Cement and concrete are among the most important building materials. Cement is a fine, gray powder. It is mixed with water and materials such as sand, gravel, and crushed stone to make concrete. Cement and water form a paste that binds the other materials together as the concrete hardens. People often misuse the words cement and concrete. A person may speak of “a cement sidewalk.” But the sidewalk actually is made of concrete.
Concrete is highly fire-resistant, watertight, and comparatively cheap and easy to make. When first mixed, concrete can be molded into almost any shape. It quickly hardens into an extremely strong material that lasts a long time and requires little care.
Nearly all the cement used today is port/and cement, which is a hydraulic cement, or one that hardens under water. This cement was named portland because it has the same color as stone quarried on the Isle of Portland, a peninsula on the south coast of Great Britain.
Uses of cement and concrete
Nearly all skyscrapers and factories and many homes stand on concrete foundations. These buildings may also have concrete frames, walls, floors, and roofs. Concrete is used to build dams to store water and bridges to span rivers. Cars and trucks travel on concrete highways, and airplanes land on concrete runways.
Concrete tunnels run through mountains and under rivers. Concrete pipe distributes water, carries away sewage, drains farmland, and protects underground telephone wires and electric power lines.
Portland cement is used chiefly to make concrete. But it can also be mixed with soil and water to form soil-cement, which is used in road paving and dam construction and for lining reservoirs.