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Concrete
BUILDING MATERIALS & CONSTRUCTIONbeginner
Definition
A composite building material made from cement, water, sand, and aggregate (gravel or crushed stone). When mixed and poured, it is fluid and can be cast into almost any shape; as it cures, it hardens to stone-like strength. Reinforced with steel bars (rebar), it can resist both compression and tension.
Example
The Pantheon in Rome (128 AD) features the world's largest unreinforced concrete dome — a testament to Roman mastery of the material nearly 2,000 years ago.