Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World

by Mark Miodownik

The setting of concrete is, at its heart, an ingenious piece of chemistry, which has powdered rock as its active ingredient. Not every type of rock will work. If you want to make your own concrete you need some calcium carbonate, which is the main constituent of limestone, a rock formed from the compressed layers of living organisms over millions of years and then fused together by the heat and pressure of the movement of the Earth’s crust. You also need some rock containing silicate—silicate being a compound containing silicon and oxygen, and constituting roughly 90 percent of the Earth’s crust—for which some form of clay will do. Grinding these ingredients up and mixing them together with water won’t get you anywhere, unless you want to create a sludgy mud. In order to create within them the essential ingredient that will react with the water, you need to free them from their current chemical bonds. This is not easy. These bonds are extremely stable, which is why rocks do not easily dissolve or react with many things—on the contrary, they last for millions of years. The trick is to heat them to a temperature of about 1450°C. This is a temperature far exceeding that of an average wood or coal fire, which is between 600 and 800°C if it is glowing red or yellow hot. At 1450°C a fire will glow white hot, with no tinge of red or even yellow in the flames but instead a hint of blue. It is so bright it is unnerving and almost painful to look at. At these temperatures, rock star...