Rate-dependent tensile properties of ultra-high performance engineered cementitious composites (UHP-ECC)

The direct tensile properties of ultra-high performance engineered cementitious composites (UHP-ECC) were investigated under a range of strain rates from 0.0001 to 0.05 s⁻¹ in this study. Three kinds of polyethylene fibers with different fiber aspect ratios were used as the reinforced fiber in the UHP-ECC. The rate sensitivity of the UHP-ECC in tension was evaluated in terms of initial cracking stress, peak stress, strain capacity, energy absorption capacity and elastic modulus at different strain rates. The cracking patterns, including crack number, crack width and crack spacing, of the UHP-ECC specimens were also monitored. The test results showed a significant rate effect on the initial cracking stress and a moderate effect on the peak stress and strain capacity. The fiber aspect ratio significantly influenced the tensile properties and failure modes of the UHP-ECC. The matrix strength, single fiber tensile and pull-out tests were conducted at corresponding strain rates to further explain the test results. Finally, the micro-structure of the tensile specimens was observed using a scanning electron microscope.