Study On Interfacial Characteristics Of Steel Deck Pavement With Engineered Cementitious Composites

The application of high ductility cement-based material ECC(engineered cementitious composite)on steel deck pavement with wet-bonding technology can greatly improve the stiffness of pavement structure,enhance its crack resistance and fatigue resistance,and prolong the service life.Wet-bonding technology can not only avoid the mechanical and maintenance defects caused by shear keys and other mechanical connections,but also has the advantages of economy and construction convenience.In this paper,the design and preparation of high ductility cementitious composites,the mechanical analysis of pavement structure and interfacial stress characteristics,the analysis of interfacial strength and fracture characteristics between steel bridge deck and ECC,and the improvement of self-healing and interfacial quality by adding light-burned magnesia and superabsorbent resin were studied.The main contents are as follows:(1)Based on the design principles of micro-mechanics and fracture mechanics,the domestic PVA fiber,quartz sand,Portland cement,fly ash and superplasticizer were used to prepare the ECC material with a large amount of fly ash.The intrinsic relationships between micro-structure and macro-performance were discussed and finally ECC with low cost and good ductility was developed.(2)The commercial finite element software ANSYS was used to establish a three-dimensional finite element model,calculate and analyze the mechanical response of steel deck pavement system under various working conditions.The stress state of bonding interface and the internal relationship between the design control index of pavement system and material parameters and structural parameters were explored.In addition,the single-layer pavement scheme and "ECC + asphalt concrete" double-layer pavement scheme were compared to provide guidance for the reasonable determination of the pavement structure.(3)For wet-bonding,there is water in the curing process and strength formation process of adhesives and ECC,and the interfacial properties are difficult to guarantee.A large number of laboratory tests such as pull-off test,single shear test and inclined shear test were used to evaluate the interfacial bonding properties of wet-bonding.The attenuation law of interfacial bonding properties under freeze-thaw and wet-heat conditions was discussed.The criterion of shear failure of wet-bonding interface under vertical loading was also established.(4)The double cantilever beam(DCB)and four-point end-notched flexure(4ENF)specimens were used for mode I and II fracture tests respectively,and the critical energy release rate was calculated by virtual crack closure technique.At the same time,the fracture criterion of mixed failure was established based on bister test.In addition,based on Workbench computing platform,a three-dimensional bidirectional fluid-solid coupling model was established to analyze the dynamic water pressure at the interface under load,and to explore the propagation mechanism of cracks under the water-loading interaction.(5)Light burnt magnesia and superabsorbent resin were added to ECC to reduce interface defects,improve the interface microstructure,and enhance the self-healing properties of ECC materials and the interface.Pressure seepage test,single shear test and electron microscopic observation were used to verify the improvement effect.