Abstract
The tensile mechanical response of ultra-high-performance concrete (UHPC) is distinctly different from conventional concretes and traditional fiber-reinforced concretes. UHPC can exhibit a pseudo-strain-hardening behavior wherein the fiber reinforcement bridging tensile cracks is sufficient to allow for a sustained tensile capacity at stress levels near the tensile-matrix-cracking strength through significant tensile-strain levels. This mechanical response is generating interest in the structural design community; however, quantification of the response through standardized test methods is necessary. Researchers at the U.S. Federal Highway Administration have developed a test that directly measures the tensile response of UHPC-class materials. This test, conceptually similar to the ASTM E8 [ASTM E8-13a: Standard Test Methods for Tension Testing of Metallic Materials, Annual Book of ASTM Standards, ASTM International, West Conshohocken, PA, 2013] test for steel, provides a method to assess the tensile response from elastic behaviors through multi-cracking and eventual crack localization. Prismatic specimens are loaded in direct tension under a fixed-end condition, allowing cast or extracted specimens to be tested under conditions that mimic the tensile loading that can occur within full-scale structural elements. Testing to date has assessed two UHPC matrices and a variety of fiber types/dosages with promising results in terms of test-procedure robustness.
