Fly ash is used in concrete and other portland cement-based systems primarily because of its pozzolanic and cementitious properties. These properties contribute to strength gain and are known to improve the performance of fresh and hardened concrete, mortar, and grout. The use of fly ash typically results in more economical concrete construction.

This report gives an overview of the origin and properties of fly ash, its effect on the properties of hydraulic cement concrete, and the selection and use of fly ash in the production of hydraulic cement concrete and concrete products. Information and recommendations concerning the selection and use of Class C and Class F fly ashes conforming to the requirements of ASTM C618 are provided. Topics covered include a detailed description of the composition of fly ash, the physical and chemical effects of fly ash on properties of concrete, guidance on the handling and use of fly ash in concrete construction, use of fly ash in the production of concrete products and specialty concretes, and recommended procedures for quality control. High-volume fly ash concrete is covered in a general way in this report, readers can consult ACI 232.3R for more information.