Chemische Stabilität von Natriummonofluorphosphat in der Porenlösung des Betons / Chemical stability of sodium monofluorophosphate in the pore solution of concrete

1998 ◽  
Vol 4 (4) ◽  
pp. 423-434
Author(s):  
A. Gerdes ◽  
F. H. Wittmann
Keyword(s):  
Aqueous Solution ◽  
Calcium Phosphate ◽  
Chemical Stability ◽  
Calcium Fluoride ◽  
Corrosion Inhibitors ◽  
Pore Solution ◽  
Concrete Surface ◽  
Capillary Suction ◽  
Soluble Calcium ◽  
Non Destructive

Abstract For non-destructive rehabilitation in case of corroding reinforcement the application of sodium monofluorophosphate has been proposed. In practice an aqueous solution of sodium monofluorophosphate is sprayed on the concrete surface. By capillary suction the inhibitor is supposed to he transported into zones surrounding the corroding reinforcement in order to inhibit further corrosion. Hut the results presented here show that monofluorophosphate decomposes in the alkaline concrete pore solution forming slightly soluble calcium phosphate and calcium fluoride. Calcium phosphate and calcium fluoride are not known to work as corrosion inhibitors. The penetration depth in concrete depends on the properties of the microstructure and the rate of decomposition of sodium inonofluorophosphate. These mechanisms strongly limit the possible concentration near the reinforcement bars and, as a consequence, it is very unlikely to reach the level necessary to maintain the inhibition of corrosion in reinforced concrete.

Self-Healing and Repairing Concrete Cracks Based on Bio-Mineralization

2014 ◽  
Vol 629-630 ◽  
pp. 494-503 ◽  
Author(s):  
Chun Xiang Qian ◽  
Mian Luo ◽  
Li Fu Ren ◽  
Rui Xing Wang ◽  
Rui Yang Li ◽  
...  
Keyword(s):  
Concrete Surface ◽  
Cellular Respiration ◽  
Self Healing ◽  
Capillary Suction ◽  
Water Permeation ◽  
Carbonate Ions ◽  
Micro Cracks ◽  
Small Cracks ◽  
The Common ◽  
The One

In this paper, three bio-mineralization mechanisms were proposed to repair cement-based materials cracks. The common feature is that the three are all induced by bacterial. A type of bacterial which can decompose urea and release carbonate ions could be applied to repair micro cracks on concrete surface when combining calcium ions. But what need to be noted is that the way of repairing cracks is passive. Some alkaliphilic bacterial spores could be added to concrete when casted and two different types of bacterial were used to realize the function of self-healing. The sources of carbonate ions made them different, the one release carbonate dioxide through its own cellular respiration, the other could transfer carbon dioxide in air to bicarbonate. Coefficient of capillary suction, apparent water permeation coefficient and area repairing rate were applied to characterize the repairing effectiveness. The tests results were that all three bio-mineralization mechanisms showed excellent repair effect to small cracks formed at early ages. When the bacteria were immobilized by ceramsite, the self-healing effect could be improved for the cracks formed at late ages.

A Review of Ultrasonic Application on Non-destructive Testing Method for Concrete Structure

2014 ◽  
Vol 70 (3) ◽  
Author(s):  
Nasarudin Ahmad ◽  
Ruzairi Abdul Rahim ◽  
Herlina Abdul Rahim ◽  
Mohd Hafiz Fazlul Rahiman
Keyword(s):  
Concrete Structure ◽  
High Speed ◽  
Structural Integrity ◽  
Surface Hardness ◽  
Concrete Surface ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Surface Absorption ◽  
Processing Techniques ◽  
Non Destructive

Although the technique of using ultrasound has reached maturity by given the extent of the development of sensors, but the use of the various areas still can be explore. Many types of ultrasonic sensors are still at conventional in use especially for measurement equipment in the industry. With the advancement of signal processing techniques, high-speed computing, and the latest techniques in image formation based Non-destructive testing (NDT) methods, the usage of ultrasound in concrete NDT testing is very extensive because the technique is very simple and should not damage the concrete structure to be investigated. Many of the parameters need to be tested using ultrasound techniques to concrete can be realized. Starting with the initial process for of concrete mixing until the concrete matured to the age of century old. Various tests are available to test a variety of non-destructive of concrete completely, in which there is no damage to the concrete, through those where the concrete surface is damaged a bit, to partially destructive testing, such as core tests and insertion and pull-off test, which surface to be repaired after the test. Testing parameter features that can be evaluated using non-destructive testing and destructive testing of some rather large and include basic parameters such as density, elastic modulus and strength and surface hardness and surface absorption, and reinforcement location, size and distance from the surface. In some cases it is also possible to check the quality of the workmanship and structural integrity of the ability to detect voids, cracks and delamination. A review of NDT using ultrasound on concrete are presented in this paper to highlight the important aspect to consider when one to consider the application and development of ultrasound testing on concrete by considering ultrasound signal capturing, processing and presenting.

scholarly journals Antibacterial and physical properties of calcium–phosphate and calcium–fluoride nanocomposites with chlorhexidine

2012 ◽  
Vol 28 (5) ◽  
pp. 573-583 ◽  
Author(s):  
Lei Cheng ◽  
Michael D. Weir ◽  
Hockin H.K. Xu ◽  
Alison M. Kraigsley ◽  
Nancy J. Lin ◽  
...  
Keyword(s):  
Calcium Phosphate ◽  
Physical Properties ◽  
Calcium Fluoride

scholarly journals Application of Terrestrial Laser Scanner with an Integrated Thermal Camera in Non-Destructive Evaluation of Concrete Surface of Hydrotechnical Objects

2017 ◽  
Vol 39 (4) ◽  
pp. 35-43 ◽  
Author(s):  
Maria Kowalska ◽  
Janina Zaczek-Peplinska
Keyword(s):  
Laser Scanner ◽  
Concrete Surface ◽  
Terrestrial Laser Scanner ◽  
Thermal Camera ◽  
Concrete Wall ◽  
Temperature Changes ◽  
Thermal Data ◽  
Technical Assessment ◽  
Non Destructive ◽  
Source Of Information

Abstract The authors present possible applications of thermal data as an additional source of information on an object’s behaviour during the technical assessment of the condition of a concrete surface. For the study one of the most recent propositions introduced by Zoller + Fröhlich company was used, which is an integration of a thermal camera with a terrestrial laser scanner. This solution enables an acquisition of geometric and spectral data on the surveyed object and also provides information on the surface’s temperature in the selected points. A section of the dam’s downstream concrete wall was selected as the subject of the study for which a number of scans were carried out and a number of thermal images were taken at different times of the day. The obtained thermal data was confronted with the acquired spectral information for the specified points. This made it possible to carry out broader analysis of the surface and an inspection of the revealed fissure. The thermal analysis of said fissure indicated that the temperature changes within it are slower, which may affect the way the concrete works and may require further elaboration by the appropriate experts. Through the integration of a thermal camera with a terrestrial laser scanner one can not only analyse changes of temperature in the discretely selected points but on the whole surface as well. Moreover, it is also possible to accurately determine the range and the area of the change affecting the surface. The authors note the limitations of the presented solution like, inter alia, the resolution of the thermal camera.

scholarly journals Cement-based materials destruction under the action of deicing salts

2019 ◽  
Vol 298 ◽  
pp. 00053 ◽  
Author(s):  
Ekaterina Potapova ◽  
Ivan Korchunov
Keyword(s):  
Aqueous Solution ◽  
Pore Solution ◽  
Colorimetric Method ◽  
Chloride Ions ◽  
Cement Matrix ◽  
Chloride Solutions ◽  
Deicing Salts ◽  
Cement Based Materials ◽  
Destructive Processes

The results of chloride ions with aqueous solution penetrating into the cement structure were determined with the colorimetric method. Some tendencies of chloride solutions migration in different conditions were established. The article suggests the possible ways of the prevention of destructive processes occur during the excessive pore solution saturation in cement matrix with chloride ions.

scholarly journals Chemical Nature of Remineralized Flattened Enamel Surfaces

1971 ◽  
Vol 50 (6) ◽  
pp. 1621-1625 ◽  
Author(s):  
David J. Krutchkoff ◽  
Nathaniel H. Rowe
Keyword(s):  
Calcium Phosphate ◽  
Calcium Fluoride ◽  
Chemical Nature ◽  
Internal Reflection ◽  
Enamel Surface ◽  
Reflection Spectroscopy ◽  
Chemical Changes ◽  
Amorphous Phosphate ◽  
Internal Reflection Spectroscopy

lnfrared internal reflection spectroscopy (IRS) was used to investigate chemical changes of enamel surface during in vitro remineralization. Specimens were demineralized and exposed either to calcium phosphate-fluoride solutions or to acidulated fluorophosphate. The former showed amorphous phosphate remineralization, and the latter showed surface precipitate interpreted to be calcium fluoride. The significance of previous demineralization time to both forms of remineralization is discussed.

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