scholarly journals Modelling of chloride ingress in concrete based on benchmarking field results

2018 ◽  
Vol 199 ◽  
pp. 01005 ◽  
Author(s):  
E.A.B. Koenders
Keyword(s):  
Service Life ◽  
Structural Design ◽  
Numerical Models ◽  
Concrete Structures ◽  
Research Community ◽  
Chloride Ions ◽  
Analytical Models ◽  
Design Stage ◽  
Engineering Practice ◽  
Chloride Ingress

Modelling the ingress of chloride ions into the cover of a concrete structure is a phenomenon that is gaining an increasing attention of the research community, but even more, from the engineering practice. As the mechanism that drives the ingress of chlorides is implicitly responsible for the service-life of concrete structures, its input parameters are a major issue whenever predicting the service-life of new concrete structures. In this paper most relevant parameters involved in the evaluation of chloride ingress models are discussed and related to the benchmark activities that currently run in RILEM TC 270-CIM on benchmarking Chloride Ingress Models. The results provide an overview of the models used in the structural design stage, mostly analytical models, and in the rehabilitation stage, mostly numerical models.

Influence of Boundary and Initial Condition on Durability of Concrete Structures Exposed to Chloride Environment

2012 ◽  
Vol 166-169 ◽  
pp. 1946-1953
Author(s):  
Xin Gang Zhou ◽  
Fang Zhao
Keyword(s):  
Service Life ◽  
Initial Conditions ◽  
Error Function ◽  
Concrete Structures ◽  
Life Time ◽  
Chloride Penetration ◽  
Analytical Models ◽  
Chloride Ingress ◽  
Chloride Environment ◽  
Penetration Profile

According to investigations of apparent surface chloride contents and chloride penetration profile of concrete structures exposed to chloride environment, the influences of boundary and initial conditions, geometry parameters such as the geometry dimension and section shape, etc. were discussed. Based on the Fick’s second law of diffusion and different boundary and initial conditions, different analytical models to predict the chloride penetration profile in concrete structural members with different boundary and initial conditions were derived. Some calculations examples were made using those analytical models. Computational results show that the boundary and initial conditions have remarkable influences on chloride penetration profile and service life time of concrete structures. Using prevailing error-function solution model based on the semi-infinite assumption of chloride ingress, the prediction of service life time of concrete structures are over evaluated, in particular for the steel reinforcement in corner of the section. Some modify coefficients should be taken into consideration, concerning the influences of boundary and initial conditions.

Diffusivity Resistance of Concrete Systems in Chloride Rich Environment for Corrosion Protection of Embedded Steel Bars

2013 ◽  
Vol 831 ◽  
pp. 3-8
Author(s):  
Suad Khalid Al-Bahar ◽  
Safaa M. Abdul Salam ◽  
Adel M. Husain
Keyword(s):  
Service Life ◽  
Concrete Structures ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Steel Reinforcement ◽  
Mineral Admixtures ◽  
Chloride Ingress ◽  
Corrosion Initiation ◽  
Chloride Ion Penetration ◽  
Ion Penetration

Improving concrete performance and minimizing corrosion-induced deterioration of reinforced concrete structures are mandated Building Codes Practices and Specifications in arid regions such as the Arabian Gulf. Concrete structures resist corrosion due to the passivating properties of the hydrated cement around the steel reinforcement created by the high alkaline environment within the composite structure (pH > 12). However, the presence of chloride ions in the pore structure of the concrete destroys this passivating layer, which makes the steel reinforcement vulnerable to chloride-induced corrosion attack that accelerates degradation and deterioration of concrete structures. Corrosion activities-related tests such as Time-to-Corrosion Initiation (Modified ASTM G-109)6, and Corrosion Rate Test (Lollipop Test), can be effectively used to monitor the behavior of corrosion development, while chloride ingress characteristics tests such as Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration ASTM C-1202-91)7, and the Resistance of Concrete to Chloride Ion Penetration (AASHTO T 259-80)8, are applied to evaluate the rate at which chloride ions can diffuse through concrete to onset the time-to-corrosion initiation, which will impact the structure service life and compromise its sustainability. Efforts have been made by scientists to develop mathematical simulation models that predict the service life of the structure based on Ficks Second Law for semi-finite diffusion of chloride ions, concentrated at different concrete depths. The study concluded that mineral admixtures have contributed to the enhancement of concrete performance and its resistance to chloride diffusivity, as well when in combination with corrosion-inhibiting admixture such as calcium nitrite.

scholarly journals The cover thickness design of concrete structures subjected to chloride ingress from RBDO solution technique

2020 ◽  
Vol 13 (5) ◽  
Author(s):  
Giovanni Pais Pellizzer ◽  
Edson Denner Leonel
Keyword(s):  
Concrete Structures ◽  
Weighted Average ◽  
Threshold Level ◽  
Chloride Ions ◽  
Structural Safety ◽  
Solution Technique ◽  
Chloride Ingress ◽  
Initiation Stage ◽  
Cover Thickness ◽  
Propagation Stage

Abstract: Diffusion is the principal transport mechanism of chloride ions into concrete pores. The chlorides trigger the reinforcements’ depassivation when its concentration at the concrete/reinforcement interface reaches the threshold level. Thus, the depassivation defines the initiation stage end and the propagation stage start. The structural safety reduces widely during the propagation stage because of the various deleterious mechanisms triggered by reinforcement’s corrosion. Therefore, the engineers should accurately predict and prevent the propagation stage start. The literature describes several models for evaluating the end of the initiation stage. However, few of them applies the Boundary Element Method (BEM) for this purpose, despite its known accuracy. Besides, enormous randomness affect the phenomenon. Thus, it is adequately handled solely in the probabilistic context. Optimisation techniques may be coupled in the problem modelling to propose adequate cover thickness values accounting for probabilities of failure. This study presents a Reliability-Based Design Optimisation (RBDO) approach for designing accurately the cover thickness of concrete structures subjected to chloride ingress. The BEM handles the diffusion modelling whereas the Monte Carlo simulation assesses the probabilities of failure. The RBDO is formulated in the context of Weighted Average Simulation Method (WASM), which requires only one assessment of the reliability analysis. It leads to a reliable and computationally efficient solution technique. The problem formulation and the implemented solution scheme are described herein. Moreover, one application is presented, in which the design results are interpreted properly.

Analysis of Service Life of Surface Coated-Concrete Structures Considering Climate Change and Chloride Ingress

2020 ◽  
Vol 842 ◽  
pp. 299-305
Author(s):  
Xiao Yong Wang
Keyword(s):  
Climate Change ◽  
Service Life ◽  
Surface Coating ◽  
Concrete Structures ◽  
Parameter Analysis ◽  
Chloride Ingress ◽  
Arrhenius Law ◽  
Chloride Diffusivity ◽  
Chloride Profile ◽  
Marine Concrete

Mortar surface coating is widely used as a finishing material to extend the service life and improve chloride ingression resistance of marine concrete structures. This study proposes a model for estimating the service life of surface-coated marine concrete considering climate change. First, the increase of chloride diffusivity due to climate change is considered using Arrhenius’ law. A two-layered chloride ingress model is used to analyze chloride profile. The probability-based approach is used to find the service life of concrete structures. Second, parameter analysis is performed considering the effects of various factors on service life. The influences of thickness and chloride diffusivity of the coating and substrate concrete on service life are highlighted. The reduction of service life due to climate change is clarified based on the regression of results of parameter analysis. For marine concrete with 50 years’ service life, 6% service life reduction occurs because of climate change.

scholarly journals Perpendicular-to-crack chloride ingress in cracked and autonomously healed concrete

2018 ◽  
Vol 199 ◽  
pp. 02011
Author(s):  
Bjorn Van Belleghem ◽  
Philip Van den Heede ◽  
Kim Van Tittelboom ◽  
Nele De Belie
Keyword(s):  
Concrete Structures ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Chloride Ingress ◽  
Crack Healing ◽  
Crack Location ◽  
Spray Method ◽  
Surface Visualization ◽  
Chloride Profiles ◽  
Concrete Matrix

Cracks in reinforced concrete structures exposed to a marine environment or de-icing salts can cause major durability issues due do accelerated ingress of chloride ions. In this study, the influence of autonomous crack healing by means of encapsulated polyurethane on the chloride ingress perpendicular to cracks was evaluated. This was done quantitatively by determining perpendicular-to-crack chloride profiles by means of profile grinding followed by potentiometric titration and qualitatively through visualization of the chloride penetration front by means of the AgNO3 spray method. The resulting chloride profiles showed that the healing mechanism was able to reduce the chloride concentrations in the direct vicinity of the crack to a large extent and to reduce the perpendicular-to-crack chloride penetration, especially further away from the exposed surface. Visualization of the chloride penetration front showed some variation in crack healing. For some healed samples almost no additional chloride ingress was found compared to uncracked samples, others showed a slightly enhanced ingress at the crack location but less perpendicular-to-crack chloride penetration compared to untreated cracked samples. Generally, the reduced amount of chlorides present in the concrete matrix due to crack healing will enhance the durability and service life of concrete structures.

Achieving Concrete Durability in Chloride Exposures

2016 ◽  
Vol 711 ◽  
pp. 607-614 ◽  
Author(s):  
R. Douglas Hooton
Keyword(s):  
Service Life ◽  
Predictive Models ◽  
Performance Test ◽  
Concrete Structures ◽  
Test Methods ◽  
Transport Processes ◽  
Chloride Ingress ◽  
Concrete Durability ◽  
Life Predictions ◽  
Construction Defects

Obtaining durability in concrete structures over a long service life in chloride exposures requires knowledge of the concrete properties, relevant transport processes, depths of cover as well as minimization of cracking and construction defects. For example, imperfect curing can result in depth-dependent effects of the concrete cover’s resistance to chloride ingress. Several service life models with various levels of sophistication exist for prediction of time-to-corrosion of concrete structures exposed to chlorides. The model inputs have uncertainty associated with them such as boundary conditions (level of saturation and temperature), cover depths, diffusion coefficients, time-dependent changes, and rates of buildup of chlorides at the surface. The performance test methods used to obtain predictive model inputs as well as how models handle these properties have a dramatic impact on predicted service lives. Very few models deal with the influence of cracks or the fact that concrete in the cover zone will almost certainly have a higher diffusion coefficient than the bulk concrete as the result of imperfect curing or compaction. While many models account for variability in input properties, they will never be able to account for extremes in construction defects. Therefore, to ensure the reliability of service life predictions and to attain a concrete structure that achieves its predicted potential, designers, contractors and suppliers need to work together, using proper inspection, to ensure proper detailing, minimize defects, and adopt adequate, yet achievable, curing procedures. As well, concrete structures are often exposed to other destructive elements in addition to chlorides (eg. freezing or ASR) and this adds another level of complexity since regardless of cause, cracks will accelerate the ingress of chlorides. These issues are discussed along with the need to use performance-based specifications together with predictive models.

scholarly journals Probability-Based Sensitivity of Service Life of Chloride-Attacked Concrete Structures with Multiple Cover Concrete Repairs

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Aruz Petcherdchoo
Keyword(s):  
Sensitivity Analysis ◽  
Service Life ◽  
Concrete Structures ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Expected Number ◽  
Probabilistic Data ◽  
Free Condition ◽  
Corrosion Initiation ◽  
Cover Concrete

This paper presents probabilistic and sensitivity analysis of service life (or time to repairs) for attaining corrosion-free condition of concrete structures under chloride attack. Four groups of probabilistic parameters are determined, i.e., (1) time-dependent chloride content, (2) mean and median of corrosion initiation and repair application times, (3) percent confidence of repairs, and (4) total expected number of repairs. To achieve this, this paper proposes a computational approach and probabilistic data. The proposed approach, which combined the Latin Hypercube technique with the Crank–Nicolson-based finite difference approach, is developed for predicting probabilistic chloride diffusion in concrete with repairs by cover concrete replacement. Probabilistic data of four governing random variables (surface chloride, diffusion coefficient, concrete cover depth, and critical chloride) and six repair strategies for corrosion-free condition are introduced. Numerical assessment is then shown. From the study, it is revealed that the reduction of the amount of chloride ions at the threshold depth due to using higher depth of cover concrete repairs is better than that using higher quality of repair materials. However, the excessive depth of repairs is not always recommended due to another control factor, such as the immediate amount of chloride ions at the repair depth, cost of repairs, etc. From the sensitivity analysis, the cover depth is found to be the most important parameter in the design of chloride-attacked concrete structures to extend the corrosion initiation and repair application times and to reduce the total expected number of repairs.

scholarly journals Parallel Code Execution as a Tool for Enhancement of the Sustainable Design of Foundation Structures

2021 ◽  
Vol 13 (3) ◽  
pp. 1145
Author(s):  
Jiri Brozovsky ◽  
Radim Cajka ◽  
Zdenka Neuwirthova
Keyword(s):  
Service Life ◽  
Civil Engineering ◽  
Sustainable Design ◽  
Numerical Models ◽  
Computer Hardware ◽  
Engineering Practice ◽  
Engineering Structures ◽  
Model Case ◽  
In Situ Experiments ◽  
Complex Models

Civil engineering structures are always in interaction with the underlying parts of the Earth. This form of interaction results in deformations and stresses that affect the service life of structures. Long and predictable service life is one of important aspects of sustainable design. Thus, good knowledge of the interaction effects is an essential part of sustainable design. However, to obtain this information, the use of complex numerical models is often necessary. In many cases, the creation and analysis of such complex models are not possible with the tools usually available in civil engineering practice. Technically, the necessary software and computer hardware exist, but their use for such tasks is still very infrequent and includes many challenges. The main aim of this article was thus to propose an approach of numerical analysis that utilizes parallel supercomputers and software based on the finite element method. The paper concentrated on the feasibility of the solution and on calculation times, because these aspects are usually the main reasons why engineers in practice tend to reject these approaches. The approach was demonstrated on a model case that was compatible with actual in situ experiments executed by the author’s team, and thus the validity of the computed results is verifiable. Limitations of the proposed approach are also discussed.

scholarly journals Durability design of concrete structures, Part 1: Analysis fundamentals

2009 ◽  
Vol 7 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Radomir Folic
Keyword(s):  
Service Life ◽  
Limit State ◽  
Natural Extension ◽  
Concrete Structures ◽  
International Committee ◽  
Chloride Ingress ◽  
Freezing And Thawing ◽  
Model Code ◽  
Design Service Life ◽  
Present Design

Concrete structures (CS) are designed so that they can satisfy requirements regarding safety, serviceability, durability and aesthetics throughout their design service life. Present design procedures regarding CS required by national or international codes and standards such as Model Code Euro International Committee of Concrete (1993) now Federation Internationale du Beton (FIB), Eurocodes, ACI, RILEM, etc. are predominantly based on strength principles and limit state formulation. The durability aspect is a natural extension of the classical resistance verification where deterioration effects are normally neglected. The reliability is assessed through the given performance that must be delivered within the design service life, the so-called performance-based design. This approach can be adopted for a performance based on service life design. In the recent years design is related to durability through the analysis of carbonation, resistance to chloride ingress, improved freezing and thawing resistance, etc. The review of literature and some recommendations are presented referring to the design of structures aiming to attain greater durability of CS. The accent is put on the theory of reliability, failure probability and service life probability. The basics of this analysis are given through the principles of performances and service life, and deterministic and scholastic methods using the lifetime safety factor.

scholarly journals Modelling of Deterioration Effects on Concrete Structures

10.14311/344 ◽  
2002 ◽  
Vol 42 (3) ◽  
Author(s):  
B. Teplý
Keyword(s):  
Service Life ◽  
Probabilistic Approach ◽  
Concrete Structures ◽  
Analytical Models ◽  
Reinforcing Steel

In order to predict the service life of concrete structures models for deterioration effects are needed. This paper has the form of a survey, listing and describing such analytical models, namely carbonation of concrete, ingress of chlorides, corrosion of reinforcing steel and prestressing tendons. The probabilistic approach is applied.

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