scholarly journals Direct observation of particle kinematics in biaxial shearing test

2021 ◽  
Author(s):  
Usman Ali ◽  
◽  
Mamoru Kikumoto ◽  
Matteo Ciantia ◽  
Ying Cui ◽  
...  
Keyword(s):  
Shape Descriptor ◽  
Particle Rotation ◽  
Image Analysis Technique ◽  
Analysis Technique ◽  
Particle Level ◽  
Confining Pressures ◽  
The Difference ◽  
Granular Behavior ◽  
Particle Assemblies ◽  
Bulk Behavior

Biaxial shearing tests on dual-sized, 2d particle assemblies are conducted at several confining pressures. The effect of particle angularity, an important mesoscale shape descriptor, is investigated at the macro and micro levels. Macroscopically, it is observed that assemblies composed of angular particles exhibit higher strengths and dilations. The difference observed in bulk behavior due to particle angularity can be explained reasonably by considering particle-level mechanisms. A novel 2D image analysis technique is employed to estimate particle kinematics. Particle rotation results to be a key mechanism strongly influenced by particle shape determining the overall granular behavior. Unlike circular particles, angular ones are more resistant to rotations due to stronger interlocking and consequently exhibit higher strengths.

scholarly journals Influence of The Segregation Phenomenon on Structural Efficiency of Lightweight Aggregate Concretes

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5754
Author(s):  
Afonso Miguel Solak ◽  
Antonio José Tenza-Abril ◽  
Victoria Eugenia García-Vera
Keyword(s):  
Lightweight Aggregate ◽  
Segregation Index ◽  
Image Analysis Technique ◽  
Structural Efficiency ◽  
Trapped Air ◽  
Analysis Technique ◽  
Segregation Phenomenon ◽  
The Difference ◽  
Materials Used ◽  
The Impact

Lightweight aggregate concretes (LWAC) are versatile and interesting materials for projects that require greater structural efficiency. Due to the difference that exists between the densities of the materials used in these types of concrete, during transport and mainly compaction, their aggregates tend to separate from the mortar matrix, floating towards the surface, a phenomenon called segregation. Segregation in LWAC can affect its durability properties, its density, and directly affect its structural efficiency. In this work, different concrete densities (1700 kg/m3 and 1900 kg/m3) manufactured with different dosages (two different lightweight aggregates) and compaction methods (one or two layers) were analyzed to verify the impact of segregation on its structural efficiency. For this purpose, the segregation index of the LWAC was obtained by means of the image analysis technique. In addition, to obtain their structural efficiency, the density and compressive strength were obtained at different heights of the tested specimens. The results show the vibration of the samples in two layers leads to a more efficient elimination of trapped air, a reduction in the risk of segregation, and better structural efficiency.

Chemical, Microstructural, and Rheological Characterizations of Binders to Evaluate Aging and Rejuvenation

2017 ◽  
Vol 2632 (1) ◽  
pp. 14-24 ◽  
Author(s):  
Patrícia Hennig Osmari ◽  
Francisco Thiago Sacramento Aragão ◽  
Leni Figueiredo Mathias Leite ◽  
Renata Antoun Simão ◽  
Laura Maria Goretti da Motta ◽  
...  
Keyword(s):  
Digital Image Analysis ◽  
Gel Permeation Chromatography ◽  
Waste Cooking Oil ◽  
Asphalt Binders ◽  
Size Distributions ◽  
Image Analysis Technique ◽  
Cooking Oil ◽  
Atomic Force ◽  
Analysis Technique ◽  
Key Variables

This study evaluated the effects of the commercial product, AR 5, and two alternative products, waste cooking oil and castor oil, in the rejuvenation process of two asphalt binders. The analyses were carried out on microscopic and macroscopic scales on virgin, aged, and rejuvenated binders. Tests in a dynamic shear rheometer were performed to characterize rheological properties of the binders. Then, an atomic force microscope was used to identify microstructural changes in the materials. A digital image analysis technique enabled the quantification of key variables such as area fraction and spatial and size distributions of the binder constituents. Finally, the following chemical tests were performed to identify changes in the chemical composition of the binders resulting from the aging and rejuvenation processes: SARA (which measures saturates, asphaltenes, resins, and aromatics), gel permeation chromatography, and nuclear magnetic resonance. The results obtained from the tests were further compared to identify correlations between the properties evaluated in different scales. The results demonstrated the efficiency and potential of the rejuvenators evaluated in this study. The results also highlighted the importance of the use of advanced techniques to characterize and understand the material aging and rejuvenation processes.

Carbon Fiber Reinforced Cement and Mortar

1990 ◽  
Vol 211 ◽  
Author(s):  
J. R. Linton ◽  
P. L. Berneburg ◽  
E. M. Gartner ◽  
A. Bentur
Keyword(s):  
Carbon Fibers ◽  
Fiber Length ◽  
Length Distribution ◽  
Fiber Breakage ◽  
Image Analysis Technique ◽  
Analysis Technique ◽  
Reinforcing Fibers ◽  
Before And After ◽  
Reinforced Cement ◽  
Critical Fiber Length

AbstractAlthough carbon fibers have high tensile strengths and are chemically inert, their application in cementitious composites is limited due to their brittleness. An image analysis technique employed to determine the length distribution of the reinforcing fibers before and after mixing in cement paste and mortar matrices indicates that substantial fiber breakage occurs during mixing. In paste mixtures, the average fiber length after mixing remains above the critical fiber length, but in mortar mixes the average fiber length falls below the critical fiber length resulting in no significant enhancement of composite flexural properties.

A technique in confocal laser microscopy for establishing biofilm coverage and thickness

1997 ◽  
Vol 36 (10) ◽  
pp. 117-124 ◽  
Author(s):  
G. Silyn-Roberts ◽  
G. Lewis
Keyword(s):  
Laser Scanning ◽  
Sewage Treatment ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Rock Surface ◽  
Optical Sectioning ◽  
Image Analysis Technique ◽  
Rock Types ◽  
Analysis Technique ◽  
Biofilm Quantification

This study uses confocal laser scanning microscopy to determine the coverage and thickness of biofilms on rock types commonly used in wetland sewage treatment systems in New Zealand. Samples of scoria, greywacke and slag - with glass used as a comparison - were submerged in subsurface flow wetlands and examined after six weeks. An image analysis technique was used to quantitatively determine the coverage and thickness of each biofilm. The technique consisted of the biofilm quantification of each individual image obtained from the confocal optical sectioning. The results indicated that the biofilm coverage for the substrata types did not exceed 25%. However, there was a marked difference between the biofilm structures grown on the different substrata; that on glass formed thin spindly structures, and slag and scoria showed similar dense patches interspersed with open channel structures that followed the contours of the pocketed rock surface.

Sign in / Sign up

Export Citation Format

Share Document