Institute for Transportation

Transportation agencies across the nation are striving to quantify the environmental impacts and carbon emissions of their pavement materials as part of their overarching endeavor to construct and maintain sustainable pavement systems.

However, before they can quantify their impacts, transportation agencies need tangible strategies to start their projects off successfully by reducing the carbon emissions of their transportation construction materials.

To help agencies reduce the environmental impacts incurred during the production of paving concrete before it leaves the concrete plant, the National Concrete Pavement Technology Center (CP Tech Center) recently published the Guide for Reducing the Cradle-to-Gate Embodied Carbon Emissions of Paving Concrete.

Cradle to gate describes the earliest portions of a product’s life cycle, from initial material production—such as aggregate mining—through product manufacture at the concrete plant. Embodied carbon emissions are a measure of a material’s cradle-to-gate global warming potential, which is estimated from the energy used to extract, process, and transport the raw materials as well as the emissions generated from the manufacturing processes.

The strategies presented in this guide can serve as an important early step in bringing attention to the need for broader carbon reduction during a pavement system life cycle, while implementing quantifiable change at the outset of a project.

Specifically, the guide presents five strategies that can be used separately or in combination and that can result in measurable reductions in the cradle-to-gate embodied carbon emissions of paving concrete. The strategies are summarized as follows and expanded upon in the guide:

1. Target the cementitious binder.
2. Target the concrete mixture to optimize binder content.
3. Reduce the cradle-to-gate embodied carbon emissions of aggregates.
4. Target mixture performance requirements.
5. Consider other factors.

Each strategy is accompanied by an Implementation Table that provides background information about the strategy, a high-level overview of how the strategy can result in lower embodied carbon emissions, and actions and steps that can be taken to implement the strategy. The guide also provides a detailed example method to estimate the embodied carbon emissions of paving concrete.

“Most of the strategies presented can be implemented immediately to produce positive short-term improvements while broader, longer term actions are planned,” reads the guide. “Early successes achieved during the production stage can be built upon to further reduce embodied carbon emissions in later stages of the concrete life cycle.”

The strategies outlined in the guide are well within the scope of the target audience. That is, the agency personnel involved in specifying concrete paving mixtures, their consultants, and contractors and concrete mixture designers can immediately implement these strategies as part of their concrete paving projects going forward.

However, agencies’ ability to reduce the embodied carbon of concrete in a given location depends on existing practices and the availability of concrete-making materials, meaning in some cases more dramatic changes may be needed.

The guide was published with funding from and as part of the Federal Highway Administration (FHWA) cooperative agreement Advancing Concrete Pavement Technology Solutions.

This guide and other publications produced as part of the ongoing cooperative agreement are available at the project page. Additionally, a recent webinar focused on the topic is available on the CP Tech Center’s Webinars and Videos page.