There are many ways to repair cracks when doing epoxy coatings, sometimes you need to repair that crack fast. This was what I was facing as I was installing a metallic epoxy floor in our own showroom. With limited working time I needed a fast setting, injectable epoxy. I grabbed one off the shelf and a little over an hour later I was applying my first coat of epoxy.
I wasted no time worrying about mixing ratios or measuring out material. Popping off the cap I put on the mixing nozzle and started injecting into the crack. Our epoxy has a consistency of water so it easily flows into a tight crack, like a hairline. It cures to a medium gray and when I say this is a fast set crack repair, I mean FAST SET! The room temperature was around 75F and within several minutes the epoxy began stiffening and curing. I gave it 1 hour and then sanded it down with 120 grit sand paper on an orbital sander. It was rock hard and I was able to able get the primer coat of epoxy down less than 2 hours after I began my floor patching, which saved me an entire day.