Hand polishing concrete

[Chumley.mouse]

Has anybody hand polished concrete before ?

I’m currently trying to make a concrete windowboard , any tips or recommendations on which discs pads are good ? Also a good sealer to use ?

This is where i am at ….. its still curing in the form work. It was all going well untill I vibrated it and all the water poured out along with the fat and so its left quite a rough finish and wasn’t able to trowel it up smoother. The underside might be better when i strip it. The plan was to always polish it but was hoping a more troweled up finish might make it easier?



Thanks.

[bimsb6]

Thats going to be a bd to move around without breaking it .

[craigthecoupe]

I cant help i'm afraid, but following with interest, I've always fancied a go at making a concrete/terrazzo worktop.
there are loads of pads on amazon, no idea if they're any good?

[Rob.]

I reckon you'll struggle polishing that top face now (would need to have been troweled smooth while setting). You'll want to flip it and polish the formed side instead.

[Chumley.mouse]

bimsb6 said:

Thats going to be a bd to move around without breaking it .

This is a concern, its 40mm thick and i have put a bit of reinforcement in it. I think some sort of wire mesh might have been a better idea but hopefully it wont crumble away when i strip it.

Think ill leave it a couple of weeks to cure before remove it though.



I put it in the middle of the concrete not in the bottom like pictured.

[Chumley.mouse]

craigthecoupe said:

I cant help i'm afraid, but following with interest, I've always fancied a go at making a concrete/terrazzo worktop.
there are loads of pads on amazon, no idea if they're any good?

Ive seen the kits on amazon and i think thats what ill get to start with , like you say not sure if they are any good. ?

[Dutch80]

I have seen some Concrete polishing tools on a website called Speedcrete which have metallic diamond and the resin bonded diamond pads. Some of these can be added to an angle grinder for small projects like this.

[Chumley.mouse]

Rob. said:

I reckon you'll struggle polishing that top face now (would need to have been troweled smooth while setting). You'll want to flip it and polish the formed side instead.

Yeah, i would have liked it smoother but i mixed it too wet.
I’m not expecting the first one to be any good really i think its going to be a learning curve, i have 5 in total to do so i might have a couple of bad ones.

I was under the impression that you could polish concrete rough or smooth ? Just the rougher you start with the more work it will take to get a better finish, Bit like car body filler ?

I have read that you need to leave it 28 days to fully harden so its going to be a while.
Practicing on an old slab i think is the next step …….it looks easy on youtube but im sure its not.

[Chumley.mouse]

Dutch80 said:

I have seen some Concrete polishing tools on a website called Speedcrete which have metallic diamond and the resin bonded diamond pads. Some of these can be added to an angle grinder for small projects like this.

Thanks ,I’ll take a look.

[reggie747]

bimsb6 said:

Thats going to be a bd to move around without breaking it .

Let's hope he's put some light rebar in it !!

Edit: just seen that he has...

[reggie747]

What size aggregate did you use ?

[Chumley.mouse]

I read that sharp sand makes harder concrete? Not sure if thats true but thats what i used. Plus the gaffer said she didn’t want to see big “ bits” in it after it had been polished so that was another reason for sharp.

Mixed it 5 -1 with a bit ( cap full ) of mortar dye ( black ) to try and make it darker grey than usual light grey concrete. Its all a bit of trial and error.

Just been and had a bit of a poke at it and it seems a lot harder than the weekend , its been done 5 days now but its cold in the garage so not sure thats helping. It is nice and flat though so thats a plus .

[Mr Magooagain]

You’ve made it too weak imo. Break it up and start again and I think you will get a better result with at least a three to one ratio. After vibration and as it starts to dry but still wet, sprinkle pure cement dust all over it using plenty. Float/ rub it up with a plastic or wooden float and if needed more cement dust then another pass with the float. When it’s starting to dry then trowel it with a steel trowel to get a smooth finish. Don’t over trowel it each time but trowel until it’s smooth, nearly dry and flat.

Edit to add that it needs a month to cure to give it a chance.

Edited by Mr Magooagain on Tuesday 25th February 19:38

[Drumroll]

Definitely to weak, made even worse as you have made it way to wet.

[OutInTheShed]

Mr Magooagain said:

You’ve made it too weak imo. Break it up and start again and I think you will get a better result with at least a three to one ratio. After vibration and as it starts to dry but still wet, sprinkle pure cement dust all over it using plenty. Float/ rub it up with a plastic or wooden float and if needed more cement dust then another pass with the float. When it’s starting to dry then trowel it with a steel trowel to get a smooth finish. Don’t over trowel it each time but trowel until it’s smooth, nearly dry and flat.

Edit to add that it needs a month to cure to give it a chance.

Edited by Mr Magooagain on Tuesday 25th February 19:38

This is how to make a really smooth surface that will be mostly cement.
I associate 'polished concrete' with a smooth surface created by cutting down the concrete, polishing away parts of the gravel/stones, so the surface is mostly polished stones.

If you just want smooth cement, it would be easier to skim it when it's set?

[Mr Magooagain]

OutInTheShed said:

Mr Magooagain said:

You’ve made it too weak imo. Break it up and start again and I think you will get a better result with at least a three to one ratio. After vibration and as it starts to dry but still wet, sprinkle pure cement dust all over it using plenty. Float/ rub it up with a plastic or wooden float and if needed more cement dust then another pass with the float. When it’s starting to dry then trowel it with a steel trowel to get a smooth finish. Don’t over trowel it each time but trowel until it’s smooth, nearly dry and flat.

Edit to add that it needs a month to cure to give it a chance.

Edited by Mr Magooagain on Tuesday 25th February 19:38

This is how to make a really smooth surface that will be mostly cement.
I associate 'polished concrete' with a smooth surface created by cutting down the concrete, polishing away parts of the gravel/stones, so the surface is mostly polished stones.

If you just want smooth cement, it would be easier to skim it when it's set?

Yes you do have a point but as you probably know most polished concrete is a floor where it’s at least 10 cm thick. In this instance I don’t think the op has a choice unless he uses granite chipping’s.

Edit to add: The op wife says she doesn’t want to see odd big bits in it!
What about micro cement?

Edited by Mr Magooagain on Tuesday 25th February 20:50

[Chumley.mouse]

Thanks for the input… its all a learning curve. It will be interesting to see what happens when i strip it.

The problem i had was it was fine until i vibrated it. It did its job and hundreds of little air bubbles came out but unfortunately all the water came out too which I presume bought some of the cement out.

I didn't want to mix it too dry then end up with voids on the front edge that will be seen.

Im not after a mirror/ gloss finish, more a flat / smooth one.

I will get some discs and practice a bit while I’m waiting for it to cure and also get some sealer of some kind.

[LimmerickLad]

Add some granite dust next time & lightly bang edges and underneath with a hammer rather than vibrate.

[wolfracesonic]

Have you struck the mould yet? If not and you find lumps of concrete come away with it, try something like this, assuming you haven’t already.

[Chumley.mouse]

I didn’t have anything as fancy as that to hand but I did give it a couple of coats of some left over Castrol edge 10/40. If it falls apart when I strip it I won’t be too disappointed, I’ve got a feeling that more cement was needed anyway .