keep in mind, 'they think they figured out why roman concrete was so good' many times. https://en.wikipedia.org/wiki/Roman_concrete#See_also https://en.wikiped

keep in mind, 'they think they figured out why roman concrete was so good' many times. https://en.wikipedia.org/wiki/Roman_concrete#See_also https://en.wikipedia.org/wiki/Roman_concrete#See_also "The strength and longevity of Roman marine concrete is understood to benefit from a reaction of seawater with a mixture of volcanic ash ... The result is a candidate for "the most durable building material in human history." In contrast, modern concrete exposed to saltwater deteriorates within decades"