Cement

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Calcium oxide powder

William Aspdin Radford cyclopedia Volume 1

Cement is a binding material used in construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Cement is the most widely used material in existence and is only behind water as the planet's most-consumed resource.

Composition

Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron, and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore. These ingredients, when heated at high temperatures form a rock-like substance that is ground into the fine powder that we commonly think of as cement.

Types of Cement

There are several different types of cement, including:

• Portland cement: The most common type of cement in general use around the world, used as a basic ingredient of concrete, mortar, stucco, and non-specialty grout.
• White Portland Cement: Used in applications where it is desirable not to have the gray color of normal Portland cement. It is used in decorative works and also wherever vibrant colors are desired.
• Hydraulic cement: Sets and hardens by chemical reaction with water and is capable of doing so under water.
• Non-hydraulic cement: Must be kept dry in order to retain its strength.

Production

The production of cement involves several stages. The first step is the extraction of raw materials, followed by their processing to produce the raw mix, which is then heated in a cement kiln to produce clinker. The clinker is ground to a fine powder and mixed with a small amount of gypsum to produce cement.

Environmental Impact

The cement industry is one of the primary producers of carbon dioxide, a potent greenhouse gas. The production of cement accounts for about 8% of global carbon dioxide emissions. Efforts are being made to reduce the environmental impact of cement production by improving process efficiency, using alternative fuels, and developing low-carbon cements.

Uses

Cement is used in a wide variety of applications. These include the construction of buildings and infrastructure, the production of concrete pipes, and the manufacture of precast concrete products. Cement is also used in the production of mortar for laying bricks and blocks, in the mixture of concrete for foundations, roads, and bridges, and in various other construction-related activities.

See Also

• Concrete
• Mortar (masonry)
• Portland cement
• Cement kiln
• Environmental impact of concrete