As an old chemistry graduate from the University of Nottingham its good to hear Martin Barker mentioned - his lectures were some of the most memorable, engaging and fun.... I was gutted when I heard he had passed away RIP Dr Barker
Very nice video but I was hoping to hear more about the reaction itself. I know that the reaction is fairly exothermic. I was hoping to hear more about how that varied or could be controlled through composition and how it affected larger pours. Perhaps a follow up video could be done that talked about expansion/contraction of concrete and it's exothermic reaction. Love these videos. I have forwarded them on to many others who have asked me questions from time to time about the various aspects of materials engineering they have covered. Hats off to you guys. Nicely done.
Just discovered this great, informative series... my thanks to the professor and his awesome finger-in-the-outlet hairdo... not sure why he feels the need to accompany every single syllable with a hand gesture, but it's all good! Love these vids and their straightforward no-nonsense explanations! for us non-scientists who are fascinated by science.
Great professor, great lectures, but in this case he had a slip. once water is added to the cement-aggregate mixture (ie, concrete) it starts the chemical reaction of hydration. After that you only have 2 Hrs to pour it (however there are certain chemicals that can be added in order to extend the setting time for an extra hour or two. Really like your videos and your honesty,
few things, limestone is mixed with clay and not sand to make cement, Sand is used as an aggregate in concrete and is inert, doesn't react, and the Roman structures were made from lime which reacts with CO2 to form hard calcium carbonate and so it becomes stronger over time. Concrete, on the other hand, deteriorates due to carbonation over years....
Once hardened and properly sealed, there is no need to worry. If your counter top is polished well enough and you disinfect it you can potentially eat off it without worries. A teacher of mine has a polished concrete counter top that has been treated whit acid in some parts, it looks pretty nice with a vegetation motif and it doesn't have pores which makes it very clean and not bacteria friendly.
I remember, long ago, an article in SciAm about concrete setting, and I find the explanation here very deficient. Rather than a gel hardening, the particles of toasted dry lime are surrounded by water. As the water invades the dry interior of the particle and begins slaking the lime, it increases the volume of the interior, and pretty soon the generated pressure drives filaments of the CaOH through to the outside. Eventually the CaOH combines with CO2 to become hard calcium carbonate. These filaments from millions of small particles interlock with their neighbors, making a strong structure. The sand provides nothing but bulk and tiny cracks in the sand articles to allow the grip of the calcium carbonate.
@alpatranss "The professor makes it sound like if you mix CaO and SiO2 with water you get concrete" -- if you add the also mentioned aggregate to it I rather think you do. A good teacher is able to convey the essential core of a subject without getting the story cluttered up with pedantic detail. I think the professor knows this and he does a good job of presenting technical information in a clear and lucid manner.
Other concrete trivia - the bubbles aren't always a bad thing. There are several applications for foamed concrete - including at the end of runways, where some airports are laying an area of special foamed concrete that crushes under the weight of an aircraft, rapidly slowing it and preventing disastrous overruns. . Also, on large projects, the temperature of the reaction can be an issue - Hoover dam, for example, required over 500 miles of cooling tubing to avoid excess heat during curing.
Its also advisable to keep concrete wet for a few days if its to hot, workmen then spray water ontop periodicly. So it has more time to set, like the proffesor explained the longer it takes for concrete to set the harder it will get, but the opposite is also treu, if concrete sets to fast it wil become unstable and susceptable to pressure, resulting in flaking top layer and cracks, it becomes a layer op lose "pieces" of concrete being hold together by friction and rebar.
Your right that it will set even if it is kept moving. But you can still pour after 2 hours unless it really hot ouside. I work as a concrete field testing technician and when i turn trucks aound for the 2 hours ''norm'' they sometimes drive over an hour and a half back to the plant to make concrete blocks without any trouble. And he's also wrong about the air bubbles to an extent. If you live in a cold country 5-8% of air in the concrete prevents cracks due to freezing water.
Totally agree, also modern cement does not react at all with carbon dioxide (it reacts with water ence the name "hydraulic cement" ) and that's why it can set underwater too!
@LasagnaIsGood The answer to this is summed up in the beginning "You take calcium carbonate and you heat it up to create calcium oxide or lyme". It takes a lot of energy to heat up the limestone to the point where it becomes lyme. Energy prices are on the rise so concrete prices fluctuate with energy prices. Then there is the cost of moving a heavy substance to the place where it is to be mixed and then from there where it will be poured. Try shipping 100lbs of rock interstate.
The fact that the hardening is postponed as long as the concrete is stirred is very interesting and deserves an explanation. Are there more examples of chemical reactions that only take place when not mechanically disturbed?
and you forgot to add that the steel re inforcements are added to add tensile strength. they are sometimes used to increase compressive strength by compressing, but mostly to increase tensile strength.
Im currently making a project at my chemical engineering faculty. IM writing about a technology called calcium looping.. Where we from the cement plant can completely eliminate the CO2 emission by one simple way: The limestone gets into the calcinator, making CaO, most of it goes to making cement/concrete as usual.
When concrete was explained to me by a concrete contractor he used the terms "chemical water" and "mechanical water". I was hoping to hear about those concepts from the professor.
@wazscience Bulking out the mixture. It adds strength as the aggregate is stonger than the sand cement mixture alone. Think of a concrete wall as being a wall made out of very small bricks, the aggregate is the brick and the sand /cement is the mortar between the bricks
The steel doesn't just increase strength, it is specifically added in areas where tension forces will be present. Like he said, concrete doesn't work well in tension. But steel does.
You should investigate the concrete process used to create the Hoover dam in the US. They have some interesting figures as to how long it would take the concrete to cure if they poured it all at once. I believe it was 180yrs+. There was a special process used to cure it because of the quantity that was being used. Also, when concrete cures, reacting with CO2, it is also interesting the amount of C02 that the concrete actually absorbs throughout its lifetime--I THINK it 80% absorption.
@Zaddtheman Most of what the professor means when he talks about green chemistry doesn't even have to do with global warming. It's finding new ways to do reactions using less volatile chemicals or in this case eliminating unnecessary waste.
Steel is what gives concrete structures the tensile strength they need to stay up. Arches back in old times were made with a compression only design using stone so no steel was needed.
How did you get any work done with the building going on right outside your window? I had to cover the window in my office when I was an undergraduate because there was a giant tower crane across the street and all I could do was watch it... Proof I got older in college but never grew up.
@DeoMachina The reaction the professor talked about is exothermic, releasing heat. Plaster of Paris is the same way... I remember reading a story of a person who submerged their forearm in still-liquid plaster of paris and ended up suffering severe burns as a result.
We might not run out of concrete but the energy required to make it combined with the energy supply challenge we have in the near future means that that will be an issue as well.
I've got a question for you professor, how did the ancient Romans know to drive out the CO2? Or rather how did they know how to make it in the first place?
@alpatranss I also agree with alpatranss. Cement manufacturing is a solid state reaction between CaO, SiO2, Al2O3 and Fe2O3 at very high temperature. Alpatranss, did you work in the industry? I worked for Lone Star Ind. in Houston in the early '80s until they went out of business. I miss looking into the 500 foot long rotation kilns.
I think a great followup video would delve into the actual chemical reactions taking place in hydrated Portland cement. It would also be neat to see grains of cement, under a microscope as they change form (time lapse) after being wet. This would help people understand how Portland cement binds stuff together.
i used to make powder coating, the overground powder (only micron sized particles) could be added as well because of the high amounts of SiO2, but it was very toxic to handle, you could smell it through the best gas masks, it was like moon dust, never really settled
As an Architecture major I find your way of thinking ridiculously obtuse, The professor is really spot on for a person outside the industry but what dbraven said is in fact correct and I don't think he said it to show off but to add some more precision to the content. I'm sure that the professor, as a man of science, would appreciate any correction as long as it serves for the purpose of clarity and feelings of superiority because of age are way below the intellectual level of a scientist.
Civil engineering student here as well and I'm sure you're right, but I don't think these videos are meant to go into detail. I'm sure there are alot more additives that can be used under specific circumstances, that doesn't mean he should start summing them up, all of them. But ofcourse everyone wants to show the internets that they are smarter than the youtube professor
by reusing or breaking up old stones or concrete wich hold agragate, but not all bricks can be reused such as clay bricks because their fragments are verry compressable especialy when wet! or for isnstance marble or bleu stone wich is used for making kitchen tops or doorsteps etc... they are made from large rocks then they cut out a square, the ridgid edges of the rock are then crushed into smaler pieces acoording to what size they need for the concrete recepi, not every concrete is the same.
OK that's all very fine and dandy. But I dont understand the necessity of you pointing that out in such a matter of fact way.Never did he once contradict your above statements. He just gave the general public an overall idea about what cement and concrete are and their main differences. This videos aren't meant to give an exhaustive picture ; they're just little nuggets of wisdom :)
@riveness dont worry about concrete, its not that difficult, doesnt take that much energy. compare it to aluminium, or steel, or plastic, many ores take incredible amounts of energy until you have the final product, some (like aluminium) involve electrolysis. and plastic still contains all the energy of the oil, and is completely dependent on crude oil. maybe you could get the energy for all concrete on the planet by burning all old plastic on the planet.
Concrete is not only deploiable in wet areas but its also being used to poor directly in to water of a river to form a stable foundation to but bridge pillars on them so they wint sink.. These are verry special compounds and expensive, also normal concrete is never poured under the temperature of 0° celcius because then the water would fomr crystals and the chemical reaction would stop,Execpt in Russia and the likes they will add aditives that protect it from freezing.
@mathiaspaul1987 It may absorb the same amount, not fully sure, but the amount of time to absorb co2 vs how quickly it's released is not in the globes favor. There are some cements are that absorb co2 to set like Eco-cement, ie it requires co2 to set.
@vlvl21 yes it can demolish buildings which have concrete in their construction are recycled all the time the debris is ground up to the proper size and can be used as aggrogate for concrete in new buildings in fact the next hirise or basically any building you walk into there is almost certanly recycled concrete holding up the building or in the foundation or both
@AlterGX & @ Chaosblade777 you are both right. I ignored for a moment that you need to heat the CaCO3 and that the amount of Energy needed for this is most of the time gainded by burning fossil energies. But what if I would say that I use wind, solar, water or atomic energy for it ^^
They need to make building out of a new stone type. You know play around with stone chemistry. Not because it would be better than concrete, just because we can. If all else fails, you could reinforce the building with steel.
I don´t think that the CO2 that does come from the concrete industry will cause such a problem, because when the concrete or the cement is used it will bind the same amount of CO2 back over time. Or am I wrong?
@LasagnaIsGood Let us say we found a way of utilizing the surface dust of the moon for building houses. You could still say "We will never run out", but it is still an expenssive process of getting the moon dust. So I don't see how the "we will never run out" is linked to the pricing in this case. Well, it sorta is. If on the same time it was a rare product, concrete, it would be even more expenssive :)
In Japan, they would typically use a peristaltic concrete pump to get the concrete up there. But then, over here, greenness (sorry, "ECO") is a marketing fad to get you to replace your perfectly good telly/fridge/microwave/house/car/wife/children/pets with new, more ECO friendly ones!
Then it still contains what he said. Yes it is a little removed, much like a child is removed from the parent. The Cement is the parent, the aggregate is the second parent, and the concrete is the child.
@jakeweiq I don't know if they'd burn alive... they'd probably die of asphyxiation before the heat caused them significant harm, but I'm sure the heat certainly wouldn't help preserve the body. I don't think concrete produces quite as much heat per volume as plaster does.
If concrete is made from limestone, what is the difference between it and limecrete? I keep hearing stuff about limecrete, people saying that it is more eco friendly than concrete and even sequesters more co2 over its life than is used in its manufacture, wear as concrete is really bad co2 wise. But if they are made from the same stuff how can they be so different?
@Digeridude Not really, the aggregate is basically just a more sturdy substance which the concrete can hold together. This makes the concrete structure overall more durable.
@mathiaspaul1987 I don't imagine concrete binds nearly the same amounts of CO2 as are released into the atmosphere by industry, which are probably, unfortunately, much greater due to the large-scale chemical reactions done there compared to the gradual one done by concrete.
Whilst the videos are not an exhaustive picture they should at least be factual. When he says that concrete is a mix of calcium oxide (lime), sand (silicates) and aggregate it is incorrect. Cement is not the same as calcium oxide (lime). Most modern cement is Portland Cement and contains the components as per dbraven's post.
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As an old chemistry graduate from the University of Nottingham its good to hear Martin Barker mentioned - his lectures were some of the most memorable, engaging and fun.... I was gutted when I heard he had passed away RIP Dr Barker
I study architecture and despite a very broad and deep going lectures on concrete i have learned some things i didn't knew from this video!
Thank you!
Very nice video but I was hoping to hear more about the reaction itself. I know that the reaction is fairly exothermic. I was hoping to hear more about how that varied or could be controlled through composition and how it affected larger pours.
Perhaps a follow up video could be done that talked about expansion/contraction of concrete and it's exothermic reaction.
Love these videos. I have forwarded them on to many others who have asked me questions from time to time about the various aspects of materials engineering they have covered.
Hats off to you guys. Nicely done.
Just discovered this great, informative series... my thanks to the professor and his awesome finger-in-the-outlet hairdo... not sure why he feels the need to accompany every single syllable with a hand gesture, but it's all good! Love these vids and their straightforward no-nonsense explanations! for us non-scientists who are fascinated by science.
Great professor, great lectures, but in this case he had a slip. once water is added to the cement-aggregate mixture (ie, concrete) it starts the chemical reaction of hydration. After that you only have 2 Hrs to pour it (however there are certain chemicals that can be added in order to extend the setting time for an extra hour or two. Really like your videos and your honesty,
few things, limestone is mixed with clay and not sand to make cement, Sand is used as an aggregate in concrete and is inert, doesn't react, and the Roman structures were made from lime which reacts with CO2 to form hard calcium carbonate and so it becomes stronger over time. Concrete, on the other hand, deteriorates due to carbonation over years....
Once hardened and properly sealed, there is no need to worry. If your counter top is polished well enough and you disinfect it you can potentially eat off it without worries. A teacher of mine has a polished concrete counter top that has been treated whit acid in some parts, it looks pretty nice with a vegetation motif and it doesn't have pores which makes it very clean and not bacteria friendly.
I remember, long ago, an article in SciAm about concrete setting, and I find the explanation here very deficient. Rather than a gel hardening, the particles of toasted dry lime are surrounded by water. As the water invades the dry interior of the particle and begins slaking the lime, it increases the volume of the interior, and pretty soon the generated pressure drives filaments of the CaOH through to the outside. Eventually the CaOH combines with CO2 to become hard calcium carbonate. These filaments from millions of small particles interlock with their neighbors, making a strong structure. The sand provides nothing but bulk and tiny cracks in the sand articles to allow the grip of the calcium carbonate.
here's an idea, don't worry about it. he's an old gent. we all should be so steady when we reach his age.
Could we grind up old concrete and heat it up? Also, it absorbs CO2 over time. So in essence it eventually recaptures what is put into the atmosphere.
@alpatranss "The professor makes it sound like if you mix CaO and SiO2 with water you get concrete" -- if you add the also mentioned aggregate to it I rather think you do. A good teacher is able to convey the essential core of a subject without getting the story cluttered up with pedantic detail. I think the professor knows this and he does a good job of presenting technical information in a clear and lucid manner.
Other concrete trivia - the bubbles aren't always a bad thing. There are several applications for foamed concrete - including at the end of runways, where some airports are laying an area of special foamed concrete that crushes under the weight of an aircraft, rapidly slowing it and preventing disastrous overruns.
.
Also, on large projects, the temperature of the reaction can be an issue - Hoover dam, for example, required over 500 miles of cooling tubing to avoid excess heat during curing.
poor guy, he looks absolutely frozen. thanks for doing this prof! :)
Its also advisable to keep concrete wet for a few days if its to hot, workmen then spray water ontop periodicly. So it has more time to set, like the proffesor explained the longer it takes for concrete to set the harder it will get, but the opposite is also treu, if concrete sets to fast it wil become unstable and susceptable to pressure, resulting in flaking top layer and cracks, it becomes a layer op lose "pieces" of concrete being hold together by friction and rebar.
Your right that it will set even if it is kept moving.
But you can still pour after 2 hours unless it really hot ouside. I work as a concrete field testing technician and when i turn trucks aound for the 2 hours ''norm'' they sometimes drive over an hour and a half back to the plant to make concrete blocks without any trouble.
And he's also wrong about the air bubbles to an extent. If you live in a cold country 5-8% of air in the concrete prevents cracks due to freezing water.
Totally agree, also modern cement does not react at all with carbon dioxide (it reacts with water ence the name "hydraulic cement" ) and that's why it can set underwater too!
I like how he can make the ideas of watching concrete dry exciting.
another great video, I try to get my high school students to watch these, just fantastic
I really admire the Professor for his honest approach to life and science.
is it just me or when the professor was explaining what the cement truck was doing he looked like an exited little school boy it was so awesome.
@LasagnaIsGood The answer to this is summed up in the beginning "You take calcium carbonate and you heat it up to create calcium oxide or lyme". It takes a lot of energy to heat up the limestone to the point where it becomes lyme. Energy prices are on the rise so concrete prices fluctuate with energy prices. Then there is the cost of moving a heavy substance to the place where it is to be mixed and then from there where it will be poured. Try shipping 100lbs of rock interstate.
The fact that the hardening is postponed as long as the concrete is stirred is very interesting and deserves an explanation. Are there more examples of chemical reactions that only take place when not mechanically disturbed?
and you forgot to add that the steel re inforcements are added to add tensile strength. they are sometimes used to increase compressive strength by compressing, but mostly to increase tensile strength.
Im currently making a project at my chemical engineering faculty. IM writing about a technology called calcium looping.. Where we from the cement plant can completely eliminate the CO2 emission by one simple way:
The limestone gets into the calcinator, making CaO, most of it goes to making cement/concrete as usual.
When concrete was explained to me by a concrete contractor he used the terms "chemical water" and "mechanical water". I was hoping to hear about those concepts from the professor.
@wazscience Bulking out the mixture. It adds strength as the aggregate is stonger than the sand cement mixture alone. Think of a concrete wall as being a wall made out of very small bricks, the aggregate is the brick and the sand /cement is the mortar between the bricks
The steel doesn't just increase strength, it is specifically added in areas where tension forces will be present. Like he said, concrete doesn't work well in tension. But steel does.
You should do a Periodic Video about Portland Cement. Especially since it was discovered in Portland England.
You should investigate the concrete process used to create the Hoover dam in the US. They have some interesting figures as to how long it would take the concrete to cure if they poured it all at once. I believe it was 180yrs+. There was a special process used to cure it because of the quantity that was being used.
Also, when concrete cures, reacting with CO2, it is also interesting the amount of C02 that the concrete actually absorbs throughout its lifetime--I THINK it 80% absorption.
@Arkalius80 - That was probably a chemical burn, not a heat burn. Liquid cement has a ph of about 13.
@Zaddtheman Most of what the professor means when he talks about green chemistry doesn't even have to do with global warming. It's finding new ways to do reactions using less volatile chemicals or in this case eliminating unnecessary waste.
Steel is what gives concrete structures the tensile strength they need to stay up. Arches back in old times were made with a compression only design using stone so no steel was needed.
How did you get any work done with the building going on right outside your window? I had to cover the window in my office when I was an undergraduate because there was a giant tower crane across the street and all I could do was watch it...
Proof I got older in college but never grew up.
My point is, a civil engineering STUDENT is probably wrong in comparison to a guy who's devoted his entire life to science.
Not once it's dry, but it will burn your skin while it's setting.
@DeoMachina The reaction the professor talked about is exothermic, releasing heat. Plaster of Paris is the same way... I remember reading a story of a person who submerged their forearm in still-liquid plaster of paris and ended up suffering severe burns as a result.
We might not run out of concrete but the energy required to make it combined with the energy supply challenge we have in the near future means that that will be an issue as well.
Cement is part of concrete. Concrete is typically made of lime, aggregate (sand and gravel), and portland cement.
I've got a question for you professor, how did the ancient Romans know to drive out the CO2? Or rather how did they know how to make it in the first place?
@alpatranss I also agree with alpatranss. Cement manufacturing is a solid state reaction between CaO, SiO2, Al2O3 and Fe2O3 at very high temperature. Alpatranss, did you work in the industry? I worked for Lone Star Ind. in Houston in the early '80s until they went out of business. I miss looking into the 500 foot long rotation kilns.
ive studied lots about concrete at university, good too see a video about it by you guys!
I think a great followup video would delve into the actual chemical reactions taking place in hydrated Portland cement. It would also be neat to see grains of cement, under a microscope as they change form (time lapse) after being wet. This would help people understand how Portland cement binds stuff together.
Great video as always :D
I'm being picky here, but "sand" only refers to grain size. However, sand is mostly found as SiO2
i used to make powder coating, the overground powder (only micron sized particles) could be added as well because of the high amounts of SiO2, but it was very toxic to handle, you could smell it through the best gas masks, it was like moon dust, never really settled
As an Architecture major I find your way of thinking ridiculously obtuse, The professor is really spot on for a person outside the industry but what dbraven said is in fact correct and I don't think he said it to show off but to add some more precision to the content. I'm sure that the professor, as a man of science, would appreciate any correction as long as it serves for the purpose of clarity and feelings of superiority because of age are way below the intellectual level of a scientist.
Could Periodicvideos do a video on ceramic materials not only industrious but common too like pottery from pottery throwing and making?
Civil engineering student here as well and I'm sure you're right, but I don't think these videos are meant to go into detail. I'm sure there are alot more additives that can be used under specific circumstances, that doesn't mean he should start summing them up, all of them.
But ofcourse everyone wants to show the internets that they are smarter than the youtube professor
by reusing or breaking up old stones or concrete wich hold agragate, but not all bricks can be reused such as clay bricks because their fragments are verry compressable especialy when wet! or for isnstance marble or bleu stone wich is used for making kitchen tops or doorsteps etc... they are made from large rocks then they cut out a square, the ridgid edges of the rock are then crushed into smaler pieces acoording to what size they need for the concrete recepi, not every concrete is the same.
It is always a pleasure to have one of your videos pop up in my subscription box! I love it!
The Professor makes even the concrete fascinating.
OK that's all very fine and dandy. But I dont understand the necessity of you pointing that out in such a matter of fact way.Never did he once contradict your above statements. He just gave the general public an overall idea about what cement and concrete are and their main differences. This videos aren't meant to give an exhaustive picture ; they're just little nuggets of wisdom :)
@riveness
dont worry about concrete, its not that difficult, doesnt take that much energy. compare it to aluminium, or steel, or plastic, many ores take incredible amounts of energy until you have the final product, some (like aluminium) involve electrolysis. and plastic still contains all the energy of the oil, and is completely dependent on crude oil. maybe you could get the energy for all concrete on the planet by burning all old plastic on the planet.
Cement hardening was the first chemical reaction they explained to us on chemistry lessons.
Concrete is not only deploiable in wet areas but its also being used to poor directly in to water of a river to form a stable foundation to but bridge pillars on them so they wint sink.. These are verry special compounds and expensive, also normal concrete is never poured under the temperature of 0° celcius because then the water would fomr crystals and the chemical reaction would stop,Execpt in Russia and the likes they will add aditives that protect it from freezing.
You guys should talk about the chemical structure of diamonds and explain what makes them the hardest known material on Earth.
you shoudl do somehting on welding electrodes liek 7018's or 6013's all the changes and end results are pretty cool
@mathiaspaul1987 It may absorb the same amount, not fully sure, but the amount of time to absorb co2 vs how quickly it's released is not in the globes favor.
There are some cements are that absorb co2 to set like Eco-cement, ie it requires co2 to set.
@vlvl21 yes it can demolish buildings which have concrete in their construction are recycled all the time the debris is ground up to the proper size and can be used as aggrogate for concrete in new buildings in fact the next hirise or basically any building you walk into there is almost certanly recycled concrete holding up the building or in the foundation or both
This guy is really a great lecturer.
I think I've played way to many video games when the first thing I thought of at 2:45 was Assassin's Creed 2
Hemp concrete though.
Is there any way to download this video to show to a class of people? It is an excellent teaching tool!!
If the university were involved with marketable enterprise I'd love to see them work on making concrete beautiful.
You do want entrapped air, just not big bubbles. The entrapped air helps the concrete to cure.
...in a hard hat, special gloves, periodic tie... Priceless.
Would I be considered cheating if i wore a periodic tie during my exam??
@AlterGX & @ Chaosblade777 you are both right. I ignored for a moment that you need to heat the CaCO3 and that the amount of Energy needed for this is most of the time gainded by burning fossil energies. But what if I would say that I use wind, solar, water or atomic energy for it ^^
They need to make building out of a new stone type. You know play around with stone chemistry. Not because it would be better than concrete, just because we can. If all else fails, you could reinforce the building with steel.
I don´t think that the CO2 that does come from the concrete industry will cause such a problem, because when the concrete or the cement is used it will bind the same amount of CO2 back over time.
Or am I wrong?
@LasagnaIsGood Let us say we found a way of utilizing the surface dust of the moon for building houses. You could still say "We will never run out", but it is still an expenssive process of getting the moon dust. So I don't see how the "we will never run out" is linked to the pricing in this case. Well, it sorta is. If on the same time it was a rare product, concrete, it would be even more expenssive :)
In Japan, they would typically use a peristaltic concrete pump to get the concrete up there. But then, over here, greenness (sorry, "ECO") is a marketing fad to get you to replace your perfectly good telly/fridge/microwave/house/car/wife/children/pets with new, more ECO friendly ones!
Then it still contains what he said. Yes it is a little removed, much like a child is removed from the parent. The Cement is the parent, the aggregate is the second parent, and the concrete is the child.
NEVER forget the periodic tie!!
@jakeweiq I don't know if they'd burn alive... they'd probably die of asphyxiation before the heat caused them significant harm, but I'm sure the heat certainly wouldn't help preserve the body. I don't think concrete produces quite as much heat per volume as plaster does.
In every chemistry exam you should have a periodic table!!! In some they print it behind the sheet of the test!
If concrete is made from limestone, what is the difference between it and limecrete? I keep hearing stuff about limecrete, people saying that it is more eco friendly than concrete and even sequesters more co2 over its life than is used in its manufacture, wear as concrete is really bad co2 wise. But if they are made from the same stuff how can they be so different?
its fun being an engineer , seeing things like that and knowing you know better XD
great stuff! how about about plaster?
@alpatranss Do not mock the professor. He is simplifying it for the masses. I think you just fancy yourself as a smarty pants! ;)
To quote the chemically minded Spinal Tap
"Even the hardest concrete never quite sets,
And the Sun never sweats."
the reaction between calcium oxide and SiO2 is part of the extraction of metals am i right? it forms the molten slag in the blast furnace rite?
I think concrete may be caustic (I could be wrong) while its wet.
@tybo09 I don't know why, but your comment made me smile.
Do a video about his lecture plz.
@Digeridude
Not really, the aggregate is basically just a more sturdy substance which the concrete can hold together. This makes the concrete structure overall more durable.
Great idea for one of their videos!
These videos are fantastic
@MrTaurentino I don't think they do yet.
I love these videos :D You are great!
Cement and concrete is very cool. I can also be very beautiful and useful for flooring.
@mathiaspaul1987 I don't imagine concrete binds nearly the same amounts of CO2 as are released into the atmosphere by industry, which are probably, unfortunately, much greater due to the large-scale chemical reactions done there compared to the gradual one done by concrete.
The ultimate Macgyver channel.
hard hat, special gloves, and a periodic tie. my man
Can't go anywhere without a periodic tie.
Is that Pope building being built???
what is the purpose of the agregate in the concrete
America: Truck
UK: Lorry
the differences are both numerous and funny
More videos like this. One person, in stead of five persons, talking for five minutes.
Thumbs up. Very informative. Thank you.
Whilst the videos are not an exhaustive picture they should at least be factual. When he says that concrete is a mix of calcium oxide (lime), sand (silicates) and aggregate it is incorrect. Cement is not the same as calcium oxide (lime). Most modern cement is Portland Cement and contains the components as per dbraven's post.