Novel Mix Design Methodology for Self-Compacting Steel-Fiber Reinforced Concrete Based on Rheological and Mechanical Concepts

We describe a new methodology to calculate mix proportions of components for self-compacting steel-fiber reinforced concrete [Construction and Building Materials 189 (2018) 409–419]. The methodology is based on a previous one for plain self-compacting concrete by Prof. B. L. Karihaloo and co-workers, which has been expanded to include steel fibers while maintaining self-compactability of the concrete. The methodology has two key points. The first one is the rheological behavior of the fresh material, which leads to considering the effective viscosity of the suspension with fibers as a design parameter. By means of micromechanical models we estimate this parameter from the plastic viscosity of the cement paste and the volume fraction and aspect ratio of the fiber. The second one is the desired compressive strength of the composite material, which leads to setting water-cement ratio as the other design parameter. Besides, water-cement ratio influences the plastic viscosity value of the cement paste, together with the content of superplasticizer admixture. This rheological parameter has to be measured by means of rheometers or approximated by other simpler and cheaper instruments, like capillary viscometers (Cannon-Fenske or Marsh funnel). The methodology has been programmed numerically in MATLAB to make some practical design charts by means of which the quantities of the concrete components are calculated. The use of these design charts is explained with an example. The study also provides experimental validation in fresh and hardened state. The results show the robustness of the proportioning methodology.