Bridge Approach Slab Lifting
Various approach and departure slabs on a roadway settled. The affected slabs included up two four travel lanes, and two full width shoulders, depending on location. The repairs were warranty work prior to turning over the roadway to the DOT and coming off bond. Slab settlement varied from 2 inches to 6 inches.
- Speed. The roadway needed to be completely open during the day, and at least one lane at night
- Cost. Because this was a warranty repair, the contractor wanted to minimize cost of the bridge approach slab lifting
CJGeo proposed polyurethane grouting to fill voids below the pavement slabs and raise them back into position. Polyurethane grouting allows for immediate resumption of traffic after repairs. This is important for roadway work in that work time can effectively be the entire time of a lane closure.
Another advantage of polyurethane grouting is hole drilling speed. The average time for drilling the injection holes (18″ on this project) was 27 seconds. This allows for grouting to start almost immediately after traffic control is set. No time is wasted sitting around waiting for large diameter holes to be drilled through the slabs.
Logistics of polyurethane grouting are also much less complicated than mudjacking or pressure grouting. A single polyurethane grouting truck brings up to 300 cubic yards of in place material to the site.
Three CJGeo polyurethane grouting crews worked over a period of seven nights to complete the bridge approach slab lifting repairs at the six locations. At least one lane of traffic was open at each location during the repairs. Average hole spacing of 5 feet, with a polyurethane grout specially formulated for mid-range mobility ensured a complete fill, while retaining control over lateral spread of the grout. This facilitated taking a 6″ belly out of a shoulder slab without material blow out, and for correcting short bellies.
Each night when the repair window closed, repaired areas were immediately reopened to unlimited vehicle traffic.