Impact of Transportation of Supplementary Cementitious Materials on Concrete-Embodied Carbon: A Life Cycle Assessment for Sustainable Material Sourcing

Abstract Concrete production is a significant source of greenhouse gas (GHG) emissions, largely due to the high carbon intensity of portland cement (PC). Supplementary cementitious materials (SCMs), such as fly ash (FA), are widely used to reduce the embodied carbon of concrete. However, the environmental benefit of SCM substitution depends not only on material composition but also on transportation distance and mode, which can offset potential emission reductions. This study investigates the transportation thresholds at which SCM substitution remains environmentally beneficial. A cradle-to-gate life cycle assessment (LCA) was conducted using 1 m 3 of concrete as the declared unit, considering FA replacement levels of 20%, 30%, and 50% and transportation distances ranging from 30 km to 13,000 km under truck-only and combined truck–rail scenarios. Results show that higher FA replacement levels can maintain net GHG reductions across longer transportation distances due to reduced cement demand. Sensitivity analysis indicates that SCM transport remains environmentally advantageous up to approximately 1,600 km when considering equivalent cement substitution impacts, while transport beyond this threshold can offset emission savings depending on logistics conditions. These findings highlight the importance of integrating material sourcing and transportation logistics in concrete mix design decisions and provide a practical framework for evaluating SCM supply strategies in low-carbon infrastructure development.