Concrete Slab Repairs, Concrete Crack Repair or Slab jacking is used as a specialty concrete repair or slab lifting technology. The basis is that slabjacking lifts concrete slabs that have sunk or subsided by pumping a specially formulated grout under the surface of the concrete which pushes it up from below and levels it.
Concrete slabs can be susceptible to settlement from a wide variety of factors in Australia the most common being ground movement from severe droughts ‘earth shrinkage’ to flooding, ‘wash out of sub-soils’, Concrete Slabs built upon filled in land or sandy soils can excessively settle as well. The result of sunken slabs and foundations in buildings, roads, bridges, houses, driveway or any concrete slab can be raised and releveled to its original height using a pressure injection of polyurethane resin “Slab Jacking with Polyurethane”
Polyurethane grout levelling utilizes closed cell polymer expanding foam in an injection process. A two-part polymer (example, component A and component B) is injected through a hole less than 13mm in diameter. Although the material is injected at a higher psi rate than traditional cementitious grouts, the pressure is not what causes the lifting. The expansion of the air bubbles in the injected material below the slab surface performs the actual lifting action.
Material injected below a slab to be lifted will first find weak soils, expanding into them to consolidate and cause sub-soils to become denser and fill any voids below the slab. One inherent property of expanding foams is that they will follow the path of least resistance, expanding in all directions. Another inherent property includes reaching a hydro-insensitive or hydrophobic state when cured with 100% cure times in as little as 5 minutes.
Closed cell polymer foams offer benefits, which go beyond the goal of levelling hard surfaces. They are not subject to erosion once in place. Their fast cure time allows for immediate use when application is complete. Their lightweight, 1.3 to 3.6kg. per cubic ft. vs. 45 to 55 kg. per cubic ft. for cementitious grout will not cause further settlement. Foams will retain their cured shape and volume indefinitely reducing the possibility of new voids forming below grade unless acted upon by some outside cause. Some closed cell polymer foams have baseline lifting capabilities of 2,700 kg per sq. ft. and levelling procedures have been performed in which loads as high as 125 tons have been lifted and stabilized in a surface area of less than 900 sq. ft