Bibliography - J. J. Valenza II

1. Scherer, George, J. J. Valenza II, and G. Simmons, 2007: New Methods to Measure Liquid Permeability in Porous Materials. Cement and Concrete Research, 37(3), doi:10.1016/j.cemconres.2006.09.020 386-397
   [ Abstract ]

   Several novel methods have recently been proposed for rapid measurement of the liquid permeability of saturated cement paste, mortar and concrete. The relative merits of the techniques are discussed, and some recent results obtained on pastes and mortars are presented. The low permeabilities seen in cement paste are inconsistent with the pore size distributions measured following drying, indicating that the pore structure is significantly changed by drying.

2. Scherer, George, and J. J. Valenza II, 2005: Mechanisms of Frost Damage. Materials Science of Concrete, American Ceramics Society, VII(ISBN:978-1-57498-210), 209-246
   [ Abstract ]

   The mechanisms responsible for damage from internal freezing and salt scaling are reviewed. The primary cause of internal damage is crystallization pressure, and the role of the air voids is to provide sites for nucleation of macroscopic ice. The thermodynamics of the stress development are reviewed, and the predicted pressures are shown to be in quantitative accord with measured contraction of frozen bodies (including porous glass and cement paste). The origin of salt scaling damage is less clear. We examine two mechanisms that seem to account for most of the experimental observations: the bimaterial effect (i.e., thermal expansion mismatch between ice and cement paste) and salt-induced swelling. A sensitive experiment, in which a layer of water is frozen on top of a thin plate of cement paste and the deflection of the plate is measured, reveals the large stresses produced by these mechanisms. Cracking of the ice layer is promoted by brine pockets, and this may account for the pessimum concentration for scaling damage. Salt-induced swelling, which seems to result from a combination of crystallization pressure and ion exchange, also contributes to the superficial stresses and may exacerbate scaling.

3. Valenza II, J. J., and George Scherer, 2005: Evidence of anomalous thermal expansion of water in cement paste. Cement and Concrete Research, 35(1), doi:10.1016/j.cemconres.2004.08.022 57-66
   [ Abstract ]

   A comparative study of permeability measurement by thermopermeametry (TPA) and beam bending was performed on cement paste. To bring the two measurements into agreement, it is necessary to recognize that the pore solution has a thermal expansion coefficient about one and a half times that of bulk liquid and to account for viscoelastic stress relaxation during TPA experiments. The anomalous thermal expansion is not accounted for by the presence of ions in the cement paste pore solution.

4. Valenza II, J. J., and George Scherer, 2004: Measuring Permeability of Rigid Materials by a Beam-Bending Method: V. Isotropic Rectangular Plates of Cement Paste. Journal of the American Ceramic Society, http://www3.interscience.wiley.com/cgi-bin/fulltext/118743577/PDFSTART, 87(10), 1927-1931
   [ Abstract ]

   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.

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