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OathOfFeanor t1_j9wh6ac wrote

Reply to comment by darkfred in It seems like we havent heard anything about carbon nanotubes for almost a decade. is there anything exciting involving those these days? by mintysmellshowntell

You are confusing carbon fiber with carbon nanotubes.

Carbon fiber is fiberglass with carbon instead of glass. It's the same thing, but stronger. But it's still encased in a plastic binder, still micro or macro in size (not nano-scale).

Carbon nanotubes are pure carbon (sometimes with some oxides in there at low concentrations).

Their behavior and impact on the chemistry of the concrete are entirely different.

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darkfred t1_j9xc3ix wrote

Not really. From a macro engineering perspective all of the current research in carbon nanotubes for structural use is aimed at producing longer tubes, often referred to as carbon nanotube fibers. Nanotube fibers that are long enough to be used in the same way as carbon fiber, or glass fiber, woven together and bound in a matrix to produce strong macro scale materials.

ALL current carbon fiber use in concrete is mechanical and exactly equivalent to how glass fibers are used. Except that the carbon nanotubes are far smaller so although they provide stronger local support the scale of the cracking they prevent is reduced vs other fiber mix-ins.

Like I said, real innovation will come when carbon nanotubes are long enough to be used at a structural scale rather than microscopic. It's neat to talk about futuristic meta-materials and they can slightly change the thermal conductivity and microscopic crack formation of concrete but from a large scale engineering perspective most of the small scale nanotubes that can be purchased in bulk today would be the same as mixing a bag of soot into the concrete.

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OathOfFeanor t1_j9xe82n wrote

> Not really. From a macro engineering perspective all of the current research in carbon nanotubes for structural use is aimed at producing longer tubes, often referred to as carbon nanotube fibers. Nanotube fibers that are long enough to be used in the same way as carbon fiber, or glass fiber, woven together and bound in a matrix to produce strong macro scale materials. > > ALL current carbon fiber use in concrete is mechanical and exactly equivalent to how glass fibers are used. Except that the carbon nanotubes are far smaller so although they provide stronger local support the scale of the cracking they prevent is reduced vs other fiber mix-ins.

This is absolutely 100% false and if you just browse the ACI YouTube channel you will find a whole ton of research of nano-scale carbon. The goal is NOT to make it micro or macro scale because the nano scale provides unique benefits.

It is incredibly different from how glass fibers are used and I recommend you educate yourself on the subject or else just stop talking down about a new technology you are unfamiliar with.

Again, carbon fiber and carbon nanotubes are very different materials.

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