Corrosion of concrete reinforcement and electrochemical factors in concrete patch repair

Abstract

/npsi/ctrl?lang=en http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/ctrl?lang=fr Access and use of this website and the material on it are subject to the Terms and Conditions set forth at http://nparc.cisti-icist.nrc-cnrc.gc.ca/npsi/jsp/nparc_cp.jsp?lang=en NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://dx.doi.org/10.1139/L05-088Canadian Journal of Civil Engineering, 33, 6, pp. 785-793, 2006-06-01 Corrosion characteristics and key electrochemical factors in patch repair Zhang, J. Y.; Mailvaganam, N. P. Abstract: Corrosion of concrete reinforcement at a patch repair is a complex problem and the current knowledge of its mechanism is quite limited. This review has examined the correlation between two corrosion mechanisms, macrocell and microcell corrosion, from fundamental electrochemical principles. It was found that both mechanisms could play significant roles in inducing corrosion damage, contrary to the prevailing opinion that macrocell corrosion is the main deterioration mechanism in patch repair. This has practical implications that need to be considered for an effective and durable repair. A review of the studies done to date also enabled the identification of the key factors in patch repair controlling the corrosion characteristics.Corrosion could occur at different locations ⎯in the vicinity of the patch: substrate, interface, or patch area⎯ depending on the respective electrochemical environments induced by the repair material properties and treatments, as well as the in-service exposure and mechanical loading.The review indicates that much of the needed research should focus on identification of corrosion mechanisms in order to effect successful patch repair in reinforced concrete structures.

Cement-based mortar patch repair of RC columns. Comparison with all-four-sides and one-side repair

“…Later studies analysed patch repairs and considered other aspects such as shrinkage cracking [10,11], concrete-RM bond strength [12] and their influence on the efficiency and durability of the repairs. Some studies have specifically focused on patch repairs on corrosion-damaged RC structures, usually in aggressive environments, to avoid a repeat of the corrosion in the repair zone [13][14][15][16][17][18][19]. Some have analysed the influence of the shape and depth of the patch and emphasized that it must enclose the reinforcement in order to improve the load-bearing capacity of the repaired element [13][14][15][16][17][18][19].…”

Performance evaluation of patch repairs on historic concrete structures (PEPS): a bibliographic review of patch repair durability

“…As a major cause of repair failure, the corrosion process is widely studied in the context of patch repairs [25][26][27][28][29][30][45][46][47][48][49][50][51][52]. The electrochemical phenomena involved are addressed through the mechanism of incipient anode formation.…”

“…Like permeability, the concrete resistivity is a major factor that influences the magnitude of the macrocell corrosion [30]. A patch with high resistivity should diminish the incipient anode effect [5,26] as the material offers a high resistance to the rate of flow of the ions between the anode and cathode areas.…”

Modeling the kinetics of corrosion in concrete patch repairs and identification of governing parameters

“…The kinetics of macrocell corrosion ⎯ the corrosion current density and its distribution along the reinforcing bar ⎯ that directly leads to deterioration, however, are not well understood and very limited knowledge exists on the key factors that affect these key characteristics [14]. Understanding the distribution of the corrosion current density along the rebar is critical to predict the location and the severity of the corrosion damage.…”

“…Again, the precise identification of the source of the problem by experimental approaches will be limited by the geometry of experimental set-ups and of the capabilities of the corrosion measurement equipment. Therefore numerical modeling is considered as a suitable and useful tool to study the kinetics of reinforcement corrosion after patch repairs in concrete structures and to specifically address the following questions raised by Zhang and Mailvaganam [14] on the ring-anode effect: 1) is the anodic site after a patch repair at the interface or in the substrate? and 2) what are the anodic corrosion characteristics of the steel after patch repair with regards to its geometry and current density?…”