Tangential topic: What goes into grout?

[Jholmes9]

I ask because I'm making my own concrete kitchen countertops. I've cast them in molds and they came out well, but there are a lot of small "bugholes" in the surfaces that need to be filled. The typical prescription is to fill them with a "slurry" of cement and pigment. It occurred to me that the properties needed of that "slurry" are really identical to those of tile grout. I can't use commercially prepared grout because the counters were cast using grey cement and dry pigments that won't match any commercial grout available. So, does anyone have a basic recipe for grout that might improve on my seat-of-the-pants combination of cement, pigment, a bit of sand...... ??

[bbcamp]

Portland cement, sand, pigments, and secret sauce. The grout companies guard their recipes jealously, so that's about all you'll get from them.

Since you mixed you own concrete, you have all the ingredients and proportions. Just leave out the aggregate, maybe grind your sand a little finer (don't ask me how).

[Jholmes9]

Thanks, Bob. I suspected as much about the 'secret sauce.' The sand I used for the concrete was the bagged "medium sand" that quickcrete sells for making mortar. It seemed fine enough when dry, but looks like gravel in a more grout-like mixture. I've got a bag of play sand sitting here, which I now see is much finer. Also, the great majority of the holes are under the 1/8" threshold, so unsanded "grout" may be just the thing. Cement, pigment and water; can it really be so simple?

[bbcamp]

I dunno. Maybe it's like sausage, everybody makes it, but nobody wants to know how.

Seriously, you are just patching little holes. Portland and pigment for the small ones, add little sand for bigger ones. The color may not be exact, but if you wipe you patching compound off the surface and leave it only in the holes, no one will notice.

[dgunnels]

I think Bob is 'spot on' with the recipe. BTW, don't use big words, Bob is the only one who knows what they mean.

[bbcamp]

...big words, Bob is the only one who knows what they mean.

And I'm just guessin'...

[Jholmes9]

What do you think about moisture management during curing? I'm a little concerned that the concrete, which is about a week and a half old, may wick too much water from the grout and weaken it. The slabs are outside right now. Thankfully we've got a couple of cloudy days ahead.

[bbcamp]

Wet the area, then wait for the water to wick into the concrete (no visible puddles). Spritz with water as soon as the patch hardens, then cover with plastic.

[Scooter]

You can make your own stuff--use Laticrete 4227 plus some very, very fine sand, like plaster sand, and pigment.

I'd probably spritz the area with a fine mist before "grouting".

[Jholmes9]

Thanks everyone. It's starting to smell like a plan.

[dgunnels]

How abouts some pics when you're done?

[Jholmes9]

Will do.

[Jholmes9]

Sorry it's been so long, but here are the photos I promised. The slurry of cement and pigment, plus sand for some larger holes, worked beautifully.

http://flickr.com/photos/donnatakesp...7594244828145/

[Alto]

Sweeet!!I hope you're pleased with it, as you well should be.