Monitoring the Electrochemical Response of Chloride Sensors Embedded in Cement Paste

2015 ◽  
Vol 1768 ◽  
Author(s):  
F. Pargar ◽  
D.A. Koleva ◽  
E.A.B. Koenders ◽  
K. van Breugel
Keyword(s):  
Cement Paste ◽  
Electrochemical Impedance ◽  
Chloride Concentration ◽  
External Solution ◽  
Chloride Content ◽  
Open Circuit ◽  
Water Soluble ◽  
Free Chloride ◽  
Chloride Determination ◽  
Bound Chloride

ABSTRACTThis work presents the electrochemical behavior of Ag/AgCl electrodes (chloride sensors) in cement paste environment, monitored over a period of 180 days via open circuit potential (OCP) readings and electrochemical impedance spectroscopy (EIS). The EIS response indicates modification of the sensors’ morphology, in particular alteration of the AgCl layers, as a result of continuous chloride penetration into the bulk matrix towards the vicinity of the sensor/cement paste interface. A gradual shift to more cathodic OCP values and stabilization at approximately -1mVSCE to 2mVSCE was observed at the end of the test, reflecting chloride content of 820mM to 930mM in the pore solution surrounding the sensors, which differs 5-10% from the chloride concentration in the external solution. The water soluble chloride content in the cement pate, as destructively measured wet chemically by Volhard method and photometry, was in the range of 1100mM - 1300mM i.e. about 30-50% more than the chloride concentration in the external solution. This difference of maximum 50% in the recorded chloride levels is attributed to the fact that the sensors “read” the average amount of free chloride at the interface sensor/cement paste, while the destructively measured water soluble chloride reflects the average free (with possible contribution of physically bound chloride) in the total volume of analyzed cement paste. It can be concluded that for the conditions of this experiment, more reliable free chloride content is measured via the sensors’ readings. Hence, if chloride thresholds for corrosion initiation are to be determined, the sensors’ readings will be more representative and accurate if compared to destructive water soluble chloride determination.

scholarly journals Potentiometric Response of Ag/AgCl Chloride Sensors in Model Alkaline Medium

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Farhad Pargar ◽  
Hristo Kolev ◽  
Dessi A. Koleva ◽  
Klaas van Breugel
Keyword(s):  
Alkaline Medium ◽  
Open Circuit Potential ◽  
Dynamic Equilibrium ◽  
Chloride Concentration ◽  
Chloride Content ◽  
Cementitious Materials ◽  
Open Circuit ◽  
Potentiometric Response ◽  
Before And After ◽  
The Stability

The stability and reproducibility of an Ag/AgCl sensors’ response in an alkaline medium are important for the application of these sensors in cementitious materials. The sensors’ response, or their open circuit potential (OCP), reflects a dynamic equilibrium at the sensor/environment interface. The OCP response in an alkaline medium is affected by the presence of hydroxide ions. The interference of hydroxide ions leads to inaccuracies or a delay in the sensors’ response to a certain chloride content. In this article, the potentiometric response (or OCP evolution) of the chloride sensors is measured in model solutions, resembling the concrete pore water. The scatter of the sensors’ OCP is discussed with respect to the interference of hydroxide ions at varying chloride concentration in the medium. The deviation of the sensor’s response from its ideal performance (determined by the Nernst law) is attributed to dechlorination of the AgCl layer and the formation of Ag2O on the sensor’s surface. Results from the surface XPS analysis of the AgCl layer before and after treatment in alkaline medium confirm these observations in view of chemical transformation of AgCl to Ag2O.

Chloride Distribution Feature in Surface Layer of Cement Paste under Cyclic Drying-Wetting Condition

2016 ◽  
Vol 711 ◽  
pp. 367-374 ◽  
Author(s):  
Hong Lei Chang ◽  
Song Mu ◽  
Jian Zhong Liu
Keyword(s):  
Surface Layer ◽  
Cement Paste ◽  
Total Porosity ◽  
Chloride Content ◽  
Homogeneous Surface ◽  
Maximum Value ◽  
Free Chloride ◽  
Wet Condition ◽  
Chloride Profiles ◽  
Wetting Time

This research focuses on chloride distribution in the surface layer of cement paste and the relation between chloride distribution and pore structure under two different drying-wetting regimes. The results of chloride profiles obtained by three different methods reveal that it dose exist a feature that chloride content first gose up then down with a maximum value Cmaxappearing in the homogeneous surface layer of cement paste subjected to indoor cyclic dry-wet condition. Besides, the Cmaxincreases with the ratio of water to cement (W/C) increasing. And the regime with higher drying temperature and longer wetting time leads to higher Cmax. Moreover, Cmaxappears at the same location for both total and free chloride. In addition, Cmaxincreases with total porosity, the most probable pore size, and average radius increasing, while it decreases with tortuosity decreasing.

Influence of Crack Depth on Chloride Transport of Cracked Self-Compacting Concrete under Non-Steady State Migration Test

2011 ◽  
Vol 328-330 ◽  
pp. 1331-1334
Author(s):  
Song Mu ◽  
Geert de Schutter ◽  
Bao Guo Ma
Keyword(s):  
Chloride Transport ◽  
Crack Depth ◽  
Chloride Concentration ◽  
Chloride Content ◽  
Point Of View ◽  
Water Soluble ◽  
Test Method ◽  
Migration Test ◽  
Self Compacting Concrete ◽  
Chloride Migration

From a physical and mechanical point of view, concrete cracking is hard to avoid. So, it is meaningful to study the influence of crack depths on chloride transport in cracked self-compacting concrete. Following the NT BUILD 492 chloride migration test method, water soluble chloride conetnt, acid soluble chloride content and penetration depth were determined on cracked concrete samples which were prepared by artificial crack method. Afterwards, the migration coefficients were obtained by curve fitting on water soluble chloride contents and penetration depths seperately. The results show that the influence of crack depth on chloride concentration of concrete is significant for the concrete zone deeper than 20 mm from the surface. Secondly, the influential zone caused by the crack is limited to a distance of 10 mm at both sides from the crack. Thirdly, the existing equation of chloride transport is not applicable to concrete with different crack depths.

scholarly journals Chloride Levels That Initiated Corrosion of Duplex Stainless Steel Embedded in Mortar

2019 ◽  
Vol 2019 ◽  
pp. 1-6 ◽  
Author(s):  
Yu-You Wu ◽  
Francisco Presuel-Moreno
Keyword(s):  
Stainless Steel ◽  
Reinforced Concrete ◽  
Electrochemical Impedance ◽  
Concrete Structures ◽  
Chloride Concentration ◽  
Threshold Value ◽  
Open Circuit ◽  
Reinforced Concrete Structures ◽  
Premature Failure ◽  
Chloride Threshold

Chloride-induced corrosion of carbon steel has been widely recognized as one of the main causes of premature failure on the reinforced concrete structures. Various strategies and measures such as employing stainless steel reinforcements have been developed to address this problem. Past studies have been concerned with the identification and characterization of chloride threshold since corrosion would not initiate as long as the chloride concentration values at the reinforcing stainless steel depth remains below this threshold value. It is therefore a critical parameter for the design of new stainless steel reinforced concrete structures and the assessment of existing concrete structures. This study presents the finding on the chloride threshold of stainless steel UNS32304 embedded in mortar with two different mixes. Reinforced mortar specimens were subjected to ponding exposure and wet/dry cycle exposure with a sodium chloride solution. The specimens were monitored by using the measurements of the open circuit potential, electrochemical impedance spectroscopy, and linear polarization resistance. The paper also discusses the chloride threshold values of such stainless steel embedded in mortar and concrete with other mixes reported by other researchers and the factors that may affect these values.

scholarly journals Electrochemical Investigations of Steels in Seawater Sea Sand Concrete Environments

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5713
Author(s):  
Xiang Yu ◽  
Saad Al-Saadi ◽  
Xiao-Ling Zhao ◽  
R. K. Singh Raman
Keyword(s):  
Corrosion Resistance ◽  
Stainless Steels ◽  
Detrimental Effect ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Electrochemical Corrosion ◽  
Chloride Content ◽  
Open Circuit ◽  
Portland Cement Concrete ◽  
Sea Sand

Seawater and sea sand concrete (SWSSC) is an environmentally friendly alternative to ordinary Portland cement concrete for civil construction. However, the detrimental effect of high chloride content of SWSSC on the corrosion resistance of steel reinforcement is a concern. This study undertook the electrochemical corrosion behaviour and surface characterizations of a mild steel and two stainless steels (AISI type 304 and 316) in various simulated concrete environments, including the alkaline + chloride environment (i.e., SWSSC). Open circuit potential (OCP), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) were employed. Though chloride is detrimental to the corrosion resistance of mild steels, a simultaneous presence of high alkalinity in SWSSC negate the detrimental effect of chloride. In the case of stainless steels, a high level of alkalinity is found to be detrimental, whereas chloride seems to have less detrimental effect on their corrosion resistance.

A New Smart Additive of Reinforced Concrete Based on Modified Hydrotalcites: Preparation, Characterization and Anticorrosion Applications

2012 ◽  
Vol 1488 ◽  
Author(s):  
Zhengxian Yang ◽  
Hartmut Fischer ◽  
Rob Polder
Keyword(s):  
Carbon Steel ◽  
Open Circuit Potential ◽  
Pore Solution ◽  
Chloride Concentration ◽  
Open Circuit ◽  
Inhibiting Effect ◽  
Corrosion Initiation ◽  
Free Chloride ◽  
Chloride Exchange ◽  
Ft Ir

ABSTRACTA carbonate form of Mg-Al-hydrotalcite and its p-aminobenzoate (pAB) modified derivative (i.e.,Mg(2)Al-pAB) were synthesized and characterized by means of XRD and FT-IR. The anticorrosion behavior was evaluated based on open circuit potential (OCP) of carbon steel in simulated concrete pore solution and chloride-exchange experiments. The preliminary results shown in this study demonstrated that ion-exchange indeed occurred between chlorides and the intercalated pAB anions in Mg(2)Al-pAB structure, thereby reducing the free chloride concentration in simulated concrete pore solution. The simultaneously released inhibitive pAB anions were found to exhibit the envisaged inhibiting effect and caused corrosion initiation of the steel shifting to a higher chloride concentration than without the modified hydrotalcites.

scholarly journals A gateway for ion transport on gas bubbles pinned onto solids

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Veton Haziri ◽  
Tu Pham Tran Nha ◽  
Avni Berisha ◽  
Jean-François Boily
Keyword(s):  
Ion Transport ◽  
Metal Ion ◽  
Electrochemical Impedance ◽  
Gas Bubbles ◽  
Open Circuit ◽  
Double Layers ◽  
Water Geochemistry ◽  
Chemical Potentials ◽  
Pore Water Geochemistry ◽  
Electric Potentials

AbstractGas bubbles grown on solids are more than simple vehicles for gas transport. They are charged particles with surfaces populated with exchangeable ions. We here unveil a gateway for alkali metal ion transport between oxygen bubbles and semi-conducting (iron oxide) and conducting (gold) surfaces. This gateway was identified by electrochemical impedance spectroscopy using an ultramicroelectrode in direct contact with bubbles pinned onto these solid surfaces. We show that this gateway is naturally present at open circuit potentials, and that negative electric potentials applied through the solid enhance ion transport. In contrast, positive potentials or contact with an insulator (polytetrafluoroethylene) attenuates transport. We propose that this gateway is generated by overlapping electric double layers of bubbles and surfaces of contrasting (electro)chemical potentials. Knowledge of this ion transfer phenomenon is essential for understanding electric shielding and reaction overpotential caused by bubbles on catalysts. This has especially important ramifications for predicting processes including mineral flotation, microfluidics, pore water geochemistry, and fuel cell technology.

scholarly journals Concrete Examination of 100-Year-Old Bridge Structure above the Kłodnica River Flowing through the Agglomeration of Upper Silesia in Gliwice: A Case Study

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 981
Author(s):  
Barbara Słomka-Słupik ◽  
Jacek Podwórny ◽  
Beata Grynkiewicz-Bylina ◽  
Marek Salamak ◽  
Bibianna Bartoszek ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
High Performance ◽  
Chloride Content ◽  
Technical Condition ◽  
Inductively Coupled ◽  
Bridge Safety ◽  
Free Chloride ◽  
Management Processes ◽  
Icp Ms ◽  
Plasma Mass Spectrometry

The article analyzes the composition of concrete taken from various elements from a 100-year-old bridge in South Poland, so as to analyze its technical condition. The main methods applied during experimental work were: Designation of pH, free chloride content, salinity, XRD and SEM examinations, as well as metals determination using inductively coupled plasma mass spectrometry (ICP­MS), high-performance liquid chromatography (HPLC)-ICP-MS, and cold-vapor atomic absorption spectroscopy (CV-AAS). The concrete of the bridge was strongly carbonated and decalcified with an extremely high content of chlorides. The pH of the concrete was in a range from 10.5 to 12.0. Acid soluble components were between 9.9% and 17.6%. Typical sulfate corrosion phases of concrete were not detected. Friedels’ salt was found only at the extremity of an arch. The crown block was corroded to the greatest extent. Various heavy metals were absorbed into the concrete, likely from previous centuries, when environmental protection policy was poor. The applied research methodology can be used on bridges exposed to specific external influences. The acquired knowledge can be useful in the management processes of the bridge infrastructure. It can help in making decisions about decommissioning or extending the life cycle of the bridge. This work should also sensitize researchers and decision-makers to the context of “bridge safety”.

scholarly journals Sacrificial Dissolution of Zinc Electroplated and Cold Galvanized Coated Steel in Saline and Soil Environments: A Comparison

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 744
Author(s):  
Ameeq Farooq ◽  
Umer Masood Chaudry ◽  
Ahsan Saleem ◽  
Kashif Mairaj Deen ◽  
Kotiba Hamad ◽  
...  
Keyword(s):  
Corrosion Rate ◽  
Electrochemical Impedance ◽  
Saline Soil ◽  
Steel Substrate ◽  
Salt Spray ◽  
Steel Structures ◽  
Open Circuit ◽  
Cyclic Polarization ◽  
Transfer Resistance ◽  
Soil Solutions

To protect steel structures, zinc coatings are mostly used as a sacrificial barrier. This research aims to estimate the dissolution tendency of the electroplated and zinc-rich cold galvanized (ZRCG) coatings of a controlled thickness (35 ± 1 μm) applied via brush and dip coating methods on the mild steel. To assess the corrosion behavior of these coated samples in 3.5% NaCl and 10% NaCl containing soil solutions, open circuit potential (OCP), cyclic polarization (CP), and electrochemical impedance spectroscopy (EIS) tests were performed. The more negative OCP and appreciably large corrosion rate of the electroplated and ZRCG coated samples in 3.5% NaCl solution highlighted the preferential dissolution of Zn coatings. However, in saline soil solution, the relatively positive OCP (>−850 mV vs. Cu/CuSO4) and lower corrosion rate of the electroplated and ZRCG coatings compared to the uncoated steel sample indicated their incapacity to protect the steel substrate. The CP scans of the zinc electroplated samples showed a positive hysteresis loop after 24 h of exposure in 3.5% NaCl and saline soil solutions attributing to the localized dissolution of the coating. Similarly, the appreciable decrease in the charge transfer resistance of the electroplated samples after 24 h of exposure corresponded to their accelerated dissolution. Compared to the localized dissolution of the electroplated and brush-coated samples, the dip-coated ZRCG samples exhibited uniform dissolution during the extended exposure (500 h) salt spray test.

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