Polyurethane is also known as compaction grouting, concrete raising, concrete lifting and slab jacking. This process is almost exactly what it sounds like. It is a way to pump in, under pressure, large amounts of concrete to fill voids and lift concrete back to grade.
Polyurethane is an inexpensive way to repair areas of concrete that have settled. Sidewalks, driveways, patios, basement floors and foundation walls are all good candidates for this type of process. The process is simple: A hole is drilled in the concrete slab, and then a thin mixture of sand and cement, also known as grout are pumped under the area. This fills the voids beneath the area but if enough is pumped in, will raise the area.
Polyurethane is also in some cases a good repair for areas with poor soil conditions. The same type of mixture is pumped into the soil, under pressure, and the pressure pushes the soil; compacting it together. The mixture will then fill the void just created by pushing the soil together, thus densifying the area. When Polyurethane is used to lift the perimeter of a home, the process is a little more labor intense. The soil around the perimeter is removed; the foundation is raised, usually with bottle jacks. A new or higher footer is poured and when everything dries, the foundation is dropped back down on the new pour, usually at a higher elevation to level the home back to its original grade.