Effect of fire exposure on the bonding behavior of hybrid engineered composite systems

Abstract

When used with self-compacting concrete (SCC) in a fresh state, engineered cementitious composites (ECC) can enhance flexural properties and durability. There is, however, some uncertainty as to whether the composites and their related interfacial bonds will endure high temperatures. This article investigates how fire exposure affects hot-jointed concrete systems (CS) that combine SCC and ECC. Residual flexural and tensile properties and possible degradation/debonding of the interfacial zone after exposure to 800 °C were examined, considering the effect of three different fiber types (i.e. polyvinyl alcohol (PVA), steel (SF), and hybrid PVA/steel fibers) in the tension ECC layer. Visual, microstructural, ultrasonic pulse velocity and mass loss properties were assessed for air- and water-cooled specimens. Also, mathematical models were proposed based on the results of each concrete composite. ECC added to SCC at fresh-to-fresh state significantly increased its flexural and splitting tensile resistance, as well as thermal integrity. All composites were negatively affected by fire, but composite systems maintained their interfacial bond without excessive degradation. It was also determined that fibers at the interface area of composite systems are crucial to preserving their mechanical and physical bonding under fire, thus SF resulted in higher thermal resistance compared to PVA.