EFFECTS OF AGGREGATES AND MICROFILLERS ON THE FLEXURAL PROPERTIES OF CONCRETE

A flexural strength theory for concrete based on the elastic-plastic t heory, was derived In the tests performed the failure criterion of the plain concrete beam was found to be the tensional rupture strain epsi lon(u) which had the value of 0 . 00016 irrespective of the different concrete compositions. The elastic-plastic flexural strength f(tp) was shown to be almost a linear function of the modulus of elasticity of concrete. The problem of enhancing the flexural strength of concrete w as transformed into the problem of increasing the modulus of elasticit y of concrete. Concrete was modelled as a three-phase material consist ing of aggregate, binder matrix and transition zone phases. The transi tion zone between the binder matrix and the aggregate particulates was reasoned to be around the aggregate particles which had a diameter ex ceeding 75 mu m. The modulus of elasticity of concrete was modelled by an improved law of mixtures in which an adhesion factor was introduce d The adhesion factor takes into account the bond inter-action between aggregate particulates and the binder matrix. The results of the theo ry derived were compared with the test results from concretes in which three different aggregates and two microfiller types, mainly, were us ed.