Contact erosion initiated by clay dispersion beneath pavement layers

2020 ◽  
pp. 1-23
Author(s):  
S. Premkumar ◽  
J. Piratheepan ◽  
P. Rajeev
Keyword(s):  
Clay Dispersion ◽  
Contact Erosion ◽  
Pavement Layers

Laboratory Model Test on Contact Erosion of Dispersive Soil Beneath Pavement Layers

2015 ◽  
Vol 38 (6) ◽  
pp. 20140179 ◽  
Author(s):  
Piratheepan Jegatheesan ◽  
Premkumar Sothilingam ◽  
Arul Arulrajah ◽  
M. M. Disfani ◽  
Pathmanathan Rajeev
Keyword(s):  
Model Test ◽  
Laboratory Model ◽  
Contact Erosion ◽  
Pavement Layers ◽  
Laboratory Model Test ◽  
Dispersive Soil

scholarly journals In-Line Rheo-Optical Investigation of the Dispersion of Organoclay in a Polymer Matrix during Twin-Screw Compounding

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2128
Author(s):  
Paulo F. Teixeira ◽  
José A. Covas ◽  
Loïc Hilliou
Keyword(s):  
Local Heating ◽  
Polymer Nanocomposite ◽  
Structural Rearrangement ◽  
Particle Dispersion ◽  
Optical Investigation ◽  
Twin Screw Extrusion ◽  
Clay Particles ◽  
Clay Dispersion ◽  
Screw Extrusion ◽  
Twin Screw

The dispersion mechanisms in a clay-based polymer nanocomposite (CPNC) during twin-screw extrusion are studied by in-situ rheo-optical techniques, which relate the CPNC morphology with its viscosity. This methodology avoids the problems associated with post extrusion structural rearrangement. The polydimethylsiloxane (PDMS) matrix, which can be processed at ambient and low temperatures, is used to bypass any issues associated with thermal degradation. Local heating in the first part of the extruder allows testing of the usefulness of low matrix viscosity to enhance polymer intercalation before applying larger stresses for clay dispersion. The comparison of clay particle sizes measured in line with models for the kinetics of particle dispersion indicates that larger screw speeds promote the break-up of clay particles, whereas smaller screw speeds favor the erosion of the clay tactoids. Thus, different levels of clay dispersion are generated, which do not simply relate to a progressively better PDMS intercalation and higher clay exfoliation as screw speed is increased. Reducing the PDMS viscosity in the first mixing zone of the screw facilitates dispersion at lower screw speeds, but a complex interplay between stresses and residence times at larger screw speeds is observed. More importantly, the results underline that the use of larger stresses is inefficient per se in dispersing clay if sufficient time is not given for PDMS to intercalate the clay galleries and thus facilitate tactoid disruption or erosion.

Nature of the clay - cation bond affects soil structure as verified by X-ray computed tomography

Soil Research ◽  
2012 ◽  
Vol 50 (8) ◽  
pp. 638 ◽  
Author(s):  
Alla Marchuk ◽  
Pichu Rengasamy ◽  
Ann McNeill ◽  
Anupama Kumar
Keyword(s):  
Computed Tomography ◽  
Hydraulic Conductivity ◽  
Zeta Potential ◽  
Structural Stability ◽  
Structural Parameters ◽  
Pore Connectivity ◽  
X Ray ◽  
Clay Dispersion ◽  
X Ray Computed ◽  
Cation Ratio

Non-destructive X-ray computed tomography (µCT) scanning was used to characterise changes in pore architecture as influenced by the proportion of cations (Na, K, Mg, or Ca) bonded to soil particles. These observed changes were correlated with measured saturated hydraulic conductivity, clay dispersion, and zeta potential, as well as cation ratio of structural stability (CROSS) and exchangeable cation ratio. Pore architectural parameters such as total porosity, closed porosity, and pore connectivity, as characterised from µCT scans, were influenced by the valence of the cation and the extent it dominated in the soil. Soils with a dominance of Ca or Mg exhibited a well-developed pore structure and pore interconnectedness, whereas in soil dominated by Na or K there were a large number of isolated pore clusters surrounded by solid matrix where the pores were filled with dispersed clay particles. Saturated hydraulic conductivities of cationic soils dominated by a single cation were dependent on the observed pore structural parameters, and were significantly correlated with active porosity (R2 = 0.76) and pore connectivity (R2 = 0.97). Hydraulic conductivity of cation-treated soils decreased in the order Ca > Mg > K > Na, while clay dispersion, as measured by turbidity and the negative charge of the dispersed clays from these soils, measured as zeta potential, decreased in the order Na > K > Mg > Ca. The results of the study confirm that structural changes during soil–water interaction depend on the ionicity of clay–cation bonding. All of the structural parameters studied were highly correlated with the ionicity indices of dominant cations. The degree of ionicity of an individual cation also explains the different effects caused by cations within a monovalent or divalent category. While sodium adsorption ratio as a measure of soil structural stability is only applicable to sodium-dominant soils, CROSS derived from the ionicity of clay–cation bonds is better suited to soils containing multiple cations in various proportions.

Automatic detection of multiple pavement layers from GPR data

2008 ◽  
Vol 41 (2) ◽  
pp. 69-81 ◽  
Author(s):  
Samer Lahouar ◽  
Imad L. Al-Qadi
Keyword(s):  
Automatic Detection ◽  
Pavement Layers

Electrical contact performance of various electro-deposited graphene reinforced silver-based nanocomposites

2020 ◽  
Vol 62 (4) ◽  
pp. 401-407
Author(s):  
Ramazan Karslioglu ◽  
Lujain Al-Falahi
Keyword(s):  
Pulse Current ◽  
Electrical Contact ◽  
Reverse Current ◽  
Electrical Contacts ◽  
Test Device ◽  
Arc Erosion ◽  
Contact Test ◽  
Grain Sizes ◽  
Contact Erosion ◽  
Pulse Reverse

Abstract Silver and silver(Ag)-graphene(Gr) nanocomposite coatings were prepared via direct current, pulse current and pulse reverse current on copper electrical contacts for evaluating electrical contact performance. The effects of the addition of Gr and current types on microstructure, crystallographic orientation, mechanical properties and electrical contact performance were investigataed via a scanning electron microscope, an X-Ray diffractometer, microhardness test device and an electrical contact test device, respectively. The addition of Gr changed the Ag surface morphology and decreased grain sizes. Moreover, the addition of Gr significantly improved arc erosion resistivity and decreased the average working temperature during the contact test. In addition, pulse current and pulse reverse current provided a significant improvement in microhardness and electrical contact erosion resistance owing to increased embedded graphene amounts in silver layers.

scholarly journals Factors affecting clay dispersion in oxisols treated with vinasse

2016 ◽  
Vol 37 (6) ◽  
pp. 3997 ◽  
Author(s):  
Thadeu Rodrigues de Melo ◽  
Tiago Santos Telles ◽  
Walquiria Silva Machado ◽  
João Tavares Filho
Keyword(s):  
Sandy Soil ◽  
Physical Quality ◽  
Factors Affecting ◽  
Clay Dispersion ◽  
Water Dispersible ◽  
Dispersive Effect ◽  
Bivalent Cations ◽  
Chemical Attributes ◽  
Almost All ◽  
Dispersible Clay

Vinasse is a potassium-rich waste generated in large amounts by the ethanol production that, applied in the soil, can promote changes in water dispersible clay and in its physical quality. The aim of this study was to evaluate the clay dispersion of Oxisols after vinasse application and correlate it with some chemical attributes. Samples were collected in two Oxisols (155 and 471 g of clay kg-1), put in pots, received dosages of vinasse (0, 50, 100, 150 and 200 m3 ha-1) and remained incubated during 120 days. Phosphorous, organic carbon, pH H2O, pH KCl, pH CaCl2, Al3+, H+Al3+, Ca2+, Mg2+, K+, Na+, Delta pH and the proportion between monovalent and bivalent cations have been evaluated and correlated with the clay flocculation degree. Vinasse changed almost all chemical variables in both soils and increased the flocculation in the sandy soil, but did not change the clayey one. Delta pH, Mg2+ and K+ significantly correlated with the flocculation degree in the sandy soil. It is possible to conclude that the dispersive effect of K+ added by vinasse are irrelevant, considering the flocculant effect caused by the increment in Mg2+ and Delta pH after vinasse application.

Sign in / Sign up

Export Citation Format

Share Document