Effect of elevated temperature on strain-hardening engineered cementitious composites

•Engineered cementitious composite is proposed for spent nuclear fuel storage.•High temperature effect on ECC uniaxial tension properties is characterized.•ECC has high spalling resistance after 6h of exposure to 600°C.•“Spider web” nano-cracks are absent in ECC at temperatures up to 600°C.•The change in ECC microstructure explains its mechanical properties deterioration. Strain-hardening engineered cementitious composite materials (ECC) is proposed to substitute quasi-brittle concrete materials for building extended spent nuclear fuel (SNF) storage systems in nuclear power plants. While most of ECC properties have been established under normal temperature, the study aims at understanding ECC material behavior under elevated temperature that is expected in a SNF storage environment. On the composite level, ECC specimens were characterized at various temperature levels up to 600°C under both uniaxial tension and compression. The elevated temperature effect on tensile strength and strain capacity, compressive strength and failure mode, moisture loss, and spalling behavior was studied. On the microstructure level, optical microscopy and scanning electron microscopy were conducted to probe the degradation of components, and the change of pore structures due to fiber melting within ECC. The results will provide crucial data and insights for future studies of re-engineering ECC with robust properties specifically desired for nuclear engineering applications.