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Synopsis The characteristics of pfa to BS 3892:Part I and their possible effects upon concrete are examined by using supplies from 26 sources in the UK. Fineness identified as giving an over-all measure of ash quality and is used to propose a four-part classification to provide a realistic basis for ash utilization in concrete.

Synopsis The paper describes an investigation into the effect upon the strength of OPC/pfa concrete of the variability of pulverized-fuel ashes from single sources over a period of time. Twenty weekly samples of four ashes were used to make OPC/pfa concretes at three nominal strengths which were then cured under five different conditions. The strength variations caused by the pulverized-fuel ashes were compared with those caused in OPC concretes by an equal number of weekly cement samples. Although variability in ash properties was observed, only one ash exhibited a significantly greater variation in concrete strength than was shown by the cement. Correlations between ash properties and OPC/pfa concrete strengths did not reveal any property which could by itself reliably give any more than a general indication of the probable effect of a batch of pulverized-fuel ash upon OPC/pfa concrete strength.

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