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Existing surface preparation to receive new topping

Existing surface preparation to receive new topping

Existing surface preparation to receive new topping

(OP)
The contractor has removed a 1½" thick bonded concrete topping from the top of a 50 year old concrete waffle slab floor (2½" thick slab on ribs at 24" centres each way). Some of it was well bonded but much of it was not. The top of the old waffle slab is rough. The contractor wants to place the new topping on top of the old waffle slab with a proprietary water based epoxy bonding agent with a 24 hour open life, but no surface preparation. Is that ok? Shouldn't it be shotblast? What surface preparation should be used?

RE: Existing surface preparation to receive new topping

I think you need a clean, moist surface. This likely means a shot blast or water blast surface. I would have little faith in a manufacturer's assertion of "24 hour open life" for a bonding compound. These chemicals can just as easily serve to debond.

RE: Existing surface preparation to receive new topping

(OP)
OK, THANKS. WE HAVE USED THE BODING AGENT IN A NUMBER OF PROJECTS WITH GOOD SUCCESS, ALTHOUGH WE NEVER ACTUALLY LEFT IT FOR 24 HOURS. I AGREE WITH YOUR COMMENT ABOUT SHOTBLASTING.

RE: Existing surface preparation to receive new topping

Has the manufacturer of the topping been contacted? It seems that they would have a vested interest in getting the best adhesion of their product. I'd get them to pay a visit or at least give a recommendation over the phone.
Document their recommendation and give it to the contractor. It might come in handy if there is a warranty claim.

RE: Existing surface preparation to receive new topping

If the project is large in scope, maybe put the onus on the contractor to prove via field trials that it works. 2'x2' trial topping areas using 2 or 3 different bonding agents/open times, followed by bond test to ASTM, or equal.

RE: Existing surface preparation to receive new topping

(OP)
To JedClampett - the topping is concrete so there is no manufacturer. I should have been clearer in my post.

To Ingenuity: a very good idea. Thanks.

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