On 6/15/2014 4:56 AM, Richard Aiken wrote:
On Sat, Jun 14, 2014 at 7:05 PM, sjard <sjard@emerytelcom.net> wrote:
"Road crews have been known to bury foil-wrapped potatoes under fresh asphalt, then come back and exhume them several minutes later . . . "
Having worked on a road crew, I'm not entirely sure how that would work. Hot mix asphalt comes out of the mix plant at between 450 to 500 degrees fahrenheit, and has to be laid down and shaped before it drops below about 300 degrees. If it drops below about 275, it won't compress properly with the rollers and you have to scrape it back up and usually dump it (it's very hard to reheat properly). It cools rapidly; you've only got about 15 minutes with a 5 ton load from plant to worked before it cools too much.
 
 
I'm not sure what you mean by "plant."
 
When road crews around here work, the asphalt comes to them in regular large dump trucks, then gets tipped into a big, slow-moving, one-lane-plus-wide machine with a large hopper on the back which does the pre-roller spreading. Given our *horrendous* local traffic, there is NO way these dump trucks are making it from a fixed plant somewhere to a roadwork site in  only 15 minutes. So those big crawlers must be able to re-heat fairly cool asphalt to application temps.
 
Assuming this is correct, I can see "accidentally" bleeding a bit of extra hot asphalt off onto the road shoulder, then coming back when it's cooled off to ~275 and shoveling it back into the hopper (minus your lunch).
 
Richard Aiken


Plant as in the facility that heats and mixes the hot mix. And yes, most of the really big crawler types are either concrete machines, or have integral heating and mixing parts. But the crawler types don't have feed for  a standard dump truck feed (where the truck would back up and dump into the hopper), most of the large ones have a precursor vehicle that the trucks dump the hot mix into a line, then this other thing (don't know what it's called, never worked with one) then picks up the long thin pile of hot mix and uses a conveyer belt thing to move it to the hopper. 

Also, there are mobile mix plants for jobs that are far enough away from a static plant.