Porosity/Diffusivity And Alkali-Silica Reaction

1988 ◽  
Vol 137 ◽  
Author(s):  
Micheline Moranville-Resocurd
Keyword(s):  
Chemical Processes ◽  
Alkali Silica Reaction ◽  
Physical Processes ◽  
Alkali Ions ◽  
Water Imbibition ◽  
Corrosion Of Steel ◽  
Physical And Chemical ◽  
Secondary Chemical ◽  
And Diffusion

AbstractPhysical and chemical processes are responsible for the alkali-silica reaction in concrete. Physical processes include (i) migration of hydroxyl and alkali ions (ii) swelling by water imbibition of the alkali-silica gel produced, (iii) development of cracks. Chemical processes involve (i) neutralisation of acidic silanol groups and attack of siloxane bridges, both by OH- ions (ii) formation of an alkali silicate. These reactions result in a breakdown in the silica structure and diffusion of some silicate and impregnate the cement paste filling the capillary pores. The increase in permeability due to the opening and progression of cracks facilitates secondary chemical deteriorations like the formation of ettrinqite, carbonation and corrosion of steel reinforcement. Recent studies have emphasized the role of Ca(OH)2 preventing the dissolution or miqration of freed silica out of the structure. Only the removal of Ca(OH)2 is able to stop the expansion of concrete.The paper will present some new interpretations of alkali-silica reaction related to the diffusivity of various ions from the pore solution.

scholarly journals Are the Fractionation Corrections Correct: Are the Isotopic Shifts for 14C/12C Ratios in Physical Processes and Chemical Reactions Really Twice Those for 13C/12C?

Radiocarbon ◽  
2011 ◽  
Vol 53 (4) ◽  
pp. 691-704 ◽  
Author(s):  
John Southon
Keyword(s):  
Chemical Reactions ◽  
Isotopic Fractionation ◽  
Theoretical Work ◽  
Chemical Processes ◽  
Physical Processes ◽  
Isotopic Discrimination ◽  
True Value ◽  
A Value ◽  
Isotopic Shifts ◽  
Physical And Chemical

Conventional radiocarbon calculations correct for isotopic fractionation using an assumed value of 2.0 for the fractionation of 14C relative to 13C. In other words, isotopic discrimination in physical and chemical processes is assumed to cause relative shifts in 14C/12C ratios that are exactly double those of 13C/12C. This paper analyzes a 1984 experiment that produced a value for the fractionation ratio in photosynthesis of 2.3, which is used to this day by some researchers in the fields of hydrology and speleothem geochemistry. While the value of 2.3 is almost certainly incorrect, theoretical work suggests that the true value may indeed deviate from 2.0, which would have significant implications for 14C calculations.

scholarly journals Relationship between snow microstructure and physical and chemical processes

2012 ◽  
Vol 12 (11) ◽  
pp. 30409-30541 ◽  
Author(s):  
T. Bartels-Rausch ◽  
H.-W. Jacobi ◽  
T. F. Kahan ◽  
J. L. Thomas ◽  
E. S. Thomson ◽  
...  
Keyword(s):  
Chemical Reactivity ◽  
Experimental Studies ◽  
Chemical Processes ◽  
Field Observations ◽  
Physical Processes ◽  
Micro Scale ◽  
Surface Disorder ◽  
Snow Microstructure ◽  
Physical And Chemical

Abstract. Ice and snow in the environment are important because they not only act as a host to rich chemistry but also provide a matrix for physical exchanges of contaminants within the ecosystem. This review discusses how the structure of snow influences both chemical reactivity and physical processes, which thereby makes snow a unique medium for study. The focus is placed on impacts of the presence of liquid and surface disorder using many experimental studies, simulations, and field observations from the molecular to the micro-scale.

Planetary Climates

2013 ◽  
Author(s):  
Andrew P. Ingersoll
Keyword(s):  
Current Knowledge ◽  
Chemical Processes ◽  
Physical Processes ◽  
Climate History ◽  
Planetary Satellite ◽  
Chemical Mechanisms ◽  
Term Evolution ◽  
Earth’S Climate ◽  
Physical And Chemical

This clear and concise introduction to planetary climates explains the global physical and chemical processes that determine climate on any planet or major planetary satellite—from Mercury to Neptune and even large moons such as Saturn's Titan. The book presents a tour of our solar system's diverse planetary atmospheres, providing a rich foundation on their structure, composition, circulation, climate, and long-term evolution. Although the climates of other worlds are extremely diverse, the chemical and physical processes that shape their dynamics are the same. As this book makes clear, the better we can understand how various planetary climates formed and evolved, the better we can understand Earth's climate history and future. Explaining current knowledge, physical and chemical mechanisms, and unanswered questions, the book brings the reader to the cutting edge of this field.

Fate of Chemicals

2017 ◽  
Author(s):  
Morton Lippmann ◽  
Richard B. Schlesinger
Keyword(s):  
Biogeochemical Cycles ◽  
Chemical Processes ◽  
Physical And Chemical ◽  
Biotic Environment

This chapter discusses how, following their release into the environment, chemicals may be converted into different forms and/or transferred within and between the atmosphere, hydrosphere, lithosphere, and biosphere. It reviews the physical and chemical processes by which specific pollutants and classes of pollutions may be altered and ultimately dispersed within each of the components of the environment. The role of biogeochemical cycles in the movement of pollutants from the abiotic to the biotic environment is reviewed. Ultimate sinks for pollutants are discussed as are pollutant residues in the environment.

Understanding the role of post-CCVD synthetic impurities, functional groups and functionalization-based oxidation debris on the behaviour of carbon nanotubes as a catalyst support in cyclohexene hydrogenation over Pd nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (91) ◽  
pp. 88538-88545 ◽  
Author(s):  
R. Puskas ◽  
A. Sápi ◽  
Á. Kukovecz ◽  
Z. Kónya
Keyword(s):  
Catalyst Support ◽  
Chemical Properties ◽  
Pd Nanoparticles ◽  
Chemical Processes ◽  
Physical And Chemical Properties ◽  
Surface Chemical ◽  
Physical And Chemical ◽  
Striking Effect ◽  
And Chemical Properties

Tuning of the surface modification has a striking effect on the physical and chemical properties of CNTs in surface chemical processes.

scholarly journals Impact of Biocorrosion on the Durability of Etics and Empirical Findings About the Periodocity of Maintenance

2013 ◽  
Vol 21 (2) ◽  
pp. 21-28
Author(s):  
Naďa Antošová
Keyword(s):  
Building Materials ◽  
Composite System ◽  
Chemical Processes ◽  
Biological Factors ◽  
Wide Range ◽  
Living Organisms ◽  
Physical And Chemical ◽  
The Impact ◽  
Complete Collapse

Abstract Generally, the role of living organisms (especially bacteria, cyanophytes, algae and fungi) in the physical and chemical processes of the biocorrosion of an external thermal insulation composite system (ETICS) is underestimated. These organisms are the ones that are responsible for a wide range of changes in or "diseases" of building materials and constructions, including damage to a building´s appearance or the destruction and complete collapse of the characteristics and requirements of materials and the ETICS construction. The following article concerns the impact of biological factors on the durability of ETICS. It shows the importance of and necessity to maintain it, and the method and periodicity of the maintenance.

Modelling of migration of leached radionuclides by groundwater

1986 ◽  
Vol 319 (1545) ◽  
pp. 97-108
Keyword(s):  
Mathematical Modelling ◽  
Water Flow ◽  
Chemical Processes ◽  
Levels Of Detail ◽  
Mathematical Expressions ◽  
Waste Repository ◽  
Physical And Chemical ◽  
Future Work ◽  
The Way

Radionuclides may be carried by groundwater from an underground waste repository to places accessible to man. The central role of mathematical modelling is to predict how their concentration varies in time at positions around the repository. This requires consideration of the physical and chemical processes at work and representation of the most important by mathematical expressions. As this can be done on several levels of detail both for water flow and radionuclide behaviour the resulting overall models can differ greatly in completeness and complexity. We discuss briefly some examples of such models, the data they require, the way these are gathered and how they have been used in practice. It is necessary to examine the validity of proposed models and we describe some approaches to this. We indicate the strengths and weaknesses of some commonly adopted models and outline current and future work aimed at improving our understanding.

scholarly journals Laboratory simulation of physical and chemical processes in interstellar ices

1997 ◽  
Vol 178 ◽  
pp. 331-340 ◽  
Author(s):  
W.A. Schutte
Keyword(s):  
Surface Reactions ◽  
Current Situation ◽  
Chemical Processes ◽  
Laboratory Simulation ◽  
Physical Processes ◽  
Atoms And Molecules ◽  
Interstellar Ice ◽  
Chemical Conditions ◽  
Uv Photons ◽  
Physical And Chemical

We review the techniques which are applied to study by means of laboratory simulation the chemical and physical processes taking place in ices in interstellar dense clouds. We summarize the current situation with regard to spectroscopy of interstellar ice analogs and with regard to the simulation of chemical processes such as modification of the ices by UV photons and surface reactions between reactive atoms and molecules. It is discussed how such data can be used to explore the potential of the icy mantles both as a record of the various chemical conditions that occur in dense clouds and as an environment for unique interstellar chemical processes.

Ignition delays of biodiesel-diesel blends: Investigations into the role of physical and chemical processes

Fuel ◽  
2021 ◽  
Vol 303 ◽  
pp. 121251
Author(s):  
Phuong X. Pham ◽  
Nam V.T. Pham ◽  
Thin V. Pham ◽  
Vu H. Nguyen ◽  
Kien T. Nguyen
Keyword(s):  
Chemical Processes ◽  
Physical And Chemical

scholarly journals ALUMINIUM BRONZE. NANOSTRUCTURAL PROCESSES OF MELTING AND MOULDING

2018 ◽  
pp. 12-15
Author(s):  
E. I. Marukovich ◽  
V. Yu. Stetsenko
Keyword(s):  
Dissolved Oxygen ◽  
Chemical Processes ◽  
Adsorbed Oxygen ◽  
Aluminum Bronze ◽  
Aluminium Bronze ◽  
Physical And Chemical

It is shown that melting and molding of aluminum bronze are difficult physical and chemical processes. In them the major role is played by the centers of crystallization of dendrites of a a-phase, the a-phase nanocrystals dissolved and the adsorbed oxygen and hydrogen. The role of the modifying crystals of an intermetallid of ZrAl3 is reduced to reduction of concentration of the dissolved oxygen and hydrogen and an intensifi ation of process of coagulation of nanocrystals of a a-phase in the centers of crystallization of dendrites of a a-phase.

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