Reinforced Concrete Structure Performance in Marine Structures: Analyzing Durability Indexes to Obtain More Accurate Corrosion Initiation Time Predictions

This paper presents a comparison of six index properties collected during durability inspections of five Mexican seaports. Typical durability indicators such as compressive strength, saturated electrical resistivity, ultrasonic pulse velocity, percent total void content, capillary porosity, and chloride concentration profiles were analyzed to obtain empirical correlations with the non-steady-state chloride diffusion coefficient. These indices were compared to determine correlation coefficients that are the most important for obtaining better corrosion initiation forecasting. Two models of corrosion initiation time (ti) were used: Fick’s second law of diffusion and the reported UNE-83994-2 (Spanish Association for Standardization, UNE) in which electrical resistivity was used to calculate concrete service life. The data from both models were cleaned using correlated variables, and the initial variables were compared with ti. The main result achieved was the verification of the feasibility of using correlations of variables to clean unnecessary data in order to calculate ti. Additionally, electrical resistivity was identified as one of the main durability indexes for in-service concrete structures exposed to marine environments. This is important because electrical resistivity is a non-destructive and reliable test that can be measured both in the laboratory and in the field very easily.

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Probability Model of Corrosion Initiation Time of Steel in Concrete Structure in Chloride Environment

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.243-249.5632 ◽

2011 ◽

Vol 243-249 ◽

pp. 5632-5636

Author(s):

Ya Li Ma ◽

Ai Lin Zhang

Keyword(s):

Sensitivity Analysis ◽

Probability Distribution ◽

Probability Model ◽

Chloride Concentration ◽

Initiation Time ◽

Distribution Law ◽

Corrosion Initiation ◽

Corrosion Initiation Time ◽

Chloride Environment ◽

Distribution Type

Probability distribution law of corrosion initiation time of steel in concrete under chloride environment is discussed. Based on the Fick’s second law, by Monte Carlo, frequency distribution, distribution type and probability density is analyzed. The statistic parameters of the factors influencing the probability distribution of corrosion initiation time are studied and the expression for sensitivity analysis of corrosion initiation time is deduced. By sensitivity analysis can know, corrosion initiation time is found to be more sensitive to cover than the diffusion coefficient, and more sensitive to surface chloride concentration than the critical chloride level. The analysis of the paper perfects the methods of predicting the corrosion initiation time.

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CORROSION INITIATION TIME FOR REINFORCED CONCRETE MEMBERS ALONG INDIAN COASTS: EFFECTS OF TEMPERATURE AND RELATIVE HUMIDITY — A PROBABILISTIC APPROACH

International Journal of Reliability Quality and Safety Engineering ◽

10.1142/s0218539308003210 ◽

2008 ◽

Vol 15 (06) ◽

pp. 539-553

Author(s):

SATISH B. ALLAMPALLEWAR ◽

A. SRIVIDYA

Keyword(s):

Diffusion Coefficient ◽

Relative Humidity ◽

Probabilistic Approach ◽

Chloride Concentration ◽

Threshold Value ◽

Chloride Ingress ◽

Initiation Time ◽

Corrosion Initiation ◽

Concrete Members ◽

Corrosion Initiation Time

Corrosion initiation time of steel reinforcement for partially saturated concrete members subjected to chloride ingress is investigated at five places along Indian coasts using simplified probabilistic analysis and sensitivity of the parameters to reinforcement corrosion is studied. Previously proposed diffusion based chloride ingress model for constant surface chloride concentration and variable diffusion coefficient is used. Corrosion is initiated when the chloride concentration on steel reinforcement exceeds a threshold value. The various input parameters considered in the model are surface chloride concentration (Cs), chloride threshold value (Cth), Concrete cover (X), reference diffusion coefficient (Dref), age (t), reference age (tref), diffusion decay index (m) and monthly temperature and relative humidity correction factors f(T) and f(h) respectively; to reference diffusion coefficient. For prediction of corrosion initiation time temperature and relative humidity data collected by India metrological Department is used and all other parameters are assumed same. A large variation in corrosion initiation time is found and therefore it becomes necessary to consider the temperature and relative humidity data in a region. Life-365 considers fully saturated condition of concrete and thus underestimates the corrosion initiation time of a reinforced concrete member. The deterministic approach uses mean values of the parameters and provides a 50% probability of corrosion initiation but the probabilistic approach provides expected time of first corrosion for chosen risk of corrosion and also gives sensitivity of parameters to probability of corrosion. Corrosion initiation time in ascending order is found at Colaba, Kanyakumari, Santacruz, Chennai and Vishakhapatnam. Corrosion initiation time is useful for owner, designer, or to an organization to take decision in time of priority of repairs, repair strategy, corrosion protection in order to optimize maintenance planning and budgeting. Planned maintenance at the optimum time is the safest and most cost effective approach.

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The Effect of Shape on Chloride Penetration of Circular Reinforcement Concrete Columns and Its Durability Design

Applied Sciences ◽

10.3390/app10020459 ◽

2020 ◽

Vol 10 (2) ◽

pp. 459

Author(s):

Gu Yin ◽

Li Pan

Keyword(s):

Diffusion Model ◽

Chloride Diffusion ◽

Model Parameters ◽

Geometrical Shape ◽

Initiation Time ◽

Minimum Thickness ◽

Corrosion Initiation ◽

Durability Design ◽

Corrosion Initiation Time ◽

The Impact

The reinforced concrete (RC) circular element is usually simplified as slab one on the issue of chloride diffusion simulation, without considering the effect of the geometrical shape. In the paper, a modified slab diffusion model is proposed for circular section. A formulation for estimating the error caused by neglecting the effect of shape on chloride diffusion is derived. The formulation demonstrates that radius significantly affect the error. When shape is neglected, the effects of model parameters, including the diffusion coefficient, radius, cover concrete thickness and age factor, on the corrosion initiation time are investigated. The result shows the radius has a slight effect on calculating the corrosion initiation time compared with other model parameters. Furthermore, the influence of shape on estimating on reliability index for different service time is also discussed. A guideline is proposed for properly using the modified slab diffusion model instead of the original one to predict service life. Finally, the impact of the shape of the RC circular column on the durability design against chloride corrosion is studied. The design result when the column is simplified as a slab element indicates a lower required minimum concrete cover thickness. The minimum thickness should be improved by 5 mm as a conservative choice based on the result of the slab element.

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Chloride-Induced Corrosion of Steel in Concrete: An Overview on Chloride Diffusion and Prediction of Corrosion Initiation Time

International Journal of Corrosion ◽

10.1155/2017/5819202 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9 ◽

Cited By ~ 19

Author(s):

Muhammad Umar Khan ◽

Shamsad Ahmad ◽

Husain Jubran Al-Gahtani

Keyword(s):

Diffusion Models ◽

Chloride Diffusion ◽

Second Law ◽

Chloride Ingress ◽

Initiation Time ◽

Chloride Binding ◽

Rc Structures ◽

Corrosion Initiation ◽

Corrosion Initiation Time ◽

Corrosion Of Steel

Initiation of corrosion of steel in reinforced concrete (RC) structures subjected to chloride exposures mainly depends on coefficient of chloride diffusion, Dc, of concrete. Therefore, Dc is one of the key parameters needed for prediction of initiation of reinforcement corrosion. Fick’s second law of diffusion has been used for long time to derive the models for chloride diffusion in concrete. However, such models do not include the effects of various significant factors such as chloride binding by the cement, multidirectional ingress of chloride, and variation of Dc with time due to change in the microstructure of concrete during early period of cement hydration. In this paper, a review is presented on the development of chloride diffusion models by incorporating the effects of the key factors into basic Fick’s second law of diffusion. Determination of corrosion initiation time using chloride diffusion models is also explained. The information presented in this paper would be useful for accurate prediction of corrosion initiation time of RC structures subjected to chloride exposure, considering the effects of chloride binding, effect of time and space on Dc, and interaction effect of multidirectional chloride ingress.

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CORROSION INITIATION TIME OF REINFORCED CONCRETE STRUCTURES IN MARINE ENVIRONMENT — A PROBABILISTIC APPROACH

International Journal of Reliability Quality and Safety Engineering ◽

10.1142/s0218539308002952 ◽

2008 ◽

Vol 15 (02) ◽

pp. 93-99

Author(s):

A. SRIVIDYA ◽

SATISH B. ALLAMPALLEWAR

Keyword(s):

Probabilistic Approach ◽

Chloride Concentration ◽

Cost Effective ◽

Threshold Value ◽

Steel Reinforcement ◽

Initiation Time ◽

Expected Time ◽

Corrosion Initiation ◽

Cost Effective Approach ◽

Corrosion Initiation Time

An approximate explicit method from literature to estimate the corrosion initiation time of steel reinforcement in concrete is developed to incorporate random variables which affect the diffusion rate. The method accounts for uncertainties of input parameters and predicate expected time of first corrosion for the chosen risk of corrosion and its variance. Method is also utilized to rank the sensitive parameters to initiate steel reinforcement corrosion. Corrosion is initiated when the chloride concentration on steel reinforcement exceeds a threshold value. Corrosion initiation time is useful for owner, designer, or to an organization to take decision in time of priority of repairs, repair strategy, corrosion protection in order to optimize maintenance planning and budgeting. Planned maintenance at the optimum time is the safest and most cost effective approach.

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Corrosion performance of steel reinforcement in concrete admixed with magnesium chloride and sulphate

Anti-Corrosion Methods and Materials ◽

10.1108/acmm-08-2019-2163 ◽

2020 ◽

Vol 67 (1) ◽

pp. 106-118 ◽

Cited By ~ 3

Author(s):

Raghu Babu U. ◽

Kondraivendhan B.

Keyword(s):

Electrical Resistivity ◽

Cementitious Material ◽

Corrosion Mechanism ◽

Aluminium Content ◽

Water Reinforcement ◽

Internal Source ◽

Initiation Time ◽

Content Type ◽

Corrosion Initiation ◽

Corrosion Initiation Time

Purpose Besides with a large amount of Na+ and Cl− ions in seawater, the presence of Mg+2 and SO4−2 ions builds more complex corrosion mechanism. This paper aims to investigate the corrosion of embedded reinforcement in concrete with the environment of both Cl− and SO4−2 anions associated Mg+2 cation. Design/methodology/approach The concrete specimens were prepared by using ordinary Portland cement (OPC), and OPC blended with metakaolin (MK) for water to cementitious material ratio (w/cm) 0.48 and 0.51. The concrete mixes were contaminated with the addition of MgCl2 alone and combined MgCl2 and MgSO4 in mix water. Reinforcement corrosion was evaluated by half-cell potential and corrosion current densities (Icorr) at regular intervals. Moreover, the influence of cementitious material type, salt type and w/cm ratio on electrical resistivity of concrete was also investigated. The statistical models were developed for electrical resistivity as a function of calcium to aluminium content ratio, compressive strength, w/cm ratio and age of concrete. Findings Although the corrosion initiation time increases in the concomitant presence of MgSO4 and MgCl2 as internal source compared to MgCl2, Icorr values are higher in both OPC and MK blended concrete. However, electrical resistivity decreased with addition of MgSO4. MK blended concrete performed better with increased resistivity, corrosion initiation time and decreased Icorr values. Originality/value This study reports statistical distributions for scattered Icorr of rebar in different concrete mixtures. Stepwise regression models were developed for resistivity by considering the interactions among different variables, which would help to estimate the resistivity through basic information.

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Acelerated Test Methods: Determining the Diffusion Coefficient of Concretes in the Saturated Condition

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.372.91 ◽

2017 ◽

Vol 372 ◽

pp. 91-100

Author(s):

Tassia Fanton ◽

João A.M. Bender ◽

Leandro G. Blois ◽

Franciele Müller ◽

André T.C. Guimarães

Keyword(s):

Diffusion Coefficient ◽

Standardized Tests ◽

Chloride Concentration ◽

Test Methods ◽

Chloride Penetration ◽

Chloride Diffusion ◽

Chloride Diffusion Coefficient ◽

Reinforced Concrete Structure ◽

Saturated Condition ◽

Pozzolanic Cement

The chloride diffusion coefficient indicates the capacity of a particular type of concrete to resist chloride penetration and is therefore used to predict the service life of a particular reinforced concrete structure exposed to environments containing this type of aggressive agent. Its experimental determination is time-dependent and time-consuming. For that reason, our study analyzes the characteristic behavior of the diffusion coefficient (D) of concretes in the saturated condition by testing higher NaCl concentrations and lower contamination ages than those used in standardized tests, in addition, the objective is to analyze the behavior of surface chloride concentration (Cs) over time. Therefore, it was concluded that for concrete dosed with pozzolanic cement, the Cs value varied with increasing tendency at higher ages. In addition, the D value obtained by the proposed method presented values close to those obtained by standardized tests at contamination ages of 21 and 35 days.

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Experimental Study on Effective Chloride Diffusion Coefficient of Cement Mortar by Different Electrical Accelerated Measurements

Crystals ◽

10.3390/cryst11030240 ◽

2021 ◽

Vol 11 (3) ◽

pp. 240

Author(s):

Jianlan Chen ◽

Jiandong Wang ◽

Rui He ◽

Huaizhu Shu ◽

Chuanqing Fu

Keyword(s):

Diffusion Coefficient ◽

Cement Mortar ◽

Early Stage ◽

Chloride Concentration ◽

Chloride Diffusion ◽

Chloride Diffusion Coefficient ◽

Cement Ratio ◽

Water To Cement Ratio ◽

Good Consistency ◽

Determination Methods

This study investigated the effective chloride diffusion coefficient of cement mortar with different water-to-cement ratio (w/c) under electrical accelerated migration measurement. The cumulative chloride concentration in anode cell solution and the cumulative chloride concentration drop in the cathode cell solution was measured by RCT measurement and the results were further used to calculate the chloride diffusion coefficient by Nordtest Build 355 method and Truc method. The influence of w/c on cement mortar’s chloride coefficient was investigated and the chloride diffusion coefficient under different determination methods were compared with other researchers’ work, a good consistency between this work’s results and literatures’ results was obtained. The results indicated that the increased w/c of cement mortar samples will have a higher chloride diffusion coefficient. The cumulative chloride concentration drop in the cathode cell solution will have deviation in early stage measurement (before 60 h) which will result in overestimation of the effective chloride diffusion coefficient.

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Numerical Simulation of Non-Uniformly Distributed Corrosion in Reinforced Concrete Cross-Section

Materials ◽

10.3390/ma14143975 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3975

Author(s):

Magdalena German ◽

Jerzy Pamin

Keyword(s):

Reinforced Concrete ◽

Cross Section ◽

Chloride Transport ◽

Chloride Concentration ◽

Corrosion Current ◽

Chloride Diffusion ◽

Chloride Diffusion Coefficient ◽

Initiation Phase ◽

Chloride Corrosion ◽

Cover Thickness

Reinforced concrete structures can be strongly damaged by chloride corrosion of reinforcement. Rust accumulated around rebars involves a volumetric expansion, causing cracking of the surrounding concrete. To simulate the corrosion progress, the initiation phase of the corrosion process is first examined, taking into account the phenomena of oxygen and chloride transport as well as the corrosion current flow. This makes it possible to estimate the mass of produced rust, whereby a corrosion level is defined. A combination of three numerical methods is used to solve the coupled problem. The example object of the research is a beam cross-section with four reinforcement bars. The proposed methodology allows one to predict evolving chloride concentration and time to reinforcement depassivation, depending on the reinforcement position and on the location of a point on the bar surface. Moreover, the dependence of the corrosion initiation time on the chloride diffusion coefficient, chloride threshold, and reinforcement cover thickness is examined.

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