[lll-o-lll]

Rebar reinforced concrete fails, I assume, because the rebar rusts? If so, isn’t the issue greatly reduced (potentially) if we were to use the quicklime process of the Romans? If the self-healing prevents water penetration, does that stop rebar from rusting?

[mjevans]

Steel is really strong vs tension, not so much vs water / rust / chemical reactions.

It's also relatively cheap. Maybe carbon nanotube ropes could replace that after we have cheap mass production?

[kadoban]

There's already other ways to reinforce concrete, one I know of is embedding kind of fiber-glass mesh in it instead of rebar. I quick google suggests that this might be called Fiber Reinforced Polymer (FRP) reinforcing, or possibly that's a different thing I'm not really an expert.

I assume you could use a whole bunch of different materials really, including other metals that don't rust in the same way as steel does.

[lll-o-lll]

The point, is that the steel needs water to rust. The cracks allow the water, but supposedly the Roman concrete self heals and water does not continue to penetrate. One assumes, therefore, limited rust (perhaps). In practice this may not be the case, but surely someone has tested? Steel has the right properties + price; if you can keep the water out.

[mjevans]

Concrete isn't waterproof, it might resist the flow of water, but as even most rocks are, there is at least a slow migration of water through the material.