Nowhere is this about replacing the steel reinforcement in a...

Nowhere is this about replacing the steel reinforcement in a structural slab. It is about improving the integrity and performance of the surrounding concrete. The two elements must not be confused.
Good example- suspended concrete bridge slab with reinforcement, sways and moves over the years with constant traffic, the engineered steel reinforcement will perform to its design loads but the concrete having minimal flexural properties will develop microscopic hairline cracks. The CNTs will work to bridge and prevent these microscopic cracks.