PRESSURE GROUTING

Pressure Grouting is the art of injecting grout ( either cementitious or chemical ) through an injection nozzle, into a void, cavity or crack.

Although cementitious grouting (sometimes referred to as "Mud Jacking") is more commonly used when a concrete slab has "sunk" due to weak soil conditions, voids in the soil or excessive moisture in the soil. To pressure grout a concrete slab, small holes (1"-2" in diameter) are cored or drilled, in a specific pattern, throughout the slab. Then the grout is injected, under some pressure ( as required by loads ) ranging from just a few pounds per square inch (PSI) to several hundred PSI. Once the voids have been filled, the pressure will start building and the concrete will began to rise. Once the grouting has been completed, the holes are topped off with a non-shrink grout and struck off smooth with the floor surface.

When grouting a concrete slab, in this manner, the contractor will not offer any warranty, as he is, only, lifting the slab and filling the voids as he lifts. The slab is still on the soil that allowed it to settle, to begin with. Should warranties be required, additional grouting would be required. This is called "compaction grouting" and is performed by injecting grout, under higher pressures, through pipe, into the sub-grade below the slab. This process will compact the soil, to some depth, below the slab and prevent future settlement.

Other methods of pressure grouting utilize epoxies and/or urethanes to repair structural cracks in concrete or seal cracks from leaking.