THE JOB
The floor of a 105′ diameter grain bin settled. The floor had a bin sweep installed, that was mounted on the top of the unloading tunnel, which ran down the center of the structure. Where the slab floor butted up to the tunnel walls, the floor had settled 2″ on one half, and 3.5″ on the other half. This caused issues with operating the bin sweep because it was designed for a smooth, level floor.
The owner’s alternative was to remove the entire floor and pour a new floor. This would have been incredibly expensive and taken a very long time. The only access into the bin was two 2′ wide by 4′ tall doors, located 5′ above exterior finish grade, and 2′ above the bin floor elevation.
THE CHALLENGE
Due to the nature of the commodity business, mobilization and completion of the grain bin floor repair had to be fast. Additionally, the repair had to return the floor to its original profile, along with the turned-down ventilation trenches in the floor. The extensive turned-down ventilation troughs made this floor very susceptible to cracking. The floor was 6″ thick but then went to 24″ thick at the ventilation troughs. Slabs with non-uniform thickness require extreme care and attention to avoid differential lifting.
The design loads for the floor are approximately 3500psf. So, the material used for lifting the floor had to be relatively high strength.
THE SOLUTION
CJGeo proposed polyurethane grouting for filling the voids below the floor and lifting them back into place. The minimum bearing capacity of the proposed materials was 5500PSF, ensuring adequate bearing capacity even under full load.
CJGeo mobilized two polyurethane grouting crews to the site. The concrete lifting work was completed over a period of two days. CJGeo placed more than 7,000 pounds of polyurethane grout using three reactors running simultaneously. CJGrout 28FDL is optimal for differential settlement correction, and thus the primary grout. Secondary grouting using CJGrout 20SDB is optimized for undersealing, so chased any nominal voids left by the relatively low mobility CJGrout 28FDL.
Multiple reactors (pumps) helped to ensure thorough lifting of the slab and the ventilation troughs. The crews that completed this job have collectively performed millions of pounds of polyurethane grouting, ensuring the successful completion of this grain bin floor repair job.
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