how to repair large, uneven crack in concrete floor

Question

I have a really long (about 20') uneven crack in my cement garage floor. Not only is it jagged, but the sides of the crack range from flat to about 1/2" high. I want to level the sides of the crack, seal it, and end up with a flat floor. I'm not sure what the best way to do this is. I'm thinking about either grinding or chiseling down the high side, then applying CrackFix, then applying some sort of topcoat to make it smooth. Anyone have any better ideas?

I'm not going to put a floor over it, I just want it to look good again. I picked CrackFix because it looks like it will seal and level at least the crack, but once I break up the high side I still need to level and smooth the whole area.

Answer 1

The proper way to do it would be to break it up and pour again. You might be able to get away with a self leveling compound that you pour over the floor then let it set.

I've used these before installing tile on concrete. I can't imagine what it would look like as a finish.

Answer 2

When I come up against this issue when laying floating floors I grind down the higher area. I use my 5" angle grinder and a grinder like this: turbo grinding cup for granite

You will generate ALOT of concrete dust. I sometimes cut out a half circle in a 5 gal bucket so I can set it over the angle grinder about half way up the handle. In the other side I cut a hole to put my shop vac into. Dust is reduced probably 95% this way. You have to work by feel and stopping to check your work occasionally but for the size of crack you describe 1/2 hour should take care of it. When you have a level surface you can finish it any way you wish.

Answer 3

It sounds like your ground is settling (hence the high spots). Crack filler will only be a temporary fix.

the best solution(and cheapest) is to break up the area around the crack and re-lay the slab section.

it would be better to chisel away the damaged sections (as opposed to cutting) since the ragged join will bond better and have better crack resistance.

Mix some cement/concrete mix and lay into the area. then follow up with a screed mix whereby you use a float to smooth the finish. For this, sprinkle some water over the drying screed and "float" using a screeding float

Answer 4

My solution was to grind the high side down with a diamond wheel on an angle grinder until the surface was reasonably level, apply an epoxy filler, and cover the floor with an epoxy chip floor that will cover any further imperfections.