Matrix-strength-dependent strain-rate sensitivity of strain-hardening fiber-reinforced cementitious composites under tensile impact

The effects of matrix strength on the rate-sensitive tensile responses of strain-hardening fiber-reinforced cementitious composites (SH-FRCCs) at high strain rates were investigated using an improved strain energy frame impact machine (I-SEFIM) overcoming the limitations of previous strain energy frame impact machine (SEFIM). The strengths of matrix were 56, 81, and 180 MPa, while 1% long (30 mm) hooked and 1% short (13 mm) smooth steel fibers were blended in all matrices. Dynamic increase factors (DIFs) for the tensile parameters of the SH-FRCCs, as the strain rate increased, were clearly dependent on the matrix strength although they generally increased: a lower strength matrix produced higher DIFs for both the strain capacity and peak toughness, whereas a higher strength matrix generated higher DIFs for the post-cracking tensile strength. Besides, DIF equations were newly proposed for predicting the post-cracking strength.