Research On Influence Of Polypropylene Fibers With Different Length And Diameter On Mechanical Properties Of High-strength Concrete After High Temperature

High-strength concrete (HSC) has been more widely used,in order to adapt to the development of modern engineering structures of large span, high rise, overloaded as well as withstanding harsh environment.However,the high density and low permeability of HSC leading to larger brittleness and poorer toughness,seriously affect the durability of structure and service life especially the tendency of spalling of HSC when exposed to fire and high temperature,the bearing capacity fire resistance of member and safety of structure will be dramatically reduced.The incorporation of Polypropylene Fibers into HSC is one of the effective measures to improve the performance of brittleness,toughness and fire resistance. This paper intends to study the mechanical properties of HSC doped with Polypropylene Fibers with different length and diameter after exposed to high temperature.As follows:(1) After summarizing the literatures at home and abroad, the mechanical properties of HSC, with and without Polypropylene Fibers, after exposed to high temperature were comprehensively reviewed.(2) By simulating the high-temperature test, the colour, crack and spalling of the specimens were observationally studied.(3) The compressive performance of HSC mixed with Polypropylene Fibers subjected to high temperature was studied. After investigating the variation of cube compressive strength (fcu) and axial compressive strength (fcp) of HSC with different length and diameter, under the same dosage with increasing temperature, and the effect of Polypropylene Fibers with different length and diameter on fcu and fcp, the relationship between temperature and fcu, fcp were established respectively. Simultaneously, the influence of specimen size on fcu was discussed at high temperatures before and after.(4) The splitting tensile strength of HSC mixed with Polypropylene Fibers subjected to high temperature was studied. The variation of splitting tensile strength (fts) and tension and compression ratio (fts/fcu) of HSC with different length and diameter, under the same dosage were examined with increasing temperature, afterwards, the influence of PP fibers on fts was discussed at high temperatures before and after(5) The elastic modulus of HSC with Polypropylene Fibers after high temperature was studied. After investigating the variation of Ec of HSC with different length and diameter, under the same dosage with increasing temperature, and the effect of PP fibers with different length and diameter on Ec, the relationship between temperature and Ec was established.(6) The relationship of cube compressive strength (fcu), axial compressive strength (fcp), splitting tensile strength (fts), elastic modulus (Ec) of HSC with different length and diameter between the temperature before and after were comparatively studied respectively.