The effect of corrosion and high temperature on the physico-mechanical properties of reinforced concrete steels

The main objective of this study was to investigate the reinforced concrete components under high temperature exposure and corrosion condition. For this reason, concrete samples, which have three different compression strength, were produced. S220a, S420a and S500a reinforced concrete steels were used. 12, 16 and 20 mm bar diameter were chosen. Three different corrosion condition; noncorrosive, corrosion with constant period and corrosion until concrete crack formed, were chosen to determine the corrosion effect. Corrosion current and period of reinforced concrete samples were considered with accelerated corrosion mechanism. Furthermore, corrosion potential, corrosion rate, bond strength, SEM and EDX studies were performed on the samples. 100, 200, 400, 600, 800 and 1000 °C temperatures for were selected for high temperature conditions. Compressive, tension strengths under bending, ultrasonic sound velocity, bulk density, porosity, water absorption, loss on ignition, dynamic elasticity modulus and heat transfer measurements depending on the bar cover were carried out. Pull out test, impact toughness, oxide layer measurement, micro hardness and investigation of micro structure were performed on steel samples. In addition, a measuring of bond strength was carried out for all of the temperature conditions.Higher bond strengths were measured with increase in the concrete strength in normal condition and also in high temperature and corrosion conditions. Formation of corrosion products increased the bond strength of S220a class non-ribbed steel as compared to normal condition, on the other hand decrease in the bond strength was measured in S420a and S500a ribbed steels. All of the sample series were affected negatively from increasing of temperature; nevertheless bond strengths of the samples were increased slightly at 100 oC. It was concluded that, the differences in the micro structures of S420a and S500a steels which were the some surface structure, the main reason for the difference in the bond strengths under high temperature and corrosion condition.According to the results of this study, S500a is recommended in terms of physico-mechanical properties under normal conditions. S420a steel is recommended because exhibit balanced exchange in corrosion and high temperature conditions.