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Mochizuki N.,Nakabohtec Corrosion Protecting Co.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2010

There has been a growing demand of cathodic protection (CP) for the rehabilitation of salt damaged concrete structures. A brief introduction is given for the major CP systems used for concrete structure and the criteria of protection. In the present paper discussion is also given on the mechanism of protection, materials flow and electrical conduction within concrete, a solid system with low mobility and high electrical resistivity placed in atmosphere. Cathodic polarization protects steel reinforcement not only by shifting the metal potential in cathodic direction but also by modifying the environment factors favorable for steel protection such as an increase in pH and a decrease in chloride ion in the vicinity of metal surface resulting in protection conditions that satisfy the criteria. The environmental modification is thought to be the principal effect of CP. It is not seldom in concrete CP that a system that has been in operation below the criteria in the early stage would be changed to be satisfactory after long run owing to the modified environments. It is thus required to establish design and maintenance criteria in consideration of chronic changes.

Nanasawa A.,DenkI Kagaku Kogyo Kabushiki Kaisha | Kushida J.,Nakabohtec Corrosion Protecting Co. | Ueda T.,Tokushima University | Tsukagoshi M.,Tokushima University
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014 | Year: 2015

Chloride attack and ASR are serious deterioration mechanisms of concrete structures respectively. Moreover, in the cases of marine environment and cold climate area, complex deterioration of these mechanisms can be observed because of the supply of sea water or de-icing salt. In this study, as a remedial measure against such a complex deterioration, electrochemical penetration of lithium from the electrolyte solution was investigated. It was clarified that electrolyte temperature greatly affected the extent of lithium penetration and the treatment at 40 °C remarkably accelerated lithium penetration into concrete compared with the case of 30 °C. Regarding the kind of lithium salt, LiNO3 solution was most effective among a number of different kinds of lithium salt in the viewpoints of Li+ penetration of into concrete and suppression of concrete expansion. © 2015 Taylor & Francis Group, London.

Kobayashi H.,Port and Airport Research Institute | Yamaji T.,Port and Airport Research Institute | Akira Y.,Toyo Construction Co. | Hamada H.,Kyushu University | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

We investigated retrofit design in cathodic protection (CP) with galvanic anodes made from an aluminum alloy. In conventional retrofit design, the decrease in CP current reduction (which affects the life of anodes) is estimated based on nominal durability values. The current reduction rate falls to a level far below the design value, leading to an increased number of facilities in which the anode life exceeds the design service life. As this trend is due to exaggerated design, it is necessary to review retrofitting methods in order to enable more effective and economical maintenance. After detailed analysis and discussion, we developed an innovative methodology for an optimized maintenance system in galvanic anode CP. To test the assumptions made, we conducted on-site, shortterm testing with an actual structure and confirmed the validity of the new design methodology. The method, which takes current reduction into consideration, allowed more accurate prediction of anode life and a reduction in the initial costs of CP facilities.

Tanaka K.,Nakabohtec Corrosion Protecting Co. | Iwasaki T.,Kitacon Ltd.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2011

On the cathodic protection system for concrete structure, a galvanic anode system is recently highlighted as maintenance-free system. But, only some reports on the periodic or continuous monitoring of its performance can be found. The report covers the continuous monitoring of the performance on our galvanic anode system with "aluminum panel anodes", applied to the concrete highway bridge. The external view on the bridge was kept in initial condition for eight months after application. Although more positive ON potential of the rebar and lower output current of anode per unit rebar surface area were observed at lower ambient temperature, the rebar potential was kept in sufficient protection level.

Kobayashi H.,Port and Airport Research Institute | Akira Y.,Port and Airport Research Institute | Yamaji T.,Port and Airport Research Institute | Hamada H.,Kyushu University | And 2 more authors.
Zairyo to Kankyo/ Corrosion Engineering | Year: 2013

We investigated a cathodic protection design basis for reinforced concrete structures exposed to atmospheric conditions. If such structures in severely corrosive environments do not satisfy the relevant cathodic protection criteria, the situation can be remedied by supplying more current than the design value. However, as such energization results in rapid consumption of the water surrounding the anode, the voltage DC power supply may rise. Using electrochemical measurement and numerical simulation, we sought to clarify the effects resulting from environmental improvement of rebar surfaces using cathodic protection and devised a new design method. Then, via cathodic protection examination using concrete specimens affected by rebar corrosion, the validity of the new design method was determined. The approach was found to be suitable for economical and stable cathodic protection.

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