Proportion Of Voids Research Articles

The possibility of reusing recycled aggregates in the production of hot mix asphalt

The use of aggregates resulting from destroying concrete as a substitute for natural aggregates in the production of hot mix asphalt for roads with high traffic loads reduces natural consumption and the amount of scattered waste. The study was conducted by designing the hot mix asphalt using the Marshall method with different proportions of recycled aggregate. The results showed an improvement in the stability, flow and indirect tensile tests of the aggregate compared to the conventional mixture. An increase in the recycle aggregate leads to an increase in the proportion of air voids, but it also leads to a decrease in the proportion of voids in the aggregate and asphalt-filled voids. The optimum bitumen content increases with the amount of recycled concrete. Recycled aggregate can be used as a substitute for natural aggregate in hot mix asphalt design successfully. The study found that increasing the percentage of recycled concrete (RCA) in hot bituminous mixtures led to an increase in air voids (VA) and a decrease in voids in mineral aggregates (VMA) and voids filled with asphalt (VFA). However, these percentages decreased with the increase in RCA due to the behavior of the recycled aggregates under load. The optimum bitumen content (OBC) also increased with the increase in RCA. The asphalt mixture's resistance to tensile stress increased with the increase in RCA up to 50% and at 25˚C and RCA 40˚C by up to 8%. The process of using recycled aggregates as an alternative to natural aggregates in hot bituminous mixtures is applicable up to a certain percentage.

Precision and accuracy of modal analysis methods for clastic deposits and rocks: A statistical and numerical modeling approach

Quantifying the proportions of certain components in rocks and deposits (modal analysis or componentry) is important in earth sciences. Relevant methods for cross-sections (two- dimensional exposures) of clastic rocks include point counts or line counts. The accuracy of these methods has been supposed to be good in the literature but not necessarily verified empirically. Natural materials are inappropriate for assessing accuracy because the true proportions of each component are unknown. The precision of modal analysis methods has traditionally been evaluated from statistical models (primarily the normal approximation to the binomial distribution) but again rarely verified in practice because it is also extremely difficult to obtain different slices through the same material at outcrop scale. Here we create a set of numerical models of red and blue spheres with different proportions and sizes and cut 60 slices through the models, on which we perform point counts and line counts. We show that both of these methods are indeed able to retrieve the correct volumetric proportions of components, on average, when enough fragments are counted or intersected. As already known, precision is controlled by component abundance and the number of points counted or clasts intersected. However, we show that other important factors include differences between slices, which are relevant for our unequal-size models, and the proportion of voids, matrix, and/or cement in the rock. We present empirical precision charts for clast counts and line counts based on our models and make recommendations for future field studies.

Influence of intermolecular interactions and crystal structure on desolvation mechanisms of solvates

The desolvation processes of the solvates were systematically investigated by various analytical techniques and were analyzed based on the intermolecular interactions, molecular networks, void types, proportion of voids and packing patterns.

Apical filling characteristics of carrier-based techniques vs. single cone technique in curved root canals.

In this in vitro study, we assessed filling characteristics (adaptation, homogeneity, sealer percentage, position of the carrier) of warm and cold obturation methods in curved root canals. A reciprocating method was used to prepare 90 curved roots (25° average curvature) to an apical size of 25.08. They were then obturated with either (A) Guttafusion (VDW, Munich, Germany), (B) Thermafil (Maillefer, Ballaigues, Switzerland) or (C) single cone technique using 25.08 gutta-percha (VDW) and sealer (2Seal easymix) (n=30 each group). Five sections in 1-mm steps were obtained from each root, beginning 1mm short of the apex. The percentage of voids in contact with root canal walls (PVO), the proportion of voids per area (PVA) and the percentage of sealer per area (PSA) were measured. Little to no differences between Guttafusion and Thermafil were seen in curved root canals with respect to adaptation and homogeneity in the apical region. Both methods showed significantly better adaptation and homogeneity than the single cone technique. The proportion of sealer was significantly greater when roots were obturated with Guttafusion than with Thermafil, but both warm obturation techniques had significantly smaller sealer areas than the single cone technique. Compared to the single cone technique, a more favourable root canal filling with less sealer could be expected from both warm obturation techniques in curved root canals. The easier-to-handle Guttafusion leads to comparable results as Thermafil in curved root canals.

Micromorphological characteristics reflecting soil-forming processes during Albeluvisol development in S Norway .

This paper presents micromorphological observations of the only two Albeluvisol chronosequences to have been reported in the international literature so far. These observations are combined with existing profile morphological and soil chemical data in order to identify the major processes involved in the development of Albeluvisols. The study area is located in the counties Vestfold and Østfold on the western and eastern sides of the Oslofjord, S Norway. The region is characterized by continuous glacio-isostatic uplift over the Holocene, and hence the age of the land surface increases continuously from the beach towards the higher elevations. Twelve soil pits in loamy marine sediments were investigated, six each in Vestfold and Østfold; in addition, three samples of fresh sediments were taken from the shoreline. Results of this study suggest that as soon as the land surface is raised above sea level, drainage of the coarse pores and aeration of the upper part of the young soils leads to five major processes: i) development of deep desiccation cracks, forming a polygonal pattern; ii) compaction, taking place as soon as the land surface reaches an elevation above sea level that leads to drainage of the coarse pores; iii) pyrite oxidation, releasing sulfuric acid; iv) rapid decarbonatization of the originally calcareous sediments through carbonate dissolution by acids from pyrite and iron oxidation; v) precipitation of iron hypocoatings and coatings in the capillary fringe. The next morphological change, also taking place within less than 2.1 ka, is horizon differentiation into Ah, Eg and Btg horizons due to the limited water permeability of the fine-textured sediments. Eg horizons, for example, become lighter in colour with time. The process leading to the next morphological change in the soil profiles is clay illuviation, which is also already present in the 2.1 ka-old soil. Soil pH in the upper part of the E horizon of this soil is already too low for significant clay mobilization. Clay illuviation is still active in all soils studied, but the upper boundary of the clay mobilization zone is at 20-50 cm depth. Progressive clay illuviation is recorded by the increasing thickness of clay coatings and proportion of voids having clay coatings. Clay mobilization and iron co-eluviation in the upper parts of the Eg horizons cease within less than 2.1 ka, whereas weathering and formation of clay minerals and iron oxides continue, leading to formation of a BE horizon in the upper part of the Eg horizon. Albeluvic tongues start to form after 4.6-6.2 ka. They develop preferably along the desiccation cracks. Albeluvic material is washed into the cracks, and enhanced leaching of bases and clay eluviation takes place in the cracks. As both processes proceed, the albeluvic tongues get longer and wider. Clayey intercalations occur in the Stagnic Albeluvisols of the sequence, and the following concept is suggested to explain their genesis: after snow melt or a rainy period infiltrating water arrives at the lower end of an albeluvic tongue, the tongue fills up with water, and perched water also accumulates on top of the dense Btg horizon. Water, carrying suspended clay, penetrates under pressure from the tongue into the Btg horizon, where additional clay is mobilized. The clay settles when the velocity of the water decreases, forming clayey intercalations in the dense matrix of the Btg horizon.

3D micro‐CT analysis of the interface voids associated with Thermafil root fillings used with AH Plus or a flowable MTA sealer

To investigate nondestructively the percentage of 3D voids and marginal gaps in a pre-defined interface volume of interest (VOI) within root fillings produced by Thermafil Obturators with either a hydrophobic epoxy-resin-based sealer (AH Plus) or a hydrophilic flowable calcium-silicate sealer [mineral trioxide aggregate (MTA) Flow]. Sixteen single root canals from extracted premolar teeth were prepared with ProTaper rotary instruments, randomly allocated into two groups (n = 8) and filled with size 30 Thermafil Obturators in association with AH Plus or MTA Flow sealers. The filled roots were stored at 37 °C in 5 mL of Hank's balanced salt solution (HBSS) used to represent body fluids and scanned after 7 days and 6 months using a high-resolution micro-CT. From each root, images of 3000 sections were analysed in 3D and binarized using a high-resolution micro-CT (4-μ resolution). The 3D distribution of voids (porosity and marginal gaps) at the gutta-percha-sealer-dentine interface was detected through a threshold grey level and expressed as percentage of the 40-μ-thick pre-defined interface VOI (20 μ of interface dentine and 20 μ of gutta-percha/sealer). A method of analysis based on the root canal segmentation was used, and coronal, middle and apical thirds considered separately. The percentage of 3D void volume was compared statistically using one-way anova (significance for P < 0.05). Environmental Scanning Electron Microscope with Energy Dispersive X-ray (ESEM-EDX) analysis was performed on the surface of both sealers after soaking in HBSS. Micro-CT detected gaps at the dentine-sealer interface in both groups. Void volumes wider than 10.21 μm(3) with 1.35 μm diameter were detected. Cul-de-sac-type voids (blind pores) and through-and-through voids (continuous pores) were discriminated. The apical thirds had a significantly lower 3D void volume (P < 0.05) than the middle and coronal thirds. The 3D void volume reduced significantly (P < 0.05) over time. ESEM-EDX analysis revealed that MTA Flow sealer created a dense apatite layer after 7 days of immersion in HBSS, whilst only sparse calcium phosphate deposits were detected on AH Plus even after 28 days. Micro-CT proved to be a powerful nondestructive 3D analysis tool for visualizing the porous internal microstructure of dental/endodontic materials at the interface with dentine. The proportion of voids was least in the apical third of root canals. Voids reduced over time in the presence of simulated body fluid.

Compressibility of tyres for use in landfill drainage systems

Whole or shredded scrap tyres are sometimes proposed as an alternative to conventional aggregates in landfill drainage systems. Landfill basal drainage systems are, however, subjected to large overburden stresses from the overlying waste, which may compress a tyre drainage layer reducing its porosity and hence its effectiveness. Previous work has indicated that tyre drainage layers will remain effective under high stresses, but tests have in the main been restricted to small (&lt;100 mm) shred sizes. The use of coarser shreds or even whole tyres for landfill drainage systems may be advantageous as they are more economical to produce and may be less prone to clogging than smaller shreds. In this paper, the results of largescale (2 m sample diameter) tests to investigate the compressibility of 50, 200 and 450 mm nominal-size tyre shreds are compared with data from the literature for smaller-size shreds and whole tyres. Tests were carried out at vertical stresses up to 600 kPa, representing landfill depths of up to about 60 m. Generally whole tyres and larger-size segments compress more in overall volume terms on initial loading than smaller size shreds. At vertical stresses greater than about 80 kPa, however, the differences on a graph of dry density or porosity plotted against vertical stress are much smaller. The proportion of voids that are not free-draining decreases with compression for whole tyres, as cup-like structures capable of retaining water flatten out. For tyre chips, the proportion of non-drainable voids increases with compression, suggesting that flow pathways are being lost. The dependence of the compressive behaviour of tyres and tyre chips on the particle shape is discussed, and the need for a more detailed and rigorous way of characterising particle size and shape is highlighted.

The Influence of Argon Pressure on the Properties of Sputtered Molybdenum Disulfide films

Sputtered molybdenum disulfide films having various density, internal stress, morphology, and impurities were produced by varying argon pressure, and the properties were investigated. The main results obtained are summarized as follows : A decrease of argon pressure brings the increase of the bulk density, compressive stress, and argon contents in films. However, the weight of films and stoichiometry are scarcely influenced by the argon pressure. The decrease of bulk density correlates with the proportion of voids in films. An increase of argon pressure brings the increase of the deposition rate, true density, and oxygen contents in films. The occurrence of compressive stresses and increase of true density correlate with the presence of entrapped argon in films. At least in the argon pressure range of 1.7 to 4 Pa, films with preferential orientation were obtained.

Gibbs ensemble simulation of symmetric mixtures composed by the homopolymers AA, BB and their common block copolymer AB

A Gibbs ensemble algorithm implemented previously for mixtures of homopolymers and copolymers in a cubic lattice with coordination number z=26 is now used to characterize the complete phase separation diagram of the ternary mixtures formed by AA and BB homopolymers and their common symmetric diblock copolymer AB, all chains of the same length. We consider two alternative types of systems with repulsions between neighboring A and B units or with attractions between A and A or B and B neighboring units. A certain proportion of voids is included in both cases. The 3-phase region of the diagram is obtained by using a 3-box algorithm that has not been previously employed for polymer mixtures. The 3-phase region is composed of two homopolymer-rich asymmetric phases, each one mainly composed of a different homopolymer component together with a small proportion of copolymer. These two phases are in equilibrium with a third phase rich in copolymer. The 3-phase region connects smoothly with the 2-phase region covered by our 2-box simulations reported earlier for low copolymer composition. Similarly, it also connects with two asymmetric 2-phase regions characterized now through 2-box simulations performed with a low initial proportion of one of the homopolymer components. The data obtained for the systems with repulsions are in agreement with earlier single box Monte Carlo estimations for ternary mixtures with a symmetric homopolymer composition. They show a non-clearly structured copolymer-rich phase with a substantial amount of homopolymer, while the presence of copolymer in the AA or BB enriched phases is small. The systems with attractions, however, exhibit important differences with respect to this picture, due to a more specific role of the voids. Some differences with respect to the mean-field theory predictions are also discussed.

Sequence-dependent clustering of parts and machines: A Fuzzy ART neural network approach

This study addresses the problem of identifying families of parts having a similar sequence of operations. This is a prerequisite for the implementation of cellular manufacturing, group technology, just-in-time manufacturing systems, and for streamlining material flows in general. A pattern recognition approach based on artificial neural networks is proposed, and it is shown that the Fuzzy ART neural network can be effectively utilized for this application. First, a representation scheme for operation sequences is developed, followed by an illustrative example. A more comprehensive experimental verification, based on the mixture-model approach is then performed to evaluate its performance. The experimental factors include size of the part-machine matrix, proportion of voids, proportion of exceptional elements, and vigilance threshold. It is shown that this neural network is effective in identifying good clustering solutions, consistently and with relatively fast execution times.

The Effect of Gravitational Compaction on the Structure of Sedimentary Rocks: A Discussion

Some of the conclusions in Hedberg's valuable paper on the effect of the compacting of clay rocks upon the structure of strata overlying buried hills seem to be more sweeping than the data warrant. Hedberg's average depth-porosity curve is based upon assumptions which greatly affect its accuracy. The present writer points out that the available data indicate that the void ratio of shale (the relative proportion of voids and solids) varies inversely as the depth of burial. This empirical relation is but a slight modification of a theory proposed by Sorby, it is similar to van der Waal's (gas volume) equation, and it seems to lead to acceptable geologic conclusions. Hedberg showed that by his average curve the present writer's suggested explanation of an anticline in western Kansas was improbable. However, by the modification of Sorby's theory, this explanation appears quantitatively possible. Even granting that the two methods of computing structure are equally logical, the large discrepancy between the results demonstrates that Hedberg's method is not sufficiently accurate for use as a quantitative test. Although several of Hedberg's other conclusions seem questionable, it is desirable to emphasize the fact that his paper opens up interesting vistas upon many fields of geologic study.