Concrete is a composite material composed of coarse granular material (the aggregate or filler) embedded in a hard matrix of material(the cement or binder) that fills the space among the aggregate particles and glues them together. Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, motorways/roads, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Famous concrete structures include the Burj Khalifa (world's tallest building), Hoover Dam, the Panama Canal and the Roman Pantheon. Concrete technology was known by the Ancient Romans and was widely used within the Roman Empire—the Colosseum is largely built of concrete and the concrete dome of the Pantheon is the world's largest. After the Empire passed, use of concrete became scarce until the technology was re-pioneered in the mid-18th century. Ref: Wikipedia
