New roads out of old
A couple of roads near my house were repaved last month, and if you’ve ever had a child or a dog, you know how exciting that can be.
The first thing the dog noticed was all the trucks parked at the intersection of our road and the one that goes over the dam. We had to stop during our early morning walks in the dark so the dog could investigate by sniffing every tire. Satisfied that they were indeed trucks, she was off to more interesting adventures, namely checking in with the beaver couple near the beach. They’ve been working on a little construction project of their own.
The boy child noticed something even more interesting than tires: a huge machine, as wide as one lane of the road, with fire coming out of the bottom to melt the pavement it ran over.
“It was amazing, Mom,” he told me. “It’s the coolest machine ever.”
He is given to hyperbole, but to me the system is the coolest ever because it recycles the asphalt, right in place, as it resurfaces the road.
I called Keith Manz, the commissioner of public works for Saratoga County, to find out more about the technique, called heat scarification or hot, in-place recycling. The machine heats the asphalt, then mechanically breaks it up, adds oil and spreads it back over the surface of the road. A pavement roller follows to flatten and smooth everything out and it’s done. It’s a one-pass system.
The dog and I admired the little flecks of orange in the new surface — bits of paint from the traffic lines.
Manz said the system can be used on roads where the base is sound but where cracks are starting to make the surface rough for driving and affecting drainage. The recycled road will last around 18 years, depending on traffic and other conditions, he said.
“A road in Clifton Park, where there’s a lot of traffic, might last 12 years, maybe 15,” he said. “Up near you, those roads might last 20 years.”
Manz said the best thing about the system is that it’s “environmentally sound.”
Rather than breaking up old asphalt and trucking it away, to a landfill or a distant recycling plant, the old road is being made into a new road, right where it is.
For high-traffic areas, a more complex system is often used, one that heats the asphalt then digs down deeper, to the road’s subbase, and adds some more material to the old asphalt before returning it to the road. A topcoat, about an inch and a half thick, of new asphalt is then added. That’s a two-pass system, which has been used in Schenectady, too.
For Saratoga County, recycled road resurfacing actually costs more than traditional methods, Manz said. That’s because the county doesn’t own the in-place recycling equipment and uses subcontractors for roads resurfaced that way.
The Federal Highway Administration notes that in-place recycling minimizes the use of new materials and preserves the level of the road surface, which also saves money. Since the road isn’t getting higher every time it’s resurfaced, curbs don’t need to be raised and the clearances for bridges and overpasses remain the same. “Hot in-place recycling has proved to be a very economical pavement rehabilitation strategy which can be used to maintain existing pavements by reusing existing material,” the FHA says.
A few years back, the road in front of our house was resurfaced, using an even more basic technique: a thin layer of tar with a fine gravel layer on top of it. Manz calls it “chip seal” or stone and oil, and said it’s essentially a Band-Aid to extend the life of the road.
First the old road surface is cleaned and cracks are sealed. Then a truck comes through to spray a thin layer of hot liquid asphalt. Then comes the stone layer. And then the cars, trucks and bicycles drive around for 10 days or two weeks, pushing the stone into the asphalt. Finally a truck comes through and brushes up whatever loose stone is left.
It extends the life of the road, and allows highway departments to save some money by delaying paving. And in low traffic areas like mine, it holds up pretty well.
Saratoga County, like every other city, town and county in the country, is trying to maintain its roads while cutting costs. Manz said the plan right now is to resurface about 17 miles of road next year using one of two in-place recycling systems — that’s two or three of the eight road projects planned. “That can change,” he said. “We’re constantly reassessing.”
Keeping up roads isn’t easy. But reusing asphalt, right where it is, seems like a sensible way to go.
Margaret Hartley is the Gazette’s Sunday and features editor. Greenpoint appears in the Gazette’s print edition Sundays on the Environment page.
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