Effect of high temperatures on hot-bonded SCC/ECC and SCC/UHPC composite systems

Abstract

The use of Engineered Cementitious Composites (ECC) and ultra-high-performance concrete (UHPC) in combination with self-consolidating concrete (SCC) in a fresh state can improve the economical and sustainability benefits of modern concretes while increasing the structural properties of SCC-elements. However, it is important to determine if the resulted hot-jointed composite systems (CS) can resist the harsh environments-like fire conditions, especially with the presence of unknown proprieties interfacial bond layer. The goal of this study is to investigate and compare the flexural and bonding behavior of the SCC/ECC and SCC/UHPC composites at ambient and high temperatures up to 800 °C. In addition to the type of modern concrete in the tensile layer, the effect of fiber reinforcement on fire endurance of CSs was also investigated through the inclusion of PVA and steel fibers in ECC and UHPC. After cooling in air, fire-exposed samples were examined for visual, microstructural, tensile, and flexural bond properties. It was confirmed that, the applied ECC and UHPFRC in CSs significantly improved the mechanical properties of SCC elements at ambient and all fire exposure temperatures. In addition to the enhanced fire endurance and better residual performance for the UHPRFC-based CSs, steel fibers were shown to be essential for the physical anchorage and bond preservation between SCC/ECC and SCC/UHPFRC, particularly at 400 °C–800 °C.