I was asked why does it cost Big Buck$ to repair crumbling balconies
In the above case the slab can't be simply repaired the steel reinforcement and cracked concrete area needs to be cut out, replaced/repaired & certified by experts.
Cause...Long term water penetration through cracks resulting in concrete cancer
initial design/engineering factors that could have prevented this are additional crack control reinforcement, extra concrete cover, lean concrete mix design, proper concrete placement & vibration, & protective external waterproofing/coatings ,etc,etc
Unfortunately it's too late now extra prevention is always better than cure.