Pompeii evidence: dry pre-mix piles + intact quicklime

11:01>> And this is the paper, an unfinished Pompean construction site. >> Okay. >> Okay. That's the key. >> Okay. >> Pompei is the key. >> Okay. >> Okay. I went to Pompei um I think it was two years ago. I actually that's I did go I did go to Pompe go to Pompei. Isn't it incredible? Yeah. Pompei is um >> an intact Roman city. It's >> that has been buried under a volcanic eruption. Mount Vuvius erupted in 79 AD >> and it buried an entire volcanic city in moments in just like you know within within

11:44within a few hours. And when you say city, it's, you know, particularly for the time, it is so [snorts] unbelievably large. >> Yeah. >> And organized and choreographed. It's like hard. >> It's It was a really surreal and bizarre feeling being like, "Oh, that street goes all the way over there and this one goes all the way over here." And it's a grid system. It's really impressive. >> Yeah. And there's a shopping district and there's like intact restaurants >> and you can you can you can tell what the function was because it looks just like >> today. Yeah. Yeah. There's a mall. >> Yeah. >> You know, it's insane when you think

12:25about it. Right. >> It is. >> And the advantage of studying a site like Pompei >> Yeah. >> is that >> what you've got is a city that was 2,000 years old. um one of the you know beach cities of the Roman Empire and it's frozen in time >> and just like every other city >> there's going to be construction sites. >> Okay. >> Okay. You see you see what's happening. So if there's a construction site you can go and look Yep. >> and see how they were mixing the concrete. >> Yes. >> That's the key. >> Yes. We can see how the sausage was made. >> Exactly. >> Uh because much like in all as all time periods in human history, we're always building something. >> Yeah.

13:05>> Exactly. and and you know that like they're renovating a building or they're building a new building or something like that. So they found a construction site and that's the focus of this paper. >> Okay. Got it. >> Okay. They found an active construction site >> and what they found was the dry premixed piles. >> So not lime that's been sitting in water and cold mixing, >> but actually lime that's been put and mixed with volcanic ash. >> Okay. >> And then it's waiting to be mixed with water. >> Ah, okay. Okay. Got it. Got it. Got it. Got it. >> And the reason why this matters chemically, right? We want to talk about like what what's what's the difference between the hot mixing and the cold mixing. >> Yeah. Like I you know, and I can kind of

13:46maybe into it a little bit, but it seems to be really fundamental. >> Yes, it is. It is very fundamental. So the idea is whenever water reacts with um calcium oxide, it gives off a lot of heat. >> Okay. Okay. That's the hot mixing part. Okay. Okay. Now, if you do it the way Vuvius said all those years ago in that book, then you take the lime, you mix it with the water, and because it takes such a long time, the the heat is just going to dissipate into the water. And so that's the cold mixing. >> If you do it when it's hot, right, you do it when it's hot, then you've got a mixture of the lime and the

14:26volcanic ash that you're mixing together, that's going to give off a lot of heat. there's gonna it's going to reach temperatures nearing 200 degrees C. Okay? And in that chemical reaction, what's going to end up happening is it's gonna sort of plaster everything together and that's actually going to preserve chunks of lime before they fully dissolve. >> I see. >> Into the rest of the mixture. >> I see. I see. So there there's sort of this this timing this this timing function where there's a window where it can solidify prior to distribution. >> Yes. >> But only at certain temperatures. >> Got it. >> Exactly. Yeah. And and because it's

15:07happening so fast, the the chunks of lime don't have enough time to really diffuse and become part of a homogeneous mixture. And so having these grains of lime in your concrete is actually a good idea. I see. >> Okay. >> Okay. Okay. >> And the reason for that >> I was gonna say Okay. Yes. >> Yeah. And and the reason for that we're gonna we're gonna sort of get into a little bit later, right? >> That's actually key to the the self um healing process. >> This kind of random distribution of this lime inside the mixture that solidifies >> in this case at high temperature prior to it all kind of getting distributed

15:48like into a muck. allow has some derivative effects that create uh favorable outcomes. Exactly. From a construction perspective. >> Yeah. Yeah. From a construction perspective. Right. So they found these dry mix piles and they're like, "Okay, this is this is great. That means that, you know, we were kind of right in that there's lime mixed with volcanic ash and it's dry. It's not in the form of the the concrete." Okay, let's let's look at some of the the smoking gun microructure that they found. Okay. When they looked at the unfinished walls and then they looked at the raw material, what you see is this really brittle micro structure where you're getting like the the you're

16:28getting chunks of lime, you're getting microscopic bits of volcanic ash and the two are exactly the same. Meaning the raw material and the unfinished walls, >> the walls that have just been created, >> right? Unfinished means there's no plaster, which means it was just done. >> Yes. Those have the same material properties. >> So, so this is again helping to verify the the the hypothesis that it is unfinished. >> Yes. >> Cuz when you look at it when it's really small, the structure of it matches because if it was finished, the fundamental that microruct Yeah. Well, no, hold on. The unfinished the fact that it's an unfinished wall means that it's very recently been made.

17:09>> Gotcha. >> Okay. Yes. And and so what that means is that that construction happened from this pile. >> I see what you're saying. You see what I'm saying? Yeah. It didn't have because because over time because >> Yeah. Because finished means that they put a plaster on it and then like now this the wall is smooth. Like if you've been to inside the Pompei buildings, there's like paintings and stuff like that. This is a new wall, right? And the raw material is right there. So you can you can connect those two and be like this >> was going to go become that. >> Yeah. I got you. >> You know what I mean? and it's right next to each other. And because the micro structure is exactly the same, you can say that actually, yeah, they did dry mix and then and then do the and then do the hot mixing and then and then make that wall.

17:49>> Right. That's the idea. >> Got it. >> Okay. [snorts] Um the other the other