Depends on thermal expansion coefficient.

If the solution chemistry is compatible with concrete then it might be mixed in and polymerize together, and that would be yet more exciting.

Probably not. Steel rebar is used because it is ductile, that is it stretches and fails gracefully, which complements the brittle nature of concrete.

This material is likely brittle, probably similar in overall behavior to graphite.

There are already very good non-steel rebar - fiberglass. Many manufacturers, easily searchable. I'm astonished it hasn't completely taken over the construction industry, as rusting steel rebar expands and destroys the concrete it is supposed to be reinforcing (concrete is great in compression, lousy in tension).

Just coat the rebar, one of its properties is that it's impermeable to liquids and gases.

That doesn't help if it expands differently from the rebar and concrete. One of the advantages of rebar is that it has a similar coefficient of thermal expansion so when there are temperature changes the concrete and rebar expand and contract in sync and don't have stresses from that.

Lots of problem here - it doesn't expand/contract at the same rate. So it will likely delaminate over time.

It is also not inert. So it may in fact, be attacked by soil PH, etc (maybe not, not enough info in the article).

Also, one of the problems with coating most things is achieving good enough adhesion that it both doesn't delaminate, and that molecules can't slip through.

If it's stronger & lighter than steel and produces less CO2 than steel manufacturing...

Forgot the most important part, is it cheaper than steel?

Also can it be produced at scale we produce steel... Which is mind boggling when you really start to think of all the stuff.