Influence of Aggregate Volume Ratio of Mortar on the Migration of Cations Using the Accelerated Lithium Migration Technique

2011 ◽  
Vol 230-232 ◽  
pp. 400-404
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Steady State ◽  
Current Density ◽  
Linear Correlation ◽  
Volume Ratio ◽  
Constant Current ◽  
Constant Current Density ◽  
Pass Through ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

This study utilizes mortar specimens, to design 3 different a/c ratios of 2.25, 2.75, and 3.25. The aggregate volume ratios (Vf) are 46 %, 52 %, and 57 %, respectively, while the w/c ratio is 0.5, and undergoing a 9, 12, and 15 A/m2 constant current density Accelerated Lithium Migration Technique after curing for 3 months. Results show that, on specimens applied with the same current density, the time of Li+ to pass through the specimen, and steady state flux and migration coefficient all exhibit a positive linear correlation with Vf. At the same time, the non-steady state migration coefficient for Li+ have a negative linear correlation with Vf.

Migration of Cations in Mortar under an Electrical Field Controlled by a Constant Current Density

2010 ◽  
Vol 150-151 ◽  
pp. 362-372 ◽  
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Current Density ◽  
Constant Current ◽  
Alkali Silica Reaction ◽  
Test Cases ◽  
Applied Current ◽  
Electrical Field ◽  
Constant Current Density ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

In this study, an Accelerated Lithium Migration Technique (ALMT) was applied to simultaneously drive alkali out and lithium into concrete as a remedy for alkali-silica reaction (ASR) problem. The mortar specimens used in the experiments contained 2.0% Na2Oeq. Constant current denities were applied during the ALMT testing process. The anolyte and catholyte solutions consisted of LiOH．H2O and Ca(OH)2, respectively. The results show that there are a well correlated linear relationship between the applied current density and the steady flux and migration coefficient of the Li+. During the process of ionic migration, K+ was first removed completely from the specimen, followed by Na+, after which the Li+ flux remained steady. The system resistance initially decreased, and then increased gradually. The time corresponding to when the Li+ concentration in the cathode/Li+ in the source cell was equal to 0.1% indicates the time-span needed for Li+ to penetrate throughout the specimen. Furthermore, the accumulated charge carried by the cations and the accumulated charge applied during testing showed a similar in all test cases.

Effect of Electric Field on Cation Migration and Electrode Reactions of Mortar with Different W/C Ratios

2011 ◽  
Vol 399-401 ◽  
pp. 1320-1325
Author(s):  
Chih Chien Liu ◽  
Wen Ten Kuo ◽  
Shu Wang Hsu
Keyword(s):  
Constant Current ◽  
Type I ◽  
Constant Current Density ◽  
Mortar Specimen ◽  
Electrode Reactions ◽  
Increase With Increase ◽  
Cation Migration ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

This study used Type I Portland cement with Na2Oeq of 0.67 % to fabricate a mortar specimen with a w/c ratio of 0.5 and a dimension of φ10 × 3 cm, adjusted to the 6 w/c ratios of 0.35, 0.40, 0.45, 0.50, 0.55 and 0.60. The specimen was applied constant current density of 9 A/m2 during the Accelerated Lithium Migration Technique (ALMT) experiment. The results show that during the application of the current, over 86.4% of the electricity applied used in the production of gas through electrode reactions, and about 3.9-4.6% in cation migration. The required time of removal for Na+ and K+ decreased with increases in w/c ratio. The average removal percentage of Na+ and K+ increasing with the increase in w/c ratio. There was a good linear relationship between the steSuperscript textSuperscript textady-state flux and migration coefficient of Li+ and w/c ratio, and the steady flux of migration coefficient increase with increase in the w/c ratio.

On the Relationship between Deteriorated Level of ASR Damaged Concrete and Lithium Migration from Acceleration Lithium Migration Technique Test

2010 ◽  
Vol 163-167 ◽  
pp. 3812-3819
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Steady State ◽  
Linear Relationship ◽  
Current Density ◽  
Lithium Ion ◽  
Sodium Ion ◽  
Electrochemical Technique ◽  
The Relationship ◽  
Lithium Migration ◽  
Migration Technique

This research is to study the effect of deteriorated level on the ions migration in inhibiting the concrete damaged by ASR using electrochemical technique. Cylindrical concrete specimens made by reactive sandstone with 10 cm diameter and 5 cm height were prepared at the ages of 7, 14, 28, 90, and 180 days curing in a 38°C and 100% R.H. storage environment. The accelerated lithium migration technique (ALMT) was performed using LiOH H2O and Ca(OH)2 as electrolytes for anode and cathode, respectively. 9 A/m2 current density was used to drive lithium ion into and remove sodium ion out of the concrete. The results show that the rates of ions migration increase with increasing the deteriorated level of specimen. Furthermore, a linear relationship exists between the non-steady state migration coefficient of Li+ and the deteriorated level of specimen.

The morphology and mechanism of formation of porous anodic films on aluminium

1970 ◽  
Vol 317 (1531) ◽  
pp. 511-543 ◽  
Keyword(s):  
Steady State ◽  
Layer Thickness ◽  
Current Density ◽  
Barrier Layer ◽  
Anodic Oxide ◽  
Constant Current ◽  
Cell Diameter ◽  
Anodic Films ◽  
Constant Current Density ◽  
Barrier Layer Thickness

The morphology of porous anodic oxide films formed on aluminium in phosphoric acid electrolytes at constant current density or voltage, and under changing electrical or electrolytic conditions, has been studied quantitatively by electron microscopy. Replicas from film sections and from both film interfaces have been prepared, as well as transmission micrographs of thin films, produced under accurately defined conditions. During formation at constant current density, pore initiation occurs by the merging of locally thickening oxide regions, which seem related to the substructure of the substrate, and the consequent concentration of current into the residual thin areas. The pores grow in diameter and change in number until the steady-state morphology is established. The film barrier layer thickness has been measured directly for the first time. The steady-state barrier-layer thickness, cell diameter and pore diameter are all observed to be directly proportional to the formation voltage. It becomes evident that the barrier-layer thickness, decided largely by an equilibrium established between oxide formation in the barrier-layer and field-assisted dissolution (probably thermally enhanced) at the pore bases, determines the cell and pore sizes by a simple geometrical mechanism. Anion incorporation into the film and its hydrogen-bonded structure play secondary roles to these factors in determining the actual film morphology, although not its subsequent properties. A consequence of the mechanism is that, at constant current density, relatively non-aggressive electrolytes give thicker barrier layers, larger cells and larger pores next to the barrier layer than aggressive media, although subsequent pore widening at the outer surface of the film by simple chemical dissolution is more severe in aggressive electrolytes.

scholarly journals Transient Current Density in a Pair of Long Parallel Conductors

2021 ◽  
Vol 11 (15) ◽  
pp. 6920
Author(s):  
Oldřich Coufal
Keyword(s):  
Steady State ◽  
Cross Section ◽  
Current Density ◽  
Circular Cross Section ◽  
Transient Current ◽  
Constant Current ◽  
Voltage Source ◽  
Sinusoidal Voltage ◽  
Steady State Current ◽  
Maximum Current

Two infinitely long parallel conductors of arbitrary cross section connected to a voltage source form a loop. If the source voltage depends on time, then due to induction there is no constant current density in the loop conductors. It is only recently that a method has been published for accurately calculating current density in a group of long parallel conductors. The method has thus far been applied to the calculation of steady-state current density in a loop connected to a sinusoidal voltage source. In the present article, the method is used for an accurate calculation of transient current using transient current density. The transient current is analysed when connecting and short-circuiting the sources of sinusoidal, constant and sawtooth voltages. For circular cross section conductors, the dependences of maximum current density, maximum current and the time of achieving steady state on the source frequency, the distance of the conductors and their resistivity when connecting the source of sinusoidal voltage are examined.

Study on Special Morphology Hydroxyapatite Bioactive Coating by Electrochemical Deposition

2013 ◽  
Vol 537 ◽  
pp. 256-260
Author(s):  
Cai Ge Gu ◽  
Qian Gang Fu ◽  
He Jun Li ◽  
Jin Hua Lu ◽  
Lei Lei Zhang
Keyword(s):  
Electrochemical Deposition ◽  
Current Density ◽  
Electrolyte Concentration ◽  
Spherical Particles ◽  
Constant Current ◽  
Constant Current Density ◽  
Depth Direction ◽  
Special Morphology ◽  
Calcium Phosphate Coatings ◽  
Coating Weight

Bioactive calcium phosphate coatings were deposited on carbon/carbon（C/C） composites using electrochemical deposition technique. The effects of electrolyte concentration and constant current density on morphology, structure and composition of the coating were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) spectroscopy. The results show that, the coating weight elevated gradually with the increase of electrolyte concentration, and the morphology of coatings changed from spherical particles to nanolamellar crystals with interlocking structure initially. Then the coating transformed into seaweed-like and nano/micro-sized crystals along the depth direction of the coating. The coatings showed seaweed-like morphology as the deposition current density was less than 20mA. With the less current density, the coating became more homogenous. However, the coating was fiakiness crysal, with needlike crystal stacked upside as the current density reached to 20mA/cm2. The coating weight was improved gradually when the current density increased from 2.5mA/cm2 to 10mA/cm2, then reduced with the increasing current density in the range of 10 to 20mA/cm2.

Effect of Water on the IR Properties of Mg2+ Intercalated Electrochromic Nb2O5 Thin Films

2006 ◽  
Vol 972 ◽  
Author(s):  
Gargi Agarwal ◽  
G B Reddy
Keyword(s):  
Thin Films ◽  
Aqueous Solution ◽  
Water Content ◽  
Current Density ◽  
Sol Gel ◽  
Constant Current ◽  
Cyclic Stability ◽  
Constant Current Density ◽  
Effect Of Water ◽  
Ftir Studies

AbstractSol-gel derived Nb2O5 thin films were intercalated with Mg2+,using the non-aqueous solution of Mg(ClO4)2 in propylene carbonate (pc) as the electrolyte. 2% and 4% ( volume %) water was added to the electrolyte to study the effect of water on the electrochromic properties of Nb2O5. This paper presents the changes in optical and structural properties of the intercalated films with and without water in the electrolyte. The ratio (x) of the Mg2+ and Nb atoms has been controlled by optimizing the intercalation duration under a constant current density. The fall in transmittance on intercalation (for x= 0.8) increased by 15% with 4% water in the electrolyte, compared to the film intercalated without water. FTIR studies show that water is incorporated in the films on intercalation and small quantities of Mg(OH)2 and Nb-OH are formed along with Mg-O-Nb bonds. The presence of water in electrolyte decreases water content in the films and enhances the formation of Mg(OH)2, Mg-O-Nb and Nb-OH bonds. The recovery of Mg2+ on deintercalation is slightly reduced in presence of water in the electrolyte. The cyclic stability of the films intercalated without water is more than that of the films intercalated in presence of water.

Study of growth of dot and column in porous silicon samples of various thicknesses prepared at a constant current density

2015 ◽  
Vol 73 ◽  
pp. 110-115 ◽  
Author(s):  
Fateh Singh Gill ◽  
Varij Panwar ◽  
Himanshu Gupta ◽  
G.S. Kalra ◽  
Shanta Chawla ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Current Density ◽  
Constant Current ◽  
Constant Current Density
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