The results of a 3-year study on the properties of concrete containing fly ash are presented. Both the fresh and hardened properties are reported of concrete made using Type 1 cement, river gravel, natural sand, and fly ashes from several sources. The mixtures were proportioned to have similar slump and a constant cementitious content by weight. It is shown that concrete containing fly ash can be proportioned having equal strength properties and adequate durability when a suitable ASTM C 618 Class C or F fly ash is used. Test data on over 1600 laboratory and field specimens tested for freeze-thaw resistance, flexural strength, compressive strength, creep, shrinkage, and abrasion resistance are presented. Fly ash contents ranging from 0 to 35 percent by weight of portland cement were used with both Class C and Class F fly ashes. Guidelines for the selection of materials and their proportions for producing concrete containing fly ash to meet existing highway specifications for concrete are presented.