Episode 532 Use Less Concrete

Adeyemi Adesina, John Orr, and Ryan Zizzo are all experts on concrete. They advise construction companies and architects on how to use materials efficiently and with minimal emission of carbon dioxide during construction and afterward, throughout the structure’s lifetime. John Orr particularly emphasizes the value of reducing the amount of concrete used in construction, for it is one of the leading sources of greenhouse gas and global warming. It is possible in most cases to design buildings that meet al the standards but use much less concrete. Another source of reductions is the use of more concrete that does not require such a long period of curing. For the video, audio podcast, transcript and comments: https://tosavetheworld.ca/episode-532-use-less-concrete.


John Orr

Adeyemi Adesina

Ryan Zizzo

Adele Buckley

Paul Beckwith



concrete, material, cement, co2, carbon, building, people, world, steel, design, questions, rebar, aggregate, pour, curing, concrete structures, numbers


Adele Buckley, Ryan Zizzo, Adeyemi Adesina, John Orr, Paul Beckwith, Metta Spencer


        In a conversation among engineers about concrete, they discussed the need to reduce the CO2 emissions associated with cement production, which is the main contributor to the problem. John Orr notes that making the Portland cement accounts for about half of the emissions of co2 and this is completely unavoidable, since the emissions come from a chemical reaction when you make clinker.


      About 4.2 trillion kilograms of cement is made every year. For Orr, the quickest and easiest way to do that right now is to use less concrete. This can be achieved by designing buildings that use concrete only where necessary, or by using alternative materials such as ground granulated blast furnace slag or pulverized fly ash. These by-products are fine powders that can be blended with cement. They have lower co2 emissions associated with them. In the UK, it’s very popular to use those materials. But they are very scarce and we actually import them from as far afield as Japan. So it’s a sort of a funny sustainability question. Orr believes instead in preventing the over-design of concrete, which results in the unnecessary use of cement and higher emissions.

       Ryan Zizzo says that in Ontario the main supplementary cementitious material is called slag from coal fired plants. But it’s not really option for us as because we ended coal-powered plants a decade or so ago, and we would have to import it from other jurisdictions. So we are using other things like fly ash, which is from steel plants; we do still have steel production in Ontario

       Design codes are currently prescriptive-based, which can be a challenge in implementing sustainable alternatives. A shift towards performance-based codes is necessary to focus on achieving specific performance goals, such as durability and strength, rather than prescribing a certain amount of cement. But a bag of cement is cheap. If it were more expensive, we’d be incentivized to be more efficient with it, which might be a good thing.

      In a typical UK building there so much wastage that 30,40 or 50% of the concrete could be taken away, and the building would still satisfy all the regulations It is also important to note that concrete is good in compression but not in tension, so designers must consider where concrete should be used and where other materials can be used instead, such as straw or hemp for walls.

      The series of Pugwash discussions is focused on carbon-negative concrete, with Metta Spencer mentioning specifically Blue Planet concrete, and the notion that the goal should be to adopt and use, not less, but even more of it.  John Orr, however, disagrees with the philosophy of using loads of any material viewed as negative carbon just because it is carbon-negative. He believes designers should use resources more efficiently.

       Ryan Zizzo agrees with John Orr and says that we need to look at the data and numbers rather than the story surrounding carbon-negative materials. He cites an example of companies that inject CO2 into concrete mixes, which only reduces the carbon footprint of the concrete by about 5%.

       Ryan also mentions the issue of curing time. The more cement you put into concrete, the faster it will cure. So to get cement to get really strong in a short period of time, then we add more cement to it. Actually, not all parts of the building need to be at full strength within 28 days, so we could design those parts to cure longer than 28 days and save concrete.

       Metta Spencer mentions Blue Planet and their carbon-negative aggregate, which is made by taking waste demolished concrete and combining it with CO2. The aggregate is so carbon-negative that it offsets the carbon emissions produced by the concrete, and the carbon emissions from the Portland cement can even be captured and used as part of the ingredients for the aggregate.

       Adeyemi Adesina sounds skeptical, pointing out that the cement component of concrete is responsible for around 70% of carbon emissions.. But Orr assures him that he has seen Blue Planet’s numbers and they absolutely do result in a negative value, but he hasn’t had time to independently review those numbers. He also notes that true carbon capture is not attached to any cement plant, and the cost of making the aggregate could make the concrete more expensive, supporting the idea of using less material.

       Adeyemi Adesina highlights the need for comprehensive lifecycle assessments of sustainable alternatives to Portland cement. While some options, such as alkali-activated materials, may be more sustainable than cement, they may still have high embodied carbon when evaluated comprehensively.

       Paul Beckwith raises concerns about concrete’s durability, especially its ability to withstand climate change impacts, such as freeze-thaw cycles and corrosion caused by salt. Steel reinforcement in concrete is also a problem area, as the steel corrodes and leads to deterioration. Adeyemi Adesina agrees that the codes were designed to evaluate durability, but now designers need again to carefully consider the sustainability of materials and detailing. In addition to the freeze and thaw problem, we have corrosion and the amount of salt going onto the road.

       Orr notes that the Pantheon, the largest unreinforced concrete dome in the world, is nearly 2,000 years old. But the key thing is that it is unreinforced. If you put steel rebar in concrete, the rebar corrodes. It rusts, it expands and it makes concrete crack.

       The experts also discussed the construction industry’s adoption of low carbon concrete, with the Federal Government of Canada’s new embodied carbon policy, set to require all federal construction projects to quantify the carbon footprint of their concrete and show that they are 10% below a typical concrete mix. This policy will apply from January 1, 2023, and will encourage the construction industry to consider low carbon materials as a standard part of construction. In the future, it may be a requirement for building permits. The experts also noted that concrete continues to absorb CO2 from the air around it after construction, highlighting the importance of using low carbon or carbon negative concrete in new projects.

      The use of algae and biochar in concrete is also mentioned, but the guests agree that these methods are not yet proven on a global scale. Overall, the panelists encourage the exploration of innovative ideas while emphasizing the need for practical solutions that can be implemented on a large scale to make a significant impact.


This transcript has been machine generated using “otter.ai.” Prior to using information from the transcript, please watch the video to catch any obvious errors.

Metta Spencer  00:00

Hi, I’m Metta Spencer, let’s talk about concrete again, It’s really important stuff. You know, it’s the most common building material in the world or material being used for anything, I guess. And it creates something like 8% of the emissions that have to worry us of carbon dioxide. So this is a big problem, but the blessing is that if we do it, right, we could turn it not into a liability for the world, but a real asset. Because you develop correctly and use correctly, concrete can actually capture and sequester carbon, and lock it up in large amounts and because we use so much concrete in the world, we could lock up a heck of a lot of this stuff that that we need to get rid of. So it will be a major factor in reducing climate change. And that’s why we need to talk about it. So what’s going on now is that the Canadian Pugwash group is holding some let’s call them inquiries into various possible ways of reducing the problems of climate change. And one of the methods that we’re considering, we’re just discussing it and talking and trying to get smart about it, is the use of carbon negative or low carbon concrete. So I have some experts with me today, some people who actually do some of the real work, they know what they know what the stuff looks like, and smells like and they can pour it if they have to. And they really know their stuff. And so, these are people these are civil engineers, in various parts of the world who are going to give me a very up close consideration of concrete and how it can be used in the world. And my, my friend, Adele Buckley will be joining us in possibly one or two other members of the Canadian Pugwash group to help me interrogate this fellas. Okay, so, first I want to introduce Adeyemi Adesina, or Yemi, who is a material scientist and civil engineer who works on developing cheap and sustainable building materials. He has been working and collaborating with people in 11 Different countries on four different continents. So good morning, Yemi how are you?

Adeyemi Adesina  02:42

I’m good, good morning, everyone. Nice to be here.

Metta Spencer  02:45

Good to meet you. And in Cambridge, or I don’t know, you’re not really in Cambridge. But you are I think you’re you’re based in Cambridge is John Orr, who’s a Professor of Engineering at the University of Cambridge in England. But he said he’s going to be in Lyon, France consulting today. Where are you today, John?

John Orr  03:06

Morning Metta. So I’m actually I didn’t make it to Lyon because we’ve had some snow and it’s not been possible to travel from London today. So I’m in London.

Metta Spencer  03:14

Oh, Okay. Well, we have snow here too,  London doesn’t get much snow normally does it?

John Orr  03:21

No, that’s why the transport system has fallen down.

Metta Spencer  03:24

Okay. Well, anyway, I’m glad that you can join us and hear it closer to home. For me in Toronto is Ryan Zizzo, who’s the Chief Executive Officer of Mantle Developments. And I was talking to him over the weekend. And he said, he goes out and he and others I suppose, go out and advise architects and builders, consult with them on how to design low carbon buildings that are, you know, sustainable and especially using low carbon concrete and so on. And now my friend, Adele Buckley is here as well. She’s not an expert on concrete, but she’s an expert on just about everything else, because she’s an engineer and a scientist, and also very important activist in the Pugwash movement. So, Adele will, no doubt have pertinent questions to ask. So hello, Adele, how are you?

Adele Buckley  04:33

Well, I’m well. I unfortunately, haven’t followed all of the concrete discussion. So I I may ask uninformed questions, but I hope to participate.

Metta Spencer  04:51

Okay, now, here’s what I have in mind today. We’ve had a couple of conversations about concrete with mostly from well, you know, from way above ground, you know, theoretical more. And I think that all of you, as engineers actually have practical considerations that you probably talk about. And, and you can share with us. Let’s say you happen to all meet in a bar after a conference and at what would you talk about? Because I know there are many, many developments of new and alternative ways of creating concrete. A lot of them have to do with, I think, probably the majority have to do with alternate types of cement or alternates to the use of cement, because cement is apparently the major source of co2. They see the concrete consists of cement, water, and aggregate, which are sand and gravel, mostly. And now they’re playing around with other things. Let me ask John, first, why don’t you talk a little bit about what you’re doing?

John Orr  06:12

Maybe I’ll start with with what you said about cement. So you’re right to say, cement is the main contributor for co2 for concrete absolutely. And when we talk about cement, we mean Portland cement, and making Portland cement about half of the emissions of co2 are completely unavoidable, they come from a chemical reaction when you make clinker. So, where my work sits, is looking at the scale of cement production, it’s about 4.2 trillion kilograms made every year. How can we cut the emissions? And for me, the quickest and easiest way to do that right now is to use less stuff. So when we talk about a hierarchy of emissions reductions, the first thing is use less cement. So that can mean lots of things which we can come back to. Below that you can talk about how you specify the material. And below that even even lower is offsetting. So how do you use less than cement? Well, one way to do it is to use less concrete, of course, so you design your buildings to be optimized you make, you know, how I would phrase it is only use concrete where you really need concrete, don’t just put it everywhere, which is quite common in construction today, because although it’s an easy material to make, we should really view it as a sort of resource constrained material, because of the co2 impact of it. And then you go to sort of how you use alternative materials, you mentioned that as well. So often people will use what we call a blended cement, and they have ground granulated blast furnace slag, or PFA pulverized fly ash, and they blend that with the cement that cuts the co2 emissions. But the issue there is those two materials are very resource constrained, there’s not much of it in the world. And so you can’t just say everybody can have blended cement, because there’s not enough to do that. And so

Metta Spencer  07:54

Sorry, I don’t, I never heard of it. So please, if I asked dumb questions, it’s always good, because, you know, some of my listeners are probably not even as smart as I am about this.

John Orr  08:09

So they’re byproducts from industrial processes. So coal fired power stations, and making steel with a blast oxygen furnace produce these byproducts, which is a sort of a fine powder, which can be blended with cement. And because they’re a byproduct, they have lower co2 emissions associated with them. In the UK, it’s very popular to use those materials. But what we do actually is we import it from as far afield as Japan. So it’s a sort of a funny, funny sustainability question where we’re making the concrete in the UK, better in inverted (inaudible) by having these bending materials, but we’re taking it from places around the world, which means they can’t use it. So again, for me, the main thing is just try and use as little concrete as possible.

Ryan Zizzo  08:50

Yeah, yeah, I’ll just add in the Canadian context, we are having issues with that as well, that one of the main cement supplementary cementitious materials is called slag. And that’s from coal fired plants. And in Ontario, if anyone’s familiar with the Ontario electricity grid, we got rid of our coal fired plants about a decade ago. So slack not really an option for us as just as John said, we would have to import it from other jurisdictions, if we want to use that as one of our materials. So we are using other things like fly ash, which is from steel plants, and we do still have steel production in Ontario. But as you know, as John was saying that these are some of these industrial byproducts are scarce. And it’s not like they have an unlimited supply supply of them.

Adeyemi Adesina  09:37

I totally agree with John and Ryan on that. And again, these bring into place the real definition of low carbon concrete. So in some cases, shipping this material might not be sustainable at the end of the day. So one of the ways to actually achieve this low carbon concrete is to find ways to use locally available materials. So for example, if you’re shipping your fly ash all the way from Japan to the UK, by the time you kind of estimate the emission, actually the transportation, by the time you calculate that do you still have a low carbon concrete? So at the end of the day to really achieve a low carbon concrete, we have to focus on the use of locally available materials. So this means that the definition of low carbon concrete is very, very relative, is very relative to the kind of material you’re using, for example, low carbon concrete, for example, uses fly ash in India, but the most sustainable way in Canada, we have less fly ash. In our case, it might not be sustainable concrete. So, we really have to be careful again with the terminology of low carbon concrete.

Metta Spencer  10:41

Okay, now, what would you do if you if you want to cut back on concrete, but you’re still building things? What do you do instead? I mean, the total amount of concrete is, if you don’t use that you’re going to use something else. I’ve heard people say we’ll do more with mass timber. Well, mass timber is also questionable, isn’t it?

Adele Buckley  11:03

People have to go for lower costs. And some of these newer concretes probably cost more. Therefore, how can you get the necessary impetus to use the new ones? If if they cost more? And second of all,I, I believe that concrete has different specs, depending on what you’re using. Therefore, if it will, if you’re trying to accommodate a certain kind of strength, it’s a different mix. If you’re trying to accommodate a certain weather patterns, particularly say cold climates, it’s a different mix. And all of these things are constraints. And then I think a major constraint has got to be that the there are government regulations, which you must adhere to. And if the government regulations have not caught up, or or even, even, you know, if you can’t use current regulations, how do you develop new regulations that support these better kinds of concrete?

Metta Spencer  12:17

This will all come up but before I switch back to our guest speakers, I want to greet Paul Beckwith, who has just joined us. Paul is also a new member of the Pugwash group. But he is an old friend to me, because he’s a he’s a climatologist in Ottawa, who makes lots of videos of his own. He knows what he’s talking about. So it’s good to have Paul with us. Adele asked a whole bunch of questions piled one on top of the other, who wants to tackle one part of it?

John Orr  12:53

I was gonna say about the cost, I think my videos frozen on cost. It’s interesting one, because yes, concrete is basically relatively cheap, because it’s easy to make, a bag of cement, it’s quite cheap. There’s an argument actually, that if it was more expensive, we’d be more incentivized to be more efficient with it, which might be a good thing. And people have talked about things like carbon taxes for decades, and whether that will ever happen, I don’t know. But to me, it’s about the design of viewing it as a carbon intensive material and using as little as possible, whether the alternative processes cost slightly more, it may not matter in a city like London, if the land is so expensive, that the cost of the building is relatively small. So just depends what you’re doing really what you’re building with it. And then you mentioned things like regulations. And, again, that that is a constraint. But in the work that we’ve done, what we find is you get in a typical building, there might be wastage in the order of 30,40 50% of the concrete could be taken away, and the building would still satisfy all the regulations. So it’s, it’s a one where we’re relatively conservative as engineers, and sometimes that conservatism is causing an unintended consequence, perhaps with co2.

Metta Spencer  14:08

So they’re just afraid, they want to make sure that the thing doesn’t fall down. So they use twice as much concrete is they really need?

John Orr  14:17

It’s sometimes that I mean, we are concerned with with safety, of course, but it can be things like making all the floor plates the same thickness everywhere, which isn’t necessarily needed and making all the columns the same size, which isn’t needed, or adding lots of concrete, just to form the walls of a building. When you could make the walls out of straw or hemp, which is a much lower carbon alternative but concrete is easy. So you kind of stick with concrete so there’s there’s lots of ways a designer can think about, you know, how much concrete do I really need and where should it go, and not put it anywhere else? It’s a material that’s good in compression, not good in tension. So maybe we only use it when it’s in compression and everywhere else we use a different material, but you know many buildings, if you go around any city, really you see a concrete frame going up. It’s concrete everywhere. So it’s it’s just thinking about what materials should go where, I think is really important.

Metta Spencer  15:12

Okay, Adeyemi you started to speak.

Adeyemi Adesina  15:14

Yeah, just want to point John (inaudible), again, one of the things we realized, actually some studies just came out is that we have a lot of over design. So let’s say for example, I’m designing the concrete for a sidewalk, I don’t need 50 MPa, I don’t need to really use an ultra high performance concrete for a sidewalk. Because when you use those things, you’re using a more your IR amount of cement, which means more emissions. So in those cases, we should really find a way to prevent the over design of concrete, which will result in lower cement consumptions. In terms of the specification, I think is actually one of the main challenges we have in implementing sustainable alternatives. There’s a lot of materials that have been developed to actually have good properties better than the conventional concrete. But the problem is that the design codes are standard we have is called prescriptive based. So which means you need to use a certain amount of cement for this particular design. But in a case where you’re not using the conventional cement what happens in decades. So there’s really a push now, to have more of a performance based code than prescriptive. So we just focus on for example, you can get this durability, this strength Yes, you can use this material. So it’s always good to go more towards the performance based random recurrence prescriptive basecoats, we are right now.

Metta Spencer  16:34

Okay, let me switch the gears because suppose the, the game is to adopt and widely use carbon negative concrete. And I have done two shows, one with Brent Constantz, who is the head of something called Blue Planet. And I know that he and his company is going into business with Lafarge Wholesome in North America and to create carbon negative concrete. And it is so carbon negative that it’s, it’s a, you want to use as much concrete as you can, because it’s going to absorb the more concrete you use of their of this carbon negative kind, the more of the world’s co2 it’s going to suck up and lock away. So the name of the game will not be how to reduce the amount of, of concrete that gets used in the world. But where else we can employ it to good effect. Is that I mean, now Okay, tell me I’m silly any of you who think I am.

John Orr  17:47

As a philosophy, I disagree. I don’t think in any material that you view as being negative carbon, and that should be an excuse to use loads and loads and loads of it. People know the similar argument you made for timber, timber in some people’s use carbon negative, therefore, over specify timber, but that doesn’t work on a global scale, because we can’t do that. And it’s a silly thing to do from a design point of view because,  why are you making a really inefficient building? It’s sort of philosophically I oppose that. So my concern, is this the blue planet, products that Brent did.  Is that right? Yeah, so whenever somebody says it’s a carbon negative material, I think we need to really interrogate what what they mean and how they’ve calculated that. The and all I’ve seen is the website. So I’m, I’m uninformed. So I am sure you know more about it than me. But in that process of Blue Planet process, they are still producing Portland cement, which releases co2 emissions. So the negativeness is coming from the aggregate and the sand. So I’m a bit concerned that that would encourage people to overuse concrete because yeah, as I said, I just feel as a philosophy as a designer, We should to steal a phrase from an old mentor of mine, touch the earth lightly. We shouldn’t be overusing resources, just for the sake of it. It’s not a good approach for my view.

Metta Spencer  18:21

Um hum.

John Orr  19:07

Okay, I…

Ryan Zizzo  19:08

I agree with I agree with that. And also, I think we need to always be looking at the numbers, right. Like sometimes we get swept away with a story as opposed to looking at the actual quantities involved. Also I think this might be an example, as John said, like, dig into that. There’s, there’s another there’s other examples I’ve heard of, for example, some companies inject co2 into concrete mixes, that’s something some people might have heard of. And in some people’s mind, that means it’s a totally carbon zero product, because all of the carbon gets injected into concrete. But, you know, again, that’s a good story. But when you look into the data, it actually only reduces the total carbon footprint of the concrete by about 5%. So I mean, I’ve, I’ve spoke to some people who, you know, I when I try to put the the topic of low carbon concrete on their agenda, they say, Oh, we’ve already dealt with that. We’re using carbon. We’re using concrete that has injected co2 in it.  Into in their mind, and it was carbon neutral, but I said, well, do you realize that’s only a 5% difference? And they said, no, no, it’s not. It’s carbon neutral. So sometimes this story can overshadow the data. And we need to make sure we’re always looking at the data, the numbers. But the one thing I also wanted to say about efficient design. John gave some really good examples of using less material, using the material more efficiently. But there’s a whole other dimension that we can use more efficiently and that’s the curing time. So concrete cures, it gets stronger over time, right. And as an industry, the typical curing length that we use is 28 days, the shortest month of the year, February, so that it’s a safety factor saying Oh, allow it to dry for a month or secure for a month. And then

Metta Spencer  20:44

Hold on, you’ve got to educate me on this because I don’t, I don’t know the thing about curing.

Ryan Zizzo  20:50

Yeah, curing. So c.u.r.i.n.g curing.

Metta Spencer  20:54

Curing, okay.

Ryan Zizzo  20:55

The more you, the more cement you put into concrete, the faster it will cure. So if you want to, if you want cement to get really strong in a short period of time, then we have to add more cement to it. So basically, as an industry, we say we say the strength that we’re rated, but this concrete is rated for say 30 MPa, it needs to hit that 30 MPA in 28 days, that’s how the concrete designers figure out how much cement they need to put in to achieve that. But if we allow certain parts of the building to cure over a longer period of time, maybe we don’t need the full strength in 28 days, maybe we can have that strength in 60 days or 90 days. So if we allow certain elements of the building that don’t require early strength to cure over a longer period of time, that allows us to use less cement. So that’s a way that we can greatly reduce our cement without, if we don’t change anything else, just picking up those elements that don’t need to be at full strength in 28 days, like foundations and footings, those aren’t going to see their full strength for years, right until the building is fully occupied, and there’s a party and there’s a storm all at the same time. That’s not going to happen in 28 days, it’s physically impossible for those loads to be met. So it really makes no sense for us to require some elements to have 28 day strength.

Metta Spencer  22:20

Okay, well, let me let me explain what little bit I understand about any carbon, negative concrete. And the Blue Planet, I sort of kind of got part of it. And what they do is it’s not the, the cement that they’re trying to to reduce. It is the it is a change in the composition of the aggregate. And they simply create aggregate by taking waste, demolished concrete, and smashing it and combining it with co2, and presumably some secret formula, which they they get their co2 from some smokestack that’s right next door. They always have to be close to sources, because I gather that the cost of concrete of any kind is largely, predominantly a function of the distance, you have to move the materials. So they combine these old demolished concrete with co2 and create aggregates of little pebbles that then they mix with with the cement in the usual way. Well, this, this aggregate is so carbon negative, that it greatly offsets the carbon emissions produced by the concrete. But it one of the other features of this is they don’t necessarily have to do it this way. But they can use the concrete or sorry, the carbon emissions that are produced during the making of the Portland cement. They capture the the emissions from the Portland cement and then use it as a part of the ingredients for the aggregate. In any case, the aggregate is supposedly the I’ve heard the the expression 440 kilograms of carbon per what is it? Would it be a cubic meter of concrete or I don’t know what. But at any rate, that’s apparently stupendous amount of carbon that gets locked up in this aggregate. And that is the approach. Does anybody want to

Adeyemi Adesina  24:38

I will still go with what John mentioned earlier.  So even though the cement is just about 50%, the component of concrete, it is responsible for around 70% of the carbon emission. So, let’s say we have a carbon negative aggregate is that really turning the old concrete to the carbon negative? So we really have to quantify these numbers very well and be careful with what we really call it negative concrete. Because again, aggregate is a huge volume in concrete, the impact on carbon emission is very low compared to that of cement. So, …

John Orr  25:16

if I just if I say what I said earlier, when I looked on the website, the numbers that they have absolutely result in a negative value, right, so, the numbers are there. What I what I don’t have, for my own investigation is a is an independent review of those numbers. Anybody write a number on a website? So I’m not saying it’s wrong? And I’m not saying it’s impossible, absolutely mineralization is a thing, and it’s a way to capture carbon? Absolutely. It’s the science is there. I just haven’t been able to look through that in any more detail to really show that it’s correct. And the second point I would make is carbon capture and storage have been talking about for a very, very long time. How much is available? How much you have, I don’t think any cement plants are fitted with true carbon capture. There’s about 6000 cement plants in the world, I would say zero, have it attached to them. And maybe CCS attached to other plants? Of course, I don’t know. So how much can they actually receive from that those sources. And then what does it cost if it if this process makes the aggregate very expensive, then it’s actually supports my previous point about using less material because the concrete can be more expensive. And therefore you should be using less not more. Or you would be using less as a designer as a contractor who’s been more expensive.

Adeyemi Adesina  26:36

And I think this is why it’s good for any initiative approach to reduce the carbon emission of concrete to really do a comprehensive lifecycle assessment. There are a lot of various promising options to do the some of it is actually alkali activated materials, where in some cases, you’re using heat curing, you’re using sodium silicate, with high embodied energy. So even though it’s a sustainable alternative to Portland cement, by the time you do a comprehensive lifecycle assessment, that material actually as high embodied carbon compared to cement, so it’s always good to really evaluate, like, a comprehensive lifecycle assessment of the sustainable alternatives to Portland cement.

Paul Beckwith  27:19

I’d like to add on to that comment, actually, because you may have talked about it before I arrived, but the what, when concrete when concrete buildings are designed or struck general concrete structures, what is what is the lifetime expected lifetime of these structures? You know, is it like, I mean, 30 years, 25 years, I mean, I see a lot of, you know, bridges, for example, concrete bridges, where you know, in Canada, we get the salt on them. We get corrosion of the rebar, we get pieces crumbling, and I’m right now I’m in Montreal at the conference on biodiversity of the Cop, 15 and Quebec and roads, bridges have been notorious for chunks of rock falling down onto the roads, much faster than you would expect based on the engineering lifetime spec. So, you know, I guess that’s the question, you know, shouldn’t we be talking about the durability of concrete, because if it’s capturing carbon or not, in aggregate, you know, if it only last 20 years, or 30 years, it’s not considered it’s not a very long term store of the carbon. And I guess you get mineralization. And so it’s just rock that you result of when it crumbles, but, you know, why? Why can’t we make concrete to last longer? I mean, the Romans mixed concrete rock materials with saltwater, built structures in the ocean that have lasted 5000 years, so their concrete can last 5000 years, you know, ours lasts 30 years. So what’s the problem, we’ve forgotten how to how to make it properly?

Adeyemi Adesina  28:57

Trying to figure it out. So I should also mention that in terms of standard and codes, like for example, a common example is freeze and thaw. Um, ideally, when these codes were designed to really evaluate the durability, you probably have like a cycle, like maybe you have minus five this week, zero next week, and maybe again, minus five. But with the impact of climate change, not everything we say. And within a week, you could have like four different cycles, maybe minus five, zero 10, again, minus five. So there’s really need for us to again, as I mentioned, really consider durability, and sustainable design, because again, if your concrete is lasting longer, it means you don’t need additional material to repair or to replace. So at the end of the day, is a sustainable like concrete, so we have to really consider durability. The sustainability of concrete generally.

Paul Beckwith  29:44

Yeah, yeah. So I would question the, the rationale behind pouring concrete when we have temperatures that could swing, you know, far above them far below zero. So maybe we shouldn’t be building or pouring concrete in the spring and fall seasons in Canada any longer for example, I mean, I’ve often talked about whether whip lashing you know where we go from one extreme to the other, depending on where your location is relative to the jet stream, you know, the meteorological reasons why we’re getting these, these huge swings. But, like in Ottawa, for example, you know, they’ve had a huge problem with with sidewalks, because of all of these numbers, increased numbers of freeze-thaw cycles. So if you’re in a city where, where you are very close to zero, you’re going to be swinging above and below it numerous times, you know, maybe 25 times in a month, for example, you know, at night, it always goes below zero, during the day, it always goes above zero, you can have that happening 30, 35, 40 days, you know, in a spring or fall season, you know, when it’s in the winter, it’s well below zero would never goes above zero, you know, you’re in a different regime in the summer, you know, it’s always warmer than than zero. So you’re also in a different regime. So, are you aware of, of how much the lifetime of concrete is degraded when it’s when it’s poured, you know, in the end, experiencing these huge swings in temperature, because I would expect, you know, this lifetime would be severely degraded, maybe this is part of the problem with, you know, concrete structures sailing in 20-25 years, when they should be lasting much longer.

Adeyemi Adesina  31:28

So I’ll say from design perspective, again, we have more theoretical values for those. But this is quite different from reality. So for example, in addition to the freeze and thaw, we have corrosion, we ask, we are using a lot of salt going on this road affecting this. So like, we have this theoretically, when in reality is quite different. So we have to design we have to have and answerability design, we have to find a way to incorporate this.  Right now to we have materials that are very durable that can be used for this application,

Metta Spencer  31:56

Affecting the durability of the concrete. Is it the climate? Is it the salt? Is it something else? Is it the quality of the materials? And, is it known in advance how structure is going to last before you pour it? And what Paul was suggesting was that maybe it makes a difference. whether you pour the concrete in warm weather or cold weather, I don’t know this, this is all a complete mystery to me.

John Orr  32:27

So the first question you asked about design life. So typically, you would say more than 50 years for a building more than 100 or 120 years for a bridge, right. So we do think about design life, we want our stuff to last for a long time. And you’re absolutely right to point out that the Romans, the Pantheon is still the world’s largest unreinforced concrete dome in the world. And that’s what, two and a half, 1000 years old. But the key thing though, is unreinforced. So the issue with concrete is you put steel rebar in it and the rebar corrodes as I just mentioned, it rusts, it expands and it makes a concrete crack. And then as you said in, I think he said Montreal, you see the bridges are starting to deteriorate, it’s a concrete falling off. So that was probably very much related to when the bridge was designed likely the 1960s. I think there’s a few famous bridges in Montreal from the 60s which are sort of deteriorating. So what you have to do with concrete is you have to protect the steel from rusting, right? And you do that by having what we call cover the distance from the steel bar to the outside world. And you think about how permeable the concrete is, from the outside world going in to things like salts and chlorides. And other deteriorates can don’t get into the concrete, but it’s the additional steel, which is the key problem.  Concrete on its own, it’s fine, as we’ve seen with the Roman stuff, but the steel rusts. So what we do now is we think carefully about how you protect the steel, or even. And this does happen in Canada, I think use alternative materials like fiber reinforced polymers, which are basically plastics, which don’t corrode and therefore don’t suffer the same problem. So you’re absolutely right to point out that, you know, some historic uses of concrete haven’t been so great. And even maybe modern ones haven’t been so great. But we do know that that’s an issue. And it’s really the job of the designer to try and prevent that deterioration from happening. And and just final point on design life, you know, 120 years. Isn’t that really that long in terms of, of a city, and I would really hope that we were designing for much, much longer than that. And that might then again, questions, should you put steel in concrete? Maybe the concrete should just be sort of compression only structures, arches, vaults, without materials which are going to corrode over time. So again, it’s about thinking what what’s the material really good for and where should the material go?

Metta Spencer  34:45

Oh, well, now how about reinforced concrete being abolished? I mean, I assume that the thing hasn’t been even used, except in the last 50 or 100 years. And now it’s It’s in everything isn’t? Could you? I mean, I’m in In a building now 23 storeys tall, I hope they’ve got steel in this concrete, I’m not sure, but it could, are you suggesting that you could still go ahead and build a building like this without concrete, I mean, without steel reinforcement?

John Orr  35:19

you’d be very difficult to build a concrete building 23 storeys tall without reinforcement. So I think what I’m saying is, as a designer, think very carefully about what you do in terms of detailing to either protect that reinforcement, or to use something else, you know, build out of timber, you know, there are other materials around.

Ryan Zizzo  35:37

Yeah, there are materials, there are timber buildings that are over 20 storeys, actually, and we’re seeing a strong direction towards more and taller timber buildings. But we can also create, you know, more innovative new solutions that use that still use concrete, as was said, by John in compression, but have another material for the tension. And they’re in that other material isn’t covered by concrete that’s going to degrade. So you know, there’s some composite material elements that have concrete on the top, and then they might have like a fiber, fiber material on the in the tension without concrete covering or something that’s not going to erode. But just to go back to Paul’s earlier point about the freeze-thaw cycle. My understanding is that it doesn’t matter when it’s poured, it’s not about this free thought happening during the curing time, it’s just about the concrete degrading over the life of it. So just to make that point clear, it’s freeze-thaw just impacts the concrete, it just it just accelerates its degradation at any time of year. It’s not about being poured during a period of freeze thaw. So that yeah, just wanted to make that point to clarify.

Adele Buckley  36:47

I, there are a number of large companies who do construction. And I know that they have all sorts of questions of design to consider when constructing but is there any possibility that all of them would decide to include, you know, low co2 content as as one of their criteria? I mean, there’s so many other things that I’ve heard you talk about that, it seems to me that I don’t, I don’t sense that the industry as a whole has decided that it should do this. And so they have to do it, it doesn’t just have to exist as a process that can be used, it has to be that everyone in the industry decides we’re going to do it. And even if it’s now imperfect, if if it’s just part of the regular way of doing things, I think gradually over the years, it will, it’ll probably get better. So what makes you decide to use it?

Ryan Zizzo  38:03

So I can comment on that. And you’re right, it is most people aren’t doing this right now, this is very much a nice to have, not a neat to have on a lot of people’s agendas. But that’s changing. In three weeks, when the clock turns to 2023, then Federal Government of Canada’s new embodied carbon policy will kick in and all federal construction projects as of January 1, onwards, we’ll have to quantify the carbon footprint of their concrete and show that they that they’re 10% below a typical concrete mix. So this is just going to be brand new in three weeks, it applies to all federal construction, and then they have a plan to add structural steel as a new material that will have to be similar assessment will have to be done in 2024. So it starts there at the federal government, and then it’s going to trickle down to you know, provinces or municipalities that will adopt this, and then, you know, best practices of various construction firms. So we’re at the very early days of this, you guys are all ahead of the curve to even be asking these questions. But I like to tell people in five years or 10 years, this is going to be a requirement for your building permit, right? It’s just hasn’t been on the radar up until now. When I started my career as a green engineer. 15 years ago, we were having this discussion with energy modeling was only that most advanced projects that were going for LEED certification that did an energy model. And now it’s every project basically does that to get their building permit. So I think we’re at the same point with lifecycle assessment and low carbon materials that right now it’s the leader’s is doing it or people in a very, you know, stringent jurisdiction that you know, if Toronto wants to lead and make a requirement for that, but over the next 10 years, we’re gonna see this trickle down to become a standard, a standard part of construction.

Metta Spencer  39:45

I just love that. And in fact, the first show I did, we had a Doug Hooton, who’s an expert from University of Toronto, retired now, and and he basically told me, you know, the project that Pugwash doing, which would if we investigate things we would wind up recommending to the Government of Canada, that it require in the future that all of the concrete that it pays for for its own funded infrastructure should have to be low carbon or carbon negative concrete. And he said they’ve already they’ve already passed legislation, basically, to that effect. So the good news is that we’re way behind the curve. But at any rate, that’s one of the one of the things that we might, we will still have to look at, to see whether or not you know, what kinds of recommendations Pugwash wants to make. But But I had one further thought, which is that I, I’m only learning, you know, a little bit because I don’t have any background as a scientist. But, But as I understand it, the cost of a concrete once you created a building that or sidewalk or whatever, that concrete continues to absorb co2 from the air around it. Is that correct?

John Orr  41:12


Metta Spencer  41:13

So even if the thing gets old, is there a point where it’s saturated? Is there a certain curve at which it absorbs co2 and then it gets all full of it, and it can’t, anymore, or do anything to make it make the structures that you pour, continue to, to grab more and more concrete and hang on to it longer?

John Orr  41:42

Well, so concrete does carbonate. So co2 works its way in from the outside world into the concrete. As a designer, what you try and do, what you need to do is to prevent that carbonated layer reaching your steel reinforcement. So again, it goes back to that steel that wants to carbonate, the carbonation reaches a steel, the steel loses its passive protection from corrosion. So yes, it does carbonate, but it’s a very slow process. And you actually don’t want it to go too far into the concrete when you’re using steel. So yeah, that’s the quick answer, it is not really a process which sucks up much co2 In my book it I don’t think it’s something we can rely on.

Metta Spencer  42:24

Okay, but this the, the system that’s operating a scientific process is the same for two of the measures that Pugwash is considering. One of them being whether rock weathering, enhanced rock weathering, where we which powder, the idea is to powder, basalt and other kinds of rock and spread it on the soil, and not only to make the soil more fertile, but also because powdered rock is has more surface area and will absorb more co2, and therefore it becomes a significant measure for reducing climate. But presumably, it it even if you took all concrete and smashed it up and spread it on the soil, might not do anything for the fertility of the soil, but it would have the same effect, as we’re talking about using basalt and, and other kinds of rock, is that right? The principle is the same.

John Orr  43:33

The principle is the same. If you if you break up a concrete beam into rubber and spread it out on a car park, it will suck up more co2, but you need to leave it there for quite a long time. And I don’t think it’s really feasible in terms of volumes to have vast swathes of the land covered in concrete rubble, I don’t think the society will be very happy with that.

Ryan Zizzo  43:54

And it’s reabsorbing some of the carbon that was released during its production, right? So it’s never going to suck up more carbon than it was used to make it. So it can never be in like net negative, and it could, you know, if it was 100% effective, which it isn’t, but the most you could ever reabsorb was the amount that was emitted when it was created from the chemical process part of it not even from the fuel that got for the heating process. So it would never be a solution to reverse climate change, for example.

Metta Spencer  44:26

But salt could be but I think probably the, the level, the amount of co2 that it can absorb is not comparable to the really extraordinary amount that the Blue Planet people claim that they are able to absorb and retain, lock up in the concrete that they make. Ryan you’ve looked at the numbers right? They are making…

Ryan Zizzo  44:52

I haven’t actually, no. I know about the process, but I haven’t done any kind of third party…

Metta Spencer  44:56

I guess John looked into it, right?

John Orr  45:00

No, what I say metrics, I looked at their website. So, and I haven’t seen any sort of third party review of those numbers. I don’t know if they? Yeah, I don’t know enough about what they’re doing to say if those numbers are correct, although I’ve seen that they are negative.

Metta Spencer  45:14

Let me,…

Paul Beckwith  45:15

Can I ask you a couple of questions Metta? The, for concrete structures that are that are going below sea level? Okay, for causeways, etc? Are they still reinforced concrete? And did they do something special to them to keep the ocean water seeping in and corroding the rebar. And also, what, how could an insulator or conductor of heat is a concrete so you know, when you have a bridge, and you know, that doesn’t get really do get an unequal temperature distribution within the concrete? And if you have multi-phase concrete, so you have put rebar in it or some other substance, there’s going to be different thermal expansion coefficients of these materials, and that’s going to cause cracking and causing seepage of that’s going to be exposing rebar, whatever’s in the concrete to the external environment quite quickly, you know, most concrete does crack to some extent. And, you know, I’m concerned about Florida, we had an example of a concrete structure on the beach, and, you know, with tidal surges, etc. tropical storms, you know, where you get storm surges, you know, the, the basis of these buildings are in bed or under sea level under seawater for, say, you know, weeks at a time before it dries out. And then we’ve had some building collapses on coastlines of Florida, probably because of the foundations being undercut by the flooding from storm surges. So I know, I know, there’s a lot of questions in there. But those are all related to the deterioration of concrete, because of climate and weather events, etc, exposure to sea water.

John Orr  47:02

I mean, I can try and tackle a few, the thermal coefficient of steel and concrete is about the same. So there’s not a differential between them. Concrete does have a high thermal mass. So it’s a bit it’s like stone. So it’s a massive material, which is good if you’re in a building. So you can use that property to help you with sort of natural ventilation, heating, cooling all this other space, because it sort of dampens the changes in temperature over a day. So that’s really useful way to use concrete. You mentioned about a bridge deck having a gradient of temperature across it, it it does, as does any bridge like a steel bridge, because the top surface is exposed to the sun and the underside isn’t. So you can see how that’s that’s going to happen. It’d be cooler underneath. And then in design codes, there’ll be all sorts of temperature profiles that people use to work out what’s the effect on the structure, which will be considered by the designer? So yeah, that those are the three I remembered. Sorry.

Paul Beckwith  47:57

Okay. Okay. Thanks. but  I mean,

Adele Buckley  48:00

I think we’re running out of time, but I think I have a burning question that I just want to put before us. When you talk about the data that Blue Planet puts forward, I think they need and everyday industry needs a process known as environmental technology, verification, with which I have had a lot of experience. And essentially, the data that supports whatever claim you’re making, is examined in specific processes by a third party. And therefore you actually can take confidence in the data, or, or not, depending on what happens. So I think a third party needs really to examine their data and do that. And now there are pros, there are government’s back processes in Canada, the US and Europe, at least to do that. Anyway, that’s what I think Blue Planet needs in order to be credible.

Metta Spencer  49:02

Okay. I can’t recall exactly what they say. But I remember something like this, that the amount of carbon that they expect to lock up is something such that if 16% of the concrete being poured in the world were made of their concrete, it would handle all of the current emissions of human co2. And that so it would handle all of our, all of our climate problem. Something like that. It was just an astonishing figure. I didn’t think that I should have to be able to quote it. So I didn’t look it up first, but I can I think what I’ll do, I’ll put it in the comment section because under when we post this video, which I’ll do tonight, on our website, there’s a place that people can discuss it below the comments column. So you can put you guys can put any further information you want to add in that comment column and anybody watching this can go there and I will have the exact quotation that they claim. Now if Adele is right, and they they need to have a third party investigate it, of course that I can’t answer for that. But I can say that one of the things I want to get in one of these shows coming up soon is somebody from Lafarge Wholesome, because those two are the biggest concrete producers anywhere I gather. And in Canada and North America at least. And they will they have entered into a deal with Blue Planet to create plants to manufacture their this type of aggregate in Canada. And I want to get somebody from one of these companies to tell us what their plans are. So I think that Lafarge Wholesome would not have entered into this if they found that the numbers are suspect. That’s my guess, anyway.

John Orr  51:21

And to be clear, metta, I’m not I don’t think anybody’s saying they are suspect. But I, when I’m asked about these things, I like to see what we call an environment environmental product Declaration, which is an order of what the actual carbon count is. And that for me, is all I’m saying. And I think that’s really what Adele is saying also. As I said earlier, mineralisation technology definitely is a thing, it definitely is scientifically proven that you can do this. But the numbers for me, I just, I’m not putting my reputation on the line for something I’ve only seen a website for.

Paul Beckwith  51:35

And maybe everybody should be searching for that Roman concrete formula. You no, I mean, we I don’t I’m not aware of any concrete produced today, that uses saltwater as the mixture, especially if it’s got metal rebar within I mean, that would be ridiculous. But they did use, you know, saltwater mixtures with to make their concrete, you know, in some of their structures on coastlines that has lasted 1000s upon 1000s of years.

Ryan Zizzo  52:27

And I’m gonna post Metta when you send up the link to the comment section, I’ll post a new report or not not so new anymore. But last year, the National Research Council published a report on strategies for low carbon concrete that is written for a non technical audience. So I’ll share that so that everyone can review it and refer to it.

Metta Spencer  52:47

That’s very, very useful. I’ve seen references to things that were really offbeat one paper was talking about adding biochar to concrete. That’s That sounds pretty far out to me. Does anybody know anything about that? No.

Paul Beckwith  53:07

So that’s basically adding charcoal. I mean, that would really weaken it. I would think unless it was very finely ground, you know, because we haven’t talked about sand. I mean, sand, you know, is a sand all equal, as far as concrete goes, I mean, whether it comes from the ocean, whether it comes from you know, crushed rock. I mean, it’s one of the highest volume, things that is being mined globally, you know, that people don’t think too much about this basic sand. People even talk about shortages of sand. You know. 

Ryan Zizzo  53:41

We’re already over time here. So I don’t think we can get into all the other materials.

Paul Beckwith  53:45

Yeah, yeah, yeah. But yeah.

Metta Spencer  53:46

It certainly is interesting. And I’m open to hearing about novel ideas. Although this has been, I think, a very conservative bunch of people, because what you’re saying is, just be careful. And,… I think

John Orr  54:04

No I think Metta what I’m saying is not conservative at all, I’m saying use much less concrete, which is very far out. People don’t like that they don’t, they don’t tend to do this cutting your concrete use by 50% would cut cement emissions by 50%. And can cut our demand for sand by 50%. And we can do that right now with all the technology we have already. So actually, I’m not being conservative at all. I’m saying we’ve got lots that we’ve we can do right now, which will have a huge impact on co2 emissions, and that can happen

Metta Spencer  54:32

More or less conservative. Then proposals. Like there’s one that I’m trying to reach a guy to be on the show. He’s talking about using algae in concrete, and I think little, little it’s not just algae, but it’s also little microscopic critters that have been shells or something. So you know, there are a lot of very far out ideas that being considered what I would consider yours pretty conservative. John, in comparison to that, and to the biochar notion.

John Orr  55:11

Always mean’t to always think about scale, can you reach the scale that you need? If you can make one cubic meter of algae concrete and I know nothing about it one meter cubed or this idea, it’s not making any impact on a global scale. So it has to be something which can be done globally. So yeah, I but we should always encourage wacky ideas, because that might just be the solution to climate change, you never know. So.

Metta Spencer  55:35

This has been fun. Thank you very, very much.

Paul Beckwith  55:38

Okay. Thank you. Good bye.

John Orr  55:39

Thank you. Bye, bye.

Metta Spencer  55:41

Take care, bye.  Project save the world produces these shows. And this is episode number 532. Watch them or listen to them as audio podcasts on our website tosavetheworld.ca you can also share information there about six global issues. To find a particular talk show enter it’s title or episode number in the search bar, or the name of one of the guest speakers. Project save the world also produces a quarterly online publication Peace magazine. You can subscribe for $20 Canadian per year. Just go to pressreader.com on your browser. And in the search bar enter the word peace, you’ll see buttons to click to subscribe.



To Post a Comment

Please wait a few seconds for the comments to load at the bottom of this page. Then read the ideas other people have shared and reply or add your own knowledge. The space for comments is in a pale font. It’s good to give your comment a title by selecting it and clicking the “B” (for “boldface”). And you can italicize passages with the “I”, indent, add hyperlinks (with the chain symbol) or even attach a photo or graphic from your hard drive by clicking the paperclip at the right side of the space. Have fun with it!

Notify of

Inline Feedbacks
View all comments

Here’s info from their website:
Blue Planet’s patented mineralization technology is the only known scalable method for capturing and permanently sequestering billions of tonnes of CO2. Our process can use dilute CO2 from any source, at any concentration, and turn it into valuable building materials to enable carbon capture at a profit. This mineralization process combines CO2 from any source with alkaline industrial waste, to make high-performance lightweight aggregates that sequester and permanently store CO2.  Each tonne of our aggregate permanently mineralizes 440 kg of CO2, preventing it from ever leaking or accumulating in the atmosphere. 
If we replace just 16% of all aggregate used today with Blue Planet Aggregate, we could achieve the CO2 storage needed by 2050 to keep temperature rise below 1.5C.
Blue Planet’s partners now include Mitsubishi Corporation, Chevron, Knife River, KDC, Calpine, Lafarge and Holcim.

Thanks for having me on the show – it was fun. For a great resource on low-carbon concrete, check out the primer linked from this article.

Select the Videos from Right

We produce several one-hour-long Zoom conversations each week about various aspects of six issues we address. You can watch them live and send a question to the speakers or watch the edited version later here or on our Youtube channel.