Slabjacking chosen to solve settlement problem with concrete slabs.

Fort Lee, New Jersey was experiencing a settlement problem with concrete slabs along a heavily traveled roadway. According to Fort Lee Publics Works Director Dan Kincaid, the slabs had settled 4 to 6 inches in some locations, voids were evident, and more settlement was expected due to utility washouts in the area over the last few years. Kincaid pointed out that settlement often occurs without warning and can damage cars before a lane closure is set up to perform emergency repairs.

SsesCo, Inc. was hired to raise the settled slab using slabjacking, which involves pumping a cement / lime slurry through a grid pattern of drilled holes in the settled slab, lifting the slab back to its original elevation, while stabilizing the soil underneath the slab. This process eliminates the need for labor-intensive removal and replacement of the slabs. “For example”, said SsesCo President Thomas F. Planert, P.E., “an 8ft by 5ft slab was lifted 6 in. in two hours and no further work, landscaping, cement finishing, or hauling of old concrete to a landfill was necessary.”

A void survey performed by SsesCo on the remaining slabs in question showed that about 50 percent of them would not require slabjacking for soil stabilization, saving the town an anticipated repair cost. By combining radar void mapping with slabjacking, towns can budget for planned maintenance, versus having to perform extensive emergency repairs, Planert pointed out.

Slabjacking has been used in the midwest and western parts of the country for over 40 years and is a well known system for raising settled concrete slabs in roadways and sidewalks, said Planert. However, slabjacking required that the concrete be in a relatively sound structural condition. Slabs with cracks less than 2 ft apart typically should be replaced, he explained.

Fort Lee is currently considering slabjacking for another busy intersection with settlement problems.

Reprinted with permission from Public Works Magazine.