Rate Effect on Pullout Behavior of Steel Fibers Embedded in Very-High Strength Concrete

Problem statement: Rate dependence of the newly developed Very-High-Strength-Concrete (VHSC) composites has received little or no attention so far. Approach: In this research, the bond-slip mechanisms of four types of steel fibers embedded in VHSC matrices were investigated through single-fiber pullout tests with the loading rates and matrix strengths are the primary variables. This study presented the experimental results of steel fiber-matrix bond characteristics and discussed the influence of loading rates on the pullout behavior. Results: The results were measured in terms of peak loads and total fiber pullout work or dissipated bond energy. Results indicated that the increase in pullout rate increases both peak load and total pullout work for all deformed fibers but had no effect on smooth, unreformed fibers. Conclusion/Recommendations: De formed and smooth fibers exhibit different rate sensitivities. The variation in response was attributed to the fiber end conditions. It is recommended that (1) additional experimental tests should be performed at other loading rates and (2) an analytical model should also be developed to analyze the rate effect on the interfacial deboning process of VHSC composites.