THINSET STRUCTURAL CONCRETE TOPPING

[rlewistx]

I'm evaluating a structural slab. It was poured about 3 weeks ago on a hot summer day. The slab is about 85'x85'. The set time got away from the contractor and the top surface looks terrible and has high spots (photo attached). It is not flat. The slab is needed to erect some equipment on so it needs to be flat. Not super flat, but flatter than it is now. I cannot pour a concrete topping on it, like 4 inches, due to other constraints. Basically the surface needs to be ground and the low spots filled in. I'm looking for a thinset topping recommendation that can be feathered out if need be. Does anyone have previous experience with a good durable thinset topping they would like to recommend? Again, it is industrial application so I can't have it delaminating easily.

Thanks for any assistance.

 

[Ingenuity]

We used CTS RapidSet Cement-All for a similar finishing problem. It is CSA based-cement (not Portland) so rapid setting and requires immediate and continuous curing during initial set. Good for max 4", down to feather edge. Recommend you add their Flow Control and Set Control to extend you flow characteristics and set time.

The manufacturer is in California and distributors through the US.

Link

 

[Ron]

I use SikaTop....a polymer modified cementitious topping manufactured by SIKA.

 

[TehMightyEngineer]

What about hydro-demolishing the top third of the slab and then re-pouring?

Maine Professional and Structural Engineer
American Concrete Industries

http://www.americanconcrete.com

 

[RPMG]

The existing topping can also be scarified.

If only portions of the slab need to be flat, you can add concrete curbs or pads.

 

[Guastavino]

BASF Makes some good products too. Make sure there are other latent issues with the slab before you just add a topping. Also make sure to match control joint locations.

As an aside, I wouldn't take a project like this on unless they were paying me a lot. Reason being is the liability you take on is high. Once you get involved any future cracks can become "your fault" whether it was your fault or not. In other words, just be careful you cover yourself well. It's the contractor's problem now, but it will be your problem after your recommendations if anything else goes wrong with it.