diamond grinding pads - concrete/granite
 

I have a small piece of pigmented concrete (3'x1.5') that I want to grind/polish to expose the aggregate and polish - ultimately buff with some beeswax. I'm thinking there's gotta be some stone/granite guys out there that have some experience here.

I don't have a variable speed grinder/polisher (although I want one)....do you think this can be done by hand? I'm planning on working thru a grit ranging from 120-1200. I do have an automotive buffer to apply the wax.

Will I kill myself trying to wet sand this by hand? I don't really want to drop 300 bucks on a grinder and another 300 bucks on diamond pads to clean up 4.5 sf of concrete.....but maybe it's unrealistic to think I could use this...
http://www.dkhardware.com/product-1494-z2set-3m153-flexible-diamond-hand-pad-set.html


I eventually plan to attempt a concrete countertop - which would require the grinder/pad purchase but I'm not quite there yet. Any opinions?

Is 3M the consensus product as well (for diamond pads)? Thanks for the help.

I've seen round stone polishing sand paper discs that could be used with an orbital sander. If you don't have one, you could borrow mine to see if it would work for you.

We have a small section of concrete that was used as a patch in my Maple floor at my building. when we refinished the floor the floor sanders went over it and exposed the aggregate. It looks pretty good.

I think good quality sandpaper in a belt sander will work fine.

I don't think an orbital is aggressive enough.

Tom W

Thanks
 

for the suggestions - another thing I just considered is renting a right angle grinder for a day?

I do have a palm sander - but I just figured the concrete would chew up the expensive sandpaper too fast (hence the diamond pads) and I assumed I needed a variable speed to keep the RPMS down for polishing with fine grits?

Can you wet sand with a belt sander? Seems like it would mess the tool up as the belt throws water everywhere.

I suppose I could just try it with carbide sandpaper on my palm sander (and water) and find out...


This is for a concrete coffee table - by the way.

The only concrete I've polished was the basement floor in my dad's house. I used a floor buffer like Tom mentioned and wet sanded the floor with 2 grades of screens, then buffed it with floor wax. It ended up with a satin finish that was nice but I imagine more sanding would have allowed a high gloss finish.

3M makes diamond impregnated sponges in varying grits, about $20 apiece. Maybe you could find some outfit to get it in the ballpark with their equipment and finish it with the sponges.

You can do some polishing with an angle grinder and diamond pads ( see www.braxtonbragg.com ). Just keep a bottle of water handy to keep the concrete wet.
HD has a dewalt grinder for about $40, might be cheap enough to just buy, but the pads are expensive.
4sq ft is not a lot, but it's not a little either. You couldn't do it with granite, but concrete is much softer so it might work. I don't have much exp with concrete.

BB also has grinding stones and cup wheels if you wanted to try that.

I would rule out doing it totally by hand.

I would also try an angle grinder, pads, and plenty of water (perhaps a steady dribble from a bucket above? ...maybe run some vacuum line close to the stone and dribble it that way) Gonna be messy...buy an apron too. Probably take more than a day too.

Good luck...take pictures!

Thanks guys.....I have a nice dewalt angle grinder and I considered using it.....but I was afraid I couldn't control the rpm's and I'd botch it up. I think I may try that on the underside of the coffee table (obviously not visible) and see how it goes.....and then try regular (wet) sandpaper in my palm sander up top - at least just to start out. Member BillyBob also PM'd me a great website too - I'll have to check that out.

I'll post pics when I'm done - right now it's a work in progress. I cast wood legs into (I was originally going to stain them to match my new pergo floor) for ease and to keep the weight down.....but aesthetically - it looks like hell. It's this massive chunk of concrete with little wimpy legs - so I'm going to encase the legs with concrete now and beef it up.

Also, it should be noted that I'm an engineer (not an architect) and the results could be disastrous:).

I think the angle grinder will be very hard to control.

Tom W

An air powered angle grinder with a water hookup is what's used to polish granite edge details. Or a giant router type deal for the fancier edges.

In a pinch, our installers used to use regular grinders with the water bottle, which I did once when a splash was mistakenly cut to fit on the polished side.

I ground over 1000 sq feet of concrete with a right-angle grinder attached to a shop vac with no problems. I think that's the best way to do it. For only 4 sq feet I'd rent one for a day. Don't worry about RPM's (on mine they're not manually adjustable anyway) and just apply very light pressure and keep the grinder going in circular motion. Don't let it rest in one spot while it's spinning.

Might I ask what that was for? I think I'm gonna buy the right angle grinder/polisher in the future - but I tried it last night with my palm sander and some 120 grit sandpaper - and I exposed the aggregate with relative success......I think the concrete is still a little too green though - so I'm going to wait until the weekend to try it further (around 8 days old then).

Having said that - it destroyed the sandpaper in a couple of minutes (even with water) - so this obviously wouldn't work for 1000 sf but for only 4, I don't mind spending $30 in sandpaper.

Yeah, sandpaper might work for just 4 sq feet but that's about it.

My project was about removing nasty water stains from my concrete patio and it took me about a year, working mostly several hours each weekend. The patio was done by a rather dishonest contractor one year in November just couple days before a storm that blew the blankets away and brought rain which then froze on the surface before the concrete had a chance to fully cure, leaving permanent dark stains. Now after the grinding the patio looks decent.

do you have an equipment rental company near you? there are several ways you could do it. there is a concrete grinder that uses either diamond or concret inserts. Another way would be a floor sander. my company www.sustateequipment.com rents both of these and also we carry the sandpaper for the sander.