A few weeks ago a road crew dumped a layer of gravel (not your normal gravel road gravel, a bit smaller and more light brown instead of gravel grey) on a road that I drive on every day to get to the highway. The road was just repaved about 18 months ago, and they only put the gravel on about a mile of the road (from one intersection almost to the where it passes under the highway).
The road is just barely outside of my city. It doesn’t have shoulders, just ditches on either side. When they repaved it last they finally painted lines down the middle of it.
The thing is since it sees a lot of traffic, most of the gravel has been pushed aside now and a good portion of the road is peeking through. What’s the purpose of the gravel? Does it do something for the blacktop? Is it an omen of road construction to come?
Are you sure they didn’t put down a layer of tar first? Here for cheap repaving they lay tar then the gravel for cheap repaving. They let the traffic force the gravel down into the tar.
I don’t think so Reeder. That’s what I originally thought but this gravel doesn’t seem to be stuck to anything. Driving over a freshly tarred road with gravel is pretty distinctive and I don’t hear the gravel being thrown up in to the wheel well nor have I found any flecks of tar on my car. I can still see the painted lines in parts so I don’t think it was tarred first. As I said in the OP the road was recently paved and it was in great shape (or so I thought) before the gravel was laid down. It’s not the only road in the area like this. Today I drove my kids to a birthday party a few miles further away from the city and that road is also like I described, except it just starts suddenly (not at an intersection), goes on for about a half a mile, then ends just as suddenly.
I’m guessing they are about to repave the roads but I’ve never seen this kind of prep work done before.
What most folks refer to as “asphalt” or “blacktop” is technically called “asphalt concrete” or “asphaltic concrete.” It’s comprised of variously-sized aggregate (rocks and sand, usually) bound together with asphalt cement, the black sticky stuff commonly called “tar” or, by those who work with it, “AC.” And, at least in these parts, the practice that Reeder refers to is called “chip and seal;” the old pavement is sprayed with a thin layer of AC emulsion and then coated with “chips,” usually crushed #8 or #9 limestone. The emulsified AC binds the chips to the old pavement and traffic serves to compact the new wearing surface.
As to what may have happened in Horseflesh’s example, I can only hazard a couple guesses, not having seen it. The most obvious is that it was a chip and seal job that went poorly, i.e. not enough emulsion applied, too much time elapsing between emulsion application and the spreading of the chips, or WAY too much in the way of chips, making it appear that “most of the gravel has been pushed aside.” It could be too that the purpose of the gravel was not as a wearing course at all, but to supply added traction, much in the manner of sand or cinders spread by crews in the winter to cope with snow and ice. The 18-month-old asphalt in that stretch may have been too “juicy,” meaning its AC content was too high, causing it too look shiny and provide poor traction.
And yes, as some of you may have guessed, I work in the highway construction field…
If the gravel is v.small stuff, it may be to soak up/cover an oil or diesel spill. That happened when a bus decided to go over, rather than round, a little traffic island near my house. Ripped out the sump - oil flowed down the hill for about 1/4 mile, quite impressive! Sand and grit got poured all over everywhere.
TBone2 may have something there. On the three roads I’ve encountered like this now, all of the sections where gravel was laid down were on slopes that are a little steeper than average. Maybe the 100+ weather we’ve had for the last several weeks has made these newly paved sections a little softer than desired and the gravel is there to keep the asphalt from buckling under heavy loads like garbage trucks and whatnot.