I was just reading an article where the university of Utah has discovered that Roman concrete has the ability over time to build interlocking minerals that can aid in repairing cracks and give the structure added strength.
never2late454 - interesting... I was once on a tour of a castle in the south of england. There were many large and hard material stones holding the place up, but, at around the top were some soft stone blocks... when asked, the tour guys best theory was that softer stones could be sacrificial as they weather easily. This weathering in rain allows the minerals to deposit on the stones below... It sounded like bs at the time to me, maybe there was something to it...
Paticularly interesting is that they had different mixes for different applications. They had a mix that they used for saltwater. It strengthened over time due to mineral bonding caused by the salinity of the ocean. Anyone who has been to Naples can attest to this
It took months to cure, gain maximum strength because they were using pozollan cement. Portland cement did not exist during those times. Volcanic ash were common mortar/grout in many fortress . Besides pozollan is still cheaper than portland.You have a discussion on pozollan cement and Portland cement in your past video. Very interesting discussion ,engineer.
I grew up in a small town with a Roman fortress. Built at the extreme end of the Roman empire. Huns destroyed it several times and it was re-built. As kids we used run over it, on top of Roman concrete containing many big rocks taken from rivers. There was not a single crack. And it felt more like granite than like current concrete. Roman concrete in seawater reacts with phillipsite to form aluminum tobermorite, a crystal harder than modern concrete. And it can flex a little bit. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself. 2000 years and Roman concrete in the sea is still there and stronger than when it was young. On land Roman concrete was built by hand and water for it was carried by hand. So they used far less water than we do. And that's why Roman concrete contains grains and bubbles of cement which is not fully hydrated. If a crack forms and water enters it can react with one of those cement grains or bubbles and they expand and harden.
Nice video, the bar fight was a good reference to explain the elasticité and rigidity of materiels ! I like what you did there! True, ciment has a important modulus compared to lime. I guess for me to understand the concept, it was quite a challenge, PS: I was young ! Anyway, I want to understand more about the behavior of the lime mortor. So, I eager to see a video about it very soon if possible !
We have in my country Roman ruin structures and yes they contain reinforced steel/iron . . I saw it with my own eyes and that huge round cylinder was so heavy it wouldn't budge no matter how hard I tried to lift it, even for expecting to move a little, I felt like I was tearing my self apart
The individual blocks definitely helped with the expansion and contraction. Concrete when spread out will crack. However if you think of it like their blocks, 3d! If you want it to crack less make it thicker... if you make it a perfect square (not recommend, could get expensive quick) it has no weak spots. Opposite side- we add weak spots to "make" it crack where we want
When I first start to work with concrete they would tell us it would take 28 days+ before concrete got ideal starting strength, we had to keep it wet for that period.. About 20 years ago it started being 3-4 days . Old concrete would cure pretty cool. Modern Concrete seem to get hotter and drinks more. Some of that old concrete which I consequently had to remove 30 years later was very very hard.
Actually it’s because of the lime chunks would help “self heal” when water got to it the lime would fuse back to gather. You add the lime to the water first and it doesn’t fully dissolve leaving the big chunks of lime to them help up to 6mm cracks co paired to now a days 2mm is the most new Concreat can “heal itself”
In San Fransuco, Ca my fathers family where at 1st, starting 1870's onwards : where stone masons, plasters, building contractors of small homes & concrete finishers. Odd note: Concrete foundations & sidewalks put in before 1920 had a pink tint to it. And the pre 1920 concrete foundations where very, very crumbly with age. Too much gravel in the mix!
How would concrete behave if it were made of pure diamond which has the highest modulus on earth? I feel like a loaded column 2’x2’ could take incredible stress without deformation. It doesn’t have a low modulus, in which you state that lower is better for durabilitys sake of concrete. I guess im just confused, wouldnt you want the cement paste and aggregate to not be so elastic? Like a high psi mix designed with high modulus materials to absorb stress to limit the strain?
I know this is kinda off topic, but iv always wanted to get giant crystal columns from that one cave in mexico. GIANT quartz crystal columns! And diamond would prob be a great aggregate in cement, but too expensive ofcourse. Id like to make my concrete with granite chunks and powder, just cause its a longer lasting stone than limestone.
Lime mortars and concrete, unlike Portland cement, could REPAIR themselves over time. That's exactly what was superior about them. Also, unlike modern masons, traditional masons understood very well that mortars must be WEAKER than what they were holding together, else the structural material would be fractured by the mortar. Lime mortar takes the damage from forces and expansion, and heals itself. Portland cement mortars are in no way capable of this.
Johan, Thanks for the message. Portland cement mortars or concrete can heal themselves. However, I have never seen it compared quantitatively to lime mortars. Thanks for the cool idea.
On the Bar Fight bit, effective catchy analogy. A problem with alcoholics though: they get hurt much worse in a fall. Their reaction times and effectiveness are slowed. So in a fall, they don't protect themselves in time. Alcoholics bash their head and wrists etc in falls, stumbles that quicker, surer moving sober/soberish people don't get into.
Where possible, carry out the tests on an accurately measured grid. This will remove bias from the data. If a grid is not used, the tests will tend to be in easily accessible locations that may have also been accessible for maintenance, and will thus be in better condition, or more exposed, leading to a worse condition. What is meant by this statement ?
Roman Construction...About being in mild climate....my co-worker from years ago (an engineer from England) worked on the partial restoration Roman bridges of antiquity(around and in water) ...he couldn't believe/was baffled by their super strength and how they lasted in frigid-wet weather. Did they transport volcanic materials over the sea? And Inland?
I don't agree with your explanation that because roman concrete had low modulus hence it lasted longer. Modulus (E) is the slope of stress - strain curve and it has nothing to do to how much stress can a material take before cracking. This depends on the ultimate strength of the material. Ultimate strength of concrete (fc') is greater for high modulus concrete than for low modulus concrete. As per ACI, E=57000(fc')^0.5 The correct way to look at the issue here is that if you build identical structures with identical loads but one with higher modulus concrete and one with lower modulus concrete, then concrete with low modulus will undergo larger strain for the same load and will crack earlier, unless it has plastic stage which no concrete has. Concrete with higher modulus will undergo less strain and fail later. Structures are always designed for given loads not for a given strain. In my opinion Roman concrete was durable because structures were designed in such a way that concrete remained under compression or minimum tension, hence cracking did not develop. Moreover, there was no reinforcement in the concrete which would corrode. Although I would say that lime might also play some role in durability of Roman concrete but not sure how significant it might be.
Hasan - Thanks for your comment. We must keep in mind that it is the deformations that cause the damage. Materials with more deformation capacity have the ability to dissipate energy and ask for help from other parts of the structure before they fail. See my video on structural resiliency - czcams.com/video/5P3BZUDz-9g/video.html Think of a paper plate and a glass plate. If a glass plate is loaded to its limit then it fails in a brittle manner. However, the paper place can bend a lot under the same load. This allows it to survive under a given load. I agree that having structures under compression is also a great idea but this lower modulus is a concept that is used in a lot of materials to dissipate energy before it fails. Think of bending but not breaking.
@@TylerLey I agree that material which can deform more and has more toughness has the ability to dissipate energy and survive longer, that is why we provide reinforcement because concrete has low toughness and exhibits brittle failure. However, in Roman concrete there was no reinforcement and we are left with concrete only. Concrete of lower modulus will not deform more, rather it will deform earlier but the total deformation for lower strength concrete will be almost the same as higher strength concrete. We take ultimate strain of concrete as 0.003 which is same for all strengths of concretes. Therefore concrete of any strength has the same potential to deform i.e. 0.003 strain. However, higher strength concrete will reach this strain at higher load than lower strength concrete, thereby exhibiting greater toughness (area under stress-strain curve is more for higher strength concrete than lower strength concrete, for ultimate strain of 0.003).
Don't forget their water to cement ratios were multiple times less than modern concrete and they dense packed it in place, literally beating it into compaction. Also their mixes were much more closely monitored to maintain consistency from one side of a building to the next (which is a serious problem we encounter when we try to copy their arche and dome shapes)
In seawater Roman concrete creates aluminum tobermorite, a crystal harder than modern concrete. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself. On land everything was carried by hand, including the water for concrete. So they used much water than we do and thus their concrete was much dryer than ours. And grains of it were not fully hydrated. And if water enters through a crack it can react with those grains, which then hydrate - expand and thus close the crack.
@hasanshirazi9535 Apologies for reviving this 5-year-old thread, but I hope that, in the meantime, you have learned that concrete is a viscoelastic material. Low modulus materials are more resilient to volumetric instabilities (i.e. creep and the many forms of shrinkage) because they allow for larger internal strains before the material fails in tension and cracks. These microcracks then greatly reduce the ability of concrete to resist the ingress of water and/or deleterious chemicals. I know how complex structural engineering is, but you guys could definitely use a couple of materials courses...
More relevant reasons their concrete lasted thousands of years and ours typically fails within a century is their water to cement ratio, precise mix consistency, and completely different installation technique.
I wouldn't believe for a second it's an issue of precision. I would think we can much more accurately and precisely control the mix ratios with current technology. Nor would I believe it's a water to cement ratio. The people like this professor have had centuries to experiment with varying the two parameters of cement and water. There is very little chance that the magic behind Roman concrete lies in that combination.
@@nonconsensualopinion it's not a matter of speculation. We know what the romans did. They used multiple times less water and because they used domes with no mesh, their aggregate mixes had to be more carefully balanced so as to avoid uneven stress. Also they used higher quality pozzolans. It's not that we couldn't do that, but that we don't. No one wants to pay to dry pack their concrete into forms with mallets, so we use steel to hold our weaker concrete together.
@@nonconsensualopinion Everything was carried by hand obviously. Including the water for making concrete. So they used far less and their concrete was much dryer than modern. And grains of cement in it did not fully hydrate. And if a crack forms and water enter it can react with those grains and they expand and harden. Self healing up to a point. In seawater Roman concrete forms aluminum tobermorite, a crystal harder than modern concrete. It can flex a little bit. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself.
how much of it has to do with vertical loads versus horizontal loads? They didn't use rebar, that makes it last longer or shorter for reasons we understand. Which or their structures did not last? I suspect it may be the ones that had more horizontal loads applied to them and could have benefitted from rebar. Of course I ablsolutely agree with your other reasons you presented, why some have lasted so long, climate being the most important IMO
Good question! I think that would be a good thing to research. The existing structures are in areas with very mild climates. There are some sea walls in Britain that still exist but they are in the ocean and so they don't freeze.
Gosh, I sure do wish I'd run across you before. Many of the things you talk about here we have addressed by streaming UHMWPE fibers into concrete. We just had our first fullish size test (8'x25'x0.5' panel) and you can see it on TNSRsys.com/prototype. There are lots of advantages. Do you think we can edge lift 8'x40'x1' panel? Without steel. Coming soon....
Hello, I keep coming back to track steel in my question as what would work cheaply for rebar. When I was growing up around here there were a myriad of small marine railways that went out to low water. Then a cradle was lowered out at high tide to submerge and let boats run on to them. Once on they were chocked and a winch drew them up into the shop where work was done. The point is this is another case where steel rails were submerged in salt water twice a day as well as out in the weather for decades. Nary a sign of flake rust at all. A patina of rust on the non load surface was the most you'd find. Would not this formulation of steel be trick as rebar for long lasting concrete? I would love to hear a metallurgist chime in because it sure looks like a better answer than epoxy, paint, galvanizing etc that have been tried and failed. Would not be near as expensive as stainless or exotic alloys nor subject to crevasse corrosion etc. Take care. Doug
Thanks for the comment. What structure did you have in mind? Italy is in a very mild climate. It is very similar to southern California. There is a sea wall in the UK that is discussed but it gets cold but it doesn't freeze or the entire ocean would freeze. Keep in mind that temperature changes that our bodies respond to are not the same temperature ranges that impact concrete.
Good video and topic. However, the graphs are entirely useless. lol They only say the same thing you already say over and over, about time to harden, and the modulas. The graphs don't even have data points. Their just a visual representation of those same statements, based on no data. lol Anyways, I'm just nit-picking because it was funny to me. 🤣 But, good videos and topic. You seem to have alot of knowledge about concrete. Roman concrete and other forms of homemade concrete are very interesting and useful to me. I subscribed. I think I can learn alot from your channel.
The aqueducts are mostly stone...not concrete... The weather in that region of the world is anything but mild from an ecological perspective. It is a ocean exposed biome, that is highly tectonically active...and the reason "natural cements" didn't need reinforcement was because of the way it was build with and understood...Reinforcement simple was not (is not!) needed in the modern context. So no...these where not "great environments" at all to build structures...no greater than many other places. I was the material itself and the craft of designa nd application...not the biome. As for your point many didn't last...???...That is rather moot...Many structures don't last. However by comparison, the vernacular forms out last the modern by significant margins...including in the world of traditional geopolymeres, limecretes and natural cements... We "choose"...!!!...to use steel inside our modern concrete because of politics...not best practice...that is a choice and not a pragmatic or logical one, but rather one of greed, sloth and consumerism within today's normative cultures... It was difficult to listen to many of your comments about "need for speed" which sounds more like an advertising campaign for the concrete industry than it does actual understanding of architecture and its impact, not only on society at large, but the future health of this planet that concretes hold over a quarter share in destroying. The videos tonight that I have had to watch because a student shared them with me is the disconnect between an "academic" that seems more concerned with promoting a material rather than really learning the full impact and realities of that material. I don't know yet? Perhaps you real goal, long term is to bring back "good natural cements" which I could support both architecturally and ecologically...but somehow I don't think that is the case...
Considering the curing time of concrete (if that's the correct word) I wonder if you'd be willing to discuss in a future video the possibility of using cements that absorb CO2 as they cure? Ideally, from a global carbon perspective, we'd want the cement to absorb more CO2 as it cures than was released in the entire production process. That would make conduction industry a boon to the planet rather than a problem. Is this even feasible? I'd love a professional perspective on this issue. Warm regards
You said you guessed they didn't open it for a year, this isn't the right reasoning.. you mentioned lack of corrosion, what about the Roman concretes standing in the ocean being hit by waves and salt millions of times more then out concrete
Modern concrete would have no problem with waves and salt water if it didn't contain steel. I don't understand your first sentence. It was common knowledge in Rome that concrete gained strength over time. They left their concrete roads empty for at least a year before using them. We don't do that with modern concrete.
@@TylerLey ah you sounded like you were making an educated guess over fact about the curing time of the concrete, Maybe I misheard - it's early here and alcohol is still in the system We do also have concrete additives and curing methods to further strengthen the concrete, eg. Watering it for up to a few weeks after, different aggregate sizes. What about galvanized steel? Would that be any stronger when exposed to water / erosion etc? Aren't there theorys about the substances they used in concrete that are lost today?
Sam, You are right! We have lots of tricks to tailor our concretes today that didn't exist before. I love galvanized rebar! It is better than the normal rebar that we use but it will still break down and corrode. I talk about it here: czcams.com/video/xVDy84rR5Z8/video.html Roman concretes are different than what we use today. They used lime and volcanic ash. Today we use portland cement and fly ash. Fly ash is man made volcanic ash. The Roman concrete may be better at resisting cracks but modern concretes are more consistent, gain strength faster, and can be designed to have long lifespans. It just depends on what you want your concrete to do and what you can afford. Thanks for the conversation!
England's greatest PM is one thing, but actually the greatest thing about England's Prime Ministers is that not one of them were Donald Trump. ... ... ... has the bar fight started yet?
Did European people *forget* how to make concrete after the Western Roman Empire collapsed or was there no longer the infrastructure to support cement production?
Both. The secret to Roman concrete was a closely guarded secret: volcanic ash was the pozzolan that made Roman cement different from the soft lime cements that everyone else knew about. When the Roman empire collapsed the few people who knew the secret no longer had access to volcanic ash and no one made a comparable cement until Portland was discovered in the 19th century
Both, plus a third thing: due to the difference in Imperial building projects and those that immediately followed there was no longer the desire to build such huge structures. That reason logically and actually came before both the points you mentioned: it explains why the skills were not maintained, and why the industries to produce the material went out of business.
I use a lot of analogies when I am speaking extemporaneously. I've come up with some odd ones over the years that raised a few eyebrows and got a few uncomfortable laughs. This "bar fight" analogy is the *absolute worst* simile for concrete elasticity. The basis for your analogy is based on movie scripts (See www.TVTropes.com ) and not reality.
@@TylerLey Fine, you can stick by your analogy, if weakly. But at least give my comment some thought in 5, 10, 20 years... when you re-watch this video and cringe at your choice of comparison logic. Hmmm.. maybe it wasn't the bad analogy but the terrible delivery? Could a comedic tweak have made it more palatable? Perhaps the entertainment value would have helped.
uruiamnot Perhaps you have too much time on your hands, or you are a secret entertainment critic . I’m sure the good doctor will be wincing about this subject topic in 30 years........sure
Your speculating based on your oppinion as there are breaker walls in contact with the sea in England still standing. As a builder (not a reader of) Roman comcrete are far more durable than present concrete used, the reason we don't use it is that Roman concrete is more labor intense. Also I dont believe youd do well in a bar fight with your knowledge, that too requires much hands on to know what works, theory is for non doers-self proclained "teachers" that teach bad practice and offer bad advice. you do sustain as much damage BTW ,you simply are too drunk to care and you dont register pain as much when drinking, hence drinking before surgery prior to modern medicine. Your welcome if your not too proud of your paper, if you are sorry for wasting my time to offer sound, practicle exp regarding your bunk theorys that are barely more than fanciful thoughts that don't really apply outside of talk.
John, I agree that I don't know for sure why some things fail and others don't. However, those Roman walls in England don't contain reinforcing steel. Corrosion of reinforcing steel is a weakness of modern concrete. If we could design them without it then that would greatly increase their life. Materials with a lower modulus experience less stress than a material with a high modulus for the same deflection. This is a truth that is a widely known. For example, compare a serving plate made of glass versus a paper plate. You can deflect the paper plate a lot and it doesn't break. Is the paper plate stronger than the glass plate? No, it has a lower modulus. This is the concept that I am trying to teach. Let's say you are going to be hit by something. In one circumstance you tense up and in the other circumstance you are relaxed. When you tense up your body will take more damage and you will feel more pain because more of the load is transferred to your body. If you are lose then your body will give when you are hit. The force is dissipated as you give and less of it will transfer to you. This is why we have bumpers on cars. It crumples and gives when something hits it. This is why we design our structures that will see earthquakes or bomb blasts to give and not be too rigid. Think about it and let me know if it makes sense. You seem to have lots of experience. I bet you have seen this in your life.
Tyler Ley heres a begining beyond the I dont know (link below) bit you would know if you knowledge base was not theory. czcams.com/video/R9sZSrhoPJY/video.html
Stainless steel costs about 6x more than normal rebar. There is also not enough stainless produced every year to supply enough to replace rebar. I have a recent video where I talk about it here: czcams.com/video/1ELHzXuwdqg/video.html
I was just reading an article where the university of Utah has discovered that Roman concrete has the ability over time to build interlocking minerals that can aid in repairing cracks and give the structure added strength.
never2late454 - interesting...
I was once on a tour of a castle in the south of england. There were many large and hard material stones holding the place up, but, at around the top were some soft stone blocks... when asked, the tour guys best theory was that softer stones could be sacrificial as they weather easily. This weathering in rain allows the minerals to deposit on the stones below... It sounded like bs at the time to me, maybe there was something to it...
Paticularly interesting is that they had different mixes for different applications. They had a mix that they used for saltwater. It strengthened over time due to mineral bonding caused by the salinity of the ocean. Anyone who has been to Naples can attest to this
Great analogy, I'll NEVER forget that. It's hilarious
It took months to cure, gain maximum strength because they were using pozollan cement. Portland cement did not exist during those times. Volcanic ash were common mortar/grout in many fortress . Besides pozollan is still cheaper than portland.You have a discussion on pozollan cement and Portland cement in your past video. Very interesting discussion ,engineer.
Love the bar fight comparison
I grew up in a small town with a Roman fortress. Built at the extreme end of the Roman empire. Huns destroyed it several times and it was re-built. As kids we used run over it, on top of Roman concrete containing many big rocks taken from rivers. There was not a single crack. And it felt more like granite than like current concrete.
Roman concrete in seawater reacts with phillipsite to form aluminum tobermorite, a crystal harder than modern concrete. And it can flex a little bit. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself. 2000 years and Roman concrete in the sea is still there and stronger than when it was young.
On land Roman concrete was built by hand and water for it was carried by hand. So they used far less water than we do. And that's why Roman concrete contains grains and bubbles of cement which is not fully hydrated. If a crack forms and water enters it can react with one of those cement grains or bubbles and they expand and harden.
I never knew what I was in for when I looked up diy Roman concrete...
From a friend who got into numerous fights: Hit First, Hit Hard, Hit Often.
Nice video, the bar fight was a good reference to explain the elasticité and rigidity of materiels ! I like what you did there!
True, ciment has a important modulus compared to lime. I guess for me to understand the concept, it was quite a challenge, PS: I was young ! Anyway, I want to understand more about the behavior of the lime mortor. So, I eager to see a video about it very soon if possible !
We have in my country Roman ruin structures and yes they contain reinforced steel/iron . . I saw it with my own eyes and that huge round cylinder was so heavy it wouldn't budge no matter how hard I tried to lift it, even for expecting to move a little, I felt like I was tearing my self apart
The individual blocks definitely helped with the expansion and contraction. Concrete when spread out will crack. However if you think of it like their blocks, 3d! If you want it to crack less make it thicker... if you make it a perfect square (not recommend, could get expensive quick) it has no weak spots. Opposite side- we add weak spots to "make" it crack where we want
Dont get into one. That is how you win.
Not always possible. Speaking from experience.
When I first start to work with concrete they would tell us it would take 28 days+ before concrete got ideal starting strength, we had to keep it wet for that period.. About 20 years ago it started being 3-4 days . Old concrete would cure pretty cool. Modern Concrete seem to get hotter and drinks more. Some of that old concrete which I consequently had to remove 30 years later was very very hard.
That bar fight analogy is crazy. Literally.
Thanks!
Weren't there roman concrete structures in the sea and on their coasts? How did those structures endure? What are/were their modes of failure?
Actually it’s because of the lime chunks would help “self heal” when water got to it the lime would fuse back to gather. You add the lime to the water first and it doesn’t fully dissolve leaving the big chunks of lime to them help up to 6mm cracks co paired to now a days 2mm is the most new Concreat can “heal itself”
In San Fransuco, Ca my fathers family where at 1st, starting 1870's onwards : where stone masons, plasters, building contractors of small homes & concrete finishers.
Odd note: Concrete foundations & sidewalks put in before 1920 had a pink tint to it.
And the pre 1920 concrete foundations where very, very crumbly with age. Too much gravel in the mix!
How would concrete behave if it were made of pure diamond which has the highest modulus on earth? I feel like a loaded column 2’x2’ could take incredible stress without deformation. It doesn’t have a low modulus, in which you state that lower is better for durabilitys sake of concrete. I guess im just confused, wouldnt you want the cement paste and aggregate to not be so elastic? Like a high psi mix designed with high modulus materials to absorb stress to limit the strain?
I know this is kinda off topic, but iv always wanted to get giant crystal columns from that one cave in mexico. GIANT quartz crystal columns!
And diamond would prob be a great aggregate in cement, but too expensive ofcourse. Id like to make my concrete with granite chunks and powder, just cause its a longer lasting stone than limestone.
Didn't the Romans use pozzolanic materials from old volcanoes ?
I read the same.
@@Albert-fe8jx yes they did
Lime mortars and concrete, unlike Portland cement, could REPAIR themselves over time. That's exactly what was superior about them. Also, unlike modern masons, traditional masons understood very well that mortars must be WEAKER than what they were holding together, else the structural material would be fractured by the mortar. Lime mortar takes the damage from forces and expansion, and heals itself. Portland cement mortars are in no way capable of this.
Johan,
Thanks for the message. Portland cement mortars or concrete can heal themselves. However, I have never seen it compared quantitatively to lime mortars. Thanks for the cool idea.
@@TylerLey I'd love to see some research on this. Any chance you know where to find some?
@@knewsom I am in too !!
there is research. they are capable, you do not need weak mortar like concrete with 10MPa bricks analogy.
@@Baigle1 Got links?
Thank you very much sir..
On the Bar Fight bit, effective catchy analogy. A problem with alcoholics though: they get hurt much worse in a fall. Their reaction times and effectiveness are slowed. So in a fall, they don't protect themselves in time. Alcoholics bash their head and wrists etc in falls, stumbles that quicker, surer moving sober/soberish people don't get into.
Don't see the link you mentioned about Roman Concretes and their being belite based.
Where possible, carry out the tests on an accurately measured grid. This will remove bias from the
data. If a grid is not used, the tests will tend to be in easily accessible locations that may have also
been accessible for maintenance, and will thus be in better condition, or more exposed, leading to
a worse condition. What is meant by this statement ?
I know it be more expensive, but, would galvanized stainless steel be a non corroding reinforcement?
Roman Construction...About being in mild climate....my co-worker from years ago (an engineer from England) worked on the partial restoration Roman bridges of antiquity(around and in water) ...he couldn't believe/was baffled by their super strength and how they lasted in frigid-wet weather. Did they transport volcanic materials over the sea? And Inland?
Why was rosendale cement mixed with portland cement to build roads to make them more durable?
I don't agree with your explanation that because roman concrete had low modulus hence it lasted longer. Modulus (E) is the slope of stress - strain curve and it has nothing to do to how much stress can a material take before cracking. This depends on the ultimate strength of the material. Ultimate strength of concrete (fc') is greater for high modulus concrete than for low modulus concrete. As per ACI, E=57000(fc')^0.5
The correct way to look at the issue here is that if you build identical structures with identical loads but one with higher modulus concrete and one with lower modulus concrete, then concrete with low modulus will undergo larger strain for the same load and will crack earlier, unless it has plastic stage which no concrete has. Concrete with higher modulus will undergo less strain and fail later. Structures are always designed for given loads not for a given strain.
In my opinion Roman concrete was durable because structures were designed in such a way that concrete remained under compression or minimum tension, hence cracking did not develop. Moreover, there was no reinforcement in the concrete which would corrode. Although I would say that lime might also play some role in durability of Roman concrete but not sure how significant it might be.
Hasan - Thanks for your comment. We must keep in mind that it is the deformations that cause the damage. Materials with more deformation capacity have the ability to dissipate energy and ask for help from other parts of the structure before they fail. See my video on structural resiliency - czcams.com/video/5P3BZUDz-9g/video.html
Think of a paper plate and a glass plate. If a glass plate is loaded to its limit then it fails in a brittle manner. However, the paper place can bend a lot under the same load. This allows it to survive under a given load.
I agree that having structures under compression is also a great idea but this lower modulus is a concept that is used in a lot of materials to dissipate energy before it fails. Think of bending but not breaking.
@@TylerLey I agree that material which can deform more and has more toughness has the ability to dissipate energy and survive longer, that is why we provide reinforcement because concrete has low toughness and exhibits brittle failure.
However, in Roman concrete there was no reinforcement and we are left with concrete only. Concrete of lower modulus will not deform more, rather it will deform earlier but the total deformation for lower strength concrete will be almost the same as higher strength concrete.
We take ultimate strain of concrete as 0.003 which is same for all strengths of concretes. Therefore concrete of any strength has the same potential to deform i.e. 0.003 strain. However, higher strength concrete will reach this strain at higher load than lower strength concrete, thereby exhibiting greater toughness (area under stress-strain curve is more for higher strength concrete than lower strength concrete, for ultimate strain of 0.003).
Don't forget their water to cement ratios were multiple times less than modern concrete and they dense packed it in place, literally beating it into compaction. Also their mixes were much more closely monitored to maintain consistency from one side of a building to the next (which is a serious problem we encounter when we try to copy their arche and dome shapes)
In seawater Roman concrete creates aluminum tobermorite, a crystal harder than modern concrete. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself. On land everything was carried by hand, including the water for concrete. So they used much water than we do and thus their concrete was much dryer than ours. And grains of it were not fully hydrated. And if water enters through a crack it can react with those grains, which then hydrate - expand and thus close the crack.
@hasanshirazi9535 Apologies for reviving this 5-year-old thread, but I hope that, in the meantime, you have learned that concrete is a viscoelastic material. Low modulus materials are more resilient to volumetric instabilities (i.e. creep and the many forms of shrinkage) because they allow for larger internal strains before the material fails in tension and cracks. These microcracks then greatly reduce the ability of concrete to resist the ingress of water and/or deleterious chemicals. I know how complex structural engineering is, but you guys could definitely use a couple of materials courses...
More relevant reasons their concrete lasted thousands of years and ours typically fails within a century is their water to cement ratio, precise mix consistency, and completely different installation technique.
I wouldn't believe for a second it's an issue of precision. I would think we can much more accurately and precisely control the mix ratios with current technology. Nor would I believe it's a water to cement ratio. The people like this professor have had centuries to experiment with varying the two parameters of cement and water. There is very little chance that the magic behind Roman concrete lies in that combination.
@@nonconsensualopinion it's not a matter of speculation. We know what the romans did. They used multiple times less water and because they used domes with no mesh, their aggregate mixes had to be more carefully balanced so as to avoid uneven stress. Also they used higher quality pozzolans. It's not that we couldn't do that, but that we don't. No one wants to pay to dry pack their concrete into forms with mallets, so we use steel to hold our weaker concrete together.
@@nonconsensualopinion Everything was carried by hand obviously. Including the water for making concrete. So they used far less and their concrete was much dryer than modern. And grains of cement in it did not fully hydrate. And if a crack forms and water enter it can react with those grains and they expand and harden. Self healing up to a point.
In seawater Roman concrete forms aluminum tobermorite, a crystal harder than modern concrete. It can flex a little bit. And if a crack forms, the chemical reaction with seawater keeps creating tobermorite and the crystal grows, and heals itself.
how much of it has to do with vertical loads versus horizontal loads? They didn't use rebar, that makes it last longer or shorter for reasons we understand. Which or their structures did not last? I suspect it may be the ones that had more horizontal loads applied to them and could have benefitted from rebar. Of course I ablsolutely agree with your other reasons you presented, why some have lasted so long, climate being the most important IMO
Good question!
I think that would be a good thing to research. The existing structures are in areas with very mild climates. There are some sea walls in Britain that still exist but they are in the ocean and so they don't freeze.
An atheist, a Christian, and a Muslim walked into a bar. Why didn't they duck?
Bar Fight. Those macro synthetic fibers ganged up on the rebars and saved the concrete from cracking up……
Today I learned my body is Roman Concrete with enough vodka. Thanks for the life Protip :D
Yes, getting a friend to hold the drunkard while you hit him is one way to win a bar fight !
Gosh, I sure do wish I'd run across you before. Many of the things you talk about here we have addressed by streaming UHMWPE fibers into concrete. We just had our first fullish size test (8'x25'x0.5' panel) and you can see it on TNSRsys.com/prototype. There are lots of advantages. Do you think we can edge lift 8'x40'x1' panel? Without steel. Coming soon....
Hello, I keep coming back to track steel in my question as what would work cheaply for rebar. When I was growing up around here there were a myriad of small marine railways that went out to low water. Then a cradle was lowered out at high tide to submerge and let boats run on to them. Once on they were chocked and a winch drew them up into the shop where work was done. The point is this is another case where steel rails were submerged in salt water twice a day as well as out in the weather for decades. Nary a sign of flake rust at all. A patina of rust on the non load surface was the most you'd find. Would not this formulation of steel be trick as rebar for long lasting concrete? I would love to hear a metallurgist chime in because it sure looks like a better answer than epoxy, paint, galvanizing etc that have been tried and failed. Would not be near as expensive as stainless or exotic alloys nor subject to crevasse corrosion etc. Take care. Doug
Sounds similar to blueing or browning steel. The oxide outer layer protects the steel within
@@mexital1159 As I recall, browning was done with salt, too. Good observation.
Oh My God My name is probably a Week Now
Can you say "curb stomp"
Sorry, but some of your stats are wrong. There are plenty of temperature changes and plenty of rainfall in some of these places
Thanks for the comment. What structure did you have in mind? Italy is in a very mild climate. It is very similar to southern California. There is a sea wall in the UK that is discussed but it gets cold but it doesn't freeze or the entire ocean would freeze. Keep in mind that temperature changes that our bodies respond to are not the same temperature ranges that impact concrete.
Good video and topic. However, the graphs are entirely useless. lol They only say the same thing you already say over and over, about time to harden, and the modulas. The graphs don't even have data points. Their just a visual representation of those same statements, based on no data. lol Anyways, I'm just nit-picking because it was funny to me. 🤣 But, good videos and topic. You seem to have alot of knowledge about concrete. Roman concrete and other forms of homemade concrete are very interesting and useful to me. I subscribed. I think I can learn alot from your channel.
I just write the question
The aqueducts are mostly stone...not concrete...
The weather in that region of the world is anything but mild from an ecological perspective. It is a ocean exposed biome, that is highly tectonically active...and the reason "natural cements" didn't need reinforcement was because of the way it was build with and understood...Reinforcement simple was not (is not!) needed in the modern context. So no...these where not "great environments" at all to build structures...no greater than many other places. I was the material itself and the craft of designa nd application...not the biome.
As for your point many didn't last...???...That is rather moot...Many structures don't last. However by comparison, the vernacular forms out last the modern by significant margins...including in the world of traditional geopolymeres, limecretes and natural cements...
We "choose"...!!!...to use steel inside our modern concrete because of politics...not best practice...that is a choice and not a pragmatic or logical one, but rather one of greed, sloth and consumerism within today's normative cultures...
It was difficult to listen to many of your comments about "need for speed" which sounds more like an advertising campaign for the concrete industry than it does actual understanding of architecture and its impact, not only on society at large, but the future health of this planet that concretes hold over a quarter share in destroying.
The videos tonight that I have had to watch because a student shared them with me is the disconnect between an "academic" that seems more concerned with promoting a material rather than really learning the full impact and realities of that material. I don't know yet? Perhaps you real goal, long term is to bring back "good natural cements" which I could support both architecturally and ecologically...but somehow I don't think that is the case...
puzolian! volcanic fly ash! elbow grease!
Considering the curing time of concrete (if that's the correct word) I wonder if you'd be willing to discuss in a future video the possibility of using cements that absorb CO2 as they cure?
Ideally, from a global carbon perspective, we'd want the cement to absorb more CO2 as it cures than was released in the entire production process. That would make conduction industry a boon to the planet rather than a problem.
Is this even feasible? I'd love a professional perspective on this issue.
Warm regards
You said you guessed they didn't open it for a year, this isn't the right reasoning.. you mentioned lack of corrosion, what about the Roman concretes standing in the ocean being hit by waves and salt millions of times more then out concrete
Modern concrete would have no problem with waves and salt water if it didn't contain steel.
I don't understand your first sentence. It was common knowledge in Rome that concrete gained strength over time. They left their concrete roads empty for at least a year before using them. We don't do that with modern concrete.
@@TylerLey ah you sounded like you were making an educated guess over fact about the curing time of the concrete, Maybe I misheard - it's early here and alcohol is still in the system
We do also have concrete additives and curing methods to further strengthen the concrete, eg. Watering it for up to a few weeks after, different aggregate sizes.
What about galvanized steel? Would that be any stronger when exposed to water / erosion etc? Aren't there theorys about the substances they used in concrete that are lost today?
Sam,
You are right! We have lots of tricks to tailor our concretes today that didn't exist before.
I love galvanized rebar! It is better than the normal rebar that we use but it will still break down and corrode. I talk about it here: czcams.com/video/xVDy84rR5Z8/video.html
Roman concretes are different than what we use today. They used lime and volcanic ash. Today we use portland cement and fly ash. Fly ash is man made volcanic ash. The Roman concrete may be better at resisting cracks but modern concretes are more consistent, gain strength faster, and can be designed to have long lifespans. It just depends on what you want your concrete to do and what you can afford.
Thanks for the conversation!
@@TylerLey thanks for the replies and the information / informing me 😁
I ignored u 7 times for this thumbnail
Why this video looks like it was made ten years ago 🤔
Not sure,
I have upgraded my camera since then!
eh.
I say England's greatest prime minister was Lord Palmerston!
Pitt the Elder!
England's greatest PM is one thing, but actually the greatest thing about England's Prime Ministers is that not one of them were Donald Trump.
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has the bar fight started yet?
Did European people *forget* how to make concrete after the Western Roman Empire collapsed or was there no longer the infrastructure to support cement production?
Both. The secret to Roman concrete was a closely guarded secret: volcanic ash was the pozzolan that made Roman cement different from the soft lime cements that everyone else knew about. When the Roman empire collapsed the few people who knew the secret no longer had access to volcanic ash and no one made a comparable cement until Portland was discovered in the 19th century
@Brik Tearz World yep, just like making the best pizza in town doesn't mean you know how to run a business that doesn't fail.
Both, plus a third thing: due to the difference in Imperial building projects and those that immediately followed there was no longer the desire to build such huge structures.
That reason logically and actually came before both the points you mentioned: it explains why the skills were not maintained, and why the industries to produce the material went out of business.
Stop using "harder" when you mean "more difficult "
Harder means too much else talking about materials.
I use a lot of analogies when I am speaking extemporaneously. I've come up with some odd ones over the years that raised a few eyebrows and got a few uncomfortable laughs. This "bar fight" analogy is the *absolute worst* simile for concrete elasticity. The basis for your analogy is based on movie scripts (See www.TVTropes.com ) and not reality.
I'm sorry you didn't like it. Have you seen two drunk people fight? Maybe you have to live it to get it.
@@TylerLey Fine, you can stick by your analogy, if weakly. But at least give my comment some thought in 5, 10, 20 years... when you re-watch this video and cringe at your choice of comparison logic.
Hmmm.. maybe it wasn't the bad analogy but the terrible delivery? Could a comedic tweak have made it more palatable? Perhaps the entertainment value would have helped.
uruiamnot Perhaps you have too much time on your hands, or you are a secret entertainment critic . I’m sure the good doctor will be wincing about this subject topic in 30 years........sure
Calm down
Your speculating based on your oppinion as there are breaker walls in contact with the sea in England still standing.
As a builder (not a reader of) Roman comcrete are far more durable than present concrete used, the reason we don't use it is that Roman concrete is more labor intense. Also I dont believe youd do well in a bar fight with your knowledge, that too requires much hands on to know what works, theory is for non doers-self proclained "teachers" that teach bad practice and offer bad advice.
you do sustain as much damage BTW ,you simply are too drunk to care and you dont register pain as much when drinking, hence drinking before surgery prior to modern medicine. Your welcome if your not too proud of your paper, if you are sorry for wasting my time to offer sound, practicle exp regarding your bunk theorys that are barely more than fanciful thoughts that don't really apply outside of talk.
John,
I agree that I don't know for sure why some things fail and others don't. However, those Roman walls in England don't contain reinforcing steel. Corrosion of reinforcing steel is a weakness of modern concrete. If we could design them without it then that would greatly increase their life.
Materials with a lower modulus experience less stress than a material with a high modulus for the same deflection. This is a truth that is a widely known.
For example, compare a serving plate made of glass versus a paper plate. You can deflect the paper plate a lot and it doesn't break. Is the paper plate stronger than the glass plate? No, it has a lower modulus. This is the concept that I am trying to teach.
Let's say you are going to be hit by something. In one circumstance you tense up and in the other circumstance you are relaxed. When you tense up your body will take more damage and you will feel more pain because more of the load is transferred to your body. If you are lose then your body will give when you are hit. The force is dissipated as you give and less of it will transfer to you.
This is why we have bumpers on cars. It crumples and gives when something hits it. This is why we design our structures that will see earthquakes or bomb blasts to give and not be too rigid. Think about it and let me know if it makes sense. You seem to have lots of experience. I bet you have seen this in your life.
Tyler Ley heres a begining beyond the I dont know (link below) bit you would know if you knowledge base was not theory.
czcams.com/video/R9sZSrhoPJY/video.html
@@TylerLey Then why nobody is putting stainless steel in the concrete to avoid corrosion?
Stainless steel costs about 6x more than normal rebar. There is also not enough stainless produced every year to supply enough to replace rebar. I have a recent video where I talk about it here: czcams.com/video/1ELHzXuwdqg/video.html
Why was rosendale cement mixed with portland cement to build roads to make them more durable?