AbstractEngineered cementitious composite (ECC) is a relatively recent construction material with characteristics of high ductility and energy dissipation capacity. Such ductility is fulfilled by adding polymeric fibers, such as polypropylene (PP), polyethylene (PE), and polyvinyl alcohol (PVA) fibers, which would inevitably experience fusion under fire. This paper focuses on the behavior deterioration of postexposure high-strength engineered cementitious composite (HSECC). Color change, surface cracking, and spalling phenomena of HSECC specimens were inspected after specimens exposed to 200°C, 400°C, 600°C, 800°C, and 1,200°C for 1 h. Weight loss, residual compressive/flexural strength, and failure modes of cubes were evaluated correspondingly. Experimental results indicated that the threshold temperature for HSECC to crack is lowered in comparison with ECC of normal strength, whereas explosive spalling behavior could still be prevented effectively with 2.0 vol% PVA fiber. The loss ratio of weight and strength in HSECC was lower than that in ECC, but the failure modes under compression were found to be more catastrophic. HSECC exhibits lower intensity in an X-ray diffraction (XRD) curve than that of ECC. Apparent needle-like channels were observed beyond 400°C, then were gradually filled with reaction products ascribed to the synergistic effect of thermal expansion, volume increase caused by chemical reactions and pore-structure coarsening, and manifested by the results of mercury intrusion porosimetry (MIP).