THE JOB
The slab floor inside of a manufacturing facility in Hagerstown, Maryland settled. This caused equipment that was installed on the slab to become misaligned, requiring industrial facility floor repair.
A geotechnical investigation revealed voids below the slab due to the settlement of the underlying soil. The affected area was built over approximately 10 feet of fill during construction. Engineering analysis showed that the soil was likely poorly compacted, but had consolidated with time.
THE CHALLENGE
Due to the sensitive electronic equipment within the work area, the repair had to be very clean and dust-free. Though analysis determined that the underlying soils had most likely completed consolidating, the owner’s geotechnical consultant recommended limiting additional weight placed on the fill material.
The repair area was also more than 100 feet from the nearest exterior access. The floor had started to settle before the equipment was installed. It was very important that the slab not be lifted during the void filling process.
THE SOLUTION
Geotechnical polyurethane grouting to fill the voids below the slab floor. Polyurethane grouting is superior to mudjacking in situations like this because it is considerably cleaner, much faster, and allows for immediate reuse.
The material used in polyurethane grouting is much lower weight than mudjacking grout. This reduces the weight applied to the underlying soil. Lower weight materials reduce the chance of resettlement.
A single CJGeo polyurethane grouting crew completed the industrial facility floor repair in less than a day, using CJGrout 20SDB. Due to the extreme sensitivity of the equipment to lifting, a specially-formulated plural component polyurethane grout was selected for undersealing without lifting.
Precision equipment was used to monitor the floor during undersealing. A movement of 0.02 inches was used to determine the completeness of fill. This was confirmed by extensive extrusion of polyurethane through the adjacent saw cut control joints in the floor. Rotary lasers are the most appropriate for monitoring floor elevations during grouting operations. It’s important to ensure that the base station is well outside the zone of influence of grouting.
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