Statistical variation in the embodied carbon of concrete mixtures

This study presents a refined calculation of the embodied carbon of concrete mixtures via life cycle assessment (LCA) with an explicit focus on three innovations. First, probability distributions that represent process-related variability in the embodied carbon of concrete are calculated using a variety of life cycle inventory data sources. Second, the traditional concrete LCA system boundary (i.e., cradle-to-gate) is expanded to incorporate and analyze estimates of in situ carbon sequestration via concrete carbonation. Third, we analyze the impact of different transportation scenarios on the utility of using fly ash to reduce the embodied carbon of concrete. We use these data to heuristically determine the breakeven transportation distance for fly ash via trucking to be 2655 km for domestic sources of fly ash. However, when fly ash is imported from international sources, reductions to embodied carbon attributed to fly ash replacement can be negligible. The calculated breakeven maritime shipping distance for fly ash equals 15,110 km-beyond which, the anticipated embodied carbon reductions due to fly ash use in concrete are compromised due to transportation. The advancements described herein enable improved scenario-based decision-making for understanding, quantifying, and reducing the embodied carbon of concrete mixtures. In addition, the results highlight the importance of accounting for international transportation of fly ash in LCAs, especially given that domestic sources of quality fly ash are expected to continue to decline and imports are expected to increase in many parts of the world over the next few decades. (C) 2020 Elsevier Ltd. All rights reserved.