On 8/30/2010 1:56 PM, Micajah wrote:


"Bob" wrote in message
...
Hello,

Was just wondering about this.

It is pretty well accepted, apparently, that a new asphalt driveway
for a residence should be laid over about 4" to 6" of gravel.
Never over soil directly.

Why ?

The hot, liquid, asphalt I would pretty much think makes the gravel
into one, solid, "clump" underneath (the asphalt).
So, it's hard to see that any improved drainage results.

Increased "stability" perhaps ? If so, how ?

So what does the gravel add as a benefit over just laying the asphalt
on top of well compacted soil ?

Thanks,
Bob

The folk responding about asphalt are right, so I won't duplicate their
effort. However, you might also be recalling the old Macadam road
technique with the modern version. http://en.wikipedia.org/wiki/Macadam

In my home town, many of the streets were Macadam and they did very
well. Occasionally, the street department would employ a tractor with
wheel disk to turn up the streets, and then they'd be rolled smooth,
with a thick layer of asphalt then applied. The final touch was a new
coating of pea gravel to reduce tar pick-up by car tires. The streets
held up beautifully and the technique most likely would be considered,
"Green," in today's world.

Micajah

Where is your hometown? I noticed you used the word "Macadam", that is
a rare word in the US. Named for a man named John McAdam. The first to
use stone and roll it to lock the stones together to make better roads.
Later he added oil/tar on top to help it last through heavy rains.
That is were the word "Tarmac" became popular and is still used at
airports. I come from a part of PA, USA where the outdated word
"Macadam" was still used to describe asphalt/blacktop. If I use the
word today not many people will know what it means.