Synergistic tensile response of reinforced ultra high performance concrete with low fiber contents

From the perspectives of ductility, economic and construction, reinforced ultra high performance concrete (UHPC) structures with low fiber contents have a significant potential in applications. This paper studied the tensile behaviors and damage mechanisms of reinforced UHPC with low fiber contents based on the direct tensile tests accompanied with acoustic emission (AE) detection system. The test results show that the high strength steel bar can prolong the tensile multiple-cracking stage of reinforced UHPC with low fiber contents in some extent at the serviceability stage and further improve its tensile ductility via inducing additional longitudinal cracks at the failure stage. It is found that the low fiber contents and steel bar grades have marginal effect on the tension stiffening at the first cracking of reinforced UHPC. Non-negligible tension stiffening effect still remains at yielding of steel bar and it is more obvious for normal strength steel bar and UHPC with a higher fiber content. The AE weighted peak frequency can identify the tensile damage model of reinforced UHPC with low fiber contents: no internal damage occurs during stage Ⅰ; matrix cracking occurs accompanied by marginal fiber pull-out during stage Ⅱ; matrix cracking and fiber pull-out are dominated during stage III and stage IV, respectively.