A popular repair technique is concrete leveling using polyurethane foam. This is injected below the sunken slab to lift and support the concrete back to its original position. The polyurethane expands to fill any voids or washed-out areas beneath the driveway.
The process can successfully level sunken sections ranging from a few inches to several feet. No digging or demolition is required. The concrete slabs are lifted back into place from underneath. This restores the smooth flat surface without having to rip out and replace the entire driveway.
For more extensive sinking across large areas, a full driveway replacement may be warranted. This involves ripping out all the existing concrete, preparing the soil beneath, and pouring new slabs. Replacement ensures you end up with a completely level and properly supported driveway.
However, it is costlier and more disruptive. Heavy equipment is needed to remove and dispose of the original concrete. The prep work also often requires excavating down a foot or more to create a stable base. Then forms must be set up, reinforcement added, and new concrete poured and finished.
The condition of your slab will determine whether polyurethane leveling or full replacement makes the most sense. Multiple, cracked sections spread across the entire driveway typically call for replacement. Isolated sinking of mostly intact slabs may be better suited for slab lifting.
Polyurethane injection offers a less expensive and less invasive repair option compared to wholesale replacement. It also uses fewer resources while producing less demolition waste.