The Rheology of Fresh Concrete

The rheology of fresh concrete is studied by investigating the main characteristics of stability, compactability, and mobility. Stability is dependent on the bleeding and segregation tendencies. Compactability is related directly to relative density. Mobility is shown to be a function of the viscosity of the cement paste, cohesion of the mix and its angle of internal resistance to deformation. Each of these factors was investigated separately and expressed where possible in absolute units. An analysis of these individual findings enabled an over-all picture to be obtained of the relative contribution and interaction of these properties. From this has emerged a practical concept of the flow characteristics of fresh concrete. This under standing of the internal factors involved, which are normally slumped together under the one heading of workability, has proved valuable in assessing which mix characteristics play a significant part in various practical problems in concrete construction.