Energy-Based Method for Evaluating Cracks and Resistance of Fiber Reinforced Ultra-High Strength Concrete under Impact Loads

Document Type : Research Article

Authors

1 Department of Civil Engineering, Imam Khomeini International University, Qazvin, Iran

2 Department of Civil Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran

3 Department of Civil & Environmental Engineering, Amirkabir University of Technology, Tehran, Iran

Abstract

In order to adjust the lack of sufficient ductility of ultra-high strength concrete (UHSC), different types of fiber were used in this study. This research investigates the effect of glass, polypropylene and steel fibers on the impact resistance and crack propagation of fiber reinforced UHSCs by implementing slab specimens with a dimension of 300×300×30 mm. The experimental program includes 18 specimens with 1%, 1.5% and 2% of concrete volume for each type of fiber which was made with two different mixing methods (Ordinary fiber reinforced concrete (FRC) and high performance fiber reinforced concrete (HPFRC)). In this study, specimens were placed under a low-velocity impact loading (5.42 m/s) within a fixed rigid constrained setup. The health index and the crack propagation correlation are two criteria for determining the trend of degradation and impact resistance reduction. Results demonstrate that the FRCs show higher impact resistance in comparison with the HPFRC because the HPFRC method doesn’t provide enough cohesion between concrete and fibers. The obtained results also show that FRC specimens include polypropylene, endure higher impact resistance with a greater amount of health index rather than other specimens. By increasing the fiber’s volume in the specimens fabricated with glass and polypropylene, a more homogenous composite was formed and energy spread more uniform over all faces of FRC specimen.

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