1 00:00:04,400 --> 00:00:07,800 Speaker 1: Welcome to tex Stuff, a production from my Heart Radio. 2 00:00:12,200 --> 00:00:15,400 Speaker 1: Pay there and welcome to tech Stuff. I'm your host, 3 00:00:15,600 --> 00:00:19,040 Speaker 1: Jonathan Strickland. I'm ad executive producer with I Heart Radio, 4 00:00:19,120 --> 00:00:23,880 Speaker 1: and I love all things tech. And today's episode is 5 00:00:23,920 --> 00:00:28,120 Speaker 1: going to focus on something that relates to climate change. 6 00:00:28,160 --> 00:00:30,319 Speaker 1: You know, it was Earth Day not too long ago, 7 00:00:31,120 --> 00:00:34,360 Speaker 1: and while I did not have an episode specifically for 8 00:00:34,479 --> 00:00:37,240 Speaker 1: Earth Day, I thought it would be good to create 9 00:00:37,320 --> 00:00:42,159 Speaker 1: something within that spirit. And recently I was perusing Scientific 10 00:00:42,240 --> 00:00:45,800 Speaker 1: American like I do, and I saw an article by 11 00:00:45,880 --> 00:00:50,040 Speaker 1: Benjamin star Ow titled X Prize Winners use c O 12 00:00:50,159 --> 00:00:53,920 Speaker 1: two emissions to make concrete and We're gonna get to that, 13 00:00:54,280 --> 00:00:57,800 Speaker 1: and Starrow made some excellent points. I highly recommend the article. 14 00:00:58,280 --> 00:01:00,319 Speaker 1: But that article made me think, I should you an 15 00:01:00,320 --> 00:01:05,360 Speaker 1: episode about concrete. We depend very heavily upon concrete. It 16 00:01:05,480 --> 00:01:10,480 Speaker 1: is the most frequently used material around the world for 17 00:01:10,520 --> 00:01:13,920 Speaker 1: the purposes of, you know, building stuff. It's the literal 18 00:01:14,080 --> 00:01:17,679 Speaker 1: foundation for many of the structures we build. And the 19 00:01:17,720 --> 00:01:22,319 Speaker 1: production and transportation of concrete represents a truly enormous source 20 00:01:22,400 --> 00:01:26,080 Speaker 1: of carbon emissions, which of course are major contributors to 21 00:01:26,120 --> 00:01:29,080 Speaker 1: climate change. And so I thought I would dedicate an 22 00:01:29,080 --> 00:01:33,000 Speaker 1: episode to concrete. Now, you could argue it's not high 23 00:01:33,080 --> 00:01:36,280 Speaker 1: tech stuff. Most of the time, concrete doesn't have you know, 24 00:01:36,760 --> 00:01:41,000 Speaker 1: cool circuitry or artificial intelligence or anything like that, although 25 00:01:41,040 --> 00:01:43,480 Speaker 1: we will talk about the technology that does use some 26 00:01:43,560 --> 00:01:47,560 Speaker 1: of that stuff. However, concrete represents a technological advance, and 27 00:01:47,600 --> 00:01:50,440 Speaker 1: there are some interesting technologies, like the ones that use 28 00:01:50,600 --> 00:01:54,280 Speaker 1: CEO two to help actually make concrete, that we can 29 00:01:54,320 --> 00:01:58,360 Speaker 1: talk about. But first let's talk about what concrete is. 30 00:01:59,120 --> 00:02:02,440 Speaker 1: It is a material that is made up of aggregate, 31 00:02:02,920 --> 00:02:06,920 Speaker 1: that is particulate material that ranges from medium grade down 32 00:02:06,960 --> 00:02:11,360 Speaker 1: to course. So think of stuff like sand or gravel, 33 00:02:11,639 --> 00:02:16,919 Speaker 1: or pebbles or crushed stone. These are loose, small, individual 34 00:02:16,960 --> 00:02:21,239 Speaker 1: pieces of hard material. Now, obviously you can't just build 35 00:02:21,280 --> 00:02:23,840 Speaker 1: with aggregate all by itself. You would end up with 36 00:02:23,919 --> 00:02:28,280 Speaker 1: piles of particulate. You'd have sand dunes or or piles 37 00:02:28,280 --> 00:02:31,280 Speaker 1: of gravel, which is not terribly useful. So another part 38 00:02:31,320 --> 00:02:35,840 Speaker 1: of concrete is a binding agent. This is essentially a glue. 39 00:02:36,000 --> 00:02:39,280 Speaker 1: It holds the particulate together and we go from having 40 00:02:39,280 --> 00:02:42,639 Speaker 1: a pile of sand or gravel to concrete once we 41 00:02:42,840 --> 00:02:47,120 Speaker 1: mix it with this binding agent, which gives that that 42 00:02:47,160 --> 00:02:50,519 Speaker 1: material strength, and the result is something that's akin to 43 00:02:50,639 --> 00:02:54,320 Speaker 1: an artificial stone, but it's one that when it's still 44 00:02:54,360 --> 00:02:57,840 Speaker 1: in its viscous form, you can actually shape the stuff. 45 00:02:58,240 --> 00:03:01,400 Speaker 1: Then it will harden and will hold that shape. So 46 00:03:01,480 --> 00:03:03,760 Speaker 1: rather than having to look for a stone that's just 47 00:03:03,919 --> 00:03:07,080 Speaker 1: the right shape, or having to employ a stonemason to 48 00:03:07,240 --> 00:03:10,800 Speaker 1: cut an existing stone down to the correct shape, you 49 00:03:10,840 --> 00:03:14,239 Speaker 1: could just, in theory, make one yourself out of concrete. 50 00:03:14,600 --> 00:03:18,440 Speaker 1: Another important aspect of concrete is that it's chemically inert. 51 00:03:18,919 --> 00:03:22,880 Speaker 1: It is not reactive to stuff, so it's very stable. 52 00:03:23,120 --> 00:03:25,480 Speaker 1: You don't have to worry about concrete getting wet and 53 00:03:25,480 --> 00:03:30,320 Speaker 1: then going all droopy. Though with concrete, water does actually 54 00:03:30,400 --> 00:03:32,560 Speaker 1: make a difference, but we'll get to that, because water 55 00:03:32,680 --> 00:03:36,040 Speaker 1: is all part of the system. Now. Depending upon your 56 00:03:36,040 --> 00:03:39,320 Speaker 1: point of view, you might argue that the binding agent 57 00:03:39,920 --> 00:03:43,520 Speaker 1: for concrete has to be cement in order of you 58 00:03:43,640 --> 00:03:50,160 Speaker 1: to consider the finished product actual concrete, otherwise it's something else. However, 59 00:03:50,240 --> 00:03:52,640 Speaker 1: other people are a little more loosey goosey with a 60 00:03:53,000 --> 00:03:56,840 Speaker 1: definitive terms, and they will use concrete to refer to 61 00:03:56,880 --> 00:04:01,160 Speaker 1: materials that relied on other binding agents to hold together, particulate, 62 00:04:01,560 --> 00:04:04,120 Speaker 1: or sometimes they might give a little ground, and and 63 00:04:04,160 --> 00:04:07,520 Speaker 1: they'll call such stuff a sort of a predecessor to concrete. 64 00:04:07,960 --> 00:04:12,960 Speaker 1: The discovery of cement probably dates back thousands of years 65 00:04:13,320 --> 00:04:17,839 Speaker 1: when early people's observed something interesting with regard to their 66 00:04:17,920 --> 00:04:22,120 Speaker 1: cooking fires. So people would dig a hole and into 67 00:04:22,160 --> 00:04:26,400 Speaker 1: that hole they would, you know, build their their cooking fires. 68 00:04:27,000 --> 00:04:30,840 Speaker 1: And those high temperatures from the fires would cause the 69 00:04:31,000 --> 00:04:33,719 Speaker 1: edges of the hole to kind of dry and crack 70 00:04:33,839 --> 00:04:36,360 Speaker 1: and sometimes even turn into a bit of a powder. 71 00:04:36,400 --> 00:04:39,440 Speaker 1: And when it would rain, water mixing with that powder 72 00:04:39,640 --> 00:04:42,880 Speaker 1: would sometimes become a sludge that would then harden into 73 00:04:42,960 --> 00:04:46,480 Speaker 1: a stone like material. Now, one source I looked at 74 00:04:46,520 --> 00:04:50,320 Speaker 1: for this episode was a paper titled Concrete History and 75 00:04:50,480 --> 00:04:54,960 Speaker 1: Stories from World Scientific Now, according to that source, these 76 00:04:55,000 --> 00:04:59,279 Speaker 1: ancient peoples used a protoconcrete to start construction on the 77 00:04:59,400 --> 00:05:02,599 Speaker 1: famed hour of Babel, you know, the one that in 78 00:05:02,640 --> 00:05:08,239 Speaker 1: the Bible was began construction and then God said, hey, guys, 79 00:05:08,680 --> 00:05:11,880 Speaker 1: I don't dig how you're building up to the heavens, 80 00:05:11,920 --> 00:05:14,200 Speaker 1: so I'm going to give you all different languages and 81 00:05:14,240 --> 00:05:17,120 Speaker 1: scatter you so that you can't taught to each other anymore. 82 00:05:17,360 --> 00:05:20,680 Speaker 1: But according to this paper, uh, what was happening was 83 00:05:20,720 --> 00:05:23,160 Speaker 1: that the builders kind of ran out of raw material 84 00:05:23,240 --> 00:05:26,120 Speaker 1: before they could finish construction, and then they just sort 85 00:05:26,160 --> 00:05:31,560 Speaker 1: of abandoned the project. Now, several ancient civilizations used different 86 00:05:31,560 --> 00:05:35,599 Speaker 1: aggregates and binding materials in an effort to create artificial stones. 87 00:05:36,160 --> 00:05:40,719 Speaker 1: The Assyrians and the Babylonians used clay and bitumen. And 88 00:05:40,800 --> 00:05:43,920 Speaker 1: you might not be familiar with bitumen um, And in fact, 89 00:05:43,960 --> 00:05:45,880 Speaker 1: I don't even know if I'm pronouncing it correctly. I 90 00:05:45,880 --> 00:05:48,160 Speaker 1: should have looked that up before this episode, but hey, 91 00:05:48,400 --> 00:05:52,480 Speaker 1: let's wing it anyway. It's a petroleum based type of hydrocarbon, 92 00:05:52,680 --> 00:05:54,920 Speaker 1: so it's a If you were to break down its 93 00:05:54,960 --> 00:05:58,039 Speaker 1: chemical composition, you would say it's a compound of hydrogen 94 00:05:58,120 --> 00:06:02,000 Speaker 1: and carbon, which is pretty common. In fact, that's the 95 00:06:02,080 --> 00:06:05,800 Speaker 1: reason why a hydrogen based economy is harder than what 96 00:06:05,880 --> 00:06:09,520 Speaker 1: it sounds like. Hydrogen is almost always bound to something else, 97 00:06:09,920 --> 00:06:15,040 Speaker 1: and frequently it's carbon. Anyway, it's extremely viscous and it's 98 00:06:15,120 --> 00:06:18,120 Speaker 1: really dense stuff, and it can be found in pitch 99 00:06:18,279 --> 00:06:22,320 Speaker 1: lakes and oil sands out there in nature. So in 100 00:06:22,360 --> 00:06:25,360 Speaker 1: some parts of the United States, it's referred to as asphalt. 101 00:06:25,680 --> 00:06:28,520 Speaker 1: Though the asphalt we used to pave roads is made 102 00:06:28,600 --> 00:06:31,520 Speaker 1: up of other stuff in addition to a binder made 103 00:06:31,520 --> 00:06:36,520 Speaker 1: from bitamin or a bitumin like substance. Meanwhile, the Egyptians 104 00:06:36,600 --> 00:06:40,839 Speaker 1: and the Phoenicians were using gypsum and lime. Gypsum is 105 00:06:40,920 --> 00:06:45,520 Speaker 1: made of calcium sulfate dihydrate, and it's a big ingredient 106 00:06:45,600 --> 00:06:51,279 Speaker 1: and lots of stuff including drywall, chalk, fertilizer, and modern cement. 107 00:06:52,040 --> 00:06:55,440 Speaker 1: Lime the material, not the fruit, so you don't you 108 00:06:55,440 --> 00:06:57,720 Speaker 1: don't put this in a coconut and drink them both up. 109 00:06:58,040 --> 00:07:00,960 Speaker 1: In this case, we're talking about an inorganic mineral made 110 00:07:00,960 --> 00:07:05,559 Speaker 1: of calcium and various oxides. The Greeks also use lime, 111 00:07:06,040 --> 00:07:09,840 Speaker 1: and they treated it in kilns to create burnt lime. 112 00:07:10,080 --> 00:07:14,800 Speaker 1: Like kilns are an important element of creating cement. You 113 00:07:14,800 --> 00:07:18,640 Speaker 1: couldn't just use this material as it was, you know, 114 00:07:18,880 --> 00:07:21,679 Speaker 1: found in nature. You had to treat it to heat 115 00:07:21,800 --> 00:07:26,960 Speaker 1: in order to have the chemical transition into what would 116 00:07:27,000 --> 00:07:31,240 Speaker 1: become concrete or cement. Rather, we'll talk more about processing 117 00:07:31,320 --> 00:07:33,360 Speaker 1: lime in a bit, because that does play a huge 118 00:07:33,480 --> 00:07:36,640 Speaker 1: part in the production of cement. In fact, many early 119 00:07:36,720 --> 00:07:41,360 Speaker 1: civilizations would use kilns similar to or in some cases 120 00:07:41,440 --> 00:07:44,960 Speaker 1: exactly the same as the kilns that they would use 121 00:07:45,000 --> 00:07:48,760 Speaker 1: to fire pottery. The kilns would reach the temperatures needed 122 00:07:48,800 --> 00:07:52,200 Speaker 1: to quote unquote burn the lime, making it suitable to 123 00:07:52,280 --> 00:07:55,200 Speaker 1: use as a binding agent. Most of these early forms 124 00:07:55,200 --> 00:07:59,160 Speaker 1: of protoconcrete would cure in the air. They hardened upon 125 00:07:59,280 --> 00:08:02,880 Speaker 1: exposure to the air, or, as spinn Thalo put it 126 00:08:02,920 --> 00:08:06,400 Speaker 1: in an article in nineteen sixty seven, quote lime that 127 00:08:06,480 --> 00:08:10,320 Speaker 1: needs air to achieve strength end quote. I like that phrasing. 128 00:08:11,080 --> 00:08:13,880 Speaker 1: Then came the Romans. And while the Romans stole a 129 00:08:13,880 --> 00:08:17,440 Speaker 1: ton of stuff from the Greeks, they also innovated quite 130 00:08:17,440 --> 00:08:19,680 Speaker 1: a lot of stuff themselves, and one of those things 131 00:08:19,680 --> 00:08:22,320 Speaker 1: they innovated was concrete. Now, the Greeks had been using 132 00:08:22,360 --> 00:08:25,600 Speaker 1: concrete a little bit, but not anywhere to the extent 133 00:08:26,040 --> 00:08:29,840 Speaker 1: that the Romans did. And the Romans discovered natural cements 134 00:08:29,880 --> 00:08:33,439 Speaker 1: called Pozzolan's. Actually, I should say that Pezzolan's might have 135 00:08:33,480 --> 00:08:37,640 Speaker 1: already been in use pre Roman times, but the Romans 136 00:08:37,640 --> 00:08:42,359 Speaker 1: really went ham on the stuff. Mm hmm, ham and pozzolan. 137 00:08:42,920 --> 00:08:45,400 Speaker 1: So what the heck is pozolan? Well, according to the 138 00:08:45,520 --> 00:08:51,080 Speaker 1: American Concrete Institute, it is quote a solicitous and aluminous 139 00:08:51,120 --> 00:08:56,360 Speaker 1: material that in itself possesses little or no simentitious value, 140 00:08:56,440 --> 00:08:59,920 Speaker 1: but will in finally divided form, and in the present 141 00:09:00,040 --> 00:09:04,679 Speaker 1: some moisture chemically react with calcium hydroxide at ordinary temperatures 142 00:09:04,720 --> 00:09:09,920 Speaker 1: to form compounds having sementitious properties. End quote. That is 143 00:09:09,960 --> 00:09:13,880 Speaker 1: a mouthful, but in plain English it means that it's 144 00:09:13,880 --> 00:09:16,640 Speaker 1: a material that when ground up into a powder and 145 00:09:16,760 --> 00:09:21,440 Speaker 1: mixed with water and material that contains calcium hydroxide, it 146 00:09:21,520 --> 00:09:26,080 Speaker 1: becomes cement. Like that is, it can bind aggregate as 147 00:09:26,200 --> 00:09:30,280 Speaker 1: cement and form concrete. Actually, I should point out in 148 00:09:30,320 --> 00:09:32,360 Speaker 1: fact I Probace should have done this already. Cement and 149 00:09:32,400 --> 00:09:36,199 Speaker 1: concrete are not the same thing. They are not synonymous. 150 00:09:36,200 --> 00:09:41,079 Speaker 1: Cement is to concrete what flour is to a cake. Right. 151 00:09:41,160 --> 00:09:44,280 Speaker 1: It's an ingredient, it's an important part, but it is 152 00:09:44,320 --> 00:09:47,920 Speaker 1: not the same thing anyway. The source for the Romans 153 00:09:47,960 --> 00:09:51,679 Speaker 1: was a puzzolonic ash, which in itself came from volcanic 154 00:09:51,760 --> 00:09:55,840 Speaker 1: ash and pumice. So the Romans would collect this ash 155 00:09:55,880 --> 00:09:58,200 Speaker 1: and they would use it with calcium hydroxide to create 156 00:09:58,200 --> 00:10:01,640 Speaker 1: their cement. When did they start doing this, well, we're 157 00:10:01,679 --> 00:10:05,760 Speaker 1: not really sure. It wouldn't have been any later than 158 00:10:05,880 --> 00:10:09,480 Speaker 1: one fifty before Common era or B C. As there's 159 00:10:09,520 --> 00:10:12,400 Speaker 1: evidence of concrete structures dating from around that time period, 160 00:10:12,800 --> 00:10:16,200 Speaker 1: so it was definitely at least as late as that. 161 00:10:16,280 --> 00:10:19,320 Speaker 1: It was probably earlier, much earlier. But there's just no 162 00:10:19,520 --> 00:10:23,679 Speaker 1: Roman record that says, quote, it's to seventy four b C. 163 00:10:23,920 --> 00:10:26,960 Speaker 1: And we just invented concrete. Also, why are our years 164 00:10:27,040 --> 00:10:31,240 Speaker 1: counting down backward? Anyway? I'm off to the vomitorium end quote. 165 00:10:31,720 --> 00:10:34,880 Speaker 1: And yeah, I made at least two dumb jokes based 166 00:10:34,880 --> 00:10:38,880 Speaker 1: off inaccurate representations of ancient Rome's timekeeping in terminology, but 167 00:10:38,920 --> 00:10:43,200 Speaker 1: I couldn't resist. Concrete would play an enormous part in 168 00:10:43,360 --> 00:10:46,960 Speaker 1: the Roman architectural revolution. In fact, it was such a 169 00:10:46,960 --> 00:10:50,920 Speaker 1: crucial component of that movement that we sometimes referred to 170 00:10:50,960 --> 00:10:54,880 Speaker 1: it as the concrete Revolution. This marked a period in 171 00:10:55,000 --> 00:10:59,920 Speaker 1: Roman history of huge architectural projects, including the famous Roman Pantheon, 172 00:11:00,040 --> 00:11:03,520 Speaker 1: on which was has a dome made from concrete that, 173 00:11:03,640 --> 00:11:07,839 Speaker 1: from its shape, supports itself with no need for additional 174 00:11:08,280 --> 00:11:11,480 Speaker 1: columns or other supports apart from the walls, which kind 175 00:11:11,480 --> 00:11:16,040 Speaker 1: of act like columns. The Romans could build enormous structures 176 00:11:16,040 --> 00:11:20,280 Speaker 1: thanks to concrete, which could be poured and then cured. Well, 177 00:11:20,360 --> 00:11:23,840 Speaker 1: it's the quote process of controlling the rate and extent 178 00:11:24,000 --> 00:11:28,160 Speaker 1: of moisture loss from concrete during cement hydration end quote. 179 00:11:28,640 --> 00:11:34,199 Speaker 1: That's the helpful definition from cement, Concrete and Aggregates Australia. 180 00:11:34,280 --> 00:11:37,800 Speaker 1: So let's dive into that a little bit further. Hydration 181 00:11:38,000 --> 00:11:40,520 Speaker 1: is the mixing of water with cement and aggregate that 182 00:11:40,559 --> 00:11:43,719 Speaker 1: gets this whole binding process going. And I realized this 183 00:11:43,800 --> 00:11:46,160 Speaker 1: is skipping over the modern method of producing cement, but 184 00:11:46,240 --> 00:11:48,800 Speaker 1: we will get back to that a bit later. Right now, 185 00:11:49,040 --> 00:11:52,840 Speaker 1: we're talking about Roman concrete, which uses a natural cement 186 00:11:52,960 --> 00:11:57,640 Speaker 1: with fewer controls, and that meant consistency was a little variable. Okay, 187 00:11:57,679 --> 00:12:01,079 Speaker 1: So you make the concrete by mixing together water, cement, 188 00:12:01,280 --> 00:12:04,960 Speaker 1: and the aggregate, which forms a workable paste. You put 189 00:12:05,000 --> 00:12:07,079 Speaker 1: this where you want it to go, such as in 190 00:12:07,120 --> 00:12:11,040 Speaker 1: a form mold. So imagine that you've got like a 191 00:12:11,080 --> 00:12:14,079 Speaker 1: wooden box that doesn't have a top and the sides 192 00:12:14,120 --> 00:12:17,000 Speaker 1: and bottom are all removable, So you put it together. 193 00:12:17,240 --> 00:12:20,000 Speaker 1: Then you pour the paste into that box so it 194 00:12:20,040 --> 00:12:22,520 Speaker 1: takes on the shape of the box. Then you remove 195 00:12:22,640 --> 00:12:25,640 Speaker 1: the wood once it's all done. But the once you're 196 00:12:25,679 --> 00:12:30,480 Speaker 1: done bit is important. So the Roman concrete, like modern concrete, 197 00:12:30,480 --> 00:12:35,240 Speaker 1: required hydration. That is, the cement needed moisture to harden further. 198 00:12:35,840 --> 00:12:39,880 Speaker 1: Once dried out, concrete is set, and generally speaking, the 199 00:12:39,920 --> 00:12:43,400 Speaker 1: faster it dries out, the weaker it is. Don't get 200 00:12:43,440 --> 00:12:46,240 Speaker 1: me wrong, it's still strong stuff and it can withstand 201 00:12:46,360 --> 00:12:51,079 Speaker 1: incredible compressive forces, that is, forces that push down on it, 202 00:12:51,320 --> 00:12:53,880 Speaker 1: you know, in an attempt to compress it. But it 203 00:12:53,920 --> 00:12:56,480 Speaker 1: can also be a little brittle, and if the concrete 204 00:12:56,520 --> 00:13:01,280 Speaker 1: remains wet, the reactions within cement will tenue and sometimes 205 00:13:01,280 --> 00:13:04,720 Speaker 1: for years if it remains moist before drying out. It's 206 00:13:04,760 --> 00:13:07,719 Speaker 1: this process of hardening that is called curing. It's not 207 00:13:08,280 --> 00:13:10,800 Speaker 1: the drying out part, it's the hardening part that's that's 208 00:13:10,840 --> 00:13:14,080 Speaker 1: kind of the the end process is dried out. It's 209 00:13:14,120 --> 00:13:16,640 Speaker 1: the keeping it wet in order to get the hardness 210 00:13:16,640 --> 00:13:20,040 Speaker 1: and strength you want. That's important. Um and in fact 211 00:13:20,080 --> 00:13:24,720 Speaker 1: concrete part of that mass is made up of water. Chemically, 212 00:13:24,800 --> 00:13:29,080 Speaker 1: what's going on is calcium silicates are undergoing an exothermic reaction. 213 00:13:29,080 --> 00:13:34,120 Speaker 1: As they interact with water, they release hydroxide ions, calcium ions, 214 00:13:34,160 --> 00:13:37,400 Speaker 1: and heat. The bit about releasing heat is what makes 215 00:13:37,440 --> 00:13:42,960 Speaker 1: this an exothermic reaction. Eventually, calcium and hydroxide ions saturate 216 00:13:43,040 --> 00:13:47,840 Speaker 1: the system and they begin to form calcium hydroxide crystals. Meanwhile, 217 00:13:47,920 --> 00:13:52,760 Speaker 1: calcium silicate hydrate forms. The crystalline structures provide seed points 218 00:13:52,800 --> 00:13:55,240 Speaker 1: for further ions to kind of glom onto, and the 219 00:13:55,280 --> 00:13:57,920 Speaker 1: process can grow from there. But it does need water 220 00:13:58,040 --> 00:14:01,920 Speaker 1: to continue this reaction, and as those crystals form, the 221 00:14:02,160 --> 00:14:06,480 Speaker 1: concrete gets harder and stronger. Controlling this reaction falls to 222 00:14:06,559 --> 00:14:09,280 Speaker 1: the rate at which water molecules can diffuse through the 223 00:14:09,280 --> 00:14:14,080 Speaker 1: calcium silicate coating. As the reaction progresses, that coding gets 224 00:14:14,120 --> 00:14:17,000 Speaker 1: thicker and it gets more difficult for water to make 225 00:14:17,080 --> 00:14:20,280 Speaker 1: its way through, which in turn means the reaction begins 226 00:14:20,280 --> 00:14:23,480 Speaker 1: to slow down. Hydration will continue as long as water 227 00:14:23,560 --> 00:14:25,720 Speaker 1: can get into the system and as long as there 228 00:14:25,720 --> 00:14:30,480 Speaker 1: remains unhydrated compounds within the paste. This process can go 229 00:14:30,520 --> 00:14:34,920 Speaker 1: on for days or weeks, or months or even years. 230 00:14:35,080 --> 00:14:38,280 Speaker 1: I'll be there for you when the rain starts to fall. 231 00:14:39,000 --> 00:14:42,320 Speaker 1: As long as water can permeate an access unhydrated cement, 232 00:14:42,800 --> 00:14:47,440 Speaker 1: the process will continue. Also, while the reactions release heat, 233 00:14:47,840 --> 00:14:51,640 Speaker 1: this process itself goes through an interesting revolution. Early on 234 00:14:51,800 --> 00:14:55,440 Speaker 1: in the hydration process, the reactive mixture will release a 235 00:14:55,480 --> 00:14:57,880 Speaker 1: good amount of heat, the temperature will will go up 236 00:14:57,920 --> 00:15:01,360 Speaker 1: several degrees, but after the first now fifteen minutes to 237 00:15:01,360 --> 00:15:04,440 Speaker 1: half an hour of the reaction, that temperature starts to drop. 238 00:15:05,160 --> 00:15:07,360 Speaker 1: Then a few hours in the amount of heat it 239 00:15:07,400 --> 00:15:10,880 Speaker 1: releases will begin to climb again, and over several hours 240 00:15:10,880 --> 00:15:14,120 Speaker 1: it will peak, and once you get like twenty hours in, 241 00:15:14,880 --> 00:15:18,600 Speaker 1: it will then begin to slowly drop the temperature again, 242 00:15:18,840 --> 00:15:22,000 Speaker 1: very slowly ramping down. And what's happening is that the 243 00:15:22,120 --> 00:15:26,360 Speaker 1: rate of the reactions themselves changes as things initiate and 244 00:15:26,400 --> 00:15:29,040 Speaker 1: then water it continues to react with the cement mixture. 245 00:15:29,400 --> 00:15:31,800 Speaker 1: Then it gradually becomes more difficult for water to make 246 00:15:31,800 --> 00:15:35,600 Speaker 1: its way to unhydrated elements of the cement, so the 247 00:15:35,600 --> 00:15:39,920 Speaker 1: curing process can be done without having to heat anything 248 00:15:39,960 --> 00:15:43,680 Speaker 1: else up, and in fact it itself heats up. As 249 00:15:43,720 --> 00:15:46,000 Speaker 1: we'll learn a bit later, that's kind of the opposite 250 00:15:46,000 --> 00:15:49,800 Speaker 1: of the actual modern process of making cement. So concrete 251 00:15:49,880 --> 00:15:54,480 Speaker 1: formation is exothermic, but the production of cement turns out 252 00:15:54,480 --> 00:15:58,720 Speaker 1: to be endo thermic. I'll explain more later on this episode. 253 00:15:59,400 --> 00:16:02,320 Speaker 1: Now we've got some more to say about the process 254 00:16:02,600 --> 00:16:06,160 Speaker 1: of concrete forming, and we'll talk a lot more about 255 00:16:06,200 --> 00:16:08,880 Speaker 1: cement in just a moment. But first let's take a 256 00:16:08,960 --> 00:16:19,880 Speaker 1: quick break. Now. I mentioned that if concrete dries out quickly, 257 00:16:20,200 --> 00:16:23,840 Speaker 1: it won't be as strong as concrete that was hydrated properly. 258 00:16:24,000 --> 00:16:26,080 Speaker 1: But let's get a bit more detailed with that, because 259 00:16:26,120 --> 00:16:29,080 Speaker 1: it's not as simple as just you know, drenching wet 260 00:16:29,160 --> 00:16:31,720 Speaker 1: cement mix as you wait for it to cure. The 261 00:16:31,760 --> 00:16:35,120 Speaker 1: amount of water you add makes a difference. The ratio 262 00:16:35,240 --> 00:16:38,600 Speaker 1: of water to cement is important. A low water to 263 00:16:38,640 --> 00:16:41,080 Speaker 1: cement ratio means you're gonna end up with concrete that's 264 00:16:41,200 --> 00:16:44,280 Speaker 1: very strong, but it's also very difficult to work. So, 265 00:16:44,280 --> 00:16:47,720 Speaker 1: in other words, the paste will be extremely viscous and 266 00:16:47,760 --> 00:16:50,280 Speaker 1: you might end up with shapes you totally didn't intend 267 00:16:50,320 --> 00:16:52,320 Speaker 1: and now you're stuck with them unless you, you know, 268 00:16:52,400 --> 00:16:56,680 Speaker 1: grab some heavy duty tools. High water to cement ratio 269 00:16:56,760 --> 00:16:59,480 Speaker 1: means you're gonna have a paste that's really workable, but 270 00:16:59,600 --> 00:17:01,880 Speaker 1: the over all strength of the concrete will be low. 271 00:17:02,400 --> 00:17:05,959 Speaker 1: So it's not just how long the cement is kept moist, 272 00:17:06,320 --> 00:17:08,720 Speaker 1: but how much water you use to do it. In 273 00:17:08,760 --> 00:17:11,240 Speaker 1: our modern era, there are other things we can add 274 00:17:11,280 --> 00:17:14,560 Speaker 1: to cement and aggregate to improve stuff like workability, and 275 00:17:14,600 --> 00:17:17,840 Speaker 1: plasticity and strength. But let's get back to the Romans, 276 00:17:17,920 --> 00:17:19,880 Speaker 1: because we've got to get back to them, because they're 277 00:17:19,920 --> 00:17:24,560 Speaker 1: always Roman around. It's a dad joke. The Romans learned 278 00:17:24,600 --> 00:17:28,760 Speaker 1: about the hydration process and produced a lot of concrete, 279 00:17:28,760 --> 00:17:32,000 Speaker 1: at least for the time anyway, They relied on the 280 00:17:32,080 --> 00:17:36,040 Speaker 1: natural cement features of volcanic ash. Many of those structures 281 00:17:36,080 --> 00:17:39,560 Speaker 1: exist in whole or in part today, which is really 282 00:17:39,600 --> 00:17:42,399 Speaker 1: just a testament to the strength and durability of concrete. 283 00:17:42,960 --> 00:17:45,720 Speaker 1: But there was a pretty long span of time between 284 00:17:45,760 --> 00:17:48,880 Speaker 1: the fall of the Roman Empire and the widespread use 285 00:17:48,920 --> 00:17:52,679 Speaker 1: of concrete and other civilizations outside of some uses in 286 00:17:52,760 --> 00:17:56,159 Speaker 1: building in churches and cathedrals, And it may be that 287 00:17:56,240 --> 00:17:59,679 Speaker 1: the knowledge of producing concrete was largely kept in religious 288 00:17:59,720 --> 00:18:03,120 Speaker 1: scents as far back as the earliest examples of the stuff, 289 00:18:03,520 --> 00:18:06,240 Speaker 1: which gave the edge to the clerical folks out there 290 00:18:06,240 --> 00:18:09,679 Speaker 1: over everybody else. So the Roman Empire trips on a 291 00:18:09,680 --> 00:18:14,000 Speaker 1: bananappeal and falls and Europe plunges into the Dark Ages 292 00:18:14,720 --> 00:18:16,959 Speaker 1: kind of. I mean, the history of the Dark Ages 293 00:18:17,040 --> 00:18:20,680 Speaker 1: is actually really complicated, but for our purposes, the secrets 294 00:18:20,720 --> 00:18:24,280 Speaker 1: to cement and concrete are largely lost until the fifteenth 295 00:18:24,280 --> 00:18:28,720 Speaker 1: century when the rediscovery of an old manuscript written by 296 00:18:28,920 --> 00:18:34,359 Speaker 1: Marcus vitruvious Polio, usually just called Vitruvius, rekindled interest. Now, 297 00:18:34,400 --> 00:18:37,520 Speaker 1: Vitruvius was an architect and engineer way back in the 298 00:18:37,640 --> 00:18:41,760 Speaker 1: first century b c. He wrote a long manuscript about 299 00:18:41,800 --> 00:18:45,439 Speaker 1: the principles of architecture, and it included a section on 300 00:18:45,520 --> 00:18:50,119 Speaker 1: the production of Roman concrete. So as the Renaissance began 301 00:18:50,200 --> 00:18:54,000 Speaker 1: to bloom in Europe, there was a new interest in concrete. 302 00:18:54,200 --> 00:18:58,520 Speaker 1: In fact, Giovanni Giocondo used Roman concrete to build a 303 00:18:58,560 --> 00:19:01,480 Speaker 1: part of the bridge called the Pont the Notre Dame 304 00:19:01,640 --> 00:19:05,720 Speaker 1: in Paris in fourteen nine, which, as I understand it 305 00:19:05,760 --> 00:19:08,480 Speaker 1: is widely thought of as the first example of the 306 00:19:08,520 --> 00:19:12,399 Speaker 1: modern use of concrete, and it was also necessary. The 307 00:19:12,600 --> 00:19:16,159 Speaker 1: Pont Notre Dame sometimes gets called the most ancient of 308 00:19:16,240 --> 00:19:19,840 Speaker 1: bridges in Paris, but this is largely a matter of 309 00:19:19,920 --> 00:19:24,520 Speaker 1: point of view, because it hasn't always been the same bridge. 310 00:19:24,960 --> 00:19:28,320 Speaker 1: The Pont Neuf is the oldest bridge that remains in 311 00:19:28,359 --> 00:19:31,800 Speaker 1: its original form in Paris, but there has been a 312 00:19:31,840 --> 00:19:35,920 Speaker 1: bridge at the location of Polt Notre Dame. The longest. However, 313 00:19:36,280 --> 00:19:40,600 Speaker 1: that Pont Notre Dame Bridge has gone through multiple collapses 314 00:19:40,680 --> 00:19:44,200 Speaker 1: and demolitions and otherwise has been destroyed numerous times, only 315 00:19:44,240 --> 00:19:47,480 Speaker 1: to have been rebuilt. So this is a real ship 316 00:19:47,520 --> 00:19:50,760 Speaker 1: of theseus kind of thing we've got going on here anyway. 317 00:19:51,119 --> 00:19:54,600 Speaker 1: Giacondo used a recipe of Roman concrete as part of 318 00:19:54,600 --> 00:19:57,720 Speaker 1: the rebuilding process after the bridge suffered a collapse in 319 00:19:57,760 --> 00:20:01,840 Speaker 1: fourteen ninety nine when the way of houses on the 320 00:20:01,840 --> 00:20:04,680 Speaker 1: bridge proved to be too much for the old structure. 321 00:20:05,359 --> 00:20:09,040 Speaker 1: This version of the bridge, the concrete one, stood largely 322 00:20:09,119 --> 00:20:12,919 Speaker 1: unaltered until eighteen fifty three, So that was back in 323 00:20:12,960 --> 00:20:16,760 Speaker 1: four but widespread use really wouldn't kick into high gear 324 00:20:16,800 --> 00:20:20,480 Speaker 1: for a few more centuries. In seventeen seventy four, an 325 00:20:20,560 --> 00:20:24,080 Speaker 1: English engineer by the name John Smeaton learned that by 326 00:20:24,160 --> 00:20:27,800 Speaker 1: using quicklime as an ingredient for making cement, he could 327 00:20:27,880 --> 00:20:32,280 Speaker 1: make better, harder cement, and later in seventeen ninety three 328 00:20:32,560 --> 00:20:38,240 Speaker 1: he discovered something else which brings us to calcination. Calcination 329 00:20:38,680 --> 00:20:41,720 Speaker 1: is the process of heating up a solid to a 330 00:20:42,000 --> 00:20:44,960 Speaker 1: very high temperature, and the purposes to burn off any 331 00:20:45,119 --> 00:20:49,000 Speaker 1: volatile substances within that solid mass so that you're left 332 00:20:49,000 --> 00:20:52,960 Speaker 1: with a more pure lump of whatever it was you 333 00:20:53,119 --> 00:20:57,480 Speaker 1: started off with. Smeaton discovered that calcinating limestone that had 334 00:20:57,640 --> 00:21:01,960 Speaker 1: clay content in it would produce hydraulic lime. As the 335 00:21:02,040 --> 00:21:06,520 Speaker 1: name implies, this produces a lime that hardens underwater. Three 336 00:21:06,600 --> 00:21:10,640 Speaker 1: years later, an Englishman named James Parker patented a hydraulic 337 00:21:10,760 --> 00:21:16,080 Speaker 1: cement produced by calcinating limestone that contained clay. Engineers began 338 00:21:16,359 --> 00:21:21,679 Speaker 1: building lime kilns, essentially ovens dedicated to calcinating limestone. So 339 00:21:22,600 --> 00:21:27,040 Speaker 1: they were trying to recreate the effect that those ancient 340 00:21:27,119 --> 00:21:32,359 Speaker 1: peoples saw around their their fires, their food fires, years 341 00:21:32,359 --> 00:21:36,119 Speaker 1: and years and years centuries earlier. Now let's skip ahead 342 00:21:36,160 --> 00:21:40,720 Speaker 1: to eighteen twenty four. A builder named Joseph Asten found 343 00:21:40,760 --> 00:21:43,359 Speaker 1: that by grinding up chalk and putting it in a 344 00:21:43,440 --> 00:21:47,800 Speaker 1: kiln with clay produced an even stronger type of cement. 345 00:21:48,600 --> 00:21:52,160 Speaker 1: This is the type of cement we call Portland cement. 346 00:21:52,600 --> 00:21:56,320 Speaker 1: It's named after the Isle of Portland in the English Channel. 347 00:21:56,760 --> 00:22:00,520 Speaker 1: It's where a type of limestone called Portland stone comes from, 348 00:22:00,600 --> 00:22:03,399 Speaker 1: and that stone played a huge part in British architecture. 349 00:22:03,520 --> 00:22:07,760 Speaker 1: Fact it still does. More people made contributions towards the 350 00:22:07,880 --> 00:22:11,679 Speaker 1: understanding and production of cement. But the next innovation I 351 00:22:11,720 --> 00:22:15,920 Speaker 1: want to talk about came courtesy of Frederick Ransom. Ransom 352 00:22:15,960 --> 00:22:19,840 Speaker 1: wanted to find a way to consistently make the best cement, 353 00:22:19,920 --> 00:22:23,280 Speaker 1: which required a new type of kiln. So the old 354 00:22:23,320 --> 00:22:28,320 Speaker 1: cement kilns were essentially vertically aligned ovens. So think of 355 00:22:28,359 --> 00:22:31,600 Speaker 1: like a chimney. You would load this stuff up with 356 00:22:31,720 --> 00:22:35,080 Speaker 1: limestone and clay, You would have fuel at the bottom. 357 00:22:35,280 --> 00:22:39,280 Speaker 1: You get the kiln up to a certain temperature, and 358 00:22:39,359 --> 00:22:42,119 Speaker 1: you would kind of mix everything together, and in between 359 00:22:42,160 --> 00:22:44,399 Speaker 1: loads you might even allow the oven to go cool, 360 00:22:44,480 --> 00:22:47,879 Speaker 1: which represented a pretty darn big waste of energy because 361 00:22:48,400 --> 00:22:50,680 Speaker 1: it takes a lot of fuel to get kilns up 362 00:22:50,720 --> 00:22:53,720 Speaker 1: to temperature, and once you get it up there, it 363 00:22:53,760 --> 00:22:55,640 Speaker 1: takes less fuel for you to just keep it there 364 00:22:55,640 --> 00:22:57,639 Speaker 1: than it would if you let it go cold and 365 00:22:57,680 --> 00:23:00,359 Speaker 1: had to start it up again. And by high to pachures, 366 00:23:00,400 --> 00:23:04,359 Speaker 1: we're talking up around four dred degrees celsius and hotter. 367 00:23:04,960 --> 00:23:07,439 Speaker 1: The result of this process is that the limestone and 368 00:23:07,440 --> 00:23:11,880 Speaker 1: the clay partially melt together into nodules that are called clinker. 369 00:23:12,480 --> 00:23:16,439 Speaker 1: The clinker, once cooled, can be crushed into a powder 370 00:23:16,600 --> 00:23:20,520 Speaker 1: mixed with gypsum, and then you've got your cement. A 371 00:23:20,560 --> 00:23:22,880 Speaker 1: lot of stuff actually happens in this process, but I'm 372 00:23:22,880 --> 00:23:25,400 Speaker 1: going to explain more in just a moment, so stick 373 00:23:25,440 --> 00:23:28,560 Speaker 1: with me. Ransom figured out that one way you can 374 00:23:28,640 --> 00:23:32,200 Speaker 1: make a better kiln is to go from this vertically aligned, 375 00:23:32,800 --> 00:23:37,160 Speaker 1: you know, smokestack style kiln to a tilted one, one 376 00:23:37,200 --> 00:23:40,440 Speaker 1: that was almost closer to horizontal than vertical, but still 377 00:23:40,480 --> 00:23:44,240 Speaker 1: on an incline. So the raised end, the part that's 378 00:23:44,320 --> 00:23:47,760 Speaker 1: higher up, would be where you would feed limestone and 379 00:23:47,800 --> 00:23:51,360 Speaker 1: clay into the kiln. On the opposite end, the lower end, 380 00:23:51,680 --> 00:23:54,600 Speaker 1: you would have an opening at the base where clinker 381 00:23:54,640 --> 00:23:56,720 Speaker 1: could pass through, and that's also where you would have 382 00:23:56,760 --> 00:24:00,000 Speaker 1: your heat source that would get the raw materials up 383 00:24:00,040 --> 00:24:03,880 Speaker 1: to the right melting point, and the whole thing would rotate, 384 00:24:04,240 --> 00:24:07,960 Speaker 1: shifting material around and causing it to gradually move down 385 00:24:08,000 --> 00:24:11,280 Speaker 1: the length of the kiln. It was a rotating kiln, 386 00:24:11,800 --> 00:24:14,159 Speaker 1: so you would feed in your mix of limestone and 387 00:24:14,200 --> 00:24:16,639 Speaker 1: clay at the top and at that end of the kiln, 388 00:24:16,720 --> 00:24:19,679 Speaker 1: far from the heat source, you would have the relatively 389 00:24:19,760 --> 00:24:25,560 Speaker 1: chilly temperatures of between seventy two degrees celsius. At this temperature, 390 00:24:25,640 --> 00:24:29,640 Speaker 1: any water content in the feed would evaporate off. This 391 00:24:29,720 --> 00:24:32,640 Speaker 1: is also the end where any gas is given off 392 00:24:32,640 --> 00:24:36,040 Speaker 1: by the process would escape. The raw material would then 393 00:24:36,080 --> 00:24:39,600 Speaker 1: sift down further into the kiln as the kiln rotated, 394 00:24:39,760 --> 00:24:43,119 Speaker 1: and it would start to reach hotter segments. So once 395 00:24:43,160 --> 00:24:47,080 Speaker 1: the material reached between four hundred to six hundred degrees celsius, 396 00:24:47,520 --> 00:24:52,040 Speaker 1: the clay would start to decompose into oxides like silicon 397 00:24:52,160 --> 00:24:57,000 Speaker 1: dioxide and aluminum oxide, and the limestone would decompose into 398 00:24:57,119 --> 00:25:02,720 Speaker 1: calcium carbonate, magnesium oxide, and some carbon dioxide. So some 399 00:25:02,800 --> 00:25:06,560 Speaker 1: of that carbon dioxide would then expel out the end 400 00:25:06,720 --> 00:25:10,520 Speaker 1: of the kiln, but we would continue our journey down 401 00:25:10,600 --> 00:25:13,760 Speaker 1: the kiln, and now the raw materials are reaching around 402 00:25:13,840 --> 00:25:17,040 Speaker 1: six hundred and nine hundred celsius somewhere in that range, 403 00:25:17,359 --> 00:25:20,080 Speaker 1: and the calcium carbonate from the limestone would react with 404 00:25:20,119 --> 00:25:23,840 Speaker 1: the silicon dioxide to form a material called the light 405 00:25:24,200 --> 00:25:26,560 Speaker 1: or B E L I T E, also known as 406 00:25:26,800 --> 00:25:31,960 Speaker 1: die calcium silicate. So this again continues to sift down 407 00:25:32,000 --> 00:25:34,960 Speaker 1: the length of this rotating kiln, and of course it 408 00:25:35,000 --> 00:25:37,080 Speaker 1: gets even hotter as it gets closer to the source 409 00:25:37,119 --> 00:25:41,440 Speaker 1: of heat, and around nine hundred two thousand, fifty degrees celsius. 410 00:25:41,480 --> 00:25:46,320 Speaker 1: Any remaining calcium carbonate decomposes into calcium oxide and more 411 00:25:46,359 --> 00:25:49,520 Speaker 1: carbon dioxide, which again exhausts out the end of the kiln. 412 00:25:50,160 --> 00:25:52,920 Speaker 1: Then the material gets towards the point where the hottest 413 00:25:53,000 --> 00:25:55,440 Speaker 1: section is with temperature is getting up to around four 414 00:25:55,840 --> 00:26:00,080 Speaker 1: hundred fifty degrees celsius, and the raw material begins to 415 00:26:00,160 --> 00:26:04,520 Speaker 1: melt and fuse into clinker, which sifts down through and 416 00:26:04,640 --> 00:26:06,720 Speaker 1: opening at the base of the kiln and falls into 417 00:26:06,800 --> 00:26:11,280 Speaker 1: a cooling tank. Modern rotating kilns recapture the heat from 418 00:26:11,320 --> 00:26:13,760 Speaker 1: the clinker and they use that as part of the 419 00:26:13,760 --> 00:26:17,800 Speaker 1: way to power the system. So if you follow that process, 420 00:26:17,920 --> 00:26:21,560 Speaker 1: you realize a few really big things. First, the chemical 421 00:26:21,640 --> 00:26:25,960 Speaker 1: process to create Portland's cement is an endothermic reaction, meaning 422 00:26:25,960 --> 00:26:29,080 Speaker 1: you actually have to add heat to make this reaction happen. 423 00:26:29,359 --> 00:26:32,600 Speaker 1: And we contrast to that to the two concrete curing 424 00:26:33,040 --> 00:26:36,840 Speaker 1: that's an exothermic reaction. It gives off heat. You also 425 00:26:36,880 --> 00:26:39,520 Speaker 1: probably heard there are a couple of steps there that 426 00:26:39,640 --> 00:26:44,000 Speaker 1: involve a release of carbon dot oxide in this chemical process. 427 00:26:44,040 --> 00:26:48,679 Speaker 1: That's one of the big byproducts of cement production carbon dioxide. 428 00:26:48,880 --> 00:26:51,360 Speaker 1: But it doesn't stop there. We also have to consider 429 00:26:51,560 --> 00:26:54,360 Speaker 1: the whole system, not just what gets produced through this 430 00:26:54,440 --> 00:26:58,080 Speaker 1: chemical reaction. So to power the kilns, I mean to 431 00:26:58,760 --> 00:27:01,480 Speaker 1: make the heat, we need fuel and that tends to 432 00:27:01,520 --> 00:27:05,399 Speaker 1: be fossil fuels, and burning fossil fuels also produces carbon 433 00:27:05,440 --> 00:27:10,080 Speaker 1: dioxide emissions. So cement production contributes a significant amount of 434 00:27:10,119 --> 00:27:13,439 Speaker 1: CEO two emissions, both in the chemical process itself of 435 00:27:13,560 --> 00:27:17,639 Speaker 1: cement becoming cement and also the fossil fuels that you 436 00:27:17,680 --> 00:27:20,040 Speaker 1: need to burn in order to create the heat to 437 00:27:20,080 --> 00:27:24,120 Speaker 1: get this reaction going. In fact, global cement production accounts 438 00:27:24,119 --> 00:27:27,320 Speaker 1: for about five percent of all CEO two emissions, which 439 00:27:27,359 --> 00:27:31,720 Speaker 1: is a staggering amount for one specific process. And when 440 00:27:31,760 --> 00:27:35,080 Speaker 1: you factor into the equation other considerations, like the fact 441 00:27:35,119 --> 00:27:37,600 Speaker 1: you still have to transport the cement to wherever it's 442 00:27:37,640 --> 00:27:39,959 Speaker 1: going to be used, you start to see how our 443 00:27:40,000 --> 00:27:45,000 Speaker 1: dependence upon cement and concrete becomes challenging. Now, let's get 444 00:27:45,040 --> 00:27:50,560 Speaker 1: some stuff straight. Concrete is incredibly useful and and important. 445 00:27:50,640 --> 00:27:53,479 Speaker 1: I mean, without concrete, there'd be no way to build 446 00:27:53,600 --> 00:27:57,000 Speaker 1: stable structures beyond a few stories, which would mean that 447 00:27:57,040 --> 00:27:59,159 Speaker 1: we would have to sprawl out even more than we 448 00:27:59,240 --> 00:28:02,640 Speaker 1: already do. And I should also add that the fact 449 00:28:02,680 --> 00:28:06,000 Speaker 1: we can build really tall structures like skyscrapers isn't just 450 00:28:06,359 --> 00:28:11,639 Speaker 1: due to concrete. You see, concrete does have incredible compressive strength, 451 00:28:11,720 --> 00:28:15,360 Speaker 1: that is, it can hold a ton of weight literally 452 00:28:15,400 --> 00:28:17,520 Speaker 1: can hold a ton of weight, tons and tons of weight, 453 00:28:17,760 --> 00:28:21,840 Speaker 1: but doesn't have great tensile strength. If you build a 454 00:28:21,920 --> 00:28:26,159 Speaker 1: very tall structure and you only use concrete, you're asking 455 00:28:26,200 --> 00:28:30,040 Speaker 1: for trouble because something like really high winds or an 456 00:28:30,040 --> 00:28:34,280 Speaker 1: earthquake could cause monumental damage and even total collapse. But 457 00:28:34,440 --> 00:28:36,359 Speaker 1: fortunately we have a lot of people to thank for 458 00:28:36,440 --> 00:28:40,440 Speaker 1: creating more resilient ways to use concrete. One of those 459 00:28:40,480 --> 00:28:45,320 Speaker 1: people was a nineteenth century gardener in France named Joseph Monnier. 460 00:28:45,960 --> 00:28:49,440 Speaker 1: He wanted to create a more durable flower pot. Then 461 00:28:49,480 --> 00:28:52,719 Speaker 1: he began to experiment with concrete set around an iron 462 00:28:52,920 --> 00:28:58,120 Speaker 1: mesh frame. He created iron reinforced concrete or ferro concrete. 463 00:28:58,480 --> 00:29:02,000 Speaker 1: A lot of other people would build literally upon that idea, 464 00:29:02,440 --> 00:29:05,440 Speaker 1: giving us stuff like the lovely rebar that gives more 465 00:29:05,480 --> 00:29:10,560 Speaker 1: tensile strength to concrete. So concrete is really handy stuff. 466 00:29:10,600 --> 00:29:14,080 Speaker 1: It's one of the big innovations that has supported urbanization 467 00:29:14,200 --> 00:29:18,000 Speaker 1: and industrialization. So it is not easy to say we 468 00:29:18,000 --> 00:29:21,960 Speaker 1: should give up on concrete due to carbon emissions. However, 469 00:29:22,280 --> 00:29:26,600 Speaker 1: at the same time, humans are producing a lot of cement. 470 00:29:27,120 --> 00:29:30,480 Speaker 1: In twenty the estimated global production was around four point 471 00:29:30,520 --> 00:29:33,600 Speaker 1: one billion tons of the stuff, and every ton of 472 00:29:33,640 --> 00:29:37,920 Speaker 1: cement creates nine ms of c O two emissions, which 473 00:29:38,000 --> 00:29:42,720 Speaker 1: is around one four pounds of carbon dioxide per ton 474 00:29:42,960 --> 00:29:47,040 Speaker 1: of cement. So that would mean in cement production dumped 475 00:29:47,080 --> 00:29:51,960 Speaker 1: around three point seven trillion ms or eight trillion pounds 476 00:29:51,960 --> 00:29:55,360 Speaker 1: of c O two into the atmosphere. And again that's 477 00:29:55,400 --> 00:29:58,720 Speaker 1: just figuring in the production of cement, not the transportation 478 00:29:58,840 --> 00:30:02,160 Speaker 1: or anything like that. And keep in mind might have 479 00:30:02,200 --> 00:30:05,560 Speaker 1: actually seen more cement production than we did had there 480 00:30:05,600 --> 00:30:08,960 Speaker 1: not been a pandemic. The four point one billion tons 481 00:30:09,000 --> 00:30:14,360 Speaker 1: figure has remained fairly consistent since around but back in 482 00:30:14,400 --> 00:30:18,320 Speaker 1: the industry actually produced an estimated four point two billion tons, 483 00:30:18,560 --> 00:30:20,680 Speaker 1: so we're not likely to see this number go down 484 00:30:20,800 --> 00:30:24,520 Speaker 1: anytime soon. And there are other parts of concrete production 485 00:30:24,640 --> 00:30:27,880 Speaker 1: that contribute to CEO two emissions, it's just that the 486 00:30:27,920 --> 00:30:33,040 Speaker 1: manufacturing of cement represents by far the largest contributor. All Right, 487 00:30:33,480 --> 00:30:35,840 Speaker 1: So we know that making concrete creates a lot of 488 00:30:35,880 --> 00:30:40,040 Speaker 1: carbon dioxide. We also know concrete is really important stuff, 489 00:30:40,160 --> 00:30:42,400 Speaker 1: and that it's not as easy as just walking away 490 00:30:42,440 --> 00:30:45,640 Speaker 1: from the material. When we come back, i'll talk about 491 00:30:45,760 --> 00:30:49,000 Speaker 1: those researchers who pumped c O two into concrete mix 492 00:30:49,400 --> 00:30:52,920 Speaker 1: and what that all actually means. But first let's take 493 00:30:53,280 --> 00:31:05,600 Speaker 1: a quick break. In two Matt made, the then governor 494 00:31:05,720 --> 00:31:08,920 Speaker 1: of the U. S State of Wyoming, issued a challenge. 495 00:31:09,280 --> 00:31:11,920 Speaker 1: It was a competition to find ways to convert carbon 496 00:31:11,960 --> 00:31:16,240 Speaker 1: dioxide emissions into sellable products. So, in other words, ways 497 00:31:16,320 --> 00:31:19,160 Speaker 1: to take something that is generally a negative, that is 498 00:31:19,200 --> 00:31:22,479 Speaker 1: the release of carbon dioxide, and to turn it into 499 00:31:22,560 --> 00:31:25,760 Speaker 1: a positive. Now, presumably the goal wasn't just to create 500 00:31:25,800 --> 00:31:29,000 Speaker 1: a product, but to lock c O two into some 501 00:31:29,200 --> 00:31:33,880 Speaker 1: other substance so that it wouldn't be part of the atmosphere. Now. 502 00:31:33,920 --> 00:31:36,400 Speaker 1: Me did this for a few different reasons. One big 503 00:31:36,440 --> 00:31:39,480 Speaker 1: one is that Wyoming has a coal industry. But obviously 504 00:31:39,800 --> 00:31:43,440 Speaker 1: coal is a fossil fuel, and burning coal releases c 505 00:31:43,640 --> 00:31:47,080 Speaker 1: O two, So the optics are not great for the 506 00:31:47,080 --> 00:31:50,080 Speaker 1: coal industry, and it's hard to get around this fact 507 00:31:50,440 --> 00:31:54,360 Speaker 1: that this particular industry contributes to climate change, and that 508 00:31:54,440 --> 00:31:56,560 Speaker 1: in turn poses a pretty big threat to our way 509 00:31:56,600 --> 00:31:59,680 Speaker 1: of life, which is perhaps the most understated way I 510 00:31:59,680 --> 00:32:02,560 Speaker 1: could have put that. So finding a way to capture 511 00:32:02,640 --> 00:32:05,320 Speaker 1: c O two and convert it into something else and 512 00:32:05,400 --> 00:32:09,600 Speaker 1: to make it a profitable endeavor would be a great solution. 513 00:32:10,160 --> 00:32:13,960 Speaker 1: One of the reasons carbon capture initiatives aren't exactly proliferating 514 00:32:13,960 --> 00:32:17,240 Speaker 1: all over the place is that they tend to be expensive, 515 00:32:17,600 --> 00:32:21,400 Speaker 1: and often the output isn't something you can monetize. So 516 00:32:21,440 --> 00:32:24,440 Speaker 1: it's not that we don't know how to capture carbon dioxide. 517 00:32:24,720 --> 00:32:27,239 Speaker 1: We've got lots of ways to do it. It's just 518 00:32:27,320 --> 00:32:29,480 Speaker 1: that we don't have a lot of ways to do 519 00:32:29,560 --> 00:32:33,959 Speaker 1: it that in turn generate revenue. They represent a cost. 520 00:32:34,120 --> 00:32:38,480 Speaker 1: So if you're literally pumping CEO two underground so that 521 00:32:39,000 --> 00:32:43,040 Speaker 1: it's essentially captured down beneath the ground, and you know 522 00:32:43,120 --> 00:32:45,200 Speaker 1: you're not making any money off that CEO two it's 523 00:32:45,240 --> 00:32:48,680 Speaker 1: just pumped down there, it's actually gonna cost you money 524 00:32:48,720 --> 00:32:52,320 Speaker 1: to move the CEO two down there. And businesses, by 525 00:32:52,360 --> 00:32:55,800 Speaker 1: and large, from what I understand, exists to make revenue. 526 00:32:55,880 --> 00:32:59,800 Speaker 1: So generally speaking, businesses don't tend to follow pathways that 527 00:33:00,200 --> 00:33:04,560 Speaker 1: two expenses if they can avoid it, and carbon capture 528 00:33:04,960 --> 00:33:08,840 Speaker 1: is expensive. But if you can create a product, Well, 529 00:33:09,040 --> 00:33:12,400 Speaker 1: then you can recapture those costs, and if the product 530 00:33:12,480 --> 00:33:15,960 Speaker 1: is good enough, as in popular enough and desirable enough, 531 00:33:16,000 --> 00:33:17,920 Speaker 1: you can actually make a profit off of it. And 532 00:33:17,960 --> 00:33:22,640 Speaker 1: now with a profitable plan for carbon capture, you can 533 00:33:22,760 --> 00:33:26,880 Speaker 1: kick things into a different gear. Now, what is environmentally 534 00:33:26,880 --> 00:33:31,800 Speaker 1: beneficial is also economically beneficial, at least in the short term. 535 00:33:31,880 --> 00:33:35,800 Speaker 1: And let me do a quick aside here. I want 536 00:33:35,840 --> 00:33:41,760 Speaker 1: to stress wholeheartedly that climate change mitigation is in fact 537 00:33:42,360 --> 00:33:46,840 Speaker 1: economically beneficial. It's just on a much longer timetable than 538 00:33:46,920 --> 00:33:51,400 Speaker 1: most businesses focus on. Businesses tend to look at fiscal 539 00:33:51,560 --> 00:33:56,040 Speaker 1: quarters or maybe a fiscal year, and mitigating climate change 540 00:33:56,240 --> 00:33:58,960 Speaker 1: on that kind of time scale doesn't seem to make 541 00:33:59,000 --> 00:34:03,120 Speaker 1: economic sense because of the expenses involved, and you're not 542 00:34:03,240 --> 00:34:08,040 Speaker 1: likely to see any kind of you know, results immediately. 543 00:34:08,480 --> 00:34:10,879 Speaker 1: But when you pull back and you take a much 544 00:34:11,000 --> 00:34:14,600 Speaker 1: longer term view, you see the climate change stands as 545 00:34:14,600 --> 00:34:18,360 Speaker 1: a threat to entire regions and industries, and you realize 546 00:34:18,360 --> 00:34:22,440 Speaker 1: that climate change mitigation is the best economic strategy in 547 00:34:22,480 --> 00:34:25,480 Speaker 1: the long term. It's just really hard to get stakeholders 548 00:34:25,520 --> 00:34:27,759 Speaker 1: to look that far out, as we tend to be 549 00:34:27,840 --> 00:34:31,400 Speaker 1: pretty short sighted when it comes to stuff like money 550 00:34:31,520 --> 00:34:33,919 Speaker 1: and lots of other things too. All right, let's get 551 00:34:33,960 --> 00:34:37,840 Speaker 1: back to this X Prize competition thing. Out of the 552 00:34:37,880 --> 00:34:40,920 Speaker 1: competition emerged a couple of teams with proposals for a 553 00:34:41,040 --> 00:34:44,680 Speaker 1: green concrete strategy, and both teams had shown that by 554 00:34:44,760 --> 00:34:49,680 Speaker 1: injecting carbon dioxide into the concrete production process, they can 555 00:34:49,760 --> 00:34:53,040 Speaker 1: both reduce the amount of CEO two that was released 556 00:34:53,560 --> 00:34:57,880 Speaker 1: and they can make concrete stronger. One team, called Carbon 557 00:34:57,960 --> 00:35:03,040 Speaker 1: Cure Technologies injected c O two into concrete wastewater, which 558 00:35:03,280 --> 00:35:06,440 Speaker 1: didn't turn it into some sort of carbonated beverage, but 559 00:35:06,560 --> 00:35:09,799 Speaker 1: rather created a mineral that, when added back into the 560 00:35:09,880 --> 00:35:14,120 Speaker 1: concrete mixture, made it stronger. The second team, you see 561 00:35:14,280 --> 00:35:17,920 Speaker 1: l a carbon Built, injected c O two into concrete 562 00:35:17,960 --> 00:35:21,400 Speaker 1: as it goes through the curing process. This approach reduced 563 00:35:21,400 --> 00:35:24,600 Speaker 1: the amount of carbon dioxide emissions from producing that concrete. 564 00:35:24,640 --> 00:35:29,160 Speaker 1: By now, that's just the production of that concrete, not 565 00:35:29,320 --> 00:35:33,320 Speaker 1: the cement that was used to make that concrete. Keeping 566 00:35:33,320 --> 00:35:36,479 Speaker 1: in mind that cement production is the real issue here. 567 00:35:36,800 --> 00:35:40,280 Speaker 1: The reduction in greenhouse gas from concrete production might seem 568 00:35:40,320 --> 00:35:43,040 Speaker 1: like a band aid on top of a very serious cut. 569 00:35:43,600 --> 00:35:48,000 Speaker 1: It's not nearly good enough. It's a reduction that is good, 570 00:35:48,480 --> 00:35:51,360 Speaker 1: but it's not eliminating the vast amounts of c O 571 00:35:51,480 --> 00:35:56,560 Speaker 1: two given off through cement production. The process does require 572 00:35:56,600 --> 00:35:59,240 Speaker 1: CEO two. That means that you could create carbon capture 573 00:35:59,280 --> 00:36:03,560 Speaker 1: systems and pair them with facilities like a cement production facility, 574 00:36:03,920 --> 00:36:07,040 Speaker 1: so the CEO two generated from cement production would go 575 00:36:07,160 --> 00:36:12,160 Speaker 1: toward making better concrete. But honestly, these facilities produce way 576 00:36:12,200 --> 00:36:15,600 Speaker 1: more carbon dioxide than you would need to produce green 577 00:36:15,719 --> 00:36:18,920 Speaker 1: concrete solutions. You would really need to build in capture 578 00:36:18,920 --> 00:36:23,759 Speaker 1: and sequestration facilities into cement production plants. But like I 579 00:36:23,800 --> 00:36:27,480 Speaker 1: said earlier, those solutions are expensive and they represent an 580 00:36:27,480 --> 00:36:31,360 Speaker 1: economic cost to the companies. It's possible for governments to 581 00:36:31,360 --> 00:36:35,280 Speaker 1: create incentives to reward companies for capturing and sequestering carbon, 582 00:36:35,760 --> 00:36:38,879 Speaker 1: but outside of that it's a tough sell, and even 583 00:36:38,960 --> 00:36:41,279 Speaker 1: the political approach is super difficult because there are a 584 00:36:41,320 --> 00:36:44,360 Speaker 1: lot of politicians who aren't exactly swayed by the science 585 00:36:44,400 --> 00:36:48,600 Speaker 1: of climate change. Meanwhile, there are engineers looking to find 586 00:36:48,640 --> 00:36:51,760 Speaker 1: ways to reduce the amount of carbon emissions released during 587 00:36:51,840 --> 00:36:55,959 Speaker 1: cement production, largely by fiddling with the formula. A big 588 00:36:56,000 --> 00:36:59,120 Speaker 1: source of the problem is that the materials in the 589 00:36:59,160 --> 00:37:01,600 Speaker 1: process of make cement have to be heated up to 590 00:37:01,719 --> 00:37:06,520 Speaker 1: around fifty degrees celsius or hotter to form clinker. Finding 591 00:37:06,520 --> 00:37:10,120 Speaker 1: alternatives to those materials that can react at lower temperatures 592 00:37:10,160 --> 00:37:12,600 Speaker 1: would release the amount of fossil fuels that you needed 593 00:37:12,760 --> 00:37:16,399 Speaker 1: for the process. Another solution is to look at byproducts 594 00:37:16,480 --> 00:37:20,720 Speaker 1: generated from other industries like fly ash and use those 595 00:37:20,760 --> 00:37:24,560 Speaker 1: as additives to reduce the amount of cement production that 596 00:37:24,600 --> 00:37:26,840 Speaker 1: you need in order to make concrete. So, in other words, 597 00:37:27,480 --> 00:37:29,359 Speaker 1: if you are using fly ash to make up some 598 00:37:29,440 --> 00:37:32,319 Speaker 1: of the weight of the cement, you don't need as 599 00:37:32,400 --> 00:37:34,640 Speaker 1: much cement to make concrete, and as long as the 600 00:37:34,719 --> 00:37:39,120 Speaker 1: finished product is as good or better than existing concrete, 601 00:37:39,200 --> 00:37:42,239 Speaker 1: your golden Now. I also didn't really cover this, but 602 00:37:42,320 --> 00:37:46,439 Speaker 1: with the hydraulic nature of concrete the need for hydration, 603 00:37:46,680 --> 00:37:49,759 Speaker 1: there's also a big need for water. In fact, the 604 00:37:49,840 --> 00:37:54,000 Speaker 1: concrete industry takes up nearly ten of industrial water use 605 00:37:54,400 --> 00:37:57,960 Speaker 1: and nearly one point seven percent of total global water use. 606 00:37:58,320 --> 00:38:01,880 Speaker 1: So not only is it dumping CEO two in the atmosphere, 607 00:38:02,120 --> 00:38:04,880 Speaker 1: it's using up a significant amount of water and in 608 00:38:04,920 --> 00:38:07,600 Speaker 1: some areas of the world that might not be a 609 00:38:07,719 --> 00:38:10,160 Speaker 1: huge deal. But for other areas that are affected by 610 00:38:10,160 --> 00:38:14,080 Speaker 1: water shortages and droughts and have a need to lay 611 00:38:14,080 --> 00:38:17,280 Speaker 1: a lot of concrete to build up their their infrastructure, 612 00:38:17,600 --> 00:38:20,960 Speaker 1: that's a huge problem. Water resources are precious, I mean, 613 00:38:21,000 --> 00:38:25,440 Speaker 1: wars are fought over them, and an industry as thirsty 614 00:38:25,560 --> 00:38:29,680 Speaker 1: as concrete production adds more pressure. One thing I wanted 615 00:38:29,719 --> 00:38:33,640 Speaker 1: to close on was a cool technology that uses cement 616 00:38:33,800 --> 00:38:38,200 Speaker 1: products similar to concrete as an ink in a three 617 00:38:38,320 --> 00:38:42,960 Speaker 1: D printing application. These companies are using enormous three D 618 00:38:43,080 --> 00:38:46,200 Speaker 1: printers to print buildings, and there are actually a few 619 00:38:46,200 --> 00:38:49,480 Speaker 1: different companies doing this. One of them is called icon 620 00:38:50,239 --> 00:38:53,640 Speaker 1: Icon has a large industrial three D printer called the 621 00:38:53,760 --> 00:38:58,120 Speaker 1: Vulcan two, which uses a cement based building material which 622 00:38:58,120 --> 00:39:02,080 Speaker 1: the company calls lava crete as the ink. So with 623 00:39:02,120 --> 00:39:05,880 Speaker 1: the Vulcan Too, it's possible to print out a single 624 00:39:05,960 --> 00:39:09,880 Speaker 1: story building. The Vulcan too can print walls that stand 625 00:39:09,920 --> 00:39:12,080 Speaker 1: at a maximum of eight and a half feet tall, 626 00:39:12,560 --> 00:39:15,719 Speaker 1: and the printer is thirty three ft wide and can 627 00:39:15,800 --> 00:39:19,640 Speaker 1: print on a foundation that's up to twenty eight feet wide. However, 628 00:39:19,640 --> 00:39:23,000 Speaker 1: the Vulcan can also move down the length of a 629 00:39:23,320 --> 00:39:27,480 Speaker 1: structure as it builds it and there's no real maximum 630 00:39:27,600 --> 00:39:31,280 Speaker 1: length that you would have, like you could in theory 631 00:39:31,400 --> 00:39:33,279 Speaker 1: build it as long as you wanted it to be. 632 00:39:33,719 --> 00:39:36,720 Speaker 1: It would always be at max. Twenty eight feet wide, 633 00:39:36,800 --> 00:39:39,280 Speaker 1: but it could be as long as you needed, assuming 634 00:39:39,320 --> 00:39:41,880 Speaker 1: you had the materials and the land, like the level 635 00:39:42,040 --> 00:39:46,000 Speaker 1: space to build upon. The printer pushes out the mixture 636 00:39:46,040 --> 00:39:48,960 Speaker 1: at a rate of around five to seven inches of 637 00:39:49,080 --> 00:39:54,520 Speaker 1: wall length per second, which yeah, that's really fast. So 638 00:39:54,719 --> 00:39:58,040 Speaker 1: by laying down lines of this lava creet each line 639 00:39:58,120 --> 00:40:02,439 Speaker 1: is about an inch tall, then you can lay out 640 00:40:02,480 --> 00:40:05,920 Speaker 1: the outline of your wall structure, and then you start 641 00:40:05,920 --> 00:40:09,560 Speaker 1: putting on the second layer. Each layer binds with one 642 00:40:09,719 --> 00:40:13,520 Speaker 1: underneath it, and so then the volcantuo can print a building, 643 00:40:13,600 --> 00:40:15,840 Speaker 1: or at least the walls, you know, the internal and 644 00:40:15,920 --> 00:40:18,839 Speaker 1: external walls of a building. You would still have to 645 00:40:18,920 --> 00:40:22,840 Speaker 1: provide the finishing touches, you know, stuff like doors and 646 00:40:22,840 --> 00:40:25,160 Speaker 1: and a roof and ceiling and that kind of thing. 647 00:40:25,560 --> 00:40:28,640 Speaker 1: But this mixture has the special binding agents in it 648 00:40:28,760 --> 00:40:32,200 Speaker 1: so that they do hold together. And using that approach, 649 00:40:32,200 --> 00:40:34,240 Speaker 1: it's possible to build a house out of a concrete 650 00:40:34,320 --> 00:40:37,840 Speaker 1: like material within a day or two, depending on the 651 00:40:37,840 --> 00:40:41,360 Speaker 1: size of the building. The rapid approach to building durable 652 00:40:41,440 --> 00:40:44,560 Speaker 1: homes could be a huge game changer and help communities 653 00:40:44,560 --> 00:40:48,840 Speaker 1: address problems like homelessness or creating housing in the wake 654 00:40:48,960 --> 00:40:52,880 Speaker 1: of a natural disaster. It's the plasticity of the liquid 655 00:40:52,960 --> 00:40:55,040 Speaker 1: form of the material that makes it really possible to 656 00:40:55,040 --> 00:40:58,120 Speaker 1: go through a three D printer device, and the curing 657 00:40:58,160 --> 00:41:02,319 Speaker 1: process makes it a practical structural material. And I have 658 00:41:02,400 --> 00:41:06,000 Speaker 1: to emit these are really interesting technologies that could serve 659 00:41:06,239 --> 00:41:08,919 Speaker 1: as a huge benefit if put to the right use. 660 00:41:09,640 --> 00:41:12,920 Speaker 1: That's a big if. However, it requires people to spearhead 661 00:41:12,960 --> 00:41:16,640 Speaker 1: projects that aim for these goals, and of course that 662 00:41:16,680 --> 00:41:19,960 Speaker 1: does not change the fact that cement production is still 663 00:41:20,000 --> 00:41:24,360 Speaker 1: an environmentally costly process. We shouldn't forget that while cement 664 00:41:24,400 --> 00:41:28,040 Speaker 1: production is a big contributor to greenhouse gas emissions, it 665 00:41:28,160 --> 00:41:32,840 Speaker 1: is also not the largest contributor. Transportation tends to be 666 00:41:33,000 --> 00:41:36,839 Speaker 1: the biggest one, followed by electricity production. And so while 667 00:41:36,880 --> 00:41:40,000 Speaker 1: it's important that we address issues with carbon emissions from 668 00:41:40,160 --> 00:41:45,440 Speaker 1: cement and concrete production, we can't focus solely on that issue. 669 00:41:45,680 --> 00:41:48,400 Speaker 1: If we quote unquote solved it, we would still have 670 00:41:48,480 --> 00:41:50,239 Speaker 1: a lot of work to do. So if we just 671 00:41:50,440 --> 00:41:53,040 Speaker 1: look at one thing, that ends up creating a false 672 00:41:53,120 --> 00:41:56,080 Speaker 1: sense of achievement whenever we make any sort of progress, 673 00:41:56,560 --> 00:41:59,080 Speaker 1: and meanwhile, we continue to dump tons of CEO two 674 00:41:59,080 --> 00:42:02,600 Speaker 1: into the atmosphere. The quest to create green concrete and 675 00:42:02,680 --> 00:42:05,560 Speaker 1: cement has to be part of our approach to climate 676 00:42:05,640 --> 00:42:10,040 Speaker 1: change mitigation, but it can't be the only part of it. Well, 677 00:42:10,080 --> 00:42:12,520 Speaker 1: that wraps up this episode of text Stuff and our 678 00:42:12,640 --> 00:42:16,000 Speaker 1: look at concrete. There's obviously a lot more we could say. 679 00:42:16,160 --> 00:42:18,880 Speaker 1: I didn't really go into the various additives that have 680 00:42:18,960 --> 00:42:23,400 Speaker 1: been developed over the years to change the the the 681 00:42:23,480 --> 00:42:27,280 Speaker 1: qualities of concrete, but that would require a much deeper 682 00:42:27,320 --> 00:42:31,280 Speaker 1: dive into chemistry. And y'all know, when I started getting 683 00:42:31,320 --> 00:42:34,600 Speaker 1: lots of letters and numbers together, my eyes begin to 684 00:42:35,080 --> 00:42:37,799 Speaker 1: glaze over. So we're gonna leave it here for now. 685 00:42:37,840 --> 00:42:40,560 Speaker 1: But if you have suggestions for future topics of tech stuff, 686 00:42:40,600 --> 00:42:43,120 Speaker 1: reach out to me. The best way is over on Twitter. 687 00:42:43,560 --> 00:42:47,640 Speaker 1: The handle for the show is text Stuff HSW and 688 00:42:47,680 --> 00:42:55,640 Speaker 1: I'll talk to you again really suit. Text Stuff is 689 00:42:55,640 --> 00:42:58,759 Speaker 1: an I Heart Radio production. For more podcasts from my 690 00:42:58,920 --> 00:43:02,520 Speaker 1: Heart Radio, this at the i Heart Radio app, Apple Podcasts, 691 00:43:02,640 --> 00:43:09,000 Speaker 1: or wherever you listen to your favorite shows. H