Colouring Concrete

[skylined_gtr]

Hi All,

Hoping you can offer some advice!

I'm laying a concrete pad (roughly 3.5m x 2.5m x 150mm/6"). Trouble is, I want coloured concrete (a dark gray heading towards a light black) with exposed aggregate. So what I was going to do was get a coloured ready mix in, lay it and tamp it level to get as much fat to the surface as possible, then press the exposed aggregate mix in on the top whilst bull-floating, wait for it to stiffen up a bit, then brush off with water to expose the aggregate.

Problem is that I have phoned a few ready mix companies, they don't do coloured concrete. The options I see are:

1. Self-mix/Mix it myself with the colour mixed in
2. Add colour to the ready mix in each wheel barrow, give it a quick mix with a shovel or drill with mixing spatula before pouring into the pad
3. Use a powder based stain/hardener with the colour I want

Anyone got any other suggestions or can anyone recommend a preferred option?

Cheers

 

[JohnD]

I suppose you could lay most of the depth in readimix, then (while it is still fresh) add a layer of your fancy finish.

It will be hard to get even colour mix without a mixer.

 

[r896neo]

You need to persevere and find a readymix outfit who will do it. The big factor in exposed aggregate is the matrix colour, you can have lovely coloured stone and have it ruined by a dull matrix.

If you cant get anyone to do it like john says putting down 100mm of standard readymix and then 50 of your own mix will work especially if you get a dose of retarder in the readymix. You need to be accurate and weigh out the colour additive fir each gauge.

Finding a plant that will do it will take all the risk and possible problems out of it.

 

[skylined_gtr]

Thanks for the advice, I'm still having trouble finding a coloured ready mix so I think the best idea is the one you've both suggested which is to do a 100mm of readymix with a retarder and 50mm of selfmix coloured on top.

I'll vibrate the air pockets out of the 100mm readymix before laying the top 50mm down but I take the risk of the 50mm layer having air pockets trapped in it. Can't vibrate that 50mm layer with the poker because it will pick up the grey from bottom 100mm layer and bleed it to the top as I pull the poker out.

 

[r896neo]

Vibration is uneccessary for that sort of thickness, a simple tamping will be fine.

As for the top layer you really shouldnt vibrate or tamp exposed aggregate concrete anyway as it sinks the aggregate from the surface. You want to screed it using an aluminium or magnesium bar.

Get as many hands to the pump as you can to get the colour mix knocked up quick. You could even premix some of it if you confident your readymix will be on time, or at least have it batched with the weighed colour and cement for each gauge etc ready to go. Even at only 50mm thick its about 0.8cu, you will be mixing for a couple of hours at least

If you could find a way to stay off it after laying the bottom backing concrete, ie place and screed it off floating planks etc you could bring the top layer down to as little as 25mm. The thinner you go the more the risk though.

Where are you in the uk? Im amazed no-one will do exposed agg readymix near you

 

[skylined_gtr]

Cheers, good to know, so if I give the top layer a good tamp, should hopefully be ok.

I wasn't going to do an exposed aggregate pour, I was going to have a coloured readymix in with normal aggregate, then vibrate it to bring a bit of fat to the surface, then throw exposed aggregate over the top and bull float it in, then after a bit of drying, pressure wash/brush to expose the aggregate then seal once fully dry. Sort of like what this chappy has done here

I can get readymix no probs but I can't get a coloured readymix. I'm in PE19