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Re: To Bond or Not to Bond - Concrete Thin Overlay

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Richard,
 
        Why not consider standard asphalt paving like they use for bridge decks?  I think you'll find this cheaper, faster, better, and easier to remove if they change the building back to its original use.
 
        You may not need any reinforcing or any jointing except where you cross an actual building expansion joint; but check this out with others more experienced with paving than me.
 
Regards,
 
H. Daryl Richardson
----- Original Message -----
From: Rich Lewis
Sent: Tuesday, August 22, 2006 8:59 AM
Subject: To Bond or Not to Bond - Concrete Thin Overlay

I have an architect client who asked me about bonding an overlay to an existing concrete slab.  They are turning in inside slab of a building into a drive-thru section for a bank.  They are considering adding topping to the slab to drain the slab from any storm water.  It would have a crown in the middle of say 4 inches and taper down to 2 inches at the building edge.  The width of the building is 60 feet.

 

He asked me if it should be bonded to the existing concrete slab and about jointing.

 

My initial thinking is to allow the new concrete topping to bond to the old concrete.  Then the jointing should match whatever is in the slab underneath.  I look at this as like a slab poured on metal deck.  Jointing is not required because the decking locks the slab in place and distributes the cracks out as micro cracks.  By bonding this to the existing slab it will do the same thing.  A movement joint needs to be provided in the new slab where the existing slab has one.  Also, there will be WWF in the topping to help with the stress distribution.

 

Any other thoughts or experiences on this?

 

Thanks.

 

Rich