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Comment by culi | Hacker News Reader

The oldest buildings in the world[0] are as old as they are because they use materials with lifespans of much less than 100 years. Instead they make them modular. Make it so that you can take out parts of the building to replace them without collapsing the whole thing. Instead we build our buildings in such a way that makes maintenance very hard and costly. We prefer to pretend like our buildings will last forever rather than actually plan for the inevitable degradation

There's small scale movements towards changing this. Some cities are specifically building buildings in a way that makes them modular and reusable[1]

[0] https://en.wikipedia.org/wiki/H%C5%8Dry%C5%AB-ji

[1] https://www.bbc.com/future/article/20230207-can-we-design-ci...

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> The oldest buildings in the world[0] are as old as they are because they use materials with lifespans of much less than 100 years.

Rather apropos counter-example: Rome's Pantheon is several hundred years older and built in part of concrete.

The ancient Roman concrete was very different from modern: it was more thick, could not ne poured etc. But more importantly, it had no rebar, which is the main thing that corrodes over time. Ancient buildings could use molten lead to join together pieces of stone, but steel could not be made in the volume needed for reinforced structures.

Thing is we can use rebar in concrete for indefinately long use if we plan ahead, use sacrificial annodes to stave off corrosion or use stainless steel or use carbonfiber rebar as they won't rust. Hell using a polymer coating on rebar can prevent moisture contacting the surface of steel and rusting but that would require added cost and care when preping to prevent the polymer from being damaged prior to being embedded in concrete.

Are the thermal expansion characteristics the same as for regular steel rebar?

Reinforcing rebar and fibers can also be made out of basalt, which takes care of both corrosion and thermal expansion issues.

Un reinforced.

Also in Japan, there has been an increasing use of aluminum (!) in construction, since it will generally be melted and re-used after the structure is no longer useful.

https://www.acsa-arch.org/chapter/toyo-itos-second-age-of-al...

What's the problem with aluminium? I would always build structures out of aluminium if aluminium would be strong enough. It has extreme corrosion resistance, it's cheap, it's easy to handle, you can easily make almost any imaginable shape with it, you can cheaply reuse it, it's very light.

Also the low melting point in case of fire.

Aluminiums corrosion resistance is mostly myth so.

Aluminum corrosion resistance is caused by a thin film of aluminum oxide which protects the rest of the material.

Aluminum's corrosion resistance is decent, but it's particularly weak to alkali, and cement is alkaline. So.

And to salt, and to contact corrosion woth, e.g., steel. Especially the last one is quite often ignored. Even by people at VW and General Dynamics.

Aluminum is generally much more expensive than other construction materials, but less obviously, it has practically no fatigue limit, meaning a structure made of aluminum will eventually fail under repeated loads.

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