A study has been undertaken into the properties of foamed concrete in which large volumes of cement (up to 75 wt.%) have been
replaced with both classified and unclassified fly ash. This fourth paper in the series examines the effects of increasing the levels of ash on
the compressive strength of the concrete. Twenty-seven different mixtures were cast with varying ash contents and densities, and the results
used to develop models that have been used to predict the compressive strength of the foamed concrete. The output from the models predicts
an optimum ash content for maximum strength at a given porosity and age and shows that the optimum value increases with increasing age.
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