Fire resistance of ultra-high performance strain hardening cementitious composite: Residual mechanical properties and spalling resistance

Ultra high performance strain hardening cementitious composites (UHP-SHCC) is a special type of cement-based composite material with outstanding mechanical and protective performance at room temperature. But its fire performance is unknown and there is a lack of research in this aspect. This study presents an experimental program to study fire resistance of UHP-SHCC under two aspects, viz. high-temperature explosive spalling resistance and residual mechanical performance after a fire. Both compressive strength and tensile strength of UHP-SHCC were found to deteriorate with increasing exposure temperature. Tensile strain-hardening feature of UHP-SHCC would be lost at 200 °C and above. It was found that PE fibers are found not effective in mitigating explosive spalling, although they start to melt at 144 °C. FE-SEM (Field Emission Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray) techniques were used to study the state of fiber, fiber/matrix interaction, and microcracks development. Microscopic study found that melted PE fibers were still present in the cementitious matrix, and the melting did not introduce more microcracks. Furthermore, it was difficult for melted PE fibers to diffuse through the matrix, thus providing the reason that PE fibers did not mitigate explosive spalling in UHP-SHCC.