In my extensive (20 minute) broad search (Duck Duck Go) of the internet, I have been unable to find the answer to my question. I found a lot about where and when and how certain fortifications were used - but not how they were built. Hadrian's wall and a few pics I found of Castelum were all built of stone. I'd be really surprised if the Romans didn't also use earthworks when necessary (heck, we still use them) but that's not my question. What I'm trying to find out is whether or not there was any extensive use of concrete AS fortification - not as a supplemental (like mortar or ramparts) but as the main fortification itself.
Why I want to know is because I grew up with the myth that the technology for concrete had been lost in those horrible Dark Ages - well, turns out, not so much (which, if you think about it, is kinda ridiculous on its face - mortar is just an ingredient away from hydrostatic concrete). What is clear is that concrete was rarely used in the Medieval period. It couldn't have been impossible to import volcanic ash - so why?
I'm wondering if it has something to do with the differences in emphasis. Romans were building huge public works - baths, latrines, fora, circus, arenas, et al. Medieval governments, probably due to the large scale of fracturing, were building fortifications and churches. Mostly fortifications - castles and keeps being more common and bigger than cathedrals and monasteries (admittedly, maybe not by much and not at all by the Late Medieval).
Concrete doesn't strike me as a good fortification material - compressive strength, you betcha - tensile? Not so much... Toss a couple large rocks into it with a trebuchet - and with no massive amounts of rebar as we would use now - this doesn't sound like it ends well.
For public works where you're building a lot of stuff and need to save on building material, concrete is perfect (throw on some marble after it dries and no one is the wiser). But I suspect stone is superior for fortifications (up until cannons catch up in the 17th century) simply because it performs better under tension (like huge boulders getting tossed at it).
The Romans and the Medieval knights were the guys getting shot at - I expect they had a much better knowledge of what they preferred to hide behind during the shooting. Which is why I want to know what the Roman's used to build fortifications from when they had a choice (once shooting starts you take what you can get).
Why I want to know is because I grew up with the myth that the technology for concrete had been lost in those horrible Dark Ages - well, turns out, not so much (which, if you think about it, is kinda ridiculous on its face - mortar is just an ingredient away from hydrostatic concrete). What is clear is that concrete was rarely used in the Medieval period. It couldn't have been impossible to import volcanic ash - so why?
I'm wondering if it has something to do with the differences in emphasis. Romans were building huge public works - baths, latrines, fora, circus, arenas, et al. Medieval governments, probably due to the large scale of fracturing, were building fortifications and churches. Mostly fortifications - castles and keeps being more common and bigger than cathedrals and monasteries (admittedly, maybe not by much and not at all by the Late Medieval).
Concrete doesn't strike me as a good fortification material - compressive strength, you betcha - tensile? Not so much... Toss a couple large rocks into it with a trebuchet - and with no massive amounts of rebar as we would use now - this doesn't sound like it ends well.
For public works where you're building a lot of stuff and need to save on building material, concrete is perfect (throw on some marble after it dries and no one is the wiser). But I suspect stone is superior for fortifications (up until cannons catch up in the 17th century) simply because it performs better under tension (like huge boulders getting tossed at it).
The Romans and the Medieval knights were the guys getting shot at - I expect they had a much better knowledge of what they preferred to hide behind during the shooting. Which is why I want to know what the Roman's used to build fortifications from when they had a choice (once shooting starts you take what you can get).
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