The Superpave Center at Purdue does a lot of testing. Right now they are looking at a different kind of rock to use in asphalt pavement.
"We are looking at a new aggregate source. We’re looking at what’s called a trap rock, an igneous rock that we don’t have in Indiana, because we have sedimentary rocks like limestone and dolomites," explains Rebecca McDaniel from the North Central Superpave Center at Purdue.
Other things now being used to save on the cost of building or maintaining a road are recycling old asphalt pavement, recycling the asphalt from used roofing shingles, and using left-over steel slag in place of rocks.
"There are actually some projects in Illinois that they call ‘total recycle,’ because they use steel slag aggregates, they use maybe 40 or 45% reclaimed asphalt pavement, they use shingles," McDaniel explains. “There was a study by the Environmental Protection Agency that showed reclaimed asphalt pavement is the most widely recycled material we have. It far exceeds newspapers, aluminum cans, glass and so on. In fact, it’s probably as much as all of those put together on a tonnage basis.”
Asphalt and sealers use up our natural resources, so recycling makes sense. But what if we could literally grow some of our road products? That would make them more environmentally friendly and less costly.
Research at Purdue could make this a reality someday.
“This is part of what you’ll get when you crush a soybean," explains Dr. Jason Weiss, a professor of civil engineering at Purdue, as he holds a container full of the liquid.
"This would help with the curing process to help keep some of the water inside of the system. What we’re really looking at and exploring right now is if we can use this on concrete to help keep some of the water out long-term, and some of the salt out long-term, because once the micro-structures form, if we can keep water out of the system, we can make it much more resistant to freeze-thaw damage, or to scaling damage when people place de-icing salts on the surface.”
“At least one group has actually used swine manure – I know, everyone laughs when they hear it, but it’s true – and turn that into something that has properties like asphalt," explains John Haddock, an associate professor at Purdue. “There are other people that are working with bi-products that come from combustion of corn stover or wood chips and things like that. When you burn those, part of the by-product you have that is left over can also be refined into something that’s also like asphalt."
“It’s something to replace asphalt binder in general, because it does have some desirable properties, but it comes from crude oil,” Haddock explains.
And while researchers are finding ways to cut costs and use improved material to add a few years to the life of a road, the really big discovery may still be out there somewhere.
"Can you take a road and make electricity from it?" Haddock asks rhetorically. "What if it were a linear solar collector? What if every road you had was a solar collector? You wouldn’t need to build big solar farms.”
"We have shown in the lab you can do it."