Originally Posted by pondering_it_all
I wonder if they can use other materials for rebar, that can't corrode. Like carbon fiber.
Carbon fiber would be great, though currently cost prohibitive. The addition of carbon to the concrete mix, in the forms of CO2 and biochar, are proving to be beneficial in several ways, including high early strength and durability - it’s also a way to sequester atmospheric carbon for long periods.

Air entrainment in the concrete is also a formulation that has been established commonly over the past several decades, reducing weight while decreasing water permeability and improving resistance to cracking and spalling.

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller