How do you fix a concrete slab with a cosmetic crack in it? In this video, Matt Risinger, master builder, walks us through how to fix concrete cosmetic cracks. Using a product by Metzger Mcguire called RS-88 semi-rigid polyurea joint filler, the repair system is used with a specialty caulking gun to fill the crack. The gel sets rapidly, and it is made of 100% solids with no VoCs. Apply in a heavy bead on the top of the crack and then come back in around an hour and scrape the excess off with a scraper.Within a couple of hours, 40 linear feet of cracking was repaired," and the results are impressive. The RS-88 might be a little hard to find so a commercial supply house is your best bet.