Strength and durability of high-volume fly ash concrete Available to Purchase

The effects of replacing 10, 40 or 60% of the cement content by low-calcium fly ash on the compressive strength and durability of the concrete were investigated. An appropriate amount of (super)plasticiser was added to the mix to obtain good workability. At an early age the compressive strength decreases with increasing level of cement replacement. After 28 days the compressive strength increased relatively more for high-volume fly ash concrete than for the control concrete. Concrete with fly ash performed better in lactic/acetic and sulphuric acid during accelerated experiments. The chloride diffusion coefficients resulting from accelerated chloride migration tests were significantly lower for concrete with fly ash than for the control concrete, except for the mixture with 60% replacement of the cement content. The resistance to frost/thaw cycles was similar for all concrete mixtures. The carbonation depth after 9 weeks in a 10% carbon dioxide (CO₂) environment increased with increasing fly ash content. High volumes of fly ash also decreased significantly the resistance against the combined action of frost and de-icing salts (3% sodium chloride (NaCl) solution). From these results it can be concluded that high-volume fly ash concrete has a potential for commercial use in particular applications.