The hinge slab of a runway at an overpass settled. This caused up to a 1.5″ difference in elevation across the joint between slabs. The slabs had previously been repaired with pressure grouting. The previous runway slab jacking was done using a cement-based grout. The previous slab jacking required drilling 3″ holes on 4′ centers over the entire area. They had to be core drilled due through the 26″ deep slab.
The proposed repair had to work despite previous repair attempts with cement grout. The repair had to be completed in fewer than 48 hours, with the ability for air traffic at any time during the repair with as few as 10 minutes’ notice. The settled slab was nearly twice as thick as the adjacent slab, which was 14″ thick.
CJGeo proposed polyurethane grouting to raise the settled slabs. Polyurethane grouting allows for immediate resumption of traffic and is much more efficient to install than cement-based grout.
Because the previous repair had left hundreds of 3″ core holes through the slab, polyurethane grouting was idea due to its 5/8″ hole diameter. CJGeo proposed a 6-pound foam for this project, which was originally specified for cement-based grout. 6-pound foam provides adequate bearing capacity and has excellent lifting capacity.
Polyurethane grouting can also be performed in the rain without affecting the material. Due to the extremely short runway shutdown period, the speed of execution despite any bad weather was critical.
CJGeo mobilized three polyurethane grouting rigs to the site. The joint was saw cut full depth using a 48″ walk-behind saw prior to lifting. Lifting was done using up to four polyurethane reactors running simultaneously. Drilling was completed using a combination of pneumatic rock drills & electric hammer drills.
The runway slab jacking project was completed in less than the allotted time. CJGeo’s subcontracted to TST for this project. The project also includes restriping and asphalt pavement restoration on the runway shoulders.