[toss1]

What baffles me (as someone working in Advanced Composites) is why not simply get rid of the steel, the steel-concrete interface, the chloride ion and corrosion problem altogether — by instead using rebar made of composites?

Rebar of fiberglass, carbon fiber, basalt, and other combinations is all redily available and has known properties.

The key issue is that steel will corrode, then expand and put the concrete in tension (which concrete sucks at reacting), causing the concrete to crack, then spall off. None of the composites do this.

Yet, despite composites being available for years, and even being cheaper than steel [0], they are being picked up at remarkably slow rates.

It seem blindingly obvious to me that everyone should have just switched some time ago. Yet, this has not happened. Why?

[0] https://ernestmaier.com/is-fiberglass-rebar-more-affordable-...

[joelegner]

Alternative reinforcement is an area of ongoing research. There are issues with cost and stiffness of the more exotic types. Research is probably slower because of the need to at all times be confident our structures are safe. We cannot freely experiment with exotic reinforcement in the built environment. It needs to be proven, first analytically then in the laboratory, then in pilot projects, and then in the legal and political forum before adoption in life safety critical applications like bridges and buildings.

[toss1]

Yes, I certainly agree that validation research needs to be done, and done absolutely solidly before wholesale switching .

Yet in this case, the existing tech is known bad (although TBF, the how-bad is well-characterized), and the new technologies are already qualified to fix this bad tech, e.g., carbon-fiber re-wrap of disintegrating steel-rebar bridge columns [0,1,2].

Certainly seems that applications like road-bed construction that require rebar, where the worst-case is a part of the road gets potholes prematurely, vs abridge or building collapsing, should already be mandated to use composite rebar. That would significantly increase the data set that can be used for real-world aging studies, with minimal risk?

[0] https://www.hj3.com/blog/dot-bridge-column-repair

[1] https://www.advancedfrpsystems.com/how-to-repair-concrete-co...

[2] https://hydratechllc.com/resources/case-study-dot-bridge-con...