Everything Everywhere Daily: History, Science, Geography & More - Roman Concrete

Episode Date: December 9, 2020

There are lots of stories about lost technologies and techniques of the ancients which have been lost to us through history. In reality, most things were figured out independently by modern people, and we have better modern versions of almost everything the ancients had, including things like Damascus Steel. That is, except for one thing. Learn more about Roman Concrete, the stuff which has lasted over 2,000 years, on this episode of Everything Everywhere Daily. Learn more about your ad choices. Visit megaphone.fm/adchoices

There are lots of stories about technologies and knowledge from ancient peoples that have been lost to us through history. In reality, most of those things that were lost have been figured out independently by modern people, and we have better modern versions of almost everything the ancients had, including things like Damascus Steel. That is except for one thing. Learn more about Roman concrete, the stuff which has lasted over 2,000 years, on this episode of Everything Everywhere Daily. Fear is the virus is trending on TikTok. Vaccines are poison. Then your yoga teacher says that sex traffic children are being sacrificed by satanic liberals.

But it's all okay. The great awakening is coming. What is happening? Every week on Conspiratuality Podcast, we explore the fever dreams that suck friends, family, and wellness gurus down the right-wing cult spiral in a search for salvation. This episode is sponsored by Skillshare. Back in the ancient world, if you wanted to learn a skill, you'd have to spend years learning your trade from a master. Today, we have Skillshare, which can help you get up to speed quickly.

They have videos on almost every subject you can imagine, including things like designing your own furniture, milling your own lumber, and how to put shingles on your house. With Skillshare premium, you can have unlimited access to everything for as low as 825 per month. Go to everything-dash-everywhere.com slash Skillshare to get a free two-week trial of Skillshare Premium membership, or just click on the link in the show notes. Before you decide to skip this episode, because you think the idea of talking about concrete is boring, realize this.

For most of you listening to this podcast right now, there's probably concrete somewhere around you. If you're listening in a car, there's concrete on the road. If you're walking, there might be concrete on the sidewalk. And if you're in a building, there's probably concrete in the foundation or maybe the walls. Concrete might not get a lot of attention, but it's really important stuff. modern civilization wouldn't be possible without it. While the Romans were great engineers and builders, they weren't really great innovators.

Despite existing for centuries, the Romans can't really be said to have left us with much in the way of technical advancement. Many of the things that they're best known for, such as Aqueducts, weren't actually Roman innovations. They got them from other civilizations, such as the Etruscans. However, there was one thing that they had that no one else has been able to figure out or reverse engineer for over 2,000 years. Roman concrete. The Latin word for it was opus camenticium, and it was a particular blend that was used to create many of the structures which are still standing, and in some cases are in use, today. We should start our discussion with the difference between concrete and cement. The two terms are often used interchangeably today, but they are different things. Concrete is a mix of aggregate

such as rocks or sand and a paste. Cement is an ingredient in concrete and is part of the of the paste. Cement, which in its modern form is called Portland cement, usually has a base made out of lime and is mixed with water to create the paste which holds together the aggregate in concrete. Today, there are different types of concrete depending on what your needs are. There is concrete that will dry fast, concrete that can harden underwater, and concretes with different load-bearing properties. So what was so special about Roman concrete? Basically, it was really durable. Modern concrete is pretty good, but over time, microfisures will develop. develop, those will expand, and over the decades the concrete will crumble. You've probably seen

examples of crumbling concrete at some point, be it on a building, road, or a bridge. Roman concrete didn't do that, at least not easily. If you go and visit Rome, the dome over the Pantheon and the triumphal arches you'll find in the forum are almost in perfect condition. Whereas many other structures have fallen down from earthquakes over the last two millennia, many of the structures which have stood are made out of Roman concrete. What was even more impressive, was how it worked in seawater. Concrete tends to decay much faster in seawater than on land. However, Roman concrete didn't suffer from this.

In fact, it got stronger the longer it was in seawater, which is totally counterintuitive. Probably the best preserved Roman concrete used in seawater can be found in the ancient port city of Caesarea in Israel. Built by Hare the Great, the breakwaters used in its harbor, are still intact today over 2,000 years since its construction. Pliny the Elder wrote in his book Naturalis Historia around the year 79, that Roman concrete, quote, as soon as it comes into contact with the waves of the sea and is submerged, becomes a single stone mass impregnable to waves and every day stronger, unquote.

So, Roman concrete is pretty amazing stuff. So what do we know about it exactly, and what makes it so good, and why were we unable to make it for so long? The answer to the last question is we lost the recipe. The vast majority of knowledge which was written down in antiquity has been lost, and much of the common knowledge which might have been used by tradespeople may never have been written down. The great Roman architect Vitruvius wrote down what little we know about Roman concrete. His treatise, 10 books on architecture, is really the only surviving text on architecture and building from the ancient world and spells out the basic ingredients of Roman concrete.

There were three components to Roman concrete. Lime, an aggregate, which was usually rocks, and the third was something called Pozalana, which is a volcanic ash that comes from a particular spot near Naples. This specific ash was the key to Roman concrete. Before, when I mentioned the harbor at Caesarea, Herod the Great imported 44 shiploads of Pozalana at 400 tons per shipload to complete the project.

So, believe it or not, much of the Roman success in building came from the fact that they just happened to live next to the perfect material for concrete. The recipes they developed over time were through trial and error. Those specific recipes are what's been lost in time. What the Romans didn't know was why it worked. Thankfully, modern researchers have figured out what made Roman concrete work so well, especially in seawater. Normally, when microfisures develop in concrete,

it's the start of the process which will eventually lead to its destruction. Over time, the fissures get larger, and at some point the concrete will start to crumble. In seawater, this process is accelerated. However, the unique mixture of Roman concrete in seawater causes something else to happen. When water enters the microfisures in the concrete, it stimulates the creation of a mineral called aluminum tober morite. This mineral grows and fills in the gaps in the concrete, making the structure harder and more solid over time. aluminum tobermorite is actually a rather rare mineral that usually only forms at high temperatures.

But it also just so happens to slowly form over time with Roman concrete. As we're learning more about the secrets of Roman concrete, it might just hold the key to making better concrete today. It turns out that Roman cement used less lime than the Portland cement used today. This is important because cement production and the heating of lime is one of the largest emitters of CO2 on Earth. a more Roman-like concrete would actually require less energy. Moreover, a good substitute for the natural volcanic Pozalana found in Italy is fly ash from coal-burning power plants. We haven't reverse engineered the exact recipe of Roman concrete yet,

but we're getting close. By studying this 2,000-year-old concrete, we're unlocking its secrets, and we might use this information to recreate this ancient formula or maybe even make something better. Executive producer of Everything Everywhere Daily is James McAlla. Associate producer is Thor Thompson. Today's five-star review comes from Podcast Republic. Listener Abdullah writes,

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