Stainless steel rebar is a thing. It's expensive, but structures built with it last much longer. Washington State now has a policy that bridges over salt water will be built with stainless steel rebar. Stainless steel costs much more, but total project cost goes up less than 10%.

Epoxy coated rebar looked promising for a while, but it's on the way out. Water gets in at cuts and joints. So all field joints have to have field patching.

There is a great comparison. Two piers were built in the 1940s, side by side, one with carbon steel rebar, one with stainless steel rebar.[1] Go look.

[1] https://worldstainless.org/wp-content/uploads/2025/02/ref19_...

[1] https://worldstainless.org/wp-content/uploads/2025/02/ref19_...

As I understand it, concrete has excellent resistance to compression but fails easily on traction, while steel bars are exactly the opposite. That is why you put rebar in concrete: the steel handles the traction loads and the concrete handles the compression. This works well because both materials have similar coefficients of thermal expansion, so as the temperature changes they both expand and contract at the same rate. I suppose you can engineer fiberglass to have the same thermal expansion coefficient and use it to replace steel (assuming it is just as strong on traction). But how would you "build without rebar even"? Wouldn't your beams start cracking at the bottom, where they are subject to traction?

> but that is more costly and and less efficient.

Maybe this is the clue as to why our concrete crumbles after 100 years: it's not economically efficient to make it last longer?