Finishing Concrete. Confused on which Floats?

[lovelyjob]

Hi all. I have searched but couldn't quite find definitive answer.
I have small slab hearth to pour and want the surface smooth. I have read concrete finish 3 stage process...screed across to compact and flatten, then float to even out lows and highs but leave open pores and allow water to evaporate off surface? And then finish with a steel float to get a smoother finish. Is that about right?

Its a constructional hearth and the pour will be about 170mm thick.
I'm thinking 5:1 or 6:1 Ballast/cement...that about right?

I'm confused re Plasterers floats and concreting floats. Don't want to spend lot of money as I only do this every blue moon.
Any advice what to look for re timing when to finish the final float please?

Stage 1. Wooden screed across surface. Piece of long timber.
Stage 2. Wooden or Poly Float?
Stage 3. Steel float to achieve finer smooth finish.

Thanks in advance guys.

 

[SammyInnit]

Why not put down the bulk as concrete then top out with self leveling pour screed? It'll be much easier for someone who hasn't finished concrete to a smooth glass like finish before.

As for timing you need to work it to within flat while it's still fresh, you need to finish it smooth just as it's going off and firm to the touch.

When large area slabs are done with a glass finish they'll get the power floats on while they're able to walk on it without leaving boot prints but it's still green enough to be finished.

 

[^woody^]

Concrete floats are stiff, and plasterer's floats flex - but TBH if you've never used one and have a single job you wont know the difference - get any old cheap one. You wont get concrete dead smooth no matter how hard you try. If this will be seen, then you need a sand cement screed on the surface

Level the concrete by sliding a straight edge sideways while pulling it toward you. Then trowel it. Don't mix it too wet else the water will pond on the top and it will be a right mess when it all dries off.

 

[lovelyjob]

Sammy, Woody, thanks for your replies and advice, most helpful. I've since done some research and your advice reflects that also. A lot more to concrete and it's uses than I ever thought!

 

[lovelyjob]

Just a note on self leveling pour screed...specifically BOSTIK CEMENTONE CEMPOLATEX ( Note: I have only researched this product)...According to BOSTIK this product does not have any fire data specified. In this case it would fall under EUROCLASS FIRE RATING F which states..."If the product is not documented, or the manufacturer has not provided the fire properties for the product, it does not meet the criteria for any class.

This does not mean it does not comply with the 'Non Combustible' aspect of Building Regs for Fire place Constructional hearths, but it does mean it is not proven to be so. In the case of pour screeds, my naive brain picked up on the additive 'Latex'.
Hope this helps someone.

 

[^woody^]

It doesn't burn if that is what you are asking