I'm thinking about the end of life-cycle for concrete made with millions of tiny fibers instead of rebar; can one recycle it in the same manner we do now? It's easy to crush the concrete away from rebar to separate the two components and the ferrous nature of the steel rebar makes it even easier to get useful aggregate from old concrete. But if it's full of threads made of fiberglass, graphite or even graphene, what then? Will those contaminate the aggregate with a material that detracts from its usefulness? To the point where we have to landfill older fiber concrete?
Seems like a solvable problem, I hope.
There is also a nagging concern I have about tiny fibers and the potential health and environmental hazard. Folks who work with fiberglass need to be protected from inhaling fine particles, and we all know about asbestos. Will these brilliant new nano-fibers end up having a similar effect when aerosolized during emplacement or removal and 'drill' into people's lung tissue and foment cancer? I really hope not because I would hate for the engineering potential of nano-fibers to be torpedoed by this potential problem.