Effect of Transportation on Environmental Burdens of Blended Cements Made with Imported and Domestic Supplementary Cementitious Materials

Cement accounts for 7% to 8% of global anthropogenic emissions. An effective strategy to reduce concrete emissions is partially replacing cement with supplementary cementitious materials (SCMs) such as coal fly ash and slag. However, the available supply of these industry byproduct SCMs is rapidly diminishing in the United States. Consequently, they are transported from distant regions. However, the effect of transportation distance on the global warming impact (GWI) of SCM-blended cement remains unknown. A cradle-to-gate life cycle assessment showed that the GWI of 1 metric ton (tonne) of blended cement with 20% coal fly ash imported from Asia is approximately 3% lower than 1 tonne of cement based on the U.S. national average GWI for cement. The reduction was almost 14% when coal fly ash was from Texas and approximately 17% when a locally produced natural pozzolan was used. The results show transportation could significantly affect the environmental benefits of blending cement with SCMs.