lowest GWP at year 0, nano-modified A concretes possess the lowest GWP associated at year 100 due to the acceleration of the CO2 uptake during their lifetime. Results also reveal that the GWP of nano-modified and CO2-cured concretes will be overestimated if the effects over time are not considered. Therefore, the dynamic methodology presented in this study should be employed when quantifying their GWP in cementitious composites. Moreover, this dynamic analysis could also be applied to other impact categories or even the complete holistic life cycle assessment.