| The crack of concrete has always been an important topic studied by academia and engineering circles,and it is one of the main manifestations of concrete diseases.At present,epoxy resin structural adhesive is widely used in concrete crack reinforcement because of its excellent adhesion and high hardness.However,due to the inherent brittleness and toughness of epoxy resin based materials and the characteristics of easy sagging at high temperature,it cannot meet the requirements of practical construction applications.Therefore,it is necessary to study the toughening modification of epoxy resin structural adhesive.In this paper,the toughening research of epoxy resin structural adhesive is carried out by modifying the surface of meteorological white carbon and using it as a toughening component and changing the filler composition of structural adhesive,so as to prepare a kind of epoxy resin structural adhesive with long construction applicability,high toughness Toughened and retarded EP structural adhesive(TR-EP)with high strength and thixotropy while maintaining a certain rigidity.The bonding performance and reinforcement effect of the structural adhesive concrete interface were characterized.The main research contents are as follows:(1)Preparation and characterization of modified meteorological white carbon black.Using meteorological white carbon black(SD)as raw material,the modified gaseous white carbon black(MSD)was prepared by reacting with silane coupling agent KH-792.MSD was characterized by IR and TEM.The results showed that after MSD modification,the organic hydrophobic group of KH-792 was successfully grafted,and the hydrophobicity and dispersion in epoxy matrix were improved.(2)Preparation and characterization of TR-EP structural adhesive.The prepared TR-EP structural adhesive is a and B two-component system.Component A: main agent E51 epoxy resin;Thixotropic agent MSD;Thickening and reinforcing fillers: ultrafine quartz sand,nano calcium carbonate and chopped carbon fiber;Modifier silane coupling agent KH-792.Component B: main curing agent T-31 phenolic amine;Auxiliary curing agent and toughening agent PA polyamide.The tensile section of TR-EP structural adhesive was observed and discussed by SEM,and the relevant indexes of mechanical properties and construction performance of TR-EP structure were determined according to gb50728-2011 and other standards.The results showed that TR-EP structural adhesive had a 1D compressive strength of62 mpa,a 14 d compressive strength of 81 mpa,a 14 d tensile strength of 34 mpa,a 14 d shear strength of 18.5 MPa,and a tensile bonding strength of 5.5mpa.(3)Through the three-point bending test of concrete beams with cracks strengthened with toughened and retarded structural adhesive under different strengthening methods and different FRP sheets,the double-K fracture parameters,fracture energy and ductility index of reinforced concrete notched beams are calculated respectively,and the strengthening effect of toughened and retarded structural adhesive TR-EP on reinforced concrete notched beams is evaluated according to the calculation results and failure mode.The results show that compared with ordinary epoxy resin adhesive O-EP,TR-EP can significantly improve the bonding strength of the structural adhesive concrete interface and has a better reinforcement effect in the glue pouring method and the externally bonded FRP method;The combination of CFRP and TR-EP is the best combination.According to the failure mode and tensile bond strength of 16 groups of80 tensile specimens,the reinforcement effect of toughened and retarded structural adhesive TR-EP in different curing environments and combined with different FRP sheets was evaluated.By analyzing the micro bonding mechanism of the interface between structural adhesive and concrete under normal tension,the micro mechanical model of the interface between structural adhesive and concrete under normal tension is derived.The results show that under the above two conditions,TR-EP improves the tensile bond strength of the specimens better than ordinary epoxy resin O-EP;The wet environment will cause the tensile bond strength of the specimen to decrease significantly.TR-EP is less sensitive to the wet environment because of its high hydrophobicity.In the wet curing environment,the decrease of the tensile bond strength is significantly smaller. |
PDF Full Text Request