Research on the residual mechanical properties of hybrid fiber ECCs after high-temperature exposure

In this work, the mechanical properties of hybrid fiber-reinforced cementitious composites (CP-ECCs) composed of polypropylene fibers (PPs) with varying volume fractions and 1% volume fraction chopped carbon fibers (CFs), as well as the influence of different fly ash (FA) contents on material performance under both room temperature (20 °C) and high-temperature conditions, are systematically studied. Through experiments conducted at five target temperatures (20, 200, 400, 600, and 800 °C), the residual mechanical properties, fundamental mechanical properties, and microstructural evolution patterns of the CP-ECC were analyzed. The results indicated that the mechanical properties of the material generally tended to increase with increasing temperature, reaching peak strength at 600 °C, followed by a significant decrease at 800 °C. Scanning electron microscopy (SEM) analysis revealed that the incorporation of PP fibers effectively suppressed cracking and spalling in concrete at 600 °C. Moreover, the carbon fiber-like reinforcement structure formed by the CF fibers and molten PP fibers further enhanced the mechanical properties of the ECCs at elevated temperatures. This study innovatively designed a novel high-temperature resistant hybrid fiber ECC material. This material provides a new theoretical foundation for the application of ECCs in high-temperature environments, with significant theoretical value and practical significance.