This is why you shouldnt do drugs because it makes you think of this stuff…but anyway i was driving down a steep hill watching the construction workers pouring a new road surface. I was watching it run out of the truck and started thinking about the stuff…even after solidifying does it still run…much like glass does?? Discounting wind, temp changes and other wear, would all the asphault <already fully made into roadtop> eventually run down a hill and puddle at the bottom?? Even if it took 5000 years? Or a million? Or is the network of the road solid enough to hold itself together and have a greater force than that of gravity. I realize this is kinda strange but where ELSE would you ask this stuff???
Glass doesn’t run once it’s cooled to room temperature. Don’t know about asphalt.
Well, you might try GQ…
As far as the OP, I doubt that asphault would flow downhill, but I’m no expert.
There are many different grades of asphalt depending on the intended usage. Some grades of newly laid primary road asphalt can weaken and become soft(er) if the temperature gets too high (but we’re talking 110+ degrees in the shade kind of temperatures) but even so it will still not “flow” in the manner in which you describe.
Dunno about downhill flow but I’ve seen asphalt deformation due to sheer weight. At certain intersections on Los Angeles streets with lots of truck traffic, the asphalt is squashed into big, ultra-slow-motion “waves”. The overlying white paint is similarly rippled and distorted, kind of a psychedelic effect. Maybe the high summer temperatures help it along.
[hijack]
AndrewL: Glass doesn’t run once it’s cooled to room temperature.
Are you sure? In the first book (I don’t have the online column handy), Cecil said,
and I’d be surprised if there wasn’t some deformation over time. [/hijack]
Here is the column in question about the glass.
And yes, asphalt does continue to flow. Ever wonder why roads eventually deteriorate, and people’s driveways look nice for years? People seal their driveways, which in effect is replacing the asphalt that has heated and leached into the soil. If you dig under a freshly removed asphalt plot, you will find a layer of soil soaked with black asphalt residue. Sealcoating replaces the asphalt lost due to leaching, and before you ask, they don’t do it to (most) highways because sealcoating makes the asphalt dangerously slippery, not a problem with most driveways or parking lots.
Billy, thanks for the link ( that’s a helluva topic it got paired with), and for the info.
So AndrewL is correct, practically speaking.
No, asphalt won’t flow in it’s “hardened” state. And it isn’t really poured out of a truck, asphalt is approx. 94% gravel. At an asphalt plant gravel is heated to remove all the moisture (usually about 2–4 % of the total weight) and then asphalt oil is mixed in which essentially replaces the water. I’m not up on today’s technology, but when I ran a batch plant 10+ years ago, we mixed 115 lbs. oil to 1885 lbs. 1/2"gravel, or 5.75% oil, at 350 F. As ** astro** said, there are many different grades.
When the asphalt is laid on the road it is compacted, and when it cools it is ready to drive on.
Billy Rubin, roads deteriorate and driveways look nice for years because of the vast difference in traffic. Seal coat is used on driveways because paving is seldom perfect and people demand perfection when they are paying big bucks. The seal coat covers up all the small cracks in the surface and if applied regularly will add to the life of the driveway, but not significantly if the job is well done in the first place. This type of seal coat isn’t used on a highway mostly because it wouldn’t last, besides the slipperiness factor (chip seal is the highway version).
And before asphalt is laid the base is prepped: the gravel or old pavement is sprayed with a thinner oil that soaks into it a little to help the new asphalt adhere to it.
This thread is more appropriate for the General Questions forum. Moving it there.
At my old HS, during the summer when it got up round 35 - 40 C, you could find “puddles” of asphalt on the road which you could twist with your foot to make a mark. I would say it had the consitency of bubble gum on those days so, yes, it would run if there was a hill I guess.
Donkey: Yes, I understand what you are saying.
I am referring to “asphalt”. Asphalt is a bituminous material which holds aggregate (in your example, gravel) into a coherent mass. A similar material is Pitch; pitch is hard enough to drive nails with in its cool state, but if you place a feather on it and wait a week or so, the feather will leave an imprint in the pitch. Because it is flowing.
Asphalt, the bituminous material, does indeed contine to flow, except under extremely cold temperatures. Sometimes it takes the aggregate with it,depending on the slope.
And sealcoating has one purpose, and that is to replace the asphalt which has leached out of the aggregate; every can of sealcoat you see clearly states that it’s purpose is NOT to seal cracks, it instead expects you to fill the cracks first then lay down the sealcoat. Look closely at your blacktop driveway: Just after sealcoating, the bitumen is right to the top of the aggregate; years after sealcoating, most of the aggregate is exposed, and if allowed to leach out without being replaced, will eventually leach out altogether, leaving only the gravel. Anyone who has ever ridden a motorcycle on an old blacktop street knows you occasionally run into a patch where the top layer of aggregate has loosened; a very dangerous thing for a bike.
If the use is what causes the road (or driveway) to deteriorate, why is it that when I moved into my house (after it had sat abandoned for five years) the top surface was white and starting to loosen? Age, heat, and gravity leach the asphalt out of the aggregate. there was no traffic to do anything to it.
Aside: the “semisolid” nature of asphalt is what provides the “cushioning” effect most runners prefer to concrete. The asphalt binder allows the aggregate to shift slightly, which makes an asphalt surface more forgiving than concrete.
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