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Strain hardening and multiple cracking behavior of hybrid fiber reinforced cement composites containing different hybrid combinations of steel and polyethylene (PE) fibers under four-point bending are reported. The total volume fraction of fibers was kept constant at 2.5% to maintain a workable mix. Effects of increase in fly ash content as partial replacement of cement beyond 50%, such as 60% and 70% on the flexural response of hybrid steel-PVA (Polyvinyl Alcohol) and steel-PE fiber composites are also evaluated here. Among composites with different volume ratios of steel and PE fibers, the composite with 1.0% steel and 1.5% PE was found to show the highest flexural strength and that with 0.5% steel and 2.0% PE exhibited highest deflection and highest flexural toughness. Generally, the steel-PE hybrid composites exhibited lower flexural strength but higher deflection capacity than steel-PVA hybrid composites. The rate of strength loss after peak load in steel-PE hybrid composites was found low compared to steel-PVA hybrid system. The 50% replacement of cement by fly ash is found to be an optimum fly ash content in hybrid fiber composites.

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This paper reports the results of an experimental program on the effectiveness of a Ductile Fiber Reinforced Cementitious Composite (DFRCC) material, which exhibit strain-hardening and multiple-cracking bahavior under flexural loadings, in retarding the corrosion of steel in Reinforced Concrete (RC) beams. Based on the collective findings from theoretically-estimated steel losses, rapid chloride permeability tests, pH value tests, as well as structural tests, it was concluded that Functionally-Graded Concrete (FGC) beams, where a layer of DFRCC material was used around the main longitudinal reinforcement, had a noticeably higher resistance against reinforcement corrosion compared to a conventional RC beam. The better performance of the FGC beams was also evident from the absence of any corrosion-induced cracking and the very low tendency of the concrete cover to delaminate as measured by a concrete-embeddable fiber optic strain sensor.

Synopsis An analytical approach for predicting the shear and moment capacity of reinforced steel-fibre-concrete (RSFC) beams is proposed. Recent plasticity analyses for shear capacity of reinforced concrete beams are extended to RSFC beams by including the contribution of the fibres. Moment capacity is derived using the usual sectional analysis and fully plasticized stress blocks and forces. By establishing relevant capacities for a given beam loaded over a range of span/depth ratios, the capacity and governing mode of failure can be predicted. The observed failure loads and modes of failure for 22 test beams agree well with the predictions. Data presented in the literature are also analysed and compared. The present approach allows for direct comparison between the efectiveness of stirrups and fibres as shear reinforcement. The results suggest that fibres can replace stirrups partially or wholly as long as parity in the shear reinforcement factor is maintained.