Coupling Effects of Chloride Penetrating and Corrosion Damage Evolving Process in Concrete under Marine Environment

2016 ◽  
Vol 846 ◽  
pp. 245-250
Author(s):  
Qin Zhang ◽  
Li Guo ◽  
Xiao Ming Guo
Keyword(s):  
Marine Environment ◽  
Concrete Structure ◽  
Chloride Concentration ◽  
Corrosion Damage ◽  
Internal Variable ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Damage Degree ◽  
User Subroutine ◽  
Chloride Ions Diffusion

Chloride penetration could lead to the rebar corrosion and cause the durability problem in concrete structure under marine environment. It is a coupling process between chloride penetrating and corrosion damage evolving in concrete. This paper proposed an analysis method to deal with this coupling problem. The corrosion damage degree was considered as an internal variable in coefficients of chloride diffusion. Additionally, the interfacial boundary displacement values varied with chloride concentration and service time of concrete structure. This iterative computing algorithm was tackled as user subroutine packaged into software ABAQUS. The numerical examples were given to confirm the reliability of the developed model. The results show that corrosion expanded damage accelerates chloride ions diffusion and vice versa.

Sensitivity Analysis of Durability Parameters of Concrete Structures Corroded by Chloride Ions

2012 ◽  
Vol 594-597 ◽  
pp. 999-1004
Author(s):  
Li Zeng ◽  
Yuan Cheng Guo ◽  
Zhuo Zhao
Keyword(s):  
Concrete Structure ◽  
Diffusion Mechanism ◽  
Limit State ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
State Function ◽  
Chloride Diffusion Coefficient ◽  
Structural Durability ◽  
Influencing Parameters

For the pre-stressed concrete structure under marine environment，the stochastic characters of structure and environment such as concrete cover depth, initial chloride ions concentration, chloride diffusion coefficient in concrete, critical chloride ions concentration and structural surface chloride ions concentration affect the structural durability in designed service life greatly. Based on the diffusion mechanism of chloride ions, considering the durability failure character of pre-stressed concrete structure, the limit state function of durability failure is established, the sensitivity of durability influencing parameters is analyzed, and the Monte Carlo simulation is carried out based on the stochastic characters of influencing parameters, which will provide method and foundation for the structural durability design, construction and quality control of similar project.

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.

Membrane Potentials in the Central Nervous System of a Phytophagous Insect (Carausius Morosus)

1967 ◽  
Vol 46 (3) ◽  
pp. 413-421
Author(s):  
J. E. TREHERNE ◽  
S. H. P. MADDRELL
Keyword(s):  
Action Potentials ◽  
Fat Body ◽  
Chloride Concentration ◽  
Sodium Concentration ◽  
Stick Insect ◽  
Mean Value ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Glass Capillary ◽  
Positive Potential

1. The nerve cord of the stick insect is surrounded by a fat-body sheath. This sheath encloses an extraneural space and thus interposes an additional fluid compartment between the neural lamella and the haemolymph. The axons in the thoracic connectives were found to be relatively small, the largest ones averaging 7--II µ in diameter. 2. The apparent resting potentials of axons, impaled with glass capillary microelectrodes, were found to be relatively small, averaging only 25.1 mV., with an overshoot of 59.3 mV. in action potentials in intact preparations. In the absence of the neural fat-body sheath the resting potentials were increased to a mean value of 40.3 mV., there being no significant alteration in the total amplitude of the action potentials. This effect appears to result from the interpolation of a positive potential of some 15-20 mV. between the indifferent and recording electrodes. 3. The positive potential was abolished, in intact preparations, when the nerve cords were bathed with solutions of elevated chloride concentration. Positive potentials were also obtained when gradients of chloride ions were maintained across the isolated fatbody sheath. It is suggested that the positive potentials may result from a chloride diffusion potential across the neural fat-body sheath. 4. The results are discussed in relation to the ability of the axons of this species to function in ganglia and connectives bathed with solutions of low sodium concentration.

Service Life Checking Calculation of Marine Reinforced Concrete Structures Based on Monte Carlo Method

2013 ◽  
Vol 788 ◽  
pp. 663-669
Author(s):  
Gui Hong Dong ◽  
Zhi Hong Fan ◽  
Jian Bo Xiong
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Service Life ◽  
Marine Environment ◽  
Concrete Structures ◽  
Chloride Concentration ◽  
Chloride Diffusion ◽  
Distribution Model ◽  
Chloride Diffusion Coefficient ◽  
Design Life

Checking some apparent chloride diffusion coefficient of concrete in the marine environment meets the requirements of design life based on Monte Carlo method. Through the project investigations, laboratory test data, statistical analysis and to determine random distribution model of the critical chloride concentration, the surface chloride concentration ,using computer program simulation 5000 random groups critical chloride concentration, surface chloride concentration into the life value calculation model, And obtain the derived distribution of the concrete structures service life, in order to determine Compliance with the design life of concrete structures. For the concrete durability design and service life checking provide the effective analysis under the marine environment.

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.

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.

Probabilistic Design for Concrete Durability in Marine Environment

2013 ◽  
Vol 431 ◽  
pp. 53-56
Author(s):  
Qing Lian Shu ◽  
Lu Ling Yang ◽  
Rui Gao ◽  
Ling Qiang Yang
Keyword(s):  
Chemical Composition ◽  
Marine Environment ◽  
Random Distribution ◽  
Probabilistic Method ◽  
Chloride Concentration ◽  
Chloride Diffusion ◽  
Model Parameters ◽  
Concrete Durability ◽  
Probabilistic Design ◽  
Saturated Medium

A probabilistic method to durability is proposed for the design of reinforced cover of a concrete immersed in marine environment. It uses a non-linear chloride diffusion model for a saturated medium. Parameter variability is estimated and used by the probabilistic method to assess the probability of reaching a critical chloride concentration near the reinforcement for a given service life. Based on the concrete formulation and the cement chemical composition, the model parameters are evaluated with their associated random distribution.

Numerical Simulation on Chloride Ions Diffusion in Concrete

2011 ◽  
Vol 261-263 ◽  
pp. 348-351 ◽  
Author(s):  
Qing Wang ◽  
Gang Xu ◽  
Jun Wei
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Concentration Distribution ◽  
Chloride Concentration ◽  
Simulation Method ◽  
Chloride Ions ◽  
Test Results ◽  
Exposure Test ◽  
Modified Model ◽  
Chloride Ions Diffusion

Allowing for the analogy between ions diffusion and heat transfer, the numerical simulation on chloride ions diffusion in concrete can be realized following the thermal analysis module in the large general FEA software ANSYS, by reasonable equivalent of parameters. It is based on the modified model for Fick’s second diffusion law, taking the factors of temperature, humidity and time etc. into account. Hereby, the numerical simulation method is established for predicting the chloride concentration distribution with time in concrete, testified by the coastal exposure test. The test results confirm the efficiency and feasibility of the method.

Research on Life Prediction for One Gravity Piered Wharf Based on the Regulated Reliability Index

2012 ◽  
Vol 256-259 ◽  
pp. 1101-1111
Author(s):  
Wei Hua Li ◽  
Xiang Zhuang Gao ◽  
Cong Tao Sun ◽  
Hai Bing Zheng
Keyword(s):  
Service Life ◽  
Concrete Structure ◽  
Chloride Concentration ◽  
Concrete Cover ◽  
Chloride Diffusion ◽  
Reinforcement Corrosion ◽  
Sea Sand ◽  
Long Term Behavior ◽  
Very High

The long-term behavior of concrete structure shows that the main cause of deterioration is reinforcement corrosion. One of the most aggressive exposure conditions for concrete is marine environment. What is worse, the structure mixed with sea sand. Under these conditions, chloride-induced reinforcement corrosion rate could be very high, often leading to reduction of the service life. This paper investigates long-term corrosive beams in the above-mentioned cases. Chloride distribution is analyzed. From Fick’s second law, the parameters for chloride diffusion can be obtained. Then, the service life of the concrete structure is predicted via empolying probability analysis. The characteristics of randomness (concrete cover, diffusion coefficient, surface chloride concentration and so on) have been taken into consideration.

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