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.

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

Materials ◽  
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.

Transport of Water and Chloride Ion in Cement Composites Modified with Graphene Nanoplatelet

2014 ◽  
Vol 629-630 ◽  
pp. 162-167 ◽  
Author(s):  
Hong Jian Du ◽  
Sze Dai Pang
Keyword(s):  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Cement Composites ◽  
Chloride Diffusion Coefficient ◽  
Barrier Effect ◽  
Graphene Nanoplatelet ◽  
Chloride Migration ◽  
Corrosion Of Steel ◽  
And Diffusion

Cement composites are vulnerable to harsh environments in which the chloride ions can ingress into concrete and thus cause corrosion of steel. In this study, the barrier effect of adding 2-D nanoparticles on the transport properties of cement-based materials was investigated. Graphene nanoplatelet (GNP), which comprises of a few layers of graphene stacked together, is chosen as a candidate in this study due to its impermeability and also its electrical conductivity which can be exploited for self-sensing functionality. Due to the large aspect ratio of the GNP, it is expected that the dispersion of these 2-D nanobarriers can contribute to the reduced permeability and diffusion of harmful agents. Experiments were carried out on cement mortar with 0%, 2.5%, 5.0% and 7.5% of GNP by weight of cement. The water penetration depth, chloride diffusion coefficient and chloride migration coefficient were reduced by 64%, 70% and 31% respectively with the addition of as little as 2.5% of GNP. This reduction can be attributed to the barrier effect of GNP which increases the tortuosity against water and chloride ions penetration, and also the refinement of the capillary pores which was revealed from the MIP tests. At GNP content exceeding 5%, the nanoparticles agglomerate, causing weak pockets which compromises the benefits of adding GNP to impede the ingress of fluids.

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.

scholarly journals Experimental Study on Chloride Ion Diffusion in Concrete under Uniaxial and Biaxial Sustained Stress

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5717
Author(s):  
Xiaokang Cheng ◽  
Jianxin Peng ◽  
C.S. Cai ◽  
Jianren Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Compressive Stress ◽  
Stress Level ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Chloride Ion Diffusion

The existence of axial and lateral compressive stress affect the diffusion of chloride ions in concrete will lead to the performance degradation of concrete structure. This paper experimentally studied the chloride diffusivity properties of uniaxial and biaxial sustained compressive stress under one-dimensional chloride solution erosion. The influence of different sustained compressive stress states on chloride ion diffusivity is evaluated by testing chloride concentration in concrete. The experiment results show that the existence of sustained compressive stress does not always inhibit the diffusion of chloride ions in concrete, and the numerical value of sustained compressive stress level can affect the diffusion law of chloride ions in concrete. It is found that the chloride concentration decreases most when the lateral compressive stress level is close to 0.15 times the compressive strength of concrete. In addition, the sustained compressive stress has a significant effect on chloride ion diffusion of concrete with high water/cement ratio. Then, the chloride diffusion coefficient model under uniaxial and biaxial sustained compressive stress is established based on the apparent chloride diffusion coefficient. Finally, the results demonstrate that the chloride diffusion coefficient model is reasonable and feasible by comparing the experimental data in the opening literature with the calculated values from the developed model.

scholarly journals RC Structures Strengthened by an Iron-Based Shape Memory Alloy Embedded in a Shotcrete Layer—Nonlinear Finite Element Modeling

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5504
Author(s):  
Neda Dolatabadi ◽  
Moslem Shahverdi ◽  
Mehdi Ghassemieh ◽  
Masoud Motavalli
Keyword(s):  
Finite Element ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Passive Control ◽  
Load Capacity ◽  
Finite Element Models ◽  
Rc Structures ◽  
Displacement Response ◽  
Iron Based ◽  
Load Displacement

Shape memory alloys (SMAs) have been widely used in civil engineering applications including active and passive control of structures, sensors and actuators and strengthening of reinforced concrete (RC) structures owing to unique features such as the shape memory effect and pseudo-elasticity. Iron-based shape memory alloys (Fe-SMAs) have become popular in recent years. Use of iron-based SMAs for strengthening RC structures has received attention in the recent decade due to the advantages it presents, that is, no ducts or anchor heads are required, friction losses do not occur and no space is needed for a hydraulic device to exert force. Accordingly, Fe-SMAs embedded in a shotcrete layer have been used for pre-stressing RC beams at Empa. The aim of this study is to present an approach to model and analyze the behavior of RC members strengthened and pre-stressed with Fe-SMA rebars embedded in a shotcrete layer. The lack of research on developing finite element models for studying the behavior of concrete structures strengthened by iron-based shape memory alloys is addressed. Three-dimensional finite element models were developed in the commercial finite element code ABAQUS, using the concrete damaged plasticity model to predict the studied beams’ load–displacement response. The results of the finite element analyses show a considerably good agreement with the experimental data in terms of the beams’ cracking load and ultimate load capacity. The effects of different strengthening parameters, including SMA rebar diameter, steel rebar diameter and pre-stressing force level on the beam behavior, were investigated based on the verified finite element models. The results were compared. The load-displacement response of an 18-m concrete girder strengthened and pre-stressed with iron-based SMA bars was examined by the developed finite element model as a case study.

scholarly journals Experimental Investigation on Chloride Diffusion Coefficient of Self-compacting Concrete in the Oman Sea

2020 ◽  
Author(s):  
Naser Nosratzehi ◽  
Mahmoud Miri
Keyword(s):  
Diffusion Coefficient ◽  
Environmental Conditions ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Atmospheric Conditions ◽  
Self Compacting Concrete ◽  
Normal Concrete ◽  
Oman Sea

Chloride ion penetration is an important parameter influencing the service life of a concrete structure, especially in aggressive environments. Severe chloride-induced corrosion of reinforced concretes has been reported in the southern part of Iran in the region of Oman Sea. In this paper, the effect of different environmental conditions of the Oman Sea on chloride penetration and mechanical properties of self-compacting concrete (SCC) and normal concrete (NC) is investigated. For this purpose, a number of prismatic specimens were exposed to various environmental conditions such as tide, submersion and atmospheric conditions. Surface chloride concentration and diffusion coefficient of SCC in these zones were calculated based on Fick’s second law, at 28, 90 and 150 days and compared with NC. Based on the values obtained in this study, relationships are proposed for concrete permeability and surface chloride of self-compacting concrete (SCC) at different ages in different aggressive environments. By determining the corrosion time based on these relations, it is observed that for a given water-to-cement ratio, the self-compacting concrete (SCC) has higher durability compared to normal concrete (NC).

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.

scholarly journals Applicability of Diffuse Ultrasound to Evaluation of the Water Permeability and Chloride Ion Penetrability of Cracked Concrete

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4156 ◽  
Author(s):  
Eunjong Ahn ◽  
Seongwoo Gwon ◽  
Hyunjun Kim ◽  
Chanyoung Kim ◽  
Sung-Han Sim ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Water Flow ◽  
Flow Rate ◽  
Water Permeability ◽  
Water Flow Rate ◽  
Chloride Ion ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cracked Concrete ◽  
Diffuse Ultrasound

This study aims to explore the applicability of diffuse ultrasound to the evaluation of water permeability and chloride ion penetrability of cracked concrete. Lab-scale experiments were conducted on disk-shaped concrete specimens, each having a different width of a penetrating crack that was generated by splitting tension along the centerline. The average crack width of each specimen was determined using an image binarization technique. The diffuse ultrasound test employed signals in the frequency range of 200 to 440 kHz. The water flow rate was measured using a constant water-head permeability method, and the chloride diffusion coefficient was determined using a modified steady-state migration method. Then, the effects of crack width on the diffusion characteristics of ultrasound (i.e., diffusivity, dissipation), water flow rate, and chloride diffusion coefficient are investigated. The correlations between the water flow rate and diffuse ultrasound parameters, and between the chloride diffusion coefficient and diffuse ultrasound parameters, are examined. The results suggest that diffuse ultrasound is a promising method for assessing the water permeability and chloride ion penetrability of cracked concrete.

Distribution of Chloride Concentration in Modeled Recycled Concrete Simulated by Finite Element Method

2011 ◽  
Vol 261-263 ◽  
pp. 147-150
Author(s):  
Jing Wei Ying ◽  
He Gong Chen
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Diffusion Process ◽  
Homogeneous Medium ◽  
Chloride Concentration ◽  
Smooth Curve ◽  
Recycled Concrete ◽  
Recycled Aggregates ◽  
Chloride Diffusion ◽  
Element Method

Proposed is a simple analytic model that can simulate the chloride diffusion distribution in a modeled recycled aggregates concrete (RAC). In this paper, on the one hand, the RAC is divided into three phases such as normal aggregates, new mortar and old attached mortar; on the other hand, a single aggregates RAC model was built, finite element method (FEM) is used to simulate chloride diffusion process based on the parameters of diffusivities summarized or derived from other literatures. It is found that the chloride concentration distribution in the RAC shows a band-like profile instead of a smooth curve for a homogeneous medium by ten years diffusion, with the bandwidth undulating and narrowing as the diffusion depth increases. The concentration of chloride distribution can be indicated by the different colors and, therefore, the proposed model allows more accurate realization of diffusion process.

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