Pfa For Concrete: Mix Proportioning And Strength Development

Abstract

This paper describes an investigation on mix design of concrete incorporation highly percentage of pulverized fuel ash (pfa} as a cement replacement in concrete. Studies are also made on the strength development of OPC/superplasticised pfa concrete designed for a specified workability and 28 days strength equivalent to that of the corresponding OPC concrete capering a very wide range of pfa usage (from 30% to 70%), water: cement ratio and age at test. Mixes designed by partial but direct replacement of 70% of pfa and water, cement ratio of 0.3 and a superplasticizer dosage of 2% by weight of cement + pfa, shows a slightly lower strength compared to OPC at earlier age but the concrete achieves comparable strength to OPC concrete at later ages. Such a concrete also exhibits highly workable properties with no detrimental effects on the quality of the concrete. Keywords: admixtures, compressive strength, flexural strength, fly ash, workability, proportioning, water-cement ratio, superplasticizer