0:00 For every single person on Earth, we produce about three tons of concrete every year.0:06 It's true.0:07 It's the most consumed material in the world, right after water.0:12 We use twice as much concrete as all other building materials combined.0:18 Wow.0:18 You know, it's a perfect follow-up to last week, when we talked about those unseen currents that shape the world.0:27 Concrete feels like the most unseen of all.0:30 It’s literally the foundation we walk on, but we never think about it.0:36 Exactly.0:36 We see the building, not the stuff the building is made of.0:41 And its story is way, way older than most people think.0:45 I always think of it as, I don't know, a 20th-century thing.0:50 Skyscrapers, highways...0:52 that whole vibe.0:53 Right, but the earliest forms go back about 8,500 years.0:57 People in Mesopotamia were using primitive concrete-like floors.1:02 But, um, the civilization that really perfected it—the ones who made it a world-changing technology—were the Romans.1:12 Okay, so what did they figure out?1:14 They developed something called pozzolanic concrete.1:18 They took volcanic ash—specifically from around Mount Vesuvius—and mixed it with lime and seawater.1:26 Wait, seawater?1:27 I would think the salt would just corrode everything.1:31 You'd think so, but it actually triggered a chemical reaction that made the concrete incredibly durable and even waterproof.1:41 It's why they could build massive harbors and aqueducts.1:45 And it's why the Pantheon in Rome, which was built around 126 CE, still has its original, unreinforced concrete dome.1:55 It's 142 feet across and has survived almost two thousand years of earthquakes.2:01 That's… unbelievable.2:03 An unreinforced dome that big is still standing?2:06 So what happened?2:08 Did we just forget how to do it?2:10 We did.2:11 After the fall of the Roman Empire, the knowledge was just...2:15 lost.2:16 For centuries.2:17 So how do we get from a lost Roman super-material to the stuff we use today?2:23 It took until 1824.2:24 An English bricklayer named Joseph Aspdin patents something he calls Portland cement.2:31 He figured out that by heating a specific mix of crushed limestone and clay, he could create a really strong, really consistent hydraulic binder.2:42 And that’s the key ingredient for modern concrete.2:46 That's the key.2:48 It was a total game-changer.2:50 But there was one more piece to the puzzle.2:53 A few decades later, in the 1850s, a French gardener named Joseph Monier starts embedding iron rods into his concrete planters.3:03 Oh, rebar.3:04 Reinforced concrete.3:05 Exactly.3:06 Concrete is amazing under compression—when you squeeze it—but it's terrible under tension, when you pull it.3:15 The steel rebar handles the tension.3:17 That combination—Portland cement and steel reinforcement—is what allowed for everything we think of as modern.3:26 Taller buildings, longer bridges, all of it.3:29 So it’s not one invention, but this layering of two different technologies from the 19th century that really built the world we live in.3:40 It's a classic pattern.3:42 One innovation makes something possible, the next one makes it practical on a massive scale.3:49 Okay, so it’s indispensable.3:51 It's everywhere.3:53 But that scale has to come with a cost.3:56 I feel like all I hear about concrete now is its environmental footprint.4:01 And you're right to.4:03 The production of cement is responsible for about eight percent of the entire world's CO2 emissions.4:11 Eight percent?4:12 From just that one material?4:14 That is a staggering number.4:16 It is.4:17 And the problem is, uh, chemical.4:19 The process of making cement involves heating limestone to extreme temperatures, and that process itself releases huge amounts of carbon dioxide.4:31 It’s baked into the very chemistry that makes it so useful.4:35 So the thing that made it revolutionary is also the thing that makes it so destructive.4:42 That’s the paradox.4:44 That's the paradox we're living with.4:47 So...4:47 are we stuck?4:48 Is there a future for concrete that isn't so damaging?4:52 People are trying to find one.4:55 There are all sorts of innovations happening.4:58 "Green concrete" that uses recycled materials to reduce the carbon footprint is a big one.5:05 But then there's the more experimental stuff.5:09 Like what?5:09 Like self-healing concrete.5:12 They're embedding it with bacteria that, when a crack forms and water gets in, activates and produces limestone to fill the gap.5:22 You’re kidding me.5:23 Living concrete?5:24 Essentially.5:25 And then there's translucent concrete, which has optical fibers running through it, allowing light to pass through a solid wall.5:35 It completely defies what you think concrete can be.5:39 So this ancient, grey, boring material is...5:43 still evolving.5:44 It's strange to think of the stuff that built the Pantheon now potentially healing itself or lighting up a room.5:53 It’s the story of all foundational technologies, isn't it?5:57 The things we build our world on top of never really sit still.6:02 They're always quietly changing, right under our feet.
