Concrete Grinding Advice--Prep for Full Flake Roll-on-Rock Kit

[nameyers11]

Hello everyone, and thanks advance for reading this.

I am afraid I may have messed up my garage floor, and could use some advice on what to do before making it any worse.
It's 380 sf, 30 years old, no cracks or large damage. Kit is 4195 epoxy (gray) with 5085 polyaspartic clear, full flake (gray/black small size). Previous homeowner had installed carpeting, and therefore I hired someone ~1 year ago to grind it off as I'd read that adhesive removal could be extremely difficult. I told the contractor I'd be putting in epoxy and he agreed to leave it ready for that.
Unfortunately my life got really hectic, and I wasn't able to get to it until recently. In the meantime my mother-in-law insisted on parking in there a few times, and it got a little dirty. I also noticed that the contractor didn't really patch anything and there were significant areas that needed it. I thought I would patch, then grind the patches off, as well as the few areas where some tire marks/grease seemed to be an issue.
I foolishly attempted to do this with a 4" grinder and a turbo cup wheel. Looked fine as I was working but afterward with a light from the side I saw this.

I realized my error of using the 4" grinder, and went to Harbor Freight and picked up this 7" grinder and cup wheel.
I then tried to use it on a separate area I had applied a vinyl concrete patch to, and noticed the same issue (creating grooves in the surface).

So, at this point, I'm not sure how to proceed. I know better than to try to "learn" with the 7" grinder on those areas I messed up before with the smaller one. I am no expert but I kept it very level and moving in circles the whole time with no added pressure, but it just ate into the surface almost instantly. Based on the videos I watched, and research I did, I expected it to be a pain using the 7" angle grinder, but would just be a matter of taking my time. I'm guessing the problem is related to the cheap equipment (heavy-17+ pounds, high rpms-8500 with no speed control), the fact that the concrete is soft/already ground once, and my lack of grinding expertise.

I wonder though if it is as bad as I think, when I look at it in normal light from above it doesn't seem too bad?? I've seen pros elsewhere on here say that 1/32" grooves won't telegraph through with full flake and these are that or less.

I contacted another contractor and he's asking $6/sf to grind and patch and that will defeat the whole cost savings of doing it myself.
Any thoughts? Would renting a walk-behind be a good option perhaps? Renting a different 7" angle grinder/different cup wheel? Maybe try to epoxy patch the grooves? I'm really hoping the wiser people on here can steer me in the right direction, so I don't make this worse.

Thanks,
Nick

 

[Shea]

Hello everyone, and thanks advance for reading this.

I am afraid I may have messed up my garage floor, and could use some advice on what to do before making it any worse.
It's 380 sf, 30 years old, no cracks or large damage. Kit is 4195 epoxy (gray) with 5085 polyaspartic clear, full flake (gray/black small size). Previous homeowner had installed carpeting, and therefore I hired someone ~1 year ago to grind it off as I'd read that adhesive removal could be extremely difficult. I told the contractor I'd be putting in epoxy and he agreed to leave it ready for that.
Unfortunately my life got really hectic, and I wasn't able to get to it until recently. In the meantime my mother-in-law insisted on parking in there a few times, and it got a little dirty. I also noticed that the contractor didn't really patch anything and there were significant areas that needed it. I thought I would patch, then grind the patches off, as well as the few areas where some tire marks/grease seemed to be an issue.
I foolishly attempted to do this with a 4" grinder and a turbo cup wheel. Looked fine as I was working but afterward with a light from the side I saw this.

I realized my error of using the 4" grinder, and went to Harbor Freight and picked up this 7" grinder and cup wheel.
I then tried to use it on a separate area I had applied a vinyl concrete patch to, and noticed the same issue (creating grooves in the surface).

So, at this point, I'm not sure how to proceed. I know better than to try to "learn" with the 7" grinder on those areas I messed up before with the smaller one. I am no expert but I kept it very level and moving in circles the whole time with no added pressure, but it just ate into the surface almost instantly. Based on the videos I watched, and research I did, I expected it to be a pain using the 7" angle grinder, but would just be a matter of taking my time. I'm guessing the problem is related to the cheap equipment (heavy-17+ pounds, high rpms-8500 with no speed control), the fact that the concrete is soft/already ground once, and my lack of grinding expertise.

I wonder though if it is as bad as I think, when I look at it in normal light from above it doesn't seem too bad?? I've seen pros elsewhere on here say that 1/32" grooves won't telegraph through with full flake and these are that or less.

I contacted another contractor and he's asking $6/sf to grind and patch and that will defeat the whole cost savings of doing it myself.
Any thoughts? Would renting a walk-behind be a good option perhaps? Renting a different 7" angle grinder/different cup wheel? Maybe try to epoxy patch the grooves? I'm really hoping the wiser people on here can steer me in the right direction, so I don't make this worse.

Thanks,
Nick

This can be easier than you think to fix, but it will require the cost of more materials. It looks like you purchased your kit from Versatile's website garagecoatings.com. I would recommend purchasing approximately three 1.5-gallon kits of their standard cure 4800 epoxy in the same or similar color as your 4195 base coat color.

100% solids epoxy will self-level and fill in irregularities in the concrete surface without shrinking. So what you see wet is what you get when cured. Mix the first kit and then immediately pour it in ribbons for the first 1/3 of the floor. Then, use a squeegee (they sell them) to lightly pull the epoxy across the surface for that area only and then back roll with a 3/8" roller cover. Rinse and repeat for the next 2 kits. This should fill in most of the kiss marks and irregularities from the grinding. This along with the full flake coverage should take care of the issue.

100% solids epoxy has a shorter pot life than the 4195. Use a helper when applying it. Mix the first kit and pour it on the floor. One person runs the squeegee while the other backrolls. The one who ran the squeegee should begin mixing the second kit just before the first kit is finished up from being back-rolled. Make sure to begin applying the 4195 within the recoat window of the 4800.

 

[nameyers11]

This can be easier than you think to fix, but it will require the cost of more materials. It looks like you purchased your kit from Versatile's website garagecoatings.com. I would recommend purchasing approximately three 1.5-gallon kits of their standard cure 4800 epoxy in the same or similar color as your 4195 base coat color.

100% solids epoxy will self-level and fill in irregularities in the concrete surface without shrinking. So what you see wet is what you get when cured. Mix each kit and then immediately pour it in ribbons for the first 1/3 of the floor. Then, use a squeegee (they sell them) to lightly pull the epoxy across the surface for that area only and then back roll with a 3/8" roller cover. Rinse and repeat for the next 2 kits. This should fill in most of the kiss marks and irregularities from the grinding. This along with the full flake coverage should take care of the issue.

100% solids epoxy has a shorter pot life than the 4195. Use a helper when applying it. Mix the first kit and pour it on the floor. One person runs the squeegee while the other backrolls. The one who ran the squeegee should begin mixing the second kit just before the first kit is finished up from being back-rolled. Make sure to begin applying the 4195 within the recoat window of the 4800.

Thanks very much for the reply Shea. A few follow-up questions for you:

• Is renting a walk-behind grinder to try to remove the kiss marks/irregularities a foolish idea?
• The 4800 TDS says **All concrete shall be primed with 4100 Epoxy Primer before applying 4800. Refer to 4100 install guide for instructions.** Is it okay to disregard this?
• The 4800 TDS says 200 sf/gal, but you think I will need 4.5 gallons for the 380 sf (more than double)... I'm assuming this is to ensure I apply it thick enough to fill the irregularities-will I need to take any special measures when applying it that thick? Do I need to allow for more cure time?
• I forgot to mention that I intended to grind off the epoxy patches, but bailed after seeing the way the grinder dug into the surface so quickly. If they are flush is it enough to just scuff them/degloss as in this picture? Or do I need to do more than that? Maybe sand them with a coarse resin disc? Just concerned about adding more gouges with a grinder.

Thanks again,
Nick

 

[Shea]

Thanks very much for the reply Shea. A few follow-up questions for you:

• Is renting a walk-behind grinder to try to remove the kiss marks/irregularities a foolish idea?
• The 4800 TDS says **All concrete shall be primed with 4100 Epoxy Primer before applying 4800. Refer to 4100 install guide for instructions.** Is it okay to disregard this?
• The 4800 TDS says 200 sf/gal, but you think I will need 4.5 gallons for the 380 sf (more than double)... I'm assuming this is to ensure I apply it thick enough to fill the irregularities-will I need to take any special measures when applying it that thick? Do I need to allow for more cure time?
• I forgot to mention that I intended to grind off the epoxy patches, but bailed after seeing the way the grinder dug into the surface so quickly. If they are flush is it enough to just scuff them/degloss as in this picture? Or do I need to do more than that? Maybe sand them with a coarse resin disc? Just concerned about adding more gouges with a grinder.

Thanks again,
Nick

• Is renting a walk-behind grinder to try to remove the kiss marks/irregularities a foolish idea?
• It's not foolish, but it will require more work and a lot of grinding. Remember, you would need to take the surrounding areas down to the lowest level of the kiss marks to smooth things out. You may create smooth depressions doing that. Applying the epoxy would be easier.
• The 4800 TDS says **All concrete shall be primed with 4100 Epoxy Primer before applying 4800. Refer to 4100 install guide for instructions.** Is it okay to disregard this?
• Many times this is a requirement to avoid bubbles from off-gassing and other cosmetic issues when applying 100% solids direct to epoxy. I would recommend giving them a call to discuss it. Tell them how you are using it and that it will not be an exposed color coat.
• The 4800 TDS says 200 sf/gal, but you think I will need 4.5 gallons for the 380 sf (more than double)... I'm assuming this is to ensure I apply it thick enough to fill the irregularities-will I need to take any special measures when applying it that thick? Do I need to allow for more cure time?
• That is correct about the thickness. Curing is a chemical reaction that takes place and is not a drying time. It remains the same whether it's 10mils thick or 20.
• I forgot to mention that I intended to grind off the epoxy patches, but bailed after seeing the way the grinder dug into the surface so quickly. If they are flush is it enough to just scuff them/degloss as in this picture? Or do I need to do more than that? Maybe sand them with a coarse resin disc? Just concerned about adding more gouges with a grinder.
• It's hard to tell with the pic. You always want to get it as flush as you can, but it does not have to be perfect with a full color flake system. That's the beauty of all those flakes. They do a good job of covering up and camouflaging irregularities. If it was a partial flake or no flake floor, you would need a better job than the pic.

 

[Armorpoxy]

One added note is that a full fleck broadcast will do an excellent job of hiding swirl marks and irregularities from grinding.

 

[nameyers11]

Thanks again Shea, and thanks Armorpoxy.
It turned out, I was able to solve my problem through some good old-fashioned tool abuse. By putting my 7" diamond wheel on my 4.5" grinder, it slowed it down enough to prevent it from digging in. I was able to go over the sections in a couple of hours and get rid of most of the imperfections, without leaving any smooth depressions. The final result looks great IMHO.


I think it was probably a combination of the heavy, fast grinder I had and the concrete being a little on the softer side causing my original problem.

I really appreciate the reassurance about the full-flake helping to hide the imperfections.

I am going to fill the joints now with some play sand and Sikaflex SL. I have read Shea's article on that on his website (thanks again Shea).

Nick

 

[Armorpoxy]

Looks great!

 

[Shea]

Looks fantastic! Glad it worked out.