Compatibility Of Repair Materials With The Existing Substrate In Concrete Structure Repair

The deterioration of the existing concrete structure is a common issue in actualprojects, repair and reinforcement is becoming a promising industry. Although therepair materials and repair crafts is improved fast, many problems which causes therepair failure exist in the actual projects. One of the problems which cause theconcrete structure repair failure is the compatibility of the repair materials andconcrete of the existing structure. The compatibility can be defined as a balance ofphysical, chemical, electrochemical and dimension between a repair material andexisting substrate that will ensure that the repair can withstand all the stress inducedby volume changes and chemical and electrochemical effects without distress anddeterioration over a designated period of time.In this paper, the properties of the repair materials and other factors whichinfluence on dimension compatibility, mechanic compatibility and electrochemicalcompatibility is studied by theory analysis, mechanical calculations and experiments.A mechanic model is established to predictive the dimension compatibility. Lastlysome suggestions are proposed for concrete structure repair.The study shows:(1) The factors which influent the dimension compatibility includes shrinkage strain,modulus, dimension, thermal expansion coefficient, ambient temperature andstrength of substrate.The greater the shrinkage of the repair material is, the worsethe dimension compatibility is. The greater the thermal expansion coefficient ofthe repair material is, the worse the dimension compatibility is. The greater thelength of patch is, the worse the dimension compatibility is. The influence ofthickness is based on the selection of material, for polymer material, the thinnerthe thickness is, the better the dimension compatibility is, Conversely, the thinnerthe thickness is, the better the dimension compatibility is. The greater the changein the ambient temperature is, the worse the dimension compatibility is.(2) The factors which influents the mechanical compatibility of repair materialsmainly include strength, modulus and creep. The notable factor is modulus.Foraxial compression members, when the externally applied load is essentiallyparallel to the bond line, the larger the differences in the elastic modulus ofconcrete matrix and repair material, the lower the intensity of enhanced andutilization is. The higher the strength of concrete matrix is, the higher the utilization of repair material is. The inconsistence of creed will lead to stressredistribution and reduce the carrying capacity. Conversely, in repairs where theservice load stresses are perpendicular to the bond line, the influence of creep andelastic modulus can be overlooked, but the strength has big influence on theutilization, the higher the strength of repair materials is, the lower the utilizationis.(3) The factors which influents the electrochemical compatibility mainly includeresistivity and permeability. If the discharge of the permeability of repairmaterials and substrate concrete is large, it maybe cause macro-corrosion andaccelerate the corrosion of steel. But high resistivity can slow corrosion.(4) The consideration of concrete structure repair must be integrated in customerdemand, technology, environment, economic, function and other factors. Theproperties of repair materials and substrate must be compatibility.