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.
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 portland cement, which is a hydraulic cement, or one that hardens under water.