Transportation is one of the largest contributors to US carbon emissions. . When we think about what causes those carbon emissions, we might think of gas-guzzling cars on interstate highways. But the infrastructure of our entire transportation system – roads – release carbon emissions.
Last week, Madison’s Board of Public Works heard a presentation of an unusual place to cut emissions: concrete.
It was part of an effort from Wisconsin Concrete Pavement Association, a paving industry group representing Wisconsin concrete producers, manufacturers, and suppliers. .
Now, concrete should not be confused with cement, though usually concrete does contain cement. While cement is a specific material, concrete is a mixture of everything from cement, to limestone, to even ash.
Concrete is used in everything from buildings, to bridges, to sidewalks, to their most common use: roads. The Wisconsin Department of Transportation paves over 400 miles of roads with concrete every year. And with all of that concrete comes plenty of carbon emissions, mostly generated from the production of the concrete itself. And new low carbon concrete is already making great strides to address those emissions, says Kevin McMullen, of the Concrete Pavement Association.
“Right now, we are looking at a minimum 27% reduction, up to about 47% reduction in carbon emissions with the impact of the materials we are putting together.”
McMullen says low carbon concrete cuts CO2 in three big ways.
First, it just uses less concrete. An average road in Wisconsin has about 9 inches of concrete. But if that design were better optimized, and only 8 inches of concrete were laid, that would lead to an 11% reduction in materials, and thus an , as well as an 11% reduction in CO2.
Next, a new type of concrete that uses more limestone in the mix comes with the same strength but lower emissions.
This type of concrete, called Portland-limestone, is not new. It has been used in Europe for decades, and as of this year, the state Department of Transportation exclusively uses Portland-limestone concrete on all road projects.
Finally, we can change the materials that we use to make our concrete. Instead of using cement, which has a high carbon footprint, McMullen says that we can reuse things like ash created from coal power plants, which is usually disposed of in landfills. McMullen says that Wisconsin’s plan to phase out coal power plants would not really affect this plan.
“As you know, there is also a lot of work into how we can get rid of these coal fired power plants, and whether these resources will be available. Once the coal fired power plants go away, we will need an alternative material to use. I think the majority of it is going to be mining of old coal ash power plant dumps and processing that material for use in concrete. Another positive impact there, potentially, is that we are getting rid of, what could have been called in the past a toxic waste dump, and looking at how we can utilize those materials,” McMullen says.
But what about the structural integrity of low carbon concrete? Will it be able to withstand Wisconsin’s harsh winters? McMullen says that that isn’t an issue, because they stumbled on low carbon concrete while researching durability.
“We were so focused on quality, you know not having the concrete be impacted by the freeze-thaw, or making it non-reactive to deicing salt, or strong enough to carry any load that could be applied to it, that we got so focused on those engineering properties that, it was a few years later when we brought up ‘hey what we’re also doing here is reducing our carbon footprint.’ It’s a win-win for everyone. We’re making better concrete, I’m fully convinced of that, we’re making much better concrete than we were ten years ago, and the other win here is that we are reducing our carbon footprint as well,” McMullen says.
While more and more people are moving towards electric vehicles to cut down on their transportation carbon emissions, know that even the road below you is working to reduce CO2 in the environment.
Photo courtesy: Diego Jimenez / UNSPLASH
