Abstract
The present study concerns the influence of cementitious binder on electrochemical treatment of steel embedded in salt contaminated mortar. As binder, ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBS) were used and the current density of 250–750 mA/m2 was applied for 4 weeks to complete electrochemical chloride extraction. To evaluate the effect of electrochemical treatment the chloride profile and corrosion behaviour covering chloride concentration, galvanic current density, linear polarization resistance, open circuit potential, and mass loss were measured. An increase in the applied direct current density resulted in a decrease in the chloride concentration at the vicinity of steel, accompanying the mitigated corrosion damage. The performance of electrochemical treatment was more remarkable in mortar containing GGBS presumably due to binding mechanism. However, corrosion damage was more detrimental in GGBS rather than OPC at a given potential, while GGBS had superior corrosion resistance to a corrosive environment and treatment conditions. Therefore, the electrochemical treatment should be conducted prudently to evaluate the corrosion state of embedded steel depending on binder type.
Highlights
Chloride ions in steel reinforced concrete structure have been considered as the most aggressive factor of degradation process associated with steel corrosion, thereby leading to reduction in structural serviceability
On the other hand, reduced chloride concentrations were always higher in ground granulated blast furnace slag (GGBS) compared with ordinary Portland cement (OPC) at all the current densities
The efficiency of electrochemical treatment for GGBS was anticipated to be worse than OPC due to the higher binding capacity, whereas the results showed the reversed tendency
Summary
Chloride ions in steel reinforced concrete structure have been considered as the most aggressive factor of degradation process associated with steel corrosion, thereby leading to reduction in structural serviceability. To enhance the direct corrosion resistance of the concrete made with the pozzolanic materials after long term degradation proceeds, few researches according to the electrochemical chloride extraction treatment for concrete made with supplementary cements have been performed [8]. The influence of binder types, consisting of sole OPC and blending cement with GGBS, on the removal of initially contained chlorides from the inside of steel reinforced mortars and the resultant corrosion rehabilitation was evaluated by measuring polarization resistance and corrosion potential under variation of cathodic current densities between 250 and 750 mA/m2. The amount of corrosion products was determined by measuring mass loss of corroded steel in order to find the relationships between cathode current density and rate of corrosion process From these works, it was possible to determine the corrosion resistance of GGBS based cementitious material. Air content (%) 3.1–4.5 under variation of cathodic current densities and to assess its efficiency of enhancing the durability by cathodic protection
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