Strain rate sensitivity of ultra-high performance fiber reinforced concrete

Ultra High Performance Fiber Reinforced Concrete (UHP-FRC) is relatively new cementitious material, which has been developed to enhance material performance such as, durability, workability and strength. UHP-FRC has an outstanding dynamic performance with high capacity to absorb damage. Because of its superior performance under dynamic loading, UHP-FRC has been induced in structures where dynamic resistance is required. It is proven that like other concrete materials, UHP-FRC strength increases significantly when subjected to high strain rates. The objective of this study is to develop understanding of strain rate sensitivity of UHP-FRC with 2% steel fiber by volume fraction and plain High Strength Concrete (HSC). Compressive and flexural tensile strength of each concrete composite were investigated to evaluate and compare their strain rate sensitivity through dynamic increase factor (DIF). The specimens were tested under six different strain rates; three in quasi-static and three in dynamic domain. Strain rates in quasi-static domain conducted by MTS test machine and strain rates in dynamic domain conducted using the drop hammer technique. The test results revealed that UHP-FRC exhibits less strain rate sensitivity while HSC show much higher rate sensitivity in comparison to other materials.