Leveling Existing 45,000 sq. ft. Concrete Slab of Commercial Building in South Orange County, CA.

Challenge

In March of 2011, Saber was contacted to inspect and give recommendations to level an existing concrete slab at a 45,000 sq. ft. commercial building in South Orange County, CA.  This slab had been experiencing settlement due to voids created by settlement of the underlying soils. A previous repair was completed in 2008, utilizing a cementitious grout injection beneath the slab. The soil was then overburdened due to the weight of the grout at 150 lbs. per cubic foot. Saber determined that the existing slab had settled a further 2.75”.  There were two options for repair that were discussed; coring into the existing slab and installing helical piers to a load bearing soil stratum, or injection of polyurethane resin below the concrete slab to fill all voids, raise the concrete slab back to the original elevation while also compacting the underlying soil.

 

Solution

Polyurethane resin was selected as the preferred option, not only from an economic standpoint but because of the fact that the material only weighs 4 lbs. per cu. ft.  Using a two-man crew, a series of 5/8” holes were drilled through the existing slab at 3ʼ-5ʼ increments for placement of injection ports. Approximately 60,800 lbs. of Precision Lift 4.75 Dual Component Structural Polyurethane was injected from a Graco E30 pump into the ports and subsequently under the slab for the required 2.75” of lift. The entire repair process was completed in six weeks and the slab was leveled and secured from further settlement.

Project Summary

Equipment: Graco E30 Reactor

Material: Precision Lift 4.75 Dual Component structural polyurethane resin

Compressive Strength: 100 p.s.i. or 14,000 p.s.f.

Tensile Strength: 100 p.s.i.

Expansion: 15 times

Density: 4.5 pounds per cubic foot