Use of polypropylene fibers to mitigate spalling in high strength PE-ECC under elevated temperature

The high strength engineered cementitious composites (ECC) with polyethylene (PE) fibers reinforced is vulnerable to spall under fire exposures, which risks the safety of structures. To address this issue, the polypropylene (PP) fibers were admixed in the ECC developed with dune sand as partial replacement of PE fibers up to 0.5 vol%. The experimental results exhibited that the ECC with incorporating sole PE fiber possesses tensile strength and ultimate tensile strain of 9.69 MPa and 3.98 %, respectively, and adding PP fiber at 0.3 vol% ignorable affected tensile properties of ECC; however, they were noticeably diminished as the percentage of PP fiber up to 0.5 vol%. At 20 ℃, the compressive strength of ECC can reach around 74 MPa, however, the thermal exposures tended to decrease this value due to the degradations of microstructures, especially for the exposed temperature exceeded 400 ℃. On the other hand, admixing PP fibers is expected to create preferably connective paths for escape of vapor outwards ECC samples upon rapid heating to 600 ℃, as a result, the explosive spalling was effectively alleviated in the high strength ECC with adding PP fibers at 0.3 vol% and 0.5 vol%.