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.

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.

Durability Design of Marine Concrete Structure Considering the Influence of Load

2015 ◽  
Vol 744-746 ◽  
pp. 59-64 ◽  
Author(s):  
Jian Bo Xiong ◽  
Chun Lin Deng
Keyword(s):  
Diffusion Coefficient ◽  
Tensile Stress ◽  
Concrete Structure ◽  
High Performance Concrete ◽  
Chloride Ion ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Exponential Relationship ◽  
Chloride Ion Diffusion

In this paper, based on accelerated testing indoors, under the action of bending tensile stress on a marine high-performance concrete chloride ion diffusion coefficient, the results show that: Subjected to bend under the action of tensile stress and do not withstand the test piece chloride diffusion coefficient increases with increasing stress levels, different tensile stress and does not bear the stress of the concrete chloride ion diffusion coefficient ratio (Dη/D0) exponential relationship with the stress level (η). In addition, addition, for a domestic Bridge, preliminary design to determine typical parameters of components and their environment is proposed to consider the durability of concrete structure load control index calculation method, to establish a "design life - chloride ion diffusion coefficient controlled targets" the correspondence between, for similar projects designed to provide a reference durability.

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.

Experimental Study on Mix Design of Chloride Resistant Cementitious Spacers

2014 ◽  
Vol 629-630 ◽  
pp. 351-357
Author(s):  
Chen Huang ◽  
Wen Ying Guo ◽  
Yi Bo Yang ◽  
Hui Zhao ◽  
Zhen Jie Li ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Design Method ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Mix Design ◽  
Easy Access ◽  
Ion Diffusion ◽  
Electric Flux ◽  
Chloride Environment ◽  
Chloride Ion Diffusion

Chloride resistant HPC and protective cover are two basic measurements to improve the durability of concrete in chloride environment. Though it provides crucial cover for concrete to resist chloride ions, spacer has limited chloride resistant ability, which is overlooked by past researchers. Cementitious spacers are easy access for chloride ions to penetrate into concrete resulting in reduction of structural durability. To improve cementitious spacers’ performance, a systematic study was conducted. Test results showed that there was major difference between mortar and concrete in terms of chloride coulomb electric flux but minor difference in terms of chloride ion diffusion coefficient, which implied using chloride ion diffusion coefficient as spacer’s durability indicator was preferable; parameters of mix design had a similar influence on mortar and concrete and, with the same mixing parameters, the strength and chloride resistant ability of mortar were weaker than concrete’s; it was feasible to develop the mix design of chloride resistant cementitious spacers based on concrete’s design method with certain adjustments, such as using stricter mix proportion, adding small-size coarse aggregate, lowering water-binder ratio and optimizing the binder proportion, to achieve higher strength and durability.

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 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%.

Testing for the Influence of the Degree of Water Saturation of Concrete upon Chloride Diffusivity

2013 ◽  
Vol 405-408 ◽  
pp. 2639-2643
Author(s):  
Van Tuan Le ◽  
Yong Lai Zheng ◽  
Shu Xin Deng
Keyword(s):  
Diffusion Coefficient ◽  
Water Saturation ◽  
Chloride Ion ◽  
Test Method ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Chloride Diffusivity ◽  
Water Saturated ◽  
The Impact

In order to estimate the impact of the degree of water saturation of concrete to chloride ion diffusion coefficient, the experimental setup allows to measure chloride diffusion coefficient through nonsaturated concrete specimens with controlled degree of water saturated. The different degrees of water saturation of concrete specimens were obtained, by using saturated solutions of NaCl and KCl controlling the relative humidity, then applied Rapid Cloride Permeability Test method to measure the cloride diffusion coefficient. The test results show that chloride diffusion coefficient depends strongly on the degree of water saturation of concrete. Beside, this relationship shows the non-linear relationship, in which, chloride diffusion coefficient reachs the maximum value in fully saturated concrete specimens.

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 Influence of Pore Size and Fatigue Loading on NaCl Transport Properties in C-S-H Nanopores: A Molecular Dynamics Simulation

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 700 ◽  
Author(s):  
Qingyu Cao ◽  
Yidong Xu ◽  
Jianke Fang ◽  
Yufeng Song ◽  
Yao Wang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Transport Properties ◽  
Diffusion Rate ◽  
Chloride Ion ◽  
Fatigue Loading ◽  
Chloride Ions ◽  
Water Molecules ◽  
Ion Diffusion ◽  
Chloride Ion Diffusion

The transport properties of chloride ions in cement-based materials are one of the major deterioration mechanisms for reinforced concrete (RC) structures. This paper investigates the influence of pore size and fatigue loading on the transport properties of NaCl in C-S-H nanopores using molecular dynamics (MD) simulations. Molecular models of C-S-H, NaCl solution, and C-S-H nanopores with different pore diameters are established on a microscopic scale. The distribution of the chloride ion diffusion rate and the diffusion coefficient of each particle are obtained by statistically calculating the variation of atomic displacement with time. The results indicate that the chloride ion diffusion rate perpendicular to C-S-H nanopores under fatigue loading is 4 times faster than that without fatigue loading. Moreover, the diffusion coefficient of water molecules and chloride ions in C-S-H nanopores increases under fatigue loading compared with those without fatigue loading. The diffusion coefficient of water molecules in C-S-H nanopores with a pore size of 3 nm obtained from the MD simulation is 1.794 × 10−9 m2/s, which is slightly lower than that obtained from the experiment.

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.

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