Prepping control joints

[Bigbrii]

Last year I coated our garage floor with epoxy, and have some coating failures. I cut some corners in the prep work. I have since stripped the old coating off, and ground the entire floor.
I do have a question about the troweled control/expansion joints.

How can I effectively Clean, and Prep them for the new epoxy coating?

So far I have tried grinding them with a 4" diamond grinder - works ok, but really cuts into the edges of the joints, and leaves coating on the bottom of channel. Used a wire brush wheel attachment, - that removes the coating very well, but appears to 'polish' the concrete - looks like all the concrete pores are full. Finally been mostly using a hammer and chisel to Slowly remove old coating piece by piece. These methods remove the previous epoxy coating, BUT not the Source of the failure.
My current thinking is since I have ground the Flat floor surface, I must use an acid etch to etch the curved troweled surface.
Any thoughts or ideas are Very Welcome. Thank You in Advance.

 

[JCQuick]

first welcome to the GJ and 2nd may we ask what was the coating you first used and what are your plans for the replacement product?

 

[WarDamnEagle]

I had mine filled with a mixture of sand and epoxy above prone before the garage was diamond honed down. Then the epoxy, flake, urethane system was put on top of the entire floor.

You can still see where they were but only when the light is just right. 2 years and not a single hint of a crack. Control joints are only needed until the concrete has finished curing.

 

[Bigbrii]

Am I using the correct term - control / expansion joints? They are the ones troweled into the concrete.
This is a GREAT SITE!!! Mor info in one place I found Anywhere - happy to have found it.

 

[WarDamnEagle]

Yes. They are there to ensure that as the concrete cures and shrinks that it "cracks" along those lines. Concrete isn't going to expand or contract in a garage more than a few microns (at most) after it's cured.

Again, I filled every one of them.