Fixing a section or pouring a new sidewalk
If one panel has sunk or cracked and the rest of the walk is sound, replacing just that section between the joints usually makes sense. When cracks run through most of it, the top is flaking all over, or water sits against the house, the trouble is usually the base or the slope, and a patch won't fix that. I'll tell you which way I'd go and why, and I'm glad to say so when a repair is enough.

