mfank

My front pourch was recenly extended another 15'. The extension has a less than smooth finish. There are some trowel lines, and small things that make the surface look less than professional up close. Is there any way of fixing the surface of the concrete short of taking out the whole slab?

glennjanie

Welcome MFank:
Yes, it can be ground down with a machine from the rental store. There is one with 6 concrete grinding rocks on 2 rotating shafts. The rocks last longer and there is not any carcinogenic dust if you keep the floor wet while grinding.
Glenn

mfank

How clean does the grinder make the surface look? And do you have any recommendations as to brands/make/models? Just to give me a start to see where I can rent one.

It was also suggested I could cover the concrete porch with another layer of concrete. Now knowing a bit about thermal expansion coefficients, I immediately thought this was a bad idea, but if the two materials bonded, and could act as one it may work. I figured I'd ask anyway.

glennjanie

Hello MFrank:
The grinder will make the rocks in the concrete show and make the finish almost slick but you will see the grinder's circular marks in it. Think of a Terrazo floor; that's how they make them. Or think of the road milling lines on a concrete highway where they have smoothed out a rough spot.
You may place new concrete on top of the whole thing; just make sure you clean the surface well first, use an epoxy bonding agent, and use at least 2" of additional concrete; anything thinner will pop off and crack.
Glenn

mfank

The entire surface isn't horribly rough, it is just has a few high spots, and up against the house it is very rough. Is there a way to just grind these spots? Perhaps a smaller tool? And what about the spot near the house? We aren't thrilled at the possibility of having it multi colored.

I ask for small tools because the only thing I found was this. Granted there are more places I could try but this was the 1st and the closest I've found thus far.

http://catalogs.shoplocal.com/rscrental/index.aspx?pagename=moreinfo&zipcode=&storeid=1043 018&dssid=10965985-ca15-4f56-9e3f-7b9c216a4d72&fsid=c79d41f4-1154-495d-a24e-5bb7fa65dc4d&uniqueid=13778474&circularid=12727

glennjanie

I see what you mean, yes there is a smaller machine but the process goes very slow. You wouldn't want a small hand-held model.
You won't have a lot of multicolor, just multitextrue. Where you grind the trowel marks off will remove the 'soupy' part of the concrete and expose some stones.
You spoke of VERY rough near the house; are there rocks sticking up? You may want to rent an electric hammer with a busch head bit (looks like a meat tenderizer), it will cut the extreme rough stuff off quickly.
Glenn