Exposed Aggregate Color

Old 07-21-09, 12:41 PM
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Location: Edmonton Alberta Canada
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Exposed Aggregate Color

We are pouring our front stairs and driveway. It will be an exposed aggregate finish. However, we are interested in a grey overall color. Standard exposed aggregate is brown (based on the sand color). Do we then need to order different sand/rock to achieve the grey color? Or is this an integral color we add to the mix? Or can we possibly achieve the grey by tinting the sealer? Any advice/recommendations would be appreciated! Thanks!
Old 07-21-09, 06:29 PM
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If you don't seal the exposed agg, or use a crappy sealer like Thompson's, the slab will look gray. If you use a glossy sealer, the browns of the gravel and sand will show up.
Integrally coloring the concrete gray will not help. The color tints the paste, not the gravel. When you wash the paste off (expose the aggregate), you're washing off your gray coloring.
If you use a gray tinted sealer, it will look like you painted your concrete gray. The gravel will be the same gray color as the paste.
Your idea about ordering special sand and gray gravel is probably your best bet.

Last edited by Pecos; 07-21-09 at 06:31 PM. Reason: additional info
Old 07-21-09, 07:10 PM
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Exposed Aggregate Color

Around here, a contractor will just order a "Mac Donald's mix" which is commonly used at the restaurants and most patios. It is a stock concrete mix that is available on call from any good ready-mix supplier. - It is rounded river rock (under 1/2"or so), natural sand and cement with no pigments. It is available only in 4000 psi and is air entrained because of the durability required for the climate.

My contractor friend used it on my patio and miss-labeled the retarder spray tank and used a curing compound because he was quickly leaving on a fishing trip. The crew recognized it the next morning when they showed up in the morning to wash it. They tore out the small 12x20 patio, reformed it, ordered the stock mix from the ready mix supplier and had it finished by noon or 1:00 that afternoon because it was a standard mix - They were in a hurry to get fishing and paid their son to wash and brush the patio. My friend never mentioned the error, but the crew still laughs about it.

There is much to be said for using standard readily available materials from a cost and completion standpoint.

Casting or seeding plain concrete is a totally uncontrolled way of creating a proper appearance for something that will be visual.

Coatings are temporary and highly variable.

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