Why Roman concrete is still stronger than RAAC (and other modern concretes)
Why Roman concrete is still stronger than RAAC (and other modern concretes)
The concrete dome of the Pantheon in Rome remains stable enough for visitors to walk beneath, and some Roman harbours have underwater concrete elements that have not been repaired for two millennia – even though they are in regions often shaken by earthquakes.
Whence this remarkable resilience of Roman concrete architecture? It’s all down to the chemistry.
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This is one of the most commonly touted engineering myths that simply doesn't hold up to even a brief analysis. The first glaring problem is the inherent survivorship bias behind claiming Roman concrete was objectively better than modern concrete. As other users have already mentioned, modern concrete is actually very strong and exceeds the strength of Roman concrete when such strength is required, but where it really has an advantage is in its consistency.
If every concrete structure built in Rome was still standing and in good shape to this day, engineers would be salivating over the special blend and would be doing whatever they could to get their hands on it or replicate it. But we don't see that. We see the Roman concrete structures that have survived the test of time (so far), not the myriad structures that have not. Today's concrete on the contrary is deliberately consistent in chemistry, meaning even if it typically isn't designed to last hundreds of years, you can say with a great deal of confidence that it will last at least X years, and all of it will likely exhibit similar wear and strength degradation behaviors over that same duration.
There are other factors at play too:
- Romans didn't use steel reinforcing re-bar, instead opting for massive lump sums of concrete to build structures. These massive piles are better against wear and porosity-related degradation, especially due to the self-healing properties of the Roman concrete blend due to volcanic ash helping to stop crack propagation.
- Our modern concrete structures are much, much larger in many cases and/or are under significantly higher loads. Take roads for example—no Roman road was ever under the continued duress of having hundreds of 18 wheelers a day rumble over them.
- Our modern concrete structures do things that would have been considered witchcraft to a Roman civil engineer. Consider the width of unsupported spans on modern concrete bridges compared to the tightly packed archways of Roman aqueducts.
None of this is to detract from Roman ingenuity, but to make the claim that Roman concrete was objectively better than what we have today is farcical.
And to add a platitude: “Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.”
Though it's important to note that factors of safety are always incorporated into structural designs, in case higher loads/wear/etc than expected occur
Thank you. This is a part of the whole trad mess, where they basically claim that everything was better for reasons and we should all turn back to the traditional values like bigotry and slavery. A fun mess where I lose my shit with anger - your answer is wonderful.
This article is literally about doing research to better understand the chemistry behind the self healing properties of Roman concrete to maybe use the findings to improve modern concrete. This is the aspect which I find so interesting : the chemistry. Literally no one is talking about going back to traditional values and blah blah. That's something which I personally abhor. Did you even read the article? Where did you find this in the article? Of course titles of articles tend to be over dramatic.
We know about thw chemistry and we know it's not compatible with rebar. So it's just a bunch of wank, ooh the good old times etc
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This article is about research on self healing properties of Roman concrete. It's not all about a one on one comparison. The chemistry behind the self healing properties is interesting and not definitively established.