concrete for grinding / polishing

[LD1]

Well, I think I have made my descision after consulting everyone on my call list.

I called the people that did the grinding and polishing in the earlier picture. For a garage floor, his advise was a 40 grit finish. He said you will still be able to see some scratch marks, but you would have to really get down in the light just right. So it sounds not too smooth and not too rough. And that if I needed to hog a bunch off high spots to get 16 grit, but the 40 will do it all, just be a little slower.

Since the stones cost extra to rent, I think I am gonna shoot for a saturday rental that way I have all weekend to put 8 hrs on the machine if its a metered rate, and can get more "free" time if it isnt a metered rate. That will give me a full week of cure.

 

[s219]

How high are the high spots if you had to estimate, and how wide? Are we talking trip hazards or just something that would affect rolling carts? At a minimum, I'd wait 5-6 days until it has an initial cure and then look at it again to re-evaluate (I assume its under plastic right now). It may look better than you think, then again, it could be worse . But past experience has shown me it's good to step back for a bit and then think over the options rather than foam at the mouth right away (not always easy). When we troweled my barn floor there were a couple areas where it wasn't quite perfect, but I don't even notice/care anymore, especially after a year of use, dirt, grime, oil spots, etc.

We had a concrete floor ground down and sealed where I work, and it looks awesome -- looks classy. But it's in the foyer of a building. Not sure how well it would do in a shop. Especially the sealer. I don't have a feel for how a ground floor would hold up in a shop environment with or without sealer.

 

[EddieWalker]

When renting, I've always picked up a lot more of the disposables then I figure I needed and I also find that going with the most aggressive ones first seems to be what I use the most. If you do not use it, you get your money back when you return the machine. If you think you will need 3 sets of stones, bring home at least 6 and return what you don't use.

Eddie

 

[LD1]

How high are the high spots if you had to estimate, and how wide? Are we talking trip hazards or just something that would affect rolling carts? At a minimum, I'd wait 5-6 days until it has an initial cure and then look at it again to re-evaluate (I assume its under plastic right now). It may look better than you think, then again, it could be worse . But past experience has shown me it's good to step back for a bit and then think over the options rather than foam at the mouth right away (not always easy). When we troweled my barn floor there were a couple areas where it wasn't quite perfect, but I don't even notice/care anymore, especially after a year of use, dirt, grime, oil spots, etc.

We had a concrete floor ground down and sealed where I work, and it looks awesome -- looks classy. But it's in the foyer of a building. Not sure how well it would do in a shop. Especially the sealer. I don't have a feel for how a ground floor would hold up in a shop environment with or without sealer.

the high spots arent bad. Just enough that water dont make it to the drain in certain areas. Certainly nothing that would be a trip hazard or effect rolling a cart. Maybe 1/2" over a 5-10 sq ft area.

No its not under plastic. Continuous rain in the forecast and I am keeping it hosed down in between rains though.

When renting, I've always picked up a lot more of the disposables then I figure I needed and I also find that going with the most aggressive ones first seems to be what I use the most. If you do not use it, you get your money back when you return the machine. If you think you will need 3 sets of stones, bring home at least 6 and return what you don't use.

Eddie

No stones. Everywhere I am calling has dymaserts or diamond wheels. And they are super expensive to buy, and almost equally expensive to rent for the day. I just reserved a single 17" head electric grinder for the weekend for $125. Worth a try.

 

[EddieWalker]

Post pics, I'm not familiar with that and I'm interested in your results

Eddie

 

[Streetcar]

When I say a wet load I may be exaggerating. It was wetter than I would have liked. But have poured and seen poured even wetter. This was maybe a 6-7 slump. And the concrete was pretty well set when the rain hit. Then it was off and on. I am no expert, but I dont think I hurt the floor any, just the finish. Which is why I am inquiring about grinding. I did some calling this morning. But am only left with more questions.

How long before I can grind? If more than 5 days, I may wait and proceed with building first.

Not sure what grinder I need, and what wheel. What grit? Flapper or diamond? Dual or single head? This is 40x40. I want something that wont take forever to remove the few high spots, but also leave a good finish. But will get different grits if need be. And would like to get this done in a day. And with never doing this, I dont want something that is gonna leave ridges where I remove high spots and try to taper back out to the rest of the floor. So what would be easier to NOT leave ridges, a single head or double?

LD1
I had similar issue of rain hitting as concrete achieved its initial set. The top 1/8" of the slab was compromised.
My slab is outside storage so flaking and dust is not an issue. In a garage it would be another story.

 

[s219]

the high spots arent bad. Just enough that water dont make it to the drain in certain areas. Certainly nothing that would be a trip hazard or effect rolling a cart. Maybe 1/2" over a 5-10 sq ft area.

So that's not so bad other than maybe for drainage. But I guess one advantage of grinding is that you can get the surface down to a uniform hardness if there was any concern about the rain affecting the top surface durability.

 

[mjcountrybumpkin]

I really hope you got a grinding wheel and not the dima-serts( not spelled right). We ground 40,000 sq ft. With several machines a few years ago. After about 3 days, we stopped using the dima- sett heads all together.

If you grind any grind it all. Make the entire surface have a same finish then epoxy coat (after 30 day cure)and you'll be really happy.

 

[LD1]

I really hope you got a grinding wheel and not the dima-serts( not spelled right). We ground 40,000 sq ft. With several machines a few years ago. After about 3 days, we stopped using the dima- sett heads all together.

If you grind any grind it all. Make the entire surface have a same finish then epoxy coat (after 30 day cure)and you'll be really happy.

The one that I am renting, the way the guy describes it is one big 17" diamond wheel. I am gonna look at it friday night and if I like it, I will take it for the weekend.

Still no plans on epoxy though.

 

[mjcountrybumpkin]

The single grinding wheel design works excellent.
If you grind the surface of the concrete and do not want an epoxy, look at a densifier. The grinding of the surface will "soften" it a lot. A Densifier will fill in the microscopic voids and strengthen it.