m coal burning power plants is used in concrete primarily because of its pozzolanic and cementitious properties. These properties contribute to strength gain and improved durability when used with portland cement. Other reasons for using fly ash include economy and beneficial modification of certain properties of fresh and hardened portland cement concrete. This state of the art report gives an overview of the properties of fly ash and its proper use in the production of portland cement concrete. The report contains information and recommendations concerning the selection and use of Class C and Class F fly ashes generally conforming to the requirements of ASTM C 618.