Time dependency of chloride diffusion coefficients in concrete

Author(s):  
J. Visser
2013 ◽  
Vol 721 ◽  
pp. 148-152
Author(s):  
Zheng Chen ◽  
Xi Bin Zhao ◽  
Yan Hua Yuan ◽  
Zhong Hua Wang ◽  
Lu Feng Yang ◽  
...  

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.


2011 ◽  
Vol 243-249 ◽  
pp. 5703-5710 ◽  
Author(s):  
Lu Guang Song ◽  
Wei Sun ◽  
Jian Ming Gao ◽  
Yun Sheng Zhang

This paper investigates the influences of dosage of ground granulated blast furnace slag (GGBS) (0%, 20%, 40%, 60% and 80%) to chloride diffusion coefficient. And the time dependency of apparent diffusion coefficient as the submerging time from 60 days to 360days has also been studied. The result shows that the addition of GGBS into concrete has great influence on the chloride diffusion. The diffusion coefficients of the mixes containing GGBS decrease rapidly with time than that of the mix PC Control. But there were little differences of the values of apparent diffusion coefficients among the mixes SL20, SL40 and SL60. The addition of GGBS in concrete has great influence on the time dependency of concrete. And the concrete which has 40%-60% replacement of GGBS has greater ability to resist the diffusion of chloride than other replacement.


Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1166 ◽  
Author(s):  
Ahmed Abd El Fattah ◽  
Ibrahim Al-Duais ◽  
Kyle Riding ◽  
Michael Thomas ◽  
Salah Al-Dulaijan ◽  
...  

Reinforcing steel corrosion, caused by chloride ingress into concrete, is the leading cause of reinforced concrete deterioration. One of the main findings in the literature for reducing chloride ingress is the improvement of the durability characteristics of concrete by the addition of supplementary cementitious materials (SCMs) and/or chemical agents to concrete mixtures. In this study, standard ASTM tests—such as rapid chloride permeability (RCPT), bulk diffusion and sorptivity tests—were used to measure concrete properties such as porosity, sorptivity, salt diffusion, and permeability. Eight different mixtures, prepared with different SCMs and corrosion inhibitors, were tested. Apparent and effective chloride diffusion coefficients were calculated using bound chloride isotherms and time-dependent decrease in diffusion. Diffusion coefficients decreased with time, especially with the addition of SCMs and corrosion inhibitors. The apparent diffusion coefficient calculated using the error function was slightly lower than the effective diffusion coefficient; however, there was a linear trend between the two. The formation factor was found to correlate with the effective diffusion coefficient. The results of the laboratory tests were compared and benchmarked to their counterparts in the marine exposure site in the Arabian Gulf in order to identify laboratory key tests to predict concrete durability. The overall performance of concrete containing SCMs, especially fly ash, were the best among the other mixtures in the laboratory and the field.


Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5522
Author(s):  
Jerzy Jasielec ◽  
Jakub Stec ◽  
Krzysztof Szyszkiewicz-Warzecha ◽  
Artur Łagosz ◽  
Jan Deja ◽  
...  

A non-equilibrium diffusion–reaction model is proposed to describe chloride transport and binding in cementitious materials. A numerical solution for this non-linear transport with reaction problem is obtained using the finite element method. The effective chloride diffusion coefficients and parameters of the chloride binding are determined using the inverse method based on a diffusion–reaction model and experimentally measured chloride concentrations. The investigations are performed for two significantly different cements: ordinary Portland and blast furnace cements. The results are compared with the classical diffusion model and appropriate apparent diffusion coefficients. The role of chloride binding, with respect to the different binding isotherms applied, in the overall transport of chlorides is discussed, along with the applicability of the two models. The proposed work allows the determination of important parameters that influence the longevity of concrete structures. The developed methodology can be extended to include more ions, electrostatic interactions, and activity coefficients for even more accurate estimation of the longevity.


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