Estimation of structural element sizes in sand and compacted blocks of ground calcium carbonate using a void network model (original) (raw)
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Measurement and Network Modeling of Liquid Permeation into Compacted Mineral Blocks
Journal of Colloid and Interface Science, 2000
A microbalance has been used to measure the rate of uptake of a wetting fluid, 1,3-propandiol, into a cube of compacted calcium carbonate. The cube had sides 12 mm long, with a wax band applied to the outer perpendicular edges of one basal plane to prevent external surface uptake, and the liquid was applied in a highly controlled manner at this single face only. The percolation characteristics of an identical sample were measured by mercury porosimetry. A three-dimensional void structure was generated with the same percolation characteristics using a software package called "Pore-Cor." The wetting of 1,3-propandiol into this model structure was then calculated using an extended Lucas-Washburn equation, developed by Bosanquet, which includes viscous, inertial, and capillary force effects. Neither the experimental nor the simulated wetting can be explained in terms of an "hydraulic stream tube" or "effective hydraulic radius" model. A mathematical function is presented which compensates for the differences in the boundary conditions between the simulation and the experiment. The wetting is found to be initially slowed by inertial flow, then speeded up to a t 0.8 dependence by the connectivity of the three-dimensional void network. The effect of the inertial flow is most pronounced for larger pores. C 2000 Academic Press
Transport in Porous Media, 2018
This work addresses two continuing fallacies in the interpretation of percolation characteristics of porous solids. The first is that the first derivative (slope) of the intrusion characteristic of the non-wetting fluid or drainage characteristic of the wetting fluid corresponds to the void size distribution, and the second is that the sizes of all voids can be measured. The fallacies are illustrated with the aid of the PoreXpert ® inverse modelling package. A new void analysis method is then described, which is an add-on to the inverse modelling package and addresses the second fallacy. It is applied to three widely contrasting and challenging porous media. The first comprises two fine-grain graphites for use in the next-generation nuclear reactors. Their larger void sizes were measured by mercury intrusion, and the smallest by using a grand canonical Monte Carlo interpretation of surface area measurement down to nanometre scale. The second application is to the mercury intrusion of a series of mixtures of ground calcium carbonate with powdered microporous calcium carbonate known as functionalised calcium carbonate (FCC). The third is the water retention/drainage characteristic of a soil sample which undergoes naturally occurring hydrophilic/hydrophobic transitions. The first-derivative approximation is shown to be reasonable in the interpretation of the mercury intrusion porosimetry of the two graphites, which differ only at low mercury intrusion
Sedimentation Engineering
This study aims to evaluate the constitutive equations for pressure on the solids and permeability of porous media consisting of calcium carbonates with different degrees of polydispersity. The constitutive relations are intended to assist in the modeling and simulation of sedimentation operations when theory of mixtures of continuum mechanics is used. In this work, a porous media was obtained after the complete sedimentation of aqueous suspensions of calcium carbonate. The gamma-ray attenuation technique was used, which allowed the realization of measurements of the distribution of porosity in the sediment before and after liquid percolation. The experimental results showed a considerable degree of compressibility for calcium carbonates, and significant deviations from the Kozeny-Carman correlation when the carbonates were used to express permeability. Therefore, the use of the incompressibility hypothesis for this solid in equations that model sedimentation may not be a viable consideration. Overall, this study provides relevant information about sedimentation for situations in which the formation of compressible sediments occurs.
Particle Morphology Effect on the Soil Pore Structure
Lecture Notes in Civil Engineering
The soil fabric can be expressed as a network model. Granular media voids connectivity and constriction size distribution may lead to movement of air, fluids, and solids in the soil, and therefore affect the chemical, physical and mechanical properties of soils. Understanding the soil voids areas and their interconnection might be helpful in understanding different phenomena such as transport in porous media, water retention, fluid flow in the soil, soil contamination, internal erosion, suffusion, and filtration. In addition, specifying the soil voids interconnectivity can help researchers and practical engineers to provide the best rehabilitation and remediation approaches. The pore network was investigated in the current study, assuming the soil particles to be similar to discrete spheres and particles with different shapes. Also, based on the modelling techniques, the profiles of pore connectivity and constriction size distribution were assessed.
CATENA, 2012
(AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process-such as editing, corrections, structural formatting, and other quality control mechanisms-may not be reflected in this version of the text. The definitive version of the text was subsequently published in Catena, 95, 169-176.
Clays and Clay Minerals, 2009
The size, shape, and continuity of pores in mineral solids greatly influence the behavior of percolating liquids and solids in porous media, which has significant practical environmental implications. In order to expand understanding of these properties in soil minerals, the present study was undertaken to analyze the pore characteristics of bentonite, illite, and kaolinite in the forms of powder and aggregates of different dimensions, combining water-vapor desorption and mercury-intrusion techniques. Different granulometric fractions of milled quartz glass were also studied. With increasing aggregate size of the minerals, larger pore volumes (up to 25%), smaller surface areas (down to 15%), larger average radii (up to 15%), and smaller fractal dimensions (down to 6%) were measured using water-vapor adsorptiondesorption data. The differences were smallest for bentonite, possibly due to the smallest particle size of this mineral and/or to its very large water-vapor adsorption capacity. The degree of water-vapor adsorption on quartz was too small to rely on the data obtained.
Intra granular porosity of mineral powders: modeling and experimentation
Materials and Structures, 2021
Recycled concrete aggregate (RCA) possess high water absorption, due to the porosity of the attached hardened cement paste they contain. Fine particles of RCA are composed of larger amounts of hardened cement paste, which makes their valorization even more difficult in concrete or mortar. One way to valorize these fine particles could be to use them as mineral addition, however their water absorption coefficient has to be determined, which is tricky for powders. The objective of this work is to estimate the remaining intra granular porosity of a ground powder using two different original approaches. The first modelling approach considers that the porous monolith material is composed of series of pores with characteristic volumes. A pore is considered opened due to grinding if it is cut by the surface of the particle and if its size is larger than the smallest inter granular pore. The remaining porosity after grinding is computed from the pore size distribution of the monolith material and the particle size distribution of the powder. The second experimental approach is based on mercury intrusion porosimetry tests performed on the powder. The separation between inter and intra granular porosity allows the estimation of the powder's remaining porosity. The obtained results show a good agreement between the two approaches in the case of disconnected pores. However, in the case of connected porosity, the experimental approach over estimates the amount of inter-granular porosity.
Journal of Geophysical Research: Solid Earth, 2013
1] Local porosity theory in combination with percolation theory was applied to shale microstructures that were reconstructed on the basis of focused ion beam nanotomography and scanning transmission electron microscopy. This allowed characterizing pore microstructures in Opalinus clay with length scales on the order of tens of microns. In a sample from the sandy facies (with low clay content), the fraction of "larger" pores f(radii~> 15 nm) = 0.076 is substantially higher than that in the shaley facies (with a higher clay content), where f(radii~> 15 nm) = 0.015. The resolved porosity possesses a certain degree of homogeneity, and the representative volume element (RVE) of porosity can be determined in terms of a given relative error on porosity. For example, if we accept a relative error of 10%, the RVE is on the scale of a few hundreds of microns. Both pore microstructures from sandy and shaley facies show anisotropic characteristics with respect to connectivity and percolation threshold. Using finite scaling, we found percolation thresholds with critical porosities f c,b = 0.04-0.12 parallel to bedding and f c,perp =0.11-0.19 perpendicular to bedding. The resolved porosity of the sandy facies (low clay content) is close to the percolation threshold, whereas the porosity of the shaley facies (high clay content) is below the percolation threshold. The porosity in carbonate layers is around f = 0.027, and the pore size is substantially larger when compared to the pores in the clay matrix. In the analyzed sample, pores in carbonate layers are poorly connected.