Outside civil engineering and construction circles, concrete doesn’t get much attention. It isn’t something likely to be debated in Congress, but new developments in this ancient material may make a small dent in how much governments have to pay to build and maintain transportation infrastructure.
Logic says the government could save taxpayer dollars by having a concrete bridge deck that lasts 20 years instead of 10.
“There are concrete technologies available now that can help us do a number of things related to long-term durability,” said Tim Tonyan, vice president of CTLGroup, a materials science consultant in Skokie, Ill.
The problem, he said, is federal or state departments of transportation have budget constraints that override the long-term benefits of concrete construction. It costs more upfront to place concrete paving, even if it’s cheaper than asphalt in the long run.
“DOTs are faced with this Faustian decision: I have money to spend this year, and I have 100 miles of pavement to work on,” Tonyan said. “Do I satisfy the public’s demand for doing something right away, or do I do something in the long run that is going to be more durable and cost-effective?”
That scenario came into play over the past two years, when critics say government infrastructure funding through the American Recovery and Reinvestment Act focused too much on such things as highway resurfacing and not on long-term improvements.
That’s because, at its core, ARRA’s goal was to stimulate job creation, so money was available for “shovel-ready” projects that could be funded and completed rapidly.
“States had to do things that were ready to go,” Tonyan said. “If they had the time to think about how they put the money into long-term solutions, they might have had a different result.”
Concrete dates back to Roman times. Portland cement, one of the basic ingredients, was patented in England in the early 19th century, and its use for highways in the U.S. started early in the 20th century.
Research money to find ways to improve concrete varies from year to year. “The Golden Age of research and development was throughout the 1940s and 1950s,” Tonyan said, and into the mid-1960s. It’s no coincidence the amount of research paralleled the construction of the interstate highway system.
Much of the money for research now comes from the federal government. The Federal Highway Administration has sponsored research into “high performance” concrete paving for more than 20 years. It also supports research into effective composite paving, where layers of concrete can be topped with asphalt.
“The interstate highway was a big driver. Once that infrastructure was built up, the research tapered off,” Tonyan said. “Now we’re seeing a resurgence of interest, because we look back at these structures that are 50 years old, and try to figure out either how to repair them or replace them cost-effectively.”
The past decade has seen growth in the environmental benefits of concrete, said Matthew D’Ambrosia, a project manager with CTLGroup. “There has been a drive in the industry to make concrete more sustainable and make it competitive among green building materials.”
Portland cement manufacturing, a huge source of carbon dioxide, is anything but green. Current research into alternative materials is looking at fly ash, a byproduct of burning coal at power plants, and slag, a byproduct of steel manufacture. Such alternative materials could replace approximately 50 percent of the amount of Portland cement.
“You can take out the Portland cement, and replace it with something that would otherwise end up in the landfill,” D’Ambrosia said. There are also chemical additives on the market and in testing that can be added to the concrete mix. Combined with the right chemicals, fly ash can be made to set as hard as any concrete.
With Congress inching closer to a new six-year surface transportation authorization, it’s unclear how much concrete’s new technology would contribute to reducing the estimated $500 billion it would take to repair and rebuild the infrastructure President Obama says is vital for the country’s economic position in the world.
“If we can do things to make concrete last twice as long, and in today’s dollars, you’re making a huge impact,” Tonyan said. The problem is there are still too many unknowns to provide states the assurance they want.
“I think the engineering and materials science communities can predict performance to a level that will show benefit in the long run,” Tonyan said. “Whether you’re talking about concrete or asphalt, or polymers and metals, we are starting to see the industry shift toward broader thinking and longer-term analysis. We’ll start to see more long-term management of infrastructure, and keeping up with repairs.”
The American Society of Civil Engineers issues a biannual “report card” that reflects its assessment of the nation’s infrastructure. Last year, infrastructure nearly got a failing grade. “We don’t want to get 50 years down the road again and find out that we once again have to deal with a D-plus report card from ASCE,” Tonyan said. “We don’t want to get back to that point.”
Contact R.G. Edmonson at email@example.com.