Study of the Behaviour of Senegalese Ballast Materials during Compaction with the C-Mould: Case of Bandia Limestone and Diack Basalt

2020 ◽  
Vol 831 ◽  
pp. 81-86
Author(s):  
Sow Libasse
Keyword(s):  
Grain Size ◽  
Fine Particles ◽  
Large Diameter ◽  
Railway Ballast ◽  
Effect Of Water ◽  
The Poor ◽  
Initial Diameter ◽  
Compaction Behaviour ◽  
Repeated Loads

Work presented in this article focuses on the study of the behaviour of materials from Senegalese quarries during compaction. These are Bandia Limestone (Sindia, Thiès Region) and Diack Basalt (Ngoundiane, Thiès Region). The grain size studied is 25/50 mm as for any material studied for use as railway ballast. The Proctor C-Mould for compacting large diameter materials was made for the occasion. With γdmax = 2.142 g/cm3 and WOPM = 5.3%, the compaction results clearly show the poor behaviour of the limestone under the effect of repeated loads and water. It shows a reduction in fine elements of the aggregates of initial diameter 25/50, as well as a significant cohesion under the effect of water with the formation of a muddy paste. The compaction references that characterize Diack Basalt are: γdmax = 2.15 g/cm3 and WOPM = 0.37%. Diack Basalt's compaction behaviour shows good performance. It does not break down into fine particles and the settling observed during compaction is similar to just tightening the grains and then stabilizing the material.

scholarly journals Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ran Yuan ◽  
Dan Ma ◽  
Hongwei Zhang
Keyword(s):  
Weight Loss ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Water Flow ◽  
Fine Particles ◽  
Flow Characteristics ◽  
Test System ◽  
Chemical Components ◽  
Gangue Mineral

A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss); meanwhile, a sample with more weight of size (0–2.5 mm) has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.

Uniformity of Grain Coarsening in Submicron Grained Al-Sc Alloy Containing Local Variations in Texture

2005 ◽  
Vol 495-497 ◽  
pp. 609-614
Author(s):  
Michael Ferry
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Fine Particles ◽  
Volume Fraction ◽  
Marked Change ◽  
Grain Coarsening ◽  
Large Volume Fraction ◽  
Orientation Gradient ◽  
Distribution Boundary

The effect of fine particles on the uniformity of grain coarsening in a submicron grained Al-Sc alloy containing significant local variations in texture has been investigated using high resolution EBSD. The alloy was processed by severe plastic deformation and low temperature ageing to generate a fine-grained (0.8 µm diameter) microstructure containing either a dispersion of nanosized Al3Sc particles or a particle-free matrix. The initial processing generated a uniform grain size distribution, but the distribution of grain orientations was inhomogeneous with the microstructure containing colonies of grains consisting predominantly of either HAGBs or LAGBs with the latter possessing orientation gradients of up to 10 o/µm. Despite the marked differences in boundary character between these regions, the alloy undergoes slow and uniform grain coarsening during annealing at temperatures up to 500 oC with no marked change in the grain size distribution, boundary distribution and texture. A model of grain coarsening that takes into account the influence of fine particles on the kinetics of grain growth within an orientation gradient is outlined. The model predicts that a large volume fraction of fine particles (large f/r-value) tends to homogenize the overall rate of grain coarsening despite the presence of orientation gradients in the microstructure.

scholarly journals Comparison of physical and mechanical properties of mining waste with a grain size up to 2 mm reinforced with cement CEM I and CEM III

2019 ◽  
Vol 106 ◽  
pp. 01023
Author(s):  
Justyna Morman-Wątor
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Fine Particles ◽  
Physical And Mechanical Properties ◽  
Mining Waste ◽  
Soil Testing ◽  
Mechanical Parameters ◽  
Freeze Resistance

The article presents the results of tests for mining waste mixtures - cement. The addition of cement was aimed at limiting the leaching of fine particles and improving physical and mechanical parameters. The studies used cement CEM I 42.5 R and CEM III/ A 42.5N - LH / HSR / NA and plasticizing sealant. The paper presents the results of freeze resistance, swelling tests, pH of water leachate and oedometer soil testing.

Research on Fuel Migration Phenomenon in the Sintering Process

2013 ◽  
Vol 634-638 ◽  
pp. 857-863
Author(s):  
Ya Ping Mo ◽  
De Qing Zhu ◽  
Jun Li
Keyword(s):  
Grain Size ◽  
Solid Fuel ◽  
Fine Particles ◽  
Vertical Direction ◽  
Size Composition ◽  
Fuel Particle ◽  
Sintering Process ◽  
Material Layer ◽  
Flow Through

In this paper, we use the research methods of sintering cup.On the basis of the determination of solid fuel particle size composition and the distribution in the mixture. During the sintering process, respectively, 5min, 10min, 15min, 20min interrupt the test, by dectecting the distribution of solid fuel in the mixture to study the migration phenomenon of solid fuel during the sintering process. The results showed that: during the sintering process, the main migration of the fuel is the migration of fine particles, including the fuel migration of 0.25-0.5mm grain size, part of the 0.5-1mm grain size and a small amount of-0.25mm grain size,but most of the fuel migrated will be re-adsorbed, about 0.11% of the fuel with the air flow through the material layer, the migration of fuel to ease the state of segregation in the vertical direction along the material layer, so that cause actual participation in the combustion of the fuel content in line along the height direction of the material layer.

Evaluation of Austenite Grains Growth in High Nb and Low Nb HSLA Steel

2020 ◽  
Vol 1000 ◽  
pp. 404-411
Author(s):  
Eddy S. Siradj
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Oil And Gas ◽  
Hsla Steel ◽  
Large Diameter ◽  
Low Carbon ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Reheating Process ◽  
Austenite Grain Growth

This study was presented due to the increasing demand of High Strength Low Alloy (HSLA) steel, such as demand for thinner-walled and large diameter pipes in oil and gas industries. In order to meet the imposed economic restrictions, the high standard of all kinds of steel properties is required and can be achieved by controlling the steel microstructure. The austenite grain size influences the microstructure and properties of steel significantly, in which fine austenite grain size leads to higher strength, better ductility, and higher toughness. Studying the behavior of steel grain growth during the reheating process is still being a fascinating subject. P.R. Rios and D Zollner [1] mentioned that grain growth is the most important unresolved issue that has been a topic of research for many years. In this research, the behavior of austenite grain growth at a high niobium-low carbon (High Nb-low C) and low Nb-high C HSLA steel was evaluated, and the result was compared with other investigation. The results found that the austenite grain growth at high Nb-high C steel was slower than the growth at a low Nb-low C steel. The activation energy of austenite grain growth and both constant A and exponent n ware determined close agreement was obtained between the prediction of the model and the experimental grain size value.

Fabrication and Characterization of Nanostructured Surface Layer of 38CrSi Steel

2007 ◽  
Author(s):  
Shi-Ning Ma ◽  
De-Ma Ba ◽  
Chang-Qing Li ◽  
Fan-Jun Meng
Keyword(s):  
Electron Microscopy ◽  
Grain Size ◽  
Surface Layer ◽  
Grain Refinement ◽  
Fine Particles ◽  
Nanostructured Surface ◽  
Cell Structures ◽  
Strain And Strain Rate ◽  
Transmission Electron ◽  
Average Grain Size

A nanocrystalline surface layer was fabricated on a 38CrSi Steel with tempered sorbite structure by using Supersonic Fine Particles Bombarding (SFPB). The microstructural evolution of SFPB-treated specimens under different processing conditions was characterized by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Experimental evidence showed severe plastic deformation and obvious grains refinement were observed and a nanocrystalline surface layer (grain size < 100nm) was found after SFPB treatment. The thickness of nanostructured surface layer varies from a few to about 25μm as treated time increasing from 80s to 240s, but the grain size varies slightly. For the sample treated for 240s, the average grain size of equiaxed nanocrystallites with random crystallographic orientations on the top surface layer is about 16nm. The indexing of diffraction rings indicates nanostructured surface layer consists of ferrite and cementite phases without any evidence of a new phase. The structure size increases gradually from nano-scale to original-scale with an increase of the distance from the top surface layer. In the region about 20–30μm deep from the top surface, the microstructures are mainly composed of 60–100nm roughly equiaxed grains and subgrains. Some subbounsaries are composed of dense dislocation walls (DDWs). In this regime some cell structures are also seen, which are separated by dislocation lines (DTs) and some DDWs. Experimental analysis indicate coarse-grains are gradually refined into nano-sized grains by dislocations activity with gradual increase of strain and strain rate from matrix to treated surface. Both ferrite and cementite phases occur grain refinement. Grain refinement of 38CrSi sample is mainly attributed to the movement of dislocation.

Highly Sinterable Lithium Titanate Powders Fabricated by an Organic-Inorganic Solution Route

2007 ◽  
Vol 124-126 ◽  
pp. 807-810 ◽  
Author(s):  
Myung Hyun Lee ◽  
Choong Hwan Jung ◽  
Sang Jin Lee
Keyword(s):  
Grain Size ◽  
Ethylene Glycol ◽  
Primary Particle ◽  
Fine Particles ◽  
Titanium Isopropoxide ◽  
Lithium Titanate ◽  
Lithium Nitrate ◽  
Porous Powder ◽  
Solution Route ◽  
Liquid Type

Highly sinterable lithium titanate (Li2TiO3) powder was fabricated by an organic-inorganic solution route. Liquid-type ethylene glycol (EG) was used as an organic carrier for the metal cations. Titanium isopropoxide and lithium nitrate were dissolved in the liquid-type ethylene glycol without any precipitation. The dried precursor gel showed crystalline form at 300 °C and carbon-free Li2TiO3 was observed above 400 °C. The primary particle size of the carbon-free Li2TiO3 was about 100 nm, and the structure of the crystallized powder was porous and agglomerated. The porous powder was ball-milled and easily ground to fine particles. The powder compact was densified to 93% theoretical density (TD) at relatively low sintering temperature of 1100 °C for 2 h. The densifed Li2TiO3 showed a small grain size of 1.2 μm. As well, the grain size was notably increased at 1200 °C and above. After the over grain growth, further densification was no more observed.

Significance of High Rate Superplasticity in Metallic Materials

1990 ◽  
Vol 196 ◽  
Author(s):  
Norio Furushiro ◽  
Shigenori Hori
Keyword(s):  
Grain Size ◽  
High Strain Rate ◽  
Strain Rate ◽  
Grain Refinement ◽  
Fine Particles ◽  
High Strain ◽  
High Rate ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Al Alloy

ABSTRACTIt has been expected that “High rate superplastic materials” will be developed for industrial applications. The Dorntype equation for high temperature deformation suggests that strain rate can be increased if the grain size is decreased. This means that grain refinement can effectively establish high strain rate superplastic materials.It is well known that a high degree of grain size refinement will result from the addition of zirconium to Al-base alloys. Powder-metallurgical processing with rapidly solidified powders is also available for the improvement of superplasticity by both the refinement of the solidified structure and the maintenance of the stable fine structure of a 7475 Al alloy during recrystallization and deformation. Therefore. P/M 7475 Al alloys containing Zr up to 0.9 wt% were selected as candidate specimens. The objective of the present paper includes the clarification of the role and the effective amount of Zr to obtain high strain rate superplastic materials. As a result, the addition of 0.3%Zr or more is effective in grain refinement of the P/M 7475 Al alloy. However, alloys containing 0.7 and 0.9 wt%Zr only show superplasticity at 793K. The optimum strain rate is shifted to a higher range with increasing Zr. The alloy of 7475 Al-0.9%Zr shows the maximum elongation of 900% at the remarkably high strain rate of 3.3×10−1 s−1.The deformation mechanism of such high stain rate superplasticity will be discussed briefly, by considering the effect of the fine particles of Zr on superplastic behavior.

Similarity of internal stability criteria for granular soils

1992 ◽  
Vol 29 (4) ◽  
pp. 711-713 ◽  
Author(s):  
Robert P. Chapuis
Keyword(s):  
Grain Size ◽  
Groundwater Flow ◽  
Distribution Curve ◽  
Fine Particles ◽  
Frost Damage ◽  
Granular Soils ◽  
Internal Stability ◽  
Stability Criteria ◽  
Mathematical Expressions ◽  
Internal Instability

Internal instability produces segregation in fine particles, modifies drainage properties, and increases pore pressures, capillary retention, and possible frost damage. Three criteria are commonly used to assess the internal instability of granular soils. It is shown here that they can take similar mathematical expressions where the secant slope of the grain-size distribution curve indicates the risk of internal instability. Key words : suffossion, groundwater flow, gradation.

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