Concrete Slab Curing

[SteelPE]

I have a 12” thick suspended slab that is used for an elevated parking area. The slab is constructed on top of steel beams and form deck. In order to prevent water from leaking through the slab the owner wants to apply a waterproof membrane ontop of the slab and then apply a structural toping(for protection of the membrane)after the membrane has cured. The membrane is a “one part, rapid moisture curing aliphatic polyurethane waterproofing membrane”. The manufacture says that this material can be applied to “green” concrete but I am not sure if it will effect the strength of the concrete in the end.

How long should you let the structural slab cure prior to applying the waterproof membrane?

 

[msquared48]

I would wait a minimum of 7 days after you reach your minimum f'c with the test breaks. Structure comes first.

Mike McCann
McCann Engineering

 

[hokie66]

Disagree with Mike. The membrane can only assist in curing the slab. Apply it as soon as the manufacturer recommends. This is not a recommendation for this type membrane.

 

[connect2]

Agree wt. hookie66,
Follow manufacturers recommendations, completely sealing your slab can't hurt, shore until the desired compressive strength is met.
Agree wt. Micke Mcann,
would be the sh..ts to find out that you hadn't reached the expected 7 day compressive strength. need a testing company to do this.
Re-reading this thread it says the 'owner wants to ...', that's problematic.
Who thick is the proposed topping, got all this figured in your design?

 

[hokie66]

An owner who wants a membrane on his slab sounds very informed to me. He has probably had a bad experience with a slab without a membrane.

 

[SteelPE]

I have a call into the manufacturers' technical department. Their salesman is going to be at the pre slab pour meeting but I am always leery about dealing with sales representatives because their products are always “the best”.

Connect2
Slab is already designed to be unshored during construction. The topping is going to be an additional 3” which I have figured into my design. I definitely agree with additional testing.

Thanks everybody.