Expansion joints fail quietly, and the slab pays the bill.

Cracking Expansion Joints: diagnosed and explained.

Expansion joints are the deliberate gaps built into concrete so slabs can grow and shrink with temperature without cracking each other. The joint filler has two jobs: flex with that movement, and keep water from reaching the soil below. When the filler dries out, cracks, or pulls away from the concrete edge, both jobs fail at once. You will see cracked or crumbling filler lines, gaps where the material has separated from the slab, weeds or debris colonizing the joint, and, as the failure matures, secondary problems arriving on schedule: slab edges chipping where panels now press or grind against each other, sunken sections where water slipped through the open joint and eroded the base, and cracks spreading from the joint into the slab field. In California, Arizona, and Nevada the sun does most of the damage, baking the flexibility out of joint material years before the concrete around it wears out, while big daily temperature swings in the desert markets work the joints harder than almost anywhere. Failed joints are one of the cheapest concrete problems to fix and one of the most expensive to ignore, because the joint is the front door for the water that causes settlement.

For the repair side of this, the concrete repair solutions page lists every method Dalinghaus installs, including the ones that fix problems other than cracking expansion joints.