Page 35 - Curriculum Visions Dynamic Book
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Cement
Cement is a word used for many kinds of adhesive, but is most generally applied to the powder used in the building industry.
The main process involved is hydration, which is a chemical reaction of the cement and water. It produces tiny interlocking crystals with a large surface area. Some cements will set and harden under water. They are called hydraulic cements. The most important of them is Portland cement.
Both the ancient Greeks and the Romans knew how to make cement and concrete. The Romans used it widely. The term cement comes from the Latin word cementum, meaning “stone chippings,” since they were used in the lime-based cement called mortar. They had no special name for the binding material itself.
The Romans used volcanic ash mined near the
city of Pozzuoli as cement. This ash was rich in clay minerals, the essential ingredient of any cement, since these minerals react with lime in the presence of water to form a hard material.
(Above) Limestone from a nearby quarry is constantly fed to this cement plant by a conveyor belt.
(Below) This very large cement plant has two rotating kilns.
Kiln
Kiln
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