Portland-Pozzolan Cement Made with Tennessee Valley Authority Fly Ash

Fly ash, mechanically collected at the Colbert, Alabama, steam generating plant of the Tennessee Valley Authority, has a chemical composition such that it would be satisfactory for use as a pozzolanic admixture in portland-cement concrete. However, it does not meet current specifications for such use because it is too coarse. The investigation described herein revealed that this fly ash can be used to make a satisfactory portland-pozzolan cement either by grinding the fly ash separately and blending it with commercially manufactured portland cement or by intergrinding fly ash, portland-cement clinker, and gypsum. The rate of chemical activity, as indicated by heat of hydration and the rate of development of compressive strength, decreases with increasing fly ash content of the cement-fly ash blend or the fly ash-portland-pozzolan cement when the fineness is held constant, and increases with increasing fineness when the fly ash content is held constant. Federal Specifications for portland-pozzolan cement are included as Appendix A.