Representative image of a milling machine grinding up worn asphalt on a quiet country road. Image Credits: ChatGPT
The Federal Highway Administration’s guide , ‘User Guidelines for Waste and Byproduct Materials in Pavement Construction,’ says that between 1984 and 1989 the state recycled the old asphalt on about 672 km (420 miles) of low-volume roads, the kind people call country roads. More than 75 percent of those projects were later graded fair or better. The federal guide states that this fix is used when the depth of the damage is about 4 to 6 inches (100 to 150 mm). In their 1991 Transportation Research Record paper, authors Todd Scholz, R. These roads generally carried fewer than 2,000 vehicles per day. The authors also reported construction costs of approximately $1.70 to $2.10 per square yard. A normal 2-inch asphalt overlay was about $2.75 to $4.00 per square yard. The method has been studied closely by the Oregon State Highway Division and Oregon State University since 1986.
After a couple of weeks of curing in favourable conditions, according to the federal guide, a hot mix overlay is added on top. The federal guide also said that taking old asphalt to a plant on small roads will likely cost more. Few things test a driver’s patience like a cracked, bumpy country road. In the 1980s, Oregon found a way to give these roads a second job. That’s not a perfect score. Still, it shows how recycling worn pavement can be a good, workable option for roads with lighter traffic. The method is called cold in-place recycling. It may sound complicated, but it’s actually pretty simple. Instead of removing old pavement, the worn-out top layer is ground up on site. The crushed asphalt is mixed with new asphalt in either liquid or foamed state without any heating. Then the mixture is placed back in place and compacted with heavy rollers. The work is done on-site, so there are no long truck trips to a far-away plant. Why quiet country roads were a good match Oregon kept this work on lightly travelled roads. Gary Hicks, David Rogge and Dale Allen explained that every Oregon project was partial depth recycling. Projects were also completed on county roads and US Forest Service roads. These figures reflect prices at the time. The authors concluded that it seemed to be a viable option for low-volume roads. This makes fixing the road in place all the more tempting.
