Tech Refactored

S2E13 - From Dust to Structures: 3D Printed Housing from Local Soils

October 28, 2021 Nebraska Governance and Technology Center Season 2 Episode 13
Tech Refactored
S2E13 - From Dust to Structures: 3D Printed Housing from Local Soils
Show Notes Transcript

3D printing technology could revolutionize the cost and sustainability of housing across the globe. Not to mention, the environmental impact of concrete use (spoiler: it’s not great) is of increasing concern. The key to shifting away from concrete may be reviving the traditional use of local soils—for a 3D printing process. Here to talk to us about his work helping to develop these new 3D printing techniques is Dr. Sarbajit Banerjee, Professor of Chemistry and Materials Science and Engineering at Texas A&M University.

Disclaimer: This transcript is auto-generated and has not been thoroughly reviewed for completeness or accuracy. 

[00:00:00] Gus Herwitz: This is Tech Refactored. I'm your host, Gus Herwitz, the Menard Director of the Nebraska Governance and Technology Center at the University of Nebraska. Today we're talking about new developments in 3D printing technology that could revolutionize the cost and sustainability of affordable housing across the globe, especially in the developing world.

The key to these developments is the use of local soils as base materials in the printing process when combined with individually tailored additives. This locally obtained earth can yield 3D printing materials that is strong and durable enough to displace the use of. Here to talk to us about his work, helping to develop these new 3D printing techniques is Dr. Sarbajit Banerjee, Professor of Chemistry and Material Science and [00:01:00] Engineering at Texas A&M University. Sarbajit, welcome to the show.

[00:01:05] Sarbajit Banerjee: Thank you for having me. 

[00:01:07] Gus Herwitz: So let's, uh, just start with, uh, the, the current state of affairs with infrastructure. Um, what, what are some of the, I, I guess let's even start a step earlier then.

Can you tell us about concrete and some of the challenges that come with concrete? Well. 

[00:01:24] Sarbajit Banerjee: So yeah, concrete is something that, uh, modern economies, our modern build environment relies very extensively on. It's, uh, become ingrained into our infrastructure at every level. Uh, but of course it comes, uh, with a tremendous environmental cost. Okay? It's a low cost material because the, the raw, uh, components of concrete are readily available. Um, but it comes to a tremendous environmental cost from plinking, from, from transportation of the material. So I think, you know what, what has happened over, uh, over the [00:02:00] years, uh, is, is the world has moved to where it's more homo, homogeneous, uh, construction across the board.

Um, and it's, it's given us perhaps greater standardization of construction, but, uh, the built environment, um, has, has in some ways become, uh, you know, very homogenous across the world. But it's come at an environmental cost, which is, which is the carbon emissions of concrete. 

[00:02:26] Gus Herwitz: And well, what, what are some of the sources of, uh, these emissions?

Is it production? Does the concrete itself produce carbon? Are, are there, uh, uh, external sources?

[00:02:35] Sarbajit Banerjee: Right. So concrete is, is pretty carbon intensive, um, across its entire life cycle. Um, the production of Concrete, uh, Clinking, the transportation of Concrete, uh, uh, pretty much every step involved in production in, in the use of concrete and transportation to the built environment ends up, uh, you know, having a substantial [00:03:00] hardened.

[00:03:00] Gus Herwitz: Okay. And, uh, just for our listeners, uh, uh, you're referring to the, the clinking step. Uh, can you explain what that is?

[00:03:08] Sarbajit Banerjee: Uh, pretty much the entire life cycle of concrete, um, is, is pretty carbon intensive. It begins with quarrying, uh, limestone or other raw materials, right? So crushing of the material, uh, tends to be incredibly, uh, energy intensive transportation to the cement plant mixing of the raw materials, um, milling and drawing of the raw materials, uh, preheating the materials.

Um, usually, um, there is a, the burning of the raw materials in a. Um, releases a lot of co2 and then cement, clinker, cooling, um, I mean it's, it's, it's cooled down. Um, then the, the cool cement clinker is stored and it's usually then grinded with, with something, some sort of other, other material like gypsum or something like that.

Um, and then transported to, uh, the point where it's, it's actually used in the built environment, right? So there's [00:04:00] a lot of inefficiencies across these steps. And, and some of them are, are, um, you know, uh, inevitable in, in the fun, in the basic chemistry of concrete, um, where, um, you're, you're, uh, taking limestone and you're, you're heating this up and releasing CO2 into the environment.

[00:04:17] Gus Herwitz: So why, why do we use concrete so much? 

[00:04:22] Sarbajit Banerjee: So really great structural properties, um, especially under compression. Um, that's really been, um, the, the primary, um, reason for this, um, and, and especially in many parts of the world, is a huge emphasis on. Reinforce concrete structures for building out, you know, large scale infrastructure.

Um, it can bit stand, uh, it's, it's pretty much unparalleled in terms of its strength there and load bearing properties and, and, uh, it's, it's also something that is incredibly low cost because, It comes from limestone. It's originally derived [00:05:00] from limestone, so not a very expensive material. It's also a fairly, you know, earth abundant material.

And it's, um, also fairly versatile in its chemistry. So you can mix in different types of locally sourced aggregates, for instance, um, to make your cement. And, and so, uh, it's a solution that works well at low. Um, pretty much across the world. 

[00:05:23] Gus Herwitz: So what are some of its limitations? Has concrete, Uh, is concrete, like a diamond is concrete forever.

[00:05:32] Sarbajit Banerjee: So Well, I think, um, that's a very interesting point, right? There's alternatives. So carbon emissions are a huge, um, uh, problem. Um, you know, concrete is part of what is known as, uh, the heart debate sectors, right? So, as. Um, as people start to take a look at the, uh, where our carbon emissions are coming from, right?

And it depends on how exactly where you draw the boundaries, but you know, five to 7% of carbon emissions from [00:06:00] concrete, depending on, on some sources. And, um, and it's something that is. In built into the chemistry of the most common types of cements that are used. So it becomes very difficult to resolve.

So that's one of the reasons this is such a hard debate sector. Um, uh, so, um, also concrete has other limitations in terms of its, uh, you know, the forms that you can. . Um, uh, and, and essentially there's, uh, it's, it reliance entirely on concrete starts to limit, um, the sort of productivity of, uh, the construction industry.

You know, and this is a huge problem in general. So, uh, you know, 7% of, uh, the working population, um, across the world is engaged in construction. It's, it's one of the least productive sectors out there, right? And, um, it's, it's. Reliance on concrete is not the only reason. It's not as productive, [00:07:00] but it certainly contributes to, um, the relatively limited imagination, uh, that people have had in terms of the built environment and in terms of holding back what the built environment could look like.

Um, so I think if we move away from concrete, there's a lot more opportunities for automation and for doing interesting forms, um, and for really having a built environment that is more in sync with it, the local, local conditions, the local 

[00:07:25] Gus Herwitz: climate. And, and how you talk about, uh, the productivity of the, the building trades.

How is that, uh, productivity changed over time? Has it always been, is it always going to be, uh, low product? Um, 

[00:07:40] Sarbajit Banerjee: I, I don't think it has to be right. Um, but certainly, um, there is a concern, um, that we're going, we're sort of getting concrete. Um, this, this often happens, right? There's such a large sunk cost in concrete, right?

Um, as society invests in specific technology, it [00:08:00] becomes, uh, more and more difficult for game changing technologies to come in. And, uh, make a difference, right? Um, so we've become so tight to concrete for something else to come and take its place. Um, it's going to have to dislodge all of the issues that, that have, uh, uh, you know, uh, that are the legacy of decades of building with concrete and.

[00:08:23] Gus Herwitz: Uh, what, what do we build with concrete? Obviously, buildings, infrastructure, um, a around the world, do our homes, uh, uh, built with it. Is it used for residential applications? 

[00:08:37] Sarbajit Banerjee: Um, so less so in the US but across the world. Increasingly reinforced concrete is, is, uh, you know, very commonly used in, in, um, China, for example.

Um, there's incredible amounts of reinforced concrete, both. Large scale buildings, uh, and um, as well in, as in public, public buildings, um, pretty much [00:09:00] across the build environment. Um, I would say concrete tends to get used a lot more, um, whenever you have large scale infrastructure, right? So in now in. In a lot of parts of the world, uh, that are more densely populated, you're not building as many single family homes.

Um, so you are therefore building large apartment blocks and such where there is greater reliance on con reinforced concrete. One 

[00:09:24] Gus Herwitz: of the great things or useful things about concrete, um, is that we can pour. So since you can pour it, uh, you, uh, you can make molds. Uh, you, you use a term forms, You structure the forms and you just pour the concrete in, um, and let it hard in, which gives us a lot of flexibility in the, the shape, the structure, uh, the form, uh, of, uh, the concrete.

Plus it's relatively quick. You assemble the forms. They can be predesigned, preassembled, um, and you have a, just a lot of flexibility, low cost, uh, in construction. What are [00:10:00] the, the limitations on how we can pour and form concrete? 

[00:10:06] Sarbajit Banerjee: Well, so there's, um, only, and this comes down to the mechanical properties of concrete.

Um, there's only certain types of forms that you can viably do, um, without, you know, um, losing structural integrity. Um, so, so there's some limitations in terms of what forms are viable. There's some, um, limitations in terms of. Uh, what sort of construction methods can be applied? Um, and, and so it's, again, it's an incredibly versatile materials, which is why it's become so popular.

You can mix it with all kinds of locally sourced aggregates. Uh, but, uh, in terms of. Economy and materials use, um, it doesn't fully, um, get you to where you could be. Um, but given, uh, what we are seeing now with [00:11:00] modern methods for construction, 

[00:11:01] Gus Herwitz: so this, uh, starts to bring us towards what we're really here to talk about today.

Um, how, how, what, what is 3D printing and how does concrete relate to 3D printing?

[00:11:14] Sarbajit Banerjee: Yeah, so 3D printing really allows us to build up, you know, forms, um, uh, out of, uh, pretty much any material that you can extrude or that you can, that you can print in, in any, any sort of manner. And, um, Now concrete, uh, there's a lot of work going on in 3D printing of concrete as well.

Um, the challenge, uh, it's, it's not trivial is, is how do you get, um, the concrete layer to hold the weight of the next layer that you print on it? Um, because, uh, fast as it is, uh, the setting of concrete, it still takes a bit of. And so there's an intense interest, an interest intense race in trying to [00:12:00] figure out how we could, um, get this curing process, which, uh, allows the concrete, it becomes sort of weight bearing, um, or for that matter, for any structural material to bear the weight of its next layer that's put down.

How do you get this to happen as fast as possible? So that you could print large scale structures as quickly as possible. 

[00:12:20] Gus Herwitz: So, uh, I'm familiar with, uh, 3D printing at a, a small scale, at least a little bit. I've seen some videos of, uh, 3D printers, printing houses or entire buildings. And th they're a little bit different than the, uh, little plastic 3D printers that I've seen.

But with, with the small ones, um, Kind. You have the, uh, uh, device that's, uh, extruding. The, the material and the material's sticky. It all sticks together in layers. Um, do we need to do the same thing when we're talking about, uh, uh, construction material? Are we just putting dry layer upon dry layer of concrete to like cinder [00:13:00] blocks, or does it all become one solid glob of.

[00:13:05] Sarbajit Banerjee: Right. So there you're hitting upon several important points, right? So the one hand you want it to be a little bit like toothpaste, with the consistency of toothpaste, you want it to have some flow properties, right? So that you can extrude it through a nozzle or you can, or through some sort of, uh, um, some sort of form.

Um, into, in, and, and pattern it onto a surface, onto a substrate, right? So it's gotta have those flow properties. But then, um, and if, you know, if you don't have the flow properties, uh, you know, the history of treaty printing is, is, uh, full of clo nozzles. That's pretty much the bane of everybody that does 3D printing.

Uh, but. The next step though, um, is it can't be toothpaste light for too long, because then you can't put the next layer on, right? So ideally you'd like to, to have your next layer come on, and, and the, the layer that you had put down before hold its weight, hold its form. [00:14:00] Um, now there's different things you could do.

You could have each layer fus into each other. Or you could have the entire structure somehow, uh, become a singular monolith. Um, so, so depending on the type of structural engineering you wanna do, um, and, and the type of materials you have available now getting the entire structure diffuse into one singular monolith is incredibly difficult.

But it would be quite interesting if you could, if you could achieve it. And 

[00:14:26] Gus Herwitz: what, what are we starting to see in terms of developments for, uh, uh, 3D printed construction materials and structure? 

[00:14:37] Sarbajit Banerjee: Right. So there's a, a huge amount of 3D printing of concrete going. Right. And we're seeing, um, uh, there's a company in, uh, Austin, Texas.

Icon has been doing some great work. Uh, there's a, there's a Russian company, APSCo, that's been doing some great work. There's been some amazing structures in Mexico, in Dubai. Um, We're seeing two ends of it. I would say [00:15:00] on the one hand we are seeing some very high end, uh, very avant garde architecture coming out online.

On the other hand, we're seeing, um, you know, I guess what people call dignified habitats. You know, maybe sing little houses that you can build for some of the more, um, populations that are in need of, of, of housing. So there's, I would say, two ends of the market that have that, that seem to be, uh, coming online, but there's a lot of construction with concrete.

And I, I think one, one of the thoughts that my group has, is if 3D printing takes off and all we do is make it easier to print with concrete and to, and we end up expanding the use of concrete, that's going to become a whole catastrophe in itself in terms of. Environmental 

[00:15:51] Gus Herwitz: in. Yeah. Yeah. So we've got two different trends, uh, working at loggerheads here.

The, the concern that concrete has a very high environmental impact, but [00:16:00] these, uh, new 3D printing technologies are making it easier to do more things at lower cost, uh, with concrete. Um, uh, but before we, uh, turn to, uh, the work that your group is doing to resolve that, What are the, the limitations or uh, advantages of 3D printed buildings?

[00:16:23] Sarbajit Banerjee: Uh, Sure. So, you know, when you, when you do, when you 3D print buildings, you can be very, uh, much in sync with the local environment. I think that's the biggest opportunity as I see it, You're, you can decrease the amount of material that is needed. Right. And there's some. Incredible demonstrations from companies like Autodesk, Um, uh, and, and even beyond the construction industry space in terms of 3D printed metal structures and such, where, you know, maybe 10, 15% of, um, the weight of a material, uh, is enough to give you the same load bearing [00:17:00] properties as as a large chunk.

So, um, now I think there's some real exciting opportunities that opens up too, if you're. That little material, you can use interesting new materials. You can, you can have, you can, um, add in interesting new function. Um, you can customize structures to the needs of the inhabitants, um, to the needs of, of that geography.

So, uh, you know, build in, um, all kinds of modes of resilience towards, you know, flooding toward. Earthquakes, Um, and, and how you design those architectures. So it just opens up a lot of, lot 

[00:17:38] Gus Herwitz: of opportunities. Yeah. So, uh, to give an example, uh, counterintuitive, I expect to most listeners, um, most listeners would probably expect that a solid rod, let's say just a a one inch diameter solid rod of steel would be stronger than a cylinder.

With the same diameter of steel, like a, a straw. Um, but it, it turns out in many [00:18:00] cases that the hollow tube, uh, will be stronger, less prone to bending more, uh, uh, vibration resistant, all, all sorts of different characteristics than the, uh, solid rod. And it uses significantly less material. So lighter, lower, cost, stronger.

This kind of seems like a win-win, win, um, all around. Um, and, and, uh, just to make sure, uh, I'm understanding you, you gave the examples of that we're seeing really avant guard structures being built, but also really basic structures and that really captures both ends of the spectrum here. With a 3D printing, you're not limited to static forms.

You're not limited to pouring concrete into a shell. You can print whatever shape you want, uh, or you have much more flexibility. So if you want to have a building that is shaped like a, a pineapple or a pair, I'm just coming up with shapes, people will be familiar with. It's relatively straightforward. It would be a lot [00:19:00] harder to build that out of steel or pour that in forms or build that in wood.

And on the, uh, other end, if you need to print a thousand single, uh, room, uh, uh, households in quick order, you can do that much more quickly with these technologies, with less material in principle than using, uh, traditional, uh, uh, concrete and construction, uh, techniques. Um, that it does that all. Am I right about what I just 

[00:19:28] Sarbajit Banerjee: said?

Yeah, that's absolutely right. Yeah, that's, that's exactly right. So there's just. A tremendous amount of opportunities. Uh, and because you're decreasing the amount of material required, um, you, you can do all, uh, many different interesting things. You can in use different materials and you can customize it to whatever is the needs of the inhabitants are.

Whatever the needs of the climate are. Okay. 

[00:19:51] Gus Herwitz: Well, uh, now that we've laid the foundation, we're going to take a, a brief break and we will be back in a moment, uh, to, uh, talk [00:20:00] about what is really the exciting work here, uh, that, uh, you've been doing, uh, in this area. So listeners, uh, uh, stick with us.

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[00:20:56] Gus Herwitz: So we are back, uh, with Sarbajit Banerjee talking [00:21:00] about 3D printing of, uh, buildings and, uh, other structures. And we've been talking generally about, uh, these technologies, uh, focusing primarily on what we could do with. Concrete. But uh, as we started our conversation with concrete ain't all that. It's got some problems with it.

Um, uh, so, uh, , you and your team have been doing work, uh, with alternatives to concrete. Uh, can you tell us a bit about, uh, generally, uh, what your work is? 

[00:21:31] Sarbajit Banerjee: Sure. Yeah. So we've got a team here of, uh, architects, um, civil engineers and chemists and material scientists looking to see if we could come up with a, uh, toolkit of, um, a toolkit of chemistries that, so that we could, we could harvest local soils.

No matter where you are in the world and, and build from that and, uh, and 3D print architectures from that. So how do you, uh, how do you sort of, uh, [00:22:00] solidify, um, the local soils into, into something that is a 3D printable formulation? And, uh, of course, you know, local soils have long been used in construction.

Um, uh, if you, you've got these adobe houses, you've got, um, traditional mud buildings across the world. Um, they are, they have many advantages. They're, you know, uh, that they're sort of very suit typically tend to be very, um, uh, Optimized to their local climates. And so, um, can we take that a, a step further and, and use local soils and thereby mitigate, uh, the need to, you know, um, generate concrete and to transport it to a site, um, and to just sort of build using that material.

And if you're building, using that material, Um, that there's also a, a huge play there in terms of dismantling the structure at the end of life [00:23:00] and then being able to return those materials to the back of the 

[00:23:02] Gus Herwitz: year. So what are some of the challenges here? Um, I, I assume that we're not just talking, taking the soil, adding water, and letting it dry out.

Um, why, why, why doesn't that alone work? And what, what are some of the challenges you've had to. , Right? 

[00:23:19] Sarbajit Banerjee: So the challenges is, is how do you, uh, and there are challenges to just to use the soil as a construction material, and then there's additional challenges that's 3D printing in. Right. So, uh, to, to generate, to use soil as a, as a construction material, it's, it's a question of how do you, So soil's got this diverse range of different, different materials in it.

It's got different, different sorts of play, uh, organic matter. How do you get this stuff to form a cohesive matrix? And, and this is where we've been, been trying to come up with cross-linking chemistries that, that you can, you can pour in and allow. Some sort of skeletal framework to be built up around [00:24:00] which you can, um, solidify the components of the soil and, and then, um, that gives you the original framework and then you can sort of add in more cross links and get something that is, that is pretty strong.

So approaching the compressive strengths, typical of high performance concrete is a tall order give with this sort of, uh, rag tag, mix of this spread materials. And, and, and that's been, uh, a big challenge in itself. And then when it comes to actually using it in 2D printing, then we've got the sync challenges that we do for concrete.

How do you come up with a slurry, uh, um, some sort of formulation that can be either extruded or uh, um, some. Deposited to a nozzle, um, in a, in a manner, uh, that it, you know, is, is sort of viscous liquidity when you're depositing it and it solidifies relatively fast to hold the weight of the next layer and the whole its own weights, that it [00:25:00] defines the sort of structures that you.

Set 

[00:25:02] Gus Herwitz: up to me. So when you say, uh, cross-linking chemistries, that, that sounds like it's the glue that holds this entire idea together, are these like long molecules that will get stuck together and form like a lattice and then the, the soils just kind of get stuck in there and they're, they're kind of like what fills the holes, uh, in that lattice?

[00:25:22] Sarbajit Banerjee: Yeah, that's a really good, good description of it. You can sort of think about, uh, having these internet mul, uh, molecular chains that start holding it together, uh, these polymeric polymeric chains. And, and we oftentimes will incorporate multiple, multiple different modes of cross-linking, so multiple different modes in which it can come together.

Um, uh, to, and, and then yeah, entrenching, uh, en meshing the soil particles and promoting sometimes some specific reactions in there as well that get the soil particles to that, that, for instance, people will react to clear particles and, and inform specific, uh, uh, structures. For instance, we've [00:26:00] been playing around and trying to get.

Something called eing guide, which is a particular type of, uh, relatively fast forming, um, solid needles to form that then will also reinforce the structure, uh, 

[00:26:15] Gus Herwitz: looking at the, uh, uh, technologies and takes techniques that you're using right now. Uh, how is this comparing to concrete? 

[00:26:24] Sarbajit Banerjee: Concrete, uh, some incredibly impressive structural properties, so we, we aren't still there.

Now also, uh, another thing to keep in mind when you're thinking about building out large structures, there's a lot of. Codes that we've developed over the last multiple decades that really are just, uh, written for concrete. So we're gonna have to reta those codes entirely when, when, when time comes, we, we think about alternative materials.

So, um, I think the first set of uses we're gonna see are in, um, items like architectural [00:27:00] facades and such, rather than the actual weight bearing, you know, parts of building, uh, and on relatively smaller structure. So everything where you don't have to meet every possible sort of metric that concrete needs, but, uh, you, you can, you can work through with, um, uh, relatively sort of lower end, um, strengths.

Okay. Um, and, and then the, uh, the other, the other challenge, right, that, uh, which is concrete is really good, uh, at mixing with steel re. And that's something that, again, there's a lot of work going on and how do we incorporate steel rebar with locally sourced materials? With sort of clays and such, how do we, how do we come up with a, um, version of reinforced concrete that doesn't actually use concrete?

Um, and, and, and I think that, uh, and it doesn't have to be steel rebar. Uh, of course, using, [00:28:00] um, these, these, uh, new types of soils means we could use all kinds of plant fibers and carbon fibers as uh, v r equivalents. Um, but, but there's a whole sort of, Field that is now emerging, that is looking at these fiber reinforcement as, uh, as sort of mimicking reinforced concrete.

But that's that, that needs to happen if you're really going to reach out to the high strengths of reinforced concrete structures that you see really large buildings and such made out of. 

[00:28:32] Gus Herwitz: So I, I need to briefly put on my law professor hat and make a note for any law students listening or maybe even law faculty out there.

Sounds like there's a great law review topic, uh, in here. Updating building codes for a post concrete era. Um, uh, a lot of interesting challenges immediately come to mind there. So, uh, uh, foreign listeners who are law students who are working on lar view notes, uh, there's a contribution, uh, from this podcast for you, Um, [00:29:00] uh, on the topic of, uh, steel reinforcement or reinforced non concrete, um, I'll, I'll just ask this in the, the simple naive way.

Why can't we just stick steel rebar, uh, in the, uh, uh, uh, soil based materials that you're working with? 

[00:29:19] Sarbajit Banerjee: Oh, we, we absolutely can. Um, and, and it, and it works. Um, the challenge is how do you treat and print the rebar as well as the soil around it. Right. And, and there, there is work going on in, um, for example, a DEHA, and we've been playing around a little bit with it too, is, is how could you, you know, the whole idea of, uh, putting rebar down, could you, could you blend this into the treaty printing process where you're cutting rebar and, and applying, uh, you know, your locally sourced materials exactly around it.

And, uh, building out these structures. So, [00:30:00] An active field of research. Um, there's all sorts of interesting steels that are coming into play. We've, uh, we've done a couple of recent articles. Uh, China has had, you know, tremendous success with some, uh, ultra high strength, um, you know, rebars and, and this is, uh, there's even, uh, a few buildings that have been built out in Europe and Switzerland using ultra high strength rebars.

And, and what this means is that you end up using less and less. You can, you can, uh, you need far fewer columns and such if you're, if you're gonna use VBar that has, um, you know, strengths of 600, 700 mega Pascal. Um, and this is achieved by micro alling. Typically an elements such as vanadium gets put into steel and, um, it's, it's a tremendous carbon saving as well.

And so we, we've got a recent article that shows that China achieved, uh, it's an interesting story. You know, the Sichuan earthquake happened and, um, you know, [00:31:00] one of the things that happened after Sichuan Earthquake is that there were a lot of public buildings that fell. Um, especially the, the earthquake happened around lunchtime, so school buildings were damaged. 

The, the very large number of casualties among school going children. So, uh, the, um, Chinese artist I V V has these, uh, installations that he built. The broken rebar and, uh, what, what people found is just the poor quality of rebars that didn't have the seismic resilience made a huge, uh, uh, impact.

And as China started tightening standards for rebar, They ended up using higher and higher strength rebar. Uh, but the, uh, unintentional consequence has been huge carbon savings. Uh, almost 1% of, uh, China's entire CO2 production got saved because, By moving to high strength rebar, they use so much less steel.

And I [00:32:00] think that's the way to go. Um, at least in the short term for these 3D printed structures, once we start incorporating rebar in there, is to use advanced high strength steels. They also have a lot more flexibility, um, and, and the sorts of structural properties that would allow for you not to lose the forms that you want to make with when you're, when you're using.

Native soils. Um, and, uh, there's not a 3D printed structure that is particularly impressive, but the, uh, there's a Roche building in, in Switzerland that is built out of these advanced high strengths deal rebars. That is, I think, a really good illustration for what's 

[00:32:39] Gus Herwitz: possible. Mm-hmm. , uh, there, there's so much in there, and.

I love the, just the, the basic framing of both this discussion and your research. Um, minimizing the environmental impacts of concrete, finding different alternatives to concrete and doing this innovative, uh, construction. Uh, and as much as it pains me to say, uh, [00:33:00] China has been doing incredible things in this area, driven largely by their construction boom.

Uh, ju just in the news over the last couple of days, um, uh, Chinese steel product. Is currently almost at a standstill. Um, but a large part of that is due to a lack of energy. And China is deploying massive amounts of solar energy because, uh, it's become cheaper for them to do so than relying on coal. So, uh, uh, greening their, uh, energy production ecosystem environment in order to.

More steel, which we need for, to reinforce all of this. And it's going to make it, uh, much lower impact from a carbon perspective. It, it's fascinating. Um, Which I guess, uh, we can use to turn to, uh, a more general question. Uh, what, what are the benefits of, uh, these approaches to construction over a more traditional, uh, approaches to construction?

[00:33:59] Sarbajit Banerjee: So [00:34:00] we end up using a lot less material. You, uh, uh, can build out forms. You know, allow for, you know, optimal crosscurrents of wind and, and allow for sound to be directed in specific ways. Um, you can, um, you're of course mitigating the. The disastrous impact of concrete. Right. Um, and then, uh, you know, I think then there's a whole set of new benefits that you get at the end of life when you can dispose of these materials readily, um, and, and not have to worry about their environmental impact.

So using soils has a, has a lot of, uh, You know, uh, benefits if you can do it. And, um, you know, there's also, uh, we've done a little bit of this in the past. We were building roads out in the subar where it wasn't easy to get conventional reinforcing elements, so we started using wood fibers, right? So it's not nowhere near the function of [00:35:00] steel just yet, but.

Um, there's a, a, a pathway there, there's a blueprint there for starting to think about how, you know, uh, cell, those could, could be used as reinforcing components and thereby really go to very sustainable architectures. So 

[00:35:16] Gus Herwitz: I, I have never thought, uh, This will allow us to print buildings in ways that, uh, uh, reduce noise pollution effectively and things like that.

That's just, uh, I'm seeing here, that's blowing my mind. Um, uh, I have to ask, uh, you say that, uh, reduced environmental impacts, uh, uh, we can return these soils to their native uses or reuse them for construction. Um, how, how do we know that the chemicals that you're using as binding agents aren't going to be harmful to the environment?

[00:35:52] Sarbajit Banerjee: Yeah, it's a really good question. So we, you know, and this is, we've stuck. Uh, chemistries that are typical of soil, so [00:36:00] silicon and aluminum as such. And, and, and to give you a little bit of history, uh, we started doing this work, if you've ever seen the show, Ice Road Truckers. Uh, and, and part of this, the premise of the show.

It's not one of my favorite shows, uh, is, is that people drive on packed Ds in the winter, um, in, you know, in the subar parts of the country. Uh, trying to, because that's the only time where you, you, it's safe to drive, right? Um, otherwise the soil is too marshy. Um, and, and stuff will sink. And so we set out to build all weather roads in those climates.

And, uh, one of the things, uh, of course is that most of those lands are publicly owned. And we had this shore, uh, environment Canada, that we had a way to return the, the environment to its pristine. Within 40 years, because that's all they do is, is 30, 40 year leases of the land with the companies that operate in, you know, drilling infrastructure and touch [00:37:00] there.

And so we had to actually make, uh, compacted roads and, and show that we could take it apart and that when we tested the water, when we tested the groundwater, uh, and such that there were no contaminants, we were abusing into this. This entire process had to be vetted into that. So it's definitely possible.

So we've shown that it can be done, and uh, part of this is deliberate design, right from the inception to make sure that the, the, uh, what you call the glue, right, the binding chemistries that hold it together. Um, have elements that are commonly found in nature. We're not using, um, anything that would be toxic or, and such.

And what 

[00:37:42] Gus Herwitz: about the cost? Um, more expensive. Less expensive than concrete Today. And whe when do you think we'll be at a point where, uh, cost comes down to, uh, the point where we're seeing widespread use of these technologies? 

[00:37:58] Sarbajit Banerjee: Yeah, that's a really good point. I mean, so cost is, [00:38:00] is, um, something that, So nothing.

In the chemistries we've developed is particularly expensive. Now, when you've got a well-oiled supply chain like concrete does, where people have shaved every bit of, you know, cost down, it, it's, it's a hard material to compete against. And this is, this is true for any entrenched technology that it's produced at scale and has all the advantages of pricing at scale.

Um, so, so, At this point of time, it's not cost competitive to be doing the sorts of chemistries we're doing, but there's nothing intrinsically, uh, expensive about the chemistries when, when at scale they're certainly competitive with, with concrete, especially if you start putting some real carbon, uh, assessments in terms of what that cost is.

[00:38:51] Gus Herwitz: Do you, who, who do you expect the first users, uh, at any scale of this app? Uh, these technologies. 

[00:38:59] Sarbajit Banerjee: Um, I [00:39:00] think the two ends you're seeing absolutely right. So lots of interest in, in places like Dubai to build, uh, one of a kind intricate structures that ha have. Amazing functionality that has never been seen before in a building.

And then, um, there's also tremendous push to, uh, deliver dignified habitats that are smaller scale, low footprint in, in regions where it can be, can be really, really difficult. And, uh, you know, the, the other thing that I think where, um, we're really finding a lot of res. Is places where you simply cannot build the concrete, you know, And, and so these are not places that are cost constrained.

These are places that are material or accessibility constrained. And one of the points, uh, being like up in the subar, this ice road truckers region, you just can't log concrete there. So you have to build with native soil an extremely challeng. Native soil. So marshy, [00:40:00] muskeg soil is what it's called. And so, uh, the other, other, uh, we've been working with nasa.

We have a NIAC proposal, uh, that has been NAK award. Um, in the naac study is focused on building with reg lit on marsh using martian soil or lunar soil. But we are not gonna be able to take concrete with us. Up in the space? 

[00:40:21] Gus Herwitz: Uh, can, can you tell us a any more about that? That's just, you're, you're talking about space now, so this just got really cool.

[00:40:30] Sarbajit Banerjee: Yes, absolutely. I mean, this is something that we've been, uh, we've been simulating, we've been having a lot of fun with this. Um, uh, we've got, uh, uh, ideas for delivering, uh, capsules that will react with the local soils, those, uh, LUNs lunar soil and martian soils, and essentially, uh, adhere them together into, uh, into.

You know, fused pads and we've shown that they can be quite strong. We can drive SUVs over [00:41:00] them, and, and they can withstand extremely low temperatures. It's, well, extremely high temperatures with the rockets landing. Um, the first thing we're trying to build, um, our project is called, uh, Rams. So Regal it adaptive modification systems.

Uh, the first thing we're trying to build is, is landing paths for repeated lunar landings and repeated marsh landings. So if you're gonna build this sy lunar economy, we're gonna have. Have a safe, uh, haven for, um, all our space ships to be landing. So how do we exploit that local soil to, you know, how do we extract metals from it, um, to come up with, to build steel on, on, on, on, in space, and, um, especially to build high performance steel, to build high performance aerospace alloys and to fuse the, the regal that particles together.

To build these, these slab that are weight bearing and convincing, large temperature fluctuation. 

[00:41:55] Gus Herwitz: Um, it, it just dawned on me, I've been assuming that you [00:42:00] use water in the production, uh, here. Uh, when we start talking about space, obviously water is possibly the most precious commodity, even more precious than oxygen in many ways.

Um, do you, do we need water, uh, for these applic. 

[00:42:16] Sarbajit Banerjee: So you're right on, on earth. We do use water, but you don't have to have water. Uh, for these chemistries, we've had to modify them to be, um, to use very little or no water at all. And, and we, we've used a little bit of, um, for instance, um, a. Um, Lysol and, and, and polymers, um, to, to replace water, um, and, and perform some of the same functions.

We have other alternatives that are really based on making very metallic structures that, so, um, they're really cool because you can, you know, we've been playing around. Having these, uh, explosive reactions happen. Uh, they're, you know, termite reactions and, and so it's a, [00:43:00] it's an entirely different way of building and, uh, we do it out in the open and makes for a huge, uh, quite a spectacle.

And, uh, you know, the fire department comes out and watches us. It's all very safe. Mm-hmm. . Um, but, but it's, uh, it's, it's, it's a lot of fun to do it without water too. And it's, it's a different chemistry. But we can do it, um, through either termite chemistry or to what we call non hydrolytic chemistry.

Mm-hmm. . 

[00:43:22] Gus Herwitz: Well, I, I'm not at all a fan of gender reveal parties, but I love the idea of a house reveal party where your, your house, you get all of your friends together and you like the thermite reaction and all these fireworks go off and. Voila, you have a house, uh, that comes outta the process. , um, uh, any, I I just love this work so much.

Um, and, uh, it, we discussed earlier, the thing that I think really hits, uh, why it is so important, uh, productivity in construction. It's been a very static field for so long. Um, This sort of work, this sort [00:44:00] of engineering really has the potential, I think to dramatically change, uh, the economies of scale at which we can create, uh, structures of all, all types, but especially, uh, uh, affordable, high quality residential units, which is, uh, obviously so important.

Um, uh, any last thoughts before we wrap up? 

[00:44:23] Sarbajit Banerjee: Yeah, I think there's, uh, interesting interface with society, uh, for the future of society, right? Um, and as automation takes over, as uh, construction industry sort of gets, uh, an overhaul, what happens to even the future of work, right? Um, and you've got such a large version of the world's population involved with this and, and if the construction industry looks very different 20 years down the.

Then those jobs are gonna look a lot different and perhaps will be fewer. And so I think there's some, some issues there, but some quandaries there that, uh, need, um, you know, different, different [00:45:00] disciplines, um, lawyers and scientists and, and social scientists to work together to figure out what the answers will be for, uh, If you're gonna have this disruptive change happen, the construction 

[00:45:11] Gus Herwitz: and, and that brings together just such a wonderful juxtaposition, I, I now have in my mind this image of houses being built by autonomous ai, robot droids out of dirt.

It's ultra high-tech, futuristic. And it's the stuff that the earth is made of that we walk on it. It's wonderful. Um, well thank you, uh, uh, so much for, uh, taking the time and sharing your work with us. Uh, listeners interested in learning more will, uh, definitely post, uh, some materials that you can take a look at.

Uh, we've been speaking with Cyber eight Ban Energy from Texas a and m about, uh, his work on using soils to, uh, 3D print, uh, buildings and other forms of cons. And I've been your host, Gus Herwitz. Thank you listeners for joining us on this episode of Tech Refactored. If you want to learn more about what we're [00:46:00] doing here at the Nebraska Governance and Technology Center, or submit an idea for a future episode, you can go to our website ngtc.unl.edu, or you can follow us on Twitter at UNL underscore ngtc.

If you enjoyed the show, please don't forget to leave us a rating and a review wherever you listen to your podcast. Our show is produced by Elsbeth Magilton and Lysandra Marquez and Colin McCarthy created and recorded our theme music. Our research associate Neil Rutledge, provided topic and substantive development for this episode.

This podcast is part of the Menard Governance and Technology Programming Series. Until next time, keep your nozzles clean.