Concrete raising is a broad term for raising or filling under settled concrete, and generally refers to pumping a cementitious grout below concrete. We use different processes for concrete raising:
Polyurethane grouting uses high density geotechnical polyurethane injection to fill voids below slabs and lift settled slabs by injecting expanding foams under slabs. Polyurethane grouting is by far the cleanest, fastest, and longest lasting concrete raising repair method.
Mud jacking is what people are generally referring to when they say ‘concrete raising’ because it was the first concrete raising process invented. Our residential service sister company, Concrete Jack, started out as a mud jacking contractor.
Slab jacking is just another name for mud jacking.
History of Concrete Raising
Concrete raising, in the form of mud jacking, which is also called slab jacking, was started in the 1930s in Iowa to correct settlement and frost heave of roadway slabs and curb & gutter. The earliest pumps, like the one in this photo, were somewhat primitive. Today’s mud jacking pumps are mobile, powerful and hydraulically powered. Concrete Jack’s pumps are capable of pumping pressures up to 500 psi, and depending on the grout mix can pump up to 100 feet.
The trucks used for mud jacking have also evolved a lot. Concrete Jack’s original trucks required shoveling dry grout mix into a mixer and adding water and Portland cement manually. Now, we run automatic trucks which batch the mud jacking material, Portland cement and water in a horizontal hydraulic mixer, no shoveling required. This makes Concrete Jack’s operation safe and reliable, and enables us to mix and place up to 10 cubic yards an hour of material with each truck.
Polyurethane grouting was developed in Europe in the 1970s as an alternative to mud jacking. The principal of polyurethane grouting is effectively the same as mud jacking–injecting material below concrete can be used to push the concrete up. Polyurethane grouting differs from mud jacking in that the expansion of the polyurethane foam is what generates lift, as opposed to the mechanical force of the pump.
We stock and routinely place more than 10 different polyurethane grouts, which allows us to use the process to raise small, lightweight slabs such as sidewalks to very heavy structures such as railroad crossings and foundations. There are also foams specifically designed to fill under structures without causing lift (called undersealing or void filling).