Study On Roughness Influence On The Interfacial Bond Performance Between CFRP And Concrete Under Harsh Environment

The strengthen technology of carbon fiber reinforce plastic(CFRP)and concrete ad been achieved rapid development in recent 30 years,many studies have shown the bond performance between the CFRP and concrete is the key parts of the composites and directly decided to performance of reinforcement.Harsh environment takes great impact on civil engineering materials,so it becomes the research hot spot for various countries' scholars.How much eroded of the interface between CFRP and concrete,how much degradated of the mechanical properties of the concrete structural element,and how influences of concrete surface roughness on bond performance between CFRP and concrete,some related research are to be carried out.This article is based on the mechanical properties and durability of concrete research,from the concrete surface roughness representation as the start point,based on domestic sand filled method to quantitative evaluation of concrete surface roughness.On the basis of a series of harsh environment under the roughness influence on the bond performance of CFRP and concrete,the main research work includes:(1)Roughness parameters affects on the performance of CFRP and concrete bonding interface under nondestructive environment were analyzed.In order to examine the roughness parameters influence on the bond performance between CFRP and concrete,druing the test procedure,6 kinds of concrete surface was differentiative made,and the sand filled method was adopted to quantify the rough surface,and then 216 CFRP-concrete interface single shear tests were completed,a relationship between shear stress and slip was proposed,the influences which the concrete surface roughness effect on was analyzed.The research results shows that concrete surface with different roughness can take different ultimate capacity load and bond strength;The effective bond length of CFRP to concrete beam is significantly increased from the view of roughness model,and it is declined with the roughness increases genernally;Interfacail bond strength,the corresponding slip and the ultimate slip are proposed based on the compress strength and interface roughness,and this method supports a new algorithm for the interfacial calculation.(2)Five kinds of harsh environments affects on the performance between CFRP and concrete based on the roughness parameters was discussed.Five kinds of harsh environment wer set up,there are harsh alkali environment,harsh sulfate environment,salt environment,salt cold environment,the high temperature environment,and the acid rain environment respectively.In order to evaluate the surface roughness influence on the performance between CFRP and concrete,378 concrete speicemens for single shear test and 78 specimens for pull off tests were made respectively,some indexes just like failure modes,interface roughness,environmental,ultimate load,the interfacial bond strength,maximum displacement,effective bond length and fracutrue energy were focused on.The research results shows that alkaline environment destroy little to epoxy resin,while seriously to concrete damage is;Under sulfate environment,epoxy resin can better protect the CFRP bond area;The interface bond performance shows the tendency of increase first after fall;Under salt freeze environment,interface normal bond strength between concrete and CFRP sheet is higher than interface between concrete and CFRP plate;The freeze-thaw cycle is a process of damage accumulation;Under the high temperature environment,the concrete surface roughness increase,the greater the bond strength is;Galss transition temperature is the key point to determine the interface bond decline performance between CFRP and concrete,some active measures should be taken to increase the galss transition temperature;Under acid rain erosion,the roughness is decision to interfacial failure mode,fracture energy increases with the concrete surface roughness increases,and increases first and reduces after with the corrosion time.(3)In order to improve the bonding performance between CFRP and concrete,from the two aspects of material modification,structure improvement,3 kinds of CFRP and concrete interfacial enhancement method were proposed.and based that proposed the roughness influence on the enhance interfacial action between CFRP and concrete;Nano kaolin through intercalating technology expoxy resin was modificated,to enhance the interfacial bond performance;By adopting the combination of macroscopic and microscopic test research methods,decentralized methods,dispersing time,dispersion were researched of this three factors to influences on the cement materials,modified cement was proposed to enhance the bond performance;Proposed the roughened CFRP sheet(RCFRP sheet)concept,to inspects the RCFRP sheet influences on the bond performance,analyze the interfacial enhancement mechanism,and stressed the key point that the strengthen concrete interface roughness should increased during the strengthen project.The research results shows that the dispersion performance is best of the 10%kaolin dosage for epoxy resin,the dosage of 10%kaolin epoxy resin,bond capacity is enhanced nearly four times,showed better bond ability;RCFRP can effectively enhance its wet bond performance between it and concrete surface,the particle size of volcano is the most important factor which influences on the wet interface bond between RCFRP and concrete;The reinforced beam surface treatment effect significantly on RCFRP reinforcement effect,we should treat reinforcement beam surface roughness,otherwise it easy to cause the bond failure between the new and old concrete surface;Polyacrylate polymer effects good on concrete cement materials linked and pore filled.