Slab jacking is a concrete repair process used to fill voids below, and lift settled concrete. Slab jacking uses a cementitious slurry, typically silty sand and a small amount of cement. CJGeo started out as Concrete Jack, a residential slab jacking contractor only working in Williamsburg, Virginia. We now use CJGrout geotechnical polyurethanes instead of cement-stabilized soil to stabilize and lift settled concrete. CJGeo’s performs polyurethane grouting for commercial, industrial & infrastructure clients from Maine to Miami to the Mississippi. We do not work on single family homes.
How Slab Jacking Works
Slab jacking is pretty straight forward. The grout used for the process is a mix of sand or crushed limestone, and cement. Compressive strength is usually less than 50psi at 28 days, similar to flowable fill. The water cement ratio of slab jacking grout is very low, to prevent frac outs. The process is the simplest form of low mobility grouting.
Cost of Slab Jacking
Concrete lifting and stabilization with cement-stabilized soil is typically around half the cost of replacement. Time is money, too, and concrete lifting and stabilization is significantly quicker than replacement, with nearly no downtime.
Polyurethane Grouting Alternative
Geotechnical polyurethane grouting has mostly replaced cement-stabilized soil as the preferred grout for concrete lifting & stabilization. Geotechnical polyurethane grouting is significantly cleaner, faster and allows an immediate return to service. For example, in rail grouting applications, intermittent train traffic through the repair area is allowable.
Polyurethane grouts generally have the same or higher strengths than cement-stabilized soil. Slabjacking relies on the mechanical force of the pump pushing up the concrete being lifted. Polyurethane grouting uses the physical expansion of the polyurethane to gently displace the concrete upwards. Because CJGrout is significantly more mobile, lifting with polyurethane grouts tends to significantly reduce the likelihood of cracking or slab deterioration.
Holes for shallow polyurethane grouting (injecting directly below the slab, as opposed to into the underlying soil) are typically 5/8″ diameter. If soil injection is required, larger holes may be required to install the injection tubing into the underlying ground.
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