Roman Architectural Concrete! Its actually very interesting :)

[Imperial Dave]

Absolutely fascinating article on the composition and reasons for Roman concrete longevity....well I found it fascinating!

http://newscenter.lbl.gov/2014/12/15/roman-architectural-concrete/

[Chuck the Grey]

I agree that it's a fascinating article and should serve to remind us that the ancients weren't as technologically deprived as we often think. I remember reading an article some years ago on the study of Roman seawater concrete that Marie Jackson was involved with.

As a side note, I doubt if my son, a mechanical engineer, would share my fascination with Roman concrete technology. When he was a university, he would often make snide remarks about civil engineers wasting their time watching concrete dry. (No offense intended to any civil engineers on our forum.)

[Imperial Dave]

Always been fascinated with the technological forwardness (as opposed to perceived backwardness) of the ancients including the Romans. I can remember from an early age being astounded that the Romans could make waterproof concrete (and still am) 

[Patrick Waterson]

It is largely through use of volcanic materials.  Something similar was noticed during Pacific island hopping during WW2 (apologies for going out of period, but you will see why): the islands defended by the Japanese were often volcanic in origin, and they found the rock easy to mine but once exposed to air it set hard - very hard.  The removed detritus made an excellent basis for concrete and was used to build strongpoints capable if resisting almost anything up to a direct hit from a 14" shell.  It was this which first put me onto the possibility that Roman cement was similarly composed, volcanic rock being fairly readily available in southern central Italy, so after a chat with the owner of the Shell Temple at Margate, he told his contacts and awareness seems slowly to have spread from there.  Or someone else came up with the same idea for similar reasons - I was concerned with other things at the time.  Prior to the 1980s the composition of Roman cement had been an unsolved mystery, the secret assumed lost with the demise of masons' guild personnel during the Black Death.