I think the problem was that the big concrete pad needed expansion joints. Those joints should have been angled such that when the pad is in use the venturi effect caused the concrete slabs to be sucked towards the ground.

However, this wasn't the case - the joints were vertical (as would be normal for laying a parking lot), and the end result was exhaust gasses went through the joints and lifted the slabs up, causing many of them to get blown away.