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Comment by cftm | Hacker News Reader

They're starting to break the code on it, but there are concrete docks that Rome built 2000 years ago that still exist today - we have trouble building salt resistant concrete docks that last ~100 years.

Apparently it has to do with using a certain type of volcanic ash in the concrete...

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We've known for a good while how Roman concrete works. The reason that nobody uses it is that the economic incentives aren't there. Roman concrete is more annoying to work with and takes way, way longer to usefully solidify than cheap modern concrete. Yes, it will last longer, but almost nobody these days cares about paying through the nose for a building that will last more than 100 years when you could just force future generations to pay to rebuild it when it collapses.

It's a test of intergenerational commitment, because you are asking the generation that bears the cost of construction to build something that benefits many future generations. But the future generations, even though they enjoy all those beautiful old buildings provided to them by their ancestors, are tempted to go cheap for the building they need to build themselves.

So as people become disconnected from the great chain of being that connects your ancestors to you and you to your descendants, they start to build ugly, disposable buildings.

Perhaps one approach might be to provide lower interest rates to buildings based on the expected life and maintenance cost. So a building that is expected to last 500 years would have a much lower annual interest burden than a building expected to last 70 years. That would require some type of government guarantee for the 500 year bond.

> we have trouble building salt resistant concrete docks that last ~100 years

Because of failures in technology/ability, or lack of incentive/motivation? It isn't obvious to me that anyone cares to build long-lasting structures..

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