Concrete color fade

[Manziclan]

IMG_20161114_200521

• Manziclan
• 14 Nov 2016

IMG_20161114_200531

• Manziclan
• 14 Nov 2016

Hi - hoping for some advice on concrete colour fading.

I have self poured a concrete slab as a hearth for a log burner and we were after a layer of concrete looking (Not too polished) but black or at least dark grey concrete. We're more than happy with the odd air bubble gap as this is the look we were after (think lava).

It had been down for a few days and has set well, but the top seems to have oxidised and has developed a paler colour which is almost dust like. It's not dusty but it is noticeably lighter. I have removed the side support boards tonight that I screwed to the floor to make the form and the newly exposed sides are the exact finish that we are after.

My question is around my options. Ideally we'd like the top to resemble the sides. Will they (the sides) fade/oxidise like the top now they have been exposed. Can I somehow polish or sand off the top grey finish and will this expose the black underneath or will this the simply fade again. I didn't cover the top whilst it dried which may have been the issue but can it be reworked to its former glory or do I need to seal and paint it? Having said that when sealing it will it come back?

I have attached a couple of pics that hopefully shows the top and side face so the difference can be seen. The white stuff is some mastic I applied to stop leaking underneath and try to get a uniform edge.

 

[Newboy]

I'd suspect that the exposed surface has dried a little too quickly but bear in mind that a standard concrete mix will dry to a pale grey colour - think of all the 60's tower blocks and car parks. If you used a reelease agent on the formwork then that may account for the darker sides.

 

[Manziclan]

Thanks for the response. I did add black powder colourant to the mix but do agree that I think the top dried too quick. The formwork was just in place but I did attempt to clear some of the bubbles with tapping and this may have made it come off easier. Hopefully it won't fade. If I have to paint the top to match its not the end of the world but did wonder if it's possible to effectively sand the top 1 mm off and save the painting.

 

[cjard]

Given the choice between sanding concrete and dyeing it, I'd dye it.. sanding will destroy he surface look you're going for, be hard, takes ages and make a horrendous mess

 

[Manziclan]

I'm with you on the choice. I had only seen dyes that go in the mix but will have a hunt for dyes to be applied to in situ stuff and go from there - thanks

 

[tomfe]

Wet it and have a look at the colour, then use a sutable sealer to get the colour you are after, a wet look or a more matt look.

 

[Manziclan]

Thanks tomfe - just to be clear are you saying wet it, and then if the colour goes okay to seal it then with the moisture in? Thanks.
Will have a play this evening

 

[Newboy]

No - let it dry then seal it

 

[Manziclan]

Okay - will have a bash tonight. Thanks to all.

 

[^woody^]

Varnish will give a wet look better than l'oreal. It will be worth it.

 

[Manziclan]

well - its wet and its dark. Not sure if the varnish comment is legit but its looking good so far!

 

[sprite1275]

well - its wet and its dark. Not sure if the varnish comment is legit but its looking good so far!

Pics?

How hard is it to polish concrete up? I'm in need of a hearth and wouldn't mind something like this but smooth polished.

 

[Manziclan]

Pics?

How hard is it to polish concrete up? I'm in need of a hearth and wouldn't mind something like this but smooth polished.

we aren't after the shiny look but I think it would be fairly straighforward. I did consider making the slab upside down in a form based on OSB or melanine as that would probably give a smoother finish. Pic is attached and it seems to be drying back out but not as light as previously so might try this for a few times before finally sealing - thanks all for the tips, much appreciated.

IMG_20161115_221642

• Manziclan
• 15 Nov 2016

 

[Manziclan]

IMG_20161120_171636

• Manziclan
• 21 Nov 2016

Update and next question.

The wall behind on the right wasn't plasterboard but was a plywood wall board. We have removed this and plan to move all the rest along that side of the room. On the wall there are a few holes left by the wiring or just holes etc that we plan to fill. Once that and the pointing has been done we plan to paint the wall and leave as is then tile up to around 1m to cover the area behind the burner on both walls. This is more about the look rather than combustibles as the wall isn't combustible.

Question is around the hole filling and pointing. Plan to use bonding for the biggies and a pointing/mortar missing for the pointing. Do I need to add anything to the mix given it will be close to the fire. Its going to be around 300 mm behind the appliance so yes to warm, but not very vary hot. It will like I say also be tiled over. Just want to make sure it doesn't crumble or blow over time.

Thanks all.