Thomas S. Hart Middle School Slab Lift

Challenge

The Pleasanton California Unified School District commissioned the repair of concrete slabs in the front entrance, courtyard and pathways leading to classrooms around the Thomas S. Heart Middle School campus. All 20 of these concrete slabs had settled, some as much as 3 inches. This created tripping hazards and increased the risk of potential injury to staff and students and therefore the school district’s exposure to claims. The Pleasanton California Unified School District specified that the concrete be lifted back towards level, voids be filled beneath the slabs and the entire project completed in less than a week during a school holiday as not to disturb students and faculty. Removal and replacement was an option but ultimately dismissed because it would take much longer, be more expensive and walkways would be unusable for the duration of the removal.  

Solution

Solution

The Pleasanton California Unified School District selected PolyLEVEL polyurethane injection to fill the voids and lift the concrete walkways back towards their original elevations. PolyLEVEL is a two-part urethane that expands into a rigid foam used to fill voids, stabilize slabs and lift concrete. Once injected through small 5/8-inch drilled ports in a slab or surface, a chemical reation converts the liquid urethane components to a strong rapidly-setting foam material. In its foam state, PolyLEVEL is relatively light, weighing two to six pounds per cubic foot, other void filling materials can be up to 120 pcf adding significant weight to soils or base materials, which may cause further settlement.

With a typical in-place compressive strength of at least 75 lbs per square inch PolyLEVEL 250 was the best solution to support the slabs. Foundation Repair of California injected a total of 523 pounds of PolyLEVEL 250 through 56 half inch ports. The expanding PolyLEVEL foam filled the voids and lifted 20 concrete slabs towards level minimizing or eliminating trip hazards. The entire project was completed in one weekend as to not disrupt students, faculty and normal school functions.