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.

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 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 Probabilistic Analysis of the Durability of Piles with Microcracks Under Chloride Attack

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Wei Shao ◽  
Danda Shi
Keyword(s):  
Diffusion Coefficient ◽  
Probabilistic Analysis ◽  
Probabilistic Method ◽  
Crack Density ◽  
Chloride Concentration ◽  
Experimental Results ◽  
Chloride Diffusion ◽  
Chloride Ingress ◽  
Chloride Attack ◽  
Equivalent Diffusion

AbstractA probabilistic analysis approach for estimating the durability of piles with microcracks under chloride attack is presented. The chloride ingress model is obtained by considering the time-dependent diffusion process. The equivalent diffusion coefficient is derived to investigate the crack effect by introducing the crack effect factor. The fitting formula between the chloride diffusion coefficients and crack widths is established through experimental results, and the proposed equivalent diffusion coefficient is verified by comparison with the experimental results. The probabilistic evaluation of durability of piles with microcracks is performed, and then the parametric analysis is performed to study the effect of main parameters on the failure probability and durability life. The results indicate that the chloride concentration increases rapidly as the crack width increases at the same number of cracks. The durability life greatly reduces with increasing crack density of pile. The durability life predicted by probabilistic method is always less than those by deterministic method at the same condition. The deterministic approach may underestimate the threat of reinforcement corrosion induced by chloride attack, owing to the omission of probabilistic nature of main influencing parameters.

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

Crystals ◽  
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.

scholarly journals Experimental and Simulation Study on Diffusion Behavior of Chloride Ion in Cracking Concrete and Reinforcement Corrosion

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yongchun Cheng ◽  
Yuwei Zhang ◽  
Chunli Wu ◽  
Yubo Jiao
Keyword(s):  
Finite Element ◽  
Prediction Models ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Corrosion Current ◽  
Chloride Diffusion ◽  
Finite Element Models ◽  
Rc Structures ◽  
Cracked Concrete ◽  
Chloride Migration

A chloride ion is a key factor affecting durability of reinforced concrete (RC) structures. In order to investigate chloride migration in cracked concrete, considering the mesoscopic heterogeneity of concrete, concrete modeled here is treated as a four-phase composite consisting aggregate, mortar, crack, and interfacial transition zone (ITZ). In this paper, two-dimensional finite element models of cracked concrete with different crack widths and crack quantity are established and the control parameters are determined based on the nonsteady-state chloride migration (NSSCM) test. In addition, based on the concrete finite element models, influences of crack width, crack quantity, and erosion time on chloride migration behaviors and characteristics are studied. Furthermore, a prediction model of chloride concentration on the simulated surface of a rebar in concrete influenced by different crack states is established. This model is used to derive the corrosion current density and corrosion depth prediction models of a rebar in this paper, which can be used by engineers to estimate the migration behaviors of chloride and rebar corrosion degree in RC structures in a short time and evaluate the duration of RC structures after knowing the status of cracks and chloride diffusion sources.

Boundary Element Analysis of Accelerated Chloride Diffusion in High Performance Concrete

2013 ◽  
Vol 842 ◽  
pp. 151-155
Author(s):  
Yi Wang ◽  
Wo Cheng Hang ◽  
Lu Feng Yang ◽  
Zheng Chen
Keyword(s):  
Diffusion Coefficient ◽  
Boundary Element ◽  
High Performance ◽  
Numerical Solutions ◽  
High Performance Concrete ◽  
Chloride Concentration ◽  
Mineral Admixture ◽  
Mineral Admixtures ◽  
Chloride Diffusion ◽  
Chloride Permeability

This paper aims to analyze accelerated chloride diffusion in high performance concrete (HPC) blended with mineral admixture by using boundary element method (BEM). Rapid chloride permeability test (RCPT) was employed and executed. The experiment proves that the highest resistance to chloride permeability can be acquired in the quaternary-blended concretes (ordinary portland cement + fly ash + blast furnace slag + silica fume). A chloride diffusion BEM model was established according to the diffusion coefficient calculated from the charge passed. The numerical solutions agree with experiments well. It can be inferred that the acceleration degree of RCPT is not the same in different mix proportion. Besides, the results also suggest that the low chloride permeability of the concretes with mineral admixtures may be attributed to the lower diffusion coefficient and the lower surface chloride concentration.

Research on Chloride Diffusion Model of PC with Chloride Attack in Marine Atmosphere Zone

2014 ◽  
Vol 711 ◽  
pp. 481-484
Author(s):  
Yu Chen ◽  
Jie Xu ◽  
Rong Gui Liu ◽  
Su Bi Chen ◽  
Yuan Gao
Keyword(s):  
Prestressed Concrete ◽  
Concentration Distribution ◽  
Concrete Structures ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Ion Concentration ◽  
Chloride Diffusion ◽  
Marine Atmosphere ◽  
Ion Diffusion ◽  
Chloride Ion Diffusion

Based on the existing studies about chloride ion erosion in prestressed concrete structures, this paper intends to discuss the effects of the stress level and environment factors (including temperature and humidity, etc.) on chloride ion diffusion under marine atmosphere zone. The investigation from pre-stressed concrete crossbeams which service for 39 years in Lianyungang Port shows the chloride ion concentration distribution and chloride ion diffusion. According to the chloride ion concentration distribution, it finds that chloride ion concentration values in pre-concrete structures is Cmax,1> Cmax,2. In addition, the free chloride concentration distribution values go down smoothly after the second peak. Therefore, the result shows that the improved model can be used in marine atmosphere zone.

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