Terrazzo is a floor surface consisting of decorative stone chips, commonly marble, suspended in a concrete or epoxy mix. Polished and sealed terrazzo creates a durable surface that's full of colors, each floor a unique creation. Though the epoxy or concrete makes the floor difficult to damage, damage does occasionally occur. This damage is repairable, using a patch created of the same decorative stone mixed with an epoxy resin colored to match the floor surface. Once it's in place, you can finish the patch so that its indistinguishable from the original surface.
Remove any sealer over the damaged terrazzo, using a commercial floor-sealant remover. Spread the remover over the damaged area with a squeegee, then wait for the manufacturer-recommended length of time for the remover to dissolve the finish. Remove the stripper with a damp mop, then rinse the floor with clean water to remove any stripper residue.
Mop the damaged floor with a pH-neutral cleanser to remove any dirt or debris. Rinse with clean water, and pat the floor dry with a clean cloth.
Square off the damaged area, using a cold chisel and hammer. Chip along the sides and bottom of the crack or hole to create near-vertical walls that slope, so that you slightly undercut the bottom of the damaged section from the top. This provides a ledge for the patch, to prevent it from popping out. Clean out the area with a nylon brush to remove residue.
Mix a batch of epoxy resin with a color-matching agent to match the color of the terrazzo flooring.
Fill the damaged area with marble chips matching those used in the surrounding terrazzo.
Pour the resin over the chips, using the putty knife to pack the crack or hole full. Level the patch with the surface of the floor, using the putty knife edge. Wait for the resin to dry completely.
Grind the patch even with the surrounding terrazzo using an angle grinder with a very fine diamond grit cup wheel. Switch to a 50-grit resin polishing pad, and smooth the patch out, blending the edge of the resin with the edge of the undamaged Terrazzo floor.
Cover the patched area with a brushed-on sealer to protect it from wear and tear. Allow the sealer to dry before using the floor.