This document discusses materials used in highway construction including aggregates, bitumen, asphalt, cement, and steel reinforcement. It provides details on the composition, production, and properties of these materials. Aggregates include sand, gravel, and crushed stone. Bitumen and asphalt are refined from crude oil and used to bind aggregates in asphalt concrete. Cement is produced by heating limestone and clay and is the binding agent in concrete. Steel reinforcement provides tensile strength to concrete.