Asphalt Driveway Over Gravel: Why The Gravel ?

Page 1 of 2  

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8/30/2010 11:46 AM, Bob wrote:

A: asphalt pavement is not liquid B: the gravel is for drainagek and stability.
--
Steve Barker
remove the "not" from my address to email
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Steve's right...you're confusing paving asphalt (contains a lot of gravel aggregate) and roofing asphalt (contains minor amounts of finer fillers). Next time you drive by a highway surfacing project note the big dump body trucks lined up there filled with hot mix. No liquids there.
Joe
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8/30/2010 1:31 PM, Joe wrote:

The liquid, sticky, or plastic part (asphalt cement) is only 5% of the total mix. The rest is aggregate.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Then there's "hardtop", which is common in my area on lightly-loaded roads: You lay down the usual packed-aggregate roadbed, then spray really runny tar on the surface. Then you spread pea-gravel on top of that, and just let passing traffic roll it in the rest of the way. Excess gravel gets pushed off to the shoulder over time. It's fairly durable if you keep heavy trucks off of it.
--
Tegger

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is the classic Macadam-type of paving.
Micajah
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I didn't know that. We just call it "hardtop". That's to differentiate it from the softer gravel/sand mix which goes on roads that are lesser to hardtopped roads. The big advantage of hardtop is that it's really cheap to install compared to asphalt, but is a lot more durable (and cleaner and washboard-resistant) than gravel/sand.
--
Tegger

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

"Hardtop" is a kind of car...but I have heard of "blacktop".
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I thought "blacktop" was asphalt. "Hardtop" is gray, on account of the gravel rolled into the tar.
--
Tegger

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 9/1/2010 9:33 PM, Tegger wrote:

I haven't seen that yet, except for tar and chip or whatever they call that. Actually I knew of one road that when paved it must have had way too much tar and not enough stone. On some of the hotter summer days they would coat it with stone but I don't recall if they rolled it or let the cars do the work. As far as I know they were still adding stone after 6 or 7 years and it was still turning somewhat liquid on the hottest days.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
replying to Tegger, Jake wrote: We call that Tar and Chip or Shot and Chip around here (NW Pennsylvania) very popular on the back roads that get traveled enough to get away from dirt and its cheap to repair/replace when the snow plows tear into it
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

This is a terrible way to surface roads. It really plays havoc on your skates after a icestorm. DAMHIKT!
--
Best regards
Han
email address is invalid
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8/30/2010 7:31 PM, Tegger wrote:

This is known as "chip and seal" (although in actuality it's seal and chip) in my area.
--
Steve Barker
remove the "not" from my address to email
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob wrote the following:

To prevent or minimize frost heave for one.
--

Bill
In Hamptonburgh, NY
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 8/30/2010 1:56 PM, Micajah wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The hometown is a small farming community in central MO, but dates back well before the War of Northern Aggression. The streets there are nowadays a typical mixed bag of asphalt, concrete and Macadam, but as far as I know, the Macadam ones are still maintained by the occasional wheel disking, rolling, new tar and a coat of pea gravel. FWIW, most of the older curbs are cut granite.
Micajah
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sounds like the "War" isn't over yet?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's funny -- I thought it was the war to hold the Union together, and secondarily to free the slaves.
[...]
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
-snip-

I'm in upstate NY & grew up in Schenectady, Schoharie & Greene counties in the 50s-60s. I used the term last year and was amazed that none of the folks I talked to knew what it was. My wife grew up in Saratoga county- and the folks I was talking to were all from the NY city area. [and a bit younger]
I didn't think to look it up back then, but when Micajah used it I Wiki'ed it. I knew it was named for Mr. McAdam- but didn't know the specifics of *his* roads.
I've always used the term[improperly, it appears] to refer to any asphalt surface.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.