Why was Roman concrete so durable?

https://news.mit.edu/2023/roman-concrete-durability-lime-casts-0106

by geox • 4 years ago

627 259 4 years ago

news.mit.edu

legitster• 4 years ago

Chemistry might be important, but we don't necessarily need that deep of an analysis.

Romans didn't mind over-engineering with massive, inefficient structures. They didn't worry about complex/thin shapes, or any tensile elements. No rebar, no "piping" cement, etc. And they could put up with extremely long cure times.

The end result is very, very dense concrete.

We could probably recreate the durability of their concrete if we were actually willing to put up with the compromises they represent.

https://practical.engineering/blog/2019/3/9/was-roman-concre...

teilo• 4 years ago

We do need a deep analysis. Roman concrete is self-healing, and this article explains why. And the reason is exactly the opposite of the one you postulate.

NegativeLatency• 4 years ago

Sounds like the chemistry is important

Previously disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials, the new study suggests that these tiny lime clasts gave the concrete a previously unrecognized self-healing capability.
As soon as tiny cracks start to form within the concrete, they can preferentially travel through the high-surface-area lime clasts. This material can then react with water, creating a calcium-saturated solution, which can recrystallize as calcium carbonate and quickly fill the crack, or react with pozzolanic materials to further strengthen the composite material.

trynewideas3• 4 years ago

https://www.science.org/doi/10.1126/sciadv.add1602

... evidence that the Romans employed hot mixing, using quicklime in conjunction with, or instead of, slaked lime, to create an environment where high surface area aggregate-scale lime clasts are retained within the mortar matrix. Inspired by these findings, we propose that these macroscopic inclusions might serve as critical sources of reactive calcium for long-term pore and crack-filling or post-pozzolanic reactivity within the cementitious constructs. The subsequent development and testing of modern lime clast–containing cementitious mixtures demonstrate their self-healing potential ...

Or, this study finds that Roman concrete regenerated using water-reactive calcium carbonate introduced through hot mixing–transformed lime clasts. This included observations of Roman concrete used in structures that weren't characteristically massive or inefficient, and reproducible in reformulated modern concrete.

In the present study, we demonstrate the calcium enrichment of matrix phases adjacent to the lime clasts, supporting the hypothesis that the lime clasts are a source of calcium for leaching and recrystallization within the pore space of the mortars. Microcrack filling by calcite has been recently observed in ancient Roman mortars from the tomb of Caecilia Metella (29), and the self-healing tests carried out on our modern samples described in the present study further support this hypothesis.

marcosdumay2• 4 years ago

Interestingly, the article founds out that their concrete cured quickly.

Anyway, no, our usual concrete completely breaks down in a few centuries. No matter how it's structured, it does not match the durability of that concrete without ongoing maintenance.

samstave2• 4 years ago

>A few centuries

Sounds good to me?

Although, many centuries old sound structures also sounds better to me...

gerdesj• 4 years ago

"Chemistry might be important"

Conc is nearly all about chemistry. You mention curing rather than drying so you surely have some idea about what is going on. The Romans did not have electron microscopes so could not watch the way the matrix develops around the aggregate etc etc from the get go. To be fair, I fried my first sample in the beam at college by over focussing.

They didn't use rebar because they generally built in compression - arches etc. Rebar and pre-stressing enables members to cope much better under tension. A PS beam or slab is a modern marvel and even protects the steel from fire - bonus.

Cure times: weather/environment. In hot climes you need to stop the water buggering off the surface and leaving cracked and spalling surfaces before it even cures. It may also over heat (exothermic reaction). Cold - slower curing, too cold - no cure and frozen water (total disaster). Underwater - watch your fines wandering off and going for a smoke behind a reef and your structure collapsing, unless you keep them in place.

Concrete curing is not like smoking a joint of meat! A quick or slow cure may be indicated depending on conditions. We have admixtures and all sorts to fiddle with parameters. Then you have things like grading and composing your agg. and other exciting stuff.

I could go on at some length - it is really, really complicated. Roman engineers managed to invent an ancient wonder of chemistry and physics that was concrete. Their approach to its use and improvements was obviously rather better than what passed for science and medicine at the time! They do seem to have experimented and gone with what worked best but it was never deliberately developed from first principles. The self healing thing was probably a happy accident.

A Roman engineer had some rather different design constraints than a modern Civil. For starters, failure could quite legitimately be blamed on the god's displeasure. "When that bridge was commissioned, we made all the correct sacrifices and anyway, you are holding it wrong, I mean walking on it incorrectly".

(sp)

UncleEntity2• 4 years ago

Roman engineers managed to invent an ancient wonder of chemistry and physics that was concrete.

Technically, the ancient Egyptians used concrete in construction long before the Roman engineers were a thing. The difference is they used it for mundane things like wine cellars while the Romans integrated it into their whole architecture system.

Once in a while that art history degree comes in handy…

Spooky23• 4 years ago

I worked on a campus where they were building a building that had to be incredibly stable - they had to coordinate arrivals of like 30 trucks making 4-5 trips a day. Each truck had like 180 seconds to unload.

Because of the coordination requirements, they embedded sensors in the structure and adjusted the water for curing and would slow down or speed up the flow of trucks based on how the process went.

One of the engineers told me that a thousand years from now, someone would wonder why this slab is here. I’m sure he was mostly kidding, but it seemed believable.

_0w8t• 4 years ago

In Ancient Rome blaming gods was never an excuse. For example, there an architect or a chief builder had to spent several nights under the bridge after its opening. In general they followed a rule similar to one in ancient Babylon which explicitly required to put the architect to dearth if a building collapse would kill the owner. And if the collapse would kill a son of the owner, then the son of the architect would be put to death.

That puts rather different perspective on the quality and longevity.

knodi123• 4 years ago

"Anyone can create a bridge that will hold up under a maximum load. It takes a real engineer to create a bridge that barely holds up under a maximum load."

sph• 4 years ago

It takes an accountant with a tight budget, you mean. Engineers will tend to make the most durable thing ever, if given enough time and money.

User232• 4 years ago

Yeah, I can't imagine a municipality letting their concrete roads cure for a couple years before letting cars on them.

interfixus• 4 years ago

massive, inefficient structures

How does a building, an aqueduct, or a bridge still in use after 2000 years manage to be inefficient?

egberts1• 4 years ago

Now onward to replacing the roads and bridges on freeways and highways with these new concrete.

insane_dreamer6• 4 years ago

cobblestones for the roads

jcadam• 4 years ago

That is... not a smooth ride.

naikrovek6• 4 years ago

for slow neighborhood roads I see no reason why brick isn't used more often. my hometown had brick roads everywhere and once every 3-5 years a few bricks would get replaced here and there. in the 1990s I'd look around and see a lot of the bricks on those roads that were made in the 1930s, and there were probably older bricks to be found if I'd looked harder.

the rough ride kept speeding down a lot more than the police could, because I watched people scream through my neighborhood all the time after they paved over the bricks.

plowing snow is harder on brick roads, but it isn't so hard that it is an unsolvable problem.

Retric• 4 years ago

Modern roads are designed to take serious abuse. 50 years of load cycling 20 ton semi at highway speeds causes mechanical damage which Roman concrete wouldn’t be effective in preventing. In ancient sites you can sometimes see the walls in high traffic areas have gotten smoothed and indented from hundreds of years worth of people gently dragging their fingertips across the surface as they walk by, tires are less gentile.

Also, people vastly underestimate how cheap road surfaces need to be. Try and calculate the volume of material making up the US road system.

magicpin• 4 years ago

A fun exercise is to calcualte the cost of some road in a neighboorhood, and compare that to the total collected property tax of all the homes along that road.

JanSolo• 4 years ago

I live in Montreal; many of the concrete structures in my city are crumbling and decaying due to the constant freeze/thaw temperature cycling that they're exposed to. I wonder if the self-healing property of this new advanced concrete would help to avoid some of the cracking & flaking we're seeing in constructions from the 60s & 70s.

naikrovek6• 4 years ago

modern roads and bridges are designed to decay at the rate they decay, because building in longevity is far more expensive than simply replacing the road surface or replacing the bridge at the end of its life.

what we don't do today is follow through on the maintenance and replacement schedules, in an attempt to save money. we try to repeat our tradeoff after the infrastructure is built, again trading away longevity in favor of money. well, infrastructure decays if you don't maintain it or build it to last longer.

skimping on maintenance after you skimped on longevity is trying to eat the cake, and still have it after you've eaten it. it doesn't work that way.

cjohnson318• 4 years ago

I worked at a geo-polymer start-up. One huge hurdle is sourcing the right kind of ash, and other ingredients, in sufficient quantities and with the right level of quality. Building a kiln or a launch pad is one thing, but building a road is orders of magnitude more expensive. Like, it's humanly possible, but it's not economically possible.

AlexandrB• 4 years ago

Only some bridge designs can use un-reinforced concrete. Many (most?) modern bridges need reinforced concrete to allow the concrete to bear tensile loads. Reinforcing concrete introduces new ways that concrete can degrade such as rusting of the reinforcing elements. I'm not really sure Roman concrete would be much help here.

marcosdumay2• 4 years ago

The quick cure may be very useful for most construction. And the self-healing may be better enough for use on pavement.

But most bridges and highways are quite demanding and can't simply adopt a new concrete chemistry based on an improvement in a single dimension.

naikrovek6• 4 years ago

the article talks about evidence which has always been present in evaluations of Roman concrete which was "disregarded as merely evidence of sloppy mixing practices, or poor-quality raw materials," and this kind of thing REALLY infuriates me, as a layman.

if you don't know how to make Roman concrete, don't assume anything about what you see in Roman concrete while you're trying to figure out how it was made.

The modern-day belief that we are superior to humans thousands of years ago is just an absolutely insane idea, to me. we are more technologically advanced because we have more shoulders of giants to stand on, and we are NOT smarter or more clever than humans of 5000-10000 years ago. we just aren't.

as soon as you believe that we are superior to our ancestors, you dismiss the evidence you are looking for as "sloppy mixing practices, or poor-quality raw materials" and you prove modern-day humans as inferior, or at least you prove your own efforts as careless and incomplete.

leave no stone unturned when you are trying to understand something you do not understand; your lack of understanding could be due to your false assumptions.

sogen• 4 years ago

An extremely good example of Chesterton’s fence?

sarchertech2• 4 years ago

That depends on the what you mean by smarter. At least some component of what we consider intelligence is cultural.

Just one example is that the ability to write/draw allows you to solve problems that are impossible without it.

HPsquared2• 4 years ago

Being literate definitely means some faculties get less practice. Practically nobody today can recite epic poetry like the Odyssey, for example. That lack of rote memorization skill may have unexpected side-effects.

https://daily.jstor.org/how-do-we-know-that-epic-poems-were-...

trynewideas3• 4 years ago

From the study:

In addition to the features described above, aggregate-scale relict lime clasts, also referred to as remnant lime or lime lumps, are a ubiquitous and conspicuous feature of both architectural and maritime Roman concretes. The presence of these distinctive bright white features has been previously attributed to several scenarios including incomplete or over-burning during the calcining of lime (20), carbonation before concrete preparation (30), incomplete dissolution during setting (12), or insufficient mixing of the mortar (14).

20: https://www.sciencedirect.com/science/article/abs/pii/S00088...

30: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1475-4754....

12: https://www.amazon.com/Building-Eternity-Technology-Concrete...

14: https://www.cambridge.org/core/journals/journal-of-roman-arc...

spacemark• 4 years ago

I agree with the spirit of what you're saying but you go too far, ironically asserting without any supporting logic that the intelligence of homo sapiens has remained static for the last 2,000 years. But I suppose the disagreement hinges on what is meant by intelligence.

Here's a thought experiment: if you removed all technology (tools, writing, vast stores of knowledge) from a human child and raised them in this vacuum, would they be more or less intelligent? Would they understand their place in the solar system and the structure of the cosmos? Would they know how to protect themselves from sickness (germ theory)? Would their vocabulary and ability to express themselves be less or more?

Of course these questions don't have definitive answers and you can play the game the other way, arguing that modern humans would die in a couple weeks if transported back to caveman times.

But it's a poor model to view intelligence as some static property independent of technology, environment, gene mutation, sexual selection and all the other strings in the web of existence.

naikrovek6• 4 years ago

"intelligence," as I used it, is the ability to learn, to use what you've learned to solve problems, and to accurately predict the future outcomes of today's decisions.

my knowledge of the horsehead nebula has no positive or negative effect on my ability to learn how to make concrete or to use that knowledge to actually make thae concrete. intelligence is not simple memorization of fact, it is a collection of understanding, and the ability to both grow that understanding and to use it to accomplish things that you don't yet know how to do.

we are continuously surprised by what we learn about ancient cultures, because we assume they were intellectually inferior to us.

the Lycurgus Cup is a great example of something that some people still view as a lucky accident. Anyone who has actually learned to make physical things and worked to refine their skill in making things will know in their soul that the colors in that cup are clearly intentional and the product of intelligence and time.

our belief that only contemporary humans have control over and understanding of the their world is just simply wrong, I think.

we discover new evidence from ancient civilizations which surprise us all the time. is there enough evidence to prove that we aren't smarter than people 100-200 generations ago? I don't know.

there certainly is a lot of evidence that ancient civilizations knew more than we believe they knew, and that is significant when you think about how long that evidence needs to last to be discovered today, and that those things which do last long enough are recognized for what they are before they are discarded because of a bad assumption. how much evidence has been lost? we only see a tiny fraction of the evidence that would have existed at the time.

these discoveries happen frequently enough for me to have no problem believing that there is a great deal about ancient civilizations that we think we know which we actually do not know.

that's a rambly comment but it's all I have time for before the edit window closes.

c7b• 4 years ago

if you don't know how to make Roman concrete, don't assume anything

That's not useful guidance for doing research at all. It's similar to some 19th-century physicists/philosophers saying 'if you can't see atoms, you can't possibly know anything about them or whether they even exist'. We also can't make supernovae or supermassive black holes, yet we can still try to learn about them through a combination of available data and educated 'assumptions' (ie theories).

What this research has done is replace one theory with another, and that theory might be replaced by another one later, that's just how science works.

naikrovek6• 4 years ago

eh, I disagree.

hypothesizing that atoms exist allows and encourages you to design experiments which can prove or disprove their existence.

assuming that they exist, and never experimentally verifying that is not research and it is not science.

assuming that some feature of a product that you do not understand exists for any reason is at most an hypothesis, and dismissing the hypothesis without experimental evidence disproving it is simply bad science.

Roman concrete is not something far away that we can not interact with. we can verify by experiment. for years we chose not to validate the assumption that the white specs were accidental, and that delayed our understanding of Roman concrete.

I just want scientists and historians that take the time to recognize their assumptions and to prove them correct or incorrect, if possible, instead of just relying on them as immutable facts; assumptions are often wrong.

I write software for a living, and the number of times that my assumptions about the cause of any particular problem have been correct approximately 0% of the time. whether it's a logic bug or a performance problem or a usability problem. despite decades of experience in this field, I am still almost always wrong about the cause of any particular problem I encounter, unless I have seen that exact same issue previously, which is rare.

historians, some of them at least, would probably benefit quite a bit from making fewer assumptions and by experimentally proving the assumptions they do make. if it isn't possible to prove or disprove your assumption, then you must never forget that it is an assumption and not proven fact.

I've seen so many scientists and historians say they know things which they simply do not know. things like "we know dark matter exists." no, we don't. we know that the currently accepted theories of our observations require dark matter to exist in order for our observations to make sense. that is not proof of dark matter.

dark matter may exist! I don't know, but for a scientist to say that it exists is incorrect because we've never observed it directly, and have devised no tests which can prove that it does exist.

our theories which require it in order for our observations to make sense could be wrong. our observations may not be as accurate as we assume. we may be observing things that we aren't aware of which look like something that we are aware of. etc.

I'm saying that professing that you know something without proof is folly. just like the white specs in the concrete were assumed to be accidental impurity without that hypothesis being proven is folly. these things set us back as a scientific community that wants to understand its environment.

insane_dreamer6• 4 years ago

modern-day belief that we are superior to humans thousands of years ago is just an absolutely insane idea, to me

totally agree that kneejerk response when we see something that doesn't match our current methods is "those people didn't know what they were doing" is both potentially incorrect and certainly unhelpful to the advancement of science

adrian_b• 4 years ago

The research paper:

https://www.science.org/doi/10.1126/sciadv.add1602

adolph• 4 years ago

One method to reduce cement’s carbon footprint (which accounts for up to 8% of total global greenhouse gas emissions), is to improve the longevity of concrete through the incorporation of self-healing functionalities. The resulting extended use life, combined with a reduction in the need for extensive repair, could thus reduce the environmental impact and improve the economic life cycle of modern cementitious constructs.

I wonder:

How much of an environmental impact this would make given the number of structures that are not useful before the concrete requires repair?

How much of Roman concrete's reputation for durability comes from survivorship bias--the structures that lasted were just lucky?

mitthrowaway22• 4 years ago

Survivor bias comes up every time this topic is mentioned, but it really has less explanatory power than most people think. If you meet a man born in 1932 who is still running marathons and doesn't need glasses, it's probably luck, although he might have some valuable diet tips to share. If you meet a man born in 1732 running the same marathon, it's time to rule out luck, and start collecting blood samples because he might actually be some kind of vampire.

Furthermore, the "survivor bias" idea, as an attempt to explain the longevity of Roman concrete as a building material, implies that the buildings that survived were stronger than the ones that did not, so we're just seeing the upper end of structural strength. But that's not even necessarily the case. Many more were lost because they were deliberately demolished for other reasons (honoring the wrong gods, etc). And it's not like these buildings only survived in ideal environments for preservation; as the article mentions, they have survived in many different climates across a vast empire, standing in seawater, through earthquakes, and so on.

ryanwinchester• 4 years ago

if we built these aquaducts now using common concrete, without steel reinforcement, they'd be in shambles in a few years.

amai2• 4 years ago

One method to refuce cement‘s carbon footprint…

…is to simply use less concrete by making it much stronger.

Very promising in that respect is https://en.wikipedia.org/wiki/Textile-reinforced_concrete#Su...

Especially carbon concrete can be up to 4 times stronger than steel concrete, so one can reduce the amount of material necessary by 4 times.

asah• 4 years ago

very exciting! and I imagine there will be follow-on work delivering even greater results.

There's also an interesting finance project here, to integrate the impact of this material into projects budgets, so that designers and investors can justify this material over cheaper alternatives. In particular, different construction projects have very different expected lifespans.

HPsquared2• 4 years ago

I wonder if it could have relevance for nuclear waste installations.

colechristensen• 4 years ago

Tl;dr:

Old “riddle solved”: Romans used volcanic ash as an ingredient

New “riddle solved”: the good stuff also includes tiny lumps of calcium carbonate that self heal cracks

georgyo2• 4 years ago

the good stuff also includes tiny lumps of calcium carbonate that self heal cracks

According the article, they didn't use calcium carbonate directly. They use quicklime (Calcium oxide) which must be mixed in at very hot temperatures.

When a crack forms, that stuff melts and forms calcium carbonate that seals the crack.

taetaset• 4 years ago

which must be mixed in at very hot temperatures

It gets hot when you mix it.

johnohara2• 4 years ago

Disappointed that this article didn't at least give a "tip of the hat" to the dogged research done by Dr. Marie Jackson, et.al., over her career at multiple universities.

Here is an excellent read on this subject from 2013: https://cedar.wwu.edu/geology_facpubs/75/

urthor2• 4 years ago

Says a lot doesn't it.

Marie Jackson makes it into the citations twelve times.

Otherwise not mentioned by name.

Academia:

You thought capitalists were greedy for mere money? Come meet academics.

next_xibalba• 4 years ago

Agreed. But is this not an example of a fundamental attribution error? The structure and incentives of academia creates all the credit grabbing and back stabbing (IMO).

https://en.wikipedia.org/wiki/Fundamental_attribution_error

trynewideas3• 4 years ago

The lead author of this study, Linda M. Seymour, worked with Jackson on reference 29, on the mortar of the Tomb of Caecilia Metella, which is referenced repeatedly and the samples from which form a significant part of the hypothesis.

That study: https://ceramics.onlinelibrary.wiley.com/doi/10.1111/jace.18...

Story on that study: https://als.lbl.gov/unexpected-transformations-reinforce-rom...

Jackson is quoted, if briefly, by Science's article on the new paper. https://www.science.org/content/article/scientists-may-have-...

Jackson's work is focused on pyroclastic volcanism. Seymour's work has focused on Roman water infrastructure.

Jackson works for the University of Utah, Seymour works for MIT. The linked source is MIT's PR department.

w1nst0nsm1th• 4 years ago

Dawn, I just wanted to patent it.

nimbius• 4 years ago

on the other end of the spectrum, did you know concrete can be used to demolish concrete?

dexpan is a special demolition concrete mix that, when poured into holes, expands at 18kpsi. it gets used when jackhammers and explosives cant be used, for example, in refineries and explosive atmospheres.

hinkley4• 4 years ago

Presumably dexpan has lower tensile strength so it can be disposed of easily? Or is the piece excavated and hauled away intact?

barathr2• 4 years ago

It expands in the holes you make in the to-be-destroyed concrete, cracking it. You can haul it off in chunks at that point.

barathr2• 4 years ago

It's also useful if you want to do concrete demolition yourself using only hand tools. You drill holes, pour, wait for cracks, and then use a pick and hammer to remove the remaining chunks. Often sold as "expansive grout".

dsfyu404ed2• 4 years ago

If you can drill holes you can use stone splitting wedges.

A lot of these high dollar modern miracles of chemical engineering are purely for use in situations where it's cheaper to just buy the $100/tube stuff than it is to try and get the approval to do something sensible. Basically you're paying to get around process tech debt.

swayvil• 4 years ago

I've used that. Drill holes. Fill holes with gunk. Come back in the morning and the concrete is all cracked up. Silent and easy. Works great.

amelius• 4 years ago

Won't it expand out of the holes you poured it into?

Jensson• 4 years ago

Not if it hardens before it expands.

jaclaz• 4 years ago

In some cases (particulary with modern, faster, formulations) it can, actually projecting (powder/smoke) out of the holes but it is not usually an issue.

When it happens is because the expansion is too fast (and consumes all the water available), making the grout itself fragile, with slower formulas, after the initial setting of the grout, you should water/keep the surface wet.

It is surprisingly difficult to find actual videos of it working (most are just a set of photos) because it is very, very slow (between 6 and 48 hours, usually), here is one from one of the many producers:

https://www.youtube.com/watch?v=CYAcHc9rP9o

dang• 4 years ago

Why Ancient Roman Concrete Outlasts Our Own (2017) - https://news.ycombinator.com/item?id=29366911 - Nov 2021 (67 comments)

2,050-year-old Roman tomb offers insights on ancient concrete resilience - https://news.ycombinator.com/item?id=28833525 - Oct 2021 (101 comments)

Why Roman concrete is stronger than it ever was, while modern concrete decays - https://news.ycombinator.com/item?id=25690803 - Jan 2021 (7 comments)

A chemical reaction in ancient Roman concrete makes it stronger over time (2017) - https://news.ycombinator.com/item?id=22580920 - March 2020 (64 comments)

How Ancient Rome’s Concrete Has Survived 2,000 Years (2017) - https://news.ycombinator.com/item?id=20482050 - July 2019 (81 comments)

How Did the Romans Make Concrete That Lasts Longer Than Modern Concrete? - https://news.ycombinator.com/item?id=15544128 - Oct 2017 (3 comments)

The Rock Solid History of Concrete - https://news.ycombinator.com/item?id=15480165 - Oct 2017 (12 comments)

Why Roman concrete still stands strong while modern version decays - https://news.ycombinator.com/item?id=14699652 - July 2017 (1 comment)

Ancient Romans made world’s ‘most durable’ concrete - https://news.ycombinator.com/item?id=14695876 - July 2017 (4 comments)

New studies of ancient concrete could teach us to do as the Romans did - https://news.ycombinator.com/item?id=14690329 - July 2017 (72 comments)

Ancient Roman Concrete Is About to Revolutionize Modern Architecture - https://news.ycombinator.com/item?id=5883443 - June 2013 (23 comments)

How the pantheon has lasted 2000 years without steel in its concrete - https://news.ycombinator.com/item?id=1852000 - Oct 2010 (35 comments)

Also:

The problem with reinforced concrete (2016) - https://news.ycombinator.com/item?id=27282927 - May 2021 (186 comments)

The problem with reinforced concrete - https://news.ycombinator.com/item?id=11975695 - June 2016 (147 comments)

jonnycomputer• 4 years ago

our obsession with Roman concrete.

russellbeattie• 4 years ago

I was thinking as I read this, "Wait, don't we already know this?" Now I know why.

twelve40• 4 years ago

following all of the detailed recipes that had been optimized over the course of many centuries

i wonder how all those detailed recipes were passed around for many centuries and now all is gone. Was it all passed down verbally?

eole666• 4 years ago

In the 6th century, big volcanic eruptions, low temperatures and plagues bringed a dark age in Europe and other parts of the world. A large part of the population died. Maybe those recipes were lost during this period.

dreen2• 4 years ago

I don't think the knowledge is gone, we could make that or maybe even better. The point is nobody wants it, most things we build need to be torn down after at most a few decades anyway.

ricardobeat3• 4 years ago

The knowledge is actually gone, like Damascus Steel (what we have today is just a visual reproduction) and Greek Fire.

For a more recent example: we already "forgot" how to make the spaceships and rockets that went to the moon. Even if you had the full plans - and apparently we don't, a lot of the materials and processes are not around anymore and would have to be 'reinvented'.

mitthrowaway22• 4 years ago

So why didn't the researchers just ask one of the people who knows how it's made, instead of wasting all this time conducting tests and doing spectroscopy?

coryrc• 4 years ago

Some of it was "stone from this volcano" and then it was mined out. They didn't know how to choose a substitute.

Toutouxc• 4 years ago

This is from the article:

Masic wondered: “Was it possible that the Romans might have actually directly used lime in its more reactive form, known as quicklime?”

And this is from Wikipedia, with the source dated 2011:

Gypsum and quicklime were used as binders. Volcanic dusts, called pozzolana or "pit sand", were favored where they could be obtained

Is it just me or are popular science articles really so simplified that they often completely misrepresent the point of the research?

sebmellen• 4 years ago

Gell-Mann Amnesia is real.

kazinator• 4 years ago

Roman concrete was durable mainly because they didn't yet hit upon that silly idea of adding steel rebar.

rootusrootus• 4 years ago

How does this concrete compare to a state-of-the-art mix -- not just the stuff they use to pour my driveway or the highway, but the best we know how to make?

devoutsalsa• 4 years ago

Practical Engineering can answer all your questions with their series on concrete. It’s extremely well done, including a video on “Was Roman Concrete Better?”:

https://youtube.com/playlist?list=PLTZM4MrZKfW90PdaBFt70BLTb...

ogogmad• 4 years ago

For people who don't know the difference between cement, mortar and concrete:

Cement is a substance used for producing mortar and concrete. It's never used on its own. It is a "binding agent". Note that the term "cement" is often not used correctly in everyday speech, with people talking about gluing bricks together with cement, when bricks are actually glued together with mortar.

Mortar is the glue between bricks. You can see it between the bricks in any brick wall. It is produced by mixing cement with sand. This results in a paste which hardens after being applied to a brick.

Concrete is a substance that can be put into any shape, and then hardens. The bricks in a brick wall can be made from it. (More examples?) It is produced by mixing cement with sand and gravel (which are larger rocks).

There is also reinforced concrete, which the Romans didn't have. While concrete by itself can in principle be moulded into any shape, this can sometimes fall apart after hardening. Reinforcement refers to putting the concrete around metal wiring, which allows for more versatile shapes while maintaining stability.

Feel free to provide corrections.

ggm4• 4 years ago

Reinforced concrete in part is designed to provide structural strength under tension forces. Concrete is stable in compression but has weak resistance to tension. Pretensioned reinforced concrete permits longer unsupported spans but even vertical concrete can benefit from reinforced bars, to prevent spalling. (I believe). Not all reinforcing steel has to be tensioned to be useful, that's a technique for long spans.

Reinforced steel bars hence rebar.

LegitShady8• 4 years ago

Reinforced steel bars hence rebar.

More like reinforcing bars, rather than reinforced bars. And technically the overwhelming majority of what is sold today are actually deformed reinforcing bars, since the intentional addition of ridges on the outside of the bar helps the concrete adhere as compared to smooth mild steel.

ComputerGuru• 4 years ago

but even vertical concrete can benefit from reinforced bars, to prevent spalling. (I believe).

I liked your comment but this bears correcting. (Corrosion of) rebar is actually the biggest cause of spalling in vertical concrete structures.

sambeau• 4 years ago

Though most concrete is reinforced with steel rebar, it can be reinforced with all sorts of other materials to strengthen it under different conditions & loads: glass rods, plastic meshes, fibres, carbon nanotubes, etc.

LegitShady8• 4 years ago

There is also reinforced concrete, which the Romans didn't have. While concrete by itself can in principle be moulded into any shape, this can sometimes fall apart, even after hardening. Reinforcement refers to putting a concrete around metal wiring, providing more versatility.

Not a correction per se, but some further explanation.

The reason for reinforcement is because concrete is strong in compression and weak in tension - in fact for design purposes we disregard its tensile capacity entirely. What reinforcement does is handle the tensile stresses in a structural member. When a beam, column, or slab bends it often (based on the load placed and structural design) creates tension on one side and compression on the other, so we put the rebar in the structural member close to the tension side, or on both sides if there may be tension on both sides.

In slabs reinforcing may also be used in some capacity just to limit cracking in an otherwise non structural capacity. In certain kinds of designs it may also provide confinement to the concrete which can be important for structural analysis reasons that are too technical to get into here (plastic hinging especially in earthquake design, etc).

We have different kinds of reinforcement, depending on the need of the project, but for the most part we use steel because its reasonably durable, has similar temperature expansion properties to concrete (imagine if your concrete got cold and shrunk more than things embedded in it, or grew so much the things embedded in it weren't attached anymore), its behaviour is well understood, and it is reasonably priced.

The design of steel reinforcing in concrete is also done in a way that reduces the likelihood of sudden failures, so that if something does happen, it happens slowly and with plenty of warning.

There are alternative reinforcing materials that may be appropriate in some very specific situations, but civil engineering moves very slowly and adoption is slow because risk is high. Fiber Reinforced Polymer (FRP) and Glass Reinforced Plastic (GRP) are examples of these. They may have much higher tensile stress capacity per unit of area, and also are less susceptible to corrosion, but they cost a lot, their failure modes are sudden, greater deflections under load, and each may have other tradeoffs like worse compressive behaviour, or worse fire resistance, etc.

Animats• 4 years ago

There's a small trend towards stainless steel rebar. It's expensive, but is now used for concrete structures near salt water.

Epoxy coated rebar turned out to be a mistake. One scrape in the epoxy and it starts rusting. Exposure to UV prior to installation can damage the epoxy coating. Currently banned in Quebec.[1]

[1] https://news.ycombinator.com/item?id=27676447

jhallenworld• 4 years ago

There are different types of cement: Portland and CSA (Calcium Sulfoaluminate).

https://caltra.com/wp/wp-content/uploads/2016/11/What-is-CSA...

Portand is the cheap stuff- like the $6 Quikrete bag at Home Depot. CSA is more expensive, but also available at Home Depot- look for the "Rapid Set" brand (Rapid Set Cement All is like $28 a bag).

It's kind of awesome, it's so fast you can sculpt vertically with it. You use more water with it than Portland, it starts out more mud-like. It tends to be preferred for repairs.

https://www.youtube.com/watch?v=XO8wyQfjpt4

https://www.youtube.com/watch?v=kaB22ceIrqk

aidenn02• 4 years ago

There are many, many, types of cement. Another common type of cement that people are probably familiar with is asphalt (a.k.a bitumen).

hbarka• 4 years ago

Breaking down cement further, the raw materials are limestone, clay, and touch of iron ore (“red earth”).

dima_vm2• 4 years ago

Well, technically, you can use cement instead of mortar (wet, but without sand). As far as I understand, sand is more like a neutral filler, to save money on cement. Various other things can be used to fill as well, like gravel. Sometimes even empty plastic bottles (reduces material and weight) are suitable (just make sure they don't float up). If one got very smooth bricks (e.g. precisely cut aerated concrete), then it might make sense, as there's very tiny amount of mortar (or even glue) is needed anyway.

IIsi50MHz• 4 years ago

If the sand is properly coarse, it can add strength. However, finding coarse sand is increasingly difficult, resulting in misuse of smooth sand (from error or being defrauded).

Tangent: coarse sand is also important for certain types of septic systems to function properly.

jacquesm4• 4 years ago

The baths of Caracalla (sp?) had concrete reinforced with copper!

olau• 4 years ago

The bricks in a brick wall can be made from it.

I think "brick wall" usually refers to fired clay blocks:

https://en.wikipedia.org/wiki/Brick

But yeah, you can make concrete blocks and build stuff with those. They are usually larger than clay bricks. In my country, the stuff used for building is mostly concrete bricks filled with small air bubbles air so that it is lighter and also insulates better.

duckmysick• 4 years ago

This type is called autoclaved aerated concrete.

https://en.wikipedia.org/wiki/Autoclaved_aerated_concrete

It's pretty good but it's also brittle. You have to use special screws and wall plugs if you want to attach something.

ggm4• 4 years ago

Cannot recommend enough "the new science of strong materials: or, why you don't fall through the floor" by JE Gordon. Old, but amazing.

FairDune• 4 years ago

Thanks for the suggestion

nkurz• 4 years ago

The formatting is a little off, but a fully text PDF is here: https://edisciplinas.usp.br/pluginfile.php/3975708/mod_resou...

jesuspiece• 4 years ago

It is a testament to the ingenuity and expertise of the ancient Roman engineers. It will be interesting to see what other insights this research may lead to and how it could potentially be applied to modern construction techniques.

I_complete_me• 4 years ago

The subject is complicated. For example see this paper[0]. The setting of concrete goes on for a long time and the Romans were probably not aware of how long their concrete(s) was/were going to last. There is a type of 'survivorship bias' going on here. But still, I guess, they knew something important. Adding reinforcement to concrete may well be a source of shortevity - or what ever the complement to longevity is.

[0] https://www.sciencedirect.com/science/article/abs/pii/S00225...

UncleEntity2• 4 years ago

It’s not like the Romans started out in a place where there weren’t thousands of years old structures nearly everywhere they went.

Assuming they didn’t want their structures to last as long as the ancient ones (at their time) is just laughable.

akolbe• 4 years ago

Here is a nice picture of the Pantheon, mentioned in the article as a prime example of these incredibly durable Roman concrete structures:

https://commons.wikimedia.org/wiki/File:Pantheon11111.jpg#/m...

Not bad for something built nearly 2,000 years ago.

insane_dreamer6• 4 years ago

I wonder what percentage of the original stones are left (given that it was repaired and restored over the centuries)

ggm4• 4 years ago

I don't believe the dome structure was radically altered across time. It's possible I misunderstood but my belief was it was only cosmetic changes to the dome itself. Other structural changes were made to the portico and doorways.

helloworld11• 4 years ago

Unlike many ancient structures, the Pantheon has mostly been left intact across the millennia. The Dome is entirely original and so is most of the remaining structure. From what I know, the majority of the restoration and renovation work has been to the interior ground-level walls and some of the exterior along the ground level, but even these are mostly minor renovations. In this case, what you see truly is for the most part what always was, and especially for the main awe-inspiring part, the great dome.

Bayart• 4 years ago

The Pantheon is very notable among Roman monuments for having little done over the years other than cosmetic upgrades.

peoplefromibiza2• 4 years ago

of the original Pantheon from 27 B.C. very little remained.

It was rebuilt after the fires of 80 A.C. and 110 A.C. damaged the original structure.

It's been mostly unchanged after that.

ggm4• 4 years ago

Uses pumice in aggregate as aerated mass to lighten the concrete and also varies concrete thickness by height in the dome to reduce load

galaxyLogic2• 4 years ago

And the concrete self-heals with water

Maursault• 4 years ago

Not bad for something built nearly 2,000 years ago.

According to the Pyramids, Stonehenge, Newgrange, Watson Brake, et al., it's a little premature to suggest that. Let's check back in 3,000 years.

jacquesm4• 4 years ago

Hehe, that's funny. But the OP clearly meant it relative to other stuff built 2000 years ago, most of which has vanished without leaving a trace, maybe a couple of foundation stones buried under a meter of new topsoil.

Have an upvote, it's sad to see you grayed out.

peoplefromibiza2• 4 years ago

stone != concrete

edit: we have a > 2,000 years old pyramid in Rome too, and it's in perfect shape, because stone != concrete

https://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/Ci...

GuB-42• 4 years ago

The pyramids are essentially just piles of rocks. The impressive part about them is not really how they stood out the test of time, in fact they lost most of their finer details, but how an ancient civilization managed to make piles of rocks that big.

The Pantheon is not a pile of rocks, it is made of engineered materials (concrete), with domes and overhangs. Unlike "pile of rocks" architecture that essentially can't fail, if it wasn't well engineered, it would have collapsed into something unrecognizable.

pachico2• 4 years ago

It doesn't matter how many times I see it, every time I go to Rome and find myself in front of the Pantheon, I get overwhelmed by it.

benreesman• 4 years ago

With zero sarcasm, when I read “every time I go to Rome” I feel that I took a wrong turn in life somewhere.

Fucking awesome mate.

insane_dreamer6• 4 years ago

I read the article quickly but couldn't see whether this discovery is applicable to modern concrete (in other words, could the same technique be applied to modern methods for making concrete that would make it more durable)?

novosel• 4 years ago

"To prove that this was indeed the mechanism responsible for the durability of the Roman concrete, the team produced samples of hot-mixed concrete that incorporated both ancient and modern formulations, [...] cracked them, and then ran water through the cracks. [...] Within two weeks the cracks had completely healed [...] As a result of these successful tests, the team is working to commercialize this modified cement material."

insane_dreamer6• 4 years ago

thanks

avereveard• 4 years ago

sea water + quicklime was known to be the "secret" for concrete for a while, this is a 2017 article https://www.washingtonpost.com/news/speaking-of-science/wp/2... can we put this to rest already?

ricardobeat3• 4 years ago

If you pay attention to the article, the previous theory of seawater + volcanic ash turns out to not be the main reason for it's durability. The lime clasts being a feature, not a bug, and hot mixing, are the new discoveries.

boogoob• 4 years ago

Isn't the particularly short lifespan of modern concrete construction mostly a combination of its use in areas with regular freeze-thaw cycles and using a reinforcement material that rusts (and in doing so expands, damaging more concrete and hastening further water inclusion)?

oakwhiz2• 4 years ago

The rusting and getting wet is cyclical in nature and part of what accelerates that is the formation of cracks in the first place. Part of the maintenance of concrete is to fill any cracks that you can find to prevent it from getting worse. The cracks typically start small, and they might form in places that are hard to get to as well as being too small to see, so if the concrete is self-healing it will prevent some of these small cracks from getting worse on their own which should reduce the effect of expanding water (ice) as well as expanding rust.

The reinforcement material (rebar) already has a very close thermal coefficient of expansion to concrete and this can be thought of as kind of a lucky coincidence.

masklinn2• 4 years ago

as well as expanding rust.

Ideally they’d seal before the rebar is exposed and can rust. As long as the rebar is encased, unless you fucked up dramatically it should be safe.

PicassoCTs• 4 years ago

Another method is to connect all the rebar and add a https://en.wikipedia.org/wiki/Galvanic_anode

tuatoru2• 4 years ago

expanding rust

The alkaline environment inside concrete "passivates" the reinforcing bar, greatly reducing the rate of oxidation and changing its form.

The problem exists only in concrete that is badly made with poorly chosen aggregate, and in corrosive environments.

1. https://en.wikipedia.org/wiki/Passivation_(chemistry)

prometheus76• 4 years ago

And being driven over by semi trucks full of heavy cargo 24/7.

riversflow• 4 years ago

I'm just going to throw it out there to spread the word; GFRP Rebar (Glass Fiber Reinforced Polymer) is a thing, and you can buy it today at your local hardware store. I really wish I would have known about it on my last project, probably the last time I will buy steel rebar to put in concrete.

I'm not an ME, but my understanding is that it is a comp in terms of structural reinforcement. I'd be really interested to do a deep dive on how these technologies stack up against each other, it seems like a win for construction longevity, it would be pretty cool if the ecological impact of production penciled out as a win too. My understanding is that there are some trade off when being used in large projects.

My cursory research has indicated that this stuff first hit production in the 80's and was used in a bridge in the US in 96. Still haven't figured out why it hasn't taken over.[2] Is it just for a lack of evangelists?

[1]https://www.lowes.com/pd/Owens-Corning/5013333093

[2] https://www.fiberglassrebar.us/gfrp-rebar-from-the-beginning...

iamgopal• 4 years ago

Any comparison in tensile strength?

scarier• 4 years ago

The main reason is stiffness—off the top of my head, it’s roughly a quarter as stiff as typical steel, so it needs significant engineering and often much more reinforcement to keep the concrete within allowable deformation limits. Basalt and carbon fiber are more promising replacements, but are significantly more expensive.

_jsnk• 4 years ago

I recommend Tyler Ley's youtube channel[0] entirely devoted to concrete. He has an episode[1] addressing GFRP that might interest you.

[0] https://www.youtube.com/@TylerLey

[1] https://www.youtube.com/watch?v=thUZImUTZn0

xattt• 4 years ago

Mike Holmes, a home reno personality in Canada, had been touting its benefits in about the mid-2000s for home foundation re-pours.

tuatoru2• 4 years ago

Isn't the particularly short lifespan of modern concrete construction mostly a combination of its use in areas with regular freeze-thaw cycles and using a reinforcement material that rusts

No. It's a consequence of designing to requirements of minimum cost and a 50-year lifespan. It'd be easy to make concrete with much longer lifespan, but it costs more.

raspberry1337• 4 years ago

It's a nice thought that all these depressive brutalistic/modernist builduings will all soon crumbly by the same mechanism that spawned them!

ithkuil• 4 years ago

“Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.” - Unknown

TheMagicHorsey• 4 years ago

Some day in the very far future, our descendants will ask, why is the code manually made in the 2020s with Rust so durable, while our modern PHP20457 code that is spit out by Tardpilot100 is so fragile? Our modern operating systems need to reboot 1000 times per hour just to function while ancient operating systems could stay on for months at a time without rebooting!

BirAdam• 4 years ago

Nah. Rust evangelists of the future will still be fervently rewriting everything in Rust, and they’ll be researching why ancient code worked without being written in Rust.

bachmitre• 4 years ago

It looks like ChatGPT already knew that (or I skimmed too quickly):

Why was Roman concrete so durable?

Roman concrete, also known as opus caementicium, was a highly durable construction material used by the ancient Romans for a variety of structures, including aqueducts, bridges, and buildings. There are several factors that contributed to the durability of Roman concrete:

The use of lime and pozzolanic materials: Roman concrete was made from a mixture of lime, water, and an aggregate such as sand or crushed stone. The lime was derived from the heating of limestone, which produced a highly reactive form of calcium oxide. The Romans also added a pozzolanic material, such as volcanic ash, to the mixture, which improved the durability and strength of the concrete by reacting with the lime to form a cementitious material.

The inclusion of a reinforcement material: Roman concrete was often reinforced with a material such as iron or lead, which helped to increase its structural strength and resist cracking.

The use of a hydraulic setting process: Roman concrete was able to harden underwater due to its hydraulic setting properties, which allowed it to set and cure even in the presence of water.

The construction of thick, monolithic structures: Roman concrete was often used to build thick, monolithic structures such as walls and foundations, which were able to withstand the forces of nature and resist deterioration over time.

Overall, the combination of these factors made Roman concrete a highly durable construction material that has stood the test of time.

itsthecourier• 4 years ago

Read the article, they discover they should use a particular state of lime, quicklime. That's new

dgoldstein0• 4 years ago

The inclusion of a reinforcement material: Roman concrete was often reinforced with a material such as iron or lead, which helped to increase its structural strength and resist cracking.

Sounds like chatgpt messed up it's facts? If this means reenforced like with rebar, the Romans didn't do that - and that's part of why their concrete structures lasted so long - when designed to be under compression rather than tension (arches, domes, etc)

longt1melurker• 4 years ago

they used saltwater and added volcano ash. thats the secret sauce

simonblack• 4 years ago

They didn't reinforce it with iron.

hinkley4• 4 years ago

I think the bigger question for me, and it comes up about half the time when the topic of Roman concrete comes up, is to what extent Roman concrete has a lower or higher lifetime carbon footprint than modern concrete.

Stronger concrete means either less concrete or a slower replacement schedule, and the Roman formula absorbs a certain amount of CO2 out of the air as it ages.

The second to last paragraph of this article talks about it:

Through the extended functional lifespan and the development of lighter-weight concrete forms, he hopes that these efforts could help reduce the environmental impact of cement production, which currently accounts for about 8 percent of global greenhouse gas emissions. Along with other new formulations, such as concrete that can actually absorb carbon dioxide from the air, another current research focus of the Masic lab, these improvements could help to reduce concrete’s global climate impact.

As we reach the end of the petroleum economy we are going to have a problem with making asphalt, as it is essentially diverting a waste stream from oil refining. When we only use petroleum for materials instead of setting it on fire, that's not going to be a 'free' stream of materials anymore.

ShredKazoo• 4 years ago

To prove that this was indeed the mechanism responsible for the durability of the Roman concrete, the team produced samples of hot-mixed concrete that incorporated both ancient and modern formulations, deliberately cracked them, and then ran water through the cracks. Sure enough: Within two weeks the cracks had completely healed and the water could no longer flow.

So this method wouldn't necessarily work in a dry climate without much rain?

thowei2i34234• 4 years ago

Reminds me of the Wootz Steelmaking (and much else) in classical India which was lost during the period of Anglo-Islamic colonization. Roman empire, Egypt and Greece, IMO is, contrary to current myths, is far closer in spirit to India than to anything of the 'modern West'. Indeed, the Greeks ruled parts of India for many centuries, and Rome had a great amount of trade with it.

The loss of so much rich tradition across the world due to birth of religion and its obsession with tyrannical power over everything is such a tragedy on humankind... this was recognized by the thinkers of Europe during the wee end of the 'renaissance', but in light of post-WW2 plebification of intellectuals, is being rolled back because of the current crop's moronic obsession with another religion: Marxism.

Such tragedy. tck. Such tragedy.

kaesar142• 4 years ago

What an atheist meme. These things were ‘lost’ because of breakdowns in trade networks caused by breakdowns of central authority and invasions by outside powers. If anything, the Church is what’s kept the Classics alive through its usage of Latin in the clergy and its preservation of Roman structures as churches.

ziotom782• 4 years ago

The Pantheon is a perfect example. It has survived for 2000 years because it was repurposed as a church.

ReptileMan• 4 years ago

Wootz steel was never lost. Just the contaminated with vanadium ores they used disappeared. We know quite well what happens to a carbon steel with vanadium. Most high performance steels today are made with it in the alloy.

beezlewax• 4 years ago

There is a Greek Hellenistic breakwater or port ruins in Sant Martí near L'escala in Catalonia, Spain that is sitting in the sea. It is still standing. Always amazes me that it's still there though I'm sure some minor restoration work has probably been done.

af782• 4 years ago

Relevant thread: https://twitter.com/cleptok/status/1611622181665923075

Ok. Let's do a short thread on Roman cement for the 3 people out there that might be interested. You often hear that the Romans had some sort of superior and arcane knowledge on superior cement mixes that has been now lost. And still today we cannot replicate it. This is complete nonsense. Modern day cement (and any other building material, really) is far, far superior than anything from the past. There is simply no comparison. Above everything we understand the chemical composition, interaction and quality control for consistent results.

Romans were making mortars based on volcanic ashes. There was no set recipe. Every builder had their own. Volcanic ash from Pozzuoli, crushed brick, slaked like, animal fat, hair etc. Some basic rules existed (as recorded by Vitruvius on the 10 books on Architecture).

Millions of structures were constructed these way. With the exception of a handful, most of these do not exist anymore. But why the ones that exist are still standing strong?

Usually via a simple Darwinian process. Most of these times those builders got it wrong. But in a few cases, out of luck, they got the chemistry just right. This would result in a ok-ish material, with decent properties. Not only that. Unreinforced (without steel) concrete will not suffer any serious deterioration, with few exceptions. (Pantheon in Rome) Also the very coarse pozzolan they were using, will chemically react very very slowly producing low initial strengths Vs any modern material.

In the long term (centuries) though, it will continue gaining strength. Totally useless for the original purpose of the builders, but quite good for the few surviving buildings.

So what the latest MIT research told us? That lime in very small quantities will be "self-healing'. And this somehow is something that the Romans knew and used to create a superior cement.

This is simply not true. It is well known that lime expands (the pompous "self-healing" tag), so in very small and precise quantities it will counteract the shrinkage and cracking behaviour of cement binders. But you have to be pretty lucky to get it just right.

So not intentional. Just survivor bias in the remaining Roman cement structures. Beyond this, lime is a definite no-no for any concrete with steel in it -it corrodes it. The reason we use concrete today is precisely the embedded steel. It allows to build all modern structures.

And steel is the reason modern concrete deteriorates. It corrodes, expands and cracks the surrounding concrete. An unreinforced concrete (like the ones Romans used) with modern materials and understanding would last forever. But you wouldn't build anything worthwhile.

Final. Remember. Cement = the glue, the binder that holds everything together, activated by water. Concrete= the actual building material with binder, water, sand and stones. Mortar= only binder, sand and water (maybe small stones)

amai2• 4 years ago

And the real deal is modern https://en.m.wikipedia.org/wiki/Textile-reinforced_concrete.

Especially the combination of carbon fiber and concrete is a very promising solution, which is researched in Germany: https://de.m.wikipedia.org/wiki/Carbonbeton

This stuff is superior to anything the romans did in every aspect.

imtringued4• 4 years ago

Honestly, I think a much bigger factor than random chance is the designed lifespan of these buildings. Some of them took decades or even centuries to build. So they must not only last throughout the construction process, they must also last long enough to make the construction process be worth it.

Spending a few decades on experimentally determining an optimal cement mixture is also worth it.

The by far biggest problem is that the vast majority of buildings get demolished and replaced by something else so making them long lasting is not very useful.

MayeulC• 4 years ago

That reads as somewhat misguided and dismissive. You don't have to understand the chemistry to improve recipes by trial and error, over multiple generations, and learn from the still-standing structures.

And there is still value in studying today those that survived in order to improve ours. The way lime healed cracks is new to me at least, but it's taken as a given here.

you wouldn't build anything worthwhile

You just need more cement, it could be replaced with fibers. We still use unreinforced concrete in some cases.

af782• 4 years ago

The thread seems to have been written by a Greek, a bit of Roman-bashing is par for the course :)

nazka• 4 years ago

You often hear that the Romans had some sort of superior and arcane knowledge on superior cement mixes that has been now lost. And still today we cannot replicate it. This is complete nonsense.

That’s what I heard. And that we found it recently but it wasn’t useable economically because it required an extremely long time to dry instead of modern ciment and it’s ability to dry (and so raise a building) a lot faster.

rapjr9• 4 years ago

So how difficult is it to destroy Roman concrete? If we start using it to build things are we going to be stuck with those things for 2000 years?

Why was Roman concrete so durable?

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