Was Roman Concrete Better?
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- Опубліковано 28 жов 2018
- Comparing modern concrete to that of the western Roman empire.
Errata: “More viscous” should be “less viscous”.
More Videos About Concrete:
- What is Concrete? ( • What is Concrete? )
- Why Concrete Needs Reinforcement ( • Why Concrete Needs Rei... )
-Does Rebar Rust? ( • Does Rebar Rust? )
In this video, I discuss a few modern techniques that help improve design life of concrete, including roller compacted concrete (RCC) and water reducing admixtures (superplasticizers). There are a whole host of differences between modern concrete and that of the western Roman empire that I didn’t have time to go into, including freeze/thaw damage. This is such and interesting topic, so here are some references if you’d like to learn more:
-www.romanconcrete.com/
-www.usbr.gov/tsc/techreferenc...
-en.wikipedia.org/wiki/Roman_c...
Watch this video and the entire Practical Engineering catalog ad-free on Nebula: go.nebula.tv/practical-engine...
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When you accidentally buy too much concrete so you keep making videos about it to use it up
as a real engineer would do.
Always check the size when buying online lol
@@cseblivestreaming8073 Also remember to check the units of stuff when buying online... Friend once bought what he thought was a 10kg sack of rice online one night (while drunk), not realizing they weren't sold by the sack, but by the pallet...
As a side note, sacks of rice will double as surprisingly cozy bean bag chairs if you have enough of them piled together.
RealLuckless i really appreciate this conversation
Accidentally? What if the next smaller batch was too small? Also you never buy just enough of something else you run out guaranteed.
There is also survivor bias : all cheap roman buildings are long gone, leaving only those that were considered critical infrstructure, which the Pantheon certainly was to the romans. It means they should not be compared to any regular modern building, but rather to what we also consider critical infrastructure we need to be as sturdy as possible.
This is a good point. Unluckily not only cheap buildings were lost trough history, for centuries people used roman ruins to salvage materials. So we have even less examples to compare to each other...
Also drive some trucks over the Pantheon dome and see how it looks in a year. It's not actually doing anything except resisting rainfall.
There is that but they are also 2000 years old, who knows how long those bulidings stood, 10 years, 100 years, 500 years? we haven't built anything with new concrete science that has survived 500 years yet.
@@wierdalien1 But we have built buildings that did not survive till their internal works have been finalized.
Most structures during the Roman empire were built by slaves, knowing that makes it less impressive.
There were findings published yesterday, by MIT and others, that the ancient Romans used a practice called "hot mixing" wherein they directly added quicklime to the concrete mix. This resulted in "lime clasts" which gave the concrete self-healing capabilities, which researchers tested. It's neat stuff.
Intresting
I worked at a limestone mine/cement plant for years. There are recipes for great cement, they just aren't price effective for most applications. I know they had a recipe for cement so strong it didn't need rebar. They had another recipe with silica that would harden underwater and was mainly used to fill exhausted oil reservoirs. Both were 4 to 5 times the cost of average cement.
Some of the critical concrete the romans made also used ash instead of aggregate rock so it was very strong and water resistant but also very expensive.
@@RARufusConcrete is cement with limestone filler, and sometimes added gypsum for quicker set times. So saying they used ash instead of rock is an ignorant statement. They use ash in modern day cement. Modern day ash comes from coal power plants, as a by product from the coal burning process. Same with synthetic gypsum vs natural gyp. Modern day cement plants use both types of gypsum, depending on price, availability, and region. The only difference between roman ash and modern day ash is the romans used volcanic ash. It didn't have magical properties. They primarily make lower quality cement these days because it's cheaper and keeps construction companies in business. They do make high quality, it's just expensive and not as in demand.
I’m sorry what? Used to fill exhausted oil reservoirs? Romans didn’t have oil besides wale oil
He said civil engineering, career what does he do?
Also, they cure much slower. Many project have time constrain and can't wait forever.
The roman"s concrete certainly cemented their place in history
carlindelco 🤣👍🏻
@Built To Rule lol
10 points.
That's quite a *solid* pun
@@zachnerdydude6605 lol
No one does it quite like the Romans did, I can speak from experience... just saying.
when is the bible 2 coming out
9x19mm it a work in progress after all Rome was not built in a day.
@@maxineclark2399 The world was created in 6 days though, so how long can one book take?
@@romaliop smh jesus be lacking on his book releases
Nailed it Jesus!
I’m glad that you used recipe for design mix. My wife was a Civil Engineering student in late 1960’s. She was taking a test and couldn’t remember the term “design mix”, so she used recipe. The professor announced to the class that you can take a woman out of the kitchen, but you can’t take the kitchen out of the Civil Engineering student. She got full credit for her answer.
lol I thought this was gonna go the horrible-misogynistic route. So glad it didn't!
1960 wow she must be less young now
@@Economic-_- from now on, i am going to use this phrase as opposed to "you've aged"
@@chrisr4023 me too
@@chrisr4023 this video has become less young now
“concrete reinforced with steel bars is the foundation of our modern society” ugh. civil engineering puns. … subscribed!
This is what qualifies as wild & racy humour for civil engineering haha
@@ophidahlia1464 like crazy engineers cutting corners to build something the fastest? 👀
@@lildvsvevo no. Nothing like that.
7:36 "Anyone can design a bridge that stands, but it takes an engineer to design one that barely stands."
Haha! Best line of the video!
Thanks Grady!
Safety factor 1.01!
@@jaquigreenlees: To be fair, that's probably not the intended message.
@@jaquigreenlees it's not designed to fail, it's designed to barely withstand the worst of nature and humans for a specific number of years. Anything above that would be a waste of money and resources.
As a Union Concrete Journeyman this is so true but so easy to forget. It was a good reminder hearing it.
@@ravinderkhakh3918 True, anything above that would be a waste of money and resources, but what if the error margin was miscalculated? Then you get incidents like the I35 bridge in Minneapolis.
My friend's grandpa build few concrete garages near his summer house (Russia). For one garage he used some chemicals to make concrete very tough. Because he just could. Very soon he undestood problem when he decided to make new ventilation hole. Concrete was so strong that it was impossible to drill. In Soviet times we didn't have powerful hammer drills, so he broke some drilling handheld instruments and gave. Next garage (he really loved to build) he made of normal concrete.
Could it be sodium silicate (water glass) dissolved in water and slaked lime added to form calcium silicate? Or could it be liquid sodium silicate and liquid caustic soda (sodium hydrooxide) and akuminum carbonate pre-dissolved in water and all are mixed-dissolved to form a kind of geopolymer and added to the concrete mix? The key is mixing a water solube silica source and water soluble aluminum source and mixing in caustic soda (sodium hydroxide) and mixing-dissolving them all until they have inter-reacted together thoroughly into a quick setting geopolymer, which is then added to concrete.
@@darthvader5300 I seriously hope Mechanical Engineering involves all this chemistry.
I say it was the tools/drills...I got some concrete walls, that I simply cannot drill with western drills...I gotta get my buddy to come over with his oldschool east-block drill...goes in it like into butter...
lmao, your friend's grandpa accidentally crafted bedrock.
A lot of German bunkers built during the war are like this. They're so strong they couldn't destroy them afterwards without using very expensive tools or high explosives, so they just left them or repurposed them.
Beyond design life, there is also the fact that our infrastructure isn't meant to last anywhere near as long in the first place. We regularly take down highway overpass because we have decided that we need to widen the highway. We demolish skyscrapers to replace them with an even more taller skyscraper. Our infrastructure very much fits within our throwaway society.
So what is your answer to the problem? We should always build our overpasses much wider than they need to be. Just in case there is more traffic in the future? Or should we never expand them if we get more traffic?
You *really* wanted to make a salient point capitalistic overconsumption didn't you
@@neilkurzman4907 We definitely to need to plan for the future, but it doesn't have to cost huge amounts. Tools such as land management can go a very long way. As it is, our north american towns are not being managed in a sustainable way. We also need to take on NIMBYism head on. Densification would go a long way toward reducing the amount of infrastructure we need to accomplish the same goals.
@@jonathanlanglois2742
Americans don’t like being told what to do. And they don’t like spending money and less they directly benefit from it.
And they want everything that they find offensive in somebody else’s backyard.
So yes what would be good for the country is unlikely to happen.
@@neilkurzman4907 I'm seeing the first few fights along those lines in my own city. Land available for development has mostly already been developed. Peoples don't realise that rent is going to get very expensive very quickly unless they compromise and stop with that foolishness.
The city isn't going to allow all that many new streets to be built because they can't repair streets on a 20 year cycle as it is. The city knows it needs to get more tax dollars from it's existing infrastructure and that's going to come through higher taxes, or densification.
“We’ll have to wait 2,000 years to see if today’s concrete holds up to the Romans.”
Took only 40 years in Florida to tell us that it certainly does not!
Jesus fuckin christ dude lmao
ouch
Shit🤔
Facts
"Building constructed by Florida Men lasts a fraction of the expected lifetime."
I like that idea... "Anyone can design a bridge that stands, but it takes an engineer to design one that barely stands."
No where more critical than in formula 1 racing where weight is critical and failure is not simply if some component fails before the race is over but also if it can last two races.
@@jonwatson9765 I wonder if this is the case anymore now that gearboxes and engines have to last a number of races and grid penalties are incurred for changing to new ones too early.
@@colinbaxter1022
Is this a new thing in racing? It sounds like improvement, so people don't just use very effective but very damaging techniques to squeeze out power. An engine should be powerful because it's been designed that way.
I was caught up on that too, and checked the comments to see if anybody else was too
@@kindlin It's been creeping up over the years. A couple of decades ago, they used to go through several engines per race in Formula 1. Practically single-use, disposable engines. Then they gradually imposed tighter and tighter restrictions, until now it's a handful of engines per year. The same with other key components. The aim is to keep costs down. Especially because, back then, they used relatively simple, naturally-aspirated gasoline engines, whereas now they use incredibly complex and expensive turbo hybrids.
I'd never heard of superplasticizers until now.
Learned something new. Thank you !
It's a common civil term Mr Kevin
That stuff is magic! I have no idea how such little powder could do that.
I wish I'd known that when I was patching my driveway. The specified amount of water made it too dry to work with a screed, let alone float, so I ended up adding much more water although I knew that would weaken it.
I’ve been waiting for Home Depot and other hardware stores to catch on for years, no one I’ve ever talked to around here has ever heard of it. I have to encourage employees to check it out.
First heard about years ago when researching concrete tables.
There is also silica fume that is really useful in increasing strength, another way to improve strength to create a extremely high strength concrete is to use cutted granite block as coarse aggregate and align it into square lattice covered by the mortar mix.
"You don't use volcanic ash in your concrete? Bah! How primitive!" - Ancient Rome
And wasting all that fresh water? We use sea water!
@@duudsuufd wait we don’t use sea water in concrete? Why would we waste all that fresh water?
@@Cooldude-ko7ps Salt corrodes the reinforcement
I really appreciate your videos. As a construction worker, you explain the reason for things i notice but do not have formal education to know the inner workings. Keep the videos coming please.
Hypotheses are all well and good but I'm glad you've provided some concrete data.
I had to like this because it made me choke-laugh.
@Hubert Jasieniecki You seem like a responsible citizen, because the world is corroded with bad jokes
Ba dum tsss
I also would like to come up with a witty pun but i just Kant
I feel that this video has cemented my understanding!
i’m a civil engineering student at the university of maine. we spent several weeks on concrete this semester, and the professor mentioned the roman concrete, but she didn’t have time to elaborate on why it lasted so long. thanks for the cool video!
Poozolan
The minerals formed by the seawater made sections of foundations almost indistinguishable from the rocks it rests on. The water dissolved away certain parts of the volcanic ash, but deposited a lot of salts that filled the voids and then some!
My professor at the Colorado School of Mines had a short lecture on Roman concrete so we’d stop asking!
She didn't had time ? I guess you can find time for the marvel of western civilization.
lol “she” ... “professor”...
She didn’t mention it because she has no clue about anything that isn’t in the lesson book
That is no excuse and typical of most university professors. This only took a few minutes to explain. You should ask for a portion of your tuition money back. Believe me, I have seen many professors who have no real world experience. “Those who know, do. Those who don’t know, teach”
When I was a commercial roofer we would nail down felt to a freshly poured gypsum deck and were told when the nails corrode, it gives it more holding strength. LoL
I have put down a LOT of concrete in many different countries in my time, but I keep learning more and more watching your videos. I love them. Keep up the great work
Adding powder makes it wetter? what the heck!? That's awesome.
I know! I need to know more about this..
Right! It blew my mind😁
Is there another powder that causes the concrete to harden or do you just wait?
@@TasX Sildenafil
@@_BangDroid_in a nutshell it makes the molecules repulse each other magnetically
You don't have to go back to the Romans. In 1957 a contractor built a sidewalk near where I work; the date and name are embeded in a metal form into the concrete. This sidewalk is still in great conditions. They remade the sidewalk accross the same street about 10-15 years ago: now its full of cracks and heavily damaged.
A friend of my fathers had his driveway done 25 years ago, still looks brand new today. Not a crack, I would certainly say it's worth spending the money to have a concrete project done right, rather than cheaply.
@@billybobjoe198 There are some roads in Europe made of concrete. They're kind of shit to drive on because they are literally rock hard, but they do seem to last forever.
Thats about when crack became popular 📉😎📈
@@billybobjoe198 Well that thing with almost all modern products and items now. The people who make them realize that there is no point in spending the extra money to make things last forever if they are going to be outdated or obsolete in a few years. Therefore they charge you the same but drastically cut back on production costs. Whether it comes to tires, electronics, or even cookware.
For instance I am pretty sure realtors and construction companies realize that they can build a house that last 100 years with minimal repairs, but they aren't going to bother because their goal is just build a house that meets minimal safety requirements, so that they can sell the plot for as little as possible out of pocket cost to them so that they can reduce their financial liabilities and free up their capital for other projects. Not to mention it makes it easier for them to sell the house because it more affordable due to the often lower price tag. And often times new home owners might just decide to massively renovate the house after a few years anyways or have to renovate their house to meet update building codes.
@@armybear2 that is a big problem from consumer standpoint. I remember old chairs and table, they were a lot more comfortable (probably because of habits, though) and lasted much longer than ones i currently use (20 years of use and chair is fine other than seat being damaged by cat vs 1 month before chair leg needs to be regularly hammered back in joint). I'm unsure of price difference, but including inflation it should be more or less same.
I cannot read English, so I am grateful for the Japanese subtitles. This video is very interesting.☺
there are Japanese subtitles? o:
edit: I am now watching with Japanese subtitles and I don't understand a word of Japanese :'D
@@AximVidya I'm Japanese. These Japanese subtitles are naturally and easy to understand for me😉
I speak English and I'm still grateful for the English subtitles.
1920: "We shall have flying cars and live on the moon!"
2020: I'm watching a dude mix concrete.
We would have if bot for the lazy socialists and commies constantly trying to topple our country.
You forgot: on my handheld screen, transmitting data across the world, while im pooping with my feet on a heated floor.
Edit: priorities, right?
@@firghteningtruth7173 Nothing wrong with what you got, but it's debatable if your signal transmitting across the world is worth anything.
The heat floor while you poop though, that's $.
@@timothyandrewnielsen i was referring to the internet. Which, you seem keen enough to partake in. 🤣
Ur right tho. Heated floors are the shit.
My grandfather was a civil engineer in Wyoming in the ‘30’s. He had to guard freshly poured bridges with a shotgun to prevent the contractor from pulling the rebar! Also, when engineers built infrastructure then they planned on fifty year lifecycles, never imagining that politicians would gut maintenance and replacement funding in the name of cutting taxes, thus resulting in crumbling infrastructure everywhere in this country!
@@peterjszerszen I rather build something TO LAST AS LONG AS IT EXISTS so that no matter what happens, my descendants and their survivors are still able to use it even after I am gone. The ancient Eastern Roman Empie's slaked lime-powdered brick-river sand mortar, the ancient Western Roman Empire's slaked lime-pozzalanic sand (or an artificial modern version of it) river sand mortar, the British Smeaton slaked lime-powdered iron slage-clay powder mortar all have proven their worth.
Pozzalana volcanic ash sand mixed with slaked lime and water is added to create a pozzalan cement binder which is then mixed with broken rocks and sand. No pozzolanic volcanic ash sand? The use powdered fired brick mixed with slaked lime and sand and rocks. In Haigh Sophia they use powdered fired brick mixed with lime and sand and water to produce a mortar with a high tensile strenght as if it has steel rebars in it and has allowed Haigh Sophia to survive all these earthquakes for more than 1,500 years.
Pozzalanic volcanic ash sand are microscopic particles containing atomic holes in them where the slaked lime can enter and react with the silica known as silicon dioxide. One way to reproduce this effect inorder to create an artificial pozzolanic volcanic ash sand is to mix sand and sodium carbonate and limestone powder together in the right proportions so that the silica proportion is 55% to 60% and is melted and sprayed in a chamber where it will solidified into a powdery microscopic sand particles which is then treated with acid to leach out all non-silicon dioxide and non-silica component elements and is rinsed with water thoroughly and is dried and the process is repeated again and again until it has become a pure and powdery microscopic silica sand particles which is as porous as the naturally porous pozzolanic volcanic ash sand.
This new artificial porous pozzolanic volcanic ash sand can now be used as a replacement for the naturally porous pozzolanic volcanic ash sand by mixing it with an equal volume of slaked lime and sand and water to create a cement past mortar and rocks and broken clay and rock aggregates are added to create a brand new Roman concrete.
But they won repeat this experiments nor would they use these formulas. They only wanted to make a cement-mortar and cement concrete to last only for several decades (80 to 90 plus years) not for thousands of years. But for key criticial strategic structures like dams, aqueducts, naval ports, and others has forced engineers to build them to last for centuries. The Itaipu Dam in the Brazil-Paraguay river system was built of concrete designed to last for 300 years of continous, non-stop service!
@@darthvader5300 Thank you for this info.
@@peterjszerszen Look up the I-35 bridge collapse--people have already died of this, even in the states that spend decent money on road maintenance.
Theres plenty of taxes but it just gets wasted on dumb programs and unneeded wars...
@@peterjszerszen That’s a bit dramatic. Who will die and why?
My career has been dedicated to mitigation of embedded metal corrosion with reinforced concrete. I would be happy to do a video with you on repair strategies and best practices for extending the useful life of reinforced concrete.
YES! We want to know more! I like when I learn top-notch detailed stuff on UA-cam
Bro just paint the metal lmao
That's a video I would watch!
That would be awesome!
Titanic
Wrong. Look this up. It's actually a worse idea. All that green painted rebar you see on city highway projects that have since tested and found it to fail because water gets trapped under the paint over time and accelerate the rusting.
I've been making concrete deck piers without forms for years (80's). I mix a nearly dry mixture. Using a 16" segment of a form shaped like desired column, I tamp/pound the cement into the segment and raise it as I go like a slip form. You can go 32"-48" increments before having to let lower section harden a bit before continuing higher. If you do all your piers at the same time and skip from one to the next every 24", you never have to wait by the time you come back around to the first one. There are many tricks that enable you to do this in a narrow deep hole. This cement ends up being so incredibly harder. Years later, I would strike the side of a pier, it actually resonates like solid granite would, while any other would be closer to hitting lead.
This is awesome, I'm so glad people like you exist!
what is your recipe?
@@M-L450 Well, I never really considered myself having a 'recipe'. I always used standard Portland cement and mixed a 1-2-3 ratio (Portland-sand-aggregate), with the aggregate always being crushed granite, never eroded (rounded) river gravel. The amount of water is barely enough to moisten the mixture, giving it the consistency of feed grain for cattle mixed with molasses where it seems almost dry but compacts like a snow ball. The water becomes apparent as it is compacted. The water is added slowly, a little at a time with an aerating head attached to the water hose. I have only used fiber once when making dock piers for added strength against floating ice masses.
and you think it's going to last thousands of years? Give me A break
@@tonys4396 point out where they said they thought it'd last that long 😅
"Anyone can design a bridge that stands, but it takes an engineer to design a bridge that barely stands"
So true! I believe cost and profit are the strongest forces driving innovation in engineering
The other way of thinking about this is cost and profit cause corners to get cut. So you have shorter lifespans and more shorter term failures. Like how most infrastructure in the US is in varying levels of disrepair, on the way to collapse or has collapsed.
You could drop "innovation" from that sentence and it would describe the state of civil engineering in my area. I'm always baffled how they lag behind the time and don't want to spend time to find better solutions for their clients. It's copy-paste all day long. Granted, it's less likely to happen with more prestigious or high specs structures, but nevertheless, I find it sad that many people taking engineering aren't driven by innovation.
Hi, I am a structural engineer and English is not my native language. Term "viscosity" is very often misused by engineers, like in this case. For a long time the use of this term confused me. High viscosity does not mean soupy, but exact opposite. For example, honey at room temperature has high viscosity, and water has low viscosity. Viscosity is an inherent property of a material to resist flow. I notice structural and civil engineers very often misuse this term. I bet mechanical engineers are rolling their eyes every time they hear this :)
Yeah, I came to say this same thing. Not to take anything away from your consistently great series. But your use of "viscosity" is confusing.
As a ME I totally agree!
I think a better word could be fluidity. I'm not an english speaker either, though
+
Hi, this error in video also drew my attention while watching. It should be related to the word "Viscous"
I'm looking forward to the follow-up video in the year 4018.
I love your videos man. Thank you. I study these things on my personal time, because I didn't really have a shot at school the first time, and I don't have much money now. I don't think I could ever get a job doing this but I really like learning it and going to the library. But that gets so lonely alone. I apologize for sharing so much, but I really really really want you to know how great it is for me to have access to educational content.
Thank you as always for the video! I am always amazed at the little experiments you set up to demonstrate the many concepts you teach ppl about.
I can totally relate.i learned programming and electronics all by myself using online(mostly free) resources.i also don't know if I'll ever get a job in those fields but I sure like learning them :)
This channel is always official with the information, and the guy hosting it is really chill
1:17 LoooL thats a stockphoto that I've made. I never thougt it will find its way in this video ;D
Congratulations!
Look ma, he made it!!!!
It’s a great photo!
Nice!
Bet you didn't expect a person commenting with same cover photo on, as yours as well. And after one year..😂😅
I think a lot of people underestimate the advances in modern tech on basic things, and like to imagine ancient tech as some kind of mystical thing. In reality, Steel, Concrete, Metals, etc all are very large industries and the science understanding behind them is incomparable to oldern tech.
I also think people take for granted the engineering and innovation that make modern life possible
Yeah, then we end up with ancient aliens type of shows.
I really like documentaries/video, etc about the ancient world, and how they managed to do stuff with much less than we did. Like the roman water systems, building aqueducs, tunnels, etc, all to keep the water flowing at a certain angle to reach its destination.
Mystifying it really is pointless, imho. Understanding it is so much better, a bit like Feyman said, "It only adds"
@@USSAnimeNCC- It's easy to do when commodity items like mobile phones contain cumulatively tens or hundreds of thousands of life times worth of research over the years. From processors, glass, displays, user interface design, to radio frequency circuit optimizations... so much that it's easy to lump together. Then people talk about mythical old swords in the same way, as if the understand behind them is equal. It's a shame, but it's understandable because such vast amounts of information go into things today that it takes too long to fully grasp.
Maybe ignorance isn't bliss after all, just people forgetting history and ignoring science. We all know where that leads.
It's like the people that think Damascus steel is superior to today's modern steel. Hell no.
Practical Engeneering, the channel you didn't know you needed.
For some reason I can't put my finger on, this is the 3rd video I watched back to back and they're oddly satisfying. Not just when you blow up you test station, the air lock one -while missing any failiure - was nice to watch as well.
"That cement is there strictly for the weight dear"
-The Romans
Mackus the Gladius. Classic.
Buddy, I'm so glad I found your channel! I am already an engineer but just love learning more on all these sort of topics. Great content.
I love watching videos about how to avoid or stop corrosion on steel bars. Some people paint those bars with pure cement paste. Thanks for sharing.
I have been working in precast for about 15 years as a mould fitter and the rebar side of precast Thank for show and tell about concrete in your video's... Very interesting..
There's also survivorship bias: only the Roman concrete that happened to be of exquisite quality still stands, while the weak Roman concrete is long gone.
Good point, but on the other hand plenty of Roman concrete structures still stands, regardless the fact that Italy is active seismic region. Roman Concrete (the ground one) is poly crystalic, which makes it hard to crack. Plus we have Roman marine concrete, which last millennia, quality which we would like to replicate, at least partially.
@@lzw007 yes, and plenty of it doesn't still stand as well.
To say that Roman concrete was in general better, we have to compare a representative sample of all the concrete both still standing and the concrete that crumbled or was torn down; to all concrete made today.
Concrete made today and that happens to still be standing in 2000 years will also necessarily be the concrete that just happened to be excellent.
@@lzw007 Keep in mind that expensive architects/craftsman/supplies/maintenance went into buildings that were palaces/public gathering spaces/temples vs. say an apartment complex in downtown ancient Rome that I'm sure were whacked up by far worse trained craftsmen with inferior training/design/supplies.
That is very possible. They probably made important things out of good concrete. Like temples.
If the Roman bridge had trucks rumbling at 70km/h, it wouldn't be standing too.
Your channel is amazing. It's the best piece of entertainment from civil engineering that I'm studying and almost half my class watches your videos. Keep up the great work!
I gotta say I absolutely love the theme music to this channel.
I've read of recipes calling for volcanic ash to be used.
And the plastizers and low water is a game changer for my occasional small pour. Maybe can tweak my mix. Cool. Thank you for this video.
It is said that there are three certainties in an Engineer’s life:
Death, Taxes and Corrosion
Hey! similar profile image
counterpoint: antiaging, communism, and corrosion-resistant materials
@@wolfboyft I roffle'd at "communism." That White Sea Canal was great! 👍
@@pdstor what about it?
Elroy was here
Hey, Grady! Great video! Your videos are so interesting and educational. Especially this series on concrete. Well done, and keep uploading great videos like this!
Really good analysis and clear explanations. Next time I need a concrete repair will use less water and more compaction.
Thank you for a great video. I learn so much from your videos. Keep up the good work :)
I do concrete work and our infrastructure is no longer structurally sound after about 100 years. Thats why where i live all the bridges are being redone, because theyre coming up on that 100 years or so. But that is all reinforced like that you said.
I have also ripped out 100 year old or so stoops with my reinforcement and holy shit, it's like prying a boulder out of the ground. It is nearly impossible to break, even with jack hammers, you're just knocking agregate loose. Very tedious and usually has to come out in one piece.
Rebars that were pre-anodized before being coated with a zinc-silicon-tin galvanizing alloy was used by my country during the Cold War for certain key critical strategic MILITARY bridges and other infrastructures and buildings. Our military engineers then began to QUIETLY specificied marine grade structural strenght stainless steel (they learned it from the Swedes) in the 1950s and it is quite easy and cheap since we have vast deposits of chromium, nickel, molybdenum, vanadium, etc and we use argon-filled electric arc furnaces to make our own military stainless steel rebars and other marine grade structural grade strenght stainless steel military products, they even added certain rare earths so that they can be easily handled conventionally like carbon steels.
What bothers me is why these things are not in your western engineering textbooks surprises us on the other side of the Iron Curtain during the Cold War! It is in our military interests that all things must be built to last if war breaks out and we are unable to conduct maintenance after the war. But luckily no WW III broke out. But those very important infrastructures and buildings were never covered by your western mainstream media as if they are avoiding them. Maybe if they covered them, the western Europeans and other western nations will have their citizens asking uncomfortable questions that your politicians does want to answer in the first place!
I rather build something TO LAST AS LONG AS IT EXISTS so that no matter what happens, my descendants and their survivors are still able to use it even after I am gone. The ancient Eastern Roman Empie's slaked lime-powdered brick-river sand mortar, the ancient Western Roman Empire's slaked lime-pozzalanic sand (or an artificial modern version of it) river sand mortar, the British Smeaton slaked lime-powdered iron slage-clay powder mortar all have proven their worth.
Pozzalana volcanic ash sand mixed with slaked lime and water is added to create a pozzalan cement binder which is then mixed with broken rocks and sand. No pozzolanic volcanic ash sand? The use powdered fired brick mixed with slaked lime and sand and rocks. In Haigh Sophia they use powdered fired brick mixed with lime and sand and water to produce a mortar with a high tensile strenght as if it has steel rebars in it and has allowed Haigh Sophia to survive all these earthquakes for more than 1,500 years.
Pozzalanic volcanic ash sand are microscopic particles containing atomic holes in them where the slaked lime can enter and react with the silica known as silicon dioxide. One way to reproduce this effect inorder to create an artificial pozzolanic volcanic ash sand is to mix sand and sodium carbonate and limestone powder together in the right proportions so that the silica proportion is 55% to 60% and is melted and sprayed in a chamber where it will solidified into a powdery microscopic sand particles which is then treated with acid to leach out all non-silicon dioxide and non-silica component elements and is rinsed with water thoroughly and is dried and the process is repeated again and again until it has become a pure and powdery microscopic silica sand particles which is as porous as the naturally porous pozzolanic volcanic ash sand.
This new artificial porous pozzolanic volcanic ash sand can now be used as a replacement for the naturally porous pozzolanic volcanic ash sand by mixing it with an equal volume of slaked lime and sand and water to create a cement past mortar and rocks and broken clay and rock aggregates are added to create a brand new Roman concrete.
But they won repeat this experiments nor would they use these formulas. They only wanted to make a cement-mortar and cement concrete to last only for several decades (80 to 90 plus years) not for thousands of years. But for key criticial strategic structures like dams, aqueducts, naval ports, and others has forced engineers to build them to last for centuries. The Itaipu Dam in the Brazil-Paraguay river system was built of concrete designed to last for 300 years of continous, non-stop service!
@@darthvader5300 Military grade structures maybe, but so many other concrete structures in the old Soviet are crumbling away in stark contrast to the still standing medieval buildings ... Why doesn't western architecture use these modern materials?? Why didn't t the soviets on civil construction?
Of course we can see why Chinese bridges, buildings, their artificial islands are crumbling almost from the beginning, corruption and cost cutting.
@@darthvader5300 one thing that always gets a chuckle out of me were the anti air gun towers that the germans built around their biggest cities during world war 2. they withstood bomb raids, artillery fire during the later stages of the war and even after the war, with full access, the allied forces undertook several attempts to demolish them, until they gave up and just covered them under mounds of dirt.
another great example is the weißensand autobahn bridge, the bridge was bombed so badly there were craters in it so deep that an entire bus could disappear in one, but the structural strength wasn't at all compromised, after the war, the east german government simply had the craters filled and the road renewed and after west Germany annexed east Germany, they found that the bridge could still easily carry twice the weight it was originally intended to carry, so they added two additional lanes to the road on top.
this stands in contrast to autobahn bridges built after 1990 which require nearly constant maintenance.
cost cutting is not at all a factor, its 100% corruption.
structures like the weißensand autobahn bridge are examples of cost effective design, sure the initial build was expensive, but the thing survived WW-II, being barely maintained by the crippled economy of east Germany and even after all that, they still managed to add two additional lanes on top without any changes to the body of the bridge.
that is cost cutting and future proofing, sure it was expensive initially, but once it was done, little needed to be done to maintain or even improve it.
the reason why modern structures aren't built this way is simply that there are too many companies profiting from modern structures like this needing nearly constant maintenance.
@@jonwatson9765 We learn from our Soviet past which is why during the last few years of the Soviet Union we are in a hurry to upgrade or replace them entirely, and these are the things I am mentioning. The mainstream media only covers bad news but never will they cover good news with the same equal coverage they give to bad news. Curious isn't it. Or shall I say, suspicious isn't it?
Lesson learned after that first test, eh?
I had a cousin whose company did concrete testing. I found it very fascinating. Thanks for posting the video.
love this channel. and your naration and that you do not spam your sponsors on the start
Good god. You and your Concrete. it's like Wendover and his commercial airlines...
Can't wait for the Concrete Airlines crossover video.
@@BaronVonQuiply I don't know if that will fly over well.
Concrete Airlines
"Now lead-lined!"
OR
Concrete Airlines
"Our planes survive nuclear blasts!"
You probably typed this from a building made of concrete. Is it a cabin. No?... Then its a building made of concrete
@@patmaloney5735 Plenty of homes around the world are made of (ceramic) brick or wood and not concrete.
Great video. One thing to also point out: There isn't much frost wedging in Rome. Frost wedging destroys concrete like mad.
Make the concrete NON-POROUS by coating it with WATERGLASS that reacts with the calcium in the concrete and sealing the pores so as to make sure it is water proof and not affected by frost. That engineering knowledge is a traditional engineering rule of thumb among HIGHLY EXPERIENCE REAL OLD SCHOOL ENGINEERS! I saw some of them add a certain amount of waterglass (sodium silicate to a certain amount of water to dissolve it completely and added it to the calculated amount of water to be added to the mixture of cement-sand-concrete. That was in 1950, now that engineer is still alive and his handy work is still in good pristine condition. Keep in mind that the quality of portland cement used in 1950 is different to today's portland cement in the 1990s up to 2020.
@@darthvader5300 Interesting. My only familiarity with water glass is preserving eggs
@@FreedomTalkMedia I am an old school 93 year old mechanical engineer who also worked with civil engineers when we are constructing military factories and military public utilities inside mountains for making machine tools (and all kinds of factories later on) and I also specialized in machine tool engineering and I also make sure that the foundations of the factories we are building are "OVERBUILT" many times their required engineering specifications and standards. And before they started using blast furnace iron slag as a concrete additive we are already using it to repace sand and mix it with the cement we are using. When they use blast furnace iron slag powder as an additive to the tallest skyscraper in the Middle East that makes the concrete as hard and as tough as cast iron, we are already using it as a sand substitute in powdered form which is as fine as bleached white flour and it will dissolved in water just as the cement binder will dissolved in water, then we add mica-free gravel aggregates and zirconia fibers to make sure that the gravel pieces will not accummulate at the bottom when they are vibrated with vibrators to make it free of air bubbles inorder to densify it. Then the zirconia fibers were replaced with zirconia stabilized glass fibers and then replaced with yttria-stabilized zirconia stabilized glass fibers that can withstand the alkaline environment of all kinds of concrete and all kinds of cement-sand mortars. Soil tamping and using gravel under layer and using double-shell rebar reinforcement with expanded metal mesh and all connected together by mechanical clamps of all sizes and kinds. Double-shell rebar reinforcement that goes in 2 directions in a crisscrossing grid 90 degree pattern at the bottom and at the top of the concrete slab while having a 1/2 to 1 inch thick concrete layer to stand between the steel rebars and the soil and the surface top of the concrete slab. The rebar has to be 1 inch thick and 6 or 8 inches apart and mechanically secured together with a mechanical clamp bolting them in a crisscrossing grid pattern.
@@darthvader5300 how does this fair with acidic environments?
@@mpers Depending on the admixture pre-dissolved and pre-mixed with the water used in making these specialized concrete. These admixture is either a mixture of equal volumes of water glass powder and slaked lime or rice glue powder and slaked lime. The rice glue powder is added to the water at a ratio of 13 parts by volume water to 1 part by volume rice glue powder, added and mixed and heated to boiling point until completely turned into a watery rice glue water and allowed to cool to a gentle warmth just like your glass of warm coffee before adding the slake lime powder. This is an ancient Chinese formula in making the nearly indestructible ancient Chinese mortar for the Great Wall of China.
Would be exciting to watch your take on even more exotic constructions like the concrete used in Giza or the stonework in Baalbek
What concrete structures in giza?
@@randybobandy9828 used somewhere in or nearby pyramids, can't remember
Kudos to these awesome and very easy to understand videos! Learned a lot and appreciate concrete processes and properties
❤️
Which modern buildings are more likely to survive 2000 years? I guess it would be nuclear power plants, dams and some crazyass military stuff. Definitely not bridges and skyscrapers.
I bet some bridges will be okay. The Arlington bridge comes to mind.
I'm curious about certain steel structures like the Pennybacker bridge, or the Golden Gate. They're easier to maintain and keep painted.
Bunkers are basically protected under the earth
Depends on how much maintenance is done and how long its in service for I would imagine
Perhaps launch pads and runways.
@@Dr_Xyzt the golden gate bridge will only survive as long as it can be kept painted
That plasticizer is INSANE!! That's seriously an amazing invention. Can you tell us what's in it and why it works?
I always want to know "HOW".
One thing it's used for is concrete countertops, so it can flow, be smooth, and still be strong. It's relatively common even if most people don't know about it
Unfortunately ,,,,,,, that is a well guarded secret . I have been trying to get it for years . I have researched bonding agents , anti-hydro , (concrete poured into water) , and no way is the formula available . Ever hear of Greed ?
Love your content man! Keep it up!
Loving your vids. A good mix (pun intended) of science and general info
I love these concrete series! Thank you!
Romans be like: "What? They put steel in concrete? But why??? You can't fight and conquest your neighbors with steel if it's in a concrete!"
Conquer - the word is conquer.
*puts down sword embedded in concrete block*
y-you can't?
I'm starting to wonder if Excalibur could have been taken out if it was in a concrete block rather than a rock :)
@@ObsidianParis I've got a pet hypothesis that the story of a sword being pulled from a stone is an allegory about Iron Age smelting. The society that could learn how to turn rock into weaponry could dominate in melee combat and sword-based diplomacy ("be king" over the neighbors who could only work native metal and bronze).
Next, we fight with light.
Omg I love these historical engineering videos! Can you do one on Incan stone masonry please? Trying to figure out how Cuzco was built is mind boggling.
Thank for this videos, your videos are replacing my construction teacher at college. Regards from Aguascalientes Mexico!
Not necessarily, they just used more in a different way because it was easier/less energy intensive than mining ore and forging metal reinforcements for long unsupported spans. Concrete grade depends on the application and how much $ the builder, owner, whoever wants to spend. There a minimum code requirements that serve to ensure that concrete structures last a certain amount of time, but not indefinitely. You can go beyond these requirements and make super strong concrete comparable to or stronger than the sea water and ash mixture used by Romans, by simply adding more portland cement and aggregate. If the bridges, sidewalks, etc. are breaking to pieces where you live, it's because those allocating resources for infrastructure development are signing contracts with the lowest bidders who do shit work (like placing steel reinforcements too close to concrete faces, leading to corrosion and concrete failure - yes, this is preventable), and adhering to only minimum code requirements (if at all).
He does touch on this at the end.
Also I think there is much more salt thrown on concrete now than there was back then.
Agreed, I bid on not only government jobs all the time but other corporate ones and they always only care about the lowest bidder, even if my work is better or includes more it doesn't matter because the only thing that makes it from the secretary calling around to the big man making the decision is the price. Oh and im not talking construction work but it doesn't matter.
@@josephnmn146 The lowest so that they can embezzle whatever's left, or a higher bid with a conflict of interest.
Neoliberalism. We want a society, we just don’t want to pay for it, so we will give it to the deregulated lowest bidder with relaxed standards of practice or safety because that’s just troublesome redtape apparently, you pay for shit, you get shit. 50 years has proven exactly that
Great video, I’m a civil engineering student and these videos are inspiring. Thanks again
I really like the ending of your video where you explain the duties of the engineer. I've seen many freeways move over time like rivers. Traffic changed so greatly in my city in two decades it didn't make sense to save all of the old roadways. I guess it's a good thing they were only built to last 20 to 30 to 40 years. Thanks for this fresh insight!
Have you ever seen a "Roman road"? This is a 2000-year-old Roman road in Spain that is used to move cattle between summer pastures and winter pastures. The Romans had a lot of skill, for example on one side of the Roman road they put stone posts or monoliths every 50 meters, so as not to leave the road if it was covered by snow : ua-cam.com/video/YBM-p0uNxk0/v-deo.html
@@TheMariepi3 I've trampled all over Rome, Koln and Berlin. There are ancient roads everywhere, most of the are shut to modern auto traffic. Many are open to scooter traffic but that illustrates my point.
Super.
Being an Engineer, I was also looking for these answers.
Thanx❤️
Thanks for this look into the Roman stuff.
The Romans used sea water to help cure the mortar plus the crushed lava which produced the phillipsite and al-tobormorite after about 10 years. The secret is that it bends rather than shatters under stress. With lime like cement it can take years to stop curing, up to 7 years. I have also added molasses to keep frost at bay as used in India.
The longer it takes to dry the harder it becomes, the lime putty mortars have a bit more give and are 'self-healing' which is why you can see some great slanting buildings like the Crooked House Pub in Dudley, England. It also absorbs carbon dioxide and has great acoustics than cement.
There's also a very heavy survivor bias.
For the uninitiated, the bias goes like this:
During WWII many planes were being shot down, so armor was to be added in the most important parts. So they started logging every bullethole in every returning plane to log where the planes got hit the most. They determined thevmost hit areas were the wings and tail.
They armored said areas but planes kept going down. How could this be so! They were armoring every single sq inch that planes got hit in! Baffled they went back to the drawing board
Then someone postulated that maybe, hits were distributed evenly, and that they could try armoring the areas that remain un hit in the returning planes. Said person theorized that no plane returned with hits in the cockpit or fuel storage areas because a hit there would cause the plane to go down. therefore creating these "missing hits"
Desperate, they tried it and immediately they saw more and more pilots returning to base safely.
This is the survivor bias. they saw the bullet holes of the survivord and thought "this is why planes go down" instead of "a hit here is not fatal, but that area with no survivor having a hit means that it must be vital"
Now, we see these structures and compare it with any old building from today. However, these building are not any regular buildings; those are the building that survived.
i had always wondered about this. thanks for the good video
4:10 sick reading bro. I need to get into the second edition I have so much reading ahead of me.
8:13 that's a bridge in Zaporizhzhya that has been in construction since 2004. I guess some structures are meant to stand for 2000 years and some to be built for 2000 years.
Good video btw.
Dat baburka feel...
@@comradawsum :) yeah.
Sheit! You stole my joke!
Well done though)
24pavio, it all depends on how the building contract is written and enforced. The first time I heard two industry execs talk about a certain construction company as "They make their money standing around." it boggled my mind. But there used to be a tendency to reuse old building contract texts which did not specify penalties for not completing work on time. In many places this changed since, I believe.
THANK YOU, I was looking for the name of that bridge and the dam from 4:38 because they looked interesting. Such a bad luck they didn't finished it :( we can always look for renders and dream
4:39 I knew I recognized that site! That's the Taum Sauk Hydro Power Station, out in Missouri. That swath through the forest (top left) is from when the previous reservoir failed, spilled 1 billion gallons of water. Luckily no one was killed.
The Peterborough Lift Lock, when opened in 1904, was the largest un-reinforced concrete structure in North America. Still standing and being used for it’s intended purpose 100+ years after it’s opening. 😁 I’ve been through a couple times by boat. R. B. Rogers was a pioneer in concrete, was recognized by both the American Society of Mechanical Engineers and the Canadian Society for Mechanical Engineering. He also used in-reinforced concrete in the conventional locks he designed. Peterborough, Ontario, Trent-Severn waterway. 🇨🇦
I find this channel very much interesting and highly valuable to me, thanks author! (I am no engineer or construction worker by far..)
At 5:00 you mean less viscous. Adding water decreases the visocity
this
@@caesar2164 This?
@@cpoup046 I wrote the exact same comment, before seeing you'd written this one. So I deleted my comment, and noted that I agreed with you...
Yeah, what the heck is he talking about? I caught that too.
@Dr. M. H. Wut?
This man has given me an appreciation for concrete that I never thought I'd have
Thank you for sharing this information and your knowledge
I was in Las Vegas recently and visited the Hoover Dam. During the tour, we were told that some of the concrete on the inside of the structure STILL hadn't cured! I was hoping you might consider doing a video on that. Thanks for all the new knowledge!
That's also an important factor Grady didn't mention - the strength of concrete depends a *lot* on how fast it cures! Slow-curing concrete can be much more durable, but it of course takes much longer to reach that full strength. Roman concrete took many years to fully cure - a duration that would be wholly unacceptable for most modern structures. We actually can use such slow-curing concrete today; I recall seeing one structural report from a Buddhist temple in Hawaii whose design requirements involved "should be able to last a thousand years", and they used an *extremely* slow-curing concrete to pour the foundations. But for most applications, you need your concrete ready to take load much sooner, especially for constructing really tall structures that require lower layers to be solidifed enough to support construction of upper layers!
I believe that's a misunderstanding. The Hoover dam's concrete, *if* it had been poured the normal way, would indeed still be curing to this day. However, since they needed the thing done and in operation, they instead poured the concrete in "pillars" - smaller segments of much lesser total width & height, so that it would actually cure in a reasonable amount of time.
Climate also plays a role, Rome doesn't have the as many or as extreme freeze thaw cycles as other areas. If that roman architecture was in northern Michigan it would have crumbled a long time ago.
shoutout to cristina applegate
@@gregorylangsdale8277 eric andre
AND salt was rare and expensive. They did not throw it on their roads.
On the other hand in Rome it has to withstand significantly more earthquakes than in northern Michigan.
@@eljanrimsa5843 the us earth quakes are way bigger then the earth quakes in Rome.
I'm a landscaper and we sometimes use plasticisers in our mortar because it is supposed to add strength to the set product and I was never taught why it worked, this video explained it perfectly. Thank you!
I love 5he way you explained this to me.
Beautiful job
thanks for the lesson. I will adjust my concrete mix accordingly
Incidentally, while using the weight of the structure to keep everything in compression, I understand that the Parthenon (Pantheon? I always confuse these) used pumice for its low density to keep the weight as low as possible and that the dome gets thinner the higher up in the dome and the less weight it has to carry.
When building with blocks they joined the blocks with iron butterfly inserts, larger than the cavity but filled with molten lead the ductile properties of which presumably gave an added benefit.
Parthenon is the structure in Athens, Greece. Pantheon (Pantheon meaning "all of the gods" Pan=all theo=religion/gods) is the structure in Rome. Super easy mix-up!
Another reason might be that the structures we made today go through way more use ? using a bridge, i.e. having a huge number of cars using it daily is not the same thing as if it had way less usage. It literally contributes more to stresses within the structure that eventually degrade it faster :)
That's a great shot of the Taum Sauk Reservoir on Proffit Mountain @4:33 . The roller concrete dam is a replacement for the one that failed in 2005, you can see the scare in the upper left where the water scoured the forest down to the bedrock. I did surveys on that mountain.
This was the last place I expected Upper Stillwater Dam to make an appearance! Thats is gorgeous country, I love that area.
I think you forgot to mention one big reason roman structures still stand. The temperature practically never drops to 0 degrees celsius south side of the alps. Frost deterioration in combination with carbonation effect is the real reason, for big part of europe, why most of the concrete buildings need repairing after a few decades. As my concrete technology teacher said (i'm a freshman construction engineering student from Finland): Pantheon would have collapsed in a century at best, if they've had same winters as north of the alps.
And Rome's buildings were, by todays standards, way WAY overbuilt. Pantheons walls are 6m thick at street level, and it wouldn't be sensible to build that thick walls now days.
Jealous much? If the climate were different, the Romans would have built for those conditions,.
@@tonys4396 I'm having a hard time to understand where you found jealousy here. I merely stated some of the facts that effect in the longetivity of concrete structures, and how the roman concrete myth is just that, a myth.
@@PekonI24 Fact. Not myth. My degree is in Archeology. Yours is a GED. End of discussion
@@tonys4396 condecending very much?
@@tonys4396 plus if you really were an archeologist (AKA, a scientist), no matter the education of discussion partner, you would base you argument on something. Not just say that "I'm better than you, shut up"
I always use Portland Concrete when I'm mixing up a fresh batch of cement! :D
I always have a cement truck deliver the concrete to the pour site where i place the 'ment.
This video is so fascinating! Thank you!
I was delightedby the video! The information was provided clearly and understandibly - though that was, perhaps, at the cost of some valuable details about the difference between the chemistry of Roman cement and that used today.... next time, maybe...?
The Pantheon isn't the only example of ancient Roman concrete that still stands, you will find it all over the ancient Roman Empire, I've seen it in several countries.
Even in ruins that aren't preserved as the Pantheon, I'm always amazed by the condition of the concrete itself, how well that has resisted failure.
When you visit the Pantheon, it's amazing how perfect the building is, the engineering, the architecture and the symmetry are all breathtaking, modern construction is nowhere as precise, especially the finishing work.
Small injection here on the colloseum, its a hybrid structure made of lighter materials at the top and heavier at the bottom.
Very well illustrated and explained.
Great videos -- keep them coming!
Remember several years ago I saw a program about how they were using halved bamboo trunks as reinforcements instead of rebar, and if memory serves the result was superior.
They do that in India
The usage also plays a big role I think. The heavyest things they had are feathers to what we have today. A bridge from them was way shorter than ours today. They only needed to hold maybe a few hundret people at best but ours need to hold 1,000 of cars and trucks every day.
People can be surprisingly heavy. A dense crowd is a lot heavier than a line of cars.
I enjoyed this video, and you made a lot of good points. You did sprinkle in some humility and honored the roman ingenuity to a degree. I would point out, I believe we still don't have the roman concrete recipe figured out entirely! You did point out we may not have equaled it yet in some ways. I believe a similar story exists with the mortar in the great pyramid.
Hey thanks for the practical info .
4:32 if anyone's interested, that weird dam is basically a huge battery in the top of a mountain: it's the upper reservoir of the Taum Sauk hydroelectric power station. They pump water with excess electricity in the night and use that water to generate electricity during demand peaks. The dam doesn't get any natural influx of water.
That's very interesting! Where is the power to pump the water coming from? Can't it be stored at the source to avoid transmission and conversation losses?
@@ravinderkhakh3918 specifically in this case, not sure, but in general (this is not only done here) from excess electricity generation (more electricity is produced by nuclear/coal/hydro/wind than is used by consumers) during the less demanding hours (mostly in the night).
*EDIT* : Now that I remember, that specific dam it's just next (above) a bigger hydroelectric plant and it stores it excess power. So it's actually at the source. But in general, storing the energy right at its source would be logistically counterproductive in most cases. Batteries don't have enough density/affordability enough yet, and no energy storage system is unaffected by inefficiencies.
@@ravinderkhakh3918 i think because of the amount of power we're talking about , that only stuff like these gravity batteries or whatever they are called, are the only way to store THAT much energy. especially if safety is a concern. you've seen how cell phone batteries go up, now times that by millions of times.