The rebar expands and cracks the concrete. They had to redo all the outside decks in the condo I lived in beachside Cocoa Beach. They replaced the rebar with coated rebar. I didn't need a alarm clock for months. At exactly 9AM the jackhammers would wake me. Living there was always a hassle. A high rise full of assholes basically. Some kid flushed his ball down the toilet, then the toilet started over flowing in my place. The maintenance guy was the only person who was cool. Then there were the hurricanes...