The words “cement” and “concrete” are often mistakenly used interchangeably. Cement is a powder composed of natural materials such as limestone, clay, sand and/or shale. Concrete is a mixture of water, aggregates (sand and gravel or crushed stone) and cement, which comprises 10% to 15% of the mix.

White Rock Quarries dragline

Through a process called hydration, cement and water harden and bind the aggregates into a rocklike mass. This hardening continues for years, meaning concrete gets stronger as it gets older. There’s no such thing as a cement sidewalk or a cement mixer. The proper terms are concrete sidewalk and concrete mixer.

Source: Portland Cement Association