It is a process where two polyurethane liquid components are mixed and injected below the concrete area being repaired. The two liquids react with each other, expand and harden. The polyurethane is injected as a liquid and in a short amount of time expands and hardens to fill any voids and lift the concrete. There is little or no disruption to the surrounding area and minimal environmental impact. In certain applications, polylifting is a preferred solution to lift concrete.