Effect of in-source variability of pulverized-fuel ash upon the strength of OPC/pfa concrete

Abstract

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.