Speaker 1: Welcome to tex Stuff, a production from my Heart Radio.
Speaker 1: Pay there and welcome to tech Stuff. I'm your host,
Speaker 1: Jonathan Strickland. I'm ad executive producer with I Heart Radio,
Speaker 1: and I love all things tech. And today's episode is
Speaker 1: going to focus on something that relates to climate change.
Speaker 1: You know, it was Earth Day not too long ago,
Speaker 1: and while I did not have an episode specifically for
Speaker 1: Earth Day, I thought it would be good to create
Speaker 1: something within that spirit. And recently I was perusing Scientific
Speaker 1: American like I do, and I saw an article by
Speaker 1: Benjamin star Ow titled X Prize Winners use c O
Speaker 1: two emissions to make concrete and We're gonna get to that,
Speaker 1: and Starrow made some excellent points. I highly recommend the article.
Speaker 1: But that article made me think, I should you an
Speaker 1: episode about concrete. We depend very heavily upon concrete. It
Speaker 1: is the most frequently used material around the world for
Speaker 1: the purposes of, you know, building stuff. It's the literal
Speaker 1: foundation for many of the structures we build. And the
Speaker 1: production and transportation of concrete represents a truly enormous source
Speaker 1: of carbon emissions, which of course are major contributors to
Speaker 1: climate change. And so I thought I would dedicate an
Speaker 1: episode to concrete. Now, you could argue it's not high
Speaker 1: tech stuff. Most of the time, concrete doesn't have you know,
Speaker 1: cool circuitry or artificial intelligence or anything like that, although
Speaker 1: we will talk about the technology that does use some
Speaker 1: of that stuff. However, concrete represents a technological advance, and
Speaker 1: there are some interesting technologies, like the ones that use
Speaker 1: CEO two to help actually make concrete, that we can
Speaker 1: talk about. But first let's talk about what concrete is.
Speaker 1: It is a material that is made up of aggregate,
Speaker 1: that is particulate material that ranges from medium grade down
Speaker 1: to course. So think of stuff like sand or gravel,
Speaker 1: or pebbles or crushed stone. These are loose, small, individual
Speaker 1: pieces of hard material. Now, obviously you can't just build
Speaker 1: with aggregate all by itself. You would end up with
Speaker 1: piles of particulate. You'd have sand dunes or or piles
Speaker 1: of gravel, which is not terribly useful. So another part
Speaker 1: of concrete is a binding agent. This is essentially a glue.
Speaker 1: It holds the particulate together and we go from having
Speaker 1: a pile of sand or gravel to concrete once we
Speaker 1: mix it with this binding agent, which gives that that
Speaker 1: material strength, and the result is something that's akin to
Speaker 1: an artificial stone, but it's one that when it's still
Speaker 1: in its viscous form, you can actually shape the stuff.
Speaker 1: Then it will harden and will hold that shape. So
Speaker 1: rather than having to look for a stone that's just
Speaker 1: the right shape, or having to employ a stonemason to
Speaker 1: cut an existing stone down to the correct shape, you
Speaker 1: could just, in theory, make one yourself out of concrete.
Speaker 1: Another important aspect of concrete is that it's chemically inert.
Speaker 1: It is not reactive to stuff, so it's very stable.
Speaker 1: You don't have to worry about concrete getting wet and
Speaker 1: then going all droopy. Though with concrete, water does actually
Speaker 1: make a difference, but we'll get to that, because water
Speaker 1: is all part of the system. Now. Depending upon your
Speaker 1: point of view, you might argue that the binding agent
Speaker 1: for concrete has to be cement in order of you
Speaker 1: to consider the finished product actual concrete, otherwise it's something else. However,
Speaker 1: other people are a little more loosey goosey with a
Speaker 1: definitive terms, and they will use concrete to refer to
Speaker 1: materials that relied on other binding agents to hold together, particulate,
Speaker 1: or sometimes they might give a little ground, and and
Speaker 1: they'll call such stuff a sort of a predecessor to concrete.
Speaker 1: The discovery of cement probably dates back thousands of years
Speaker 1: when early people's observed something interesting with regard to their
Speaker 1: cooking fires. So people would dig a hole and into
Speaker 1: that hole they would, you know, build their their cooking fires.
Speaker 1: And those high temperatures from the fires would cause the
Speaker 1: edges of the hole to kind of dry and crack
Speaker 1: and sometimes even turn into a bit of a powder.
Speaker 1: And when it would rain, water mixing with that powder
Speaker 1: would sometimes become a sludge that would then harden into
Speaker 1: a stone like material. Now, one source I looked at
Speaker 1: for this episode was a paper titled Concrete History and
Speaker 1: Stories from World Scientific Now, according to that source, these
Speaker 1: ancient peoples used a protoconcrete to start construction on the
Speaker 1: famed hour of Babel, you know, the one that in
Speaker 1: the Bible was began construction and then God said, hey, guys,
Speaker 1: I don't dig how you're building up to the heavens,
Speaker 1: so I'm going to give you all different languages and
Speaker 1: scatter you so that you can't taught to each other anymore.
Speaker 1: But according to this paper, uh, what was happening was
Speaker 1: that the builders kind of ran out of raw material
Speaker 1: before they could finish construction, and then they just sort
Speaker 1: of abandoned the project. Now, several ancient civilizations used different
Speaker 1: aggregates and binding materials in an effort to create artificial stones.
Speaker 1: The Assyrians and the Babylonians used clay and bitumen. And
Speaker 1: you might not be familiar with bitumen um, And in fact,
Speaker 1: I don't even know if I'm pronouncing it correctly. I
Speaker 1: should have looked that up before this episode, but hey,
Speaker 1: let's wing it anyway. It's a petroleum based type of hydrocarbon,
Speaker 1: so it's a If you were to break down its
Speaker 1: chemical composition, you would say it's a compound of hydrogen
Speaker 1: and carbon, which is pretty common. In fact, that's the
Speaker 1: reason why a hydrogen based economy is harder than what
Speaker 1: it sounds like. Hydrogen is almost always bound to something else,
Speaker 1: and frequently it's carbon. Anyway, it's extremely viscous and it's
Speaker 1: really dense stuff, and it can be found in pitch
Speaker 1: lakes and oil sands out there in nature. So in
Speaker 1: some parts of the United States, it's referred to as asphalt.
Speaker 1: Though the asphalt we used to pave roads is made
Speaker 1: up of other stuff in addition to a binder made
Speaker 1: from bitamin or a bitumin like substance. Meanwhile, the Egyptians
Speaker 1: and the Phoenicians were using gypsum and lime. Gypsum is
Speaker 1: made of calcium sulfate dihydrate, and it's a big ingredient
Speaker 1: and lots of stuff including drywall, chalk, fertilizer, and modern cement.
Speaker 1: Lime the material, not the fruit, so you don't you
Speaker 1: don't put this in a coconut and drink them both up.
Speaker 1: In this case, we're talking about an inorganic mineral made
Speaker 1: of calcium and various oxides. The Greeks also use lime,
Speaker 1: and they treated it in kilns to create burnt lime.
Speaker 1: Like kilns are an important element of creating cement. You
Speaker 1: couldn't just use this material as it was, you know,
Speaker 1: found in nature. You had to treat it to heat
Speaker 1: in order to have the chemical transition into what would
Speaker 1: become concrete or cement. Rather, we'll talk more about processing
Speaker 1: lime in a bit, because that does play a huge
Speaker 1: part in the production of cement. In fact, many early
Speaker 1: civilizations would use kilns similar to or in some cases
Speaker 1: exactly the same as the kilns that they would use
Speaker 1: to fire pottery. The kilns would reach the temperatures needed
Speaker 1: to quote unquote burn the lime, making it suitable to
Speaker 1: use as a binding agent. Most of these early forms
Speaker 1: of protoconcrete would cure in the air. They hardened upon
Speaker 1: exposure to the air, or, as spinn Thalo put it
Speaker 1: in an article in nineteen sixty seven, quote lime that
Speaker 1: needs air to achieve strength end quote. I like that phrasing.
Speaker 1: Then came the Romans. And while the Romans stole a
Speaker 1: ton of stuff from the Greeks, they also innovated quite
Speaker 1: a lot of stuff themselves, and one of those things
Speaker 1: they innovated was concrete. Now, the Greeks had been using
Speaker 1: concrete a little bit, but not anywhere to the extent
Speaker 1: that the Romans did. And the Romans discovered natural cements
Speaker 1: called Pozzolan's. Actually, I should say that Pezzolan's might have
Speaker 1: already been in use pre Roman times, but the Romans
Speaker 1: really went ham on the stuff. Mm hmm, ham and pozzolan.
Speaker 1: So what the heck is pozolan? Well, according to the
Speaker 1: American Concrete Institute, it is quote a solicitous and aluminous
Speaker 1: material that in itself possesses little or no simentitious value,
Speaker 1: but will in finally divided form, and in the present
Speaker 1: some moisture chemically react with calcium hydroxide at ordinary temperatures
Speaker 1: to form compounds having sementitious properties. End quote. That is
Speaker 1: a mouthful, but in plain English it means that it's
Speaker 1: a material that when ground up into a powder and
Speaker 1: mixed with water and material that contains calcium hydroxide, it
Speaker 1: becomes cement. Like that is, it can bind aggregate as
Speaker 1: cement and form concrete. Actually, I should point out in
Speaker 1: fact I Probace should have done this already. Cement and
Speaker 1: concrete are not the same thing. They are not synonymous.
Speaker 1: Cement is to concrete what flour is to a cake. Right.
Speaker 1: It's an ingredient, it's an important part, but it is
Speaker 1: not the same thing anyway. The source for the Romans
Speaker 1: was a puzzolonic ash, which in itself came from volcanic
Speaker 1: ash and pumice. So the Romans would collect this ash
Speaker 1: and they would use it with calcium hydroxide to create
Speaker 1: their cement. When did they start doing this, well, we're
Speaker 1: not really sure. It wouldn't have been any later than
Speaker 1: one fifty before Common era or B C. As there's
Speaker 1: evidence of concrete structures dating from around that time period,
Speaker 1: so it was definitely at least as late as that.
Speaker 1: It was probably earlier, much earlier. But there's just no
Speaker 1: Roman record that says, quote, it's to seventy four b C.
Speaker 1: And we just invented concrete. Also, why are our years
Speaker 1: counting down backward? Anyway? I'm off to the vomitorium end quote.
Speaker 1: And yeah, I made at least two dumb jokes based
Speaker 1: off inaccurate representations of ancient Rome's timekeeping in terminology, but
Speaker 1: I couldn't resist. Concrete would play an enormous part in
Speaker 1: the Roman architectural revolution. In fact, it was such a
Speaker 1: crucial component of that movement that we sometimes referred to
Speaker 1: it as the concrete Revolution. This marked a period in
Speaker 1: Roman history of huge architectural projects, including the famous Roman Pantheon,
Speaker 1: on which was has a dome made from concrete that,
Speaker 1: from its shape, supports itself with no need for additional
Speaker 1: columns or other supports apart from the walls, which kind
Speaker 1: of act like columns. The Romans could build enormous structures
Speaker 1: thanks to concrete, which could be poured and then cured. Well,
Speaker 1: it's the quote process of controlling the rate and extent
Speaker 1: of moisture loss from concrete during cement hydration end quote.
Speaker 1: That's the helpful definition from cement, Concrete and Aggregates Australia.
Speaker 1: So let's dive into that a little bit further. Hydration
Speaker 1: is the mixing of water with cement and aggregate that
Speaker 1: gets this whole binding process going. And I realized this
Speaker 1: is skipping over the modern method of producing cement, but
Speaker 1: we will get back to that a bit later. Right now,
Speaker 1: we're talking about Roman concrete, which uses a natural cement
Speaker 1: with fewer controls, and that meant consistency was a little variable. Okay,
Speaker 1: So you make the concrete by mixing together water, cement,
Speaker 1: and the aggregate, which forms a workable paste. You put
Speaker 1: this where you want it to go, such as in
Speaker 1: a form mold. So imagine that you've got like a
Speaker 1: wooden box that doesn't have a top and the sides
Speaker 1: and bottom are all removable, So you put it together.
Speaker 1: Then you pour the paste into that box so it
Speaker 1: takes on the shape of the box. Then you remove
Speaker 1: the wood once it's all done. But the once you're
Speaker 1: done bit is important. So the Roman concrete, like modern concrete,
Speaker 1: required hydration. That is, the cement needed moisture to harden further.
Speaker 1: Once dried out, concrete is set, and generally speaking, the
Speaker 1: faster it dries out, the weaker it is. Don't get
Speaker 1: me wrong, it's still strong stuff and it can withstand
Speaker 1: incredible compressive forces, that is, forces that push down on it,
Speaker 1: you know, in an attempt to compress it. But it
Speaker 1: can also be a little brittle, and if the concrete
Speaker 1: remains wet, the reactions within cement will tenue and sometimes
Speaker 1: for years if it remains moist before drying out. It's
Speaker 1: this process of hardening that is called curing. It's not
Speaker 1: the drying out part, it's the hardening part that's that's
Speaker 1: kind of the the end process is dried out. It's
Speaker 1: the keeping it wet in order to get the hardness
Speaker 1: and strength you want. That's important. Um and in fact
Speaker 1: concrete part of that mass is made up of water. Chemically,
Speaker 1: what's going on is calcium silicates are undergoing an exothermic reaction.
Speaker 1: As they interact with water, they release hydroxide ions, calcium ions,
Speaker 1: and heat. The bit about releasing heat is what makes
Speaker 1: this an exothermic reaction. Eventually, calcium and hydroxide ions saturate
Speaker 1: the system and they begin to form calcium hydroxide crystals. Meanwhile,
Speaker 1: calcium silicate hydrate forms. The crystalline structures provide seed points
Speaker 1: for further ions to kind of glom onto, and the
Speaker 1: process can grow from there. But it does need water
Speaker 1: to continue this reaction, and as those crystals form, the
Speaker 1: concrete gets harder and stronger. Controlling this reaction falls to
Speaker 1: the rate at which water molecules can diffuse through the
Speaker 1: calcium silicate coating. As the reaction progresses, that coding gets
Speaker 1: thicker and it gets more difficult for water to make
Speaker 1: its way through, which in turn means the reaction begins
Speaker 1: to slow down. Hydration will continue as long as water
Speaker 1: can get into the system and as long as there
Speaker 1: remains unhydrated compounds within the paste. This process can go
Speaker 1: on for days or weeks, or months or even years.
Speaker 1: I'll be there for you when the rain starts to fall.
Speaker 1: As long as water can permeate an access unhydrated cement,
Speaker 1: the process will continue. Also, while the reactions release heat,
Speaker 1: this process itself goes through an interesting revolution. Early on
Speaker 1: in the hydration process, the reactive mixture will release a
Speaker 1: good amount of heat, the temperature will will go up
Speaker 1: several degrees, but after the first now fifteen minutes to
Speaker 1: half an hour of the reaction, that temperature starts to drop.
Speaker 1: Then a few hours in the amount of heat it
Speaker 1: releases will begin to climb again, and over several hours
Speaker 1: it will peak, and once you get like twenty hours in,
Speaker 1: it will then begin to slowly drop the temperature again,
Speaker 1: very slowly ramping down. And what's happening is that the
Speaker 1: rate of the reactions themselves changes as things initiate and
Speaker 1: then water it continues to react with the cement mixture.
Speaker 1: Then it gradually becomes more difficult for water to make
Speaker 1: its way to unhydrated elements of the cement, so the
Speaker 1: curing process can be done without having to heat anything
Speaker 1: else up, and in fact it itself heats up. As
Speaker 1: we'll learn a bit later, that's kind of the opposite
Speaker 1: of the actual modern process of making cement. So concrete
Speaker 1: formation is exothermic, but the production of cement turns out
Speaker 1: to be endo thermic. I'll explain more later on this episode.
Speaker 1: Now we've got some more to say about the process
Speaker 1: of concrete forming, and we'll talk a lot more about
Speaker 1: cement in just a moment. But first let's take a
Speaker 1: quick break. Now. I mentioned that if concrete dries out quickly,
Speaker 1: it won't be as strong as concrete that was hydrated properly.
Speaker 1: But let's get a bit more detailed with that, because
Speaker 1: it's not as simple as just you know, drenching wet
Speaker 1: cement mix as you wait for it to cure. The
Speaker 1: amount of water you add makes a difference. The ratio
Speaker 1: of water to cement is important. A low water to
Speaker 1: cement ratio means you're gonna end up with concrete that's
Speaker 1: very strong, but it's also very difficult to work. So,
Speaker 1: in other words, the paste will be extremely viscous and
Speaker 1: you might end up with shapes you totally didn't intend
Speaker 1: and now you're stuck with them unless you, you know,
Speaker 1: grab some heavy duty tools. High water to cement ratio
Speaker 1: means you're gonna have a paste that's really workable, but
Speaker 1: the over all strength of the concrete will be low.
Speaker 1: So it's not just how long the cement is kept moist,
Speaker 1: but how much water you use to do it. In
Speaker 1: our modern era, there are other things we can add
Speaker 1: to cement and aggregate to improve stuff like workability, and
Speaker 1: plasticity and strength. But let's get back to the Romans,
Speaker 1: because we've got to get back to them, because they're
Speaker 1: always Roman around. It's a dad joke. The Romans learned
Speaker 1: about the hydration process and produced a lot of concrete,
Speaker 1: at least for the time anyway, They relied on the
Speaker 1: natural cement features of volcanic ash. Many of those structures
Speaker 1: exist in whole or in part today, which is really
Speaker 1: just a testament to the strength and durability of concrete.
Speaker 1: But there was a pretty long span of time between
Speaker 1: the fall of the Roman Empire and the widespread use
Speaker 1: of concrete and other civilizations outside of some uses in
Speaker 1: building in churches and cathedrals, And it may be that
Speaker 1: the knowledge of producing concrete was largely kept in religious
Speaker 1: scents as far back as the earliest examples of the stuff,
Speaker 1: which gave the edge to the clerical folks out there
Speaker 1: over everybody else. So the Roman Empire trips on a
Speaker 1: bananappeal and falls and Europe plunges into the Dark Ages
Speaker 1: kind of. I mean, the history of the Dark Ages
Speaker 1: is actually really complicated, but for our purposes, the secrets
Speaker 1: to cement and concrete are largely lost until the fifteenth
Speaker 1: century when the rediscovery of an old manuscript written by
Speaker 1: Marcus vitruvious Polio, usually just called Vitruvius, rekindled interest. Now,
Speaker 1: Vitruvius was an architect and engineer way back in the
Speaker 1: first century b c. He wrote a long manuscript about
Speaker 1: the principles of architecture, and it included a section on
Speaker 1: the production of Roman concrete. So as the Renaissance began
Speaker 1: to bloom in Europe, there was a new interest in concrete.
Speaker 1: In fact, Giovanni Giocondo used Roman concrete to build a
Speaker 1: part of the bridge called the Pont the Notre Dame
Speaker 1: in Paris in fourteen nine, which, as I understand it
Speaker 1: is widely thought of as the first example of the
Speaker 1: modern use of concrete, and it was also necessary. The
Speaker 1: Pont Notre Dame sometimes gets called the most ancient of
Speaker 1: bridges in Paris, but this is largely a matter of
Speaker 1: point of view, because it hasn't always been the same bridge.
Speaker 1: The Pont Neuf is the oldest bridge that remains in
Speaker 1: its original form in Paris, but there has been a
Speaker 1: bridge at the location of Polt Notre Dame. The longest. However,
Speaker 1: that Pont Notre Dame Bridge has gone through multiple collapses
Speaker 1: and demolitions and otherwise has been destroyed numerous times, only
Speaker 1: to have been rebuilt. So this is a real ship
Speaker 1: of theseus kind of thing we've got going on here anyway.
Speaker 1: Giacondo used a recipe of Roman concrete as part of
Speaker 1: the rebuilding process after the bridge suffered a collapse in
Speaker 1: fourteen ninety nine when the way of houses on the
Speaker 1: bridge proved to be too much for the old structure.
Speaker 1: This version of the bridge, the concrete one, stood largely
Speaker 1: unaltered until eighteen fifty three, So that was back in
Speaker 1: four but widespread use really wouldn't kick into high gear
Speaker 1: for a few more centuries. In seventeen seventy four, an
Speaker 1: English engineer by the name John Smeaton learned that by
Speaker 1: using quicklime as an ingredient for making cement, he could
Speaker 1: make better, harder cement, and later in seventeen ninety three
Speaker 1: he discovered something else which brings us to calcination. Calcination
Speaker 1: is the process of heating up a solid to a
Speaker 1: very high temperature, and the purposes to burn off any
Speaker 1: volatile substances within that solid mass so that you're left
Speaker 1: with a more pure lump of whatever it was you
Speaker 1: started off with. Smeaton discovered that calcinating limestone that had
Speaker 1: clay content in it would produce hydraulic lime. As the
Speaker 1: name implies, this produces a lime that hardens underwater. Three
Speaker 1: years later, an Englishman named James Parker patented a hydraulic
Speaker 1: cement produced by calcinating limestone that contained clay. Engineers began
Speaker 1: building lime kilns, essentially ovens dedicated to calcinating limestone. So
Speaker 1: they were trying to recreate the effect that those ancient
Speaker 1: peoples saw around their their fires, their food fires, years
Speaker 1: and years and years centuries earlier. Now let's skip ahead
Speaker 1: to eighteen twenty four. A builder named Joseph Asten found
Speaker 1: that by grinding up chalk and putting it in a
Speaker 1: kiln with clay produced an even stronger type of cement.
Speaker 1: This is the type of cement we call Portland cement.
Speaker 1: It's named after the Isle of Portland in the English Channel.
Speaker 1: It's where a type of limestone called Portland stone comes from,
Speaker 1: and that stone played a huge part in British architecture.
Speaker 1: Fact it still does. More people made contributions towards the
Speaker 1: understanding and production of cement. But the next innovation I
Speaker 1: want to talk about came courtesy of Frederick Ransom. Ransom
Speaker 1: wanted to find a way to consistently make the best cement,
Speaker 1: which required a new type of kiln. So the old
Speaker 1: cement kilns were essentially vertically aligned ovens. So think of
Speaker 1: like a chimney. You would load this stuff up with
Speaker 1: limestone and clay, You would have fuel at the bottom.
Speaker 1: You get the kiln up to a certain temperature, and
Speaker 1: you would kind of mix everything together, and in between
Speaker 1: loads you might even allow the oven to go cool,
Speaker 1: which represented a pretty darn big waste of energy because
Speaker 1: it takes a lot of fuel to get kilns up
Speaker 1: to temperature, and once you get it up there, it
Speaker 1: takes less fuel for you to just keep it there
Speaker 1: than it would if you let it go cold and
Speaker 1: had to start it up again. And by high to pachures,
Speaker 1: we're talking up around four dred degrees celsius and hotter.
Speaker 1: The result of this process is that the limestone and
Speaker 1: the clay partially melt together into nodules that are called clinker.
Speaker 1: The clinker, once cooled, can be crushed into a powder
Speaker 1: mixed with gypsum, and then you've got your cement. A
Speaker 1: lot of stuff actually happens in this process, but I'm
Speaker 1: going to explain more in just a moment, so stick
Speaker 1: with me. Ransom figured out that one way you can
Speaker 1: make a better kiln is to go from this vertically aligned,
Speaker 1: you know, smokestack style kiln to a tilted one, one
Speaker 1: that was almost closer to horizontal than vertical, but still
Speaker 1: on an incline. So the raised end, the part that's
Speaker 1: higher up, would be where you would feed limestone and
Speaker 1: clay into the kiln. On the opposite end, the lower end,
Speaker 1: you would have an opening at the base where clinker
Speaker 1: could pass through, and that's also where you would have
Speaker 1: your heat source that would get the raw materials up
Speaker 1: to the right melting point, and the whole thing would rotate,
Speaker 1: shifting material around and causing it to gradually move down
Speaker 1: the length of the kiln. It was a rotating kiln,
Speaker 1: so you would feed in your mix of limestone and
Speaker 1: clay at the top and at that end of the kiln,
Speaker 1: far from the heat source, you would have the relatively
Speaker 1: chilly temperatures of between seventy two degrees celsius. At this temperature,
Speaker 1: any water content in the feed would evaporate off. This
Speaker 1: is also the end where any gas is given off
Speaker 1: by the process would escape. The raw material would then
Speaker 1: sift down further into the kiln as the kiln rotated,
Speaker 1: and it would start to reach hotter segments. So once
Speaker 1: the material reached between four hundred to six hundred degrees celsius,
Speaker 1: the clay would start to decompose into oxides like silicon
Speaker 1: dioxide and aluminum oxide, and the limestone would decompose into
Speaker 1: calcium carbonate, magnesium oxide, and some carbon dioxide. So some
Speaker 1: of that carbon dioxide would then expel out the end
Speaker 1: of the kiln, but we would continue our journey down
Speaker 1: the kiln, and now the raw materials are reaching around
Speaker 1: six hundred and nine hundred celsius somewhere in that range,
Speaker 1: and the calcium carbonate from the limestone would react with
Speaker 1: the silicon dioxide to form a material called the light
Speaker 1: or B E L I T E, also known as
Speaker 1: die calcium silicate. So this again continues to sift down
Speaker 1: the length of this rotating kiln, and of course it
Speaker 1: gets even hotter as it gets closer to the source
Speaker 1: of heat, and around nine hundred two thousand, fifty degrees celsius.
Speaker 1: Any remaining calcium carbonate decomposes into calcium oxide and more
Speaker 1: carbon dioxide, which again exhausts out the end of the kiln.
Speaker 1: Then the material gets towards the point where the hottest
Speaker 1: section is with temperature is getting up to around four
Speaker 1: hundred fifty degrees celsius, and the raw material begins to
Speaker 1: melt and fuse into clinker, which sifts down through and
Speaker 1: opening at the base of the kiln and falls into
Speaker 1: a cooling tank. Modern rotating kilns recapture the heat from
Speaker 1: the clinker and they use that as part of the
Speaker 1: way to power the system. So if you follow that process,
Speaker 1: you realize a few really big things. First, the chemical
Speaker 1: process to create Portland's cement is an endothermic reaction, meaning
Speaker 1: you actually have to add heat to make this reaction happen.
Speaker 1: And we contrast to that to the two concrete curing
Speaker 1: that's an exothermic reaction. It gives off heat. You also
Speaker 1: probably heard there are a couple of steps there that
Speaker 1: involve a release of carbon dot oxide in this chemical process.
Speaker 1: That's one of the big byproducts of cement production carbon dioxide.
Speaker 1: But it doesn't stop there. We also have to consider
Speaker 1: the whole system, not just what gets produced through this
Speaker 1: chemical reaction. So to power the kilns, I mean to
Speaker 1: make the heat, we need fuel and that tends to
Speaker 1: be fossil fuels, and burning fossil fuels also produces carbon
Speaker 1: dioxide emissions. So cement production contributes a significant amount of
Speaker 1: CEO two emissions, both in the chemical process itself of
Speaker 1: cement becoming cement and also the fossil fuels that you
Speaker 1: need to burn in order to create the heat to
Speaker 1: get this reaction going. In fact, global cement production accounts
Speaker 1: for about five percent of all CEO two emissions, which
Speaker 1: is a staggering amount for one specific process. And when
Speaker 1: you factor into the equation other considerations, like the fact
Speaker 1: you still have to transport the cement to wherever it's
Speaker 1: going to be used, you start to see how our
Speaker 1: dependence upon cement and concrete becomes challenging. Now, let's get
Speaker 1: some stuff straight. Concrete is incredibly useful and and important.
Speaker 1: I mean, without concrete, there'd be no way to build
Speaker 1: stable structures beyond a few stories, which would mean that
Speaker 1: we would have to sprawl out even more than we
Speaker 1: already do. And I should also add that the fact
Speaker 1: we can build really tall structures like skyscrapers isn't just
Speaker 1: due to concrete. You see, concrete does have incredible compressive strength,
Speaker 1: that is, it can hold a ton of weight literally
Speaker 1: can hold a ton of weight, tons and tons of weight,
Speaker 1: but doesn't have great tensile strength. If you build a
Speaker 1: very tall structure and you only use concrete, you're asking
Speaker 1: for trouble because something like really high winds or an
Speaker 1: earthquake could cause monumental damage and even total collapse. But
Speaker 1: fortunately we have a lot of people to thank for
Speaker 1: creating more resilient ways to use concrete. One of those
Speaker 1: people was a nineteenth century gardener in France named Joseph Monnier.
Speaker 1: He wanted to create a more durable flower pot. Then
Speaker 1: he began to experiment with concrete set around an iron
Speaker 1: mesh frame. He created iron reinforced concrete or ferro concrete.
Speaker 1: A lot of other people would build literally upon that idea,
Speaker 1: giving us stuff like the lovely rebar that gives more
Speaker 1: tensile strength to concrete. So concrete is really handy stuff.
Speaker 1: It's one of the big innovations that has supported urbanization
Speaker 1: and industrialization. So it is not easy to say we
Speaker 1: should give up on concrete due to carbon emissions. However,
Speaker 1: at the same time, humans are producing a lot of cement.
Speaker 1: In twenty the estimated global production was around four point
Speaker 1: one billion tons of the stuff, and every ton of
Speaker 1: cement creates nine ms of c O two emissions, which
Speaker 1: is around one four pounds of carbon dioxide per ton
Speaker 1: of cement. So that would mean in cement production dumped
Speaker 1: around three point seven trillion ms or eight trillion pounds
Speaker 1: of c O two into the atmosphere. And again that's
Speaker 1: just figuring in the production of cement, not the transportation
Speaker 1: or anything like that. And keep in mind might have
Speaker 1: actually seen more cement production than we did had there
Speaker 1: not been a pandemic. The four point one billion tons
Speaker 1: figure has remained fairly consistent since around but back in
Speaker 1: the industry actually produced an estimated four point two billion tons,
Speaker 1: so we're not likely to see this number go down
Speaker 1: anytime soon. And there are other parts of concrete production
Speaker 1: that contribute to CEO two emissions, it's just that the
Speaker 1: manufacturing of cement represents by far the largest contributor. All Right,
Speaker 1: So we know that making concrete creates a lot of
Speaker 1: carbon dioxide. We also know concrete is really important stuff,
Speaker 1: and that it's not as easy as just walking away
Speaker 1: from the material. When we come back, i'll talk about
Speaker 1: those researchers who pumped c O two into concrete mix
Speaker 1: and what that all actually means. But first let's take
Speaker 1: a quick break. In two Matt made, the then governor
Speaker 1: of the U. S State of Wyoming, issued a challenge.
Speaker 1: It was a competition to find ways to convert carbon
Speaker 1: dioxide emissions into sellable products. So, in other words, ways
Speaker 1: to take something that is generally a negative, that is
Speaker 1: the release of carbon dioxide, and to turn it into
Speaker 1: a positive. Now, presumably the goal wasn't just to create
Speaker 1: a product, but to lock c O two into some
Speaker 1: other substance so that it wouldn't be part of the atmosphere. Now.
Speaker 1: Me did this for a few different reasons. One big
Speaker 1: one is that Wyoming has a coal industry. But obviously
Speaker 1: coal is a fossil fuel, and burning coal releases c
Speaker 1: O two, So the optics are not great for the
Speaker 1: coal industry, and it's hard to get around this fact
Speaker 1: that this particular industry contributes to climate change, and that
Speaker 1: in turn poses a pretty big threat to our way
Speaker 1: of life, which is perhaps the most understated way I
Speaker 1: could have put that. So finding a way to capture
Speaker 1: c O two and convert it into something else and
Speaker 1: to make it a profitable endeavor would be a great solution.
Speaker 1: One of the reasons carbon capture initiatives aren't exactly proliferating
Speaker 1: all over the place is that they tend to be expensive,
Speaker 1: and often the output isn't something you can monetize. So
Speaker 1: it's not that we don't know how to capture carbon dioxide.
Speaker 1: We've got lots of ways to do it. It's just
Speaker 1: that we don't have a lot of ways to do
Speaker 1: it that in turn generate revenue. They represent a cost.
Speaker 1: So if you're literally pumping CEO two underground so that
Speaker 1: it's essentially captured down beneath the ground, and you know
Speaker 1: you're not making any money off that CEO two it's
Speaker 1: just pumped down there, it's actually gonna cost you money
Speaker 1: to move the CEO two down there. And businesses, by
Speaker 1: and large, from what I understand, exists to make revenue.
Speaker 1: So generally speaking, businesses don't tend to follow pathways that
Speaker 1: two expenses if they can avoid it, and carbon capture
Speaker 1: is expensive. But if you can create a product, Well,
Speaker 1: then you can recapture those costs, and if the product
Speaker 1: is good enough, as in popular enough and desirable enough,
Speaker 1: you can actually make a profit off of it. And
Speaker 1: now with a profitable plan for carbon capture, you can
Speaker 1: kick things into a different gear. Now, what is environmentally
Speaker 1: beneficial is also economically beneficial, at least in the short term.
Speaker 1: And let me do a quick aside here. I want
Speaker 1: to stress wholeheartedly that climate change mitigation is in fact
Speaker 1: economically beneficial. It's just on a much longer timetable than
Speaker 1: most businesses focus on. Businesses tend to look at fiscal
Speaker 1: quarters or maybe a fiscal year, and mitigating climate change
Speaker 1: on that kind of time scale doesn't seem to make
Speaker 1: economic sense because of the expenses involved, and you're not
Speaker 1: likely to see any kind of you know, results immediately.
Speaker 1: But when you pull back and you take a much
Speaker 1: longer term view, you see the climate change stands as
Speaker 1: a threat to entire regions and industries, and you realize
Speaker 1: that climate change mitigation is the best economic strategy in
Speaker 1: the long term. It's just really hard to get stakeholders
Speaker 1: to look that far out, as we tend to be
Speaker 1: pretty short sighted when it comes to stuff like money
Speaker 1: and lots of other things too. All right, let's get
Speaker 1: back to this X Prize competition thing. Out of the
Speaker 1: competition emerged a couple of teams with proposals for a
Speaker 1: green concrete strategy, and both teams had shown that by
Speaker 1: injecting carbon dioxide into the concrete production process, they can
Speaker 1: both reduce the amount of CEO two that was released
Speaker 1: and they can make concrete stronger. One team, called Carbon
Speaker 1: Cure Technologies injected c O two into concrete wastewater, which
Speaker 1: didn't turn it into some sort of carbonated beverage, but
Speaker 1: rather created a mineral that, when added back into the
Speaker 1: concrete mixture, made it stronger. The second team, you see
Speaker 1: l a carbon Built, injected c O two into concrete
Speaker 1: as it goes through the curing process. This approach reduced
Speaker 1: the amount of carbon dioxide emissions from producing that concrete.
Speaker 1: By now, that's just the production of that concrete, not
Speaker 1: the cement that was used to make that concrete. Keeping
Speaker 1: in mind that cement production is the real issue here.
Speaker 1: The reduction in greenhouse gas from concrete production might seem
Speaker 1: like a band aid on top of a very serious cut.
Speaker 1: It's not nearly good enough. It's a reduction that is good,
Speaker 1: but it's not eliminating the vast amounts of c O
Speaker 1: two given off through cement production. The process does require
Speaker 1: CEO two. That means that you could create carbon capture
Speaker 1: systems and pair them with facilities like a cement production facility,
Speaker 1: so the CEO two generated from cement production would go
Speaker 1: toward making better concrete. But honestly, these facilities produce way
Speaker 1: more carbon dioxide than you would need to produce green
Speaker 1: concrete solutions. You would really need to build in capture
Speaker 1: and sequestration facilities into cement production plants. But like I
Speaker 1: said earlier, those solutions are expensive and they represent an
Speaker 1: economic cost to the companies. It's possible for governments to
Speaker 1: create incentives to reward companies for capturing and sequestering carbon,
Speaker 1: but outside of that it's a tough sell, and even
Speaker 1: the political approach is super difficult because there are a
Speaker 1: lot of politicians who aren't exactly swayed by the science
Speaker 1: of climate change. Meanwhile, there are engineers looking to find
Speaker 1: ways to reduce the amount of carbon emissions released during
Speaker 1: cement production, largely by fiddling with the formula. A big
Speaker 1: source of the problem is that the materials in the
Speaker 1: process of make cement have to be heated up to
Speaker 1: around fifty degrees celsius or hotter to form clinker. Finding
Speaker 1: alternatives to those materials that can react at lower temperatures
Speaker 1: would release the amount of fossil fuels that you needed
Speaker 1: for the process. Another solution is to look at byproducts
Speaker 1: generated from other industries like fly ash and use those
Speaker 1: as additives to reduce the amount of cement production that
Speaker 1: you need in order to make concrete. So, in other words,
Speaker 1: if you are using fly ash to make up some
Speaker 1: of the weight of the cement, you don't need as
Speaker 1: much cement to make concrete, and as long as the
Speaker 1: finished product is as good or better than existing concrete,
Speaker 1: your golden Now. I also didn't really cover this, but
Speaker 1: with the hydraulic nature of concrete the need for hydration,
Speaker 1: there's also a big need for water. In fact, the
Speaker 1: concrete industry takes up nearly ten of industrial water use
Speaker 1: and nearly one point seven percent of total global water use.
Speaker 1: So not only is it dumping CEO two in the atmosphere,
Speaker 1: it's using up a significant amount of water and in
Speaker 1: some areas of the world that might not be a
Speaker 1: huge deal. But for other areas that are affected by
Speaker 1: water shortages and droughts and have a need to lay
Speaker 1: a lot of concrete to build up their their infrastructure,
Speaker 1: that's a huge problem. Water resources are precious, I mean,
Speaker 1: wars are fought over them, and an industry as thirsty
Speaker 1: as concrete production adds more pressure. One thing I wanted
Speaker 1: to close on was a cool technology that uses cement
Speaker 1: products similar to concrete as an ink in a three
Speaker 1: D printing application. These companies are using enormous three D
Speaker 1: printers to print buildings, and there are actually a few
Speaker 1: different companies doing this. One of them is called icon
Speaker 1: Icon has a large industrial three D printer called the
Speaker 1: Vulcan two, which uses a cement based building material which
Speaker 1: the company calls lava crete as the ink. So with
Speaker 1: the Vulcan Too, it's possible to print out a single
Speaker 1: story building. The Vulcan too can print walls that stand
Speaker 1: at a maximum of eight and a half feet tall,
Speaker 1: and the printer is thirty three ft wide and can
Speaker 1: print on a foundation that's up to twenty eight feet wide. However,
Speaker 1: the Vulcan can also move down the length of a
Speaker 1: structure as it builds it and there's no real maximum
Speaker 1: length that you would have, like you could in theory
Speaker 1: build it as long as you wanted it to be.
Speaker 1: It would always be at max. Twenty eight feet wide,
Speaker 1: but it could be as long as you needed, assuming
Speaker 1: you had the materials and the land, like the level
Speaker 1: space to build upon. The printer pushes out the mixture
Speaker 1: at a rate of around five to seven inches of
Speaker 1: wall length per second, which yeah, that's really fast. So
Speaker 1: by laying down lines of this lava creet each line
Speaker 1: is about an inch tall, then you can lay out
Speaker 1: the outline of your wall structure, and then you start
Speaker 1: putting on the second layer. Each layer binds with one
Speaker 1: underneath it, and so then the volcantuo can print a building,
Speaker 1: or at least the walls, you know, the internal and
Speaker 1: external walls of a building. You would still have to
Speaker 1: provide the finishing touches, you know, stuff like doors and
Speaker 1: and a roof and ceiling and that kind of thing.
Speaker 1: But this mixture has the special binding agents in it
Speaker 1: so that they do hold together. And using that approach,
Speaker 1: it's possible to build a house out of a concrete
Speaker 1: like material within a day or two, depending on the
Speaker 1: size of the building. The rapid approach to building durable
Speaker 1: homes could be a huge game changer and help communities
Speaker 1: address problems like homelessness or creating housing in the wake
Speaker 1: of a natural disaster. It's the plasticity of the liquid
Speaker 1: form of the material that makes it really possible to
Speaker 1: go through a three D printer device, and the curing
Speaker 1: process makes it a practical structural material. And I have
Speaker 1: to emit these are really interesting technologies that could serve
Speaker 1: as a huge benefit if put to the right use.
Speaker 1: That's a big if. However, it requires people to spearhead
Speaker 1: projects that aim for these goals, and of course that
Speaker 1: does not change the fact that cement production is still
Speaker 1: an environmentally costly process. We shouldn't forget that while cement
Speaker 1: production is a big contributor to greenhouse gas emissions, it
Speaker 1: is also not the largest contributor. Transportation tends to be
Speaker 1: the biggest one, followed by electricity production. And so while
Speaker 1: it's important that we address issues with carbon emissions from
Speaker 1: cement and concrete production, we can't focus solely on that issue.
Speaker 1: If we quote unquote solved it, we would still have
Speaker 1: a lot of work to do. So if we just
Speaker 1: look at one thing, that ends up creating a false
Speaker 1: sense of achievement whenever we make any sort of progress,
Speaker 1: and meanwhile, we continue to dump tons of CEO two
Speaker 1: into the atmosphere. The quest to create green concrete and
Speaker 1: cement has to be part of our approach to climate
Speaker 1: change mitigation, but it can't be the only part of it. Well,
Speaker 1: that wraps up this episode of text Stuff and our
Speaker 1: look at concrete. There's obviously a lot more we could say.
Speaker 1: I didn't really go into the various additives that have
Speaker 1: been developed over the years to change the the the
Speaker 1: qualities of concrete, but that would require a much deeper
Speaker 1: dive into chemistry. And y'all know, when I started getting
Speaker 1: lots of letters and numbers together, my eyes begin to
Speaker 1: glaze over. So we're gonna leave it here for now.
Speaker 1: But if you have suggestions for future topics of tech stuff,
Speaker 1: reach out to me. The best way is over on Twitter.
Speaker 1: The handle for the show is text Stuff HSW and
Speaker 1: I'll talk to you again really suit. Text Stuff is
Speaker 1: an I Heart Radio production. For more podcasts from my
Speaker 1: Heart Radio, this at the i Heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows. H