We drill small, dime sized, holes through the concrete and inject specially formulated polyurethane foam under the slab. This liquid foam fills all the voids under the slab and as it expands it lifts the slab and further compacts the ground below it to minimize the probability of future settling. Jacking concrete with polyurethane is better than the traditional mudjacking process for two primary reasons. First, the foam used weighs about 2 pounds per cubic foot, whereas the slurry used in mud jacking weighs about 100 pounds per cubic foot.