Does epoxy shrink back

[Down Under Bloke]

Does anyone have experience with painting over cracks or gouges with epoxy. If you fill small cracks or gouges in your floor with epoxy, does it shrink back over time (into the crack or gouge) and then become visible again or do they disappear for good.

 

[Floorguy]

Depends on what type of epoxy you use. The thin stuff that they sell in the big box stores will not cover much if any cracks. A 100% solids material will do a much better job especially with a couple of coats. I diamond grind them out and fill with an epoxy filler then grind them level with a 60 grit wheel on my angle grinder. Then coar like normal with the rest of the floor. A flake floor will also help hide them.

 

[Down Under Bloke]

Thanks Floorguy,

I need to add a couple of cement sheets (15mm compressed) to the edge of my concrete slab to build out in a door opening (The bottom of the door is hanging over a big empty). Naturally enough my concreter finished the edge off with a quarter round so I will have a gap to fill. The plan is to glue and dyna bolt the cement sheets and now to epoxy fill the gap as you suggest. I’ll detail and post result when I get to it.

 

[bmwpower]

Depends on what type of epoxy you use. The thin stuff that they sell in the big box stores will not cover much if any cracks. A 100% solids material will do a much better job especially with a couple of coats. I diamond grind them out and fill with an epoxy filler then grind them level with a 60 grit wheel on my angle grinder. Then coar like normal with the rest of the floor. A flake floor will also help hide them.

What's the need to cut out the crack with a diamond wheel?

 

[V-10 Killer]

Thats how we deal with cracks in containment pits at work. Grind out the crack with a diamond wheel, and fill it with caulk, then brush it flat (with a moistened brush, but I don't remember what we moistened it with. laquer thinner I thought) so nobody can rub it out with their boots. If done carefully, you won't even notice it after painting over.

 

[bmwpower]

What's theory behind cutting out the crack, though? Seems like the last thing you'd want to do is make the crack bigger, no?

 

[RickP330]

I think it's because the filler is usually thicker then the width of the crack, so you really can't get the filler in there unless you widen it up.
RP

 

[Floorguy]

Correct, the crack filler is a thick product so in order to insure it gets deep into the crack one grinds it deeper and wider so the product can get in. Once dry, grind it back level with the floor and you will never see it once it is coated. At least that is the theory.

 

[Down Under Bloke]

I need to grind anyway, as acid wash is not suitable for me, I'll let you all know the result.