Influence of high temperatures on the residual mechanical properties of a hybrid fiber-reinforced strain-hardening cementitious composite

Recent studies have shown improved mechanical performance of Fiber-Reinforced Concretes (FRC) compared to conventional concrete at high temperatures. While polymer fibers in FRC improve the compressive behavior by providing pathways for moisture to escape through melting of fibers at high temperatures, steel fibers in FRC improve the tensile behavior through crack-bridging at high temperatures. The goal of this research is to investigate the influence of utilizing both polymer and steel fibers in a single FRC for improving compressive and tensile properties at high temperatures, simultaneously. For this purpose, a Polyvinyl Alcohol (PVA)-steel Hybrid Fiber-Reinforced Strain Hardening Cementitious Composite (HFR-SHCC) was developed. SHCC is a special class of FRC with strain hardening behavior under direct uniaxial tension. The residual compressive and tensile properties of HFR-SHCC after being subjected to temperatures of up to 800 degrees C were experimentally determined. Additional FRCs, including a conventional SHCC with only PVA fibers and a fiber-reinforced concrete with only steel fibers (steel FRC), as well as conventional concretes of two different compressive strengths were tested with the same protocol for a comprehensive comparison. The HFR-SHCC shows clear improvement over conventional SHCC, steel FRC and conventional concretes in terms of residual tensile strength after exposure to high temperatures, while simultaneously retaining the benefits of conventional SHCC, which include high tensile strain capacity and microscopic crack widths at normal temperatures and improved retention of compressive strength after exposure to high temperature. (C) 2019 Elsevier Ltd. All rights reserved.