Pavement sinks because exterior concrete is always on the move. Soil settles. Moisture moves soil up and down. In cold climates, frost can heave and lift concrete slabs.
Tearing out, hauling away and replacing an entire sidewalk or driveway is expensive – and hard on the environment when all that concrete ends up in a landfill. But if your concrete is in pretty good shape, you can avoid this process. By “pretty good shape” I mean large sturdy pieces and a surface that is smooth and solid.
If that’s the case, a process called mudjacking can level the concrete slab. For about one-third the cost of replacement, a specialized contractor will drill holes in the slab and pump ground stone or a cement slurry under it. With just a little bit of pressure, the slab will be raised back into position. A few more holes are used to fill voids, and then a concrete mix is applied to patch the holes flush with the surface.
By Tom Feiza, Mr. Fix-It