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TRUE OR FALSE? 287
Who first produced transparent glass?
AFTER WATER, CONCRETE IS THE MOST WIDELY USED 5,000 The crucial ingredient in concrete is cement, which is made by mixing limestone with small amounts of clay and sand, and heating it in a kiln. Four billion tons of cement are produced each year. This is enough to make Egypt’s Great Pyramid of Giza 5,00
FAST FACTS SUBSTANCE ON EARTH IN SUMMER Steel expands when it is hot and contracts when it is cold. However, not all four sides of the structure can be in the sun at once. The portion of the structure in direct sunlight expands more than the portion in the shade. This means that the towe
US_286_287_309600_Materials.indd 287 19/12/17 3:49 pm
