Sensitivity of Concrete’s Embodied Carbon Emissions to Cement Direct Carbon Intensity and Material Transportation

AUTHORS: Cooper, M.A.; and Mukherjee, A.

ABSTRACT: The objective of this study is to isolate the relative contributions of cement’s global warming potential (GWP) and the impact of transporting concrete materials on the A1-A3 GWP of a concrete mixture. Environmental product declarations (EPDs) are becoming more commonly used by the cement and concrete industries. EPDs present single point estimates of mid-point indicators, such as GWP, without appropriately indicating the associated uncertainty. However, EPD uncertainty is a concern clearly demonstrated by the General Services Agency (GSA) who published a document associating a fixed amount of error with the estimated GWP of a concrete product. Infrastructure owner agencies are beginning to collect cement and concrete EPDs and using these to inform benchmark mid-point indicator values for their projects. However, the benchmark values typically provide average information and do not address uncertainty, therefore failing to deliver GSA’s expectations. Therefore, this research presents the development and utilization of the spring-and-dashpot model framework. This framework explores the sensitivity of GWP to different cement direct carbon intensity values and materials transportation distances using a field dataset of concrete mixture designs from across the country. This study informs owner agencies of the range in GWP of up to 80 kg of CO2-eq per m3 of concrete and of the changes in GWP that may occur if one of these significant parameters (cement direct carbon intensity or transportation distance) changes.