How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

Modern concrete has steel rebar, which is very useful, but eventually corrodes. Stainless steel rebar could be used if longevity mattered, but usually it doesn’t because the building will likely become functionally obsolete and need replacing before then.

A picture of one of these toilets would have been useful.

Related, Grady Hillhouse on the myth of Roman concrete.

> The miracle of modern chemistry has given us a wide variety of admixtures like superplasticizers to improve the characteristics of concrete beyond a Roman engineer’s wildest dreams. So why does it seem that our concrete doesn’t last nearly as long as it should? It’s a complicated question, but one answer is economics. There’s a famous quote that says “Anyone can design a bridge that stands. It takes an engineer to build one that barely stands.” Just like the sculptors job is to chip away all the parts of the marble that don’t look like the subject, a structural engineer’s job is to take away all the extraneous parts of a structure that aren’t necessary to meet the design requirements. And lifespan is just one of the many criteria engineers must consider when designing concrete structures. Most infrastructure is paid for by taxes, and the cost of building to Roman standards is rarely impossible, but often beyond what the public would consider reasonable.

https://practical.engineering/blog/2019/3/9/was-roman-concre...

A large part of why Roman concrete lasted longer than ours tends to is that we suffer from a shortage of narcissistic emperors with the means to wield entire economies towards their own immortality.

Yes, but you have to replace the sacrificial anode every so often.

https://en.wikipedia.org/wiki/Galvanic_anode

> Stainless steel rebar could be used

There are also coated and non-metallic rebars.