Vitruvius, lime, and what “mixing” really means

7:04better than modern day concrete. Okay. So, the question is, >> how do you do that? >> Yeah. Yeah. Because we see it in superhero movies when they get the thingy or or uh the Foundation, the Apple TV show. Uh, one of the, spoiler alert, uh, one of the characters is this like sentient robot that's lived on forever and has like self-healing kind of >> and the Yeah, these Romans are doing it 2,000 years ago, right? So, it's like it's like what's going on? Okay, so we want to figure out how it is. The first clue comes from a guy named Vuvius. He actually wrote the first architecture book in the world back in 30 BC. It's called Day Architectura. um and he described a way of mixing the

7:46concrete. So, what you do is you take something called quick lime, which is just calcium oxide. That's something that you get when you um take limestone, you heat it up. Limestone is calcium carbonate. That's like a sedimentary rock that you get from, you know, millions of years of sedimentation from all of these ancient sea creatures with like sea shells. >> Okay? >> You pack up a bunch of seaells, you get limestone. You heat it up, you get quick lime, which is Cao, calcium oxide. >> Okay. >> Okay. And when you combine that in excess water over months, you get some stable form of lime putty. And that's the process that he described in his book, Architectura.

8:28>> Okay. >> Yeah. Okay. So the defects that they found whenever whenever you look at this Roman concrete in like super detail, you'll find these millimeter grain to centimeter grain defects of lime. It's like full lime. So it's like not fully mixed in. >> Okay. Okay. And it was just thought that like all of this all of this lime that's like not fully mixed in is is kind of a defect. Okay. Then in 2023, a paper from MIT comes out. Okay. This is from the Mesaich lab and this describes a new form of mixing. This is hot mixing. So in the previous one in Vuvius in his document that's 2,000

9:09years old. I mean the guy was there presumably. So he's describing how he saw the concrete being made. He said it's cold mixing which is >> this calcium oxide. >> Yeah. Which which is you get the you get the calcium oxide, you mix it with water and then you mix the other stuff. >> Okay. What the MIT guys are saying is no. Actually, what we do is we get the lime class. We get we get that lime. We don't mix it with water first. We mix it with volcanic ash and all of these other ingredients and then we put in the concrete. And that order >> is very important. Order operations. Yes. Because I told you in chemistry, chemistry, this is basically materials chemistry, right? And like it's like cooking. The order of operations is very

9:50very important. Okay. So, what the MIT 2023 paper says is that we're going to do hot mixing, which is mix the lime with the volcanic ash, mix it together, and then put in the water. Okay? And then these chunks of lime,