Role of macro fibers (steel and hybrid-synthetic) in the residual response of RC beams exposed to high temperatures

Abstract

Inclusion of fibers can mostly enhance the mechanical properties of concrete; however, the role of those in reinforced concrete beams wherein the interaction between concrete, steel reinforcement, and fibers is crucial can be different. This paper provides an experimental study to evaluate the residual behavior of macro fiber-RC beams exposed to high temperatures. Thirty-six scaled reinforced concrete beams were designed and fabricated according to the ACI 318 criteria and requirements, subjected to high temperatures up to 800 °C. In this investigation, mechanical and deformation properties of heated RC beams, failure patterns, and confinement role of fibers were examined, discussed, and compared with non-heated specimens. This investigation indicated, adding steel fibers noticeably improved the residual bearing capacity and bond interaction between steel bars with concrete at high temperatures. Hence, this value for RC beams reinforced with steel and hybrid-synthetic fibers at 800 °C was 65% and 48% of their initial capacity, respectively; however, for plain concrete was about 40%. Moreover, the transformation of failure patterns depended on the type of used fibers and experienced temperatures.