 Okay. Let's go ahead. Okay. There is someone. Okay. There are a few joining now. Okay. Okay. Okay. Let's go ahead. Okay. Okay. There is someone. Okay. There are a few joining now. Okay. I hope on YouTube. Okay. Okay. Good morning everyone. Okay. Good morning everyone. Okay. Let's go ahead. Okay. Good morning everyone. Okay. There is someone. Okay. There are a few joining now. Okay. Okay. Okay. Okay. Okay. Let's go ahead. Good morning everyone. I am getting some info. Yeah. I think maybe in your own YouTube. Mute your YouTube. My YouTube is mute. Okay. Fine. Fine. Good morning everyone and welcome to another episode of Steamboat. So this is the second episode of our season two. And for those who are joining us on Zoom and YouTube for the first time. Let me introduce you with what we do on Steamboat. Steam. Steam stands for science, technology, engineering, arts and mathematics. And on the Steamboat series we bring you some interesting talks related to these fields. And these topics are mostly something very much relatable to our everyday life. And these talks are in different languages of English, Hindi, Marathi and other regional languages. And so you can check our Steamboat page for different talks in different languages. And our English talks also we bring later on in the try to bring them in the regional languages. So for more information on them you can check the link in the description to our Steamboat page. And so today we have Satish with us. Satish is a visiting fellow at Homibower Center for Science Education. And he works on chemistry education research. And he is interested in exploring the chemistry of materials and the nature around us. So today's talk is going to be in English. And so Satish, let's like today you're going to talk about this material concrete, which is one of the things we see all around in this urban jungle we live in. But we notice it's the least maybe. So maybe you can start. And our viewers you can put your questions on YouTube and Zoom in the chat box. So Satish you can start. Okay, good morning everyone. Thanks Vishal for introducing me and briefly the topic. As you mentioned, this concrete is responsible for urban jungle. And as you see in the slide left side is image of our own city Mumbai with various concrete caves. I mean houses of various shape and size. And yeah, I mean this is indeed a material which is marvelous in its own nature and we use it widely to build our houses. And before you go in, before we go into actual topic of concrete and its history and chemistry and some interesting stories about it. So we'll look around and see what other animals and birds build their houses of what they what the materials they use for building their houses just like we do currently concrete what others use right. I have show I'm showing you a few images of houses, labeled as one to six right. First one is on second one is a weaving birds and the kind is third is another kind of bird. And this is still sorry spider and termite house and base cave. So, can you name. Okay, so the participant, I would like if you can put up your answers in the chat box either in YouTube or in zoo, we can go ahead like I need you to put answers like what are the materials used to build these houses. What materials the animals are birds use for put down the answer in the chat. Okay. So, first one what are the what is the material aren't used for building houses building building their house. I mean mostly it is digging out something like soil. Okay. Okay. So, okay, so is there any other answer. So, no right now we are not having. Okay, okay, okay, okay anyway I will reveal the answers. So one is first one is sand or clay. Or dig houses made of this one and birds this house I mean this nest is basically made up of leaf fibers and grass and tricks basically small sticks. And the other nest is this particular nest is made of tricks or small sticks and some grass and and spiders this is actually a spider silk. So I know there's a reply some in the chat. Okay. Grass, silk, and mud for this one also and use old cave. Exactly. So, yeah, yeah, I want to be absolutely right. So, so interestingly the clay. Okay. Yes, I mean that is the he's saying that the fourth one is from the first team board session. Exactly. So that is, that's when that's where we began our steamboat. Yeah, yeah, right, right, right. So there's a there's a talk by Surabhi is about spider silk. And that's interesting talk one can go about go and watch this after this session and this is an interesting talk. The termites build their houses, build their houses using clay and termite saliva saliva is roughly I mean it's actually acting as a glue which holds clay here. And obviously bear uses a cave, which is mostly naturally occurring cave made up stone. Among these materials, can we build houses with using these materials which animals use or birds use can we do that. What participants say about it. You can put it in the chat box. What do you think can we make cover houses with any of these materials. Like silk or clay or twigs or small sticks or stone. Yes. Okay. So, which material one can use. Yeah, what material can we use for making our houses from these. Okay. People do make houses she says people do make houses with stones and mud. Exactly. Okay. So people use stone and mud to build houses and so was we as ancestors like our ancestry one ancestor was to live in naturally occurring stone caves. Right. Eventually they realize there are other materials one can use for building houses as so Graham right is mentioned. The first one basically say made of clay and second one is timber or food. And third one is beautifully made of glass and fourth one is stone and fifth one is an interesting like you might not have you might not able to identify what the material is made up of it looks much like any other material, but interestingly this is made up of plastic waste. was crushed, and then glued together to make walls for building this particular house is there near Mangalore in Karnataka. It is made up of plastic it is which is very important towards recycling plastic and reusing plastic right and bamboo and okay this is again rural South Indian people also construct their houses are like temporary houses based on coconut leaves. So this is one of the and among these materials again. So which is the most stable material to use for building houses like can we rely on these materials, any of the particular material. Like which is the most stable and stronger material one can use for building houses among these given seven options. So viewers again a question for you. What do you think which of these materials are most stable. Yeah, which are suitable for building our houses. Amish is asking stone. So Graham is saying that yeah Amish is asking stone is it stone. Yeah that is pretty much answer because otherwise the place is prone to be attacked by some worms and fungus growth and this is if it is made up of wood or bamboo or coconut leaves it's prone for fire right it's not fireproof. However when we use stone, which is waterproof, fireproof, windproof and very strong. It makes a very reliable structure as a house right. However, the problem with stone is it is not easily moldable to shape which we desire like you need a lot of laborious like labor intensive work to make it a stronger house and of houses of our design. So there comes man made material, which is very much similar to stone is concrete, which is which has all the property of stone and in addition they this is easily moldable to reliable desired shape. And also it is economical in the sense it can be transported to one place to another and it is available, it can be made available throughout the world. So and also which allows us to make many structures of beautiful shapes and size. As we see here this high rise buildings in Mumbai Lotus temple in Delhi and bridges and some dams particularly this if you see this dam like on the this is interesting because the other side looks naturally occurring stone is a mountain. But this side is made of material which is very much similar to very much similar to naturally occurring stone that is concrete right. So these kind of structures which are important for human consumption of humans usage of I mean consumption and usage these are very important. So it is possible only because of the material such as concrete right. So, yeah, we shall lie have a question for you here like so you've been using concrete for various structures building these beautiful structures like can you guess when did we start using concrete. Maybe others in the chat box also others in the audience can also predict. Yes, yes, yes in the chat box what do you think how old have we been using concrete as humans. So, okay, so what is your guess we shall use put that guess is I think means what I think around 400 500 years because we have some 100 200 year old buildings that I know. Okay, okay, maybe a little older than that. Yeah, yeah, that's pretty much close as we see it but interestingly we have been using this concrete since nearly to more than 2000 years ago. On YouTube we have a comment from Krishna. Okay, so it's more than 1950. Okay, okay, later than 1950 maybe. Oh, I don't know it's 1950 years or your 1950. Okay, okay, yeah, okay, fair enough. So to reveal the answer we're like concrete as such is known to human beings since nearly more than 2000 years. So it was Romans who first use concrete for building poles, temples and many other things for their day to day life and Romans were lucky, were lucky in the sense they didn't have to produce artificially the concrete was readily available from nature. So what they did is they use volcanic dust, which was, which was available near their place in Huzuroli. They dig the dust, and then mixed with lime, that is calcium oxide, and they added with some other aggregates like stone and sand that become concrete for their construction. So, so this particular temple, which I am showing now is of Mercury, and which is located in Baye, Italy, which constructed in the first century BC is still surviving is one of the oldest surviving dome in the world. And again, another marvelous structure they built, Romans built is Pantheon, which is still standing. And this is one of the biggest unreinforced concrete, meaning there was no other material used for building this structure apart from concrete. I will be discussing what is reinforced and unreinforced later. And once the Roman Empire fell collapsed, strangely no one used concrete for building any structures for over next thousand years. Why so? Why can't we use concrete for next, you say? Okay, okay, that's actually a mysterious thing, but there are some rational reasoning given for that. One is this was naturally occurring concrete, right? There was no industrial production as such, and that is one of the reason. And another reason they knew there is a flaw in their concrete, which they never resolved. Romans didn't resolve, so that is one of the reason which I will be talking what was the flaw and why didn't they use it extensively? Why following people never used it for next thousand years? Maybe I will be discussing that in detail a little later. You may have to wait for that answer. So going ahead, during industrial revolution in Europe, they realized the necessity for having a material which is very much similar to Roman concrete. So during that time, Joseph Astin, he is a bricklayer, so he developed or improved a method for producing artificial stone. So artificial stone, which is like he is the one who invented cement, which he labeled it as artificial stone, right? Just one doubt, you were talking about concrete just now and now you are saying cement. So concrete and cement same thing? No, actually they are different, but cement is a primary ingredient required to make concrete. So that's why it is important to know cement production when it was invented, at least the Portland cement, which we now use very often. Whenever you see outside, which in a building site, in the construction site, it is mostly they are using Portland cement. That is what Joseph Astin invented in 1824. He named it as Portland cement because it was very similar to Portland stone, which I have shown here, right? And further, just using this cement was not enough for having a stronger structure. So that flaw was addressed by a pot maker. I mean, in Paris, Joseph Mania, he introduced iron mesh into this concrete, which kind of made a stronger pot. Like he was using clay fire, fire clay pots before, then he realized it is brittle and he wants something stronger. Then even though when he started using just concrete, it was not strong enough, it was still cracking. So he introduced iron mesh, it became much more stronger and it can be used for quite a long time. So this is one of the milestone in concrete history. And recently there are many changes. There are many developments in making this concrete as a smart material or improved material in terms of materialistic properties. So I will be talking about this in detail a little later. And as you were talking about what is the difference between concrete and cement, let's look into what concrete is made of. So concrete is basically made of, it's a mixture of cement, sand, fresh stone and obviously water. To get this, okay, you cannot add a various proportion. You can get a consistency of this concrete by adding roughly 13% of cement, 20% of water and 67% of aggregates. Are there any questions here? Currently, no, we don't have any questions right now. Okay, great. So as you can see here, only 13% of cement is required but it is a key material which glues together all the other components of concrete. So as I mentioned, cement is a key ingredient. We need to know more about cement. So cement is a unique glue, which basically glues all the other aggregates and water and there are two types of cement. One is hydraulic cement, another is non-hydraulic cement. Hydraulic cement is basically something, a kind of cement which gets hardened when we add water to it. For example, Portland cement, that is a very commonly used kind of cement. There is another kind of cement, which is called non-hydraulic cement. It's something hardens without water. Like when there is no water, it becomes harder. For example, it's a slack line, which is commonly known as tuna in India and Sunna in Canada. So when there is no water in it, it will become quite hard, quite hard similar to concrete. So this is another kind of cement. But in this talk, we will mostly focus on Portland cement and its properties. So how it is made and how can it be used. So as far as raw material is concerned, you see limestone, shale, clay sand and iron ore is key raw materials for production of cement. And limestone is calcium carbonate in chemical terms. And these are shale, clay, sand basically made of silica and oxygen atoms and coming together forming either silicates or silica, SiO2 and iron ore. So just grinding them and mixing them doesn't yield you cement. For having cement, you need to grind the raw materials. What is the impact in local weather due to concretization of building? Is it sustainable? So I think we will be addressing that question. We can take that question later. Because if I understood properly, what are the effects of using concrete, right? How it is affecting nature. Is that the question? Yes, it is actually talking about local weather. Okay, okay, yeah, yeah, yeah. Temperature. Okay, okay. We will come back to that question. We will take up that question at the end. So yeah, and that is mixed. I mean, raw materials are grinded and mixed and led into a rotating heater, which is heated at very high temperature, 1450 degrees Celsius. And then it is further grinded and then we get cement, which is packed and transported where it is required. So during this process, and did you, I mean, one can notice here we use quite higher temperatures around 1450 degrees Celsius. And which is basically we are mimicking volcano as Roman state, I mean, nature was doing it for them. But we are basically now mimicking that process of heating at very high temperature and getting the cement. And while doing so we liberate. So limestone is basically upon eating the tear temperature gives calcium oxide and carbon dioxide. So we are releasing a lot of carbon dioxide, but calcium oxide here reacts again with clay material and to form. And this clay is basically silicon and oxygen based compound or material which gives a family of calcium silicates. And OK, so as we are talking about cement production, this is a fun fact. There's a town named Cement Nagar in Andhra Pradesh because there is a cement production unit. So they named their town as Cement Nagar. Okay, then going forward as we know about cement now we'll go again back to concrete production. As we mentioned, we mix these raw materials and make concrete. When we add water, it sets a quite various number of complex reactions. It initiates reactions. And while it is doing so, it grows along with water. When we add water, it reacts with water and there is a growth of this kind of mesh kind of fibrils which interlock each other and make it stronger. When we add water, it eventually becomes stronger. This is the process here. So addition of water is important to concrete. Just I had a question for you Satish. So this fiber like network of cement, is this network what giving the concreted strength on drying? Exactly, I mean they interlink when they grow, I mean when they suck up water, basically cement molecules will interact with water molecules. They form this kind of fibrils. These interlinkage will give them the strength. It becomes stronger. So there is a question for audience here. When we add water to this cement and aggregate mixture, what would happen? Like have you touched any time this concrete mixer? Did you feel hot or cold when you touch it? Like is there anyone who touched concrete by their hand? Exothermic reaction. Great. Yeah, that is actually one of my questions. So here when we add water. So exothermic basically the react mixture becomes warm. So it becomes warmer and endothermic process is basically something which becomes colder. As someone mentioned here, it is an exothermic reaction, means it will become warmer. I mean interestingly it is not just giving heat at some point, it gives away in a different sequence of temperature. Like when we just add water to concrete, so water to cement mixture. So there is initial mixing reaction which gives away a lot of heat. I mean it will become warmer in the beginning. Then it cools down. So this initial mixing when addition will take place in minutes. But for next few hours, for three hours nearly. So you can actually it doesn't give away a lot of heat. But this is a period where you can transport to a construction site and put it on wherever you require. I mean maybe as floor or roof, whichever the construction you are doing. And then after you added that into a particular structure, it again starts giving out a lot of heat. So this giving out heat takes place for quite some time. It is seen in terms of days and during this process strengthening of concrete happens. That is where concrete is becoming stone, something like that. So during this process you need to add water that is called curing. I mean you basically add water for curing which allows concrete to retain moisture. And this is important because there is a lot of heat emitted here to dissipate and also improve durability. And reduce the cracking nature of the concrete, you need to keep adding water. So that is why you see people adding water for curing purpose. And I have another question regarding this addition of water to cement mixture. So can anybody guess what would be the pH of this mixture? So viewers can comment the answers in the chat or those on Zoom can unmute and say. So Satish, what I think it should be somewhat alkaline? Yes, it is alkaline. Because of presence of alkalis, many alkalis like calcium hydroxide and all, this becomes alkaline. That is the reason like when you see a construction workers use gloves while handling this concrete. Like the reason is alkalis is very harmful for our skin. So that is why they are using gloves to protect themselves from harmful effect of concrete. So we have been talking about history and chemistry of concrete. And can anyone guess which is the most used material in the world? Or I can put it in the other way, like which is the most consumed material or substance in the world by human beings? Anyone? Like maybe like maybe water. Yeah, water is a necessity then. Better answer again. Okay. It's coffee. Yeah, that is okay. So in terms of consumption, yeah, maybe that is fun. But to make coffee, you need water, right? So that makes sense. Water is one of the most consumed material. Like can you guess what is the next two water? Like which material or substance is being used? So viewers, can you guess what is the second most used substance after water? I mean, actually it is straightforward because as we are talking about concrete, I mean, I am expecting it's concrete, right? So, okay, let's go forward. And concrete is the second most used substance in the world only after water. So we use a lot of enormous amount of concrete, which is basically in terms of numbers is 3.5 billion tons of Portland cement is being produced annually in the world. And obviously concrete is around 10 billion times a billion tons. And because there is a reaction happening while producing cement that is carbon dioxide production while we eat calcium carbonate. It emits for every 100, every ton of cement production emits nearly 622 kilogram of carbon dioxide, which is huge. And actually we are trying to answer the question which was previously posed. Yeah, right. I mean, this is one of the effect like in terms of production itself, there is nearly 8% of manmade emissions of carbon dioxide comes from cement industry, which is huge. And to put it in other terms, like, we know these structures, at least the right one structure, we know it's a Bhuj Khalifa tallest building in the world, which is made up of concrete consumed nearly 0.33 million meter cube of concrete meter cube is basically 1000 liters, which is huge. And again, there's a dam, three gorgeous dam in China, which is one of the largest dam. Can anybody make a guess what is the amount of concrete is being used to construct this dam? Like maybe how many times more or less than Bhuj Khalifa consumed? Any guesses? So viewers, what do you think? How many times of concrete is being used? Amish says twice. Any more guesses? Okay, okay. I guess maybe 10 times. But this is much more than that. In the sense, it is nearly 90 times because it consumed 28 million meter cube of concrete, which is enormous amount of concrete. So as we are talking about a dam in China, and another fact about China's consumption of concrete is they in between 2011 and 13, I mean, that is three years of time, China used a lot more concrete than USA used in the whole entire 21st century, 20th century, 20th century, which is, which you can see that they have used quite a lot of concrete, right? They must have, I mean, so they have also resulted in a lot of carbon dioxide emission, which is a greenhouse gas and which leads to global warming, which is, and also we cannot complain much about it because that is a necessity material. In concrete, you cannot live without concrete because we need to cater nearly 8 billion people in the world and we need water, we need energy for our consumption and we need shelter more than everything. So it is indeed a costly compromise, right? So scientists are working towards how can they fix this? One of the aspects they go about is looking for cement alternatives. How can they replace cement? Sadly, they cannot completely replace cement. What they can do is they can partly replace, meaning they can mix certain portion of other materials like fly ash, black furnace, slag or micro silica, which are byproducts. Fly ash is basically a byproduct of composition of coal, black furnace, slag is a byproduct during production of iron and micro silica while production of silicon products, right? So in place of Portland cement, 25% of Portland cement can be replaced with fly ash, which gives a reliable and decent strength to the concrete coming out of this particular cement. And black furnace when you see, this is basically a production unit of iron where the raw materials, as you see limestone is one of the lab material and which has been heated very similar to our cement production. And the waste material produced here is slag, which is again, if you look into the chemistry, it's a calcium aluminum silica, which is very similar to chemistry of actual cement we use, the Portland cement. So it allows us to replace 70 to 80%, which is already commercially available. Portland slag cement is available in India as well and it is known to be more stronger than ordinary Portland cement. So these are one of the aspects. And going forward, as you were asking, Vishal, why there was gap of 1000 years, right? So Romans were not able to solve this because when they have concrete slab like this, when the force is applied, they tend to crack, they can break down into pieces, they didn't know how to solve this. And after industrial revolution and a pot maker who solved this using steel bar, then this is called reinforced concrete, meaning even after when we put force, there is no deformation and there's no breakage. I mean, there's no breakage in the sense of the strong strength of the material itself is becoming stronger, right? So this is something called RCC. This is a well-known term RCC that is reinforced cement concrete. Basically, the concrete is reinforced with steel. It is put inside a concrete material. So if you look into other property, concrete has higher compressive strength. Compressive strength when you apply force on the both sides, it can withstand IE force, a load. However, when we stretch it, it will crack open. But a steel, when we reinforce the steel, which has higher tensile strength, this hybrid material will be more stronger than just concrete. So that is why we say concrete and steel make a best partnership. However, when the steel is exposed, it will get corroded. That is one of the factors we need to be careful about. And as we are talking about best partnership, there is another good thing about reinforced concrete. Meaning, because of fulcaling nature of concrete, there will be a protecting layer formed on the surface of steel bar, right? So this gives, this will protect from metal from corroding, right? And if it is reduced, pH reduces with various reasons, it corrods and weakens the structures. And this is one of the things we need to be careful about. But these, as a whole, RCC is a very strong material which we can relay for construction of many structures, just like bridges, buildings and so on and so forth. So, yeah, Satish, when you are calling this the best partnership, when filling this reinforced concrete, we see cracks on buildings and sometimes like on bridges also like old roads, we see cracks. Okay, okay, I get it. Why there are cracks even with this stability and strongness, right? Stronger nature. So, okay, there are two possible reasons. Like one is they might have not cured it well, they might not have added water after we constructed, soon after they are used concrete for building. And another thing is, you might have aware of the fact that during summer, our doors make noises because they get expanded, right? Because of heat, they, and during winter, they may go back to original shape and they don't do any sound. So, this is because of repeated expansion and contraction. Like because of this effect, we tend to see cracks. And this is very similar to our bathing, like this is what happens, this is how it looks. Like in a sense, during summer, it expands and during winter, it contracts. This continuous repetition leads to cracks, both on walls and you can see also see on it roads as well, right? And again, scientists are working towards how to fix this. And so, usually, scientists gets inspiration and solution from our day to day life and nature around us. One of the aspect is when we get a small cut in our hand, our body knows how to self-heal. Like in the sense, it knows how to cure by itself without we being applying any appointment or something like that, right? This is called self-healing and scientists wonder what if we can make the same thing if concrete have a crack and it self-heals. So, such material being is under research and it is there since 40 years and that kind of material is called self-healing concrete. So, this is important when we are constructing concretes such as nuclear power station or bridges where it is preferred not to have a frequent visits there to check the stability of the construction. So, this kind of self-healing concrete comes into help, right? And it also reduces cost of repairing many many factors. That is one of the interesting thing and important thing to be considered. How do they do it? Like, okay, so this is an interesting thing, but how do they do it, right? That's the general question one can ask. So, interestingly, the question answer came from an unexpected place. In the sense, a microbiologist who were working on some kind of bacteria and they were actually looking at living organisms in extreme pH conditions, like whether some organisms able to survive in extreme alkaline conditions and they realize there is a kind of bacteria which is called bacillus pasturi is stable and at these alkaline conditions they can survive at these conditions and it excrete calcite which is basically calcium carbonate. Again, it's very similar to limestone property which is stronger material, right? And it can remain dormant for years together. So, what they did is basically they mixed starch like metal which is a food for this bacteria and mix this bacteria and starch with concrete. They casted, okay? When there is crack appearing, the bacteria will get exposed and then when water comes in or water vapor comes in, they multiply. They wake up and multiply and then excrete calcite which is basically healing products they will excrete, which helps to regain the structure. It will fill the gap, fills the crack and it helps to regain the structure. And to understand like, okay, this is basically a civil engineer's problem where chemist comes involved and microbiologist who was working on some bacteria realizes the potential of using this kind of bacteria in cracking and biotechnologists who can help make this bacteria produce a lot of, I mean, higher amount of healing products, making this solution, making, I mean, resulting in a solution for this problem, cracking problem, right? So, it's a material science approach where everybody comes together and solves a problem existing in front of us. And basically, scientists are trying to make concrete smarter. So, it is self-filling concrete. And in another approach, another attempt to make this further smarter, this clean structure, which is actually a church in Rome, Italy, again, which is clean. So, and apparently nobody cleans it as often as many other structures because it is a self-cleaning concrete. It cleans by itself. So, basically, when some bio or organic material falls on it, this concrete is embedded with titanium dioxide. Okay, so this is basically a photo catalyst, meaning when sunlight falls on this titanium dioxide, it generates some substances called free radicals, which destroys organic molecules or microorganisms. It prevents the microbial growth. So, it retains its whiteness. And this, after it destroys organic waste, that smaller molecules can be washed away either with rain or stronger wind. So, it remains clean. Yeah, that is... Shouldn't we give this all this self-cleaning credit to the white paint instead of the... You are calling it self-cleaning concrete, but shouldn't it be the white paint which is having this titanium dioxide? Okay, that's a good question. Actually, paint can do this well. If you add titanium dioxide into paint and apply it on walls. But in this particular case, it is not paint. It is just concrete. But it's a white concrete made up of white cement. So, yeah, this is a different scenario. Like, you save money, maybe not painting this one. So, basically, concrete is working as both an aesthetic approach and also a protective layer. So, the process for this white cement is the same as the Portland cement you were talking about? Yeah, pretty much similar Portland cement. The only thing is, as I mentioned earlier, iron, if we remove iron ore in production of cement, it becomes whitish. The cement looks whitish, unlike we see a grayish color. The grayish color comes mostly because of iron ore used as a raw material in the production of concrete. Okay, so, yeah, I learned most about this fundamental nature of... There are interesting stories about this particular material, concrete, through this book called Stuff Matters, written by one of the leading material scientists, Mark Miorini, which is a really good book. I would suggest everybody to read this particular book because it doesn't involve a lot of technical words. It has been described in very simple and it's worth reading. Okay, and with that note, I thank you. Okay, so thank you, Satish. You have given us quite multi-dimensional insights about concrete that we never looked into. So, yeah, we can have our questions from our participants and our viewers on YouTube also. Yeah, maybe they can put down the questions in the chat box. We can wait for some 30 seconds. Amish says, great session. Thank you. Thank you, Amish, for being there. Thanks, Amish. Miorini had some questions. I think the first question was answered. What is impact in local weather? Okay, actually, it impacts in... Okay, so I think he meant... So, there is a tendency of concrete to absorb carbon dioxide. It basically... There is something called carbon sequesterization. So, it absorbs carbon dioxide and it kind of increases the temperature around us because carbon dioxide being greenhouse gas and it leads to global warming. So, when we have a lot of concrete structures altogether, it basically warms up. I mean, you can feel that when you go out of Mumbai or any city you live, you feel that your surrounding has become colder than when you are inside a city. I think that is that explains... That's the effect of concrete jungles. Okay. So, yeah, Miorini says, this is my session. Interesting story about concrete. Thanks, Satish. Thank you. Yeah, thanks. So, yeah, we don't see any more questions, but yeah, you can put down your questions later on in the chat. Okay, so Miorini has one more question. Yeah, sure. Is there an alternative for concrete? Okay, that's an interesting question. Alternative for concrete? Okay, I mean, stone can be used, but obviously there is limitation of availability of stone, right? In terms of exact concrete replacement, okay, one can build using steel as such. I mean, just with steel. Problem with the steel is that it's expensive compared to concrete, reinforced concrete. Just steel doesn't make you... I mean, steel is reliable material, which you can build also soft, but it's costly. And also, there is no glasses, maybe tinted glasses. There are many other glasses which are equally strong. Problem is, they are expensive again. So, economically, they are not feasible. I think concrete is the most economical way of constructing most of the structures we use. Again, it is not limited just for concrete. Steel can be used, glass can be used. Yeah, wood can be used. The only thing is you need to take care of attacking by termites or other worms. In fact, most of the buildings in US are built using wood. So, yeah. So, what I would like to answer to this, there is not exactly an alternative for concrete that could replace it completely. But like Satish spoke about some alternatives of cement. Right, right. It can reduce its usage for quite... Yeah, consumption can be reduced. Right, right, right, right, you're right. It's the same strength and properties still, right? Exactly, yeah. So, yeah, so I think we don't have any more questions. So on Zoom, do we have any more questions? I think you should be able to say it. No, like... Okay, so... Okay, so I think we come to the end of this session. Yeah, so thanks, Satish. And thank you our viewers. So we shall meet again next month on the second Sunday at 11 a.m. with another interesting topic on this steamboat top series. And you can follow us on our social media handles. Subscribe to the channel on YouTube to get the notifications and updates on our new talks. And you can watch our older sessions, which have covered quite many interesting talks. So, yeah. Thank you all. And wish you all a very happy new year in advance from steamboat team. See you all next year. Yeah, okay. Okay, see you.