Durability of polymer impregnated carbon textiles as CP anode for reinforced concrete

Asgharzadeh, Amir; Raupach, Michael (Thesis advisor); Zander, Brita Daniela (Thesis advisor)

Aachen (2019) [Dissertation / PhD Thesis]

Page(s): 1 Online-Ressource

Abstract

Damage to reinforced concrete structures causes immense economic losses every year. Costs due to failure of structures and their repair measures are immense. Much of this damage is due to the corrosive environment of reinforced concrete structures. One option for repairing corrosion-damaged components is cathodic corrosion protection. In cathodic corrosion protection, the reinforcing steel is forced to act cathodically and thus the dissolution of the reinforcing steel is reduced to harmless levels. The cathodic effect can be achieved for example by the attachment of an impressed current anode where the partial oxidation reactions are shifted to the external anode. Widely used in cathodic corrosion protection are mixed metal oxide (MMO) coated titanium meshes. Currently, the use of anodes made of carbon textile is being developed, which are of particular interest due to their excellent mechanical properties, low weight and crack bridging ability. Additionally, carbon textile is electrically conductive and its functionality as a CP anode has already been validated at the Institute of Building Materials Research (ibac) of the RWTH Aachen University. Carbon, according to the Pourbaix diagram , is not chemically resistant, and can corrode. Therefore, durability studies were required to determine the suitability of carbon as a long term anode material for cathodic protection of steel in concrete. The aim of this thesis is to investigate the durability of carbon textile under anodic polarization. The experiments were carried out using a simulated pore solution and mortar. The influence of anodic polarization on carbon textiles was investigated. The behavior of unconsumed carbon textile under anodic polarization in alkaline solution was characterized by current density-potential curves through potentiodynamic experiments. SEM images were used to detect decomposition of the sizing of the carbon filaments which was attributed to anodic polarization. Further tests in solution and further SEM images showed that impregnated carbon textiles degraded the epoxy and SBR impregnations. A degradation of the carbon fibers themselves could not be achieved for potentials up to 2200 mV vs. NHE. The decomposition of the sizing and epoxy matrix presumably occurs in the transition region of its current density-potential curves at potentials of about 900 mV vs. NHE and 1050-1150 mV vs. NHE. The SBR impregnation is decomposed at potentials of 490 mV vs. NHE. After 240 days of potentiostatic polarization, no visible damage has occurred to the mortar test specimens. However, the bond between carbon textiles and mortar as well as stress corrosion cracking of carbon textiles under anodic polarization was not investigated.

Identifier

  • REPORT NUMBER: RWTH-2019-05559

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