Following testing by the College of Engineering-Oregon State University (OSU), the California Department of Transportation (Caltrans) announced January 25, 2022 that it is approving the use of low-carbon cement to help reduce the carbon footprint of California’s transportation system. Caltrans is responsible for more than 50,000 miles of highways and freeways in California. By advancing the use of portland limestone cement (PLC), Caltrans’ road construction and maintenance projects can generate less carbon dioxide (CO2)—the primary greenhouse gas contributing to global warming and climate change—with the same high performance standards at a slightly lower cost.
Toks Omishakin, Director-Caltrans, stated, “Using low-carbon cement can cut Caltrans’ concrete-related CO2 emissions annually by up to 10%. This is a big step in supporting California’s efforts to achieve carbon neutrality by 2045.”
Portland cement was developed in England in the early 1800s and is the most common type of binder used in concrete. Caltrans noted that in 2017 alone, it used 325,000 tons of cement to upgrade the California highway system. Shifting to low-carbon cement can potentially reduce carbon dioxide emissions by 28,000 tons a year – the amount produced by 6,000 cars. Caltrans expects that the reduced energy needs associated with PLC production will make the cost similar or slightly less when compared to regular cement.
The new low-carbon cement standards are based on Caltrans-funded research conducted at OSU, which concluded that PLC is equally suitable for Caltrans’ construction projects as ordinary cement with a reduced carbon footprint. Throughout the review process, Caltrans worked closely with its partners at the California Air Resources Board and industry experts and stakeholders, such as the California Construction and Industrial Materials Association and the California Nevada Cement Association, to draft the new standard specifications. The PLC approval was based on Caltrans-funded research by Jason Weiss, Professor, Civil and Construction Engineering-OSU and the Miles Lowell and Margaret Watt Edwards Distinguished Chair in Engineering-OSU.
The research concluded that PLC will work just as well as portland cement for Caltrans projects, while being more climate friendly and costing a bit less. Globally, the production of portland cement is estimated to be responsible for as much as 8% of the carbon released into the Earth’s atmosphere.
Weiss said, “Cement accounts for such a high level of emissions because of how extensively it’s used around the world. We use 10 times more concrete than any other building material, and it is becoming more and more urgent in the face of climate change that we reduce the carbon footprint of infrastructure materials.”
Weiss explained that cement is usually produced by mining, grinding and heating clay and limestone in industrial kilns to temperatures as high as 2,820° Fahrenheit (1,550° Celsius). The process alters the rock’s chemistry and creates “clinker”—the basic component in nearly all types of cement—but also generates large quantities of the greenhouse gas carbon dioxide (CO2). PLC contains less clinker. The PLC process uses up to 15%, or 10% more limestone than ordinary cement, and results in less clinker, with the environmental upshot being a smaller amount of carbon emissions.
“Our goal is always to produce better, more sustainable, & longer-lasting concrete. We don’t want to do research that sits in a book on a shelf. We want to impact standards, specifications, & construction practices that move the civil & construction engineering profession forward.”
— Dr. Jason Weiss
In 2010, Caltrans changed its concrete standard specifications to increase the use of sustainable alternatives in transportation projects, an initiative that helped spur a shift in concrete production throughout the state. Caltrans will continue to work with the California Air Resources Board to reach the state’s goal and achieve net-zero emissions from the cement sector by 2045.
For the press release, please go to: https://dot.ca.gov/news-releases/news-release-2022-003
For the OSU Press Release/Article: https://today.oregonstate.edu/news/low-carbon-cement-tested-oregon-state-approved-california-highway-projects
For Caltrans, please go to: https://dot.ca.gov
For questions, please contact: Tamie McGowen | Phone: (916) 956-0633
Photo Home Page: https://mantledev.com/projects/strategies-for-low-carbon-concrete-primer-for-federal-government-procurement/