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stanlam 11-27-2010 07:35 PM

Need advice on 1 1/2 inch of asphalt overlay on concrete and old Asphalt
 
I have a property with cracked concrete and asphalt. I had 2 different companies look at it and both are saying they can put 1 1/2 inches of asphalt over the whole parking lot and driveway. The driveway is concrete but the parking lot is asphalt. It's about 4500 square feet and they said it needs about 45 tons of asphalt and they are charging about $5,700.

Contractor 1 said they need to break apart some of the concrete to the base to replace it because it's cracked to much. Contractor 2 stated it is unnecessary and will just put the asphalt on top of the whole ground and will not remove any cracked concrete. Contractor 1 is using a 3 ton roller. Contractor 2 is using a 5 ton roller.

Any thoughts on who I should hire?

Bob Deb 11-29-2010 01:34 AM

I wouldn't install asphalt over cracked concrete, it probably won't last very long. Both types of pavements expand & contract at different rates & will allow the asphalt to lift up & separate. If the concrete is already cracking, the asphalt will crack too. There are reinforcement fabrics to place over cracks in existing asphalt before new asphalt is installed, but I am not familiar with a similar application for placing over concrete pavements.

The existing damaged pavement is a problem & there could be a lot of different reasons that the existing concrete & asphalt cracked. Wet conditions, drastic temperature changes, not thick enough of a layer, or a poor granular, stone, subbase material under it. By poor, I mean not enough material, not enough compaction, or the wrong stone type & size based on the soil conditions.

If you pave over the existing cracks, the new asphalt will likely crack in the same locations. By breaking up the concrete & asphalt pavements & compacting them, you will seat it into a better base to pave over. I don't know what roller weight is necessary, but I'd guess that it depends on the conditions of the subbase & the type of asphalt you are installing. It can have larger stones, like in "binder courses" & be more porous, or have more fines & smaller stones, like in "wearing courses" & be smoother & less porous.

Here is how to tell how many tons you need....

4500 Sq. Feet / 9 = 500 Sq. Yards
500 Sq. Yards / 12 = 41.67 Tons


It's a little complicated to explain what the 12 represents, but it's based on one ton of asphalt covering one square yard, making an 18 inch deep block of asphalt. The rule then requires that you divide the 18 inches by the depth you will be placing it, 1.5 inches in your case, or 18 / 1.5 = 12.

Don't overlook this, but do you have curbs, drains or sidewalks around the pavement? Adding another layer will raise the grade & could decrease the curb, drains & sidewalk heights creating drainage problems. Any changes in height, like in a low spot or a pot hole, will require slightly more asphalt.

Bondo 11-29-2010 08:50 AM

Ayuh,... I thought this post looked familiar,... From the 1 in the landscaping forum...
Quote:

Originally Posted by Bondo (Post 541837)
Ayuh,... No doubt removing the concrete, restoning, 'n compacting is the Best option,...

The difference might be a 10 year driveway if left in place, 'n a 15 or 20 year driveway if repaired properly...

Size of their rollers is pretty much irrevelant....


stanlam 11-29-2010 10:48 AM

Quote:

Originally Posted by Bob Deb (Post 542081)
I wouldn't install asphalt over cracked concrete, it probably won't last very long. Both types of pavements expand & contract at different rates & will allow the asphalt to lift up & separate. If the concrete is already cracking, the asphalt will crack too. There are reinforcement fabrics to place over cracks in existing asphalt before new asphalt is installed, but I am not familiar with a similar application for placing over concrete pavements.

The existing damaged pavement is a problem & there could be a lot of different reasons that the existing concrete & asphalt cracked. Wet conditions, drastic temperature changes, not thick enough of a layer, or a poor granular, stone, subbase material under it. By poor, I mean not enough material, not enough compaction, or the wrong stone type & size based on the soil conditions.

If you pave over the existing cracks, the new asphalt will likely crack in the same locations. By breaking up the concrete & asphalt pavements & compacting them, you will seat it into a better base to pave over. I don't know what roller weight is necessary, but I'd guess that it depends on the conditions of the subbase & the type of asphalt you are installing. It can have larger stones, like in "binder courses" & be more porous, or have more fines & smaller stones, like in "wearing courses" & be smoother & less porous.

Here is how to tell how many tons you need....

4500 Sq. Feet / 9 = 500 Sq. Yards
500 Sq. Yards / 12 = 41.67 Tons


It's a little complicated to explain what the 12 represents, but it's based on one ton of asphalt covering one square yard, making an 18 inch deep block of asphalt. The rule then requires that you divide the 18 inches by the depth you will be placing it, 1.5 inches in your case, or 18 / 1.5 = 12.

Don't overlook this, but do you have curbs, drains or sidewalks around the pavement? Adding another layer will raise the grade & could decrease the curb, drains & sidewalk heights creating drainage problems. Any changes in height, like in a low spot or a pot hole, will require slightly more asphalt.


THANKS a lot. Now you confused me even more. Just Kidding. I do want my driveway to last, so I'm just going to re-think everything again.

stanlam 11-29-2010 11:55 AM

Quote:

Originally Posted by Bob Deb (Post 542081)
I wouldn't install asphalt over cracked concrete, it probably won't last very long. Both types of pavements expand & contract at different rates & will allow the asphalt to lift up & separate. If the concrete is already cracking, the asphalt will crack too.

I looked online and found several article that stated it's okay to put Asphalt over concrete, but not the other way around. Is that correct?

Bondo 11-29-2010 12:10 PM

Quote:

Originally Posted by stanlam (Post 542230)
I looked online and found several article that stated it's okay to put Asphalt over concrete, but not the other way around. Is that correct?

Ayuh,... If you're in an area that Freezes in the winter, I wouldn't do it...

stanlam 11-29-2010 12:38 PM

Quote:

Originally Posted by Bondo (Post 542240)
Ayuh,... If you're in an area that Freezes in the winter, I wouldn't do it...

That clarifies a lot. I live in Sunny Los Angeles.

stanlam 12-03-2010 10:41 AM

Quote:

Originally Posted by Bob Deb (Post 542081)

Here is how to tell how many tons you need....

4500 Sq. Feet / 9 = 500 Sq. Yards
500 Sq. Yards / 12 = 41.67 Tons


It's a little complicated to explain what the 12 represents, but it's based on one ton of asphalt covering one square yard, making an 18 inch deep block of asphalt. The rule then requires that you divide the 18 inches by the depth you will be placing it, 1.5 inches in your case, or 18 / 1.5 = 12.

Hi Bob Deb,

thanks for the math equation. They are installing the asphalt today and we had a problem with how many tons were required. I couldn't verify that the contractor was telling the truth until I remembered you wrote the formula in this thread. Thanks a million.

Bob Deb 12-03-2010 09:21 PM

Quote:

Originally Posted by stanlam (Post 544749)
Hi Bob Deb,

thanks for the math equation. They are installing the asphalt today and we had a problem with how many tons were required. I couldn't verify that the contractor was telling the truth until I remembered you wrote the formula in this thread. Thanks a million.



Glad I could help, good luck with the project. :thumbsup:

Cmudr1 12-05-2010 08:46 PM

One problem with aspht is how flexible it is. If you put it over cracked concrete without a proper crack sealing membrane first the asphalt WILL eventually crack and then youre going to have more maintenance.
Asphalt over concrete is ok, it is possibly on of the better ways of doing it and is commonly done so on road jobs. The major key for asphalt is making sure the subgrade is adequate. Now with the concrete cracking it could mean the subbase is already insufficient, tho without pictures its hard to tell, because all concrete craks.

The formula for figuring tonnage needed is:
Length (in feet) Times Width (Feet) Times Depth (In Inches) DividedBy 9 Times 111.1 (weight of asphalt being used) DividedBy 2000 = Tons

The weight of the roller wont matter as much, it will just make it easier and/or faster for the contractor. But I would go with withever they recommend. For driveways we also use "Surface" material as its much finer and will provide a smoother finish.

I know its probably too late but hopefully i was helpful :P


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