Pullout Characterizations of Various Steel Fibers Embedded in Very High-Strength Concrete

Problem statement: There is a real need for a fundamental understanding of bond and bond mechanisms in the newly developed Very-High-Strength-Concrete (VHSC) materials. The interfacial steel fiber/VHSC matrix bond tests are needed to characterize VHSC and to aid in the development of analytical models that describe bond behavior of this new material. Approach: This research investigated bond-slip characteristics of four different steel fiber types embedded in Very-High-Strength-Concrete (VHSC). Parameters investigated include: Mechanical affect of the fiber geometry, fiber embedment length, medium strength and embedment method. Results were measured in terms of peak pullout load and total pullout work or dissipated bond energy. Results: Results indicated that the mechanical affect of fiber geometry had the most influence on both peak load and total work with increases over 100% for some fibers. The increase in embedment length also increased both peak load and total pullout work but was found to have more influence on smooth, undeformed fibers. Conclusion/Recommendations: Findings of this research should aid in the rational predictions of VHSC’s mechanical performance and help identify the effectiveness of different types of steel fibers on improving its tensile properties and toughness. It is recommended that an analytical model should also be developed to analyze the interfacial debonding process of VHSC composites.