Why was Roman Concrete Forgotten during the Middle Ages?

During late antiquity, concrete all but vanished from the Mediterranean world, and would not be used widely again until the twentieth century. This video explains why.

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Chapters:
0:00 Introduction
0:39 Understanding Roman concrete
1:29 Early experiments
2:25 The apogee
3:33 Squarespace!
4:19 Geographic limits of Roman concrete
5:00 The decline of concrete
6:28 Final notices
7:26 Not forgotten, but gone

Thanks for watching!

[justinbetland]

My interest in Ancient Rome is part of why I decided to become a concrete finisher.
The thought that the things I pour might be around long after I'm gone, always fascinates me.

[neutronalchemist]

The Roman concrete remained known in Italy as "calce idraulica" (hydraulic lime) and was used for underwater structures and impermeabilization of ducts. However brics were preferred for the building of large structures (see for example the dome of Santa Maria del Fiore, in Florence, the first in the world to beat the diameter of the Pantheon) for a simple reason. To produce brics in the immediate proximity of the building, you only need clay and heat, and clay is abundant almost everywere. Not so much for pozzolana and lime, that tend instead to be mutually exclusive, where there is one, there isn't the other.

[joelsmith]

The scale of the Pantheon's dome was not fully impressed upon me until I saw that photo featuring the crack.

[gorlab]

Roman concrete is actually what got me into becoming a history buff, I took an engineering class as an elective in high school and our teacher made us watch a documentary on ancient engineering. It was astonishing to learn the techniques and inventions they already had so long ago, and we ended up spending a whole week just learning about concrete with Roman concrete being the start of the lesson. Absolutely crazy stuff, until that class I had never even begun to comprehend the fact that some of these structures are still standing after literal ages of history.

[brianmccarthy]

Pozzolana is such a good material for concrete because it has immense amounts of small silica strands in it. They prevent cracks from growing as the concrete is being pulled, or in tension. Concrete, like stone, is very strong when it's being pushed on, or in compression. The combination of compressive and tensile strength of the material, plus the way it was bedded in layers, makes Roman concrete one of the best building materials ever developed. In the last century and a half concrete has undergone both a resurgence in popularity and a great deal of technological and material development. The inner secrets of Roman concrete have only become revealed in the last few decades due to our increased understanding of mechanical stresses, due in many ways to aerospace technology, and our better understanding of materials chemistry. There are good Wikipedia articles on this. We're still developing new concrete compositions to match and continue to develop this amazing Roman invention.

The amazing technology of their brickwork, such as used so successfully and in such a sophisticated manner in the Hagia Sophia, is also being studied and developed as is their terra cotta technology. We still have a lot to learn from Classical and ancient technology.

[verandi]

No annoying music, no chitty chat, straight to the point, eloquently and coherently spoken, very informative, wonderful video

[medea]

Visiting the Pantheon was easily one of the most mind-blowing experiences an engin-nerd like me could have - walking in through the enormous portico doors, your eyes instinctively drawn upward to the engineering masterpiece of the concrete dome & the oculus flooding the chamber with light.... then remembering that this structure has stood for near 2, 000 years.... and it's _completely unreinforced concrete...._ still gives me chills!! 😲💫💜

[kevinspilker]

A big problem is that the ingredients that made Roman concrete so special (fly ash, salt water, lime) wouldn't be available in other regions, and would have been hard to allocate during periods of conflict and division within areas that these ingredients would be sourced from.

[vietnam]

I randomly thought of this question one day. I was interested why they forget about concrete. This video really helped. Thanks!

[GlennMartinez]

I appreciate your efforts and enjoy the lack of hype and bravo opinion so popular in YouTubes these days. I will go order up your book today!

[j.dunlop]

The Pantheon, is the size of half football field, even fifty years after seeing it, it's awesome in my mind.
Doors, also a serious engineering marvel!

[Arterexius]

The Pantheons dome is just so insanely huge. Photos can say a lot, but nothing beats standing inside the Pantheon, looking up. It's just so massive and you feel soo tiny. It's awe inspiring

[perceivedvelocity]

I love how you cover things that other channels would never pay attention to. Thanks!

[joseph]

you created such a great channel: than you very much! ☺️💝

[cherylsmith]

I grew up in a small town with alot of Italian immigrants & each of their homes has some sort of unique concrete creation. One yard features a fence with concrete posts & is still my favorite

[timcent]

I have to say your style of narration is wonderful for me. Using pauses helps greatly for me to follow along with the information.

[johnspizziri]

That was outstanding! I talk about this in my class, but never knew why it was "forgotten ". Truly a case of occams razor viv a vis this subject.

[ourfarmhouseinspain]

I've often wondered why the Roman constructions of concrete weren't more widely copied around Europe, and why the use of it disappeared. Thank you for a very clear explanation.

[curtislowe]

Thank you for including the photo of the Pantheon dome with people for scale. I never realized how large and how high up the square features in the dome are.

[American_Made]

Love these videos. Thanks for doing them.