Study On The Mechanical Properties And Damage And Failure Morphology Of Polypropylene Fiber Reinforced Concrete

Polypropylene fiber reinforced concrete(PPFRC)is widely used in hydraulic engineering,civil engineering and geotechnical engineering in China.In different projects,the mix ratio,fiber content and curing conditions are quite different.Its performance will also have varying degrees of impact.In this paper,the mechanical properties,fiber cracking resistance and failure law under different stress conditions of polypropylene fiber reinforced concrete with different fiber content and different curing ages were studied to provide theoretical support for the rational use of polypropylene fiber reinforced concrete.The research content of this paper includes the following aspects:(1)the influence of different fiber content on concrete strength,impermeability and dry shrinkage resistance were analyzed statistically.Combined with engineering application,summarizes the parts of polypropylene fiber reinforced concrete used in hydraulic engineering,and found hydraulic engineering The commonly used fiber content is between 0.6?1.5 kg/m3,of which 0.9 kg/m3 is used most.According to the research situation,the research questions of this paper are proposed.(2)The influence of different fiber content on the workability of concrete mixture was discussed.It was found that the addition of polypropylene fiber reduced the workability of concrete.In the mixing ratio of water-binder ratio of 0.36,when the content exceeds 1.2 kg/m3,the mixing of the mixture is difficult,and the mixing water and the amount of the water reducing agent need to be adjusted.The addition of polypropylene fibers(PPF)facilitates the cohesiveness and water retention of the mixture.(3)The effect of different polypropylene fiber content on the compressive properties of concrete at different curing ages was revealed.The addition of fiber enhances the compressive strength and axial compressive strength of concrete,improves the compressive pre-crack energy absorption,compressive energy absorption and compressive toughness index of concrete,reduces the degree of compression damage of concrete,improves the brittleness of concrete and increases its ductility.Based on the axial compression test of prisms,the uniaxial compressive stress-strain constitutive model of concrete with different curing age and different fiber content was proposed.(4)The effect of different polypropylene fiber content on the splitting properties of concrete at different curing ages was revealed.The addition of fiber enhances the splitting strength and flexural strength of concrete,improves the fracture energy and toughness of concrete,and proposes an equation for the relationship between splitting strength and compressive strength of polypropylene fiber reinforced concrete.In summary,the influence of fiber content on the mechanical properties and damage evolution characteristics of concrete at different curing ages is discussed.The stress-strain constitutive model in the relevant mechanical tests is proposed,which has important theoretical significance and practical value.