1. Overview

        In all kinds of fiber reinforced concrete, because the polypropylene fibers have high quality, inexpensive, stable nature, lunch and other construction interests, which makes polypropylene fiber reinforced concrete is widely used in the international military, housing construction, transportation, water conservancy project. China since the mid-1980s, in the basement, sewage treatment pond, highway pavement in high-rise buildings and other projects are gradually initial use of polypropylene fiber reinforced concrete. Bridge Engineering, was also first and foremost is to be used in the bridge deck to its terms.

        2. function polypropylene fiber reinforced concrete

       Polypropylene fiber is a polypropylene primary material, together with the production process is made of high-strength fiber bundles. Polypropylene is a crystalline polymer having excellent heat resistance, it does not dissolve in water, and most of the chemicals (such as acids, bases and organic solvents) the effects of contact does not occur; polypropylene excellent physical and mechanical function, its anti- tensile strength of about 33.0 ~ 41.4MPa. Incorporation of polypropylene fibers in concrete can therefore use monofilament fibers can also be so reticular fibers. The primary function of polypropylene fiber reinforced concrete below.

        2.1 Excellent crack function and impermeability function

        At that time, the mechanism of fiber reinforced concrete cracking function of only some beginning assumption is generally believed that the primary role of fiber is bound to expand the micro-crack bridging effect by then to improve the function of the concrete. By mixing concrete polypropylene fiber distribution in the concrete evenly and makes the ends of the fibers appear somewhat bent. On the one hand fiber distribution in concrete acts similar to mesh together hooked fibers can withstand a tensile stress of concrete deformation, cracks may hinder further expanded. Many mutual coupling fiber aggregate occur supporting role, restraint analysis of water and aggregate concrete surface subsidence, can effectively reduce the occurrence of plastic cracks of concrete. Therefore, polypropylene fiber reinforced concrete with excellent crack function, especially for pre-shortened restraint concrete cracks have a significant role. Doped polypropylene fibers, can be reduced to shorten the fracture, and then reduce the seepage channel. Followed by incorporation to increase the amount of fiber, the space inside the concrete content will be greatly reduced. These elements make polypropylene fiber reinforced concrete impermeability function can greatly advance. Domestic and foreign research conclusions test proved incorporation of polypropylene fibers can be made of concrete impermeability function forward about 25% to 45%.

        2.2 outstanding impact function and anti-fatigue function inside a concrete layer of polypropylene fibers to support the effect of chaos concrete help advance energy shock absorption. Because polypropylene larger ductility (elongation of 200% to 700%), fiber, low load transfer in the interior of concrete ability, can effectively reduce some of the stress that occurs due to mutations in the energy micro-cracks in concrete at the rendezvous appearance, You can then forward concrete plan useful impact function. Fatigue is due to being rich material under repeated loading tension components, micro-cracks within the material from germination to widen to run through until the cracking process constitutes the cracks. Concrete planning its internal microcracks material will be prevalent at the time, the incorporation of polypropylene fibers can make native cracks inside the concrete specification is reduced, reducing the number; together, the presence of fibers can join steepness crack tip stress reduction small crack under repeated loading area widened during the plastic composition, and can effectively reduce fatigue damage accumulation planning to increase the number of fatigue life.

         2.3 excellent wear function polypropylene fibers per m tens of millions of people to the number of mixed concrete, its overlap with each other, implicated in the mess inside the concrete constitutes a uniform system to support hampered due to the impact or wear Cracks occurred unfold. Fiber also manipulate pieces of concrete falling from the matrix of the concrete pieces fall need to consume more energy from the matrix, and then forward the wear and function of the concrete. Polypropylene fiber reinforced concrete also has excellent resistance to freeze-thaw resistance, corrosion resistance and improve concrete characteristics of brittleness.

        3. discuss the function of crack resistance of polypropylene fiber concrete in the bridge test panel discussion crack resistance of a bridge in the process, carried out on polypropylene concrete shorten and shorten test for determination of work-related stress analysis, the effect of concrete proof polypropylene Concrete bridge planning function has good crack resistance.