A practical engineering model to predict the tensile strength of steel fiber-reinforced concrete from the mechanical properties of its constituent materials

The tensile strength of cementitious materials can be increased significantly by the addition of small percentage by volume of steel fibers. The mechanical properties of the resulting fiber composite are dependent on the properties of its constituent materials (matrix material, fibers, and fiber matrix interface) and the geometry of the composite (fiber spacing, fiber aspect ratio, and fiber orientation).;Using a micromechanical finite element model, a parametric study was conducted to evaluate the effect of the mechanical properties of the constituent materials on the first crack and steady state strengths of the fiber reinforced composite. The first crack and steady state tensile strength ratios of steel fiber reinforced cementitious materials were found (using the micromechanical model) to be related to the square root of the fiber spacing ratio, the fiber aspect ratio, the modular ratio, and the mechanical properties of the cementitious matrix material.;Engineering models to predict the first crack and steady state tensile strengths of steel fiber reinforced cementitious materials were developed using the results of the parametric study (using the micromechanical model).;An experimental testing program, using the split cylinder concrete specimens reinforced with random steel fibers was used, to verify the engineering model for the first crack strength ratio of fiber reinforced concrete. The absolute percentage of errors between the predictions of the model and the test results ranged from less than 1% to 15%, with an average error of 4%. The consistency of the test results shows the potential of the split cylinder as a "standard" specimen geometry for verifying the quality of steel fiber reinforced cementitious materials.;The objective of the research reported in this dissertation was to develop engineering models to predict the first crack and steady state tensile strengths of fiber reinforced composites from the mechanical properties of its constituent materials and the geometry of the composite.;The first crack and the steady state tensile strength ratios of typical steel fiber reinforced cementitious composites were found (using the micromechanical model) to increase as the fiber spacing decreases or the fiber aspect ratio is increased.