scholarly journals A Numerical Study on Chloride Diffusion in Cracked Concrete

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 742
Author(s):  
Qiannan Wang ◽  
Guoshuai Zhang ◽  
Yunyun Tong ◽  
Chunping Gu
Keyword(s):  
Diffusion Process ◽  
Penetration Depth ◽  
Crack Width ◽  
Numerical Study ◽  
Crack Depth ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Cracked Concrete ◽  
Crack Geometry ◽  
Chloride Diffusivity

The cracks in concrete are a fast transport path for chlorides and influence the service life of concrete structures in chloride environments. This study aimed to reveal the effect of crack geometry on chloride diffusion in cracked concrete. The chloride diffusion process in cracked concrete was simulated with the finite difference method by solving Fick’s law. The results showed that the apparent chloride diffusivity was lower in more tortuous cracks, and the cracks with more narrow points also showed lower apparent chloride diffusivity. For tortuous cracks, a higher crack width meant relatively more straight cracks, and consequently, higher apparent chloride diffusivity, while a lower crack width resulted in more tortuous cracks and lower apparent chloride diffusivity. The crack depth showed a more significant influence on the chloride penetration depth in cracked concrete than crack geometry did. Compared with rectangular and V-shaped cracks, the chloride diffusion process in cracked concrete with a tortuous crack was slower at the early immersion age. At the same crack depth, the crack geometry showed a marginal influence on the chloride penetration depth in cracked concrete during long-term immersion.

scholarly journals Simulation of Chloride Diffusion in Cracked Concrete with Different Crack Patterns

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Xiao-Yong Wang ◽  
Li-Na Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Crack Width ◽  
Crack Depth ◽  
Crack Density ◽  
Concrete Structures ◽  
Chloride Concentration ◽  
Numerical Procedure ◽  
Chloride Diffusion ◽  
Cracked Concrete ◽  
Dimensional Finite Element

Chloride-induced corrosion of steel rebar is one of the primary durability problems for reinforced concrete structures in marine environment. Furthermore, if the surfaces of concrete structures have cracks, additional chloride can penetrate into concrete through cracked zone. For chloride ingression into cracked concrete, former researches mainly focus on influence of crack width on chloride diffusion coefficients. Other crack characteristics, such as chloride depth, crack shape (equal-width crack or tapered crack), crack density, and spacing, are not studied in detail. To fill this gap, this paper presents a numerical procedure to simulate chloride ingression into cracked concrete with different crack geometry characteristics. Cracked concrete is divided into two parts, sound zone and cracked zone. For stress-free concrete, the diffusion coefficient of sound zone is approximately assumed to be the same as sound concrete, and the diffusion coefficient of cracked zone is expressed as a piecewise function of crack width. Two-dimensional finite element method is used to determine chloride concentration. It is found that, with the increasing of crack width, crack depth, and crack amount, chloride ingression will aggravate. The analysis results generally agree with experimental results.

scholarly journals The Depth–Width Correlation for Shrinkage-Induced Cracks and Its Influence on Chloride Diffusion into Concrete

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2751
Author(s):  
Hongguang Zhu ◽  
Qingjie Huo ◽  
Jingchong Fan ◽  
Sen Pang ◽  
Hongyu Chen ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Crack Width ◽  
Crack Depth ◽  
Composite Model ◽  
Test Method ◽  
Chloride Diffusion ◽  
Cracked Concrete ◽  
Shrinkage Cracks ◽  
Diffusion Properties

This study examined the depth–width correlation of actual shrinkage-induced cracks and its influence on the diffusion properties of concrete. An experimental setup of restrained slabs was utilized to induce the shrinkage cracks, and the geometry characteristics were quantified with image analysis technology. The results indicated the depth–width scaling λ of shrinkage cracks increases with crack width and was almost constant when the crack width was approximately 0.3 mm or more, and the tip angle of shrinkage cracks is about 1–2 degrees. The diffusion coefficients of concretes were measured by a conductivity test method. A series-parallel composite model with λ was devised to evaluate the diffusivity of shrinking cracked concrete. It was shown that the equivalent diffusion coefficient depended greatly on the crack depth instead of the crack width, and it was found to be a nonlinear relationship versus the width combining with λ . The diffusion coefficient of the crack Dcr was correlated to both crack width and λ , and increased with crack width. When the crack width is higher than 0.2 mm Dcr becomes constant, where the value obtained was 87% of the diffusion coefficient in free solution.

The Effect of Cracks on Chloride Penetration into Concrete

2007 ◽  
Vol 348-349 ◽  
pp. 769-772 ◽  
Author(s):  
In Seok Yoon ◽  
Erik Schlangen ◽  
Mario R. de Rooij ◽  
Klaas van Breugel
Keyword(s):  
Service Life ◽  
Crack Length ◽  
Significant Influence ◽  
Crack Width ◽  
Chloride Transport ◽  
Crack Depth ◽  
Chloride Penetration ◽  
Critical Crack ◽  
Chloride Migration ◽  
Migration Testing

This study is focused on examining the effect of critical crack width in combination with crack depth on chloride penetration into concrete. Because concrete structures have to meet a minimum service-life, critical crack width has become an important parameter. Specimens with different crack width / crack length have been subjected to rapid chloride migration testing (RCM). The results of this study show a critical crack width of about 0.012 mm. Cracks smaller than this critical crack width are considered not to have a significant influence on the rate of chloride transport inwards, while chloride penetration does proceed faster above this critical crack width.

scholarly journals Impact of Cyclic Loading on Chloride Diffusivity and Mechanical Performance of RC Beams under Seawater Corrosion

2017 ◽  
Vol 2017 ◽  
pp. 1-15
Author(s):  
Sen Pang ◽  
Bo Diao ◽  
Yinghua Ye ◽  
Shuxin Chen ◽  
Xin Wang
Keyword(s):  
Cyclic Loading ◽  
Crack Width ◽  
Steel Surface ◽  
Ultimate Load ◽  
Mechanical Performance ◽  
Chloride Content ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Rc Beams ◽  
Chloride Diffusivity

An experimental study was conducted to investigate the impact of cyclic loading on the mechanical performance and chloride diffusivity of RC beams exposed to seawater wet-dry cycles. To induce initial damage to RC beam specimen, cyclic loading controlled by max load and cycles was applied. Then beam specimens underwent 240 wet-dry cycles of seawater. Results show that the chloride content increased as max load and cycle increased. The chloride content at steel surface increased approximatively linearly as average crack width increased. Moreover, the max load had more influence on chloride content at steel surface than cycle. The difference of average chloride diffusion coefficient between tension and compression concrete was little at uncracked position. Average chloride diffusion coefficient increased as crack width increased when crack width was less than 0.11 mm whereas the increasing tendency was weak when crack width exceeded 0.11 mm. The residual yield load and ultimate load of RC beams decreased as max load and cycle increased. Based on univariate analysis of variance, the max load had more adverse effect on yield load and ultimate load than cycle.

Transient Diffusion Behavior of Chloride Ions in Concrete with a Macro Crack

2013 ◽  
Vol 405-408 ◽  
pp. 2671-2676
Author(s):  
Song Mu ◽  
Geert De Schutter ◽  
Jian Zhong Liu
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Concrete Structure ◽  
Crack Width ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Concrete Cracking ◽  
Cracked Concrete ◽  
Diffusion Behavior ◽  
Apparent Diffusion

Nowadays, influences of concrete cracking on durability of concrete structure are widely reported. However, the influence of macro cracks on chloride diffusion of concrete is unknown under the condition of marine submergence. Therefore, the present paper adopted a notch method to study natural chloride diffusion in cracked concrete with a width of above 0.3 mm. The results show Apparent diffusion coefficient of acid soluble chloride rises from 2.66 ×10-12 m2/s to 5.92×10-12 m2/s with increasing crack width from 0 mm to 0.45 mm. Besides, one exponential function was used to describe the piecewise relationship between diffusion coefficient (water or acid soluble chloride) and crack width.

scholarly journals Combined Effect of Initial Curing Temperature and Crack Width on Chloride Penetration in Reinforced Concrete Beams

2018 ◽  
Vol 142 ◽  
pp. 02003
Author(s):  
Lotfi Elkedrouci ◽  
Bo Diao ◽  
Sen Pang ◽  
Yi Li
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Chloride Ion ◽  
Chloride Content ◽  
Chloride Penetration ◽  
Reinforced Concrete Beams ◽  
Curing Temperature ◽  
Chloride Diffusion ◽  
Rc Structures ◽  
Cover Cracking

Reinforced concrete (RC) structures are gradually being degraded all over the world, largely due to corrosion of the embedded steel bars caused by an attack of chloride penetration. Initial curing would be regarded as one factor influencing chloride diffusion in concrete in combination with cover cracking that is also of great attention for reinforced structures. In this study, a non-steady state diffusion test of chloride ion involving RC beam specimens with a water-to-cement ratio of 0.5, initial curing temperatures of 5°C or 20°C and three types of crack widths ranging from 0 to 0.2mm was performed. Chloride content at 5°C or was determined. The results show that the higher chloride content was obtained in condition of crack width large than 0.1mm with low initial curing temperature and there are no obvious differences in chloride content when the crack width was not larger than 0.1mm.

Analysis of Chloride Penetration into the Corner Zone of Concrete Structure Member

2007 ◽  
Vol 348-349 ◽  
pp. 397-400
Author(s):  
Xiao Yong Wang ◽  
Han Seung Lee ◽  
Hai Moon Jung
Keyword(s):  
Service Life ◽  
Diffusion Process ◽  
Concrete Structure ◽  
Chloride Concentration ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Recent Analysis ◽  
Two Dimensional ◽  
One Dimensional ◽  
Dimensional Diffusion

Chloride penetration into concrete is the main cause of steel corrosion in concrete structures exposed to chloride-rich environments. In general, conditions on the diffusion process are dominant among various penetration mechanisms, such as ionic diffusion, capillary sorption, and so on. In recent analysis of current literature, chloride diffusion is as a simplified one-dimensional diffusion process. However, for the rebar in the corner zone of concrete beam, the diffusion belongs to a two-dimensional diffusion. Based on a galerkin finite element method, a two-dimensional diffusion differential equation is built and solved numerically and the different chloride concentration is compared to one dimensional diffusion and two-dimensional diffusion process. The service life of concrete structure members under two-dimensional chloride penetration is predicted by compared with a critical threshold chloride concentration. Compared with general one-dimensional chloride attack, the service life is considerably reduced in a corner zone due to two-dimension penetration.

scholarly journals Reliability algorithms applied to reinforced concrete structures durability assessment

2012 ◽  
Vol 5 (4) ◽  
pp. 440-450 ◽  
Author(s):  
C. G. Nogueira ◽  
E. D. Leonel ◽  
H. B. Coda
Keyword(s):  
Reinforced Concrete ◽  
Diffusion Process ◽  
Concrete Structures ◽  
Threshold Level ◽  
Concrete Cover ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Reinforced Concrete Structures ◽  
Reliability Method ◽  
Corrosion Time

This paper addresses the analysis of probabilistic corrosion time initiation in reinforced concrete structures exposed to ions chloride penetration. Structural durability is an important criterion which must be evaluated in every type of structure, especially when these structures are constructed in aggressive atmospheres. Considering reinforced concrete members, chloride diffusion process is widely used to evaluate the durability. Therefore, at modelling this phenomenon, corrosion of reinforcements can be better estimated and prevented. These processes begin when a threshold level of chlorides concentration is reached at the steel bars of reinforcements. Despite the robustness of several models proposed in the literature, deterministic approaches fail to predict accurately the corrosion time initiation due to the inherently randomness observed in this process. In this regard, the durability can be more realistically represented using probabilistic approaches. A probabilistic analysis of ions chloride penetration is presented in this paper. The ions chloride penetration is simulated using the Fick's second law of diffusion. This law represents the chloride diffusion process, considering time dependent effects. The probability of failure is calculated using Monte Carlo simulation and the First Order Reliability Method (FORM) with a direct coupling approach. Some examples are considered in order to study these phenomena and a simplified method is proposed to determine optimal values for concrete cover.

scholarly journals Effects of load-induced micro-cracks on chloride penetration resistance in different types of concrete

2020 ◽  
Vol 53 (6) ◽  
Author(s):  
Nicoletta Russo ◽  
Matteo Gastaldi ◽  
Pietro Marras ◽  
Luca Schiavi ◽  
Alberto Strini ◽  
...  
Keyword(s):  
Crack Width ◽  
Crack Depth ◽  
Penetration Resistance ◽  
Chloride Penetration ◽  
Migration Test ◽  
Exposure Test ◽  
Durability Design ◽  
Micro Cracks ◽  
Chloride Migration ◽  
Chloride Penetration Resistance

AbstractChloride penetration resistance of concrete is one of the key parameters for the durability design of reinforced concrete structures located in chloride-bearing environments. In all the current available durability models, service life is evaluated considering concrete in uncracked conditions, which is rarely found in practice. This work investigates chloride penetration resistance of concrete in uncracked and micro-cracked configurations, evaluated in terms of chloride migration coefficient through non-steady state migration test (Rapid Chloride Migration test). Prismatic specimens were manufactured considering six different concrete types and two different times of curing. In micro-cracked configuration, cracks were obtained with a specifically developed loading procedure. Micro-cracks were characterized at the end of the exposure test, in terms of crack width at the exposed surface and crack depth. Results showed that cracks were 5–70 μm wide and up to 40 mm deep, always causing an increase in chloride penetration, that should be evaluated considering both crack width and crack depth, with respect to sound conditions. The effects on the chloride penetration seemed to be more pronounced on the more impervious concretes.

Engineering Solution for the Uniform Strength of Partially Cracked Concrete

2005 ◽  
Vol 1919 (1) ◽  
pp. 16-22
Author(s):  
Elin A. Jensen ◽  
Will Hansen ◽  
Rune Brincker
Keyword(s):  
Crack Width ◽  
Master Curve ◽  
Large Scale ◽  
Process Zone ◽  
Concrete Slab ◽  
Crack Depth ◽  
Critical Crack ◽  
Cracked Concrete ◽  
Engineering Solution ◽  
Solution Methodology

Significant computational resources are required to predict the remaining strength from numerical fracture analysis of a jointed plain concrete pavement that contains a partial depth crack. It is, therefore, advantageous when the failure strength can be adequately predicted with an engineering solution. Current engineering or closed-form solutions are based on the elastic effective crack approach with the fracture parameters toughness and critical crack tip opening of concrete. The solutions do not directly consider the effect of the distance to the boundary conditions (restrained slab length) and the cracking process caused by stress softening across the crack. A proposed engineering solution methodology includes these latter variables. The application of the solution is demonstrated on a slab containing a partial depth midslab crack and subjected to in-plane tension. The solution captures the effects of material fracture properties and structural size in terms of crack length and distance from boundary to the crack. The model assumes a bilinear stress–crack width relationship for the fracture process zone. The concrete characteristic length, determined from the fracture energy represented by the first part of the stress–crack width relationship, controls the failure load of a partially cracked concrete slab. A unique master curve between slab strength and crack depth was developed using the results from the numerical analysis. The master curve was verified with results from laboratory testing of large-scale slabs subjected to in-plane tension. The solution methodology can readily be extended to other loading cases.

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