| Asphalt concrete is widely used in freeway, runway of airport, bridge pavement, and the roads of the city. Currently, the breakage of asphalt concrete pavement in China is still a serious problem. In order to monitor the damage of the asphalt pavement and manage the Intelligent Transportation System to prolong the service life of asphalt concrete pavement, a new multi-functional material-polyaniline compound conductive fiber blended asphalt concrete was investigated in the paper, in which the polyaniline compound conductive fiber mixed as electric conduction material. The design of the asphalt concrete was based on the SMA (Stone Mastic Asphalt) -16 discontinuous grade gradation. The paper was supported by "the research of polyaniline/polypropylene conductive fiber concretes compound materials" of the Science and Technology Funding Project of Liaoning Province and "the research of polyaniline/polypropylene electric conduction complex fiber" of the Education Departmentn of Liaoning Province Project.Preparing polyaniline/polypropylene compound conductive fiber through the in-situ polymerization synthesis and using aniline as a monomer and polypropylene fiber as a matrix. The optimal reaction condition could be gotten from the experimental results: the density of hydrochloric acid is 0.6 mol/L, the content of aniline monomer is 90 %; the density of oxidant is 0.02 g/mL; the reaction time is 2 h; the reaction temperature is below 20℃. Moreover, the polyaniline can form continuous electric conductive deposited coating on the surface of the matrix fiber as its content reaches 2.5 %, and the conductivity of the fiber can increase from 10-13S/cm to 10-1S/cm.The structure and the property of the polyaniline/polypropylene compound conductive fiber were examined by using infrared spectrum (FT-IR), scanning electron microscope (SEM), thermogravimetric analysis (TGA), optical microscope, and tensile test. The results show that the compound conductive fiber has typical structure of sheath-core consists of black greened polyaniline electric conductive deposition as the skin and the white polypropylene matrix fiber as the core, which makes the compound fiber preferable physical mechanical property. The intensity and the elongation ratio of the electric conductive fiber are decreased but the thermal stability is enhanced after modified. The compound fiber has the good acid resistance but poor base resistance. The thermal stability of the compound fiber prepared by 4-methyl-benzene sulfonic acid (organic acid) is better than that prepared by hydrochloride acid (inorganic acid). Moreover, the compound fiber can be re-doped by other organic or inorganic acid after freed from the adsorbed acid. Furthermore, the electric conductivity of the compound fiber decreases with the temperature increasing but hardly changed with the humidity. The adsorptive ability and therefore the content of the polyaniline, the constant of electric conduction, and the durability of the compound fiber can be enhanced by thinning the diameter, section heteromorphosis, section heteromorphosis and plasma treatment of the surface or blending with COPET of the fiber. The content of polyaniline of the fiber is 7.9 %, the constant of electric conduction is 0.17 S/cm and unchangeable for more than 6 months, and the washing times in water is more than 55 after plasma treatment of the fiber surface.The mechanical properties of the asphalt concrete mixed with and without compound fiber were examined through Marshall Method. The result show that the mechanical property of the asphalt concrete intermingled with polyaniline compound fiber was enhanced. When the fiber dispersed uniformly, the Marshall stability, the flow value, the air voids ratio, and the voids filled of the asphalt concrete increase with the content of the compound fiber increasing. On the degree of enhancing the mechanical property of the bituminous mixture, the four things rank in turn from high to low are mixed PANI/PP and PANI/PET fibers, the PANI/PP compound conductive fiber, the PANI/PET compound conductive fiber, the polypropylene fiber, and the polyester fiber. It is obviously that stability of the asphalt concrete intermingled with polyaniline compound fiber is better than that with polyaniline compound fiber, which shows the different trends comparing with the mechanical property of the conductive fiber after conduction modified.The electric conductivity of the asphalt concrete intermingled with polyaniline compound fiber is improved. The experimental results indicate that the constant electric conductivity of the asphalt concrete with the transfusion threshold of 0.2 % is increased by 5～6 power. When the compound fiber dispersed uniformly, the conductivity of the asphalt concrete modified with the fiber of 12 mm in length is better than that of 6 mm in length. Moreover, the electric conductivity of the asphalt concrete can be increased an order magnitude when the carbon black and the compound fiber mixture blended simultaneously in the asphalt concrete.The electrical conductivity of the asphalt concrete is stable over time. The examination of the susceptivities of press and temperature of the asphalt concrete indicated that the electric conductivity of samples increased with the press increasing with a degressive acceleration and finally reached the electrical conductivity of compound fiber. Moreover, the constant electrical conductivity of the asphalt concrete increased slowly with the temperature increasing, which presented a normal temperature effect. The mechanism of the electric conduction of the asphalt concrete can be explained by using electric channels and tunnel effect in which a net factor, n, which indicates the capability of conductive net formation in the concrete. Combined with the transfusion theory, a type of sea-island model is proposed.Based on the systematical analysis of the dispersivity of the compound fiber, the mechanical property, and the electric conductivity of the asphalt concrete, the optimal content of the compound fiber is 0.2～0.4 %.
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