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  • 1
    Electronic Resource
    Electronic Resource
    Coarsening in a Viscous Matrix (1998)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 81 (1998), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When a viscous material is three-dimensionally constrained (as when a gel or slurry of glass is infiltrated into the interstices of a particle packing), heat treatment leads to coarsening of the pore-size distribution, rather than densification. The smaller pores generate greater capillary pressure; therefore, they shrink and force the large pores to expand. In this article, the kinetics of coarsening are analyzed, and sample calculations are performed for a body with a lognormal distribution of pore sizes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1998.tb02294.x
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  • 2
    Electronic Resource
    Electronic Resource
    Measuring Permeability of Rigid Materials by a Beam-Bending Method: V, Isotropic Rectangular Plates of Cement Paste (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Ceramic Society 87 (2004), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Beam bending is an excellent method for measuring low permeabilities (≤10−18 m2) in homogeneous materials, because it is fast, requires no high pressure, and provides a concurrent measurement of the modulus of the material. The method was previously analyzed and substantiated for cylindrical or square beams. Recently, the analysis was extended to include isotropic and transversely isotropic rectangular beams. In this paper, the analysis is applied to measurements performed on cement paste, and it is shown that the solution for isotropic rectangular beams accounts for changes in the hydrodynamic behavior caused by changing the aspect ratio of the sample. The permeability and elastic modulus results are verified through comparison to previous measurements on cylindrical beams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2004.tb06342.x
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  • 3
    Electronic Resource
    Electronic Resource
    Measuring Permeability of Rigid Materials by a Beam-Bending Method: I, Theory (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When a saturated porous material is deformed, pressure gradients are created in the liquid, and the liquid flows within the pores to equilibrate the pressure. This phenomenon can be exploited to measure permeability: A rod of saturated porous material is instantaneously bent by a fixed amount, and the force required to sustain the deflection is measured as a function of time. The force decreases as the liquid flows through the pore network, and the rate of decrease depends on the permeability. This technique has been applied successfully to determine the permeability of gels, as well as their viscoelastic properties; in this paper the method is extended to ceramic materials, such as porous glass and cement paste. The theory has been modified to take account of the compressibility of the solid and liquid phases (whereas, those factors are negligible for gels). Analyses are presented for constant deflection, constant rate of deflection, and sinusoidal oscillation, where the solid phase is either purely elastic or viscoelastic, and the beam is either cylindrical or square. Experimental tests on Vycor® glass and cement paste will be presented in companion papers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01540.x
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal Expansion Kinetics: Method to Measure Permeability of Cementitious Materials: I, Theory (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When a porous material that is saturated with liquid is heated, the liquid typically expands much more than the solid phase; if the permeability is high, then the liquid flows out of the pores as it expands. However, if the permeability is low, then the liquid may not be able to escape, so it expands within the pores and contributes to the dilatation of the body; as the liquid drains from the pores, the body contracts to the dimension dictated by the thermal expansion coefficient of the solid phase. In the low-permeability case, by analyzing the kinetics of dilatation during a change in temperature, it is possible to extract the permeability. This technique, which previously has been successfully applied to gels, is also applicable to conventional ceramics, such as porous glass, sintered ceramics, cement, and concrete. However, for these rigid materials, the analysis must be modified to take account of the finite compressibility of the liquid. In this article, the thermal expansion kinetics are analyzed for cylindrical and platelike samples. The results are applied to cement paste in a companion paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01627.x
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  • 5
    Electronic Resource
    Electronic Resource
    Measuring Permeability of Rigid Materials by a Beam-Bending Method: III, Cement Paste (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The evolution of permeability and elastic modulus for Type III portland cement pastes with water/cement ratios varying from 0.4 to 0.6 were measured using a beam-bending method. Young's modulus was independently verified by measuring the ultrasonic pulse velocity. The permeability ranged over 2 orders of magnitude, depending on the water/cement ratio and the age of the samples. The advantage of the beam-bending method is that the permeability results are obtained in a few minutes to a few hours, whereas conventional techniques take hours or days to measure permeability of this order of magnitude. More importantly, there is no need to maintain high pressure during the measurement period, so leaks are not a problem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00309.x
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal Expansion Kinetics: Method to Measure Permeability of Cementitious Materials: II, Application to Hardened Cement Pastes (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new approach to determine the permeability of cementitious materials is presented in this paper. The method involves the measurement of the thermal dilatation of thin slabs of saturated cement paste. On heating and subsequent isothermal holding, the sample first expands, then gradually contracts over time. The paste is treated as a porous solid with low permeability in which the initial expansion is partly due to the liquid expanding within the pores, putting both solid and liquid under stress. The time-dependent contraction is due to the liquid flowing out of the pores to restore the pressure to equilibrium. By analyzing the kinetics of the thermal expansion and contraction, the liquid permeability of the porous solid can be calculated. The theoretical analysis (presented in a previous paper) is applied to determine the water permeability coefficients of selected cement pastes modified with silica fume and made with different water/solid ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00666.x
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  • 7
    Electronic Resource
    Electronic Resource
    Measuring Permeability of Rigid Materials by a Beam-Bending Method: II, Porous Glass (2000)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It has been shown in a companion paper that the permeability of a porous body can be found from a three-point bending experiment. When the sample is bent, a pressure gradient is created in the liquid within the pores; as the liquid flows in response to the gradient, the force that must be applied to the rod to sustain a fixed deflection decreases with time. By fitting the force decay curve to the predicted shape, the permeability is obtained, along with the elastic modulus. In this paper, that theory is tested using porous Vycor® glass saturated with various solvents, including several normal alcohols, water, and glycerol. The shape of the measured decay is in excellent agreement with the prediction. Consistent with observations of previous workers, we find that the permeability is influenced by the size of the solvent molecule; by assuming that the pore surfaces are covered with a monolayer of immobile solvent, the observed variation can be explained. The advantage of the beam-bending method is that the results are obtained in a few minutes; moreover, there is no problem with leaks or need for high pressures, as there is in conventional measurements of low permeabilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2000.tb01541.x
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  • 8
    Electronic Resource
    Electronic Resource
    Silicate Consolidants for Stone (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 391 (Oct. 2008), p. 1-25 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Consolidants are sols or solutions that are used to restore the strength of weathered stone.The liquids are drawn into the pores of stone by capillary suction, then they harden by gelationand/or drying. In this chapter, we discuss the requirements that such a material must fulfill, anddemonstrate the effectiveness of consolidants based on alkoxysilanes and alkylalkoxysilanes
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/57/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.391.1.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Measuring permeability by the thermal expansion method for rigid or highly permeable gels (1994)
    Springer
    Journal of sol gel science and technology 3 (1994), S. 31-40 
    Details
    ISSN: 1573-4846
    Keywords: permeability ; thermal expansion ; octanol ; decanol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The permeability (D) of a gel can be determined by analysis of its thermal expansion kinetics: as the gel is heated, the expanding liquid stretches the solid network like a spring; during an isothermal hold, the liquid drains out and the gel returns to its initial dimensions at a rate that depends on D and the elastic modulus of the network. However, if the network is too rigid or D is too high, the dilatation of the network may be too small to measure easily. The measured expansion increases with the viscosity of the pore liquid, so D is easier to measure after the gel is rinsed in a higher alcohol. For example, a thermally aged silica gel that shows no measurable expansion in ethanol exhibits a large thermal strain after the pore liquid is changed to 1-octanol. It is important to demonstrate that the same permeability is obtained regardless of the liquid employed (i.e., that flow in the small pores of the gel does not give rise to liquid-specific effects), so we examine the thermal expansion of a silica gel rinsed successively in ethanol, 1-octanol, and 1-decanol; the gel is compliant enough so that D is measurable in all these liquids. The permeability is found to be the same, but the expansion is much more easily measured for the more viscous alcohols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00490146
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  • 10
    Electronic Resource
    Electronic Resource
    Stress in aerogel during depressurization of autoclave: I. theory (1994)
    Springer
    Journal of sol gel science and technology 3 (1994), S. 127-139 
    Details
    ISSN: 1573-4846
    Keywords: aerogel ; stress ; drying ; permeability ; supercritical drying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aerogels are made by heating a wet gel in an autoclave to a temperature and pressure exceeding the critical point of the solvent, then releasing the pressure. This avoids the capillary stresses that usually cause cracking during drying (since there is no liquid/vapor meniscus above the critical point). However, if the pressure is released too quickly, the fluid inside the gel does not have time to flow out of the network, so it expands within the gel and can cause cracking. The pressure in the pores of the network has been analyzed, so that the stress in the gel can be calculated as a function of the rate of pressure release. Quantitative comparisons of the measured strength of the gel with the calculated stresses (for depressurization rates known to cause cracking) are presented in a companion paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00486719
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