Harnessing fly ash potential for developing high strength and high durability concrete

This paper briefly describes a study undertaken to evaluate the potential for developing high performance concrete using fly ash. Three fly ashes of low lime content (ASTM Class F) with a range of fineness were used, together with silica fume for comparative purposes. The results obtained show that provided it is of suitable fineness (for pozzolanic reaction and minimising voids within the cement paste system) and has low water demand (for reducing the water/cement ratio of concrete at a given cement content), fly ash can, on its own, be used to produce high strength and durability concrete. In addition, the quality of such a concrete can be comparable to or better than that produced with the more commonly used silica fume in this role. Where fly ash is not sufficiently fine to fulfil the required criteria of suitability indicated above, this can be compensated by using a tertiary blend with up to five percent of silica fume.