Poor Floor Grinding

[Blueford99]

Firstly, I only have myself to blame, but I recently decided to redo my garage and floor (500sq ft). The floor was in decent shape but had some stains and cracks. After filling cracks I rented a grinder from Sunbelt and they insisted I wanted the 7" Edco Concrete Edger. They gave me the electric version as it was all they had, it really struggled to have any effect on the floor without a good amount of weight. After 10 hours I had passed over the whole floor and only low spots remained which I had read was not too consequential from an adhesion stand point. After beginning to clean I realized the grinder left some pretty considerable pits and waves from where I ended my rows. The small diameter cup also made achieving uniform level very challenging. My question is how poorly will this look after I epoxy over it. I am not expecting or care to have a professional level finish as if I did I would have hired a professional.

 

[cgrutt]

Are those ruts in second pic or just dust?

Maybe going over with a hand grinder (7") with diamond wheel will blend some of those marks left by EDCO? Does epoxy have any pigment/color to it? That may also blend in the scuffs. Good luck.

ETA you may also be able to rent a floor polisher with diamond wheel to blend some of those marks out.

 

[Blueford99]

Are those ruts in second pic or just dust?

Maybe going over with a hand grinder (7") with diamond wheel will blend some of those marks left by EDCO? Does epoxy have any pigment/color to it? That may also blend in the scuffs. Good luck.

ETA you may also be able to rent a floor polisher with diamond wheel to blend some of those marks out.

The streaks on the sides are mostly just in the dust from the edge of the grinder, a few of them have a very slight rut that is barely detectable with your hand. A little confused why the stopping point left such deep ruts given I tried to immediately lift the grinder blade off the floor once I reached the end to prevent that. I am using a dark gray epoxy with black and white chips, I got 4X the recommended amount of chips as I want a near full coverage, hoping that will also hide some of the marks.

 

[cgrutt]

It almost looks like it was pulled away too fast before it had a chance to fully grind at your stopping point.

Also can you swing/shuffle rental side to side? It looks like you're grinding pretty much straight up and down. Moving side to side will help blend the "rows" together. If that's not possible maybe make more of an overlap.

I "think" the colored epoxy will hide alot of that but I'm not positive about that.

 

[Blueford99]

It almost looks like it was pulled away too fast before it had a chance to fully grind at your stopping point.

Also can you swing/shuffle rental side to side? It looks like you're grinding pretty much straight up and down. Moving side to side will help blend the "rows" together. If that's not possible maybe make more of an overlap.

I "think" the colored epoxy will hide alot of that but I'm not positive about that.

I no longer have the rental, but no it did not slide side to side very well. I had assisted someone on grinding a floor before but they had a wider machine that did shuffle well and grinded under its on weight, without applying pressure to this grinder it looked as if I was just taking 180 grit sandpaper to the floor. Luckily the area with the most divots will be completely covered by toolboxes, work bench, etc. I planned on putting the rustoleum recoat primer down before the epoxy to avoid the epoxy seeping into the porous concrete too much but after reading some on here it seems that may not be a good idea. This is what I get for trying to do the right prep rather than just etching the sealed concrete lol

 

[Shea]

I no longer have the rental, but no it did not slide side to side very well. I had assisted someone on grinding a floor before but they had a wider machine that did shuffle well and grinded under its on weight, without applying pressure to this grinder it looked as if I was just taking 180 grit sandpaper to the floor. Luckily the area with the most divots will be completely covered by toolboxes, work bench, etc. I planned on putting the rustoleum recoat primer down before the epoxy to avoid the epoxy seeping into the porous concrete too much but after reading some on here it seems that may not be a good idea. This is what I get for trying to do the right prep rather than just etching the sealed concrete lol

When grinding, it's imperative that smaller machines swing side to side as you move back or forward. Otherwise, you create furrows in the concrete. Also, what epoxy products are you using exactly?

Lastly, DO NOT use Rust-Oleum Recoat Primer. Its use is for sealed bare concrete or previously coated floors. Furthermore, it's a type of acrylic (not epoxy) and will not achieve the same bond as epoxy. It's Rust-Oleum's "magic" solution for those who want to skip the proper surface preparation of sealed concrete or coated concrete so that they can sell more of their kits.

 

[cgrutt]

Not sure if something like this would work or not. I'd try to blend all of the larger swirls, etc together as much as possible before applying your epoxy. You could probably pick up an inexpensive grinder at Harbor Freight or rent one if you dont have one. Believe the diamond cup was about $100 at home depot. I think its Makita. The dust shroud was not that expensive (maybe $60?) and actually works pretty good. My grinder is Bosch.

 

[Blueford99]

When grinding, it's imperative that smaller machines swing side to side as you move back or forward. Otherwise, you create furrows in the concrete. Also, what epoxy products are you using exactly?

Lastly, DO NOT use Rust-Oleum Recoat Primer. Its use is for sealed bare concrete or previously coated floors. Furthermore, it's a type of acrylic (not epoxy) and will not achieve the same bond as epoxy. It's Rust-Oleum's "magic" solution for those who want to skip the proper surface preparation of sealed concrete or coated concrete so that they can sell more of their kits.

Ya that is what I gathered from other people on here regarding the Recoat Primer, I will skip that. As far as the side to side I think the machine just was a poor option. It was called an Edger not a Grinder and I think that is because it was designed for just that, the edges. If I could go back I would insist on a bigger machine from Sunbelt considering getting a trailer and hauling it to my house is not a problem and it would have been well worth the extra $150.

 

[Blueford99]

Not sure if something like this would work or not. I'd try to blend all of the larger swirls, etc together as much as possible before applying your epoxy. You could probably pick up an inexpensive grinder at Harbor Freight or rent one if you dont have one. Believe the diamond cup was about $100 at home depot. I think its Makita. The dust shroud was not that expensive (maybe $60?) and actually works pretty good. My grinder is Bosch.

Thanks for the tip, I do have a grinder, would need to get the diamond cup. I will examine the floor further and determine if its worth the dust. I have spent 5 hours cleaning thus far and cannot seem to get rid of the dust no matter what. May not be worth reintroducing it all but I may need to. Its currently -22 F* real feel here but the slab is still at 55*, it is supposed to be 65* this weekend so I was hoping to get the floors down in a few days which leaves me little time left to remove all the dust created or let the slab dry if I use water to clean it.

 

[FJ4FUN]

Sent you a PM

 

[Steve_P]

I don't know the answer to the OPs question, but the commercial units that they use for grinding the big box store floors typically use three phase power, they run them on massive generators, and they can have a 20+ HP motor on them. If not electric, they can use a propane powered piston engine, also that power level. The cutters rotate on their axis and then the circular deck they mount to also rotates; this prevents the "engine turned" look you're getting. So yeah, as you surmised, you got the tiny machine that they use to grind up next to the wall and you needed the big gas or propane powered unit.