After considering epoxy and cement-based leveling for my shop floor, I'm now thinking maybe all I need is to grind it and seal it. I can rent an Edco 2-wheel grinder locally for $150/day. I figure I'd need to remove about 1/8" on average over the 400 square feet to get it as smooth and level as I'd like. The manufacturer says this grinder can remove 1/32" over 350-500 feet per hour. Four-plus hours of grinding sounds like a bit of a slog, but if it turned out well, probably worth it. I got 'resurfacing' (grind, level, epoxy coat) estimates from $4.50 to $7.50 per square foot.
Anyone have experience and advice about grinding concrete floors?
Mark, the amount removed per hour will vary widely depending on the hardness of the surface. Some concrete floor surfaces are fairly soft, and others are very hard. You can geta bit of an idea by rubbing the clean surface with your hand...if your hand comes up with a lot of concrete dust on it you can assume the surface is fairly soft and will grind pretty quickly. I assume the Edco grinder is using non-diamond grinding stones? If that's the case, you want to buy a few bags of silica sand to use while grinding. you broadcast the sand on the floor before grinding....it helps keep the stones clean (much like chalking a file keeps the swarf buildup down) The sand also acts like an additional grinding agent. Just run the grinder back and forth like a floor buffer and check your results every few minutes, by sweeping things clean and seeing what you have. If you want a really slick finish, you'll probably have to go to diamonds at some point, but you can get a decent finish with just the carborundum stones. Once you have the finish you're happy with, apply an acid hardener to the floor....that will harden and densify the surface, and is a one-time application. Some people harden before diamond-grinding...it helps get a very slick finish. If you decide to stop with just a satin-type finish, and then harden, you can apply a sealer to the hardened surface which will give more gloss, and will fill some of the pores and minor pits left in the finish. The sealer will go farther on the hardened surface, as the hardening tends to seal the pores and prevent the sealer from soaking into the surface. If you want to forego using the sealer...no problem....the hardened surface alone is resistant to the penetration of spilled chemicals like oil, and they can usually be simply wiped up. You can also get acid hardeners that are colored, if you'd like to permanently color the floor. A few years ago, I had a customer that runs a Jaguar car shop. He decided to go with an acid hardener, but he wanted a Jag-Green floor, too. That was before acid-coloring had come along, so he tried adding Rit clothing dye to the acid. It worked very well, but he didn't use enough dye, so it's a faint green. He may be one of the very first people to use color with the acid hardener.
Be sure and use a dust mask if it starts getting dusty in your shop.....there is silica in the concrete, and you're also using silica sand in the girnding process.....silica dust is a good thing to keep out of your lungs, if possible.
The non-color hardener I've used the most is "Lapidolith" by Sonneborn. Any good concrete accessory-supply business should be able to order it for you, or know of a comparable substitute.
Jim
