We Finally Know How Ancient Roman Concrete Was Able to Last Thousands of Years

floofloof@lemmy.ca to Technology@lemmy.world – 170 points – We Finally Know How Ancient Roman Concrete Was Able to Last Thousands of Years
sciencealert.com
34

Every year we seem to get an article about how we've finally discovered how Romans had really good concrete, as if we've not already known for ages.

The issue has always been about logistics, cost, time to produce, etc — not because we had no idea how the Romans did it.

This plus extreme selection bias. There's plenty of concrete that did not last for thousands of years.

"They don't make things like they used to. See that tube radio over there? It's 75 years old and still working! A rare find!"

But in their defense, not a single thing on Earth made in the last decade has lasted 75 years. Check mate.

And also fucking 16 wheelers. Romans did not drive 80 ton (made up number. I don't know how heavy big trucks are. But I'm Shure they are lighter than ancient wagons. To be honest I just hate cars and I want to use a scientific discussion to push my personal political view.) vehicles.

let me guess, the didn't fill it with iron that would corrode and expand and blow out the concrete? or the fact that it has an excess of fired lime that re-seals cracks?

You do know that rebar frames are completely essential for most concrete construction right? It's not some conspiracy to induce failure. Concrete by itself can only handle compression forces - the rebar allows it to handle tension, torsion and sheering.

I'm guessing they do, but it does also reduce the life of the concrete. Modern concrete structures would be impossible without rebar, so that makes it a good trade, but it doesn't change the fact that it's a trade.

Yep, it’s the the lime. And: “ The team is now working on commercializing their concrete as a more environmentally friendly alternative to current concretes.”

Quick lime as a 'concrete' is nothing new, or newly rediscovered though... The story seems to come up every few years, and anyone that has used a fluidised lime boiler knows how good quick lime is at forming concrete.

And, coincidentally, every time the story comes up there's a company ready to sell you the magic roman concrete.

Yeah, I was thinking it's like the "Voyager Has Left the Solar System" story - we've heard that several times over the years, and probably will again.

To be fair, we keep expanding what we class as the solar system. Poor old voyager keeps getting the goalposts moved!

The year is 76,014. Voyager still hasn't left the solar system. Also, the solar system now contains Proxima Centauri.

that'd be great, a lot of buildings are torn down just because the concrete cracks.

i'd be interested in seeing how using better concrete impacts overall costs and of course emissions. because the building ends up standing for a lot longer, the temperature isolation becomes very sub-par over time. that would increase total energy consumption compared to buildings that are frequently rebuilt.

but very promising.

Meh. Lime mortar absorbs and releases moisture. IRC "Roman" lime concrete is much the same.

Don't get me wrong, I'm a huge fan, but that kind of thing isn't compatible with modern insulation. You end up with damp and mould issues in the walls.

Sure it works great in uninsulated stuff though. But people and governments want every room in a building to be insulated nowadays. The whole one warm room, the rest of the building is cold and you'd better wear a three piece suit or heavy wool jumper thing, is abhorrent to our spoiled western arses.

Also: the Romans didn't build their buildings that high. AFAIK Lime concrete has lower tensile and compressive strength, which is an issue with high rise buildings.

Sure it works great in uninsulated stuff though. But people and governments want every room in a building to be insulated nowadays. The whole one warm room, the rest of the building is cold and you’d better wear a three piece suit or heavy wool jumper thing, is abhorrent to our spoiled western arses.

Spoken like somebody who doesn't live where rooms would be intolerably hot without insulation most of the year.

Also we only see the few structures which survived. 99%+ did not make it 2000 years.

the iron is a great way to increase tensile strength, but decreases lifespan, rust free metals would also be much nore expensive.

Epoxy covered rebar exists as does one made from stainless steel. It's just quite pricey so it's rarely used unless absolutely necessary. Rust is generally not an issue as long as the rebar is deep inside the concrete. When it's close to the surface and gets exposed to elements is when the problems start.

Wdym? Just replace the iron rebar with gold

Gold is no where near strong enough.
Titanium would work just as well, and last quite a bit longer.

Isn't titanium too rigid for this application though? I've worked with both for a mechanical application, and titanium has no flex, so stresses get passed in to other components.

I don't know, I'm no civil engineer. Any civvies wanna fill us in?

Aluminum then?

I'd say all the Civil engineers who continue to spec steel do it for well-established reasons.

Steel is just so hard to beat in so many applications. Even for the average road bicycle, surprisingly. Because steel can tolerate more flex than things like aluminum/titanium/carbon fiber. So other materials require different designs. In the end, the average street bike in steel or aluminum can often weigh the same, depending on the design choices (not specialized bikes, where different compromises are made).

Like so many things, when used as designed in concrete, steel is just fine, and I assume meets the cost, availability, industry knowledge, etc, goals.

Makes me think of "don't remove a fence until you know why it's there". Every year upcoming engineers do tests during their education. If a different material was a better choice, I'm sure a research arm of a university would present it.