This report describes the first part of a series of investigations to assess the potentialities of pfa for improving the properties of lean concrete roadbases. The work showed that by adjusting the proportions of pfa, cement and water an ash-modified lean concrete can be produced that will have strength properties comparable with those of normal lean concrete at any given age. However, the addition of pfa modifies the rate of gain strength so that an ash-modified lean concrete does not completely emulate the properties of normal lean concrete. In general the addition of ash leads to lower early strengths and higher long term strengths than are obtained with normal lean concrete. The results of compaction trials on mixes of ash-modified lean concrete showed that compactability was improved by the addition of pfa and satisfactory compaction could be obtained in layers up to 300 mm thickness. The work described in this report suggests that ash-modified lean concrete does have some advantages over normal lean concrete as a roadbase material but no final conclusions can be drawn without further studies to evaluate its structural properties relative to those of normal lean concrete. Studies of those properties are being made and they will be the subject of a further report in this series. (Author/publisher)
Abstract