Voids under concrete can be scary to look at and leave you with a sick feeling in your stomach as you decide how if it is even possible to get the problem fixed without replacing your concrete. Concrete repair is a wide range of different things but void filling is very important because you can save a good slab of concrete if you are proactive in noticing it and taking care of the problem as it arises. several 5/8″ holes are drilled depending on the size of the concrete slab and polyurethane foam is injected to fill the void and support the concrete slab. it is important not to add too much polyurethane foam or else you will start lifting the concrete slab. when this process is complete the concrete is supported and can spend a considerable amount of less time fixing your concrete issue without having to remove the concrete and all the of the things that go along with that. Void filling can take as little as an hour depending on size and up to a day, removing and replacing concrete usually takes 4 days to a week by the time its all said and done.