scholarly journals Corrosion potential: influence of moisture, water-cement ratio, chloride content and concrete cover

2017 ◽  
Vol 10 (4) ◽  
pp. 864-885 ◽  
Author(s):  
M. H. F. Medeiros ◽  
F. C. Rocha ◽  
R. A. Medeiros-JUNIOR ◽  
P. Helene
Keyword(s):  
Corrosion Potential ◽  
Statistical Significance ◽  
Chloride Content ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Degree Of Contamination ◽  
Destructive Testing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Cover Thickness

ABSTRACT The method of measuring the corrosion potential is used as an electrochemical tool for helping the monitoring of the corrosion of reinforcements of concrete structures. As a criterion for evaluating results it is common to use intervals of corrosion potential and their correlation with corrosion probability, as precognizes ASTM C 876:2015. With this criterion, it is possible to establish an overview of the thermodynamic situation of corrosion in the structure or in the test specimen in laboratory. However, the method is influenced by several factors related with the concrete, the environment and with procedures adopted at the moment of executing the readings. Aiming to provide information to guide the technical and scientific environment regarding the right use of this type of non-destructive testing, the objective of this work is to evaluate some possible factors influencing the reading of corrosion potential, such as: moisture content of the concrete, water/cement ratio, thickness of the concrete cover and degree of contamination by chlorides. Results indicate that moisture and degree of contamination of the concrete by chloride ions had a tendency of making the corrosion potential more electronegative. Besides, it was verified that the influence of the cover is different for the case of contaminated concrete (1% of chlorides by mass of cement) and not contaminated with chlorides: the influence of the thickness of the cover, in the case of concrete contaminated by chlorides, was inversely proportional, in other words, the greater the cover thickness is, the less electronegative the value of the corrosion potential will be. On the other hand, in cases of concretes without chlorides, the effect of the cover thickness in the readings or corrosion potential was irrelevant. All this information was proved with 95% of statistical significance.

Study on the Concrete in Chloride Environment Based on Electrochemical Impedance Spectroscopy

2019 ◽  
Vol 34 (06) ◽  
pp. 2059017
Author(s):  
Fengjiao Jiang ◽  
Jinxin Gong ◽  
Jichao Zhu ◽  
Huan Wang
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Electric Double Layer ◽  
Electrochemical Impedance ◽  
Pore Solution ◽  
Salt Water ◽  
Chloride Ions ◽  
Double Layer Capacitance ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Electric Double Layer Capacitance

In this paper, the effect of water-cement ratio and chloride ions on the concrete meso-structure was studied. Three kinds of concrete cubes with different water-cement ratios were immersed in fresh water and salt water, respectively. Then, the Electrochemical Impedance Spectroscopy (EIS) analysis of various test cubes were carried out by using electrochemical workstation. The results show that the salt water can improve electric double layer capacitance in the test cubes with the same water-cement ratio, but it can reduce some other parameters such as resistance of pore solution, resistance to transfer the hydrated electron, coefficient of diffusion impedance of concreter, which shows that the chloride ions diffused into the concrete in salt water and increase the ionic concentration in pore solution and C-S-H gel. However, the phase angle index is constant whether in fresh water or salt water, which shows chloride ions cannot affect the concrete meso-structure even though they can improve the ion concentration of pore structure. For the concrete test cubes which has different water-cement ratio in salt water, with the reduction of water-cement ratio, the electric double-layer capacitance of concrete remains unchanged, which indicates when the water-cement ratio becomes smaller, the porosity becomes lower, and the internal structure of concrete becomes denser.

Parameters of Acoustic Emission Signals Obtained During the Setting and Hardening of Concrete Mixtures with Different Water-Cement Ratio

2016 ◽  
Vol 837 ◽  
pp. 152-156 ◽  
Author(s):  
Libor Topolář ◽  
Kristýna Timcakova ◽  
Petr Misak ◽  
Luboš Pazdera
Keyword(s):  
Acoustic Emission ◽  
Concrete Structure ◽  
Building Materials ◽  
Building Structures ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Destructive Testing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Hardening

Concrete hardening and setting processes are the most critical phases during construction work, influencing the properties of concrete structure. For this reason applying non-destructive testing in the early age of concrete lifetime can be useful. Acoustic emission method is a powerful tool for determination of lifetime concrete structures. Nevertheless, its application in civil engineering area is not easy because many building structures are inhomogeneous. This method can describe material changes during concrete lifetime. Acoustic Emission Method monitors concrete structure continuously. Changes in the whole concrete structure are recorded. The acoustic emission phenomenon is directly associated with nucleation of cracks in building materials, therefore the changes result from the volumetric expansion causing formation micro and macro cracking in structure, which we can recognize. Application of Acoustic Emission Method during concrete hardening and setting with different water-cement ratio will be the aim of this article and his influence on parameters of acoustic emission. A comprehension of microstructure-performance relationships is the key to true understanding of material behaviour.

An Experimental Assessment of the Effects of Concrete Mix Proportions on Penetration of Chloride Ions

2011 ◽  
Vol 261-263 ◽  
pp. 352-355
Author(s):  
Jian Jiang Ding ◽  
Jian Jun Zheng ◽  
Chun Lei Chen
Keyword(s):  
Fly Ash ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Wetting And Drying ◽  
Aggregate Gradation ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Mix ◽  
Durability Assessment ◽  
Theoretical Evidence

The study on the penetration of chloride ions into concrete is very important for the durability assessment and design of reinforced concrete structures. A cyclic wetting and drying test is conducted to evaluate the effects of concrete mix proportions on the penetration of chloride ions. Based on the experimental results, the variations in chloride ion content at various points in concrete with the water/cement ratio, maximum aggregate diameter, aggregate gradation, fly ash content, and anticorrosion agent content are analyzed quantitatively. It is found that the water/cement ratio, aggregate gradation, maximum aggregate diameter, and fly ash all have a larger influence on the penetration of chloride ions. These conclusions can provide theoretical evidence for the design optimization of concrete properties.

scholarly journals Quantitative Non-Linear Effect of High Ambient Temperature on Chloride Threshold Value for Steel Reinforcement Corrosion in Concrete under Extreme Boundary Conditions

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7595
Author(s):  
Abdulrahman M. Alhozaimy ◽  
Mshtaq Ahmed ◽  
Raja Rizwan Hussain ◽  
Abdulaziz Al-Negheimish
Keyword(s):  
Corrosion Rate ◽  
Corrosion Potential ◽  
Electrochemical Techniques ◽  
Chloride Content ◽  
Threshold Value ◽  
Chloride Ions ◽  
Water Soluble ◽  
Linear Effect ◽  
Chloride Threshold ◽  
Exposure Temperature

This paper investigates the effect of high ambient temperatures on the chloride threshold value for reinforced concrete (RC) structures. Two commonly available carbon steel rebars were investigated under four different exposure temperatures (20 °C (68 °F), 35 °C (95 °F), 50 °C (122 °F), and 65 °C (149 °C)) using environmental chambers at a constant relative humidity of 80%. For each temperature, six different levels of added chloride ions (0.00%, 0.15%, 0.30%, 0.60%, 0.90%, and 1.20% by weight of cement) were used to study the chloride threshold value. Corrosion initiation was detected by monitoring the corrosion potential and corrosion rate using electrochemical techniques. The water-soluble (free) and acid-soluble (total) chlorides were determined using potentiometric titration according to the relevant ASTM standards. The threshold chloride content for each exposure temperature was determined by analyzing the corrosion potential, corrosion rate, and chloride content of each specimen. The results showed that the chloride threshold values were significantly temperature-dependent. At temperatures of 20 °C (68 °F) and 35 °C (95 °F), the chloride threshold value (expressed as free chlorides) was approximately 0.95% by weight of cement. However, as the temperature increased to 50 °C (122 °F), the chloride threshold decreased significantly to approximately 0.70% by weight of cement. The reduction in the chloride threshold value became more dramatic at an exposure temperature of 65 °C (149 °F), decreasing to approximately 0.25% by weight of cement. The trends were similar for the rebars from the two sources, indicating that the rebar source had little influence on the chloride threshold value.

scholarly journals Chloride accelerated test: influence of silica fume, water/binder ratio and concrete cover thickness

2013 ◽  
Vol 6 (4) ◽  
pp. 561-581 ◽  
Author(s):  
E. Pereira ◽  
A. Resende ◽  
M. H. F. de Medeiros ◽  
L. C. Meneghetti
Keyword(s):  
Silica Fume ◽  
Chloride Content ◽  
High Water ◽  
Developed Countries ◽  
Concrete Cover ◽  
Accelerated Corrosion ◽  
Binder Ratio ◽  
The Uk ◽  
Cover Thickness ◽  
Water Binder Ratio

In developed countries like the UK, France, Italy and Germany, it is estimated that spending on maintenance and repair is practically the same as investment in new constructions. Therefore, this paper aims to study different ways of interfering in the corrosion kinetic using an accelerated corrosion test - CAIM, that simulates the chloride attack. The three variables are: concrete cover thickness, use of silica fume and the water/binder ratio. It was found, by analysis of variance of the weight loss of the steel bars and chloride content in the concrete cover thickness, there is significant influence of the three variables. Also, the results indicate that the addition of silica fume is the path to improve the corrosion protection of low water/binder ratio concretes (like 0.4) and elevation of the concrete cover thickness is the most effective solution to increase protection of high water/binder ratio concrete (above 0.5).

Evaluation of the corrosion potential in armed concrete as a function of armature covering

2021 ◽  
Author(s):  
Lázaro Rodrigues Penna ◽  
Maria Luísa Freitas dos Santos Honório ◽  
João Victor Laurindo Siqueira ◽  
Diogo Pereira dos Santos Kropf
Keyword(s):  
Corrosion Potential ◽  
Concrete Structures ◽  
Concrete Cover ◽  
Potential Range ◽  
Hardened Concrete ◽  
Corrosion Monitoring ◽  
Potential Measurement ◽  
External Agents ◽  
Cover Thickness ◽  
Corrosion Of Steel

In concrete structures, it is not uncommon to observe the presence of pathological problems that can often be associated with high temperature range, inadequate execution of works, inefficient projects, materials without quality control, unprepared labor, harmful external agents, among others. Among the pathological manifestations of hardened concrete is the corrosion of steel reinforcement, directly influencing the durability and strength of concrete structures. The object of this research is to analyze the influence of concrete cover thickness and chloride contamination on the potential readings of reinforcement corrosion. Since the cover thickness has a direct influence on the potential readings in chloride contaminated concrete. The corrosion potential measurement method will be used as an electrochemical tool to assist in the corrosion monitoring of reinforced concrete structures. As a standard for the evaluation results, the corrosion potential range recommended by ASTM C 876: 2015 and its relationship with the possibility of corrosion is normally used. With the results obtained during the application of this method, it is possible to identify regions where the reinforcement presents corrosion and how the process of steel depassivation is distributed in the region under study. Therefore, it is expected to verify the influence that the concrete cover has on chloride contamination and also influence the values of the corrosion potential.

Experimental Study and Numerical Analysis on Chloride Diffusion Coefficient of Concrete with Various Water-Cement Ratios

2017 ◽  
Vol 726 ◽  
pp. 547-552
Author(s):  
Zheng Ren ◽  
Lian Zhen Xiao ◽  
Wen Chong Shi
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Chloride Ion Diffusion

A rapid chloride ion diffusion coefficient measurement (RCM) was used in this study. The influence of water-cement ratios of 0.30, 0.35 and 0.40 at various ages (3, 7, 14, 28 and 56 days) on chloride ion diffusion coefficient of the concretes and pastes was studied and analyzed. The results show that, with the increase of curing ages, the chloride ion diffusion coefficient of different water-cement ratio of each specimen is decreased. In the early age, the chloride ion diffusion coefficient of the paste with the water-cement ratio of 0.40 is 2~3 times of the paste with water-cement ratio of 0.30 and 0.35, and with the increase of curing age, this difference is gradually decreased. Additionally, the chloride ion diffusion coefficient of the cement paste is 1~2 times of the concrete with same water-cement ratio at different ages. Based on the actual experiment boundary conditions, the process of chloride ions diffusion and permeability was simulated by COMSOL software, and the simulation result was analyzed to predict the permeability of concrete.

The Impact of Concrete Cover Thickness and Chemical Alkalinity on Reinforcement Corrosion

2014 ◽  
Vol 1065-1069 ◽  
pp. 1957-1963
Author(s):  
Xiu Jing Zhou ◽  
Jia Ming Shu ◽  
Ji Dong Zhang ◽  
Yong Xian Yan ◽  
Wei Zhong Gan
Keyword(s):  
Corrosion Potential ◽  
Concrete Cover ◽  
Experimental Measurements ◽  
Reinforcement Corrosion ◽  
Atmospheric Conditions ◽  
Alkali Aggregate Reaction ◽  
Structural Durability ◽  
Cover Thickness ◽  
Standard Limit ◽  
The Impact

Based on the mechanism of reinforcement corrosion in concrete structures and the experimental measurements of corrosion potential and resistance, this paper investigates the impact of concrete cover thickness and chemical alkalinity on reinforcement corrosion. Experimental results show that the rate of reinforcement corrosion decreases as the thickness of concrete cover of reinforcement increases. Moreover, given no risk of alkali-aggregate reaction, raising the chemical alkalinity of concrete cover helps maintain passivation of reinforcement. Additionally, under general atmospheric conditions, cracks that are not along bars barely affect structural durability if the width of cracks is smaller than its standard limit.

scholarly journals ESTIMATION POSITION AND DIAMETER OF REBAR BY MODERN NON-DESTRUCTIVE TECHNIQUES

AГГ+ ◽  
2019 ◽  
Vol 1 (7) ◽  
Author(s):  
Dragan Nikolić ◽  
Dragan Bojović ◽  
Lana Antić Aranđelović ◽  
Goran Ćirović
Keyword(s):  
Concrete Cover ◽  
Ultrasonic Tomography ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Concrete Members ◽  
Cover Thickness ◽  
Entrained Air ◽  
Non Destructive ◽  
Non Destructive Techniques

Ultrasonic testing of concrete by modern equipment has grown in importance in recent years in non-destructive testing. Measuring concrete cover thickness and estimating steel rebar position and diameter is main focus for assessment of existing reinforcement concrete facilities. Voids, entrained air and potential delamination are important to detect in order to evaluate the quality of the executed concrete members. This paper presents the latest two modern non-destructive techniques – ultrasonic tomography and electromagnetic pulse induction – suitable for testing reinforcement concrete members. The capabilities of these techniques for locating defects, reinforcement bars and determining their size in unilaterally accessible concrete members are described.

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