# Grinding rough concrete



## Disgustipater (Oct 13, 2016)

It wont let me link to the pictures.


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## de-nagorg (Feb 23, 2014)

Use a wet grinder with a diamond cup.

And keep it moving, it will grind a big scar quite quickly if you don't.


ED


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## Canarywood1 (May 5, 2012)

That looks like it was gone over with a float or a darby, should have at least been bull floated and broomed, i don't think it's a good idea to start grinding it, your going to expose the coarse aggregate if you do, probably best to leave well enough alone, your call though.


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## DIYknot (Oct 2, 2016)

At that size, I would just rent a concrete grinder.


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## Bud9051 (Nov 11, 2015)

The trowel marks you see are mostly just the liquid portion of the mix and will sand off rather easily. I would hesitate learning how to run a large grinder as mentioned you could do more harm than good. Talk to your local rental store/s to see what they recommend and have. I have rented a rectangular flat pad sander for a wood floor and although slow it would never get out of control. They are about 120 pounds and 20" x 20". But don't know if the rental would recommend them for concrete.

As for how smooth, you can take it down to very smooth if you want. But too smooth becomes slick when wet. Often they use a broom finish to avoid slick.

Drag a concrete block over it to see what it does to those lines.

Bud


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## Disgustipater (Oct 13, 2016)

Bud9051 said:


> As for how smooth, you can take it down to very smooth if you want. But too smooth becomes slick when wet. Often they use a broom finish to avoid slick.


It is going to be a shop, so it wont be getting wet.


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## jlhaslip (Dec 31, 2009)

A diamond stone on a grinder will be very aggressive and might be too harsh.
I would go with a Carborundum stone.

https://www.ohiopowertool.com/p-217...1-concretemetal-grinding-cup-stone-26012.aspx

The secret to using them is to always keep it moving and keep it flat to the surface.


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## stadry (Jun 20, 2009)

all of the above a good tips,,, i like the cinder block - never heard that 1 before,,, the best suggestion's the floor sander w/alum oxide sheets,,, 12 x 20's rather large for knee pads & rubbing blocks,,, or is for me at my age


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## Disgustipater (Oct 13, 2016)

jlhaslip said:


> A diamond stone on a grinder will be very aggressive and might be too harsh.
> I would go with a Carborundum stone.
> 
> https://www.ohiopowertool.com/p-217...1-concretemetal-grinding-cup-stone-26012.aspx
> ...


I ended up going this route, and it worked pretty well. It's not as smooth as garage floor, but it is definitely a lot smoother than it was before. Just fine for a shop.

Thanks all for the suggestions and info.


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## Bud9051 (Nov 11, 2015)

Thanks for the update. Once you tackle a job like that you realize how easily concrete can be polished. I finally bought a 4" diamond cup for my grinder and it makes fast work of smoothing any concrete.

Bud


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