A novel prediction model of packing density for single and hybrid steel fiber-aggregate mixtures

Abstract

Steel fiber can significantly improve the tensile strength, toughness, and crack resistance of concrete matrix, but there is limited research on the packing of single steel fiber-aggregate (SF-A) and hybrid steel fiber-aggregate (HF-A) mixtures. To investigate the effect of steel fibers on the packing of aggregates, the loosely-packed packing density (PD) of 36 SF-A mixtures and 36 HF-A mixtures was measured via the high-rigidity container. The results indicated that the PD always decreased with increasing fiber volume regardless of single or hybrid steel fibers and the size ratio of steel fiber to aggregate particle was a crucial parameter affecting this lowering effect. Moreover, a novel prediction model considering the relative size of fiber and aggregate as key factors was developed and the synergistic effect on aggregates by hybrid fibers was also incorporated into the model. Prediction errors less than 1% were evaluated after calibrating the model parameters.