| Concrete is one of the most widely used and consumed building materials in the world except water.It not only has high compressive strength,good economic applicability and durability,but also can be easily processed into any shape.However,it is also a kind of porous brittle material with poor toughness and low tensile strength.Therefore,concrete cracks are one of the most common diseases of concrete buildings,especially under the action of external stress load,structural stress,deformation change,freeze-thaw cycle,wind erosion,high temperature and other conditions.Once concrete cracks appear,if they are not controlled in time,it is bound to speed up the invasion of harmful media into the concrete structure,which will gradually degrade the mechanical properties and durability of concrete structures,and eventually lead to damage of concrete structures and even complete loss of service functions.In other words,concrete cracks do great harm to the service life of bridges and concrete durability.According to the crack characteristics of concrete structure,it is very important to use appropriate materials to repair to ensure the bearing capacity of the structure.At present,epoxy resin structural adhesive stands out in the concrete crack reinforcement materials and becomes an indispensable material in the reinforcement technology.However,the poor construction performance,toughness and cracking resistance of epoxy resin limit its practical application.In order to develop high performance epoxy resin structural adhesive to deal with the problem of concrete cracking,in this paper,the chemical modification of the structural adhesive filler was carried out,and the epoxy resin was modified as a strengthening and toughening component.A kind of high-performance EP structure with thixotropy,high strength,rigidity and certain toughness was prepared,which could maintain a long construction life under high temperature environment Glue.Through formula design and indoor experiments,the basic mechanical properties,toughness and bonding properties of various structural adhesive materials are investigated and evaluated.Finally,the formula and technology of repairing materials with better performance are selected.The strengthening effect of concrete interface with cracks and high temperature damage is evaluated.The main research contents are as follows:(1)E51 epoxy resin was used as the main agent,aromatic amine(h-113)with high fluidity was used as main curing agent,low activity polyamide resin(PA)was used as auxiliary curing agent and toughening component.High active graphene(MGE)prepared by silane coupling agent(kh-792)was used as thixotropic component,and silicon powder,nano calcium carbonate and chopped carbon fiber were used as thickening agent A high performance EP structural adhesive with thixotropy,high strength,rigidity and certain toughness was prepared,which could maintain a long construction life under high temperature environment.The results show that the 1d compressive strength,14 d compressive strength,14 d tensile strength,14 d tensile strength and 14 d shear strength of the structural adhesive are 65 mpa,84mpa,32 Mpa and 17 Mpa respectively,and the normal tensile bond strength between the structural adhesive and concrete is 5.6mpa(the failure mode of interface is concrete cohesive failure).(2)Through the bending test of concrete beams with cracks strengthened by high performance structural adhesive,the strengthening effect and failure mode of high performance structural adhesive are studied.(3)The interfacial bond behavior of damaged concrete / resin was studied by three-point bending method.The interfacial bond separation constitutive curve was obtained.The fracture energy of the interface between high-temperature damaged concrete and high-performance structural adhesive was systematically studied. |
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