In its simplest form, concrete is a mixture of paste and aggregates (rocks). The paste, composed essentially of portland cement and water, coats the surface of the fine (small) and coarse (larger) aggregates. Through a series of chemical reactions called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.
Within this process lies the key to a remarkable trait of concrete: it's plastic and malleable when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses and dams.
The Portland Cement Association, in addition to serving as a clearinghouse for technical information on cement and concrete from sources worldwide,itself has sponsored research directed at extending the boundaries of technical knowledge in the field since 1918.
PCA research reflects the latest information on standards, specifications, test methods and guides of ASTM International (ASTM), the American Association of State Highway and Transportation Officials (AASHTO), the American Concrete Institute (ACI), and the National Ready Mixed Concrete Association (NRMCA).
It addresses the properties of concrete needed in construction applications, including strength and durability, and provides guidance on all aspects of concrete from mix design to batching, mixing, transporting, placing, consolidating, finishing, and curing.