Concrete Voids- Slabjack Geotechnical


Voids under concrete eventually lead to cracking and/or settling concrete. Voids are created when concrete is partially supported by base soils or through the use of anchors or rebar to foundation walls or through the use of Sonotubes. As the soil settles or is carried away by other means a gap opens up between the soil and the bottom of the concrete slab resulting in a loss of support.

Un-compacted fill dirt, erosion, burrowing rodents, decaying organic material even a loss of moisture in the soil can create voids. Once there, voids are difficult to fill. Smaller slabs such as walks can be packed with gravel or sand to fill voids but this is not practical for larger slabs such as driveways or patios. These need a method that supports but doesn’t lift the slab. Using an expansive polymer is the ideal material for void filling for several reasons such as;

Polyurethane can travel several feet in every direction to fill voids, fissures and holes. It has the ability to consolidate organic material, sand and loose rock. If properly monitored Polymer injection can provide support without excessively lifting or stressing the slab which causes fractures.

The question with new construction is what should I do? Settling of soil in new construction can go on as long as 10 years so the question becomes do you live with it and replace your broken up concrete at some later time or do you try and preserve it knowing that you may have someone out 2, 3 or 4 times in the next decade to shore up what should’ve been taken care of during initial construction. Immediate replacement of settled concrete or concrete with voids is not a good choice as settling is not yet complete.

If you see a void opening up under your concrete slabs give the concrete raising and leveling professionals a call we will get you taken care of.


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