Trowel finish on Self-compacting concrete

[KimWT]

When I tried to do steel trowel finish on precast walls, self-compact concrete was stuck to the trowel like glue.
And the finish is not looking good.

Someone says sprinkling water will help, but this may cause durability issue like scaling.
Is it acceptable practice to sprinkle water before troweling on self-compacting concrete slab?

Please tell me how to finish self-compacting concrete with steel trowel.

Thanks for your time!

 

[Ron]

Use a magnesium float first, then steel trowel. You are probably trying to trowel it too quickly.

 

[KimWT]

Thank you very much for your info!
Can you tell me when I should try a magnesium float first and then how long I should wait to use a steel trowel?
Do you think these timings are VERY different among concrete mix designs?
I wonder how you can decide WHEN to start troweling.

Thanks again!

 

[mike20793]

I recommend contacting the self consolidating concrete organization or visiting their website and reading the related ACI documents. They probably detail the proper finishing techniques.

 

[TehMightyEngineer]

I tried my hand at a little finishing of a SCC slab last year. While it was definitely stickier than the regular mud I found it easy enough to finish to a smooth, level surface. We poured, struck it level with floats, and then steel troweled it. It helped to trowel it towards an edge of the form and strike it off at that edge. That way it avoided making a hump where you lifted the trowel where the concrete was slightly sticking to the trowel. Not sure how much it matters that we're batching in a precast plant with type III cement and well controlled water (no bleeding).

Keep in mind, I'm an engineer and not a concrete finisher. I definitely am no expert at running a trowel compared to the guys in the shop.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[Teguci]

I would be upset if I saw water being used to finish a precast element.