The terms cement and concrete are often used interchangeably—a usage that ignores the rich history and etymology of each term. The kinds of cement and concrete used today are similar to those used by the ancient Romans. After the Roman Empire fell in the fifth century, people lost the art of making cement and it was not rediscovered until the mid-1700s. Cement, from Latin caementum, “rough-cut stone,” is made from limestone and clay that is crushed, heated, and ground into a powder. It is mixed with water and materials such as sand, gravel, and broken stone to make concrete. Cement and water form a paste that binds the other materials together as the concrete hardens, a process reflected in the etymology of the term itself. Concrete is a combination of the Latin prefix com-, “together,” and crescere, “to grow.” Reinforced concrete is made by pouring concrete around steel bars. Without this added strength, the building of modern skyscrapers would be impossible. Prestressed concrete is made by pouring concrete around steel cables stretched by jacks. When the jacks are released, the cables compress the concrete and strengthen it.
