Angular Grain Research Articles

Studies on mechanical properties of concrete containing waste glass aggregate

Quantities of waste glass have been on the rise in recent years due to an increase in industrialization and the rapid improvement in the standard of living. Unfortunately, the majority of waste glass is not being recycled but rather abandoned, and is therefore the cause of certain serious problems such as the waste of natural resources and environmental pollution. For these reasons, this study has been conducted through basic experimental research in order to analyze the possibilities of recycling waste glasses (crushed waste glasses from Korea such as amber, emerald green, flint, and mixed glass) as fine aggregates for concrete. Test results of fresh concrete show that both slump and compacting factors are decreased due to angular grain shape and that air content is increased due to the involvement of numerous small-sized particles that are found in waste glasses. In addition the compressive, tensile and flexural strengths of concrete have been shown to decrease when the content of waste glass is increased. In conclusion, the results of this study indicate that emerald green waste glass when used below 30% in mixing concrete is practical along with usage of 10% SBR latex. In addition, the content of waste glasses below 30% is practical along with usage of a pertinent admixture that is necessary to obtain workability and air content.

Iridium anomalies and shocked quartz in a Late Archean spherule layer from the Pilbara craton: New evidence for a major asteroid impact at 2.63 Ga

A thin (1‐5 mm) spherule layer in ca. 2.63 Ga shale from the Jeerinah Formation (Pilbara craton, northwestern Australia) has been identified at two new localities. The layers have Ir concentrations as high as 15.5 ppb, significantly higher than the surrounding carbonaceous shale (,1.5 ppb). The sand-sized spherules display quench and devitrification textures and are interpreted as former silicate melt droplets that were replaced by K-feldspar, carbonate, and sulfide during diagenesis. In one spherule-layer sample, an angular quartz grain (;100 mm in size) with planar deformation features was found, which represents the oldest known shocked grain in distal ejecta by .2000 m.y. The survival of shocked quartz in ca. 2.63 Ga rocks, which have undergone multiple metamorphic events, suggests that their absence in other impact ejecta layers may not only be a question of preservation. The presence of shocked quartz and anomalously high Ir contents in a layer containing melt spherules provides compelling evidence for an extraterrestrial impact with a target area that was at least partly silicic, favoring a continental impact site. Estimates based on geochemical data suggest that the spherule layer comprises as much as 2‐3 wt% of a chondritic meteorite component. If proposed correlations with the Carawine (eastern Pilbara craton) and Monteville (South Africa) layers are correct, then the combined ejecta blanket represents fallout from a single major impact with an areal distribution of .32,000 km 2 , among the largest yet documented in the Precambrian rock record.

Mechanisms of Sand Production Through Horizontal Well Slots in Primary Production

Abstract Cold production in unconsolidated heavy oil reservoirs, where sand production is encouraged (CHOPS), has proven to be successful for vertical wells. However, the application of CHOPS to horizontal wells has been less profitable due mainly to excessive sand cleanout costs. Therefore, reducing sand cleanout costs by controlling sand production into horizontal wells while enhancing the surrounding permeability of the formation is an important factor in optimizing cold production from unconsolidated heavy oil reservoirs. This paper presents the results of an experimental investigation of the flow of oil and sand in the vicinity of a horizontal well under cold production. Specifically, the experiments physically simulated the flow of oil and sand into a slot in a horizontal well liner. The parameters studied include slot width and sand properties (morphology and grain size distribution). Experimental results suggest that sand production through horizontal well slots can be controlled, depending more on sand grain sorting than on grain morphology or average diameter. The sand cut had a tendency to be higher at the beginning of the sand production period and to decline with time. In most tests, the decline in sand cuts continued until no more sand was produced. Significant changes in the permeability and porosity were determined in the vicinity of the slot. The changes in the parameters were less significant away from the slot. The largest fractions of the sand (bigger than 500 µm) have an important role in arch/bridge formation. Introduction Cold production is a primary non-thermal process used in unconsolidated heavy oil reservoirs in Alberta and Saskatchewan, Canada. In this process, sand and oil are produced together in order to enhance oil recovery(1–3). A comprehensive review of cold production has been presented by Tremblay et al.(1). Hall and Harrisberger(4) found that arch stability was flow rate sensitive at low confining stress but independent of flow rate at high confining stress levels. They observed that angular sand without compaction did not form an arch. When a moderate compaction was applied, it could lead to a slightly stable arch. A better interlocking of the surface grains was the explanation for this result. For round sand, arching was not observed for a loose or dense pack at low loads. Yim et al.(5) observed that in addition to the flow rate, the arch stability was strongly dependent on the granulometry of the sand and on the size of the perforation. Larger perforations required larger grains to form stable arches. McCormack(6) conducted experimental work with spherical particles to determine the arching/bridging mechanism that influenced the performance of wire-wrapped sand screens. Selby and Farouq Ali(7) showed that sand production increased as the overburden pressure and the fluid flow rate were increased. They also found that spherical small grain sand packs can produce more sand than angular large grain sand packs. Cleary et al.(8) observed that the structure of an arch depended on the stress distribution in a sand pack. The cohesive force was shown to have an important role in arch stability when different hydrocarbons liquids were used.

W-Einkristallprüfung und -Bruchflächenuntersuchung mit Elektronenbeugung (ECP) am REM The Investigation of Tungsten Single Crystals and Their Fracture Surfaces by Electron Diffraction (ECP) in the SEM

The Electron Channelling Process carried out in the scanning electron microscope (SEM), and as set up as standard in most microscopes, is unfamiliar to most users and thus seldomly used. This article is intended to present an example of the use of the ECP-process in the SEM. An investigation was carried out on crystals of tungsten in order to establish whether their microstructure, as revealed using normal metallographical preparation techniques, was made up of sub-grain boundaries or major angular grain boundaries which cast doubt as to whether the material was indeed a single crystal

MORPHOLOGICAL PROPERTIES OF EOLIAN SAND GRAINS

Kuenen and Margolis recognized frosting on the quartz sand grains as the result of mechanical and chemical process that were active in the eolian environment. On the contrary, Cailleux, Ottoman and Kosugi recognized it as the result of wind abrasion. On the basis of Cailleux, Ottoman and Kosugi's view, the writer reports the results of some measurements of the quartz sand grains and discusses them in this paper. Approximately 82, 800 samples were collected from eight environments in Pleistocene and Holocene : offshore, foreshore, backshore, dunes I, II, III, inland dune, eolian sands beneath a black humus soils, and eolian sands of lower Pleistocene in western Japan and Antarctica. The length of quartz sand grains studied ranges from 0.35 to 0.71mm. Observations were made by the binocular microscope with canadabalsam on a green background. Magnification is x 60 for the 0.71mm grains, and x 75 for the 0.5 and 0.35mm grains. Among the quartz grains, four main types may be distinguished. 1) angular shiny grain (AS) 2) round shiny grain (RS) 3) semi dull grain (SD) 4) round dull grain (RD) The results obtained may be summarized as follows: 1) Prevailing sand grains of RD type are observed in the eolian sand beds. In contrast to the eolian sands, the beach sands contain a high percentage of AS and RS type sand grains. 2) In the Holocene eolian sands, dune III sands contain relatively high percentage of sand grains of RD type (17 to 66 per cent). On the other hand, in the dune I sands, the percentage of sand grains of RD type is as low as 1 to 19. This is shown Figure 2. 3) Correlation of the thickness (t) and the percentage of sand grains of RD type (A) of dune III sands is shown to be A=0.878t+13, 188. This is shown in Figure 3. 4) In Wright valley, Antarctica, the migrating eolian sands contain higher percentage (76 per cent) of sand grains of RD type than in Japan. 5) In the pleistocene eolian sands, Tanegashima D3 sand and Hojyo eolian sand beds contain a high percentage of the RD type sand grains. Its properties differ greatly from Holocene eolian sands.