Pressure grouting (also knows as slab-jacking or mud-jacking) is a specialty concrete repair technology which involves injecting grout material into an isolated void space of which neither the configuration nor volume are known. It attempts to lift a sunken concrete slab by pumping a grout through the concrete, effectively pushing it up from below.
The grout may be a cementitious, resinous, or solution chemical mixture. Pressure Grouting has many applications that include void filling, pipe abandonment, concrete slab lifting, and soil stabilization.
Most of the time a slab can be put back to its original position by pumping a mixture of sand, cement, fly ash, and other additives beneath your slab. The process begins by drilling strategically placed holes into the slab. Then using a portable pump and flexible hoses, the holes are filled with the special mixture.