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Why does concrete set hard?
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Concrete is a mixture of sand, gravel, and cement. It is the cement that sets in liquid concrete. It binds together the other ingredients, which give concrete its strength and wear resistance. Cement is made by roasting a mixture of powdered limestone rock and clay. Heating removes water from the rock and clay and it becomes a fine grey powder. When water is added to the cement, it turns back into rock and dries to form a hard solid. | | A large, ready-mixed-concrete truck can carry up to 25 tons of concrete. |
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Previous:
Back
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Book:
1001
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Section:
Science and Technology
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Chapter:
Materials
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