How is cement created

In the wet method, a slurry is created by adding water to properly proportioned raw materials prior to them being ground, blended and fed into the upper end of a tilted and rotating cylindrical kiln, where their rate of passage is controlled by the kiln's slope and rotational speed. Burning fuel - usually powdered coal or natural gas - is then forced into the kiln's lower end, heating the raw materials to 2,, degrees F 1,, degrees C.

At 2, degrees F 1, degrees C , several chemical reactions fuse the raw materials, creating what are called cement clinkers: grayish-black pellets the size of marbles.

The red-hot clinkers are discharged from the lower end of the kiln and transferred into various types of coolers to reduce their temperature so they can be handled safely. Now cooled, the clinkers are combined with gypsum and ground into a gray powder so fine that it can pass through a micron - or number mesh - sieve.

The flexibility of Portland cement is evident in the different types, which are manufactured to meet various physical and chemical requirements. When architectural considerations require white or colored concrete or mortar, Portland cement can adapt with the manufacture of white Portland cement, just one of a number of special-purpose hydraulic cement types available.

White Portland cement is identical in composition to the traditional gray-colored product, except in color. This is made possible during the manufacturing process by selecting raw materials containing only negligible amounts of the iron and magnesium oxides that give Portland cement its gray color. Blended hydraulic cements, designed to conform to the special requirements of the ASTM C or C standards, are produced by mixing Portland cement, ground and granulated blast-furnace slag, fly ash, natural pozzolans and silica fume.

These cements may also designed as air-entraining, moderate sulfate-resistant or with moderate or low heat of hydration, depending on the need. There are no restrictions on the composition of C cements. Manufacturers can optimize ingredients, such as pozzolans and slags, to achieve a particular set of concrete properties.

While Europe and Asia currently use more blended cements than the United States, environmental and energy concerns, in addition to consumer demand for cements with specific properties, may alter this situation. Request a Quote. The rock then goes to secondary crushers or hammer mills for reduction to about 3 inches or smaller. The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln.

The cement kiln heats all the ingredients to about 2, degrees Fahrenheit in huge cylindrical steel rotary kilns lined with special firebrick. Kilns are frequently as much as 12 feet in diameter—large enough to accommodate an automobile and longer in many instances than the height of a story building.

The large kilns are mounted with the axis inclined slightly from the horizontal. The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.

As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles.

Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers. The cement clinker emerges from the kiln, is cooled, and then finely ground to produce the powder we know as cement. The Canadian cement and concrete industry is pursuing a variety of innovative measures to further reduce its carbon footprint.

Cement powder. Concrete's basic ingredients: cement mixed with sand, gravel, and water.