Cement is a hydraulic binding agent in powder form that hardens into a stone-like mass when mixed with water. As the essential binder in concrete and mortar, cement is one of the most widely used building materials in the world.
Composition and production
Cement is produced by grinding a mixture of limestone and clay and heating it in a rotary kiln at temperatures of approximately 1450 degrees Celsius. The resulting material, called clinker, is then ground into the familiar grey powder. During the grinding process, a small amount of gypsum is added to regulate the setting time.
The most common type of cement is Portland cement, developed in the 19th century. Several variants exist with specific properties:
- CEM I (Portland cement): pure cement, fast-setting
- CEM II (Portland composite cement): with additions such as fly ash or blast furnace slag
- CEM III (Blast furnace cement): with a high proportion of blast furnace slag, more sustainable and more resistant to chemical attack
The strength class is indicated by a number (32.5 / 42.5 / 52.5) representing the compressive strength in N/mm2 after 28 days.
Application
Cement is indispensable in virtually every construction project. Its main applications include:
- Concrete: cement mixed with water, sand, and gravel forms concrete, the most widely used structural material in construction
- Masonry mortar: cement mixed with sand and water serves as jointing material when laying bricks and blocks
- Plaster and render: cement-based plaster is applied as a finishing layer on walls and ceilings
- Screeds: cement screeds provide the substrate for final floor finishes
When working with cement, it is important to consider the curing time, processing temperature, and the correct water-to-cement ratio. An incorrect ratio can lead to reduced strength or workability issues.
Related terms
- Concrete
- Mortar
- Portland cement
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