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Concrete worktop

Posted: Wed Apr 22, 2015 7:44 am
by ftacarpentry
Morning!

I have made an island unit that requires a worktop at 1300x1300mm, and the client is after concrete.

I have a good working relationship with my clients, and they are hoping to achieve a rustic looking worktop (I.e. Not polished to a mirror finish, without any air pockets etc.), I have also explained that I haven't done this before and it will be a bit of an experiment and they are fine with this.

Anybody done this before? Any tips etc?

The top will be circa 50mm thick. I plan on using rebar/remesh and some glass fibres for reinforcement. I understand that I need to keep the mix as dry as possible to restrict shrinkage/cracking but I can't really ascertain the best mix to use, or even really which aggregate would be best?

All advice appreciated!

Ta,

Pete

Re: Concrete worktop

Posted: Wed Apr 22, 2015 8:16 am
by mark270981
This will be interesting work.

https://www.youtube.com/watch?v=U7GuE2O2DAo

will this video help?

Re: Concrete worktop

Posted: Wed Apr 22, 2015 8:24 am
by mark270981

Re: Concrete worktop

Posted: Wed Apr 22, 2015 10:37 am
by furynaturre
Go for it, it's not that hard to do, but the maintenance does have to be good, the only food safe not colouring sealer I found was Fila Hydrorep

http://www.tilecouture.co.uk/product-ca ... oC017w_wcB

I've attached some pics of a kitchen I made recntly, flakey was the name of the game!

Super plasticisers and loads of vibration when in the mould are your friends. Watch the Vids Mark-Numbers posted.

Image

Image

Image

Just have a go, it's good fun

James

Re: Concrete worktop

Posted: Wed Apr 22, 2015 4:58 pm
by houtslager
you have two options - in situ or in your shop/in the clients' garden
natural colour or coloured, if the latter then you need to use white cement dust, mix with sand / water / and colouring powder of choice.
Mix to a stiff mix, and "pour "

Note to remember - BLOODY HEAVY ! once set, and will take more ppl to lift into place then you think DAMHIKT !

For any through the top fittings, reduce the thickness by 50% from the underneath, this will allow you to use standard tap / waste fittings.

Don't forget to post pics - or it never happened ;)

IF more info needed - just shout out loud, I'll try to help more.

hth

Karl

Re: Concrete worktop

Posted: Wed Apr 22, 2015 5:02 pm
by tusses
I've seen it done on telly ! lol

looks easy :-)

Re: Concrete worktop

Posted: Wed Apr 22, 2015 6:47 pm
by ftacarpentry
Thanks for all the responses.

Mark- cheers for the links to those videos, they were interesting viewing.

James- that whole kitchen looks pretty amazing. The worktops are incredible, but is that also a workbench with a hob set in it?!!

Karl- cheers! I'll be sure to post pics as progress occurs... It's pretty much just a 1300mm square, but I'm sure I'll find a means of turning it into hardcore!

Tusses- yeah, saw it in TV too... Looked easy but now push has come to shove I'm a little more wary! Just got to resist the urge to stick all sorts of objects in it...

Thanks again gents!

Pete

Re: Concrete worktop

Posted: Wed Apr 22, 2015 7:14 pm
by ftacarpentry
Me again!

I still can't seem to settle on a suitable ratio for the mix...

Currently I'm thinking one part cement, one part sharp sand (to keep it a bit rustic and not too smooth), three parts builders sand.


Does that sound about right?

Cheers!

Re: Concrete worktop

Posted: Wed Apr 22, 2015 8:20 pm
by tusses
without aggregate, it's just mortar ? surely ?

I'm sure the one I saw used pea gravel

As mentioned before, plenty of vibration to smooth the top surface :-)

Re: Concrete worktop

Posted: Thu Apr 23, 2015 12:15 am
by furynaturre
You will need an aggregate, concrete is only strong because of the aggregate.

You need as much big stuff as you dare, without it jamming the mould and not allowing the fat to get to the outside. You are basically looking at 4 or 5 to 1 mix

For your top... 1.3x1.3x50mm

about 25kg cement

100kg gravel your choice, 10mm pea shingle is fine, you could use some silica fume as well but it's a faff to get hold of. Any aggregate a good deal larger than the sand will be ok, Seen some done with recycled glass!

50kg sharp sand

That's About 2 mixer loads

15 litres of water, with super platiciser this will vary depending how wet the sand and gravel are.

Add fibres

Dry enough it doesn't slop about, wet enough to move around. Neatly silicon the corners, knock the living daylight out of the mould (Best made of MFMDF or MFC) constantly, if you think you've knocked it enough, you haven't, keep knocking.

Trowel the back of the as it cheeses up.

Have a go, make the form nicely and if it goes wrong you can have a couple more goes.

Re: Concrete worktop

Posted: Thu Apr 23, 2015 7:12 am
by ftacarpentry
Cheers James- I had hoped the sharp sand would be aggregate enough, but had a feeling I was wrong! Sounds good, I'll have a stab in the next week or so.

This is going to be heavy!

Thanks,

Pete

Re: Concrete worktop

Posted: Sat Apr 25, 2015 4:21 pm
by colg
There's a good book by a guy called FU-TUNG CHENG called concrete countertops - now why do I thinks it's a yank book???

Re: Concrete worktop

Posted: Thu May 21, 2015 6:28 pm
by ftacarpentry
Well... after hours spend on my knees (ahem) she left the shop and is proudly sat atop the island...

All the pics look kinda the same, but since everyone was so helpful, thought the least I could do was post a couple of pics!

Former made from Melamine faced chipboard, on some 6x2"s that I had flattened and screwed into a rigid torsion-box type o' thing...

Image

I had made a grid of rio-rods (12mm diameter) tied on approximately 200mm centres. Dumped about an inch of muck in the former, tamped it like crazy, then floated the reinforcing on this, with some wire tied to the sides to stop it sinking when I gave it a good old shake! Dumped the rest on top to give me circa 50mm of 'depth'. The mix was as advised... three bags of pea shingle, three bags of sharp sand, a bag of dust, and as little water as possible.

I thought my vibrating device was inspired... an sds drill set to chisel mode with a very blunt chisel in it held against the former.

Image

After about 10 days, popped the sides off the former. Couldn't bring myself to flip it over... so left it another 5 days...

Image

Was really pleased to turn it without it folding in half, but initially concerned about the 'ghosting' of the rio rods... Left it another 5 days!!!

Spoke to an incredibly helpful chap at ATS diamond tools, who talked me through the polishing process, selling me the bare essentials to get it done without going bananas and buying all the gear.

I managed to use my electric polisher (grinder is too fast) with their copper-bonded discs (4") with just a brush to sluice water over the surface.

Boom!
Image

As always... handles to follow!!!

Thanks again to all of you for your help.

Re: Concrete worktop

Posted: Thu May 21, 2015 10:14 pm
by chippy1970
Nice job turned out well. Looks really crisp, is it ?

Re: Concrete worktop

Posted: Fri May 22, 2015 5:49 am
by ftacarpentry
Thanks!

It is crisp, but not without air dimples and the odd pin-hole. Fortunately my clients wanted a more rustic look, so SUPER crisp wasn't a requirement, and I only needed to polish it to circa 200/400 grit for a honed finish.

If I was going for a flawless finish, I would use densifiers in the mix, and make sure I could get under the whole former to vibrate it...as I did it on the floor I was limited to only knocking the edges.

Pete

Re: Concrete worktop

Posted: Fri May 22, 2015 6:16 am
by PABLO123
Well done that man, super job :D

Re: Concrete worktop

Posted: Fri May 22, 2015 10:52 am
by chippy1970
I like it when they put glass, marbles and bits of tile in the mix. Looks amazing when they're polished up but I bet they're a real pain to do.

Re: Concrete worktop

Posted: Fri May 22, 2015 8:09 pm
by mcluma
real nice job

I like it

Re: Concrete worktop

Posted: Sat May 23, 2015 8:19 am
by mark270981
I like that a lot - very nice work.

Re: Concrete worktop

Posted: Sat May 23, 2015 11:49 pm
by houtslager
8-) good un

Re: Concrete worktop

Posted: Thu May 28, 2015 4:25 pm
by Neil_C
Beautiful job, I really like it.

Re: Concrete worktop

Posted: Thu May 28, 2015 8:04 pm
by siafins
Nice job of that! Really like it.

Re: Concrete worktop

Posted: Fri May 29, 2015 4:20 pm
by ftacarpentry
Thanks for all the thanks!

I am gagging to have another go now...

Re: Concrete worktop

Posted: Fri May 29, 2015 5:44 pm
by promhandicam
Hi Pete. Odd question, but are you from the Bexleyheath area by any chance?

Re: Concrete worktop

Posted: Fri May 29, 2015 10:09 pm
by ftacarpentry
No... Afraid not! I'm based just outside of maidstone.

Re: Concrete worktop

Posted: Mon Jun 15, 2015 7:43 pm
by billybuntus
Nice effort. Not my cup of tea but I can see the appeal.

I thought you'd snook in and cleaned my kitchen floor for a second when I first saw it. I have exactly the same floor. Could you ask your client what they've sealed them with?

Mine never look that good.

Re: Concrete worktop

Posted: Fri Mar 18, 2016 3:21 am
by emir01
@ftacarpentry

Awesome work. I just wonder if you polished the edges on the top? I think that the edges would be very sharp if they are not grind a little bit.

Re: Concrete worktop

Posted: Sun Mar 20, 2016 11:56 am
by Meccarroll
Very nice, thank's for posting.

Mark

Re: Concrete worktop

Posted: Mon Mar 21, 2016 2:28 pm
by asselin22
very good job, i love it

Re: Concrete worktop

Posted: Mon Mar 21, 2016 4:44 pm
by MikeRotherham
That looks really good.

Re: Concrete worktop

Posted: Mon May 08, 2017 1:06 am
by duds888
Hi,

Feel like I've been looking for just this thread (in the UK) for a long time!

I'm currently renovating my kitchen and am going to be doing a cast-in-place concrete worktop. The examples here look amazing and so looking for some advice.

I'm going to use products from these guys (edge forms, suspended mesh, concrete additive, sealers etc.):
https://www.concretecountertopsolutions.com

Following the procees pretty much as per this video:
https://www.youtube.com/watch?v=GRYJRGbXb1Q

The issue I have is the concrete. What to use and in what quantity. It would be great to have the company explicitly advise on products, but they're based in the USA so can't. I will be using the 'Liqui-crete' admix to make the concrete flowable (see video), whilst the suspended glass mesh system should keep ot from cracking.

I noticed mentioned of quite a bit of aggregate. What advice the company has given me is to pretty much exclude...

"If you do want to make your own mix, you can combine 15 lbs of portland type I cement, 45 lbs of clean dry masonry sand, and one of our Liqui-Crete boxes. You do not need any larger stone as this does not give concrete strength. Some of the strongest mixes in the world only contain fine sand. The stone is a cheap and efficient way to help reduce shrinkage and increse compression strength slightly. If you do add stone or pea gravel there is nothing wrong with this but I would stay around 3 mm and I would have about 30 lbs of sand and 15 lbs of stone"

Asside from Agregate, my last main question is sand. Builder's sand or Sharp Sand?

Re: Concrete worktop

Posted: Mon Aug 21, 2017 6:59 pm
by Jakescwelch
Hi

I've just finished casting my concrete work tops and was after some advice on sealants. Would prefer food safe obviously but struggling to find a decent product this side of the pond. Polyaspratic seems to be the one of choice in the US but unconvinced of how safe it would be...

Any help?

Cheers

Re: Concrete worktop

Posted: Mon Feb 19, 2018 2:46 pm
by davetregoning
@furynaturre @ftacarpentry

Hi there, I'm looking at doing concrete worktops for our kitchen. There will be 3 small worktop areas which I'm planning to cast face-down in melamine-faced chipboard casts, then one large worktop (with sink notch-out) which I'm gonna have to cast-in-place due to the size.

Do you have any recommendations, specifically with regards to the concrete mix/ratios and the best sealants to use?

Any help or suggestions would be much appreciated. Cheers.

Re: Concrete worktop

Posted: Sat Mar 03, 2018 3:06 pm
by ftacarpentry
Hi Dave,

I followed furynature's excellent advice:

You will need an aggregate, concrete is only strong because of the aggregate.

You need as much big stuff as you dare, without it jamming the mould and not allowing the fat to get to the outside. You are basically looking at 4 or 5 to 1 mix

For your top... 1.3x1.3x50mm

about 25kg cement

100kg gravel your choice, 10mm pea shingle is fine, you could use some silica fume as well but it's a faff to get hold of. Any aggregate a good deal larger than the sand will be ok, Seen some done with recycled glass!

50kg sharp sand

That's About 2 mixer loads

15 litres of water, with super platiciser this will vary depending how wet the sand and gravel are.

Add fibres

Dry enough it doesn't slop about, wet enough to move around. Neatly silicon the corners, knock the living daylight out of the mould (Best made of MFMDF or MFC) constantly, if you think you've knocked it enough, you haven't, keep knocking.

Re: Concrete worktop

Posted: Thu Mar 15, 2018 1:40 pm
by furynaturre
What He said :lol: