Cement is a marvel of a construction material. It’s one of the most versatile building materials in the world: a simple mixture of clay, sand, limestone and water amped up with artificial coloring and odor-killing chemicals. It’s also the second most consumed substance on planet Earth.
But for all its ubiquity, cement is not well understood. The majority of people think concrete when they hear the word cement, but in reality concrete is just one type of cement. Concrete is basically a mixture of cement, aggregates (like sand or rock) and water that hardens over time to create a strong bond that can withstand pressure and hold together different materials. Cement, however, is the actual binding agent that makes up concrete.
The creation of this binding agent is what has allowed humans to build structures as tall as skyscrapers and as long as bridges—concrete was used in the construction of the Hoover Dam—but it’s also what makes cement production so energy-intensive.
A single cement plant releases more carbon dioxide per year than every car in a city of 3 million people combined. And it gets worse: The process used to heat limestone releases even more carbon dioxide than making steel or aluminum.
Cement companies around the world have been
Cement is a marvel of a construction material. It’s one of the most versatile building materials in the world: a simple mixture of clay, sand, limestone and water amped up with artificial coloring and odor-killing chemicals. It’s also the second most consumed substance on planet Earth.
When mixed with water, it hardens into a durable rocklike material that can be used to build bridges, highways and skyscrapers. In fact, concrete is the most consumed commodity in the world after water — but unlike water, you can’t drink it.
The construction industry accounts for 80 percent of all cement consumption worldwide. Cement is also key to energy production: The material is used to line silos where coal, oil and natural gas are stored. The silo liners prevent toxic gases from escaping when fuel is burned for energy generation. Cement is also mixed with steel to make reinforced concrete for buildings, bridges and other structures that must bear enormous loads or resist aggressive environmental conditions such as saltwater and high temperatures.
Cement is a marvel of a construction material. It’s one of the most versatile building materials in the world: a simple mixture of clay, sand, limestone and water amped up with artificial coloring and odor-killing chemicals. It’s also the second most consumed substance on planet Earth.
Cement is the glue that makes concrete strong. Concrete is used to make buildings, roads, bridges and all kinds of other structures. Cement companies must manage their raw materials carefully to provide concrete at a reasonable price when and where it’s needed. The basic raw material for cement is limestone, which is quarried from the ground. Processing limestone into cement requires a great deal of energy; typically, between 140 and 150 megajoules are required to produce every kilogram of cement (MJ/kg).
If you imagine the world as a series of buildings, cement is the most common building material on Earth. One of the most versatile construction materials in the world, it’s been used to create everything from houses and skyscrapers to sidewalks, bridges and sewer pipes. The second most consumed substance on planet Earth, only water is more widely used.
Cement, like concrete, is a mixture of sand, gravel and rock that hardens into a stonelike mass — the basic ingredient for buildings and roads. But cement is a fine gray powder that resembles flour or powdered milk.
Cement is made by heating a mixture of limestone and clay until it almost melts, then pulverizing it into a fine powder and mixing it with water until it forms a puttylike paste. When this paste is mixed with sand and gravel (or other aggregate), it hardens into concrete.
The Egyptians were one of the first civilizations to use cement as mortar to bind together stones with lime they created by burning limestone in kilns. The ancient Romans made similar use of lime-based mixtures, but their version was far superior to the Egyptian variety.
The Romans discovered that adding volcanic ash produced a very strong cement. They also learned that mixing in horse hair helped make concrete
It can be poured, injected, sprayed or pumped into molds, it hardens out of sight and it’s stronger than steel. It’s great stuff – but like everything else in this world, there’s a catch.
The manufacturing process is pretty simple: the ingredients are mixed, ground and heated to form a “clinker,” which is then ground with gypsum to form Portland cement. The cement is then ready to ship to ready-mix concrete companies to be used in a variety of construction projects. Although the dry process is the most modern and popular way to manufacture cement, some kilns in the United States use a wet process.
The energy required to build a typical home out of cement is the same as running a car for two years. This energy is produced by the burning of fossil fuels, most notably coal, which pump tons of carbon dioxide into the atmosphere. Cement production also contributes to climate change in another way: it requires enormous amounts of what’s called “limestone,” which is calcium carbonate that has been chemically separated from other materials using a process that requires high heat. Calcium carbonate is found in limestone, seashells and coral reefs and when heat is applied to it, it releases CO2, a greenhouse gas.
Scientists are working on creating new types of cement that use less or no limestone at all. The hope is to find ways to create cement using alternative substances like ash or slag (a byproduct of iron production). But this type of research takes time and money — and unfortunately, the cement industry has no incentive to invest in it. In fact, the cement industry isn’t even regulated under any international environmental treaty to curb its CO2 emissions.
The good news is that there’s already an alternative construction material available today: wood. Wood sequesters carbon dioxide — meaning it stores it rather than releasing it — making wood construction an inherently more environmentally friendly option