They may be referring to this, if a rock in the concrete is close to the surface, the hot sun will heat the rock causing it to pop out leaving a small hole. In the Northern states this can happen with a porous rock that absorbs moisture and then freezes. I had this happen to a couple of spots in my driveway when we first moved in, that was the explanation I got.
__________________
Retired Firefighter
Indianapolis, Indiana
"Livin our Dream"
|