National Center for Sustainable Transportation

Recent California regulatory efforts, United States goals, and industry roadmaps all target net-zero greenhouse gas (GHG) emissions from the cement and concrete industries within a few decades. While changes in production of cement and concrete, including varying constituents, can greatly reduce GHG emissions, carbon dioxide removal (CDR) will be needed to meet this net-zero goal. Hydrated cement in concrete can carbonate (i.e., form carbon-based minerals with atmospheric CO2) and thus act as a CDR mechanism. This process occurs faster with a large surface area, such as crushed concrete at its end-of-life (EoL), which can be uniquely leveraged by transportation infrastructure projects. In this work, a literature review of key parameters that can facilitate desired CO2 uptake for transportation projects at their end of life is conducted and an initial meta-analyses of data from the literature to inform CO2 uptake for individual projects is performed. Initial considerations for what concomitant impacts may arise from this process are presented. Finally, experiments to fill a key gap in understanding how thin crushed concrete must be spread to maximize uptake reactions are conducted. Cumulatively, findings will inform whether carbonation can be implementedin a way that would support policies that include carbonation as a route for reducing emissions from cement-based materials in transportation applications

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