Quartz Obsession
ConcreteNovember 17, 2017
A solid start
You might think pre-Roman technologies would be irrelevant today—but you’d be wrong. Concrete created when Aristotle walked the planet is not that different from the stuff we produce now. The difference is that we use mind-boggling quantities of concrete today—enough to build more than 1,000 Hoover dams each year. Its use has touched almost everyone alive today.
However, there’s a problem: The key component of concrete is cement, and its production causes a lot of carbon emissions. The cement industry emits more than twice the amount of greenhouse gas as every airplane in the sky, combined.
Slowly but surely, the industry is coming to terms with its problems. Given the ubiquity of the material, the future of concrete will be key to the future of humanity. How will it stack up?
By the digits
4.2 trillion kg: Cement we consumed in 2016.
700 BCE: Oldest known use of concrete.
25: Unique chemicals found in a typical mixture of cement.
Matters of definition
What's the difference between concrete and cement?
If you’re in the construction industry, please shield your eyes 🙈: Many people think cement and concrete are the same thing. They’re not, but they do have a close relationship: Cement is the glue that holds all the components of concrete together. Generally, these components include a mixture of sand, gravel, and rocks.
Cement, which is made from heating limestone and clay in the presence of coal, is activated as soon as you add water. The chemical reaction produces calcium carbonate, an extraordinary adhesive. The concrete mixture starts as a goopy liquid that can be shaped any way we like, and then as the mixture dries, it becomes nearly as hard as rock.
Ancient wonders
Sheer strength
The Pantheon is one of the world’s oldest concrete buildings. It was built in 126 CE during the reign of the Roman emperor Augustus, and it still holds the record for the largest unreinforced concrete dome, without a metal structure to add strength.
The first mention of concrete in Roman text dates back to 30 BCE, when engineer and architect Vitruvius came up with a recipe: mix ash from volcanoes with lime (calcium oxide, not the fruit) and seawater. But nobody knows the exact recipe of this Roman concrete. It’s a point of great curiosity because their formulation still beats the modern stuff in its ability to resist the harsh conditions when exposed to salt water. (🐦 Tweet this!)
The advent of concrete goes back even further, perhaps as far as 12,000 years ago, which was before humans had even mastered agriculture. In fact, some experts theorize that the first use of concrete, in southeastern Turkey, marked the moment that human civilization as we know it began.
🎧 Listen up!
This fascinating episode of the podcast Surprisingly Awesome makes a compelling case that cement binds all of humanity together.
because bacteria!
Patch me up
Concrete structures can last awhile. But like any material, they get weaker with time, and we spend billions each year repairing concrete failures. Hendrik Jonkers of Delft University has a solution: self-healing concrete.
Jonkers has found a species of bacteria that, if given the right food, spits out the material that holds the components of concrete together. The bacteria can exist in a dormant state for more than 200 years. (See a video about this here.)
When the concrete develops cracks, water vapor enters and wakes up the dormant bacteria. The food they eat—calcium lactate—is already mixed into the concrete. Then they excrete calcium carbonate, which is the glue that holds cement, gravel, and sand together.
Jonkers says the bacteria should be able to fill cracks up to a centimeter wide. He hopes to also produce a liquid containing spores of bacteria and calcium lactate, which can enter existing concrete cracks and heal them.
Pop quiz
What ingredient should you NOT add to make concrete?
Rotten foodCarbon dioxideGranitePlastic
Correct. Go forth and construct civilization!
Incorrect. Chemistry isn't your forte.
If your inbox doesn’t support this quiz, find the solution at bottom of email.
Watch this!
How to build a concrete tent
A special material that infuses concrete components into a sheet of canvas can be used to construct a large concrete tent in hours. Once built, you can stand on top of it, hammer it, and even test out a blowtorch.
the disrupters
The quest for low-emissions cement
Modern concrete is a mixture of three main components: cement, sand or gravel, and water. To reduce concrete’s environmental footprint, we first need to look at the chemistry of cement.
You can make cement by throwing in any decent-quality limestone and some clay in a coal-fired kiln. Typically, the heat inside the kiln converts limestone, which is calcium carbonate (CaCO3), to lime, which is calcium oxide (CaO), while releasing CO2. The CO2 released in the process, along with the CO2 formed when burning fossil fuels for the energy needed to heat the kiln, is what makes cement’s carbon footprint so high.
Quartz recently visited a startup in New Jersey that’s looking to disrupt the cement industry. It has tweaked the chemistry of cement such that it produces 30% less carbon dioxide during the manufacturing process. Better still, unlike normal cement that becomes concrete when mixed with water, this new cement only becomes concrete when it absorbs carbon dioxide. Overall, the total reductions in emissions come to about 60% compared to industry-standard Portland cement.
🌍 Quartz is running a series called The Race to Zero Emissions that discusses low-emissions technologies. Sign up here to be the first to know when stories are published.
Take me down this 🐰🕳
“Concrete doesn’t have to be brutal. These concrete homes and apartment buildings show that concrete doors, walls, floors—even headboards!—can be stylish and cozy,” or so says this soothing Pinterest gallery.
Poll
How will you bring up concrete at your next dinner party?
Click here to vote
I have lots of concrete ideas50 Shades of Grey (Concrete)Could it be used as a murder weapon?
THE FINE PRINT
In yesterday’s email about earcons, 32% of you voted for the Mac startup chime as your favorite.
Today’s email was written by Akshat Rathi.
Images: Reuters/Daniel Becerril (concrete truck), Reuters/Scanpix/Bertil Ericson (skate park), Reuters/Kerek Wongsa (concrete pour)
😴 sleep on this!
In tomorrow’s email, we’ll mention a bug in the latest iPhone that doesn’t quite add up. Can you guess what it is? Reply or tweet @qz #obsessed.
The correct answer to the quiz is Rotten food.
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