In July 1979, the Oklahoma Department of Transportation funded a research program at Oklahoma State University concerned with the performance of concrete containing fly ash (State Study No. 79-11-3), Initially, attention was directed towards the influence of fly ash on the corrosion of reinforcing steel. A study of available literature did not indicate that past use of fly ash had been detrimental from a corrosion standpoint. During a meeting with the Research Advisory Committee in early 1980, it was concluded that an experimental study of the influence of fly ash on corrosion was not warranted at this time and attention should be given to other factors related to the use of fly ash in concrete. A brief summary of the literature study was submitted to the sponsor in Apri 1 1980. In May 1980, a work program covering the remaining months of the project was approved. This effort, which was to develop general data concerned with the strength of mixes containing various percentages of fly ash, is the subject of this report. During this phase of the project, type I portland cement was replaced by fly ash on a weight basis. The percent replacement varied from O to 50 in. increments of 10 percent. Both coarse and fine aggregates used conformed to ASTM Standard C33 (see Appendix A), while the air entraining conformed to the Highway Specification, Section 701 (1).