In the driveway of our new home, I just noticed a spot on the driveway that makes a creak/crunch sound when stepped on. The area that is about 3 or 4 inches across, and looks very subtley different than the surrounding cement. I slightly different shade/texture and possibly ever so slightly higher than the surrounding cement. It doesn’t really look like a patch job though. Pushing on it with my hand was not enough force to get it to creak. It took a fair amount of weight from stepping on it to do so.
I would guess that a layer of the cement is raised and flexing to grind against that underneath it. I can’t figure how the whole thickness of the driveway could give in a manner to make that noise. And I suspect that if I keep stepping on it that it will eventually crumble/crack. What is the likely cause? Is it indeed likely a patch, or is there just a bubble in the cement? Can anything be done to prevent further damage?