Influence of Fly Ash Upon the Workability and Early Strength of Concrete


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Title: Influence of Fly Ash Upon the Workability and Early Strength of Concrete

Author(s): D.W. Hobbs

Publication: Special Publication

Volume: 79


Appears on pages(s): 289-306

Keywords: cement pastes; compacting; compressive strength; concretes; fly ash; mix proportioning; slump tests; workability. --

Date: 5/1/1983

Workability and strength measurements made on concretes in which up to 20 per cent by weight of the aggregate was replaced by an equal volume of fly ash are described. This method of proportioning the concrete mix has the advantage that both the water-Portland cement ratio and the volume of the water-Portland cement fraction can be held constant so that the extent to which fly ash is inert or cementitious at early ages can be assessed. It is shown that the variations in slump are in broad agreement with the predictions for a Bingham suspension in which a proportion of the particles is replaced by an equal volume of finer particles and that the strength contribution attributed to the fly ash is dependent upon the water-Portland cement ratio.