On the limitations of predicting the ohmic resistance in a macro-cell in mortar from bulk resistivity measurements

Hornbostel, Karla; Angst, Ueli; Elsener, Bernhard; Larsen, Claus

doi:10.1016/j.cemconres.2015.05.023

Cited by 23 publications

(15 citation statements)

References 13 publications

(19 reference statements)

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“…[118][119][120] This can be explained by the heterogeneity in local microstructure and environment at the steel/ soil and steel/concrete interface. [121][122][123] Particularly in aerated soils where steel surfaces are only partially wetted or where the thickness of the contacting electrolyte layer is variable, 124 there is a high probability for establishing differential aeration cells within short distances. As was early illustrated in the famous Evans droplet experiment and later summarized by Pourbaix, 125 this differential aeration "produces an increase in the corrosion rate in the non-aerated regions, and a decrease in the corrosion rate in the aerated regions."…”

Section: The Question Of Heterogeneous Corrosion Conditionsmentioning

confidence: 99%

A Critical Review of the Science and Engineering of Cathodic Protection of Steel in Soil and Concrete

Angst¹

2019

Corrosion

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After a century of history of cathodic protection (CP) of iron and steel, this paper critically reviews the state of the art in the science and engineering and assesses the fitness of CP as an effective technology to tackle the challenges related to infrastructure corrosion. This paper focuses on CP of iron-based alloys embedded in porous media, such as soil or concrete, as these two major applications of CP technology share many similarities. First, the scientific understanding of CP is reviewed and different competing theories are discussed. There is wide agreement that corrosion protection of steel is achieved thanks to a combination of immediate activation polarization and the beneficial changes in electrolyte chemistry that are gradually occurring at the steel surface when a protection current is flowing toward a steel electrode. A major and well-documented technological advantage of these "chemical effects" is that the protective effect of CP is maintained during temporal loss of protection current, e.g., due to survey work related shut-offs or anodic interference. However, the relationships between these chemical concentration changes in the porous medium and the protection current are complex, and, as this review shows, cannot reliably be described with state-of-the-art approaches. Moreover, in this paper, different hypotheses for the mechanism of corrosion protection in heterogeneous situations (galvanic elements), as they are generally occurring in practice, are discussed. It is revealed that understanding the working mechanism of CP in heterogeneous conditions remains a critical scientific challenge. The longstanding debate concerns the question whether CP results mainly in a reduction of number and size of actively corroding areas, or in a reduction of the corrosion rate at the actively corroding sites. Additionally, the literature addressing the interrelation between microbiologically influenced corrosion and CP is here reviewed, and recent progress as well as limitations of the existing literature are highlighted. In a second part, engineering practice and CP protection criteria are reviewed. It is found that the approaches stipulated in international standard are unreliable. This can be traced back to the assessment criteria being empirical and incapable of adequately taking into account the complexity of the underlying processes. Finally, recommendations for future developments are made. Particular opportunities are seen in embracing the progress made in numerical modeling, such as reactive transport modeling in porous media, and considering the interdependence between the involved processes, namely the interdependence between transport processes, chemical reactions, and electrode kinetics.

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Section: The Question Of Heterogeneous Corrosion Conditionsmentioning

confidence: 99%

A Critical Review of the Science and Engineering of Cathodic Protection of Steel in Soil and Concrete

Angst¹

2019

Corrosion

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“…This may be explained by the pronounced concrete inhomogeneity, particularly at the length scale of the studied coating defects. The presence or absence of aggregate particles in close vicinity of the defects strongly affect the ohmic resistance of the coating defects .…”

Section: Resultsmentioning

confidence: 99%

Epoxy‐coated reinforcement in concrete structures: Results of a Swiss pilot project after 24 years of field exposure

Keßler¹,

Angst

Zintel³

et al. 2016

Materials & Corrosion

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Reinforced concrete is the most common construction material of civil infrastructure. In severe environment, e.g., chloride exposure, concrete deterioration can occur with consequences on the durability of the structure. The use of epoxy‐coated reinforcement is a strategy to control chloride‐induced reinforcement corrosion, particular by prolonging the initiation and propagation phase. The epoxy‐coating acts as a physical barrier to chlorides and the electrolyte concrete. However, the effectiveness of the strategy in chloride environment and the corrosion performance of ECR in presence of coating defects is investigated by condition assessment of a Swiss pilot project after 24 years of field exposure.

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“…“cell resistance”), the respective electrical properties of the inhomogeneities are of great importance. This was investigated in an experimental study conducted by the present authors, where dimensions comparable to the presented study were used. It was found that the cell resistance is not directly correlated to the bulk resistivity, a fact which was explained by the influence of possible inhomogeneities located in front of the simulated anodes.…”

Section: Discussionmentioning

confidence: 99%

Limitations of the use of concrete bulk resistivity as an indicator for the rate of chloride‐induced macro‐cell corrosion

Hornbostel

Elsener

Angst

et al. 2017

Structural Concrete

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An experimental setup was designed to study the impact of concrete bulk resistivity on the rate of chloride‐induced reinforcement corrosion. Small pieces of mild steel were used to simulate pits (anodes) that form when chlorides come into contact with the reinforcement. The galvanic current was measured between the simulated anodes and a large cathode network. Comparisons were made between the corrosion rates calculated from the galvanic currents and the bulk resistivity. The bulk resistivity was varied using two mortar mixes (made of plain Portland cement and a Portland cement—fly ash blend), which were exposed in different temperature and moisture conditions. Despite a high scatter in the results, it was clear that the relationship between bulk resistivity and corrosion rate depended on the mortars tested. The findings presented in this article and the accompanying work strongly indicate that bulk resistivity alone does not provide sufficient information for assessment of the corrosion rate for chloride‐induced macro‐cell corrosion.

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On the limitations of predicting the ohmic resistance in a macro-cell in mortar from bulk resistivity measurements

Cited by 23 publications

References 13 publications

A Critical Review of the Science and Engineering of Cathodic Protection of Steel in Soil and Concrete

A Critical Review of the Science and Engineering of Cathodic Protection of Steel in Soil and Concrete

Epoxy‐coated reinforcement in concrete structures: Results of a Swiss pilot project after 24 years of field exposure

Limitations of the use of concrete bulk resistivity as an indicator for the rate of chloride‐induced macro‐cell corrosion

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