scholarly journals Prediction of Time-Dependent Chloride Diffusion Coefficients for Slag-Blended Concrete

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ki-Bong Park ◽  
Han-Seung Lee ◽  
Xiao-Yong Wang
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Blended Cement ◽  
Numerical Procedure ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Capillary Porosity ◽  
Key Factor ◽  
Hydration Model

The chloride diffusion coefficient is considered to be a key factor for evaluating the service life of ground-granulated blast-furnace slag (GGBS) blended concrete. The chloride diffusion coefficient relates to both the concrete mixing proportions and curing ages. Due to the continuous hydration of the binders, the capillary porosity of the concrete decreases and the chloride diffusion coefficient also decreases over time. To date, the dependence of chloride diffusivity on the binder hydration and curing ages of slag-blended concrete has not been considered in detail. To fill this gap, this study presents a numerical procedure to predict time-dependent chloride diffusion coefficients for slag-blended concrete. First, by using a blended cement hydration model, the degree of the binder reaction for hardening concrete can be calculated. The effects of the water to binder ratios and slag replacement ratios on the degree of the binder reaction are considered. Second, by using the degree of the binder reaction, the capillary porosity of the binder paste at different curing ages can be determined. Third, by using the capillary porosity and aggregate volume, the chloride diffusion coefficients of concrete can be calculated. The proposed numerical procedure has been verified using the experimental results of concrete with different water to binder ratios, slag replacement ratios, and curing ages.

On the Time Dependency of the Chloride Diffusion in High Performance Concrete

2013 ◽  
Vol 721 ◽  
pp. 148-152
Author(s):  
Zheng Chen ◽  
Xi Bin Zhao ◽  
Yan Hua Yuan ◽  
Zhong Hua Wang ◽  
Lu Feng Yang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
High Performance ◽  
High Performance Concrete ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Time Dependency ◽  
Long Period ◽  
Age Factor ◽  
Astm C1202

The chloride diffusion coefficient of concrete is time dependent. The high performance concrete (HPC) was prepared and the specimens were tested by ASTM C1202 and the durability of HPC in long period is analyzed with the time dependency of diffusion in this paper. The results show that the chloride diffusion coefficients of the HPC with only fly ash are large than those of the HPC with multi-admixtures, but the attenuation of the chloride diffusion coefficients of the formers are faster than the latters. The analysis results show that the chloride concentrations in concrete is over estimated when time-dependence of chloride diffusion is not considered, and the durability of concrete in long period is determined by both chloride diffusion coefficient and age factor.

Study on Durability of Concrete with Machine-Made Sand Part I: Time-Dependent Chloride Penetration

2013 ◽  
Vol 438-439 ◽  
pp. 3-9
Author(s):  
Chun Jie Liu ◽  
Yang Yang Xu ◽  
Xiao Yan Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Concrete Strength ◽  
Forecast Model ◽  
Chloride Penetration ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Curing Time ◽  
Ordinary Concrete ◽  
Durability Of Concrete

As part of the studies on the durability of concrete with machine-made sand, this paper introduces the test results and the forecast model of time-dependent chloride penetration of this kind of concrete. Three strength grades of concrete C30, C40 and C50, and the contents of stone powder in machine-made sand of 5%, 9% and 13% in mass were considered in the mix proportion of concrete with machine-made sand. The ordinary concrete with natural river sand in the same strength grade was tested at the same time for comparison. The test was conducted for 360 days, the results showed that the effect of the content of stone powder on the chloride penetration of concrete was obvious at early curing time of 7 days, and tended to be lower with the increase of curing time. When the curing time was longer than 90 days, this effect could be neglected, and the resistance to chloride penetration of concrete with machine-made sand was almost equal to or larger than that of ordinary concrete. The decrement of chloride diffusion coefficient varied from sharp to gentle with the curing time, the resistance of concrete to chloride penetration increased with the increase of concrete strength. Meanwhile, to facilitate the calculation in practice, the forecast model of chloride diffusion coefficient of concrete is proposed.

Concentration Distribution of Chloride Ion in Cracked Concrete

2013 ◽  
Vol 351-352 ◽  
pp. 1581-1584
Author(s):  
Bo Yu ◽  
Zhong Hui Huang ◽  
Ming Wu ◽  
Hui Liang Sun ◽  
Lu Feng Yang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Concentration Distribution ◽  
Chloride Ion ◽  
Diffusion Path ◽  
Chloride Ions ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cracked Concrete ◽  
Ions Transport

Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. The time-dependent chloride diffusion model was established based on the time-dependent chloride diffusion coefficient and the Ficks second law of diffusion. The influence of crack on the concentration distribution of chloride ion in cracked concrete was quantificationally investigated.

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