Cement is not as simple as it looks. It is made of sand, lime, and limestone mixed into a slurry and then left to set and harden. It is a marvel of efficiency – making an incredibly versatile and durable material out of the most basic ingredients.
It doesn’t just hold buildings up; it holds up the Earth itself, forming the foundation on which we all stand. Cement is ubiquitous, but few people think about how it is made or what goes into making it.
Cement’s versatility comes from its ability to bond materials together that would otherwise separate in water. In fact, cement is just so effective at holding materials together that you can make it out of anything: wood pulp, plastics, even paper pulp or straw…
9 Things You Didn’t Know About Cement: A blog about how cement is made and some of its important uses.
Cement is the primary ingredient in concrete. It makes up about 80 percent of concrete and is used in hundreds of products, from buildings to flooring to highways. Cement is one of the oldest inventions and lies at the heart of many historical achievements. The concept of cement dates back to around 4000 B.C., when people realized that rocks could be made into bricks.
The first invention was simple: people mixed sand, clay and water together to form a paste composed primarily of sand. The paste was then shaped into bricks, which were later baked at low temperatures inside kilns or ovens. That turned out to be very effective for making bricks (although baking bricks made them brittle), but it left a lot of clay behind in the kilns, where it kept clogging up the air filters, causing fires and ruining the whole batch.
In the ancient world, cement wasn’t a new invention. People have been mixing sand and lime together for millennia. But during the industrial revolution, when larger and larger molds were becoming more important, it became clear that the traditional method wasn’t working very well.
At first they tried to improve the mixture by adding binding agents: egg, fat, or even just vinegar. But these were unsatisfactory; they weren’t cheap enough, and changing them was difficult. Then someone discovered that a type of clay known as kaolin had some of the qualities of binding agents and was cheap enough. They mixed it with sand and lime and made a paste which worked much better
Cement, the ubiquitous ingredient in concrete (and a key component in many other kinds of building material), is an unlikely story. It’s not made by mixing lime with hot water and then adding sand, as you might expect.
To make cement, a mix of calcium carbonate (limestone) and clay is heated in a kiln. The lime reacts with the carbonate to form calcium oxide and water, which is then released as carbon dioxide. The clay is also reduced to a powder and mixed with this slurry to produce what’s called “slag”.
The mixture is then cooled and ground into a fine powder. This final product can be used directly for concrete or it can first be used as a flux to bind the ingredients together; it’s also added to the mix for cement that’s used in mortar.
Cement is a product that uses only natural ingredients, and it has been in use since paleolithic times. Cement was invented in ancient Egypt as a binding material for stone tools.
Cement is invented. It’s not natural. It’s a mixture of limestone, clay and other materials that can harden into something solid if you bake it in the right way. The recipe varies, but the basic ingredients are usually limestone, clay and water.
And yet its manufacture wasn’t discovered until 1824: Georges Cuvier first wrote about cement in his book “Analyse des Terres”, published in 1824. He named it after the Greek word for earth (kome), which he said was the first substance that could be cemented into a solid mass by mixing it with lime or chalk.
Cement is a key ingredient in concrete, and the basis for many other products, such as ceramic tiles and artificial joints. Its composition varies, but it generally consists of about 30% aggregate (a mixture of minerals) such as sand and gravel, 40% cement (a powder made from limestone or clay), and 30% water.
Cement is the one material that never goes out of style. There are no new innovations in architecture or construction that don’t somehow involve cement. Cement is also used to make new materials such as plastics, glass, and hard plastics.