Tube Suction Test for Evaluating Aggregate Base Materials in Frost- and Moisture-Susceptible Environments

2000 ◽  
Vol 1709 (1) ◽  
pp. 78-90 ◽  
Author(s):  
Imran Syed ◽  
Tom Scullion ◽  
Robert B. Randolph
Keyword(s):  
Dielectric Constant ◽  
New Mexico ◽  
Construction Projects ◽  
Capillary Rise ◽  
High Surface ◽  
Base Material ◽  
Dielectric Constants ◽  
Improved Performance ◽  
Tube Suction ◽  
Granular Base

A simple tube suction test has been developed by the Finnish National Road Administration for evaluating unstabilized granular base material. The test consists of monitoring the capillary rise of moisture within a 150-mm-diameter by 200-mm-high cylinder of compacted aggregate. A probe is used to measure the dielectric constant at the surface of the sample. The dielectric constant is a measure of the free, or unbound, water within the aggregate sample. It is this unbound water that is thought to be directly related to the strength of the material and its ability to withstand repeated freeze-thaw cycling. Measurements of dielectric constants are made over a period of 10 days. The poorest performing materials are those that rapidly reach saturation and exhibit high surface dielectric values. A study was conducted on four marginal aggregates from Alaska, Nevada, New Mexico, and Texas. These aggregates have been reported to be poor performers in their environments. Each aggregate failed the tube suction test. A mineralogical evaluation was performed to identify the mineral composition of each aggregate and to explain their high affinity for moisture. Subsequently the aggregates were treated with a concentrated liquid stabilizer. Upon treatment the aggregates showed improved performance in the tube suction test. The Alaska, Nevada, and New Mexico aggregates were then used in construction projects. Initial performance reports have been promising. The tube suction test described in this research has the potential to identify moisture-susceptible aggregates and to serve as a guide in selecting the optimal stabilizer type and amount.

Using Suction and Dielectric Measurements as Performance Indicators for Aggregate Base Materials

1997 ◽  
Vol 1577 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Tom Scullion ◽  
Timo Saarenketo
Keyword(s):  
Capillary Rise ◽  
High Surface ◽  
Base Material ◽  
Cold Weather ◽  
Base Materials ◽  
Aggregate Sample ◽  
Flexible Base ◽  
Granular Base ◽  
Aggregate Base ◽  
Moisture Conditions

A simple laboratory test for evaluating unstabilized granular base material is introduced. The test consists of monitoring the capillary rise of moisture within a 300-mm-high cylinder of compacted aggregate. The moisture conditions at the aggregate surface are monitored with a dielectric probe. A graph of surface dielectric versus time is used as the basis for performance classification. The poorest-performing materials are those that rapidly reach saturation and exhibit high surface dielectric values. The dielectric is a measure of the “free” or unbound water within the aggregate sample. It is not a simple measure of the moisture content of the material but an assessment of the state of bonding of the water within the fine aggregates. It is this unbound water that is thought to be directly related to the strength of the material and to its ability to withstand repeated freeze-thaw cycling. This test was developed by the Finnish National Road Administration and successfully used to investigate a major flexible base failure. The test is now under evaluation in Texas, where several Panhandle districts have reported cold-weather pavement cracking problems that they have attributed to the flexible bases. The test setup and equipment used are described, and test results from several base materials are presented. Also discussed are laboratory results from a recently completed project comparing eight Texas and four Finnish aggregates. One of the Finnish aggregates was classified as a poor performer; the remaining three were good performers. All of the Texas aggregates were rated as inferior to the high-quality Finnish aggregates. If this test is found to be successful in discriminating good- from bad-performing materials, it could be used to flag potentially poor performers and to evaluate the effectiveness of different base improvement techniques such as chemical stabilization or fines replacement.

Microstructure and physical properties of composite nonwovens produced by incorporating cotton fibers in elastic spunbond and meltblown webs for medical textiles

2021 ◽  
pp. 152808372110042
Author(s):  
Partha Sikdar ◽  
Gajanan S Bhat ◽  
Doug Hinchliff ◽  
Shafiqul Islam ◽  
Brian Condon
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Composite Structures ◽  
High Surface ◽  
High Surface Area ◽  
Barrier Properties ◽  
Cotton Fibers ◽  
Adult Care ◽  
Medical Textiles ◽  
Improved Performance

The objective of this research was to produce elastomeric nonwovens containing cotton by the combination of appropriate process. Such nonwovens are in demand for use in several healthcare, baby care, and adult care products that require stretchability, comfort, and barrier properties. Meltblown fabrics have very high surface area due to microfibers and have good absorbency, permeability, and barrier properties. Spunbonding is the most economical process to produce nonwovens with good strength and physical properties with relatively larger diameter fibers. Incorporating cotton fibers into elastomeric nonwovens can enhance the performance of products, such as absorbency and comfort. There has not been any study yet to use such novel approaches to produce elastomeric cotton fiber nonwovens. A hydroentangling process was used to integrate cotton fibers into produced elastomeric spunbond and meltblown nonwovens. The laminated web structures produced by various combinations were evaluated for their physical properties such as weight, thickness, air permeability, pore size, tensile strength, and especially the stretch recovery. Incorporating cotton into elastic webs resulted in composite structures with improved moisture absorbency (250%-800%) as well as good breathability and elastic properties. The results also show that incorporating cotton can significantly increase tensile strength with improved spontaneous recovery from stretch even after the 5th cycle. Results from the experiments demonstrate that such composite webs with improved performance properties can be produced by commercially used processes.

scholarly journals Comment on “investigation of dielectric constants of water in a nano-confined pore” by H. Zhu, F. Yang, Y. Zhu, A. Li, W. He, J. Huang and G. Li, RSC Adv., 2020, 10, 8628

RSC Advances ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 5179-5181
Author(s):  
Sayantan Mondal ◽  
Biman Bagchi
Keyword(s):  
Dielectric Constant ◽  
Dielectric Constants ◽  
Static Dielectric Constant ◽  
Inherent Anisotropy ◽  
Nanoconfined Water

Neglects of inherent anisotropy and distinct dielectric boundaries may lead to completely erroneous results. We demonstrate that such mistakes can give rise to gross underestimation of the static dielectric constant of cylindrically nanoconfined water.

DIELECTRIC CONSTANT AND SEEBECK COEFFICIENT FOR SEMICONDUCTORS: THERMODYNAMIC AND DFT STUDIES

2013 ◽  
Vol 12 (06) ◽  
pp. 1350057 ◽  
Author(s):  
HSIU-YA TASI ◽  
CHAOYUAN ZHU
Keyword(s):  
Boundary Condition ◽  
Dielectric Constant ◽  
Seebeck Coefficient ◽  
Gas Phase ◽  
Present Method ◽  
Dielectric Constants ◽  
Semiconductor Materials ◽  
Electronic Polarizability ◽  
Seebeck Coefficients ◽  
Good Agreement

Dielectric constants and Seebeck coefficients for semiconductor materials are studied by thermodynamic method plus ab initio quantum density functional theory (DFT). A single molecule which is formed in semiconductor material is treated in gas phase with molecular boundary condition and then electronic polarizability is directly calculated through Mulliken and atomic polar tensor (APT) density charges in the presence of the external electric field. This electronic polarizability can be converted to dielectric constant for solid material through the Clausius–Mossotti formula. Seebeck coefficient is first simulated in gas phase by thermodynamic method and then its value divided by its dielectric constant is regarded as Seebeck coefficient for solid materials. Furthermore, unit cell of semiconductor material is calculated with periodic boundary condition and its solid structure properties such as lattice constant and band gap are obtained. In this way, proper DFT function and basis set are selected to simulate electronic polarizability directly and Seebeck coefficient through chemical potential. Three semiconductor materials Mg 2 Si , β- FeSi 2 and SiGe are extensively tested by DFT method with B3LYP, BLYP and M05 functionals, and dielectric constants simulated by the present method are in good agreement with experimental values. Seebeck coefficients simulated by the present method are in reasonable good agreement with experiments and temperature dependence of Seebeck coefficients basically follows experimental results as well. The present method works much better than the conventional energy band structure theory for Seebeck coefficients of three semiconductors mentioned above. Simulation with periodic boundary condition can be generalized directly to treat with doped semiconductor in near future.

scholarly journals A note on some further determinations of the dielectric constants of organic bodies and electrolytes at very low temperatures

1898 ◽  
Vol 62 (379-387) ◽  
pp. 250-266 ◽  
Keyword(s):  
Dielectric Constant ◽  
Low Temperatures ◽  
Tuning Fork ◽  
Dielectric Constants ◽  
The Past ◽  
Method Of Measurement ◽  
The Given ◽  
Past Summer

In several previous communications we have described the investigations made by us on the dielectric constants of various frozen organic bodies and electrolytes at very low temperatures. In these researches we employed a method for the measurement of the dielectric constant which consisted in charging and discharging a condenser, having the given body as dielectric, through a galvanometer 120 times in a second by means of a tuning-fork interrupter. During the past summer we have repeated some of these determinations and used a different method of measurement and a rather higher frequency. In the experiments here described we have adopted Nernst’s method for the measurement of dielectric constants, using for this purpose the apparatus as arranged by Dr. Nernst which belongs to the Davy-Faraday Laboratory.

Epitaxial Growth and Anisotropic Dielectric Properties of La-Doped Bi4Ti3O12 Thin Films

2007 ◽  
Vol 124-126 ◽  
pp. 177-180
Author(s):  
Jang Sik Lee ◽  
Q.X. Jia
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bottom Electrode ◽  
Dielectric Constants ◽  
The Other ◽  
Field Range ◽  
Anisotropic Dielectric ◽  
Dielectric Nonlinearity ◽  
La Doped

To investigate the anisotropic dielectric properties of layer-structured bismuth-based ferroelectrics along different crystal directions, we fabricate devices along different crystal orientations using highly c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films on (001) LaAlO3 (LAO) substrates. Experimental results have shown that the dielectric properties of the BLT films are highly anisotropic along different crystal directions. The dielectric constants (1MHz at 300 K) are 358 and 160 along [100] and [110], respectively. Dielectric nonlinearity is also detected along these crystal directions. On the other hand, a much smaller dielectric constant and no detectable dielectric nonlinearity in a field range of 0-200 kV/cm are observed for films along [001] when c-axis oriented SRO is used as the bottom electrode.

Fabrication of low dielectric constant polyimide/TiO2 nanofibers with enhanced UV-light shielding properties

2018 ◽  
Vol 31 (8) ◽  
pp. 986-995
Author(s):  
Lei Wang ◽  
Guifen Gong ◽  
Junyao Shen ◽  
Jinsong Leng
Keyword(s):  
Dielectric Constant ◽  
Light Absorption ◽  
Composite Nanofibers ◽  
Uv Light ◽  
Dielectric Constants ◽  
Low Dielectric Constant ◽  
Number Density ◽  
Tio2 Nanofibers ◽  
Low Dielectric ◽  
Mechanical Tensile

Polyimide (PI)/titanium dioxide (TiO2) composite nanofibers (NFs) with average diameters of 200–250 nm were synthesized via electrospinning. The total number density of dipoles decreased significantly, owing to the porous structures and compact interface between TiO2 NPs and PI matrix. All PI/TiO2 NFs maintain low dielectric constants and losses. For example, the dielectric constants of PI/TiO2-6% NFs are all lower than 2.6, being exposed to temperatures from 25°C to 200°C. Meantime, the dielectric losses of PI/TiO2-6% NFs are below 0.005. For ultraviolet (UV)-light shielding performance, the PI/TiO2 NFs exhibited good UV-light shielding and corresponding anti-photoaging properties. The reason can be ascribed from high UV-light absorption and scattering ability in the TiO2 NPs. The best UV-light absorption (average: 3.71) and corresponding absorption decay (15.13%) were achieved for optimized PI/TiO2-6% NFs. Other fundamental characteristics, such as the thermal stability, mechanical tensile property, and hydrophobicity, were also investigated. Such low dielectric constant PI/TiO2 composite NFs can be alternatively chosen under a longtime UV-light exposing condition.

Moisture Accumulation and Pore Water Pressures at Base of Pavements

1996 ◽  
Vol 1546 (1) ◽  
pp. 151-161 ◽  
Author(s):  
K. D. Eigenbrod ◽  
G. J. A. Kennepohl
Keyword(s):  
Pore Water ◽  
Base Material ◽  
The United States ◽  
Base Layer ◽  
Frozen Ground ◽  
Extensive Field ◽  
Pore Water Pressures ◽  
Excess Moisture ◽  
Pavement Base ◽  
Granular Base

A unique mechanism based on extensive field and laboratory studies is presented to account for certain premature failures of flexible pavements in cold areas like those in Scandinavia and in northern parts of Canada and the United States. Water condensing at the interface between pavement and granular base accumulates at subzero temperatures resulting in excess moisture in this zone. During the thaw period of the uppermost base layer, the excess water in the aggregate is trapped between impervious layers of frozen ground to the sides and below as well as an impervious layer of asphalt pavement above. Because of this containment, high pore water pressures can occur, leading to loss in shear strength of the base material and thus to failure of the pavement structure itself. It was found that under special conditions, excess moisture can accumulate in granular base with a silt content greater than 20 percent and very high pore water pressures can develop during initial thaw at the pavement-soil interface. With silt contents of less than 2 percent, excess pore water pressures can be avoided during thaw. It was also shown that when a clean open gravel is placed below the pavement on top of a silty base material, moisture accumulation near the pavement-base interface can be prevented, and thus also the development of high pore water pressures.

scholarly journals Prediction Model of Elastic Modulus for Granular Road Bases

2020 ◽  
Vol 2 (1) ◽  
pp. p35
Author(s):  
Zainab Ahmed Alkaissi ◽  
Hassan Adnan
Keyword(s):  
Elastic Modulus ◽  
Linear Regression Analysis ◽  
Base Material ◽  
Recycled Concrete ◽  
Dry Density ◽  
Concrete Aggregate ◽  
Vertical Loading ◽  
Base Materials ◽  
Granular Base ◽  
Road Bases

The estimation of elastic modulus for road bases is the primary objective of this research which is implemented a significant role in transmitting the vertical loading to the pavement foundation layers. In this study, the effect of weathering conditions on the stiffness of base course is investigated and implied the durability test by subjecting the prepared samples to a different numbers of wet-dry cycles (0,2, 4, 6, 8 and 10). A conventional base materials of local natural gravel aggregate and treated base materials with recycled concrete aggregate RCA at different percentages (0%, 25%, 50% 75% and 100%) is adopted in this research. The elastic characteristics are estimated in terms of elastic modulus. Elastic modulus are estimated by passing the ultrasonic pulse velocity through the untreated and treated base materials laboratory specimens. This test can be used to study the elastic modulus properties of base materials. A multiple linear regression analysis is used for prediction the elastic modulus using the SPSS (software ver.21). Elastic Modulus (kPa) is the dependent variable whereas the independent variable are; No. of wet- dry cycle and Percent (%) of RCA stabilizer. The obtained results for elastic modulus (Es) of granular base material layer showed increasing in elastic modulus with percentage of RCA%., results revealed that the (Es) values reached a maximum value of (6927kPa) for 100%. For the OMC’s values increases due to the percentage increment of RCA in granular base material mixture, this increment in water contents is refer to high absorption capacity of the paste clinging to the RCA. On other side the dry density decrease gradually with adding percentage of (RCA) in granular base material mixture.

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