Total slab replacement is rarely done unless the pavement has serious deficiencies beside the loose joints. Full-depth joint replacement costs a lot and leaves two joints in place of one. Subslab grout injection works by shoring up the slab edges, but because it doesn't address the root problem of poor load transfer, this method often fails as a long-term fix.
Dowel-bar retrofit is a way to put dowels in a finished pavement. First, saw slots across the loose joints, cutting about halfway through the slab thickness. Then place smooth dowel bars in the slots and lock them in with strong mortar. The dowels are typically smooth round bars of epoxy-coated steel, about 1.5 inches in diameter and 18 inches long. The usual spacing is 12 inches center-to-center. Getting the details right is important and can be difficult, but when done well dowel-bar retrofit provides very effective load transfer.
A new device called a mechanical joint stabilizer provides results similar to those from dowels. The stabilizer is an aluminum cylinder, 3 inches in diameter, split lengthwise, that is installed vertically in a drilled hole. An internal mechanism pushes the two sides apart with about 8000 pounds of force, locking the stabilizer into the concrete and bridging the joint. Springs maintain the connection as the joint opens and closes. Spaced about 4 feet apart, stabilizers can reduce the differential movement to less than 0.010 inch. Once the stabilizer is tightened, the pavement is ready for use. The device was developed for warehouse floors, though, and may lack the movement capacity to handle exterior pavements subject to large temperature swings.
George Garber is a partner in FaceConsultants, Lexington, Ky.