Article

Determination of the distribution of electrical resistivity in reinforced concrete structures using electrical resistivity tomography

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Abstract

Concrete resistivity is an important durability related material parameter. It correlates with various properties, e.g., the reinforcement corrosion rate, the water saturation degree and the porosity. The resistivity is typically determined on a structure by using the Wenner probe. Unfortunately the results can strongly be influenced by heterogeneities, e.g., reinforcement bars or inhomogeneous moisture distributions. Neglecting these effects can lead to significant misinterpretations. In order to consider these influences quantitatively the applicability of the electrical resistivity tomography (ERT) on reinforced concrete has been studied. The aim of the method is to determine the distribution of the concrete resistivity perpendicular to the concrete surface. Based on this data the spatial distribution of material properties can be derived and the influence of an inhomogeneous resistivity distribution on the corrosion rate of the reinforcement can be studied. ERT can be applied to determine the resistivity distribution of reinforced concrete within certain resolution limits. Within this work the influence of different electrode configurations and rebar positions as well as the improvement of the resolution by considering prior information are exemplarily shown. Compared to the Wenner configuration the resolution and accuracy can be improved significantly with dipole–dipole measurements.

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... However, assessing these parameters on-site is time consuming, expensive and/or requires destructive tests. Resistivity is being increasingly considered as a reliable durability index for assessing the long-term performance of reinforced concrete structures [2][3][4]. ...
... Eq. (3) is applied for homogeneous semi-infinite volumes. However, experiments have indicated that sample size and the presence of steel bar(s) can lead to erroneous results [4,[20][21][22] and these aspects have to be considered carefully to obtain the correct resistivity value [7]. Both two-electrode and Wenner methods use alternating current in order to prevent the polarization of the metal electrodes. ...
... RE and CE resistivity was 10 À5 X.m. Different rebar diameters were modelled (4,8,16, 32 and 50 mm). Concrete cover ranged between 1 and 160 mm. ...
... The concrete resistivity measured as presented in the above sections corresponds to an ''apparent" resistivity that considers all elements in the investigated area. Therefore, this value only reflects an average value on a defined volume and does not consider the inherent heterogeneity of concrete [347]. A multielectrode device, consisting of an assemblage of single devices with four electrodes, can be used to perform an electrical resistivity tomography (ERT) of the concrete [347,348]. ...
... Therefore, this value only reflects an average value on a defined volume and does not consider the inherent heterogeneity of concrete [347]. A multielectrode device, consisting of an assemblage of single devices with four electrodes, can be used to perform an electrical resistivity tomography (ERT) of the concrete [347,348]. With such method, it is possible to determine the resistivity at different levels/depths in order to reconstruct the spatial distribution of the resistivity in the material (Fig. 10). ...
... If the highest sensitivity arrays are found near the potential electrodes, the measured potential difference differs depending on the probe configuration [349]. Thus, using several probe configurations and probe spacing, complementary data may be obtained to assess the different corrosion states on a single rebar [347]. ...
Article
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Steel corrosion is the main cause of deterioration of reinforced concrete (RC) structures. We provide an up-to-date review on corrosion mechanisms and recent advances in electrical methods for corrosion monitoring. When assessing corrosion mechanism, the inherent heterogeneity of RC structures and the significant effect of environmental factors remain major issues in data interpretations. The steel surface condition and local inhomogeneities at the steel–concrete interface appear to have an important effect on corrosion initiation. Considering uniform corrosion in atmospherically exposed RC structures, the two main influencing factors of the corrosion process are the water content and the pore structure at the steel–concrete interface. However, irrespective of the depassivation mechanism, i.e. carbonation or chloride-induced corrosion, non-uniform corrosion is expected to be the main process for RC structures due to local variations in environmental exposure or the presence of interconnected rebars with different properties. Future studies may then be focused on their effect on macrocell corrosion to gain further insights in the corrosion mechanisms of RC structures. Concerning corrosion monitoring using electrical methods, the half-cell potential technique with potential mapping is accurate for locating areas with a high corrosion risk. Recent developments in the measurement of concrete resistivity have shown that the use of electrical resistivity tomography allows to consider appropriately the inherent heterogeneity of concrete and provides more insights on transport phenomena (e.g. water and salts ingress) in the material. Nevertheless, during the corrosion propagation stage, the polarization resistance remains the most important parameter to be determined as it provides quantitative information of the corrosion rate. If conventional three-electrode configuration methods can supply an accurate determination in the case of uniform corrosion, they often fail in the case of macrocell corrosion in field experiments. Recent advances have shown that a four-electrode configuration without any connection to the rebar can rather be used for the non-destructive testing and evaluation of corrosion. If studies are still required to quantify the corrosion rate, this method appears sensitive to localized corrosion and thus more suitable to field investigations. Finally, the coupling of numerical simulations with complementary electrical and other non-destructive testing methods is essential for consolidating the results to provide a better diagnosis of the service life of RC structures.
... The value of soil electrical resistivity is usually estimated based on the injected current, the measured electrical potential, and the value of the geometrical coefficient which mainly depends on the arrangement of electrodes and test equipment (Scollar et al. 1990;Kearey et al. 2002;Tang et al. 2018). It can be used to measure the distribution of soil resistivity at various distances and depths by rearranging the electrode setup (Reichling et al. 2015). However, the application of this method in small-scale tests is limited due to the arrangement of the four electrodes. ...
... Besides, the arrangement of four electrodes in the soil is over complicated due to the small size of the studied soil sample and the specialized cylindrical container. Therefore, a two-electrode method was applied in this study (Reichling et al. 2015;Samson et al. 2018). ...
Article
Drought-induced evaporation can reduce soil water content and significantly alter soil hydro-mechanical behavior. Understanding the temporal and spatial distribution characteristics of soil water content during evaporation is of great significance for evaluating the encountered geotechnical and geo-environmental problems in arid or semi-arid regions. In this study, an electrical resistivity/resistance method (ERM) with a high spatial resolution of centimeter-level was developed for a small-scale laboratory test and applied to quantitatively characterize the evaporation-induced water content variations along a depth gradient. A total of 8 groups of initially saturated sandy soil columns (84 mm in diameter and 290 mm in height) were prepared, and eight pairs of mini electrodes (3.5 mm in diameter) were installed in each soil sample with a vertical distance of 30 mm. The soil columns were subjected to continuous drying. The changes in soil electrical resistance at different depths were monitored by the electrode couples. The gravimetric water contents at different depths were also measured at the end of drying. It is found that soil water content decreases exponentially with increasing electrical resistance. Based on the obtained data, a calibration relationship between soil gravimetric water content and corrected electrical resistance was well established with the consideration of temperature effect. This relationship was validated successfully by the experimental results, indicating the feasibility of the developed ERM to characterize the soil water content dynamics during the drying process. Besides, the drying process with the movement of the evaporation front was discussed. The results of this study demonstrate the good performance of ERM in the estimation of temporal and spatial variations of soil water content and its potential application in arid or semi-arid regions with frequent droughts.
... A technique that is already used for structural concrete monitoring to identify and locate steel rebars is the electric resistivity measurement (see, e.g., [27][28][29][30][31][32]. Based on an easyto-use test setup, which was already tested in past studies conducted by the authors [33], a new application test based on the analysis of cylindrical specimens is proposed in this research paper. ...
... This effect is already described in several studies (see, e.g., [42][43][44][45]). In addition, as a result of the storage conditions, the drying process of the concrete itself takes place, which results in a lower pore saturation and thus, also increases the electrical resistivity of the concrete (see, e.g., [31,46,47]). Since the aging effect seems to be almost constant for all fibre contents with an increase in resistivity of about 50%, it can be stated that the age or condition of the concrete must be identified to enable a prediction of the fibre content, while the fibre orientation, vertical and horizontal, can be estimated independent of the concrete. ...
Article
Full-text available
The diagnostics of constructions built with steel fibre reinforced concrete are extremely difficult to conduct because, typically, no information on the actual amount and orientation of the fibres is available. Therefore, it is of great interest to engineers to have the possibility to determine the steel fibre content and, at best, also the orientation of the fibres in existing structures. For this purpose, an easy-to-use test setup was developed and tested, in the course of laboratory investigations. This method can be used for cylinders, for example drilling cores, that can later be taken of existing structures, to determine both the fibre content and orientation. Based on these results, a model for cylindrical specimens was derived, which can be used for varying concrete compositions with steel fibre contents of up to 80 kg/m3. In the case of missing information concerning the concrete composition, it allows an initial estimation for the fibre content. In case additional information about the concrete composition is available, a much higher accuracy of the projected steel fibre content and therefore, an assessment of the building’s condition is possible.
... In cover concrete, resistivity depends on the concrete formulation, age, porosity (Karhunen et al., 2010;Whittington et al., 1981) and on its water content or saturation degree (Archie, 1942;Woelfl and Lauer, 1979). These indicators can be assessed using calibration tools (du Plooy et al., 2013;Villain et al., 2018) to give information about the durability of concrete structures (du Plooy et al., 2015;Gowers and Millard, 1999;Lataste et al., 2008;Polder, 2001;Reichling et al., 2015;Sbartai et al., 2007). Vertical Electrical Sounding (VES) approache has been intensively developed in the field of near surface geophysics for the last three decades (Loke et al., 2013). ...
... Data acquisition procedures are based on multielectrode layouts and data processing approaches are based on the inversion of measured data to allow the reconstruction of a 'true' resistivity distribution (Loke and Barker, 1996). It should be emphasized that the applications of electrical methods to cover concrete investigation are more recent and still scarce (du Plooy et al., 2013(du Plooy et al., , 2015Karhunen et al., 2010;Reichling et al., 2015;Villain et al., 2015b). ...
Article
Geophysical techniques offer assessing conditions of reinforced concrete structures without invasiveness issues. Electrical Resistivity methods are promising tools for evaluating parameters such as water and ionic contents of concrete in reinforced concrete structures. In order to obtain water content profiles due to water ingress, the actual challenge consists in evaluating the 1D-resistivity profile with depth in concrete. To reach this goal, 1D-inversion procedures improving the extraction of true resistivity profiles in concrete are proposed. The first procedure, considered more conventional, is based on a discrete parameterization of the medium with three parameters. The second procedure is based on a continuous parameterization function defined with four parameters. We invert synthetic profiles to test the procedures and we study the effect of data noise on the inversion results. At last, an experimental validation on concrete slabs is carried out by comparing four different saturation degree profiles extracted from measurements or obtained by reference measurements. Results show that the continuous parameterization is able to accurately retrieve several profiles but that the resolution of the resistivity profile is limited by the maximum inter electrode spacing.
... La présence d'acier, même dans son état passif, peut perturber les mesures de résistivité électrique, l'acier étant un bien meilleur conducteur électrique que la phase liquide dans le béton, la résistivité apparente mesurée au voisinage des armatures est plus faible que la résistivité réelle du béton ausculté. Différents auteurs ont cité l'importance de l'influence de l'acier sur la mesure de résistivité électrique dans une structure en béton armé (Millard, 1991;Polder et al., 2000;Bungey et al., 2006;Reichling et al., 2015;Nguyen et al., 2017). Lataste et al. (2003b) ont rapporté que les barres d'acier influencent la mesure de résistivité et recommandent d'effectuer la mesure loin de l'armature pour réduire le plus possible son impact ; un éloignement de 2 fois l'espacement entre électrodes donne des erreurs inférieures à 5%, et un éloignement de 3,5 fois permet de négliger l'effet du biais. ...
... permettent de développer une nouvelle méthodologie d'évaluation de la résistivité du béton d'enrobage en utilisant la réponse instantanée de polarisation de l'armature métallique.Dans ce travail, deux méthodes de modélisation des armatures métalliques seront testées dans le chapitre 4 :la « conduction », l'armature étant modélisée par un matériau plein conducteur avec une résistivité de l'acier de l'ordre 10 -6 Ω.m(Reichling et al., 2015;Alhajj et al., 2019), la condition de « Butler-Volmer » (expliquée ci-dessous) qui permet de rendre compte des phénomènes électrochimiques dus à la corrosion et où les barres d'acier sont simulées comme des tubes creux, à la surface desquels la densité de courant est contrôlée par l'équation de Butler-Volmer (équation 3.10)(Laurens et al., 2016).La corrosion de l'acier dans le béton est traduite par un transfert de charges à l'interface acierbéton. L'acier et l'électrolyte forment une pile électrochimique. ...
Thesis
La résistivité électrique est un paramètre sensible à différentes propriétés du béton, dont la teneur en eau qui est l'un des principaux indicateurs gouvernant sa durabilité. Dans cette étude, la problématique du suivi du profil de teneur en eau du béton sur toute son épaisseur est abordée en utilisant une méthode électrique à courant continu comme méthode de mesure. Cette problématique revêt une grande importance pour les structures de stockage en béton utilisées pour les déchets radioactifs et pour les applications nécessitant une résolution spatiale centimétrique de la mesure du profil de teneur en eau sur une grande épaisseur. L'objectif de cette thèse est de concevoir et de réaliser des capteurs multi-électrodes noyés dans des structures en béton pour évaluer le profil de résistivité dans leur épaisseur afin de remonter au profil de teneur en eau. L'étude porte sur la conception de deux capteurs (Echelle et Anneau) sous la forme de circuits imprimés, ce qui présente plusieurs avantages, en particulier la précision géométrique et la limitation de l'encombrement des câblages afin d'une part d'augmenter la durabilité des capteurs et d'autre part de réduire leur caractère invasif. Différentes configurations de mesure sont analysées et comparées. Une modélisation numérique de la réponse électrique des capteurs et de leur capacité à évaluer un profil de résistivité imposé est réalisée ainsi que l'influence des armatures métalliques sur la réponse des capteurs placés au centre de la maille d'armature. Des validations expérimentales à la fois dans des solutions salines de conductivité connue et sur des échantillons de béton soumis au séchage sont également mises en œuvre. Les résultats démontrent la capacité des capteurs à évaluer les profils de résistivité dans le béton avec une résolution centimétrique. Pour changer d'échelle et s'approcher des conditions de mesure sur des structures réelles, les capteurs sont intégrés dans deux dalles de béton armé de 30 cm d'épaisseur instrumentées par d'autres capteurs afin de comparer les résultats. Enfin, une calibration des mesures est réalisée pour remonter au profil de teneur en eau en tenant compte de la température. Les profils de degré de saturation obtenus avec les capteurs innovants développés dans cette thèse sont encadrés par les profils obtenus par des mesures de référence (capteurs thermohygrométriques THR et gammadensimétrie) et donnent des résultats cohérents avec l'évolution due au séchage du béton.
... tomography [80][81][82]. However, the use of only two electrodes for a given measurement corresponds to the two-probe method, which is not reliable due to the inclusion of the contact resistance associated with each electrode. ...
Article
Full-text available
Piezoresistivity is an electromechanical effect characterized by the reversible change in the electrical resistivity with strain. It is useful for electrical-resistance-based strain/stress sensing. The resistivity can be the volumetric, interfacial or surface resistivity, though the volumetric resistivity is most meaningful scientifically. Because the irreversible resistivity change (due to damage or an irreversible microstructural change) adds to the reversible change that occurs at lower strains, the inclusion of the irreversible effect makes the piezoresistivity appear stronger than the inherent effect. This paper focuses on the inherent piezoresistivity that occurs without irreversible resistivity changes. The effect is described by the gage factor (GF), which is defined as the fractional change in resistance per unit strain. The GF can be positive or negative. Strong piezoresistivity involves the magnitude of the fractional change in resistivity much exceeding the strain magnitude. The reversible effect of strain on the electrical connectivity is the primary piezoresistivity mechanism. Giant piezoresistivity is characterized by GF ≥ 500. This critical review with 209 references covers the theory, mechanisms, methodology and status of piezoresistivity, and provides the first review of the emerging field of giant piezoresistivity. Piezoresistivity is exhibited by electrically conductive materials, particularly metals, carbons and composite materials with conductive fillers and nonconductive matrices. They include functional and structural materials. Piezoresistivity enables structural materials to be self-sensing. Unfortunately, GF was incorrectly or unreliably reported in a substantial fraction of the publications, due to the pitfalls systematically presented here. The most common pitfall involves using the two-probe method for the resistance measurement.
... During this period, other researchers were also using ET for clarifying a large suite of different questions in concrete materials and structures. Some examples of additional works between 2010 and 2015 include localizing steel reinforcement using linear surface electrodes [133], conceptualizing the broad usage of ERT in NDT as a whole [134], and investigating ET with adaptive meshing for crack detection [135]. The specific usage of ET for characterizing transport properties in cement-based materials began to take hold in 2015 with the work published by Hallaji and coauthors [43], where the authors were the first to corroborate 2D unsaturated flow imaged with ERT with another 2D modality, neutron radiography. ...
Article
Full-text available
The ability to spatially and temporally quantify the state and distribution of moisture and ions is of central importance to understanding the durability of cement-based materials and structures. Owing to the heterogeneous nature of concrete and challenges associated with using point-based measurements in accomplishing such a task, the use of two- and three-dimensional tomography for quantifying transport properties has become the source of much research interest. Distinct from electromagnetic radiation-based modalities -- Electrical Tomography (ET), including Electrical Resistance Tomography, Electrical Impedance Tomography, and Electrical Capacitance Tomography, has emerged as a viable means for characterizing transport in cement-based materials. In this work, we provide a technical overview of ET and the nature of ET inverse problems. We also review historical challenges and successes of ET for imaging transport properties in cement-based materials.Based on realizations from the review, challenges and opportunities afforded by ET for characterizing transport properties are provided and discussed.
... Another interesting method is the use of a carbon black filler for increasing the electrical conductivity of the polymer matrix to employ ERT for glass fiber/epoxy laminates [25][26][27][28] . The use of ERT for SHM / NDT purposes can also be found in the case of concrete structures [29][30][31][32][33] . ...
Article
Electrical resistance tomography is a method for sensing the spatial distribution of electrical conductivity. Therefore, this type of tomography is suitable for sensing damages, which affect electrical conductivity. The utilization of resistance tomography for the structural health monitoring of carbon fiber–reinforced polymer composites is questionable owing to its low spatial resolution and the strong anisotropy of carbon fiber–reinforced polymer composites. This article deals with the employment of resistance tomography with regularization based on a Gaussian anisotropic smoothing filter for the detection of cuts. The advantages of the filter are shown through the image reconstruction of rectangular composite specimens with three different laminate stacking sequences. The cuts are implemented by a milled groove. Visual comparison of the images shows a substantial improvement in the shape reconstruction ability. In addition to visual comparison, the image reconstructions are assessed in terms of the reconstruction error and cross-correlation.
... Electrical resistance tomography (ERT) is another method that allows non-destructive 3D visualization of moisture ingress and structural inhomogeneity (such as cracks, embedded rebar) in concrete from surface measurements [133][134][135][136][137]. The method is based on passing alternating currents through the specimen and measuring the resulting potential differences using an array of surface-mounted electrodes. ...
Article
Full-text available
The steel–concrete interface (SCI) is a complex, multi-phase and multi-scale system. It is widely known to influence the performance and long-term durability of concrete structures. However, a fundamental understanding of its properties and effects on corrosion initiation of embedded reinforcing steel remains elusive. This is attributed to its complicated heterogeneity and time-dependent nature, exacerbated by the lack of suitable techniques for systematic and detailed characterisation. This paper, prepared by members of the RILEM Technical Committee 262-SCI, critically reviews available information regarding current methods (laboratory or field-based) for characterising local properties of the SCI that have been identified as governing factors affecting corrosion initiation. These properties include characteristics of the steel such as mill scale and rust layers, and characteristics of the concrete such as interfacial voids, microstructure and moisture content. We evaluated over twenty methods and summarised their advantages, applications and limitations. The findings show a severe lack of well established, non-destructive techniques that are suitable for direct monitoring of the SCI at a representative scale with sufficiently high resolution (spatial, temporal), particularly for moisture related aspects. Several promising novel techniques with significant potential for further development and application were identified and discussed. Finally, we provide several recommendations for future research needs that are required to advance this critically important topic.
... Though, in our study, concrete resistivity is assumed homogeneously distributed in the concrete domain, we must recall that concrete is inherently heterogeneous by nature. To consider this point, an electrical resistivity tomography (ERT) is necessary [96,97]. Such measurements are generally done with a multi-electrode device for determining first the apparent resistivities at specific depths in the concrete volume. ...
Article
Full-text available
The use of indirect electrical techniques is gaining interest for monitoring the corrosion of steel in concrete as they do not require any connection to the rebar. In this paper, we provide insights into the physical aspects of the indirect galvanostatic pulse (GP) method in the Wenner configuration. Considering uniform corrosion, the instantaneous ohmic drop is decreased due to the presence of the rebar, which acts as a short-circuit. However, we observed that this phenomenon is independent of the electrochemical parameters of the Butler–Volmer equation. They are, however, responsible for the nonlinear decrease of the current that polarizes the rebar over time, especially for a passive rebar due to its high polarization resistance. This evolution of the resulting potential difference with time is explained by the increase of the potential difference related to concrete resistance and the global decrease of the potential difference related to the polarization resistance of the rebar. The indirect GP technique is then fundamentally different than the conventional one in three-electrode configuration, as here the steady-state potential is not only representative of polarization resistance but also of concrete resistance. Considering non-uniform corrosion, the presence of a small anodic area disturbs the current distribution in the material. This is essentially due to the different capability of anodic and cathodic areas to consume the impressed current, resulting in slowing down the evolution of the transient potential as compared to uniform corrosion. Hence, highly corroding areas have a greater effect on the transient potential than on the steady-state one. The use of this temporal evolution is thus recommended to qualitatively detect anodic areas. For the estimation of their length and position, which is one of the main current problematic issue when performing any measurement on reinforced concrete (RC) structures with conventional techniques, we suggest adjusting the probe spacing to modulate the sensitivity of the technique.
... The presence of steel reinforcement can disturb the electrical resistivity measurements, due to the fact that steel is a much better electrical conductor than the liquid phase in concrete. Various authors have cited the importance of steel's influence on the electrical resistivity measurement in a reinforced concrete structure (Millard, 1991;Polder et al., 2000;Bungey et al. 2006, Reichling et al., 2015Alhajj et al., 2019;Villain et al., 2020). ...
... Surface electrical resistivity of concrete is one of the key durability performance indicators for evaluation of reinforcement corrosion in concrete. It provides additional information on current material and structure condition, but also enables to predict remaining service life of structures [75][76][77][78][79]. The device used for the measurement is based on the Wenner probe technique with alpha configuration, where four electrodes are in contact with the concrete surface (Figure 4c). ...
Conference Paper
Existing bridge maintenance policy, where bridge assessment is based on results of visual inspection is not sufficient since reinforcement corrosion, as the main degradation process of concrete bridges, cannot be timely detected. Hence, new approach, where visual inspection is combined with simple, rapid and cost-effective non-destructive testing (NDT) is presented and demonstrated on the case study: Adriatic Bridge across Sava River in Zagreb. NDT on the bridges includes crack detection, determination of geometry and crack cause identification, estimation of strength and dynamic elastic modulus of concrete, rebar detection, measurements of rebar diameter, concrete cover, electrical resistivity of concrete and half-cell potential. Application of NDT increases the objectivity of the visual inspection results and allows detection of invisible defects, what was confirmed by additional destructive testing on the case study. Utilization of results obtained by visual inspection and NDTs in numerical models for service life prediction of structure is discussed, highlighting the importance of inclusion of performance indicators variation due to non-uniformity of concrete quality (local cracks, damage).
... The degree of water saturation of the pore structure of the concrete, the porosity and the conductivity of the pore solution are the most relevant influencing factors for the electrical resistivity of concrete (e.g., [26,[36][37][38]). Nevertheless, it should be considered, that the influence of the pore solution chemistry is relatively small, unless extreme drying and carbonating effects take place. ...
Article
Full-text available
This paper presents a systematic study of the electrical resistivity of different steel fibre-reinforced concretes with fibre contents from 0 kg/m3 to 80 kg/m3 in order to identify possible effects of interactions among concrete composition and fibre type and content regarding electrical resistivity. Based on a literature review, four parameters, w/c ratio, binder content, ground granulated blast-furnace slag (GGBS) and fineness of cement, which show a significant influence on the electrical resistivity of plain concrete, were identified, and their influence on the electrical resistivity as well as interaction effects were investigated. The results of the experiments highlight that the addition of fibres leads to a significant decrease in electrical resistivity, independent of all additional parameters of the concrete composition. Additionally, it was shown that a higher porosity of the concrete, e.g., due to a higher w/c ratio, also results in a lower electrical resistivity. These results are in agreement with the literature review on plain concrete, while the influence of the concrete composition on the electrical resistivity is weaker with the increase in fibre content. The influence of fibre reinforcement is thus not affected by changes in the concrete composition. In general, a higher fibre dosage leads to a decrease in electrical resistivity, but the impact on the electrical resistivity varies slightly with different types of steel fibres. Based on this study, the potential of determining the fibre content using electrical resistivity measurements could be clearly presented.
... For example, electrical resistivity is very high in dry conditions, and, for the same concrete, it will be very low in fully saturated conditions [69]. Reichling et al. [118] agree that the electrical resistivity depends on the pore structure and the distribution of the concentration of ions in the liquid. In this perspective, drying the concrete will result in an increasing electrical resistivity. ...
Article
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The objective of this study is to review, evaluate, and compare the existing research and practices on electrical resistivity as a nondestructive technique in evaluating chloride-induced deterioration of reinforced concrete elements in buildings and civil infrastructure systems. First, this paper summarizes the different measurement techniques for gathering electrical resistivity (ER) values on concrete. Second, comparison analyses are performed to review the correlation of ER to different parameters representing corrosive environment and activity of steel corrosion in concrete, such as degree of water saturation, chloride penetration and diffusivity, and corrosion rate. In addition, this research enumerates and individually discusses the different environmental and interference factors that are not related to the electrochemical process of steel corrosion in concrete but directly affect the ER measurements, including temperature, the presence of steel reinforcement, cracks and delamination defects, specimen geometry, and concrete composition. Lastly and most importantly, discussions are made to determine the current gap of knowledge, to improve the utilization of this method in field and laboratory measurements, and future research.
... Electrical resistivity measurements are currently used for the monitoring of the corrosion behavior of steel rebars in concrete elements using multiringelectrodes (see, e.g., Refs. [55][56][57][58][59]. By extending this idea, the objective of this study is to develop a test setup that can be adapted on nearly all types of concrete elements and can be used for in situ measurements on SFRC buildings (see, e.g., Refs. ...
Article
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Although steel fiber reinforced concrete is becoming increasingly popular in the construction industry, its application is currently limited to certain areas. One reason is the lack of an economical non‐destructive testing method to determine the content, distribution, and orientation of steel fibers in fresh and hardened concrete. However, these parameters are decisive for the assessment of the static performance of a building component. In this article a new test method is proposed, which is based on the electrical conductivity of concrete. Using a two‐electrode experimental set‐up, measurements of the electrical conductivity were done on hardened concrete cubes with defined fiber content and a correlation between electrical conductivity and fiber content could be identified. Within the scope of extensive test series, the fiber content and the age of specimens were varied, and several identical series were produced and observed to ensure statistically verified results. At this stage of research the test method based on electrical conductivity measurement provides reliable results on the fiber content of preconditioned concrete cubes. Based on the results a new model was developed to quantify the fiber content of the examined cubes. This model is based on the estimation of the relative conductivity, the so‐called increase of conductivity. Undesired influences caused by aging, respectively hydration in the young concrete age were eliminated, by relating the conductivity of fiber reinforced concrete to an unreinforced concrete. Further investigations with focus on the influence of concrete composition and other specimen sizes are going to be conducted as next steps for the development of an in situ test setup for the diagnosis of concrete structures.
... Surface electrical resistivity of concrete is one of the key durability performance indicators for evaluation of reinforcement corrosion in concrete. It provides additional information on current material and structure condition, but also enables to predict remaining service life of structures [75][76][77][78][79]. The device used for the measurement is based on the Wenner probe technique with alpha configuration, where four electrodes are in contact with the concrete surface (Figure 4c). ...
Article
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Assessment of reinforcement corrosion and concrete damage on bridges using non-destructive testing Management of bridges in Croatia and their vulnerability to reinforcement corrosion is discussed in the paper. New maintenance approach, where visual inspections are combined with the non-destructive testing methods, is proposed and demonstrated on six representative bridges. Using this methodology, reinforcement corrosion on structural elements may be detected earlier and more precisely. Obtained results as well as correlations between different measured parameters are important input parameters for prediction of future degradation of structures and decision making for future maintenance activity.
Article
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A new probe, which does not use a confinement ring, has been developed to assess the corrosion state of reinforced concrete structures. Galvanostatic polarization is performed and the rebar corrosion potential, concrete cover resistivity and rebar corrosion rate are evaluated using an iterative calculation algorithm. The surface linear polarization resistance (RP,s = ΔEP/jPI) of the rebar / concrete interface is calculated by converting the potential measured at the surface ΔEP,surf into the rebar polarization ΔEP and the current density at the point of interest (PI) jPI using 3D numerical simulations. The calculation involves three geometrical parameters that modify the current and potential distribution in the concrete: the rebar spacing, s; the concrete cover, c; and the rebar diameter, D. Concrete cover resistivity is calculated using the instantaneous ohmic drop measured at the beginning of the galvanostatic polarization and the rebar corrosion rate is calculated using the steady-state potential. As the rebar corrosion rate also modifies the potential distribution in concrete, an iterative methodology was developed, using different supposed corrosion rates. Finally, the probe and associated methodology were used to evaluate the corrosion state of eight concrete slabs. Half of them were prepared with chloride in order to initiate corrosion. Four slabs were stored outdoors, two indoors in an ordinary laboratory environment and two indoors in a 50% CO2 gas chamber. The three corrosion parameters evaluated (corrosion potential, concrete cover resistivity and rebar corrosion rate) were in good agreement with the composition of the slabs and their curing conditions.
Thesis
Nous proposons une nouvelle procédure de mesure permettant de tracer la courbe de résistivité en fonction de l'écartement électrode de courant-électrode de potentiel relié à la profondeur d'investigation et au gradient de teneur en eau. Les mesures de résistivité au droit des armatures sont réalisées et une procédure d'inversion permettant de remonter au gradient de résistivité est mise en place. Deux types de mesures ont été effectués expérimentalement, sur des dalles en béton armé et non armée. Deux types de gradient sont étudiés : le séchage et l'humidification. La présence de l'armature diminue significativement la résistivité à cause d'un effet de court-circuit. Les mesures montrent l'intérêt de la procédure pour l'étude du gradient de teneur en eau. Pour la partie numérique la simulation a montré que la mesure de résistivité permet effectivement de déterminer le gradient de résistivité et de définir les paramètres électrochimiques de l'acier via le modèle de Butler-Volmer.
Article
Full-text available
Measuring electrical resistivity is becoming a desirable method for evaluating the material property in cement-based materials. As a rapid nondestructive technique, measurement of resistivity is frequently performed both in laboratory specimens and on-site structures. Alternating current (AC)/potential-based methods are common approaches to measure the resistivity in cement-based materials. The alternating perturbation amplitudes applied range from several millivolts to even volts. However, how the perturbation amplitude influences the results and determining the optimal frequency and perturbation amplitude are still in question. In the present study, AC resistance measurements using electrochemical impedance spectroscopy were performed on cement-based specimens with different compositions. To investigate the effect of perturbation amplitude on the measured resistance, different amplitudes of potential perturbation varying from 5 mV up to 1,000 mV were applied. The reliability of data was evaluated by the harmonic analyses. Results indicated that, as the resistivity of specimens increased, a slight decrease in the fR (i.e., the frequency at which the ohmic resistance is measured) was observed. Noticeably, significant scatter in fR was demonstrated by applying different potential perturbations, especially for amplitudes lower than 50 mV. In terms of the perturbation amplitude, the results of resistivity were generally maintained in a relatively small variation when the potential perturbation was higher than 100 mV. Based on harmonic analyses, the appropriate frequency and perturbation amplitude for measuring the resistance of cement-based materials were determined.
Article
de Das Ermüdungsverhalten von Betonstahl, Spannstahl und Beton ist in den letzten Jahrzehnten immer stärker in den Fokus der Wissenschaft geraten. Neben den stetig steigenden Anforderungen an zum Beispiel Brückenbauwerke und Windenergieanlagen, die längere Lebensdauern und dadurch höhere Anzahlen an Belastungszyklen fordern, werden neue Konstruktionen immer filigraner und schlanker unter Berücksichtigung der ressourcenschonenden Bauweise konstruiert. Zudem werden bestehende Bauwerke im Rahmen von Strukturwandelungen umfunktioniert und mit veränderten Einwirkungen belastet. Dadurch steigt der Einfluss des Ermüdungsverhaltens der Werkstoffe in der Tragwerksbemessung bedeutend. Diese Arbeit bezieht Teile der vorhandenen Erkenntnisse über die Ermüdung und die elektrische Widerstandsmessung aufeinander und stellt die durchgeführten dynamischen Versuche und den statischen Versuch mit entsprechender Kennwert‐Auswertung und Analyse vor. Abschließend wird aufgeführt, dass die elektrische Widerstandsmessung ein vielversprechendes und zerstörungsfreies Prüfverfahren zur Zustandsbewertung im Bereich des Ermüdungsphänomens ist, die Messmethode allerdings bezüglich der fehlerfreien Anwendbarkeit infolge sekundärer Messeinflüsse noch optimiert werden muss. Im Weiteren werden die Berechnungen und Auswertungen der Ermüdungsversuche dazu genutzt, einige europäische Bemessungsnormen und verschiedene Testergebnisse für das Ermüdungsverhalten von Betonstahl näher zu untersuchen und zu vergleichen. Abstract en The measurement of the electrical resistance used for a non‐destructive method for reinforcing steel in concrete strained by fatigue‐relevant loading The fatigue behavior of reinforcing steel, prestressing steel and concrete has increasingly come into the focus of science in recent decades. In addition to the constantly increasing demands on, for example, bridge structures and wind turbines, which demand longer service lives and thus more load cycles, the designs of new constructions are designed increasingly filigree and slimmer. In addition, existing buildings are being converted in course of structural and social changes and are loaded with altered actions. As a result, the influence of the fatigue behavior of the materials on the structural analysis increases significantly. This work relates parts of the existing knowledge about fatigue and electrical resistance measurement to each other and presents the tests with the associated evaluation of physical values and analyses. Finally, it is stated that the electrical resistance measurement is a promising non‐destructive test method for assessing the state of fatigue phenomenon, but the measuring method still has to be optimized with regard to its faultless applicability due to secondary measurement influences. In addition, the calculations and evaluations of the fatigue tests are used to examine and compare European design standards and various test results for the fatigue behavior of reinforcing steel in more detail.
Article
A new probe, which does not use a confinement ring, has been developed to assess the corrosion state of reinforced concrete structures. Galvanostatic polarization is performed and the rebar corrosion potential, concrete resistivity and rebar corrosion rate are evaluated using an iterative calculation algorithm. The surface linear polarization resistance (RP,s = ΔEP/jPI) of the rebar/concrete interface is calculated by converting the potential measured at the surface into the rebar polarization ΔEP and the current density at the point of interest (PI) jPI using 3D numerical simulations. The calculation involves three geometrical parameters that modify the current and potential distribution in the concrete: the rebar spacing, s; the concrete cover, c; and the rebar diameter, D. Concrete cover resistivity is calculated using the instantaneous ohmic drop measured at the beginning of the galvanostatic polarization and the rebar corrosion rate is calculated using the steady-state potential. As the rebar corrosion rate also modifies the potential distribution in concrete, an iterative methodology was developed, using different supposed corrosion rates. Finally, the probe and associated methodology were used to evaluate the corrosion state of eight concrete slabs. Half of them were prepared with chloride in order to initiate corrosion. Four slabs were stored outdoors, two indoors in an ordinary laboratory environment and two indoors in a 50% CO2 gas chamber. The three corrosion parameters evaluated (corrosion potential, concrete cover resistivity and rebar corrosion rate) were in good agreement with the composition of the slabs and their curing conditions.
Conference Paper
This paper investigates the application of surface electrical resistivity measures to assess the durability of concrete pavements containing steel fibers. Electrical resistivity testing has become a popular method to predict the service life of concrete with a good correlation with the chloride penetration testing results. The application of surface resistivity follows the same trends for in-service materials. However, the steel reinforcement in concrete elements, including pavements introduces sources of errors in such measure. Existing literature offers techniques to minimize such errors in conventional reinforcements with the orderly spatial distribution of steel bars. The presented investigation utilized numerical simulations to identify challenges introduced by randomly distributed steel fibers in concrete pavements. Results address expected errors in surface electrical resistivity caused by short steel fibers in standard specimens and analyze these errors with respect to properties and characteristics of steel fibers and their spatial distributions within the body of the concrete. Conclusions include an assessment of errors and offer modification factors for realistic conditions.
Article
Industrialized sites pose challenges for conducting electrical resistivity geophysical surveys, as the sites typically contain metallic infrastructure that can mask electrolytic-based soil and groundwater contamination. The Hanford site in eastern Washington State, USA, is an industrialized site with underground storage tanks, piping networks, steel fencing, and other potentially interfering infrastructure that could inhibit the effectiveness of electrical resistivity tomography (ERT) to map historical and monitor current waste releases. The underground storage tanks are the largest contributor by volume to subsurface infrastructure and can be classified as reinforced concrete structures with an internal steel liner. Directly measuring the effective value for the electrical resistivity of the tank, i.e., the combination of individual components that comprise the tank’s shell, is not reasonably possible because they are buried and dangerously radioactive. Therefore, we indirectly assess the general resistivity of the tanks and surrounding infrastructure by developing synthetic ERT models with a parametric forward modeling study using a wide range of resistivity values from 1×10 ⁻⁶ to 1×10 ⁴ ohm-m, which are equivalent to steel and dry rock, respectively. The synthetic models used the long-electrode ERT method (LE-ERT), whereby steel cased metallic wells surrounding the tanks are used as electrodes. The patterns and values of the synthetic tomographic models were then compared to LE-ERT field data from the AX tank farm at the Hanford site. This indirect method of assessing the effective resistivity revealed that the reinforced concrete tanks are electrically resistive and the accompanying piping infrastructure has little influence on the overall resistivity distribution when using electrically based geophysical methods for characterizing or monitoring waste releases. Our findings are consistent with nondestructive testing literature that also shows reinforced concrete to be generally resistive.
Article
The electrical resistivity is used in this study to assess the moisture content of the concrete, because of their good correlation. A new process using four point probes to measure the electrical resistivity of concrete is described in this paper. It is based on the exploitation of the short circuit induced by the reinforcement in the concrete structure. A numerical model is also made to simulate the resistivity measurements on concrete by also taking into account the electrochemical parameters of the reinforcement. The obtained results have shown the ability of the new measurement process to assess the gradient of the moisture content of the concrete cover.
Article
Full surface surveys which are likely to include e.g. a deterioration and potential mapping as well as a cover depth survey, should be the base to identify critical areas which are suspect to be suffering from reinforcement corrosion [1]. Localised assessment in these areas should give further information about the type and extent of deterioration. It should include the determination of the chloride profile beyond the cover depth, the depth of carbonation and a direct visual assessment of the steel reinforcement by breaking away the cover concrete at selected locations. Further valuable information may be collected by determining the water content of the concrete or performing corrosion rate measurements. Within this publication the essential methods for local detailed inspections are discussed regarding the application and interpretation of the results. An overview of the survey procedure is given in ref. [2].
Article
Dipole--dipole induced-polarization measurements are commonly presented as pseudosections, but results using different dipole lengths cannot be combined into a single pseudosection. By considering the theoretical results for simple earth models, a unique set of relative depth coefficients is empirically derived, such that measurements with different array parameters will ''mesh'' smoothly into a combined pseudosection. Application of these coefficients to a number of theoretical and field cases shows that they give reasonable results when applied to more complicated models. The empirical coefficients are compared with Roy's theory of ''depth of investigation characteristic,'' and support that theory, if a modified definition of ''effective depth'' is accepted. This leads to an absolute depth scale for the modified pseudosection. It is shown that rough estimates of the depth to the top of an anomalous body can be made directly on the pseudosection, at true vertical scale. This definition of effective depth is applied to other electrode arrays. It is shown, by examples, that the resulting pseudosections give consistent estimates of depth to top, within the characteristic anomaly patterns of each array. The effective depths for various arrays are compared; the results agree with the traditional applications of each array.
Article
Half-cell potential mapping techniques have been used successfully to indicate regions where steel reinforcement is corroding unseen beneath the surface of concrete structures. It has been proposed that a mapping of the electrical resistivity of the concrete can be used in conjunction with the potential method to assess the severity of the corrosion problem in addition to the location of corroding regions. In this Paper, some of the advantages and drawbacks are discussed, with different methods of making measurements in situ. Practical tests and theoretical studies were conducted to assess the accuracy and reliability of different methods of measurement. The influence of both the ambient environmental conditions and the specimen configuration on the resistivity measurement were also investigated. Practical guidance is given to engineers in resistivity measurement techniques and in the interpretation of results.
Book
The book is divided into two parts. Part 1 gives an introduction to and an overview of the field in ten tutorial chapters. Part 2 contains a selection of invited and proffered papers reporting on current research. Subjects covered in depth are: analytical image reconstruction, regularization, iterative methods, image structure, 3-D display, compression, architectures for image processing, statistical pattern recognition, and expert systems in medical imaging.
Article
The electrostatic analogue to direct current resistivity prospecting is employed to construct vertical sections through lines of four electrodes. These show the relative contributions made by individual volume elements of earth to the total potential difference measured between the two potential electrodes. Signal contribution sections enable a comparison of the response of various electrode configurations to subsurface conditions and help to explain, for example, why the dipole—dipole configuration is so suited to horizontal profiling and the Wenner and Schlumberger configurations to vertical sounding. The spurious response of apparent resistivity curves to near surface lateral resistivity variations is also explained with particular attention being given to the Wenner tripotential configurations.
Article
Geophysical inversion involves the estimation of the parameters of a postulated earth model from a set of observations. Since the associated model responses can be nonlinear functions of the model parameters, nonlinear least-squares techniques prove to be useful for performing the inversion. A common type of inversion applies iterative damped linear least squares through use of the Marquardt-Levenberg method. Traditionally, this method has been implemented by solving the associated normal equations in conventional ways. However, Singular Value Decomposition (SVD) produces significant improvements in computational precision when applied to the same system of normal equations. Iterative least-squares modeling finds application in a wide variety of geophysical problems. Two examples illustrate the approach: (1) seismic wavelet deconvolution, and (2) the location of a buried wedge from surface gravity data. More generally, nonlinear least-squares inversion can be used to estimate earth models for any set of geophysical observations for which an appropriate mathematical description is available.
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