Polypropylene (C3H6) is a well-structured crystalline polymer. Polypropylene fiber is a new type of concrete hoisting fiber, which is called "secondary hoisting bar" of concrete. It is milky white, odorless, non-toxic, corrosion-resistant, hydrophobic and chemically stable. The key defect is poor dispersion and poor bonding strength with matrix. The toughness of concrete can be greatly improved by adding modified treatment. Occasionally, the strength index can be improved to improve the impermeability. Polypropylene Fiber Concrete (PPFC) is a new type of composite material which has been developed rapidly in recent years. It is widely used in water conservancy projects, urban transportation, urban planning and construction projects. It is understood that synthetic fiber reinforced concrete accounts for about 7% of the total concrete output used in the United States at this stage, which exceeds the steel fiber reinforced concrete (3%) of the previous scientific research. In this paper, the application of polypropylene fibers in concrete is analyzed based on the practice and current situation of scientific research and application of polypropylene fibers and concrete technology for many years, which is convenient for the application of polypropylene fibers in engineering projects.
2. Application of Polypropylene Fiber Concrete Technology
The research on polypropylene fiber reinforced concrete abroad can be traced back to the 1960s, when it was found that adding a small amount of polypropylene fibers in cement paste and mortar can significantly enhance its impact resistance. Since then, a small amount of short-cut polypropylene fibers (<0.05%) has been added to concrete to make pile shells in Britain. Wallboard, float and other prefabricated products. In 1970, the United States began to develop tow-to-tow polypropylene fibers as an alternative to adjusting the expansion of concrete. The key of domestic scientific research is focused on the research of physical and mechanical properties of polypropylene fiber reinforced concrete: Jiang Xuejie and other scientific research shows that the anti-seepage effect is related to the content of fibers. The larger the amount of fibers in a certain range, the better the effect. Considering the improvement of characteristics and economic cost, the volume ratio of industrial production and civil buildings is usually 0.1%. ~ 0.3% is more reasonable, the length of fibers is 19 mm to 30 mm; Huayuan and other scientific research shows that, compared with the reference concrete, the volume ratio of fibers increases (0-15%), the compressive strength of fibre concrete changes little, the flexural strength increases by 12%-26%, and the toughness also increases; Sun Jiaying scientific research shows that different amounts of polypropylene fibers are added. Dai Jianguo and Huang Chengkui have studied the construction characteristics, compressive, flexural, toughness, impermeability, thermal aging stability and expansion properties of reticulated polypropylene fiber reinforced concrete.