The Preparation And Properties Of Ultra-High Performance Magnesium Phosphate Cement Bridge Deck Pavement Material

Using ultra-high performance concrete(UHPC)as steel bridge pavement material can not only solve the problem of lack of asphalt resources in China and need to import a large amount of asphalt,but also significantly improve the service life of bridge deck pavement material.However,the preparation of UHPC with Portland cement as cementing material requires not only special maintenance measures,but also complex structure of bridge deck pavement,low early strength and long construction period.Therefore,the development of ultra-high toughness cement-based composite materials with high early strength and no maintenance as bridge deck pavement can significantly improve the construction efficiency of bridge deck pavement.Magnesium phosphate cement has the characteristics of fast setting and hardening speed and high early strength.When using MPC to prepare ultra-high performance concrete as bridge deck pavement material,there is no need for curing and it has very high early strength.However,the toughness of MPC is poor.Therefore,the paper systematically studies the influence of steel fiber length-diameter ratio,content of fly ash,glue set ratio and other factors on the physical and mechanical properties of magnesium phosphate cement concrete by using the synergistic strengthening and toughening effect of steel fiber and ultra-fine fly ash,and analyzes the influence mechanism of the above factors.It is expected to prepare ultra-high performance magnesium phosphate cement concrete with compressive strength greater than 60 MPa and 120 MPa for 6h and 28 d,and bending strength greater than 15 MPa and 25 MPa for 6h and 28 d.The results show that when the volume content of steel fiber is 2.5% and the volume content of fly ash is 5%,the 6h and 7d compressive strength of UHMPCC reaches82.3MPa and 107 MPa respectively,and the flexural strength reaches 18.3MPa and24.5MPa respectively.It is also helpful to improve the fluidity and mechanical properties of UHMPCC.The optimum M/P=3.5,W/C=0.14,B/M=0.05 for the preparation of UHMPCC.On this basis,according to the application requirements of bridge deck pavement materials,the mixture ratio of UHMPCC was optimized to prepare UHMPCC with 28 d bending strength of 25.2MPa and compressive strength of 114 MPa.The tensile strength,elastic modulus and bonding strength of UHMPCC with steel plate were tested.It provides basic data for UHMPCC used in bridge deck pavement.Using MPC preparation of steel bridge deck pavement material can give full play to the MPC high early strength,speed,condense sclerosis,and the advantages of high bonding strength with steel,will not only help speed up the construction of asphalt pavement layer materials,is expected to achieve the steel bridge deck pavement layer without rivet connection,the connection way to avoid conventional welding stud stress damage of steel bridge deck.