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.

scholarly journals Durability of self-healing concrete

2019 ◽  
Vol 289 ◽  
pp. 01003 ◽  
Author(s):  
Nele De Belie ◽  
Bjorn Van Belleghem ◽  
Yusuf Çağatay Erşan ◽  
Kim Van Tittelboom
Keyword(s):  
Corrosion Behaviour ◽  
Healing Process ◽  
Chloride Ingress ◽  
Self Healing ◽  
Crack Healing ◽  
Nacl Solution ◽  
Visual Damage ◽  
Chloride Profiles ◽  
Cracked Specimens ◽  
Concrete Matrix

Application of self-healing concrete reduces the need for expensive maintenance and repair actions. However, the durability of self-healing concrete has only been scarcely investigated. Here, recent results are presented regarding the resistance of self-healing concrete to chloride ingress. For self-healing concrete with macro-encapsulated polyurethane, chloride profiles and electron probe microanalysis indicated that this mechanism was efficient to reduce the chloride penetration into the crack and from the crack into the concrete matrix [1]. Furthermore, the corrosion behaviour of reinforced concrete specimens subjected to cyclic exposure with a NaCl solution was studied [2]. The electrochemical measurements indicated that autonomous crack healing could significantly reduce the corrosion in the propagation stage. No visual damage could be detected on the rebars after 44 weeks of exposure. On the contrary, cracked specimens without integrated self-healing mechanism, reached a state of active corrosion after 10 weeks of exposure and after 26 weeks clear pitting damage was observed on the rebars. While self-healing by encapsulated polyurethane is complete after one day, bacteria-based products take several weeks to heal a 300 µm crack. Bacterial granules containing denitrifying cultures released nitrite as an intermediate metabolic product which protected the reinforcement during the crack healing process [3].

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.

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.

scholarly journals A Thermo-Hygro-Coupled Model for Chloride Penetration in Concrete Structures

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Nattapong Damrongwiriyanupap ◽  
Suchart Limkatanyu ◽  
Yunping Xi
Keyword(s):  
Reinforced Concrete ◽  
Concrete Structures ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Heat Diffusion ◽  
Chloride Diffusion ◽  
Actual Condition ◽  
Reinforced Concrete Structures ◽  
Coupled Transport ◽  
Governing Equations

Corrosion damage due to chloride attack is one of the most concerning issues for long term durability of reinforced concrete structures. By developing the reliable mathematical model of chloride penetration into concrete structures, it can help structural engineers and management agencies with predicting the service life of reinforced concrete structures in order to effectively schedule the maintenance, repair, and rehabilitation program. This paper presents a theoretical and computational model for chloride diffusion in concrete structures. The governing equations are taking into account the coupled transport process of chloride ions, moisture, and temperature. This represents the actual condition of concrete structures which are always found in nonsaturated and nonisothermal conditions. The fully coupled effects among chloride, moisture, and heat diffusion are considered and included in the model. The coupling parameters evaluated based on the available material models and test data are proposed and explicitly incorporated in the governing equations. The numerical analysis of coupled transport equations is performed using the finite element method. The model is validated by comparing the numerical results against the available experimental data and a good agreement is observed.

Modeling of chloride penetration in concrete structures under freeze-thaw cycles

2019 ◽  
Vol 38 (1) ◽  
pp. 127-147 ◽  
Author(s):  
H’mida Hamidane ◽  
Ayman Ababneh ◽  
Ali Messabhia ◽  
Yunping Xi
Keyword(s):  
Finite Element ◽  
Temperature Variation ◽  
Concrete Structures ◽  
Chloride Penetration ◽  
Life Assessment ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Variable Boundary ◽  
Content Type ◽  
Freeze Thaw

Purpose The purpose of this paper is to develop a method for predicting the chloride ingress into concrete structures, with an emphasis on the low temperature range where freeze-thaw cycles may cause damage. Design/methodology/approach The different phenomena that contribute to the rate and amount of transported chlorides into concrete, i.e., heat transfer, moisture transport and chloride diffusion are modeled using a two-dimensional nonlinear time dependent finite element method. In modeling the chloride transport, a modified version of Fick’s second law is used, in which processes of diffusion and convection due to water movement are taken into account. Besides, the effect of freeze-thaw cycles is directly incorporated in the governing equation and linked to temperature variation using a coupling term that is determined in this study. The proposed finite element model and its associated program are capable of handling pertinent material nonlinearities and variable boundary conditions that simulate real exposure situations. Findings The numerical performance of the model was examined through few examples to investigate its ability to simulate chloride penetration under freeze-thaw cycles and its sensitivity to factors controlling freeze-thaw damage. It was also proved that yearly temperature variation models to be used in service life assessment should take into account its cyclic nature to obtain realistic predictions. Originality/value The model proved promising and suitable for chloride penetration in cold climates.

Influence of Ox Blood on Water Absorption of and Chloride Penetration into Concrete

2011 ◽  
Vol 261-263 ◽  
pp. 496-500
Author(s):  
Jian Guang Xu ◽  
Tie Jun Zhao ◽  
Peng Zhang ◽  
Rong Jiang
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Concrete Structures ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Water Repellent ◽  
Animal Blood ◽  
Animal Fats ◽  
Historical Monuments ◽  
Natural Stones

Many concrete structures can not reach their designed service life because of their poor durability. Water and aggressive substances such as chloride ions are prerequisite to the deterioration of concrete. In aggressive environments, water repellent treatment is an effective path to delay the repair and improve the durability of concrete structures. Thousands of years ago, people used oils, animal fats or wax to treat the surface of natural stones, bricks or put some animal blood in mortar to make them water repellent. Many historical monuments were protected in these old methods. In this paper, different amounts of ox blood had been added in concrete. Compressive strength, water absorption and chloride penetration tests had been conducted. In this way, the influence of ox blood on water absorption of and chloride penetration into concrete had been investigated. The results indicated that the compressive strength of concrete with addition of ox blood decreased. And water absorption and chloride penetration into concrete were effectively reduced by adding some amounts of ox blood. The concrete with the surface abraded off 5mm, 15mm and 25mm which were mixed with ox blood had higher water absorption than concrete without abrasion.

Effects of Mineral Admixtures on Carbonation and Chloride Ingress of Concrete

2012 ◽  
Vol 212-213 ◽  
pp. 878-882 ◽  
Author(s):  
Abuduhelili Haibier ◽  
Yong Xin Wu
Keyword(s):  
Concrete Structures ◽  
Steel Corrosion ◽  
Chloride Ion ◽  
Chloride Penetration ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Chloride Ingress ◽  
Test Results ◽  
Concrete Carbonation ◽  
Carbonation Process

Reinforcement corrosion is one important factor affecting the durability and safety of reinforced concrete structures. Concrete carbonation and chloride ion penetration is the main cause leading to steel corrosion, also important indicators affecting the service life of concrete structures. An accelerated carbonation experiment and Chloride penetration experiment was carried out on ordinary Portland cement (OPC) concrete and admixture concrete in various conditions. Eight concrete specimens of different mixture properties were tested in experiment. Resistance of OPC concrete system with and without mineral admixture (fly ash, slag) and air-entraining agent against carbonation was investigated. Besides, the influence of mineral admixture on the chloride penetration was also studied. The carbonation process and the factors affecting concrete carbonation are discussed according to test results. The test results were presented and they were in good agreement with the results of previous research.

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.

Durability of Concrete under Combined Exposure Conditions of Chlorides and Sulfates

2016 ◽  
Vol 711 ◽  
pp. 319-326 ◽  
Author(s):  
Kwang Jin In ◽  
Y.R. Jiang ◽  
Sang Hwa Jung ◽  
Myung Kue Lee ◽  
Sung Won Yoo ◽  
...  
Keyword(s):  
Concrete Structures ◽  
Construction Materials ◽  
Chloride Content ◽  
Chloride Penetration ◽  
Experimental Program ◽  
Chloride Ingress ◽  
Combined Exposure ◽  
Realistic Assessment ◽  
Set Up ◽  
Penetration Behavior

Concrete structures are generally subjected to serious deterioration under harsh environment, even though the concrete materials exhibit inherently higher durability than any other construction materials. The service life of concrete structures is directly affected by the durability performance under various conditions. In this regard, many studies have been conducted on the deterioration of concrete structures under various environmental conditions. However, previous studies were confined mostly to the deterioration of concrete structures under single deteriorating factor such as chloride ingress only or sulfate attack only, although real environment is actually a combination of such factors. The purpose of the present study is, therefore, to explore the effects of combined deterioration due to chlorides and sulfates in concrete structures. To this end, comprehensive experimental program has been set up to observe the chloride penetration behavior under combined deterioration conditions of chlorides and sulfates. The test results indicate that the chloride penetration is more pronounced for the case of combined attacks of chloride and sulfates than the case of single chloride attack. The surface chloride content is found to increase with time and this phenomenon is also more pronounced under the combined exposure of chlorides and sulfates. The present study may allow more realistic assessment of durability for such concrete structures which are subjected to combined attacks of chlorides and sulfates.

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.

Sign in / Sign up

Export Citation Format

Share Document