WHY ARE EPOXY-COATED STEEL REBARS PROHIBITED IN BRIDGE STRUCTURES IN SOME REGIONS?

Abstract

One of the common ways in many countries to protect steel reinforcement from corrosion in reinforced concrete structures is to cover its surface with a thin layer of epoxy resin. However, in practice, in many cases, the anti-corrosion effect of epoxy coating was not significant, and the durability of reinforced con-crete bridge structures was lower than those where steel reinforcement was not coated with epoxy resin. Ex-perts believe that one of the factors that affects the corrosion resistance of steel reinforcement with epoxy coat-ing in reinforced concrete is the presence of mechanical damage in the epoxy coating of the reinforcing rod, through which moisture can penetrate. Therefore, in some countries, instructions have been developed for the prevention of such damage at the stages of applying an epoxy coating to the armature, its storage, transporta-tion, and construction and assembly work in the manufacture of reinforced concrete structures. This article discusses the thermomechanical mechanism of violation of the internal structural integrity of concrete rein-forced with steel rods with an epoxy coating, which is caused by a high value of its coefficient of linear thermal expansion and the epoxy coating itself. Using the methods of the theory of thermoelasticity, a mathematical model of this phenomenon was developed, a system of solving differential equations was formed, and its solu-tion was constructed. It was established that even with relatively minor temperature changes in the concrete environment in the area of its contact with the reinforcement, cracks and damages occur along the entire length of the steel reinforcement. All this contributes to further destructive processes and reducing the durabil-ity of reinforced concrete bridge structures.