Garage Epoxy Prep - Water beading issue

[su_hyd]

I have prepared my two car garage floor by renting Diamabrush concrete grinder (wet grinding) from homedepot and there after pressure washed the entire garage. After the floor is dry, there are around 4 spots were I noticed concrete is darker than rest of the area and ended up doing water bead test. To my surprise water did bead on the darker spots and took significantly more time to soak compared to rest of the garage.

I will be using Quikrete epoxy kits and have not etched the surface using their prep solution.

Wondering what I can do to pass water bead test without having to regrind the surface using concrete grinder? Any help will be greatly appreciated.

 

[Shea]

They look like spots where oil sat for a long time. Pressure washing doesn't always do a good job of removing oil and acid etching doesn't remove oil either. I would treat the spots with a good degreaser or you could try some Pour-n-Restore. People have had luck with that.

For the degreaser, mix a strong batch, pour it on the spots then let it sit for 15 or 20 minutes. Don't let it dry out. Keep it wet. After it sits, follow up with a good scrubbing. Rinse it lightly. Just enough to get the residue off the surface. Next, pour some kitty litter on the spots making sure to grind it in with your shoe to form a fine powder. A brick works well also. The kitty litter is a natural poultice that will help draw the oil out of the concrete. After you do that, apply some more kitty litter on top to insure that it will not all get wet and quit absorbing. Let it sit for at least 24 hours then sweep up and do your water test again.

Keep in mind that even on concrete without oil, water absorbs at different rates due to the density in concrete and other factors. If the water absorbs in less than a couple of minutes you should be OK.

 

[Edger]

I would add to the above by saying you can do the kitty litter first and add some solvent to it like thinners. As a degreaser I like detergents or alkaline degreasers over solvent degreasers because the wash off better with less contamination of the clean concrete.

There is no need to acid etch or to grind again, just work on the oil spots.

If the oil spots are relatively new you should epoxy coat soon after cleaning, before they become dark again. That might be 8hrs for very wet oil spots in hot temperatures to a couple of weeks for old oil spots in cool weather.

 

[su_hyd]

Thanks you all for the quick feedback...will try Pour-N-Restore and see how it goes.

 

[retfr8flyr]

One tip about PNR, put on a fairly thin coat or it will take forever to dry. I recommend a thin coat and hard scrubbing, let it dry and repeat. That's what I did on my floor. I put it on to thick the first time and ended scrapping some of it off.

 

[Darenlhr]

Take a weed burner and burn it off it really works just don't sit in one spot too long

 

[su_hyd]

It was too late....I used "Valspar Oil Stain Remover" as PNR is not available in near by stores and the product is very similar to PNR. Ended up putting thick coat and it didn't dry even after 9 hrs. I cleaned the area with water and let it dry to see if the stain went away...sure it did. Two things I learned from using this product....(1) Shake the can really.....really....really well before application (2) Apply thin coat using...may be using brush so that it dries in the time mentioned in the specs.

One tip about PNR, put on a fairly thin coat or it will take forever to dry. I recommend a thin coat and hard scrubbing, let it dry and repeat. That's what I did on my floor. I put it on to thick the first time and ended scrapping some of it off.