Research on Chloride Diffusion Model in Pre-Stressed Concrete with Sulfate Attack

2012 ◽  
Vol 166-169 ◽  
pp. 1935-1940
Author(s):  
Rong Gui Liu ◽  
Jing Li ◽  
Huan Li
Keyword(s):  
Diffusion Coefficient ◽  
Binding Capacity ◽  
Chloride Ion ◽  
Sulfate Attack ◽  
Ion Concentration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Influence Of Water ◽  
Binder Ratio ◽  
Chloride Environment

Chloride diffusion coefficient is significant to the durability of pre-stressed concrete in chloride environment. The factors which influence chloride diffusion coefficient in pre-stressed concrete structures eroded by chloride ion is of great importance, including porosity, chloride ion binding capacity and the stress of pre-stressed concrete etc. Based on the Fick’s second law and existing models, the model of chloride ion diffusion in pre-stressed concrete with sulfate attack is established. It is analyzed that the influence of water-binder ratio and sulfate ion concentration and erosion time on concentration distribution of chloride ion in concrete. Compared to test data and project examples, it is confirmed that the model is useful.

Numerical Stimulation Method of Chloride Concentration in the Concrete Structure Exposed to Chloride Aggressive Environment

2012 ◽  
Vol 193-194 ◽  
pp. 466-471
Author(s):  
Ying Huang ◽  
Jun Wei ◽  
Rong Zhen Dong ◽  
Hui Huang Yan
Keyword(s):  
Thermal Analysis ◽  
Diffusion Coefficient ◽  
Diffusion Equation ◽  
Chloride Concentration ◽  
Chloride Ion ◽  
Ion Concentration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Finite Element Software ◽  
Numerical Stimulation

In this paper, based on the similarity between chloride diffusion equation in concrete and heat conduction equation the thermal analysis module of the ANSYS finite element software was used to carry out the numerical simulation for chloride ion diffusion process in concrete. And the numerical results were compared with the analytical solutions of chloride diffusion equation, which showed that the method is effective for the chloride diffusion analysis. Time-dependence of chloride diffusion coefficient in concrete was considered by amending the chloride diffusion coefficient with various parameters. Finally it is a feasible method that the chloride ion concentration in concrete structures was calculated by thermal analysis module of the ANSYS.

Experimental Study and Numerical Analysis on Chloride Diffusion Coefficient of Concrete with Various Water-Cement Ratios

2017 ◽  
Vol 726 ◽  
pp. 547-552
Author(s):  
Zheng Ren ◽  
Lian Zhen Xiao ◽  
Wen Chong Shi
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Chloride Ion Diffusion

A rapid chloride ion diffusion coefficient measurement (RCM) was used in this study. The influence of water-cement ratios of 0.30, 0.35 and 0.40 at various ages (3, 7, 14, 28 and 56 days) on chloride ion diffusion coefficient of the concretes and pastes was studied and analyzed. The results show that, with the increase of curing ages, the chloride ion diffusion coefficient of different water-cement ratio of each specimen is decreased. In the early age, the chloride ion diffusion coefficient of the paste with the water-cement ratio of 0.40 is 2~3 times of the paste with water-cement ratio of 0.30 and 0.35, and with the increase of curing age, this difference is gradually decreased. Additionally, the chloride ion diffusion coefficient of the cement paste is 1~2 times of the concrete with same water-cement ratio at different ages. Based on the actual experiment boundary conditions, the process of chloride ions diffusion and permeability was simulated by COMSOL software, and the simulation result was analyzed to predict the permeability of concrete.

Diffusion study of chloride and binding of water in concrete pore by molecular dynamics simulation using LAMMPS

2021 ◽  
Vol 12 (3) ◽  
pp. 88
Author(s):  
Md. Shafiqul Islam ◽  
Sayem Ahmeed ◽  
Sumon Kumar Ghosh
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
System Size ◽  
Dynamics Simulation ◽  
Chloride Diffusion ◽  
Water Molecules ◽  
Chloride Diffusion Coefficient ◽  
Average Value ◽  
Temperature And Pressure ◽  
Different Characteristics

As for the communication between concrete and the particles, the surface shows Cl− shock and Na adsorption. With expanded particle focus, the solid adsorption capacity for Cl− is upgraded as a result of a detailed overview of the dynamic molecular simulation studies examining the chloride diffusion coefficient. Different characteristics of the diffusion process, including molecular models, system-size effects, temperature, and pressure conditions, and the type of protection, are discussed. This paper focus on Molecular Dynamic Simulation to determine the diffusion coefficient of chloride ion and water molecules in concrete. The diffusion coefficient for NaCl salt obtained 6.60178x10-10m2/s and the diffusion coefficient for CaCl2 salt obtained 7.29305x10-10m2/s. So, the average chloride diffusion coefficient 6.9475x10-10m2/s. Diffusion coefficient obtained from graph 5.562x10-10m2/s. Diffusion coefficients for water molecules for NaCl solution are 6.125x10-10m2/s, 6.85x10-10m2/s, 1.044x10-10m2/s, 8.525x10-10m2/s, 6.25x10-10m2/s. diffusion coefficient of water molecules in CaCl2 solution are 4.5x10-10m2/s, 6.725x10-10m2/s, 1.254x10-10m2/s, 7.725x10-10m2/s, 1.3x10-10m2/s. Average value obtained for water molecule diffusion are 4.545x10-10m2/s, 7.4062x10-10m2/s and 1.149x10-10m2/s. This diffusion of chloride effects the binding of water in concrete pore.

scholarly journals Effect of Fly Ash as Cement Replacement on Chloride Diffusion, Chloride Binding Capacity, and Micro-Properties of Concrete in a Water Soaking Environment

2020 ◽  
Vol 10 (18) ◽  
pp. 6271 ◽  
Author(s):  
Jun Liu ◽  
Jiaying Liu ◽  
Zhenyu Huang ◽  
Jihua Zhu ◽  
Wei Liu ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Binding Capacity ◽  
Chloride Ion ◽  
Chloride Content ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Binding ◽  
Test Results ◽  
New Equation

This paper experimentally studies the effects of fly ash on the diffusion, bonding, and micro-properties of chloride penetration in concrete in a water soaking environment based on the natural diffusion law. Different fly ash replacement ratio of cement in normal concrete was investigated. The effect of fly ash on chloride transportation, diffusion, coefficient, free chloride content, and binding chloride content were quantified, and the concrete porosity and microstructure were also reported through mercury intrusion perimetry and scanning electron microscopy, respectively. It was concluded from the test results that fly ash particles and hydration products (filling and pozzolanic effects) led to the densification of microstructures in concrete. The addition of fly ash greatly reduced the deposition of chloride ions. The chloride ion diffusion coefficient considerably decreased with increasing fly ash replacement, and fly ash benefits the binding of chloride in concrete. Additionally, a new equation is proposed to predict chloride binding capacity based on the test results.

Design and Impermeability of High Durability Reinforced Concrete Segment

2012 ◽  
Vol 174-177 ◽  
pp. 1199-1203
Author(s):  
Xin'gang Wang ◽  
Fang Bin Chen ◽  
Xu Na Ye ◽  
Wei Qin Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Reinforced Concrete ◽  
Water Pressure ◽  
Chloride Ion ◽  
Concrete Cover ◽  
Chloride Diffusion ◽  
Shield Tunnel ◽  
Main Body ◽  
Chloride Diffusion Coefficient ◽  
High Durability

Reinforced concrete segment is the main body of structure in shield tunnel, and its durability has an important effect on shield tunnel. The durability of High Durability Reinforced Concrete Segment (abbr. HDRC Segment) was investigated by impermeability of single segment and chloride diffusion coefficient of core-drilling. HDRC Segment had high compact cover, concrete cover and high strength structural-layer. Permeable height of HDRC Segment was approximately 0.5 mm when Keeping 4 hours in the constant water pressure of 0.8 MPa, and chloride diffusion coefficient of HDRC Segment was only 4.9×10－13m2/s by NEL method. As for Water impermeability and chloride ion penetration resistance, HDRC Segment is far superior to those of conventional Reinforced Concrete Segment (abbr. conventional RC Segment). It is advantageous to increase durability of HDRC Segment and service life of tunnel engineering.

Influence of Stone Dust in Manufactured Sand on Resisting Chloride Penetration in Marine Concretes

2012 ◽  
Vol 174-177 ◽  
pp. 1419-1423
Author(s):  
Jian Bo Xiong ◽  
Peng Ping Li ◽  
Sheng Nian Wang
Keyword(s):  
Diffusion Coefficient ◽  
Pore Structure ◽  
Binding Capacity ◽  
Chloride Penetration ◽  
Dust Content ◽  
Chloride Diffusion ◽  
Fine Aggregate ◽  
Chloride Diffusion Coefficient ◽  
Manufactured Sand ◽  
Stone Dust

In China, manufactured sand has been widely used as fine aggregate in concrete. Therefore, it is necessary to investigate the effect of manufactured sand on durability of concrete. This research studies the influence of stone dust content in manufactured sand on resisting chloride penetration in marine concrete by strength and other physical mechanical tests, XRD, TGA and pore structure analysis. Test results have shown that the chloride diffusion coefficient increased with increasing the stone dust content in manufactured sand when the stone dust content increasing from 3% to 13%. The stone dust in fine aggregate was participated in hydration procedure of cementitious, which will promote the hydration degree of cementitious and increase the chloride binding capacity of hydration product. The influence of stone dust in fine aggregate on chloride diffusion coefficient were the combined effects of concrete pore structure and cementitious hydration products, and the porosity and pore size distribution were the main factors that influence the changes of diffusion coefficient.

Effect of Sulfate Ion to Chloride Ion Transmission in Concrete under Flexural Load

2011 ◽  
Vol 90-93 ◽  
pp. 2798-2802
Author(s):  
Zu Quan Jin ◽  
Qi Chang Zhuang ◽  
Jie Lin
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
Chloride Diffusion ◽  
Main Role ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Sulfate Ion ◽  
Load Rate ◽  
Negative Effect ◽  
Ion Transmission

Chloride ion ingression into concrete under flexural load is investigated in the paper. Concrete specimens have been stored in 3.5%NaCl solution or 3.5%NaCl + 5%Na2SO4 solution for 210 days. The effect of flexural load and sulfate ion to chloride ion transmission is studied. The experimental results show that sulfate ion reduces chloride ion transmission in concrete. But when concrete under flexural load, Sulfate ion has plus and minus effect on chloride ion ingression into concrete. When the flexural load rate is low, sulfate ion reduces chloride ion transmission. But the flexural load is high, the negative effect of sulfate corrosion plays a main role. When concrete exposed to 3.5%NaCl+5%Na2SO4 solution, chloride ion diffusion coefficient of concrete in tensile zone increases with flexural load. And in compressive zone, the chloride diffusion coefficient decreases first and then raises with increasing flexural load.

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 Evaluation of Chloride Resistance of Early-Strength Concrete Using Blended Binder and Polycarboxylate-Based Chemical Admixture

2020 ◽  
Vol 10 (8) ◽  
pp. 2972 ◽  
Author(s):  
Taegyu Lee ◽  
Jaehyun Lee
Keyword(s):  
Compressive Strength ◽  
Diffusion Coefficient ◽  
Portland Cement ◽  
Chloride Ion ◽  
Strength Criterion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Characteristic Strength ◽  
Early Strength

The mixing proportions of concrete were examined with regard to the durability performance and early strength in coastal areas. Research was conducted to improve the C24 mix (characteristic strength of 24 MPa). C35 concrete (characteristic strength of 35 MPa) was selected as a comparison group, as it exhibits the minimum proposed strength criterion for concrete in the marine environment. To secure the early strength of the C24 concrete, 50% of the total ordinary Portland cement (OPC) binder was replaced with early Portland cement (EPC); and to provide durability, 20% was substituted with ground granulated blast-furnace slag (GGBS). In addition, a polycarboxylate (PC)-based superplasticizer was used to reduce the unit water content. The compressive strength, chloride ion diffusion coefficient, chloride penetration depth, and pore structure were evaluated. After one day, the compressive strength improved by 40% when using EPC and GGBS, and an average increase of 20% was observed over 91 days. EPC and GGBS also reduced the overall porosity, which may increase the watertightness of concrete. The salt resistance performance was improved because the rapid early development of strength increased the watertightness of the surface and immobilization of chloride ions, decreasing the chloride diffusion coefficient by 50%.

scholarly journals Chloride Resistance of Portland Cement-Based Mortar Incorporating High Aluminate Cement and Calcium Carbonate

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 359 ◽  
Author(s):  
Yunsu Lee ◽  
Seungmin Lim ◽  
Hanseung Lee
Keyword(s):  
Diffusion Coefficient ◽  
Calcium Carbonate ◽  
Pore Volume ◽  
Binding Capacity ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Chloride Binding ◽  
Chloride Resistance ◽  
Aluminate Cement ◽  
Capillary Pore

Whether chloride resistance is highly influenced by chloride binding capacity remains unknown. In this study, the chloride resistance of Portland cement-based mortar incorporating aluminate cement and calcium carbonate was investigated considering the chloride binding capacity, pore structures and chloride diffusion coefficient from non-steady state chloride migration and natural chloride diffusion. The cement hydrates were investigated using X-ray diffraction and thermogravimetric analysis. The chloride binding capacity was evaluated based on the chloride adsorption from the solutions using the adsorption isotherm. The aluminate cement, as an available alumina source, can stimulate the formulation of layered double hydroxides, which in turn can increase the chloride binding capacity. The results of mercury intrusion porosimetry show that non-substituted (control) and substituted (only aluminate cement) specimens have capillary pore volume 8.9 vol % and 8.2 vol %, respectively. However, the specimen substituted with aluminate cement and calcium carbonate shows a higher capillary volume (12.9 vol %), which correlates with the chloride diffusion coefficient. Although the specimen substituted with calcium carbonate has a higher chloride binding capacity than the control, it does not necessarily affect the decrease in the chloride diffusion coefficient. The capillary pore volume can affect not only the chloride diffusion but also the chloride adsorption.

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