Concrete pin holes - prep for epoxy resin

[dangti6]

I am prepping my garage floor with a diamond grinder for a epoxy resin finish and having ground some areas I have found some bug holes / pin holes in the concrete caused by air bubbles or whatnot.

I don’t want leave them and epoxy over the top as it will likely cause air bubbles in the finish. 

 

I understand when going for a polished concrete floor, a grout is added which fills such holes. I’m struggling to find such a product to buy. Epoxy mortars are probably to thick for small (single figure mm) holes so I’m wondering whether a cement and water slurry spread over may fill these in before a final pass with the diamond grinder or if anyone has any recommendations for a slurry/grout product. 

Thanks 

[nod]

If you mix SBR 4-1 and add a few handfuls of dry cement Mix it in and pour it on the floor Use a soft sweeping brush to spread it out 

[dangti6]

Thanks @nod is that 4 parts SBR to 1 part water?

[nod]

2 hours ago, dangti6 said:

Thanks @nod is that 4 parts SBR to 1 part water?

4 water 1 SBR 

[dangti6]

Thanks - that could have got messy!

[saveasteading]

Depends on the size and extent of the holes I would say.

 

I would be inclined to make a stiff mix of mortar or just cement with SBR/Unibond in it as suggested above.

But then I suggest it is a hands and knees job with a filing trowel.

That way the stuff is pressed into the holes, and you clean the surface off as you go.

 

For bigger holes, for example when lignite is in the concrete, I have used epoxy floor repair.

That could be an option for you, but if the holes are miniscule you won't want the kind with sand mixed in.

[dangti6]

21 minutes ago, saveasteading said:

Depends on the size and extent of the holes I would say.

 

I would be inclined to make a stiff mix of mortar or just cement with SBR/Unibond in it as suggested above.

But then I suggest it is a hands and knees job with a filing trowel.

That way the stuff is pressed into the holes, and you clean the surface off as you go.

 

For bigger holes, for example when lignite is in the concrete, I have used epoxy floor repair.

That could be an option for you, but if the holes are miniscule you won't want the kind with sand mixed in.

 

Hi. There's a mix really but nothing massive. I have only ground a small area at the moment where I have uncovered some small holes and a couple of larger ones. No idea what I'll find when I do the whole area (40sqm).

 

Photos speak a thousand words as they say. Here's the slab where I have ground it and the area behind that's yet to have the laitance etc removed. 

 

 

These are the small pin holes.

 

 

 

These are the two largest holes. Vernier shows the depth for reference. 

 

 

 

In an old 30+ year old concrete slab which I have butted up to, there are some deeper or wider dents from cat paws etc which need filling.

 

 

Where the two slabs meet there is a join, naturally. 

 

 

No doubt the paint will crack also so I am contemplating running a grinder down this line between old and new and filling that whilst I am at it.

 

Resincoat, who I am buying the epoxy from sell an epoxy mortar, but it does look quite thick for the smaller areas and sandy as you say and is probably more suited for pot holes. Ideally I want to use a polyfilla paste type material which I can press in with a putty knife. Do you have any recommendations on a brand to go for? This sounds ideal but out of bloody stock: Clicky

 

Someone mentioned car body filler. That's on my reserve list. 

 

 

[saveasteading]

8 hours ago, dangti6 said:

a brand to go for

I bought the standard stuff in a plastic pot from, I think, Travis Perkins, In it there were more containers:  a bag of gritty sand, a tin of resin and a tube of hardener.

Once mixed (which needed a mixer, I used a bent wire on a hand drill)) there is a limited time.

I ended up doing this myself with a groundworker, as I would have been there saying which holes to do or leave. Maybe 100 holes?

This was an industrial concrete floor with lignite that had floated to the top (small print says so no guarantee against lignite in the mix)

 

The holes were between 5mm and 25mm, and I think only epoxy would have stayed in there with forklifts and trolleys.

 

For domestic / gentle garage loading perhaps a ready-mixed product will suffice, but it needs to stick hard..

 

I think that the pinholes will fill with your paint, especially if more than one coat, but will you notice?

 

The crack at the joint is commendably small. Very difficult to patch this, but it is a tiny shrinkage crack and shouldn't move again. You could scratch a V out of it and fill. Or put a skim over it like in plasterboard skimming.

I think a preliminary, extra coat of your floor paint along the joint may be the best cover.

[jack]

18 hours ago, dangti6 said:

Do you have any recommendations on a brand to go for?

 

This is all very familiar. I did this last year to my 5 year old, heavily scabbed garage floor (we had unexpected rains and frost the night after our slab floor, and we ended up with bad spalling). I ground back all the weak concrete over a weekend and laid an epoxy top. It's held up pretty well, although it will scratch if you drag something sharp and/or heavy along it. Very easy to keep clean though.

 

You're right about the epoxy repair stuff being too granular. I had a couple of deep holes to fill, and it was fine for that, but no way would you get it into those smaller stone-holes.

 

I got everything I used from Promain. They have a wide variety of products from lots of different manufacturers, and their technical department was very helpful and responsive by email and phone. 

[dangti6]

On 06/10/2021 at 00:26, saveasteading said:

I bought the standard stuff in a plastic pot from, I think, Travis Perkins, In it there were more containers:  a bag of gritty sand, a tin of resin and a tube of hardener.

Once mixed (which needed a mixer, I used a bent wire on a hand drill)) there is a limited time.

I ended up doing this myself with a groundworker, as I would have been there saying which holes to do or leave. Maybe 100 holes?

This was an industrial concrete floor with lignite that had floated to the top (small print says so no guarantee against lignite in the mix)

 

The holes were between 5mm and 25mm, and I think only epoxy would have stayed in there with forklifts and trolleys.

 

For domestic / gentle garage loading perhaps a ready-mixed product will suffice, but it needs to stick hard..

 

I think that the pinholes will fill with your paint, especially if more than one coat, but will you notice?

 

The crack at the joint is commendably small. Very difficult to patch this, but it is a tiny shrinkage crack and shouldn't move again. You could scratch a V out of it and fill. Or put a skim over it like in plasterboard skimming.

I think a preliminary, extra coat of your floor paint along the joint may be the best cover.

 

I have bought a small tub of 2 part body filler which states is suitable for concrete, so I will try it out and see how hard it is. You can drill it, and I'm sure with the coating on top it will be fine for a domestic setting. 

I am looking at doing a primer coat and two top coats of epoxy so I have time for a plan B if the primer doesn't play ball with the holes I guess.

 

These holes below are an example I found online where moisture has caused issues in a coating, but the same bubbling appearance was my fear due to air but we'll see what happens.

 

 

 

On 06/10/2021 at 09:44, jack said:

 

This is all very familiar. I did this last year to my 5 year old, heavily scabbed garage floor (we had unexpected rains and frost the night after our slab floor, and we ended up with bad spalling). I ground back all the weak concrete over a weekend and laid an epoxy top. It's held up pretty well, although it will scratch if you drag something sharp and/or heavy along it. Very easy to keep clean though.

 

You're right about the epoxy repair stuff being too granular. I had a couple of deep holes to fill, and it was fine for that, but no way would you get it into those smaller stone-holes.

 

I got everything I used from Promain. They have a wide variety of products from lots of different manufacturers, and their technical department was very helpful and responsive by email and phone. 

 

Thanks for the heads up with Promain, they have been very helpful in suggesting a product. One thing I need to go back to them about is non slip additives as that wasn't mentioned in my quote. Did you add any? I am in two minds about it and unsure realistically how slippery it would be with wet feet.

[saveasteading]

4 minutes ago, dangti6 said:

the same bubbling appearance was my fear due to air

As long as you fill the holes with filler or paint, there wont be any air.

 

6 minutes ago, dangti6 said:

moisture has caused issues in a coating

This isn't the same situation as yours, as your floor is very dry.

[jack]

54 minutes ago, dangti6 said:

Thanks for the heads up with Promain, they have been very helpful in suggesting a product. One thing I need to go back to them about is non slip additives as that wasn't mentioned in my quote. Did you add any? I am in two minds about it and unsure realistically how slippery it would be with wet feet.

 

I considered non-slip additives, but didn't go for them in the end. I'm pleased I didn't as i suspect it would have been messier, and harder to get a neat finish. I also didn't want to risk it being difficult to roll things around.

 

It's a fairly smooth finish, but I've never had any issues with it being slippery when wet. I'm pretty careful how I move around if there's any moisture though. It's mainly an issue near the garage door. The floor can get damp if it's raining and I have the door open.

One thing to keep in mind with epoxies is that they aren't all UV stable. Promain did warn me about the potential for colour change where the epoxy gets exposed to sun, especially where the concrete extends outside the door, and certainly there's been a slight change in colour after about 18 months. It's really only something you notice when the door is open and both colours are lined up beside each other. 

[dangti6]

I have now done a couple of passes with a diamond grinder and pinholes may be the least of my worries. Although the top layer of laitance came off easily I have found that there is pitting across the whole area which is no doubt caused by the wet mix and probably goes down deep enough to the point I can’t feasibly continue to grind to find a uniform layer without loosing a lot of depth.

 

 

 

 

 

I’m in two minds whether a good quality 2 pack epoxy coating will cover over these larger areas without lifting. The optimist in me hopes a couple of layers of high build resin (first coat thinned to penetrate) will keep it all together providing I don’t hit these with pointed loads. Am I dreaming? It’s a domestic garage opposed to an industrial environment remember.

[Onoff]

2 pack epoxy will be fine imo but vacuum the floor really well first to get all the loose and dust off. 

[saveasteading]

Poss a damp cloth or mop after the vacuuming, depending on the suction power. The polished stones should show up nicely then for a moment.

[dangti6]

I’m going to rinse it all off as I have to do the perimeter later with a 4” disc on an angle grinder to get up tight to the walls. The dust that was created doing this dry without a hepa vac was mental and I can’t bare to be on my knees doing the edges so I’ll wet vac up the slurry and hose the room out. 
 

My anthracite coloured garage door covered in dust after having the door up.?

 

 

(I was masked up)

[dangti6]

Did the epoxy this week. First coat was a primer/sealer which penetrated nicely in to the concrete - have to work fast.

 

Top coat of 2 part epoxy went on lovely. Some holes filled but what I found was there were a lot more holes than I had realised. Guess the light grey gloss against the holes highlights them a lot more too.

 

 

 

 

In two minds whether to buy more and add another coat - think even if I did, it wouldn’t fill all of them unless I made it really thin which I’m reluctant to do as the top coat should really be a higher build to be as robust as possible.

 

Tempted to just leave it. Don’t intend to get the area wet or work out there without spill trays etc anyway.