Quarry tiles are an unglazed, red clay ceramic tile. They are extremely dense and durable, which makes them popular in floor tile applications. While quarry tiles are extremely durable, shifting foundations or substrates can lead to a cracked tile. When this happens, the crack becomes a structural weakness in the floor as well as an eyesore. You should repair these cracks as soon as possible. You can use epoxy or epoxy cement to fill the crack and give the tile strength.
Mix the two-part epoxy mixture on a scrap of cardboard. Both epoxy and epoxy cement require combining two chemicals to form an extremely durable glue. The two parts come in separate containers; squeeze equal amounts next to one another, and stir with a toothpick to combine.
Scoop up some combined epoxy or epoxy cement with the toothpick, and apply it directly to the crack. Try to get as much epoxy into the crack as possible, filling the crack rather than laying the epoxy on top of it. Continue to apply epoxy to the crack until it is level with the top of the tile. Wipe away any excess epoxy with a lint-free cloth. Allow the repair to dry for 24 hours.
Cover the repair if desired with an acrylic paint that matches the red colour of the quarry tile. Use a small paintbrush and just enough paint to blend the crack into the rest of the tile. Let the paint dry completely.
Seal the paint to keep it from staining by painting urethane sealer on top of the tile. Use a foam paintbrush for even coverage, and take care to apply the sealer to all areas of the paint and surrounding tile. Let the sealer dry overnight.