Study On The Flexural Mechanical Properties Of PE-ECC Beams Under Freeze-thaw Cycles

The ultra-high toughness cement-based composite(ECC)has strain hardening property and crack control ability.At present,it is mainly used in beam column joint optimization,seismic reinforcement,dam maintenance,bridge deck connection and other practical projects.Pe-ecc is made by blending PE into cement paste,which makes the material have strong crack resistance,deformation ability and energy absorption ability.The temperature difference between day and night in Xinjiang is large,and the alternation of dry and wet is frequent.Therefore,the study of freeze-thaw environment in Xinjiang is of great significance to the study of pe-ecc durability.In this paper,the pe-ecc concrete is made of Xinjiang local materials,and the optimal mix proportion is determined considering the influence of fiber content and desert sand replacement rate.The rapid freeze-thaw method was used to freeze-thaw the test block,and the bending resistance of pe-ecc simple supported beam after different freeze-thaw cycles was studied,which provided some reference for the study of pe-ecc freeze-thaw degradation in Xinjiang.Based on the uniaxial tensile test of dumbbell specimens,the effects of fiber content and sand replacement ratio on the initial cracking strength,ultimate tensile strength and tensile displacement of dumbbell specimens were compared and analyzed,so as to determine the optimal mix ratio.Pe-ecc concrete test block and simply supported beam are made with the optimum mix proportion.The test results show that the relative freeze-thaw elastic modulus of concrete test block decreases with the increase of freeze-thaw cycles,and the mass loss decreases first and then increases with the increase of freeze-thaw cycles.The compressive strength of cube decreases with the increase of freeze-thaw cycles.After freeze-thaw cycle,the simple supported beam of pe-ecc still meets the assumption of plane section.With the increase of freeze-thaw cycles,the initial crack moment and ultimate moment of simple supported pe-ecc beams are gradually reduced.