Polishing Cement

[mustardman]

Hi Guys,

I know this is odd as it says non hearth posts, but this is for help relating to how do I polish concrete. I am making a hearth pad about inches thick by pooring concrete, but since I DIY for almost everything i am looking for a solution at how to finish the concrete. Will regular sand paper work starting from 60 grit up to 1500 grit?

I would also like to know if normal sand cement would work. ABout 7 bucks a bag. My hearth is going to be 2 inches thick.

Thanks

 

[bmblank]

Look up concrete counter tops. Many people do it. My brothers hearth and counter tops, my counter tops..
Basically ours are made by building a mold out of melamine (same stuff pre made shelves are made out of) and pouring the countertop upside down. The melamine makes a good starting point to polish from. You're going to want a wet sander and use diamond polishing pads, starting at probably the 100 grit range and slowly going up to the 1200 grit range or so. Its a messy job, but final product is nice. When you're done you can polish up with some Carnuba out bees wax, out even turtle wax. And you should probably put some water sealer on there too.

 

[Highbeam]

There is special concrete mix for countertops/hearthpads. Also, special reinforcement measures since you don't want the thin slab cracking.

 

[semipro]

+1 on the countertop suggestion.
Also, make sure you use a steel trowel for the final finish of concrete. Done with the proper technique and timing this can give you a very smooth finish.

 

[Highbeam]

+1 on the countertop suggestion.
Also, make sure you use a steel trowel for the final finish of concrete. Done with the proper technique and timing this can give you a very smooth finish.

From what I understand, you actually pour the slab upside down. The steel troweling would be on the bottom. The finished surface is against the smooth form. Be sure to tamp, tap, hit the form so that there are no bubbles.

 

[semipro]

From what I understand, you actually pour the slab upside down. The steel troweling would be on the bottom. The finished surface is against the smooth form. Be sure to tamp, tap, hit the form so that there are no bubbles.

Agreed. I should have clarified.
I'm just saying that if you pour in place and finish with a steel trowel that you could get a very smooth surface. Then I think some of the polishing methods uses to finish counter tops could be used.

 

[bmblank]

There is concrete made just for countertops, but its not totally necessary. I like the looks of mine. In fact, it looks pretty cool bringing some of the aggravate out with the polishing.

 

[mustardman]

hi Guys,

This is all great input. I am going to be pooring directly in place. My only issue is i do not have all the diamond blades and stuff to polish, which is why I wanted a realistic opinion if I can polish this by using a normal orbital sander.

 

[bmblank]

You can do it but you will go through many sanding disks and it will be dustier than a dickens. I would suggest renting a wet sander if you can find one. And like everybody has said, get it as close to finished as you can while its still wet.

 

[mustardman]

When you say its still wet you mean before it is cured right

 

[bmblank]

Yes. If you trowel it while it is harder, but still not yet cured, you can get a nice smooth start.

 

[mustardman]

sounds really cool. I cant wait to test it out. Any idea on where to buy sealers or hardners ?

 

[Highbeam]

Yes. If you trowel it while it is harder, but still not yet cured, you can get a nice smooth start.

I had some interior concrete floors poured at my home and we steel troweled the bajeepers out of it to create what I think is a really cool finish. You just keep scrubbing it with that steel trowel and you will see it get darker and darker. The strokes of your steel burn swirls into the surface that really pop out when you seal it.

If you keep scrubbing you will end up with a burnt slab that is all black like a chalk board.

 

[mustardman]

Very cool,

Whats the Frog ?

 

[btuser]

You have to be careful when finishing concrete. If you trowel too early you will end up with a very brittle surface.

 

[Dave A.]

The finished surface is against the smooth form. Be sure to tamp, tap, hit the form so that there are no bubbles.

Haven't done this myself, just watched a video. Agree about the form and getting rid of the bubbles, I think they used a vibrating sander just pressed against the form. But you still will get some bubbles so you need to use a grout (thin concrete) to fill in the small imperfections after removing from the form and before the polishing.

 

[Highbeam]

Very cool,

Whats the Frog ?

That's just a little guy I found while mowing the lawn. We get some teensy weensy frogs out here. Not much to eat on one though, it takes thousands to make a good sammich.

 

[mustardman]

about how long do you think i need to wait until start to trowel. I am just going to be using normal sandmix cement