Skip to main content

Concrete’s Role As A Building Block In History

By February 21, 2012November 16th, 2016Wayne Brothers
To listen to this article click here.


This is SCIENCE FRIDAY. I’m Ira Flatow. If you’re a regular listener to this program, you know that one of my favorite topics is concrete. I know it sounds weird. It is a fascinating material, though, with a fascinating history. It’s everywhere, right. We use it for buildings, bridges, dams, roads. In fact, concrete is used more than any other manmade material in the world.

Right, we all take it for granted. A few of us know about its creation and about its development. We like to watch it being poured, like to watch it, you know, being worked. But, you know, the story of concrete is one that spans thousands of years, has touched the lives of rulers, inventors and architects, both famous and infamous.

Even Thomas Edison once owned the biggest concrete plant in the world, actually makes cement. My next thought that was an important story to tell us, along with a dozen others, and hey, I couldn’t agree more with him. Robert Courland is a historian and author of “Concrete Planet: The Strange and Fascinating Story of the World’s Most Common Manmade Material.” He joins us from San Francisco. Welcome to SCIENCE FRIDAY.

ROBERT COURLAND: It’s good to be here, thank you.

FLATOW: You know, whenever – and I corrected myself, I think – whenever I talk about concrete, and I talk to civil engineers, they say don’t mix up concrete and cement. That’s actually sort of a pun because you have to mix up cement to make concrete. So tell us the difference, would you?

COURLAND: Yeah, concrete is actually the binder used – I should say cement is the binder used to create concrete. It only represents perhaps a third of the total. The rest is sand, water and rocks called aggregate. And so they’re mixed together, and you’ve got concrete as the result. So instead of referring to a cement patio, it’s more properly called a concrete patio.

FLATOW: And I know how I got to be interested in the story of cement and concrete. How did you get your interest to write this book here?

COURLAND: Well, I actually began toying with the idea about five years ago, and it’s so ubiquitous that it’s almost invisible, and yet most of us know very little about it. So as I began researching the topic, I found all these incredible stories, and I was particularly amazed to discover that some of the most interesting figures in history were instrumental in its pioneering uses and applications, such figures as the Emperor Hadrian, Thomas Edison, who you mentioned, and – the Roman Emperor Hadrian, the architect Frank Lloyd Wright and a host of others.

FLATOW: Let’s talk about some – you tell some great stories in your book “Concrete Planet.” Let’s talk about one my favorites, which – because I’ve been to Kajaria, King Herod’s great harbor in Judea there, Kajaria, and the story of how that was built.

COURLAND: Yeah, King Herod, in the first century BCE, wanted a harbor. He wanted to have a rich kingdom, and if you wanted to have a rich kingdom, you need a harbor like everyone else, like in Alexandria and Piraeus in Athens and so on.

Now, the way you usually go about it is you take it an already existing bay or inlet, and then you extend one of the promontories to make it more sheltered, and then you start creating the jetties and the wharves and so on.

But unfortunately, ancient Judea didn’t have any of those natural features, and the only way it could be build was using this relatively new substance that the Romans had, concrete. So you could create a huge wooden form and then dump the concrete in it, have it sink in place, and you’ve got a – the result is a giant block that, you know, no current’s going to move.

And they had very strong currents, which was another problem there in Judea, right off the coast. So they – now planning such a venture is one thing, but actually doing it is quite another. The logistics that went into it were just phenomenal, comparable to the Pyramids and in some ways even more complicated. You needed to cut down something like 200,000 trees to build the huge concrete forms and also to fuel the lime kilns that were necessary to make the lime to mix the concrete with.

The trouble was at that time, the Mediterranean Basin had been mostly denuded of large trees. So where were they going to get the wood? So with the help of Rome, they found the wood in Central Europe and shipped it down the Danube to the Black Sea and then from the Black Sea to the Mediterranean and on to Judea.

And that was a tremendous effort right there, but they also needed the volcanic soil, which was another important ingredient, and so to ship it from Mount Vesuvius, the area around Naples, they had to use the ancient equivalent of today’s supertankers, these huge ships.

And they loaded thousands of tons of volcanic soil onto these ships and took it on to Judea, and it was an incredible engineering construction effort. In fact, the reconstructions of the harbor show a very modern-looking facility. In fact, it was state-of-the-art at its time. It had these special channels that were only open at high tide to flush out the harbor so it wouldn’t silt up.

And it was the second-largest harbor in the world, the first one being Alexandria to the south.

FLATOW: And it’s interesting, if you go to Israel and look at it now, you can imagine what it looked like…

COURLAND: Yeah because in that part of the Mediterranean, you’ve got a lot of subsidence. So it’s now under about 30 meters of water. The coastline’s just sunk. And there’s also a major earthquake fault that runs alongside it, too. But for several hundred years, it was one of the best in the world.

FLATOW: Why is the Roman Coliseum – you call it in your book the gold standard of concrete.

COURLAND: Well, actually not necessarily the Coliseum. The use of concrete for the Coliseum was primarily as a foundation material. But the Romans – I call it the gold standard because the Romans really perfected the use of concrete. In fact, they used it for about two centuries before applying it to their major construction efforts.

So they knew what to do with it and what not to do with it, and some of these things were – we didn’t wake up to until the second half of the 20th century. For instance, they would compact the concrete. They would just ram it into the forms to remove all air cavities and so on. And that made a denser material.

They also used very little water. They used only enough water to make it malleable, and that also gave it a much longer life and prevented cracking. They also realized that concrete wasn’t fireproof. So they used brick to clad their concrete walls, particularly after the great fire of 64 AD, the one that took place while Nero was emperor.

So they really knew a lot about how to use it, and again, we’ve only woken up to these things in the last couple of decades.

FLATOW: In fact there was a whole era where concrete was sort of forgotten about. Isn’t there a large (unintelligible)…?

COURLAND: Well, yeah, after the fall of the Roman Empire, dozens of technologies were lost, and one of them was how to make concrete. And so over 1,000 years would pass before people began rediscovering it. And the major progress in developing concrete was in 18th-century Britain, 19th-century Britain. And it was there that we eventually got the equivalent of modern concrete, which is called Portland cement, and that’s the standard concrete we use today.

FLATOW: 1-800-989-8255 is our number. We’re talking about concrete with Robert Courland, author of the book “Concrete Planet: The Strange and Fascinating Story of the World’s Most Common Manmade Material.” Is it possible to imagine a world today without concrete, what it might look like?

COURLAND: Sure, it would look like the 19th century. You would have more buildings built of brick and wood. There would probably be more people in the building trades. You would – the roads probably wouldn’t be as good as they are today. You would have more potholes. So it would look very antiquated in our eyes, simply because concrete would be missing from the visual landscape.

FLATOW: 1-800-989-8255. Let’s go to the phones, to Trevor(ph) in Redlands, California. Hi, Trevor.

TREVOR: Hi there. Great subject. I share your passion. Both my brother and I designed and built our houses out of concrete, and, you know, the walls, the floors, kitchen counters, everything. It’s an amazingly versatile product, and we have very different style houses. You know, and you wouldn’t even know they’re all built out of concrete necessarily.

FLATOW: So it doesn’t look like there’s a fortress, that you’re living in, a fortress of concrete?

TREVOR: No, not at all. My house is very modern-looking house and his is – looks like a castle, actually. It’s quite beautiful – something you might find in the Mediterranean or something. And there’s also a lot of great ways, I know now, to help make it a little bit more green building material, like using fly ash in it. I even read an article a while back about using the waste from power plants to mix the raw materials to make cement. I’m wondering if you know anything about that.

COURLAND: Yes, use of fly ash is very important. The – one of the problems with concrete today is that it generates a tremendous amount of CO2. And that comes from these huge blast furnaces that are used to kiln the limestone to create lime. And also, the limestone itself gives off carbon dioxide as it’s being cooked. And so it’s second only – I think it’s third only to power plants and automobiles in its production of CO2. Now with fly ash, you’ve got something that’s already there. And it’s wonderful material because you can use it to substitute not only the – you mix it with the cement and – so you don’t need as much lime, and also you don’t need to use as much sand in the material as well. It’s really wonderful. They’re working, right now, on even better concretes that should be out in the next few years.

FLATOW: Good luck, Trevor. There’s a new…

COURLAND: And some of these are even carbon negative.

FLATOW: There’s a new project.

TREVOR: Great. Thanks.

FLATOW: Yeah, thanks for calling. 1-800-989-8255. Let’s go to Brandon in Ann Arbor. Hi, Brandon.

BRANDON: Hey, how are you there?

FLATOW: Hey there.

BRANDON: I’m a tester in Ann Arbor area, or one of the concrete testers. We check the air pressure, take cylinders and mold them and put them in the laboratory and test them. It’s pretty entertaining. It’s quality control, quality assurance type of job.

FLATOW: Testing concrete did you say?


BRANDON: Yeah. We test concrete, usually on the side of the interstates or wherever it may be. And I get in, get out, take the test and tell the contractor and the concrete company what they got.


COURLAND: Yeah, that was…

FLATOW: Have you ever tested any old concrete that’s still around?

BRANDON: Old concrete, yeah. I mean, you can do a coring in…

FLATOW: Like Roman roads and things?

BRANDON: …get some old concrete. Roman roads – well, I was going to say, you know, these Roman roads are a lot better than the ones we even have right now. They’re crumbling after, you know, 10, 20, years, I believe, with salt on them.

COURLAND: That’s right.

FLATOW: Yeah. Thanks for calling. 1-800-989-8255. When do they start first reinforcing all this rebar and stuff inside the concrete?

COURLAND: Well, they did experiments in France back in the early 19th century, but it really didn’t take off until a contractor here in San Francisco, by the name of Ernest Ransome, who invented modern rebar, and it was much superior to what they were using before, which was something called barrel bands. Barrel bands were made by the million feet every year to – encase the wooden barrels, used for everything from wine to nails and what have you. So there was lots of it around, but it wasn’t as good as a rebar, and that’s Ernest Ransom’s big contribution.

FLATOW: 1-800-989-8255 is our number. This is SCIENCE FRIDAY from NPR. I’m Ira Flatow here, talking with the author of “Concrete Planet,” Robert Courland. And we’re going to bring in another guest now, because the cement, as we’ve said, is an ingredient in concrete. And during production, cement emits billions of tons of greenhouse gas carbon dioxide, as Robert was talking about. Researchers around the world are trying to create a greener form of concrete. Dr. Peter Stemmerman, a mineralogist at the Karlsruhe Institute of Technology in Germany – he is one of the investors of Celitement, described in the environmentally – to be environmentally compatible. Welcome to SCIENCE FRIDAY. Tell us, why are more environmentally compatible.

DR. PETER STEMMERMAN: Well, hello, Ira. It’s – our – Celitement is produced with just about one-third of limestone. And the limestone and conventional cement production and in our product is calcined. And from the calcination of the limestone, the CO2 is emitted. And over the whole process, would just emit about 50 percent of CO2 and just made about 50 percent of the energy too.

FLATOW: So it’s – so when you say the word – it’s Celite. It’s light in carbon, Celitement is how you’ve – is how you let it know. And how available is it?

STEMMERMAN: We are producing it now in a pilot plant in Germany, but it’s – I think about three to four years away from the market.

FLATOW: And you think it will be – make a real dent, because there’s a lot of concrete and – don’t the Chinese make most of the concrete or the cement in the world?

STEMMERMAN: Yes. In fact, we have about 54 percent of the cement production nowadays in China. And, yes, it’s a long way to go, as you, for example, have to do standardization, which takes five to 10 years if you want to be in the mass market. You have to start somewhere. And I think in about 10 years maybe, we’re really deep inside the market and we will change the scene.

FLATOW: Mm-hmm. Well, we wish you good luck. And thank you for taking time to join us today.

STEMMERMAN: Thank you.

FLATOW: That was Dr. Peter Stemmerman. He’s a mineralogist at the Karlsruhe Institute of Technology in Germany. What do you think about the Celitement, Robert?

COURLAND: Well, it’s very interesting. First, you’ve got to make it, you know, commercially interesting. And since this cement requires less energy to manufacture, then it’s theoretically possible to produce a low-carbon cement at a competitive price. And so I’m very encouraged by that. They’re also working on cements in England and in California here, from Culcalera(ph). And these actually produce less CO2. It emits less CO2. Or actually, it takes less CO2 than it actually generates, and so it’s carbon negative. And, again, it’s not on the market yet, but they say that within a few years it will be.

FLATOW: We’re going to take a break and come back and talk lots more about one of my favorite topics, concrete, with the author of “Concrete Planet: The Strange and Fascinating Story of the World’s Most Common Man-Made Material” Robert Courland. When we come back, we’ll talk about – why did Thomas Edison own the biggest cement factory in the world? I mean, he’s got the light bulb, you know, right? He’s got the recording machines. He’s got all that kind of stuff. What is he doing with cement? Interesting story. We’ll be back with the answers, so stay with us. I’m Ira Flatow. This is SCIENCE FRIDAY from NPR.


FLATOW: You’re listening to SCIENCE Friday. I’m Ira Flatow. We’re talking with Robert Courland, author of “Concrete Planet.” And a lot of people have questions about the mythology, about concrete. I want to get to them in the few remaining minutes that we have. Let’s talk about first – Robert, let’s talk about some mythology that concrete cannot be – cannot catch fire or be burned.

COURLAND: Well, it can’t. It’s fire resistant. It’s very fire resistant. Try to ignite a block of concrete and you’ll have a lot of problems. But the myth was that concrete is fireproof. And that was – the early concrete industry, the first half of the 20th century really promoted concrete a lot, saying that it was fireproof, and it’s not. When it’s exposed to high temperatures, it begins to defoliate. That means it begins to crumble away. And that’s why traditional bread and pizza ovens are made of brick and not concrete. If they’re made of concrete, they’d fall apart.

So the myth that concrete was fireproof was pretty much exploded by the second half of the 20th century. It should have been realized much earlier, after the 1906 earthquake and fire, but since concrete advocates dominated the engineering commissions that were formed to look into the damage caused by that disaster, they fudged the data to make it look like concrete had done very well in the fire, when in fact, it performed horribly.

FLATOW: And let’s go to another question here, and it comes in: we have concrete roads that are 2,000 years old, but why has not reinforced concrete stood up to the test of time?

COURLAND: Well, the steel that’s in reinforced concrete, which gives it its tensile strength, also dooms the material to a very short lifespan. Steel-reinforced structures, particularly those exposed to the elements, like I say, for instance, a freeway bridge are – will eventually corrode. The rebar will eventually rust, and as it rusts, its diameter expands by something like four or five fold. And then it destroys the concrete around it while it is being destroyed by the rust. And so that’s why concrete structures only last between, say, 50 and 125 years because of rebar corrosion.

We’ve got substitute rebars that have been developed recently. Some are made of fiberglass, reinforced polymer, some carbon fiber – are really good – a very interesting rebar that was recently developed is made of bronze-aluminum. Now bronze-aluminum is about the same strength as the mild steel used in most rebar today. And it’s – it doesn’t have any corrosion issues. So technically – theoretically…

FLATOW: Mm-hmm.

COURLAND: …you could build a concrete structure – reinforced concrete structure with bronze-aluminum rebar. And it should last a very, very long time.

FLATOW: Is that – are these new materials actually being used, or are we just talking about them?

COURLAND: Bronze-aluminum right now, they are doing experiments with it, and it looks – based on the experimental evidence, it looks very, very good.

FLATOW: What about fiberglass or…

COURLAND: Fiberglass – yeah, fiberglass, reinforced polymer rebar is now being used, and it shows wonderful promise. And so we really need to stop building with steel reinforced concrete, because we just have to demolish and rebuild the structure every 75 – 100 years. And, you know, it’s ridiculous. We could build buildings that last as long as the Romans, but we’re not going to be able to do it with steel as part of the element.

FLATOW: Interesting. Let’s go to the phones. Bradley in Nashville. Hi, Bradley.

BRADLEY: Hi, Ira. You may have touched on this because I tuned it late. Would you ask Mr. Courland if he could comment on the composition and construction of the dome of the Pantheon, which was designed and constructed by Hadrian in 135 A.D.

FLATOW: Yeah, he talked about that.

COURLAND: Yes. The Pantheon is…

BRADLEY: OK. Sorry. I didn’t hear…

FLATOW: No. He hasn’t talked about it yet. Go – well, we’ll hear it now. Go ahead, please, Robert.

COURLAND: Yeah. The Pantheon is an amazing structure, and, unlike the Parthenon in Athens, the Pantheon in Rome is still in good shape. It’s been in continual use for 1,900 years. And it was probably designed by the Emperor Hadrian who was one of the most brilliant emperors ever to rule during the empire. And he was always fascinated by domes.

And when he was a young man, before he became emperor, a famed architect by the name of Apollodorus made fun of his fascination for domes, which Apollodorus called pumpkins.

So when Hadrian came to power, he decided to, you know, design a building with a pumpkin, the likes of which would amaze the world. And he did that with Pantheon. It’s so incredible that when people visit it for the first time, they often assume that the portico, the part of the temple, the front part, is Roman, but that the rotunda and the dome were added in the 19th or 20th centuries because it’s too modern looking. It’s vast. Its 143 feet across and it still remains the largest unreinforced concrete dome in the world. And it could have only been done with concrete because of the plastic qualities of concrete, the ability to, you know, form it into any shape you want.

FLATOW: And you’re saying that if it has been done with reinforced concrete like today, it would’ve been gone in 100 years.

COURLAND: If it has been built of reinforced concrete, it wouldn’t have survived the empire that build it.

FLATOW: Could we still build roads without reinforcing in them today? You mentioned about the other materials. Could you still build that.

COURLAND: And that’s very interesting because concrete, by itself, has tremendous compressive strength. So assuming that a, you know, road is well-bedded, so you’re not going to have any lateral displacements if cracking occurs, you should be able to do it without reinforcement. And there’s a – the oldest concrete street in the world is in Bellefontaine, Ohio, is built, I think, around 1890 and it’s in wonderful shape and it was built of unreinforced concrete.

They turned it into a pedestrian zone because they wanted to preserve the original concrete surface, but it’s – not only has it stood up well after well over a century, but it also has required far less maintenance that the other nearby roads. So we have an example of unreinforced – and the Romans, too, you know? They used unreinforced concrete and their creations are still with us today, like the Aileen(ph) Bridge in Rome. It bears the traffic of cars, not just oxcarts and people as it originally did, but, you know, it holds up pretty good loads.

FLATOW: All is this fascinating stuff, and I personally wanted to talk about concrete and cement all the time. Concrete — cement and water, I mean, which get together, you know, to make concrete. So two substances are my favorite stuff to talk about, and this book is terrific to read “Concrete Planet: The Strange and Fascinating Story of the World’s Most Common Man-made Material” Robert Courland, thank you for taking time to be with us today and…

COURLAND: Oh, thank you.