Analysis of the electrochemical phenomenon at the rebar–concrete interface using the electrochemical impedance spectroscopic technique
IR@CECRI: CSIR-Central Electrochemical Research Institute, Karaikudi
View Archive InfoField | Value | |
Title |
Analysis of the electrochemical phenomenon at the rebar–concrete interface using the electrochemical impedance spectroscopic technique
|
|
Creator |
Vedalakshmi, R.
Palaniswamy, N. |
|
Subject |
Corrosion Science and Engineering
|
|
Description |
The corrosion rate of rebar during the various stages where it occurs, such as passivation, initiation of corrosion
and severe corrosion, needs to be determined non-destructively for the maintenance, restoration and replacement of
concrete structures. The double layer capacitance (Cdl) and the charge transfer resistance or polarisation resistance
(Rp) of the corrosion processes have been associated with the slope of the low-frequency arc in the Nyquist plot,
and this can be related to the electrochemical phenomenon that occurs at the steel–concrete interface. The present
studies, based on electrochemical impedance spectroscopy (EIS) conducted on three different densities of concrete
with addition of 0.5 and 1% chloride over a period of 1765 days, reveal that the capacitive behaviour of a lowfrequency
arc with a slope more than �1 indicates the passive condition of rebar. Warburg diffusion behaviour with
a slope exactly equal to �1 denotes the initiation of corrosion on the rebar. A slope of less than �1 is obtained
when corrosion spreads uniformly on the rebar. Other electrochemical parameters such as Rp, Cdl and phase angle
are correlated with the phenomenon occurring at the steel–concrete interface. An Rp value greater than 250 k�
cm2 indicates the passive condition of rebar, whereas values of less than 230 and 14 k� cm2 indicate initiation and
severe corrosion of the rebar respectively. Similarly, a Cdl value greater than 1000 �F/cm2 indicates the severe
corrosion of rebar, whereas less than 100 �F/cm2 denotes the passive condition of rebar. If the rebar is in the
passive condition, the phase angle is more than 308, whereas it is less than 208 under severe corrosion. The
reduction of intrinsic chloride diffusivity owing to pore restructuring by pozzolanic reaction and adsorption of a
greater amount of chloride ions into the interlayer of additional calcium silicate hydrate content are responsible for
delayed initiation of corrosion in Portland pozzolana cement (PPC) and Portland slag cement (PSC) concretes,
when compared with ordinary Portland cement (OPC) concrete.
|
|
Publisher |
Thomas Telford Ltd
|
|
Date |
2010
|
|
Type |
Article
PeerReviewed |
|
Format |
application/pdf
|
|
Identifier |
http://cecri.csircentral.net/493/1/2010-107.pdf
Vedalakshmi, R. and Palaniswamy, N. (2010) Analysis of the electrochemical phenomenon at the rebar–concrete interface using the electrochemical impedance spectroscopic technique. Magazine of Concrete Research, 62 (3). pp. 177-189. ISSN 0024-9831 |
|
Relation |
http://cecri.csircentral.net/493/
|
|