Why was Roman concrete so durable?
news.mit.edu
news.mit.edu
https://commons.wikimedia.org/wiki/File:Pantheon11111.jpg#/m...
Not bad for something built nearly 2,000 years ago.
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.
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.
Have an upvote, it's sad to see you grayed out.
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...
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.
Fucking awesome mate.
Now I live in Spain and I continue to fly to Rome now and then.
In Europe, distances are easy to overcome.
Source: tried it myself.
Probably practice is needed, but your holidays are too short for that.
I was not thinking about excessive speeds or tailgating.
In Southern Italy, when you are stuck in a traffic jam in the city, you just drive nearer to other cars, and this is only mildly dangerous because you don't have high speeds.
If you don't drive tight enough, you just can't proceed because some other car will take your place.
This is not tailgating or driving recklessly.
Lots of crosses remembering dead drivers on the side of the roads too.
I was born in an East European country and I worked a few years in New York. Many people back at home react to this fact as if I made it. As if shoveling software on Lafayette street makes you a better software engineer than doing the same on the Rákóczi Körút. On the other hand for many people living and working in New York is nothing special. They were born there, it is their normal.
I for one think where you were is not as important as what you made of your time there.
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)
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.
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.
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.
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.
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.
Just one example is that the ability to write/draw allows you to solve problems that are impossible without it.
https://daily.jstor.org/how-do-we-know-that-epic-poems-were-...
But there are so many skills lost due to the privilege of technologically enabled sedentary life-styles...
can you imagine attemting to found a town/village/city in flat/cold/resource-constrained climates without electricity/supply-lines?
Those people before us had balls and conviction of steel - and even more-so for the women. You would not exist without a woman (mother) and women are stronger than men.
Studies of using mnemonic techniques to memorize long sequences (similar to what oral performers were doing) have also not shown much promise in increasing cognitive abilities.
> 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...
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.
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.
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.
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.
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
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)
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?
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.
It would not be surprising to find that most structures weren't built to last any longer than ours, but that some were meant for the ages. An important difference today is we don't build the latter sort, excepting maybe the Sydney Opera House. Many people act personally offended that it doesn't have steel inside.
"Secundus was an apprentice to Marius who was an apprentice to Darius, who built that awesome aquaduct; Marcus was an apprentice to Felix who who was an apprentice to Marcellus, whose shit bridge fell down after twenty years. We're going to hire Secundus instead of Marcus."
De Architectura provides the sort of long-term perspective required to build and engineer projects that were meant to last for centuries, based on experience gathered from centuries of recorded experience.
I'm not sure if De Architectura is the only book that Roman Architects used. But it was certainly the most important.
Hundreds of pages of De Architectura list dimensions of older ancient buildings, the dimension and spacing of pillars, and failures encountered during or after construction. Something along the following lines (not actual text):
---
The second Temple at Delos was built in 432bce. It consisted of 13 x 29 doric columns, 6' in diameter, 22' high, spaced on 12' intervals, with two rows in the pro-cella. The cella measured ..... The entrance to the cella was 16' high and 12' wide with a granite lintel measuring 16' x 3' x 2'.
The lintel above the entrance cracked and had to be replaced after an earthquake in 430bce. The front-right architrave cracked in 329bce, but was not repaired. The temple was subsequently abandoned and collapsed completely after an earthquake in 327bce.
The temple of Apollo at Thebes ....
The main architrave cracked while it was being mounted, and further construction was abandoned.
---
Given a hundred or so such examples, a Roman architect of a new temple could make somewhat informed decisions about how high, how wide, and how thick he would need to build a new temple, and how afraid he should be when he was commissioned to build a new temple that was higher, wider, or taller.
we just don't build a lot of them.
In which case your first worry would be to make sure he doesn't collect your blood samples.
…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.
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.
i wonder how all those detailed recipes were passed around for many centuries and now all is gone. Was it all passed down verbally?
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'.
- We know that early Damascus examples were made from imported Wootz ingots, which we absolutely can recreated.
- The high quality of the blades were due to naturally occuring impurities of molybdenum, vanadium, and chromium, all of which are used in various modern alloys.
- Forging and heat treating processes varied greatly across historical blades called "Damascus" and we have sequences that create both visually and metallurgically similar results.
Especially steel-reinforced concrete, the lifespan is only 50-100 years. The only exceptions are massive structures like dams that will probably last a couple millennia.
For Damascus steel and Greek Fire we almost certainly still have the knowledge. We just lack a document to tell us that "Greek Fire" matches formula #44 of napalm specifically, or what specific process an ancient smith actually followed.
For the spaceships, no, we have the plans, but they're long obsolete. They're made for ancient, manual equipment nobody uses anymore, and old materials that have since been improved on. We technically could dig up and restore ancient manual milling machines, recruit retired engineers and special order obsolete materials and parts, but what for? Unless you're engaging in experimental archaeology what you want is a rocket, not the rocket that has a nostalgic feel to it, and it'd make far more sense to make one with modern methods.
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.
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.
I liked your comment but this bears correcting. (Corrosion of) rebar is actually the biggest cause of spalling in vertical concrete structures.
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.
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]
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.
Tangent: coarse sand is also important for certain types of septic systems to function properly.
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.
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.
So this method wouldn't necessarily work in a dry climate without much rain?
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.
I was picturing pouring it into a void for some reason.
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.
Facility has a "no sparks" in buildings A, B and C rule. Rule obviously doesn't apply to contractors doing a ton of welding during a holiday shutdown. Non-contractors in maintenance dept want to fix some other crap at the same time. Sure they could try and get approval to use a jackhammer concurrent with the other work but in reality there's a 75% chance the safety department will intentionally stonewall until after the shutdown rather than set the precedent of a sensible exemption and the maintenance manager knows it so they buy the expensive grout.
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://youtube.com/playlist?list=PLTZM4MrZKfW90PdaBFt70BLTb...
Here is an excellent read on this subject from 2013: https://cedar.wwu.edu/geology_facpubs/75/
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.
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.
A common thread, and no doubt mutual fascination behind Jackson's and Seymour's research, is the use of specific pozzolans found in and around Campi Flegrei volcano west of Naples.
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.
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.
Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more. Making no provision for when it will predictably fall apart is a modern failing. That major construction with concrete is about a century old should worry everyone.
We have a very great deal of infrastructure that will fail on a predictable schedule, with nothing budgeted to replace it all.
Do you have a citation for this? As far as I know this is entirely not true.
Rust is an expansionary product - when steel rusts its volume increases something like 10x, which reduces the connection between the concrete and the steel and causes issues like cracking and spalling. Minimizing rust improves the long term performance of rebar.
What? This is total nonsense.
> Modern concrete isn't expected or designed to last more than a century. It could have been made to last longer, if they wanted, but that would cost a little more.
Is hacker news a conspiracy theory website now?
> We have a very great deal of infrastructure that will fail on a predictable schedule
Wood rots in a few years under certain conditions and can last hundreds in others. Concrete works similarly.
The 3rd pantheon is currently standing, but it is a huge mix of repairs across centuries. The Romans built many structures that are similar but now are in ruins because the Catholics didn’t maintain the roofs on bathhouses.
Reinforced concrete ALWAYS cracks.
If you want better corrosion resistance, you do other things - lower water ratios, increased concrete cover, sulfate resistant concrete with lower permeability, different reinforcing or epoxy coated reinforcing, etc.
And while you absolutely have pretensioned girders on bridges commonly, the bridge decks generally aren't, although they're almost always completely in compression and the steel is there for shrinkage cracks etc.
[1] https://www.youtube.com/watch?v=UOHURuAf5iY&list=PLTZM4MrZKf...
The rebar handles tensile loads, the concrete handles compressive loads. You put the rebar where tension will exist so that it can handle that. Some amount of cracking on non-pretensioned concrete is normal and unavoidable.
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.
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...
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.
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.
The Parthenon is one (1) building that survived basically as-is while countless others were actively demolished.
One thing that surprised me when visiting Rome is how little original buildings existed. But when you get increasingly far from the city of Rome, you’ll find quite a few well preserved Roman buildings that were out of reach of the long tentacles of the Catholic Church.
The OP suggested that the loss of architectural art is mainly due to a clash of different cultures and to religion. While there were cases where this was surely true (the many churches destroyed during French Revolution!), in most of the cases the reasons were much more practical and did not involve conflicting cultures or the «long tentacles of the Catholic Church».
Before the concept of «historical preservation» was invented, what should have been the point to keep a temple to Venus in the crowded center of a city, when nobody worship her any longer and that very space could have been used for something more useful?
These acts of destruction happen all the time even within the same cultural context. For instance, the old Vatican Basilica, built in the IV century, was destroyed and rebuilt in the XVI century by the Pope himself! And the same applies to countless of other important ancient churches and public buildings (My favourite example: the astonishing church of St. Clemente [1], well worth a visit if you're in Rome! The XI-century building was erected over the old VI-century church.) Not only churches, but frescoes in churches have been continuously covered by newer frescoes, once the taste of the church goers changed. A few days ago I visited the beautiful church of Sant'Abbondio in Como [2]: the church dates back to the XI century, but the old frescoes were covered by newer ones in the second half of the XIII century.
Even the Romans did the same for many of their buildings: once they realized that they were no longer useful or usable, they either repurposed them or destroyed and built something else on the rubble. The Colosseum was not built on pristine land! And Nero destroyed a lot of houses to build his Domus Aurea, which was later destroyed by Vespasian and Titus and covered by newer constructions, with the intent of make people forget Nero. (No, as far as I know neither Nero nor Vespasian or Titus were catholic.)
It's a pity for scholars, but before historical preservation was a thing, it was often the best thing to do, as the older buildings did no longer fit their purpose. These acts of destruction made the world lose important pieces of art, but they were meant as a way to repurpose the spaces of the city according to the evolved needs of its inhabitants. This is particularly true for cities like Rome, which have been populated continuously for ~2500 years.
[1] https://en.wikipedia.org/wiki/San_Clemente_al_Laterano
[2] https://it.wikipedia.org/wiki/Basilica_di_Sant%27Abbondio
This isn’t even touching on the subject of the Latin corpus which is ONLY extant because of the Church.
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...
> 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.
> ... 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.
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.
Sounds good to me?
Although, many centuries old sound structures also sounds better to me...
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)
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…
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.
That puts rather different perspective on the quality and longevity.
How does a building, an aqueduct, or a bridge still in use after 2000 years manage to be inefficient?
> 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?
> In 2012, Paul Lecroart, of the institute of planning and development of the Île-de-France, wrote that "Despite initial fears, the removal of main roads does not cause deterioration of traffic conditions beyond the starting adjustments. The traffic transfer are limited and below expectations".[4] He also notes that some private vehicle trips (and related economic activity) are not transferred to public transport and simply disappear ("evaporate").[4]
> The same phenomenon was also observed when road closing was not part of an urban project but the consequence of an accident. In 2012 in Rouen, a bridge was destroyed by fire. Over the next two years, other bridges were used more, but the total number of cars crossing bridges was reduced.[4]
It seems a lot like the real-world examples of the phenomenon look like close cousins of "if you remove the smallest values in a set, the average goes up".
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.
They're insanely slippery when wet. A freeze-thaw cycle tends to make them move, eventually leading to weird dips and ridges. They're expensive to install and more expensive to maintain.
my town used dirt as the "mortar" between bricks, so there was no solid joint to degrade over time. I do remember crews going around and spreading small amounts of dirt on those roads, to refill what little rinsed away after spring thaw. they'd just have a guy following behind the truck with a push broom moving the dirt so it fell between bricks.
dirt is dirt cheap.
Also, people vastly underestimate how cheap road surfaces need to be. Try and calculate the volume of material making up the US road system.
I live at the end of a deadend road that is 0.9 miles off another very rural road.
The road is chip sealed, which according to google in 2022 is $25,000 to $42,000 per mile.
There are 7 parcels that collect $6396 per year in property taxes.
At the low end of the chip seal price, it would take 3.53 years to pay it off and 5.9 years at the high end.
This assumes that no sales or gas taxes are used to fund any of the road construction, which isn't true.
Over their lifetime, easily. The pipes for those will last 100 years, easily. The maintenance of them are paid for by the delivery costs you pay in your bill.
As for rural I think there's 2 distinctions. 1 is we need rural communities because they produce our food and other things. Secondly, rural areas are between 2 or more populated areas. We need to connect populated areas so by necessity there are roads. Rural communities are built off of those.
The other distinction where you may be closer is exuburban communities built into rural areas. These may or may not be fully covered. Not initially anyways, but you'd assume the property taxes would cover in time.
My wife served on a sanitary district board. Decent underground sewer mains have an expected service life of 70 years. Some will last longer, some won't hit the expectation. It depends on site conditions, materials, etc, etc. Many will probably last to 100 years, but I wouldn't expect it to be easy. Especially if you had any of the not decent materials (Orangeburg pipe was common in some areas and is basically wood pulp/fibers mixed with hot tar; service life could vary between 10 and 50 years; the major manufacturer went out of business in 1974, as PVC and ABS pipes rapidly replaced Orangeburg in the materials markerplace).
Actually there was a huge nationwide boom in sewer building post WWII, especially in the 50s, and you can expect that infrastructure to need some largescale replacement over the next 20 years or so. Depending on system design and how housing and industry developed, some systems will be able to just inspect periodically and replace as needed, and some systems will probably take the opportunity to do a more modern redesign (older cities tend to have combined sanitary sewers and storm/runoff drainage; if you're tearing up all the streets to replace the sanitary sewer, it might be a good time to put in a parallel storm drain system)
I'm not sure about water mains, I'd guess they need more frequent replacement since they operate at pressure.
I don't have utility water; it's available on my street, but it doesn't run by my house, it stops at a much lower elevation, our well water is fine (although we had to replace the well pump recently which was expensive). No utility sewer either, that's available in parts of my area, but mostly places with density or poor site conditions for septic or both.
Electricity is mostly overhead, with a little bit of underground telephone has a lot of undergrounding, but some overhead, cable and municipal fiber are almost all overhead. But when those are undergrounded here, they're on the sides of the road (directly under the overhead path) not under the road. That way it's easier to get to them for maintenance when needed.
How sustainable is a system that requires perpetual good times?
Calling it a ponzi scheme is a stretch, but this guy seems to be the only one talking about this: https://www.strongtowns.org/journal/2020/8/28/the-growth-pon...
Also easy expansion is more a function of interest rates than anything. Municipal bonds buy everything and there’s been very little interest on them. This means fewer taxes to buy things. And new bonds can be sold down the road as the town increases tax base and interest rates fall.
To think that the USSR had better infrastructure (less corruption) than modern day corrupt places like Montreal is a brutal shock.
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.
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.
[0] https://www.sciencedirect.com/science/article/abs/pii/S00225...
Assuming they didn’t want their structures to last as long as the ancient ones (at their time) is just laughable.
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
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.
It gets hot when you mix it.
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.
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.
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)