Concrete over asphalt

[Kevin54]

I'm seriously considering adding on to my garage. I've kicked it around about adding on the the back of the garage or the front of the garage, and I think I will be ahead adding on to the front.

Now my question is....when I had the asphalt drive put down, I have maybe 1 1/2'-2' of crushed stone underneath. The stone driveway was rolled with a huge Bomag roller that they were using on our road at the time. It had the front vibratory roller on it. The front drum was actually 5-6' in diameter. So maybe three years after going through winters etc, I had asphalt put down.

What would be the reason to remove the asphalt to pour concrete. I know it's not conventional to do it that way, but everything is already pack and compressed. When I add on, I am going to do it as a pole style building.

So is there any real reason to consider pulling up the asphalt?

 

[mtwaterguy]

I think the problem would come when the asphalt started to crumble. You'd lose your base and create problems for the concrete.

 

[bazzateer]

Asphalt is soft, you don't want to pour concrete on a soft base.

 

[Kevin54]

I think the problem would come when the asphalt started to crumble. You'd lose your base and create problems for the concrete.

Asphalt is soft, you don't want to pour concrete on a soft base.

If the asphalt crumbles though, it would just crack wouldn't it. It's not like it's over any voids as the gravel underneath is compacted, along with the asphalt compacted. And all asphalt is, is stone with a bonding agent. Don't get me wrong, not looking to start an argument, just trying to grasp as to why. I do understand not putting asphalt over concrete, but not the other way around. ..If the asphalt is contained and sealed, I don't see where there would even be any movement to allow it to crack really. I know there is movement now to some extent because it is exposed to the weather. That leads to deterioration. A large truck in hot weather will let the asphalt roll to a certain extent.. I grasp that.

 

[paullie]

it depends on the asphalt. roads are built like that all the time. if the asphault is solid and in good shape i wouldn't worrry about puttin concrete over it

 

[EvilEye]

I noticed that here in Central Pa New road construction for some heavy use highways have been doing just that. They put in the 2 or 3 layers of crushed stone heavy to lighter then pave over top of that. then put joint control and rebar and concrete over that. Just what I noticed my .02$

 

[raddksn]

I have seen major highways paved just like that concrete over asphalt i think the broblem would be differance in hight

 

[raddksn]

paullie + evileye type faster than my one finger hunt + peck

 

[JakeKohl]

Asphalt is soft, you don't want to pour concrete on a soft base.

Dirt is soft too...but it would make me nervous leaving the asphalt under the concrete.

 

[KinzeMech]

Your concrete is only as good as it's foundation.

If properly built, graded, and drained, a gravel base over compacted dirt will take much longer to deteriorate than asphalt. That, and being that it is a common practice, it's behavior is known, and predictable. Pouring over asphalt may work just fine, or it may invite unanticipated problems down the road.

 

[dcs Inc]

I don't have the particulars in front of me but they have been doing this in testing for awhile. White topping or white capping.... can't remember and I'm too lazy to pull it up. It's being done on large parking lots. May be a different animal going from commercial to residential applications. Personally I'd rip it out. It's normally thin and "hopefully will have a good stone base under it you can build up from.

 

[c7fx]

Not an expert but seriously seems the same as pouring over stone which they always do. I wouldn't see a problem with it.

 

[Justanoldguy]

Just do it.
The only reason the asphalt deteriorates is traffic directly over it and exposure to weather conditions.
You won't have either of those and a min of 4" concrete will not break down over the asphalt.
The trouble with asking a question like this on here is people will go out of their way looking for problems that won't exist. eg invent them .. lol
As mentioned, height of asphalt is you only concern.

 

[ConCretin]

dcs inc. got it right. It's called white topping and it's done all the time. If the existing base supported an asphalt surface, it will support concrete just fine.

 

[mrobins297aaa]

I was thinking of doing the same thing. My asphalt drive is starting to show its age and since I wouldn't have a height problem I was thinking of putting concrete right over it.
Just form it up with 2x4's and pour.
I asked my concrete buddy and he said it wouldn't be a problem.

 

[Will67]

Get someone with a nuclear gage to give you a compaction reading, cut a few cores and have some destructive testing done and compare against Caltrans standards....if ok pour over it.....if not rip out asphalt

 

[dcs Inc]

Just check the elevations on center line. Asphalt guys normally raise the center line of the drive just to get an extra runoff. Form to the highest cross level to make sure you have at least 4" at the thinnest area, which raises other problems. Concrete will expand and contract at different levels depending on thickness. If the center is 4" and the edges are 5 or 6" thick, the weakest point is at the thinest area. When stresses occur, it will crack at the path of least resistance.

 

[Justanoldguy]

Then you just put a saw cut through the centre to ensure when it cracks that you control where it cracks.

 

[dcs Inc]

OK....thats one way. One should take the time and attempt to pour concrete at a consistant thickness. If the centerline is thinner, one would raise the elevation of the forms on the edges and install a compacted fill to even out the thickness. THEN, install a control joint down the center. Short cutting concrete instaltion is just throwing money out the window.

 

[Justanoldguy]

I don't see it as short cutting anything.
I have poured plenty of concrete floors both residential and commercial/industrial where sections of the floor are differing thickness for varying reasons.
Never had any problems in the last 45 years by doing that.
What could go wrong as long as the ground is compacted properly.

 

[Charles (in GA)]

The state is doing that here. They put down about 6" of rock and smooth it out and roll it, then about 8 inches of asphalt and on top of that they put about 10 inches of concrete, and you have an interstate highway.

One section, they tore up some concrete that was in bad shape and re did it, but another section that the concrete was OK, they put asphalt on top of the old concrete (12" on top of a 18" or so rock base) and then on top of the new asphalt, they put 10" of new concrete. They actually had to raise the bridges crossing over this section.

Charles

 

[Kevin54]

I don't have a problem with the thickness. I can be a little higher than my existing garage and slope down into it. To me that's no big deal, and by the time I ever move, I'm not really gonna be at the age that I give a **** by then anyways I'll be feeble minded and in Depends by then.

My problem is right now that I either have too much stuff or not enough room. We have a 12' x 16' shed that right now houses the JD garden tractor, table saw, ladders, and garden tools. In the winter, the JD comes out, snowblower goes on it, and it goes in the house garage. My Compact tractor has a loader and a post hole digger. The PHD will go into the shed, but the loader will stay on the CUT and go into one side of my garage, where I now have three toolboxes and a 4' x 8' table with my small lathe on it, along with an arbor press, surface plate, and a small toolbox with lathe accessories. Then I bought my mill and a larger lathe. And I'd like to get a surface grinder in the future.

Given all of that, my truck is setting outside. And I'm not one to leave a vehicle set out. So I figure, I can keep all the machinery at the back and add on to the front so I have a place to park. I have a friend down the road that does construction and I can hire him to roof it for me. The rest, the wife and I can do.

I would like to have it tall enough though that maybe sometime in the future I could put a hoist in so I could work underneath of a vehicle.

As it is right now, I have 6' of apron on front of my garage that is covered. If I build on 28' deep x 26' wide It would take up the area across where I have two doors presently. Those are 9' doors. So if I have reverse gables on the new section, I could get a lift that is mobile, add a 16' door on the front and center it to the ridge if I needed to do something underneath a vehicle.

I'm going to have to start getting some prices together. I have a guy that does my concrete work and he'll beat anyone around here where I live, so that's no problem there. I can live with the slope from one to the other.

OR....I'm going to have to set momma down and talk about some serious downsizing Nah....I think I'll avoid that conversation with her.