A review of utilization of carbon fibers as an anodic material in cathodic protection

Author(s): M. Chini, R. Antonsen, Ø. Vennesland, B. Arntsen, J. H. Mork
Paper category: Workshop
Book title: International RILEM Workshop on Integral Service Life Modelling of Concrete Structures
Editor(s): R.M. Ferreira, J. Gulikers, C. Andrade
Print ISBN: 978-2-35158-058-5
e-ISBN: 978-2-35158-090-5
Publisher: RILEM Publications SARL
Pages: 395 - 402
Total Pages: 8
Language: English

A literature review has been made on deterioration of carbon fibers embedded in concrete or subjected to alkaline solutions. The main emphasis of this work is to evaluate carbon used as anode material in cathodic protection systems for reinforced concrete structures.
Anodes for impressed current systems may be installed as mesh or by strips embedded in shotcrete on the surface on concrete structures with ongoing reinforcement corrosion. For such systems a widely used anode is titanium covered with metal oxides. However, continuous research are carried out in order to reduce cost of anode systems and to improve application techniques such as using conductive coatings and paintings. In this regard, carbon fiber meshes have been introduced as an alternative anode material and have been used as anode meshes for the last decade. Some practical experiences seem to indicate that carbon is insignificantly affected by degradation.
The sustainability and lifetime of CP systems are often dependent upon degradation of the anode material. In concrete the anode material must withstand increased anodic polarization in alkaline media. According to Pourbaix diagram, carbon is not stable in pH values for normal concrete. Thermodynamically carbon will dissolve into either gaseous derivates such as CO2, CO, CH4, or into dissolved substances like carbonic acid, bicarbonate and carbonate.
Unfortunately, scientific work and publications concerning electrochemical properties of carbon embedded in concrete are scarce. Some studies on carbon fiber behavior on different applied potentials exist which mostly were aimed to study the life span of carbon as anode material. These investigations showed that polarization above a critical potential about 1.8 V vs. corrosion potential leads to accelerated corrosion. Hence, accelerated tests on available industrial carbon fiber meshes indicate proper life time where working potential of the anodes are held below the critical potential limit.
Ongoing research sponsored by the Norwegian Research Council and directed by Norut Teknologi was established in order to evaluate the electrochemical properties of carbon fibers in concrete. The work is carried out by studies of thermodynamics and kinetics of carbon in alkaline solution and concrete media.

Keywords: Cathodic protection, Carbon fiber, corrosion, concrete

Online publication: 2013
Publication Type: full_text
Public price (Euros): 0.00

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