Chloride profile modeling contemplating the convection zone based on concrete structures present for more than 40 years in different marine aggressive zones

2019 ◽  
Vol 198 ◽  
pp. 345-358 ◽  
Author(s):  
Carlos Eduardo Tino Balestra ◽  
Thiago Alessi Reichert ◽  
Wagner Alessandro Pansera ◽  
Gustavo Savaris
Keyword(s):  
Convection Zone ◽  
Concrete Structures ◽  
Chloride Profile ◽  
Profile Modeling

Nanoparticle Injection into Concrete Using Electromigration

2014 ◽  
Vol 1054 ◽  
pp. 6-10 ◽  
Author(s):  
Jiří Němeček ◽  
Yun Ping Xi
Keyword(s):  
Reinforced Concrete ◽  
Electric Field ◽  
Concrete Structures ◽  
Chloride Penetration ◽  
Reinforced Concrete Structures ◽  
Testing Chamber ◽  
Chloride Profile ◽  
Nanosilica Particles ◽  
Penetration Tests ◽  
Small Voltage

This paper aims at investigation of possibilities and effectiveness of chloride extraction from concrete and nanoparticle injection into existing reinforced concrete structures by means of electromigration technique. Concrete specimens are exposed to accelerated chloride penetration tests in order to simulate a natural chloride exposure. The developed chloride profile is removed by electroextraction by reversing the polarity in the testing chamber. In a similar manner, concrete specimens are injected with different concentrations of colloidal nanosilica particles. It was shown in the paper that chlorides can be effectively extracted from the concrete using small voltage lasting for several days. Higher concentration solutions of nanosilica can also be effectively transported into concrete via the electric field. Once injected nanosilica can act as microstructure densifier and further reduce chloride penetration as demonstrated by decreased diffusivity of the treated concrete.

Analysis of Service Life of Surface Coated-Concrete Structures Considering Climate Change and Chloride Ingress

2020 ◽  
Vol 842 ◽  
pp. 299-305
Author(s):  
Xiao Yong Wang
Keyword(s):  
Climate Change ◽  
Service Life ◽  
Surface Coating ◽  
Concrete Structures ◽  
Parameter Analysis ◽  
Chloride Ingress ◽  
Arrhenius Law ◽  
Chloride Diffusivity ◽  
Chloride Profile ◽  
Marine Concrete

Mortar surface coating is widely used as a finishing material to extend the service life and improve chloride ingression resistance of marine concrete structures. This study proposes a model for estimating the service life of surface-coated marine concrete considering climate change. First, the increase of chloride diffusivity due to climate change is considered using Arrhenius’ law. A two-layered chloride ingress model is used to analyze chloride profile. The probability-based approach is used to find the service life of concrete structures. Second, parameter analysis is performed considering the effects of various factors on service life. The influences of thickness and chloride diffusivity of the coating and substrate concrete on service life are highlighted. The reduction of service life due to climate change is clarified based on the regression of results of parameter analysis. For marine concrete with 50 years’ service life, 6% service life reduction occurs because of climate change.

Effect of Micro-Climatic Condition on Durability Performance of Concrete

2010 ◽  
Vol 452-453 ◽  
pp. 545-548
Author(s):  
In Seok Yoon
Keyword(s):  
Climatic Condition ◽  
Concrete Structures ◽  
Chloride Content ◽  
Chloride Ions ◽  
In Situ Monitoring ◽  
Tidal Zone ◽  
Chloride Diffusivity ◽  
Engineering Society ◽  
Chloride Profile

The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the topic have been accomplished, however, it is not easy to review literatures about environmental analysis, in particular micro-climatic condition of concrete under chloride laden environment. Since the durability of concrete depends on the properties of the surface concrete, micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The outcome will be combined with modules of material parameters such as chloride diffusivity, surface chloride content, and so on. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete at atmospheric zone or tidal zone.

Alpha-Effect, Current and Kinetic Helicities for Magnetically Driven Turbulence, and Solar Dynamo

2000 ◽  
Vol 179 ◽  
pp. 387-388
Author(s):  
Gaetano Belvedere ◽  
V. V. Pipin ◽  
G. Rüdiger
Keyword(s):  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Convection Zone ◽  
Solar Surface ◽  
Momentum Transport ◽  
Angular Momentum Transport ◽  
Magnetic Buoyancy ◽  
Alpha Effect ◽  
Current Helicity

Extended AbstractRecent numerical simulations lead to the result that turbulence is much more magnetically driven than believed. In particular the role ofmagnetic buoyancyappears quite important for the generation ofα-effect and angular momentum transport (Brandenburg & Schmitt 1998). We present results obtained for a turbulence field driven by a (given) Lorentz force in a non-stratified but rotating convection zone. The main result confirms the numerical findings of Brandenburg & Schmitt that in the northern hemisphere theα-effect and the kinetic helicityℋkin= 〈u′ · rotu′〉 are positive (and negative in the northern hemisphere), this being just opposite to what occurs for the current helicityℋcurr= 〈j′ ·B′〉, which is negative in the northern hemisphere (and positive in the southern hemisphere). There has been an increasing number of papers presenting observations of current helicity at the solar surface, all showing that it isnegativein the northern hemisphere and positive in the southern hemisphere (see Rüdigeret al. 2000, also for a review).

Solar Internal Rotation and Dynamo Waves: A Two-Dimensional Asymptotic Solution in the Convection Zone

2000 ◽  
Vol 179 ◽  
pp. 379-380
Author(s):  
Gaetano Belvedere ◽  
Kirill Kuzanyan ◽  
Dmitry Sokoloff
Keyword(s):  
Magnetic Field ◽  
Asymptotic Solution ◽  
Internal Rotation ◽  
Convection Zone ◽  
General Idea ◽  
Dynamo Model ◽  
Axially Symmetric ◽  
Dynamo Action ◽  
Regeneration Rate ◽  
Dynamo Waves

Extended abstractHere we outline how asymptotic models may contribute to the investigation of mean field dynamos applied to the solar convective zone. We calculate here a spatial 2-D structure of the mean magnetic field, adopting real profiles of the solar internal rotation (the Ω-effect) and an extended prescription of the turbulent α-effect. In our model assumptions we do not prescribe any meridional flow that might seriously affect the resulting generated magnetic fields. We do not assume apriori any region or layer as a preferred site for the dynamo action (such as the overshoot zone), but the location of the α- and Ω-effects results in the propagation of dynamo waves deep in the convection zone. We consider an axially symmetric magnetic field dynamo model in a differentially rotating spherical shell. The main assumption, when using asymptotic WKB methods, is that the absolute value of the dynamo number (regeneration rate) |D| is large, i.e., the spatial scale of the solution is small. Following the general idea of an asymptotic solution for dynamo waves (e.g., Kuzanyan & Sokoloff 1995), we search for a solution in the form of a power series with respect to the small parameter |D|–1/3(short wavelength scale). This solution is of the order of magnitude of exp(i|D|1/3S), where S is a scalar function of position.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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