Feasibility Study on Using Magnesium Phosphate Cement for Repairing Bridge Expansion Joints
In order to verify the feasibility of Magnesium Phosphate Cement(MPC)in bridge expansion joint repair,its working performance is evaluated by the setting time and mechanical properties of MPC fast hardening high-strength mortar,and the pore structure of MPC mortar is detected by mercury intrusion method,and rapid chloride ion penetration test is conducted to evaluate its durability.The results indicate that the compressive strength of MPC mortar reaches its maximum value within 12 h.Among them,when the mass ratio of calcined magnesium oxide to potassium dihydrogen phosphate is 4.0,the maximum compressive strength of MPC mortar is 31.4 MPa,while the mortar prepared with Ordinary Portland Cement(OPC)is 4.2 MPa.At the same time,MPC mortar has better bonding performance with the repair surface,with higher tensile bonding strength and bending bonding strength of 1.9 MPa and 1.7 MPa,respectively,while OPC mortar has 1.5 MPa and 1.2 MPa,respectively.In addition,the pore type of MPC fast hardening high-strength mortar is mainly air pores,rather than capillary pores,therefore,compared to OPC mortar,MPC mortar shows lower permeability in electrical flux tests.Practical engineering applications have shown that the fast hardening and high-strength repair material prepared by MPC is superior to the repair material prepared by OPC.
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