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istaticl 10-28-2011 11:29 AM

Another DIY Concrete Polish Job
Hi all,
I've been looking over this forum and the internet for some insight into polished concrete and I still have some lingering questions. My current floor situation includes about 350 sq ft. of post-tensioned concrete slab built in 2003. The surface is already fairly smooth minus some patches and a 10' long 1/16-1/8" crack that runs through the center of the slab. I don't want to color the concrete and I don't need it to be a glass like 1500-3000-grit finish. I talked to a local concrete grinder and he said you can stop at around 400-800-grit and have a nice satin finish; this is what I am aiming for. My plan is to fill the tack strip holes and crack with kwickcrete and then rent a dual wheel (three heads per wheel) oscillating floor grinder with that comes with Norton 2x2x4 10-grit rub bricks. I was told the bricks on this machine will give me a "baby's butt smooth" finish. After the first cut with the 10-grit I am planing on using a 5" hand grinder to finish the surface to about 400-800 grit.

Now to a few questions for those who have experience with polished concrete.
1.) I've read that after the first concrete grinding pass which removes the top layer of concrete paste millions of tiny air holes will be exposed. If these are not filled before the hardening (densifing) process then the final polished concrete floor will show these unsightly imperfections. I've read the holes can be filled with an acrylic tile adhesive type of product mixed with either the grinding dust or cement powder which is hand scraped across the floor using a trowel.

So it sounds like the process should be:
1.) Prep slab (fill holes and cracks with kwikcrete)
2.) First Cut with 10-grit floor grinder.
3.) Hand-trowel acrylic tile adhesive mixed with grinding dust over the entire surface. (mixture ratio?)
4.) Second cut with 50-grit hand grinder.
5.) Apply kwikcrete natural penetrating silicone sealer
6.) Third cut 100-grit hand grinder.
7.) Polish up to 400-800 grit.

One issue I am concerned about is if the 10-grit oscillating grinder will indeed make my existing smooth slab even smoother, or if I should skip the 10-grit cut and proceed straight to 50-grit hand grinding. Will the 10-grit grinder really make it "baby's butt smooth" as the local rental shop told me? They also carry 24-grit rub blocks for the machine, but the guy told me that customers generally can't tell the difference between 10 and 24 grit grinds.

Any help/insight is very appreciated. Thanks for looking.

Bud Cline 10-28-2011 11:36 AM

There are members here that polish concrete professionally so stand by.

I would think the twenty-four grit wouldn't do anything but scratch the concrete and create more work. That's been my experience using 24 grit sandpapers on floor machines but the stones may act differently.:)

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