What are the main components of concrete?

Concrete consists of cement (binding material, typically 10-15%), water (for hydration reaction, 15-20%), coarse aggregate (gravel/crushed stone, 40-50%), and fine aggregate (sand, 25-30%). Admixtures may be added to modify properties. When cement and water react (hydration), they form a paste that binds the aggregates together into a rock-like mass. The proportions are adjusted based on required strength and workability.