| In the reinforcement of degraded concrete structures,the interface agent is an indispensable important binder,but the ordinary interface agents are mainly cement?sand?pulp or net?sand?slurry mixed with expansion agent,the bonding performance is weak,often Failures to meet the reinforcement requirements,the development of new and efficient interface agents is a hot topic in the current industry.In recent years,research on interface agents has been limited to bond mechanical strength,and less to durability,resulting in a large number of reinforcing projects occur frequently shortly after completion.In this paper,a new experimental modified epoxy interface agent is used to carry out the mechanical test and durability test,and the engineering application effect is analyzed.The main research contents and conclusions are as follows:?1?In the mechanical properties test,five sets of splitting tensile test and oblique shear test of new and old concrete bonded specimens under different interface agents?modified epoxy,cement paste,cement slurry,no interface agent?and different interface roughness are respectively carried out.The results show that in the splitting tensile test,when the bonding surface is the ramen,the splitting tensile strength of bonded specimens with modified epoxy interfacial agent is higher than that of bonded specimens with cement slurry interfacial agent or without interfacial agent.When the bonding surface is a glossy surface,the splitting tensile strength of bonded specimens with modified epoxy interfacial agent is close to that of bonded specimens with cement expansion on splitting tensile surface.In the oblique shear test,when the bonding surface is notched,the oblique shear strength of the bonding specimens with modified epoxy interfacial agent is much higher than that of the bonding specimens with other types of interfacial agent.When the bonding surface is smooth,the oblique shear strength of the bonding specimens with modified epoxy interfacial agent is still higher than that of the bonding specimens with other types of interfacial agent on the notched surface.?2?In the durability test,the effects of modified epoxy interface agent and cement paste interface agent on the durability of new and old concrete bonded specimens are studied Through 28 groups of new and old concrete bonded antifreeze test,4 groups of new and old concrete bonded Impermeability test and 2 groups of interface agent anti-carbonization test.The results show that during the whole freeze-thaw cycle,the tensile strength of new and old concrete bonded specimens and bulk specimens decreases slowly with the increase of freeze-thaw cycles.The tensile strength of modified epoxy bonded specimens is always higher than the cement paste bonding test piece,and the tensile strength of the modified epoxy bonded test piece after 35 freeze-thaw cycles is15.7%higher than that of the cement paste bonded test piece.The water pressure is0.8MPa under constant pressure for 24h,and the relative permeability coefficient of the new and old concrete bonded test piece and the body test piece is between 2.3×10-5cm/h and 3.4×10-7cm/h.The permeability is one order of magnitude higher than that of the bulk test piece,and the permeability of the modified epoxy bonded test piece is41.4%of the cement paste bonded test piece.Under the standard carbonization conditions,the depth of carbonization of concrete under modified epoxy coating is only2mm,which is 20.9%of the concrete carbonation depth covered by cement paste in the same period.?3?The microstructure analysis of new and old concrete bonded specimens with modified epoxy,cement paste,cement slug and no interface agent on splitting surface is respectively carried out to study its influence mechanism.The results show that the modified epoxy interface agent is better combined with new and old concrete,and compared with other interface agents,the crack width of the transition zone between the old and new concrete interface is greatly reduced.?4?In the actual project,the application process of modified epoxy interface agent is designed,which can provide guidance for similar projects. |
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