TAH, you are right. Spalling will occur if the concrete freezes (not happenin' in Negril), is poured when it it is too hot and not sprinkled with water or it was a very poor mix (2000 mix or less) Sidewalks in Pennsylvania are poured 4" thick with at least 3" of crushed stone (drainage), expansion joints evey 20 feet (Probably not needed in Jamaica) and at least a 2500 mix of concrete. Driveways are normally (0r should be) 6" thick, but this would help more with cracking not spalling. The higher the mix (3500 for example) the more cement is added to the concrete.
Regards,
Bob