Proposed classification of HPFRC composites based on their tensile response

The tensile response of fiber reinforced cement (FRC) composites can be generally classified in two distinct categories depending on their behavior after first cracking, namely, either strain-hardening or strain-softening. Within the strain-softening category, one can distinguish between deflection-hardening and deflection-softening behavior. Several standard tests (ASTM, JCI, RILEM) are available to assess the characteristics of mostly strain-softening FRC composites through bending tests, but no standard test is currently available to characterize strain-hardening response in tension. Such composites have been described as high performance FRC or HPFRC composites. In this paper a proposal is put forth to characterize the response of strain-hardening FRC composites based on the results of direct tensile tests. The classification is based on several parameters which include a minimum value of elastic modulus, a minimum value of peak strain after first cracking, and the tensile strength level. While one of the key obstacles remains, that is, to develop a realistic and meaningful tensile test standard, some requirements on minimum specimen size, fiber size and aggregate size are also suggested.