scholarly journals Analysis for Effect of Diffusion Parameter with Time-dependent Diffusion Coefficient on Service Life Considering Deterministic and Probabilistic Method

2016 ◽  
Vol 4 (3) ◽  
pp. 259-268
Author(s):  
Seung-Jun Kwon
Keyword(s):  
Diffusion Coefficient ◽  
Service Life ◽  
Probabilistic Method ◽  
Time Dependent ◽  
Diffusion Parameter

scholarly journals Effective Bio-Slime Coating Technique for Concrete Surfaces under Sulfate Attack

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1512
Author(s):  
Keun-Hyeok Yang ◽  
Hee-Seob Lim ◽  
Seung-Jun Kwon
Keyword(s):  
Diffusion Coefficient ◽  
Service Life ◽  
Coating Layer ◽  
Sulfate Attack ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusivity ◽  
Concrete Body ◽  
Layer Technique ◽  
Coating Layers

The service life of concretes exposed to sulfate decreases as the concrete body expands due to the formation of gypsum and ettringite. Bacteria-based repair coating layers, which have been studied lately, are aerobic and very effective on the sulfate attack. In this study, bio-slime repair coating layers were fabricated using bacteria, and chloride diffusion experiments were performed. In addition, the service life of concrete under sulfate attack was evaluated using time-dependent diffusivity and a multi-layer technique. Chloride diffusivity was compared with sulfate diffusivity based on literature review, and the results were used to consider the reduction in the diffusion coefficient. In the analysis results, the service life of concrete was evaluated to be 38.5 years without bio-slime coating layer, but it was increased to 41.5–54.3 years using it. In addition, when the thickness of the bio-slime coating layer is 2.0 mm, the service life can be increased by 1.31–2.15 times if the sulfate diffusion coefficient of the layer is controlled at a level of 0.1 ~ 0.3 × 10−12 m2/s. Eco-friendly and aerobic bio-slime coating layers are expected to effectively resist sulfate under appropriate construction conditions.

Environmental Impact due to Repairs by Surface Treatment on Concrete Structures Exposed to Chloride Environment

2016 ◽  
Vol 711 ◽  
pp. 974-981
Author(s):  
Aruz Petcherdchoo ◽  
Chotima Ongsopapong
Keyword(s):  
Diffusion Coefficient ◽  
Environmental Impact ◽  
Service Life ◽  
Surface Treatment ◽  
Time Dependent ◽  
Life Extension ◽  
Free Service ◽  
Before And After ◽  
Chloride Attack ◽  
Service Life Extension

This paper presents the environmental impact in terms of CO2 and service life extension due to repairs by surface treatment on concrete structures exposed to time-dependent chloride attack. The service life extension is defined as the difference between the corrosion-free service life of concrete before and after surface treatment by silanes. The corrosion-free service life is predicted based on considering the mechanism of chloride diffusion which can be described using the partial differential equation (PDE) of the Fick’s second law. With the surface treatment, solving the PDE is complicated due to non-constant diffusion coefficient. Furthermore, if the diffusion coefficient is time-dependent, it is even more complicated to solve the PDE. Therefore, numerical computation by the Crank-Nicolson based finite difference method is introduced as a computational tool. From computation, the chloride profiles before and after different surface treatment strategies can be calculated considering time-dependent chloride attack. Furthermore, the environmental impact in terms of CO2 due to surface treatment is also presented. Finally, numerical examples to calculate the service life extension after surface treatments and the environmental impacts are compared.

scholarly journals Effect of Amount of Fibre and Damage Level on Service Life of SFR Recycled Concrete in Aggressive Environment

Buildings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 489
Author(s):  
Petr Lehner ◽  
Marie Horňáková
Keyword(s):  
Diffusion Coefficient ◽  
Service Life ◽  
Numerical Models ◽  
Recycled Concrete ◽  
Time Dependent ◽  
Damage Level ◽  
Constant Diffusion Coefficient ◽  
Strength Capacity ◽  
Constant Diffusion

The paper presents a numerical calculation of the service life of concrete structures considering the effect of chlorides in the case of the material properties of structural lightweight waste aggregate concrete. Different amounts of fibres (0.0%, 1.0%, and 1.5%) and different values of compressive preloading (0%, 50%, and 100% of the ultimate strength capacity-USC) were considered. The subject of the research was the comparison of the influence of the constant diffusion coefficient and the time-dependent diffusion coefficient regarding the service life of the selected structure. Nine groups of material characteristics in combination with two numerical models are compared. A time-dependent diffusion coefficient and maturation coefficient, which were determined based on long-term monitoring (up to 461 days), were accepted for the numerical modelling. Thanks to time-dependent parameters, it is possible to observe the results of the theoretical service life of the structure and the influence of the mentioned factors. The analysed structure can be considered as the upper layer of an industrial floor in a chemical plant. It is important to determine the theoretical service life at which the structure shall be inspected or replaced. The results, in general, show that a higher amount of fibres reduces the service life as well as the preloading of the structure. An exception was a mixture with 1% of fibre loaded to 50% USC, which shows a lower diffusion coefficient than the specimens without preloading.

scholarly journals Time-Dependent Diffusion Coefficients for Chaotic Advection due to Fluctuations of Convective Rolls

Fluids ◽  
2018 ◽  
Vol 3 (4) ◽  
pp. 99 ◽  
Author(s):  
Kazuma Yamanaka ◽  
Takayuki Narumi ◽  
Megumi Hashiguchi ◽  
Hirotaka Okabe ◽  
Kazuhiro Hara ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Liquid Crystals ◽  
Diffusion Coefficients ◽  
Coarse Graining ◽  
Chaotic Advection ◽  
Time Dependent ◽  
Local Order ◽  
Weak Turbulence ◽  
Normal Diffusion ◽  
Convective Rolls

The properties of chaotic advection arising from defect turbulence, that is, weak turbulence in the electroconvection of nematic liquid crystals, were experimentally investigated. Defect turbulence is a phenomenon in which fluctuations of convective rolls arise and are globally disturbed while maintaining convective rolls locally. The time-dependent diffusion coefficient, as measured from the motion of a tagged particle driven by the turbulence, was used to clarify the dependence of the type of diffusion on coarse-graining time. The results showed that, as coarse-graining time increases, the type of diffusion changes from superdiffusion → subdiffusion → normal diffusion. The change in diffusive properties over the observed timescale reflects the coexistence of local order and global disorder in the defect turbulence.

Time dependent diffusion coefficient in a disordered medium

1996 ◽  
Vol 104 (1) ◽  
pp. 206-209 ◽  
Author(s):  
Thomas M. de Swiet ◽  
Pabitra N. Sen
Keyword(s):  
Diffusion Coefficient ◽  
Time Dependent ◽  
Disordered Medium
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