Advice on grinding concrete garage floor for epoxy paint

[Onoff]

I decided not to apply an epoxy (or comparable) coating to the concrete floor in our new garage. I wasn't interested in a pretty, man-cave-style floor, bur just wanted to protect the concrete from salt, oil, grease, etc., and also prevent or reduce dusting. Instead of a coating, I opted for a two-step penetrating concrete treatment.

The first step was the application of a penetrating lithium silicate concrete densifier and hardener/strengthener. The concrete had cured for over a month and was clean and very dry before applying it. This is what I used (I would think that this or similar products should be available in the UK):

https://assets.ctfassets.net/muyees5bu8n0/7A6CiwnF0WYcwk1uB7mDxf/fb8aa01ffb4ab4083f529d0efe88a131/4500_TDS_LEED.pdf

After that was thoroughly dry, I applied a penetrating hydrophobic and oleophobic sealer that repels water and oil and protects against salt damage:

https://assets.ctfassets.net/muyees...c28b23765eba9a743a76285ffa7/8510_TDS_v.5_.pdf

Note: This sealer might prevent some types of adhesive, caulk, or coatings from sticking well to the concrete. I put a few drops of epoxy on the sealed concrete to see what happens, and the cured epoxy popped off easily with a putty knife. I figured that meant that it's doing its job. Neither of these treatments changed the appearance of the concrete very much. These were fairly expensive products, but I think they should be worth it in the long run.

I've only done half of our garage floor so far. I need to move a bunch of stuff off of the other half of the floor to do that half, which I plan to do before winter.

Wow! I take it you can't get SBR there?

 

[Onoff]

unibond if watered down soaks right in and does not go slimy when wet, put it on neat and it does as you say

All I know is when I did my first house, not knowing any better, I used to buy the "black" Unibond from Wickes as opposed to to the one in the red 5L container. The black was specifically waterproof. I put it in everything inside and out as a 5:1 mix with water. Concrete, mortar, render even plaster.

I still own the house and 34 years later everything I did internally and externally is still rock solid.

Too solid tbh in some places! 1863 house so I should have done everything with breathable, lime based products at least inside the house and on external render.

I'm veering off here but just to make the point ordinary PVA will re-liquify. It's an absolute no no if you're going to tile over it in say a bathroom. Then it's proper tile primer or SBR.

 

[Blue Chips]

Wow! I take it you can't get SBR there?

I was actually considering using one of the Sika SBR products as a sealer.

However, after doing some research, for my own purposes I preferred the characteristics of Siloxa-Tek 8510, as it's a deep-penetrating sealer that doesn't leave a film on the surface that could eventually wear off, and it leaves the concrete's appearance virtually unchanged. Also, its oleophobic characteristics make it great for use in my garage/shop, where it will be getting a variety of oils, grease, etc., spilled on it. Oil and grease wipe off easily, and it protects against water and salt (and they use a lot of salt on the roads here in the winter). It's also recommended for application after first applying Lithi-Tek 4500 lithium silicate penetrating densifier and hardener.

Both of these products allow the concrete to breathe, while the sealer prevents moisture incursion.

Another approach if you like using SBR would be to first apply a lithium-silicate densifier/hardener to strengthen the concrete, and then apply the SBR sealer.

 

[Pete.]

Grinding the fat off your concrete floor is probably the best thing you can do before painting unless your floor has been powerfloated or tapmped without raising too much water and fines. That means pretty much any amateur-laid floor as most people (including yours truly) tend to over-float a pour and turn the surface to flour.

I'm doing my own garage floor this winter. It wasn't laid by me, it was here when we bought the place but it's a particularly bad surface which needs sorting out. it was painted heavily with floor paint but that just flakes off in huge flakes with a thin layer of cement on the back.

i did my 20 square meters slab in the last workshop in a couple of hours witha 9" grinder and diamond cupwheel. You van buy or make a dust shroud, hook it to a dust vac and it;ll contain most of the airborne dust.

 

[Onoff]

Another approach if you like using SBR would be to first apply a lithium-silicate densifier/hardener to strengthen the concrete, and then apply the SBR sealer.

I take it you're not mechanically removing the laitance then?

 

[Blue Chips]

I take it you're not mechanically removing the laitance then?

There was little laitance to begin with, as the concrete was mixed quite stiff and worked minimally and efficiently by a pair of seasoned pros who were a joy to watch, so there was no overworking or overly wet mix, and not much in the way of fines was brought up to the surface.

However, I still did some minimally-invasive mechanical laitance removal. Here's how I prepped and treated the floor:

I have a 4,000 psi, 4 gpm pressure washer, and I pressure washed the surface of the floor after it cured for about a month, and then let it dry for days, after which even a stiff brooming would not raise any dust that I could see.

Then I applied the penetrating Litho-Tek 4500 densifier/hardener, which is formulated to reduce dusting as well as strengthening the concrete by reacting with calcium hydroxide and binding particles together and filling cracks and pores. I kept wetting the floor with it until it would not absorb more, and then squeegeed off any remaining liquid.

After the densifier dried for a week or so, I applied the penetrating Siloxa-Tek 8510 sealer in a similar way, keeping the floor wet with the sealer until it would not absorb more, and then squeegeed it, leaving no surface film.

I was not applying a coating to the surface, since both of the treatments were penetrating treatments that did not leave a surface film, so if there was any residual laitance, it would be less of an issue (no separation/delamination of a coating).

NOTE: If I had been planning to apply an epoxy or other coating to the floor, I would NOT have applied the Siloxa-Tek 8510 sealer, but instead would have applied something else that would work as an appropriate primer or bonding coat.

 

[visor_down]

Thanks all, some really good points and helpful info.
I'd like to apply a colour coat as it has been half painted in the past (not by me) and this is worn away, by looks of it it is that standard burgundy floor paint you get from DIY stores. It looks a mess and I now have the once in it's lifetime chance to paint it now before I fill it up.

I have linked the product details below and it does say it should be textured mechanically rather than jist removing latience. The supplier recommended 2 coats of their DPM product (homebuyer survey suggested the floor doesn't have a dpm). I was all set to go until I found out about the silica risks.
The hire of an extractor is a good point I'll look into.
@Agroshield