Influence of Electrochemical Chloride Extraction on the Performance of Prestressed Concrete under Dynamic Loading Conditions

Abstract

One of the major causes of corrosion of reinforced concrete structures worldwide is chloride. With progressing corrosion, the integrity of the structure is at stake and repair measures are necessary. In recent years electrochemical repair methods such as chloride extraction or cathodic protection have become increasingly popular. Chloride extraction is less expensive as compared to traditional patch repair methods due to its short duration. It is accepted for application on ordinary concrete structures with mild steel reinforcement. Its application on prestressed concrete, however, has been ruled out because of the danger of hydrogen embrittlement. Contradicting results of research on the subject have suggested that chloride extraction might be a feasible repair option for prestressed concrete structures, thus leading to major cost savings for bridge owners. This study investigated the feasibility of chloride extraction on prestressed concrete structures. A distinction was made between hydrogen embrittlement, which temporarily reduces the ductility of steel, and hydrogen-induced stress corrosion cracking, which leads to sudden and unexpected collapse of the structure. The most commonly accepted test methods for hydrogen embrittlement are constant extension rate tests, but they give little indication of the performance of the prestressed tendons under serviceability conditions. In this study, along with constant extension rate tests, 22 prestressed concrete specimens were also tested using a fatigue test program. The fractured surfaces were carefully investigated to identify signs of hydrogen embrittlement and to rule out any other causes of failure. The results of the study suggest that chloride extraction temporarily reduces the fatigue life of prestressed steel. Although hydrogen-induced stress corrosion cracking was not observed for the type of steel investigated in the main study, it occurred for a different type of steel. Statistic analysis of the fatigue tests also suggested the possibility of hydrogen-induced stress corrosion cracking for the investigated steel; therefore, chloride extraction should not be applied to prestressed concrete structures.