Concrete roads could deteriorate faster because of climate change

Add concrete roads to the list of items that could be imperiled by climate change.

A study by researchers at the University of Pittsburgh found that an expected increase in temperature extremes over the next 30 to 40 years — colder nights followed by warmer days — will cause faster deterioration of concrete roads. The study recommended the industry adjust the complicated formula it uses to make concrete, as well as the way it is used to combat changing weather conditions.

“These roads are not designed for climate change,” said Sushobhan Sen, a postdoctoral researcher who predicted that without changes concrete roads in the future will develop fatigue cracks much sooner than expected that cause their surface to deteriorate over time. With more advanced climate changes still several decades in the future, the study recommends additional research now to determine the right formula to make future roads more resilient to temperature changes.

Sen worked with Lev Khazanovich, the Anthony Gill Chair Professor of civil and environmental engineering in Pitt’s Swanson School of Engineering, on thousands of computer simulations concentrating on weather patterns in Phoenix and Boston to reach their conclusions. Their paper, “Effect of climate change and urban heat islands on the deterioration of roads,” was published in Results in Engineering.

Concrete — a mixture of sand, cement and stones with water — has been one of the most popular construction materials for thousands of years because of its strength and durability. The industry has periodically tweaked the formula to deal with changing conditions over time, and the coming climate changes call for another round of adjustments.

Khazanovich said it has long been established that asphalt can become soft with extreme heat and crumble in the freeze-and-thaw cycle of winter, but concrete road surfaces haven’t been studied as much. It’s been known that concrete will curl upward in extreme heat and in extreme cold it will curl downward, but this new research shows the damage to the road surface increases substantially when those extremes happen more frequently.

“You’re forcing the concrete to go back and forth more often with the extreme temperature changes, which will cause more cracking,” Khazanovich said.

Addressing this is particularly important, he said, because of the prominent role concrete plays in road construction. Concrete is used on only about 5% of roads, but those roads carry about 26% of all traffic, which means major roads used for travel and the movement of goods are most at risk.

That also means those roads carry a lot of heavy truck traffic, and that extra weight will combine with heat and cold extremes to hasten road deterioration, the professor said.

Although the university is planning additional research to determine the best formula and application of concrete, Khazanovich had some initial suggestions.

Rather than using one thick top layer of concrete that is 12 or 13 inches thick, he said, it would be better to use two separate layers to reach the same thickness. Research shows thinner layers have a less drastic reaction to temperature extremes.

Also, using lighter colors for concrete or materials with reflective properties such as tape will cause the concrete to absorb less heat and extend its life.

The study didn’t look at changes in concrete bridge decks, Khazanovich said, because the material is in a completely different atmosphere because it’s surrounded by air.

The American Concrete Paving Association has been preparing for climate change on road surfaces for several years, and work such as the Pitt research helps in the process, Eric Ferrebee, senior director of technical services, said in a statement.

“The takeaway is that there are a variety of variables, and research like this enables the pavement designers in our industry to address these trends during the design phase,” Ferrebee said. “This research supports that with the right design approach, concrete can achieve a 40-year life without significant repair or rehabilitation.”

Ferrebee said it is important for the industry to consider precipitation and other factors as the climate changes.

“Knowing how climate change will impact the performance of a material is the first step to designing for that change and mitigating its impact,” he said.

“Our role is to do our best to make choices from a design standpoint to combat this impact.”

John Becker, president of ACPA’s Pennsylvania chapter, said the research shows why it is “ever more critical” to prepare for the future. He noted the industry already has made changes such as reducing the amount of cement in the mixture by about 15% to reduce curling and shrinkage.

“This means that in areas where the expected daily temperature difference is expected to increase, understanding the research here is important for us to understand how we design for extreme temperatures,” he said.