The California Department of Transportation (Caltrans) this week announced it is approving the use of low-carbon cement to help reduce the carbon footprint of the state's transportation system.
Caltrans plans to advance the use of portland limestone cement (PLC) in order to generate less carbon dioxide in road construction and maintenance projects with the same high performance standards at a slightly lower cost, the department said in a news release.
“Using low-carbon cement can cut Caltrans’ concrete-related carbon dioxide emissions annually by up to 10%," Caltrans Director Toks Omishakin said in a statement. "This is a big step in supporting California’s efforts to achieve carbon neutrality by 2045.”
According to Caltrans, cement is typically produced by mining, grinding, and heating limestone in industrial kilns to temperatures as high as 2,820°F. 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 carbon dioxide. PLC contains less clinker, the department says.
In 2017 alone, Caltrans used 325,000 tons of cement to upgrade the state highway system. Switching to low-carbon cement has the potential to reduce carbon dioxide emissions by 28,000 tons a year—the equivalent of removing more than 6,000 cars off the road. 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 Oregon State University, which concluded that PLC is equally suitable for Caltrans’ construction projects as ordinary cement with a reduced carbon footprint.
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.