bluuebunny/crossref_metadata_2025 huggingface dataset:
Strained Quartz in Relation to Alkali-Silica Reaction
Authors: Cortelezzi CR , Maiza P , Pavlicevic RE
Published: March 2009

Aggregates containing strained quartz crystals that have induced damage in concrete structures, are frequently mentioned in the literature. This kind of aggregate has generated economic as well as functional problems, with the consequent additional expenses for repair and maintenance. Samples of granitic, cataclastic migmatite aggregates from the Province of Buenos Aires were studied.

Percentages of strained quartz, based on its undulatory extinction angle, are presented and the results are compared to those obtained by the mortar-bar test, the accelerated evaluation method, and the staining method.

The reaction is ascribed to the polycrystallinity of the quartz grains, as shown by electron diffraction (TEM) and by X-ray diffractometry, both showing a disorder in the crystalline structure.
Laser Fluorescence Fingerprints of Environmental Materials
Authors: Mellone A , Smith BW , Vera JA , Winefordner JD
Published: March 2009

A continuous wave (cw) and a pulsed-gated laser fluorescence systems were used to measure fluorescence spectra of polycyclic aromatic hydrocarbons (PAHs) thermally vaporized using an electrothermal atomizer. The cw laser was a Helium-Cadmium (He-Cd) laser and the pulsed laser was a flashlamp dye laser. The detector was an intensified photodiode array. Individual PAHs as well as PAHs produced by vaporizing crude oils, particulate matter and other samples were studied by this approach. Fingerprinting was performed by measuring three-dimensional plots of fluorescence intensity versus emission wavelength versus evolution temperature.
Techniques and Applications of Two-Photon Spectroscopy of Inorganic Solids
Authors: McClure DS
Published: March 2009

Recent work on two-photon spectroscopy of transition metal ions and rare earth ions in crystals is reviewed. The technology of two-photon spectroscopy changes significantly from ultraviolet to visible to infrared, and the different methods for these regions are discussed with examples from the writer's laboratory.
Laser Induced Fluorescence and Ionization Techniques for Combustion Diagnostics
Authors: Forch BE , Morris JB , Miziolek AW
Published: March 2009

Light atomic species such as oxygen atoms (O) and hydrogen atoms (H) are fundamentally important in a wide variety of combustion-related phenomena such as flame ignition, propagation, extinction and in chemical flame reactions. Furthermore, they are difficult to detect by conventional laser based optical methods (laser induced fluorescence) in combustion environments because the necessary resonance excitation wavelengths fall far into the vacuum ultraviolet (vuv) and the requisite tunable laser sources are not generally available. However, recent developments in nonlinear spectroscopic techniques such as multiphoton induced emission (MPE) and multiphoton ionization (MPI) have made direct detection of these light atoms possible. We have utilized a number of laser multiphoton excitation schemes for their detection using tunable lasers in the 190 to 400 nm range. Similar diagnostic techniques were attempted for the detection of carbon (C) and nitrogen (N) atoms in flames. The effects of laser induced photochemical pertubations on species detection in flames were also investigated. These nonlinear spectroscopic techniques have been demonstrated to be very useful in combustion studies but special care needs to be taken with respect to possible perturbations that may result from the use of short-wavelength lasers.
Fluorescence Spectroscopy in the Analysis of Deoxyribonucleic Acid (DNA) Adducts
Authors: Hayes JM , Small GJ
Published: March 2009

An important first step in the initiation of carcinogenesis by polycyclic aromatic hydrocarbons (PAH), is the formation of a covalently bound adduct between the metabolized PAH and one or more deoxyribonucleic acid (DNA) bases. In vivo concentrations of these adducts are typically ∼1 adducted base per 108 normal DNA base pairs. Methods of generating high resolution fluorescence spectra of adducts at these levels will be described. Methods of overcoming factors such as photochemistry and nonphotochemical hole burning which limit detection limits will be described. By generating line narrowed fluorescence spectra, it is possible to spectrally distinguish between various adduct possibilities.
Laser Methods in Time-Resolved Anisotropy Measurements: Tetracene in 1-n-Dodecanol
Authors: Wirth MJ , Chou S-H
Published: March 2009

The double exponential decay of the fluorescence anisotropy of tetracene on the 50 to 500 ps time scale is measured quantitatively using a photomultiplier having a risetime of 800 ps. Frequency-domain spectroscopy, that is, the measurement of the phases and amplitudes of the frequency components comprising the decay, is used. The experimental considerations for obtaining quantitative measurements are discussed. The results of the study suggest that tetracene does not behave according to the Debye-Stokes-Einstein model in the solvent 1-n-dodecanol.
Luminescence and Thermal Lensing in Micellar and Related Media
Authors: Tran CD
Published: March 2009

The two fundamentally different techniques, fluorescence and thermal lens, can be simultaneously enhanced by normal as well as reversed micelles. The fluorescence is enhanced because the micelles isolate and protect the substrate from quencher molecules whereas the thermal lens enhancement is due to the modification of the thermo-optical properties of the solvent by micelles, that is, increase the temperature coefficient of the index of refraction, dn/dT, and decrease thermal conductivity values. Normal micelles provide the most effective means for the thermal lens enhancement of hydrophobic compounds while the reversed micelles are most suitable for hydrophilic compounds. This is because the normal micellar effects such as providing a nonpolar medium for the analyte and changing the structure of water from the compact, well hydrogen bonded structure to a relatively loose one are the main mechanism for the modification of the thermo-optical properties. On the other hand, reversed micelles improve the thermo-optical properties of the environment around the hydrophilic compounds by solubilizing them as very small water droplets in a better thermo-optical nonpolar solvent.
Laser Photolytic Fragmentation-Fluorescence Spectrometry of Nonfluorescent Organic and Organometalllc Molecules
Authors: Jinkins JG , Schendel J , Wehry EL
Published: March 2009

The use of fragmentation-fluorescence spectrometry as an analytical technique for the detection and quantification of nonfluorescent organic and organometallic compounds is described. Radiation from a photolysis laser, usually operated at 193 nm, photodissociates gaseous molecules, converting them into atomic or small molecular fragments which are intensely fluorescent. If necessary, fluorescence of fragments can be induced by a second, “probe,” laser. Limits of detection and precision of one- and two-laser photofragmentation-fluorescence determinations are given. The analytically desirable characteristics of laser fragmentation-fluorescence spectroscopy are described, and future directions for development of the technique are discussed.
Laser Based Fluorescence Methods for Materials Science
Authors: Wright JC
Published: March 2009

The properties of a material can be profoundly affected by trace amounts of dopants or impurities. The most common mechanism by which the properties are changed is through the solid state defect chemistry. Point defects in solids play the same role as pH in solution equilibrium chemistry. In the same way that pH exerts strong effects on solution equilibrium chemistry, point defect concentrations exert similarly strong effects on solid state chemistry and the resulting bulk properties of the material. Historically, one measures the defect concentrations indirectly by measuring bulk properties but one can also use site selective laser excitation methods to measure the point defect equilibria directly. In this paper, we will discuss the application of these ideas to the study of interesting materials.
Is Microstructure Important to the Performance of Geosynthetics?
Authors: Daniel JL
Published: March 2009

Questions are raised concerning the importance of microstructure to the long-term performance of geosynthetics. Since the long-term performance is of major interest, macrostructure should not be overlooked. The importance of understanding the minimum requirements for each product in each application is emphasized. Some traps are identified in using accelerated ageing to predict useful product lives. Long-term testing of products in a wide variety of applications and environments needs to be started immediately.
Service Life of Geosynthetics in Hazardous Waste Management Facilities
Authors: Landreth RE
Published: March 2009

The U.S. Environmental Protection Agency (EPA) has determined that flexible membrane liners are the most practical way of minimizing pollutant releases from hazardous waste treatment, storage, and disposal facilities. Other geosynthetic products including geotextiles, geonets, and plastic pipes are being used to construct leachate collection, detection, and removal systems. Geosynthetics are also being used in cover systems to minimize the infiltration of water into the waste management unit.

Although geosynthetics have recognized durability aspects, it is necessary to know more about the aging characteristics of polymeric materials as they function in modern waste disposal environments. To answer this question, the EPA held an ad hoc meeting in 1987 to determine if conclusions could be reached on the service life of geosynthetics and where, if any, were the data gaps. To help address the issue, representatives from polymer manufacturers, the engineering profession, and research fields were assembled to provide insight to the problem.

This paper discusses the consensus report developed as a result of that meeting. Specific areas that were discussed include chemical, mechanical, and biological stresses that may be encountered by geosynthetics in waste management facilities. The report concluded that currently used polymeric materials in waste management facilities do not encounter degradation conditions for the base polymer, and that these base polymers should last hundreds of years. However, inappropriate applications can lead to premature failures.
Microscopic Evaluation of High-Density Polyethylene Geomembrane Field-Welding Techniques
Authors: Rollin AL , Vidovic A , Denis R , Marcotte M
Published: March 2009

An investigation on seam quality of high-density polyethylene geomembrane has been conducted to demonstrate the importance of microscopic analyses for seam quality evaluation. Shear and peel tests were conducted to assess the quality of polyethylene geomembrane seams produced by known welding techniques, while sample cross sections of welds were analyzed using microscopic techniques. The shear and peel tests are usually performed to obtain quantitative measurements of seam strength. These test results are used as acceptance criteria to evaluate the bond strength. However, they do not adequately characterize molecular structure changes nor identify microstress cracks within the bonded sheets. Microscopic phenomena that may not be observed by these tests include contact areas where the depth of the melted polymer is very thin, displacement of a mass of polymer towards the edge of the seam, and formation of longitudinal channels across the seam. Microscopic photographs of seam cross sections are presented and discussed to evaluate seam quality.
Microscopic Stereological Methods to Characterize Orientation of Nonwoven Geotextile Fibers
Authors: Long JH , Lau KWK
Published: March 2009

Procedures for quantifying the orientation of fibers composing nonwoven geotextiles are presented. These procedures are based upon measurements made at the microscopic scale. Methods for experimentally determining the orientation of fibers within a nonwoven geotextile are presented. The experimental methods require the geotextile to be impregnated with a fluid that will eventually harden and preserve the original geometry of the fibers. Procedures vary from using fluids that use wax to procedures that incorporate fluids that eventually become very hard. Both thick sections and thin microtome sections (5 μm) can be used as the cross section from which orientation of the fibers is determined stereologically.

Orientations for the fibers are represented by combining the concepts of probability and three-dimensional orientation tensors. Three-dimensional orientations of the fibers are modelled using second-order and fourth-order orientation tensors. All the necessary parameters can be determined from stereological measurements on three mutually perpendicular planes and are determined from the results of digitizing microscopic cross sections of the geotextile.
Evaporation-Filtration Test for Emulsion Inversion
Authors: Marchal J-L
Published: March 2009

An evaporation-filtration test has been developed which attempts to characterize asphalt emulsions by inversion point. At usual asphalt contents, emulsions are of the oil-in-water type. After spraying, the water evaporates from the emulsion and the asphalt content increases, leading to coalescence, which would be expressed in terms of inversion to the water-in-oil type. The point at which this inversion occurs depends on many parameters. An investigation of some of these parameters is proposed.
Relationship Between Generation of CO and CO2 and Toxicity of the Environments Created by Materials in Flaming and Nonflaming Fires and Effect of Fire Ventilation
Authors: Tewarson A
Published: March 2009

In fires, combustion behavior of materials, generation rates, and concentrations of fire products depend on many factors, such as the chemical structures of materials (aliphatic to aromatic to highly halogenated), fire ventilation, airflow and mixing, shape, size and arrangement of the materials, heat flux received by the materials, etc. Thus, toxicity of the environment is expected to depend on these factors.

This paper examines the relationship between the combustion behavior of materials and the toxicity of the environment. In this analysis, only CO and CO2 are used, using the toxicity relationship suggested by Levin et al. [3] on the synergism between CO and CO2 and data measured in the Factory Mutual Research Corp. (FMRC) small-scale flammability apparatus.
Developments in International Smoke Obscuration Tests and British Assessment Procedures for Smoke Hazards in Fire Scenarios Containing Plastics
Authors: Briggs PJ
Published: March 2009

Assessment of the smoke hazard caused by materials and products has normally been solely from the results of small-scale or full-scale test methods. Recent British proposals suggest that the results of smoke tests should be used as part of a total method of smoke hazard assessment which would consider fire test data, product design, and room scenario in a way which would reflect the dangers of a product in a real fire situation. This proposed assessment procedure would prevent the misinterpretation of test data which can occur when smoke test data are compared in isolation without reference to other fire parameters.

Developments in static and dynamic procedures show that there are still significant differences in the fire models used in internationally recognized smoke obscuration tests. Results for small-scale tests (e.g., ISO single and dual chamber tests, NIST cone calorimeter) and large-scale tests (e.g., IEC 3m cube, room/duct, and room/corridor tests) are described. These results emphasize the need for a standardized analytical approach to smoke hazard assessment.
Predicting the Toxic Hazard of Cable Fires
Authors: Clarke FB , van Kuijk H , Steele S
Published: March 2009

Despite a growing interest in cable fires, no systematic evaluation of the toxic threat from cables under actual fire conditions has been attempted. The present paper demonstrates the methodology used by Benjamin/Clarke Associates to estimate hazard of cable smoke. The method makes use of small-scale fire property tests and computer modeling. Certain of the predictions have been tested at full scale.

The small-scale tests provide data on the response of the cables to a radiative heat environment, predicted by the mathematical model. In this work, the NIST cone calorimeter provided mass loss data and the LIFT apparatus was used to measure flame spread parameters. All cable fire data were obtained over a range of imposed flux. Bench-scale measurement of toxic potency of cable smoke was obtained; in some cases, full-scale smoke potency data were obtained as well. The modeling was done by modifying a room fire code (Harvard V) to allow for cable fires. This involved specific calculation of the incident flux to substrates in the hot upper layer of a room fire. Once the flux to a cable bed could be predicted, it was possible to calculate the rate of smoke evolution from the cables, making use of the small-scale test data described above. In a full-scale test of the method, good agreement between predicted and observed mass loss was obtained.

The methodology was then extended to a series of four cables in two fire scenarios similar to burn studies carried out by the U.S. Navy. The predicted rankings of the cables in these two scenarios were compared with the rankings of the cables by: (1) a toxic potency test; (2) results of a toxic potency test adjusted by the amount of cable present in each case; and (3) a new smoke toxicity test, which makes some allowance for the fire properties of the material. It was found that the bench-scale toxic potency measurements were not good indicators of full-scale performance.
Investigation of the Dual LC50 Values in Woods Using the University of Pittsburgh Combustion Toxicity Apparatus
Authors: Norris JC
Published: March 2009

Dual LC50 values for red oak (8 and 30 g) were observed in the combustion toxicity testing using the University of Pittsburgh combustion toxicity (UPITT) apparatus. No report of any material displaying a dual LC50 value had been made prior to now.

The National Forest Products Association became interested in knowing whether this was an anomaly of red oak or a property of other materials. A probative investigation was initiated to determine the existence and extensiveness of a dual LC50 value phenomenon using the UPITT apparatus. Since red oak was the first reported to have a dual LC50 value, other woods were selected for testing. White oak, southern pine, and Douglas fir were chosen.

Another objective of the investigation was to determine if there were analytical characteristics of thermal decomposition that would correlate with the LC50 values. Attempts to correlate the maximum concentrations and concentration x time (Ct) products of carbon monoxide, the ratio of carbon dioxide to carbon monoxide, and maximum ∂ temperature area with the LC50 values were made.

Three LC50 values were found for red oak (8.48, 15.0, 29.2 g) and southern pine (7.34, 12.39, 20.62 g), while one LC50 value was found for white oak (36.52 g) and Douglas fir (25.38 g). Maximum carbon monoxide concentrations reached a plateau and offered no correlation with the LC50 values. The Ct products of carbon monoxide did fluctuate but did not clearly correlate with the LC50 values. For red oak, ratios of carbon dioxide to carbon monoxide demonstrated a very good correlation with its LC50 values, but this was not so for the other woods. The maximum ∂ temperature area indicated that there was a continuous change in burning characteristics as the specimen weight increased, but it did not correlate with the LC50 values.

These data suggest that multiple LC50 values cannot be strictly related to nonflaming and flaming modes or char formation. Therefore, until an explanation for the multiple LC50 values is known, there remains the possibility that other products could also exhibit this phenomenon.
Smoke Characterization in Enclosure Environments
Authors: Newman JS
Published: March 2009

Experimental results from fire tests conducted with well-defined fire sources in large enclosures are presented which demonstrate the applicability of previously derived relationships to heat/smoke transport and smoke characterization within enclosure environments. Smoke concentrations are found to be conserved quantities which are readily predicted from fire source quantification. While the impact of forced ventilation needs to be further addressed, ventilation is shown to have a significant effect on fuel combustion chemistry.
Correlation of Wood Smoke Produced from NBS Smoke Chamber and OSU Heat Release Apparatus
Authors: Tran HC
Published: March 2009

In this study, we examined smoke generation from red oak and Douglas-fir plywood using the National Bureau of Standards (NBS) smoke density chamber in the smoldering mode at 2.0, 2.5, and 3.0 W/cm2 of heating flux. The data included optical density and particulate (soot) mass concentration, both as a function of time and heating flux. Data from the NBS chamber were compared to data from a dynamic smoke measurement apparatus, the Ohio State University (OSU) calorimeter. Because of basic differences between the NBS chamber and the OSU apparatus and between the units of measurement used in these methods, the results were reduced to a common unit, particulate mass per unit area of exposed specimen surface. Comparison of the data at 2.5 W/cm2 of heating flux showed reasonable agreement.
The Use of Medium-Scale Experiments to Determine Smoke Characteristics
Authors: Fleischmann CM , Dod RL , Brown NJ , Novakov T , Mowrer FW , Williamson RB
Published: March 2009

A series of medium-scale smoke experiments were conducted at the University of California, Berkeley. Representative fuels, such as wood, asphalt roofing shingles, and liquid hydrocarbons, were burned as medium-scale fuel packages in the open, with no restriction on the ventilation. For some of the fuels, the experiments were also conducted in a burn room under limited ventilation conditions. The effects of different combustion conditions resulting from differences in fuel composition, geometry, and ventilation were determined.

Smoke emission factors measured for burning wood under well-ventilated conditions were in the range of 0.1 to 0.3%, but under limited ventilation conditions they increased an order of magnitude to the 2 to 3% range. Under well-ventilated conditions, the smoke emission factors measured for asphalt were in the 12% range and those for No. 2 fuel oil were in the 11% range. Burning in the compartment also affected the emission factors and smoke characteristics of fuel oil.

The results of the medium-scale experiments presented in this paper show that the smoke emission factors are not only dependent on the properties of a given fuel, but also on the environmental conditions under which the fuel was burned. Specifically, the influence of ventilation rate, fuel mass loss rate, temperature, and residence time are important. Although more research is required before a standardized medium-scale fire test to measure smoke production can be developed, the need for such a test standard is clearly demonstrated by these results.
Applications of Quantitative Fractography and Computed Tomography to Fracture Processes in Materials
Authors: Antolovich SD , Gokhale AM , Bathias C
Published: March 2009

An overview of recent developments in quantitative fractography (QF) and computed tomography (CT) is presented with emphasis on applications of these tools to failure analysis and the identification of fundamental fracture processes. QF yields information concerning the geometric attributes of the microstructural features on the fracture surface and quantitative descriptors of the fracture surface geometry. By way of example, this methodology is applied to the case of a composite fabricated from an Al/Li matrix and alumina (Al2O3) fibers to delineate those defects which play the most important role in the fracture process.

The internal damage state of a material can be studied by CT; such information is not accessible through conventional fractographic approaches. CT results for damage detection are given for graphite/epoxy and metal-matrix composites. New applications of CT to address important unanswered questions in the fracture field are suggested.

Integration of QF, stereology, and CT has the potential to evolve into a very powerful method for the study of failure processes in all classes of materials.
Relationships Between Fractographic Features and Material Toughness
Authors: Harvey DP , Jolles MI
Published: March 2009

The fracture surfaces of HY-100 steel and 2024 aluminum tensile specimens with differing gage lengths and gage diameters were examined using scanning electron microscopy. Relationships were found between various fractographic features and the toughnesses of the specimens as quantified by the global critical strain energy density, wc, which is a measure of the work necessary to fail a material specimen by monotonic loading. In both test materials, correlations were made between the percentage of the fracture surface characterized by a particular fracture mode and the toughness of a given specimen. Correlations could also be made between the toughness of a specimen and other fractographic features such as the linear microvoid density or the aspect ratio of microvoids. It was found that both the character of the fracture surfaces and the specimen toughnesses were dependent on the history of the triaxiality of the stress-strain state which in turn was dependent on the gage geometries of the specimens. These results indicate that quantitative interrelationships between the micromechanical behavior and the global response of a specimen may be derived through the concepts employed in this investigation.
Fractographic Study of Isolated Cleavage Regions in Nuclear Pressure Vessel Steels and Their Weld Metals
Authors: Zhang XJ , Kumar A , Armstrong RW , Irwin GR
Published: March 2009

For heavy-section steels and weld metals used in nuclear reactor vessels, a sound understanding of fracture toughness in the transition range is needed. Fractographic studies of various kinds have been helpful. The results given in this paper indicate that the high local stress necessary to initiate cleavage is provided by brittle separations of closely spaced particle arrays, termed “particle clumps,” and, occasionally, in low-carbon weld metal by fracture of individual silicate particles 2 to 3 μm in size. These features, however, are far too numerous to account for the “rare event” nature of cleavage initiation in small-specimen tests. The increase of fracture toughness with test temperature across the transition temperature range is accompanied by an increase in size of late-breaking connections. This may be largely because of an increase with temperature of resistance to smooth passage of cleavage through grain boundaries.
Cracking Mechanisms for Mean Stress/Strain Low-Cycle Multiaxial Fatigue Loadings
Authors: Kurath P , Fatemi A
Published: March 2009

Observations of the orientation of crack formation and growth in wrought metals have been the basis for many shear strain-based low-cycle multiaxial critical plane fatigue damage models. One common factor with most of these models is that they consider a maximum shear amplitude often modified by a stress or strain, or both, normal to the maximum shear orientation. Considering the variety of multiaxial fatigue loadings, one factor that can drastically influence fatigue damage is mean stress/strain. Critical shear strain-based approaches using only modifying normal strain terms cannot account for the decreased damage observed when mean stresses relax, as they often do for constant amplitude low-cycle loadings. An alternate fatigue damage criterion, employing the maximum stress normal to the shear orientation, was recently proposed to account for this effect.

The importance of mean stresses/strains has been demonstrated with uniaxial tests. To verify the validity of the proposed criterion, twelve multiaxial loadings with mean stress, mean strain, or both are investigated employing combinations of axial-torsion and biaxial-tension. Surface crack orientation and fracture surface features are used to demonstrate that the terms employed in the mathematical formulation of the damage parameter are appropriate for the fatigue characterization of SAE 1045 steel and Inconel 718 at room temperature. Correlation of the physical fatigue damage mechanism with the modeling parameter terms results in increased confidence when attempting to predict the fatigue lives for other stress-strain states.
Corrosion Fatigue Crack Arrest in Aluminum Alloys
Authors: Wanhill RJH , Schra L
Published: March 2009

The economic life of airframes is largely determined by widespread initiation and growth of fatigue cracks at low stress intensities. Any factor reducing the low stress-intensity fatigue damage rate could, if controllable, increase the structural durability. One such factor is corrosion fatigue crack retardation and arrest. This was investigated for two high-strength aluminum alloys. Results indicate that two mutually competitive processes, hydrogen embrittlement and crack-tip blocking by corrosion products, have opposing effects on low stress-intensity fatigue. Crack blocking is dominant at the lowest stress intensities. Prospects for enhancing corrosion fatigue crack arrest are reasonable. It is suggested that multifunctional inhibitors could be added to the environment and metal surface treatments to promote corrosion product buildup and prevent hydrogen entry at the crack tip.
The Nature of the Immediate Reaction of Lime in Treating Soils for Road Construction
Authors: Verhasselt AF
Published: March 2009

It is now well-known that the geotechnical characteristics of wet cohesive soils are improved rapidly by adding lime (immediate effects) and that, subsequently, the mechanical characteristics of the compacted mixture generally develop in course of time (long-term effects). Whereas the pozzolanic nature of the slow reactions which result in long-term stabilization has been recognized, that of the immediate reactions still remains a point of controversy. By replacing lime with an equivalent amount of various mineral substances that may react in a similar manner, an attempt was made to obtain the same immediate effects as those produced by incorporating lime into wet, silty soil. The tested substances are: the hydroxides of strontium, barium, and sodium; the sulphates of calcium and aluminum; and calcium chloride.

The results show that the whole of immediate effects are obtained only when alkaline-earth ions (calcium, strontium, or barium) and hydroxyl ions are present at the same time. The hypothesis of the clay particles being linked as a result of physico-chemical adsorption of calcium hydroxide [Ca(OH)2] molecules or CaOH+ ions accounts well for the experimental observations.
Geotechnical Aspects of Leaching of Carbonates from Loessial Soils
Authors: Lamb RO
Published: March 2009

A study was made of the changes that occur in the geotechnical properties of loessial soils as a result of leaching of carbonates from the soil matrix. Profiles of particle-size distribution, carbonate content, preconsolidation pressure, undrained shear strength, and soil index properties are reported for loess deposits from a study area in the midcontinental United States. The study revealed that abrupt changes in clay content, carbonate content, and soil unit weight mark the boundary between leached and unleached portions of the deposits. The leached soils are soft, low-to-medium sensitivity clayey silts having undrained shear strengths as low as 8 kPa (1.2 psi). Leaching of carbonates was found to have increased the soil compression index by a factor of approximately 1.5 and reduced the undrained shear strength to less than one-half of the unleached soil. The mechanism of leaching and its effects on soil behavior are discussed.
Properties of a Treated-Bentonite/Sand Mix in Contaminant Environment
Authors: Wu JY , Khera RP
Published: March 2009

This research was conducted to study the changes in the properties of a mixture consisting of a chemically treated bentonite and sand in contaminant environments. Seven chemicals and their aqueous solutions were used. The effects of chemicals on the soils were stressed by directly introducing the chemicals to the soil specimens and observing the changes in their properties over one year.

Index tests included expansion and sedimentation tests. These tests provided a good measure of soil-chemical compatibility. Permeability measurements were made using a consolidometer permeameter, a flexible wall permeameter, and a triple ring permeameter which was developed for this research. The triple ring permeameter preserves the advantages and compensates for the limitations of other types of permeameters.

At consolidation pressures most likely to prevail in a slurry wall, the coefficient of permeability increased with increasing concentration of the chemicals. If a soil showed less expansion in a given liquid, its permeability was observed to increase more. Tests with aniline, phenol, toluene, and 1,1,1-trichloroethane did not yield any significant adverse effect on the permeability. The largest increases were observed with sodium hydroxide. With the same chemical solutions the increases in permeability were considerably smaller at a confining pressure greater than 100 kPa.

A four-phase soil system is proposed which incorporates the effect of semi-solid expanded volume of the bentonite. Two parameters, er and ef, are defined which can account for the changes in the expansion of the bentonite resulting from the influence of chemicals. The coefficient of permeability decreases with increases in er and ef values.
Effect of Sulfate Contamination on the Volume Change Behavior of Bentonite
Authors: Sridharan A , Rao SM , Gajarajan VS
Published: March 2009

This paper reports the influence of the principal anionic contaminant of acid rain deposition, namely sulfate ion, on the index, swelling, compressibility, and permeability characteristics of bentonite. Adsorption of sulfate ion leads to edge-to-edge bonding of bentonite particles; the occurrence of such a reaction mode throughout the clay matrix mobilizes an edge-to-edge flocculated fabric.

The liquid limit, swelling magnitude, and swelling pressure of bentonite clay markedly increases on sulfate adsorption. It is likely that, for the anion-treated clay, besides the growth of a diffuse double layer, water is imbibed by entrapment in the large void spaces of its flocculated structure, thus explaining the higher liquid limit and swelling magnitude of the treated specimen. Further, it is considered that the higher degree of particle interference associated with the flocculated fabric of the anion-treated clay resists particle rearrangement under external stresses more effectively than the oriented array of the natural clay, accounting for the larger swelling pressure of the former specimen. The greater particle interference associated with sulfate clay presumably is responsible for its consolidation curve being positioned above that of the natural clay.

The de/d (log p) versus pressure plots indicated higher compressions for the anion-treated clay at any given pressure increment. Possibly the anion-treated clay with a flocculated fabric undergoes greater particle reorientation under a given load, explaining its higher compressibility. The similar ranges of permeability coefficients observed for the natural and anion-treated clays suggested that the changes in clay fabric brought about by anion adsorption is not significant enough to influence the permeability of bentonite clay.
The Effect of Heating on Engineering Properties of Clays
Authors: Wang MC , Benway JM , Arayssi AM
Published: March 2009

The effect of heating on gradation, specific gravity, plasticity characteristics, swelling, and shear strength properties of a kaolin and a bentonite were investigated. The test soils were heated in an electric furnace to different temperatures up to 600°C. The engineering properties were determined by following ASTM standard procedures.

Results of the study indicate that heating the kaolin to 400°C reduces the amount of swelling drastically. Further heating to 500°C causes a formation of larger particles, a drop of specific gravity, a change into nonplastic, and a substantial increase in shear strength of the kaolin. For the bentonite, larger particles are found when heated to 600°C. Also, at 600°C, the clay becomes nonplastic and nonexpansive and undergoes a moderate strength gain. Based on the results of the investigation, it is concluded that heating can be used to stabilize soft clay deposits effectively.
Pore Water Extraction—Comparison of Saturation Extract and High-Pressure Squeezing
Authors: Iyer B
Published: March 2009

A study of the influence of the chemical environment on the engineering behavior of clayey soils warrants an understanding of the chemistry of the pore water present in the soil, together with the physico-chemical properties of the soil minerals. There are several techniques available for the extraction of the pore water from soil samples. Following a review of these techniques, two methods were considered suitable for the extraction of pore water from overconsolidated clay deposits. Pore water was extracted from several clay shales and bentonitic clays from western Canada using the high-pressure mechanical squeezing technique and the saturation extract technique during this study.

Based on the results of a previous study, it was expected that the pore water concentration determined using the saturation extract method would yield higher salt concentrations since the relationship between the concentration and the inverse of the water content is nonlinear. This phenomenon was confirmed in the present study. A comparison of the composition of the pore water extracted using the two techniques indicated that the saturation extract technique always yielded pore water with higher salt concentration. Based on this observation, it is concluded that the extrapolation of the pore water concentration at low moisture contents from known salt concentrations at higher (diluted) moisture contents should be viewed with caution.
Effects of Small Concentrations of Soluble Salts on Hydrometer Analysis
Authors: Picornell M , El-Jurf QS , Abd Rahim MA
Published: March 2009

Hydrometer analysis normally is performed on a soil specimen mixed with a chemical dispersant. During the performance of the test, the soil suspension is inspected visually to observe whether the suspension flocculates or remains stable. If flocculation occurs, despite the use of a dispersant, it is taken as an indication that the soil needs to be cleaned of excess soluble salts. This research was directed to study the interaction among the soil, the dispersant agent, and different soluble salts in a known and controlled environment. The results of this study show that visually apparent flocculation is just the last step in a process that starts affecting the results of the hydrometer analysis at much smaller salt concentrations than those corresponding to flocculation. These effects start taking place without any visual indication on the soil suspension. A method of screening soil samples that need to be cleaned is proposed based on the electrical conductivity of the pore water.
Evaluating the Accuracy of Thermomechanical Analysis Expansion Coefficient Measurements in a Wide Temperature Range
Authors: Matsumori N , Penn J , Nakamura N , Teramoto Y
Published: March 2009

The determination of the thermal expansion coefficient by thermomechanical analysis (TMA) is based on the measurement of the original length of the specimen, the expansion difference between the specimen and the holder material (reference material), and the specimen temperature. When the measurement error is considered, the first possible error is in the measurement of the temperature, and the second is in the measurement of the expansion difference. The error in the expansion difference is not significant for high expansion materials, such as polymers, but it is significant for low expansion materials such as ceramics. For material with a low thermal expansion, three corrections are available to reduce measurement errors for improved accuracy in the linear thermal expansion coefficient determinations.
A New Thermodilatometric Instrument for Thin Metallic Ribbons
Authors: Etchessahar E , Harmelin M , Debuigne J
Published: March 2009

A thermodilatometer was designed allowing metallic specimens in the form of thin ribbon to be heated at slow heating rates (1 to 5°C min-1) from room temperature up to 1000°C in an ultra-high vacuum (10-7 Pa). This dilatometer is a direct type and highly sensitive; amplification coefficient is 25 000. The transparent silica specimen holder is of the tensile type and allows the specimen to be fixed in a unique plane of the space. The specimen is 40 mm in length and ≈50 μm thick. A tensile stress of ≈5×104 Pa is applied during the experiment. One or more strips can be used for each experiment.

This device was used for studying metallic glasses: Fe78B13Si9 and CuxZr(100-x) (x = 33, 40, and 46). Thermal expansion coefficients were determined on heating and cooling. Isothermal annealings were also performed in situ in the dilatometer. On heating, the “as-quenched” ribbons, structural relaxation, Curie point, glass transition, and crystallization are successively evidenced on the dilatometric curves. Structural relaxation results in a progressive and small shrinkage of the specimens (ΔL/L < -4 × 10-4). Curie point results in sharp shrinkage. Glass transition is manifested by the creep of the specimen (ΔL/L ≈ +2.0 × 10-3), and crystallization of the amorphous phase results in a large shrinkage (ΔL/L ≈ - 1.00 × 10-3).

Relaxation rate, Curie point, glass transition, and crystallization of the specimens were also determined by differential scanning calorimetry (DSC). The irreversibility of structural relaxation below glass transition is well evidenced by DSC and thermodilatometry.
Thermomechanical Analysis: Advances in the State of the Art
Authors: Sauerbrunn SR , Gill PS
Published: March 2009

This presentation will describe the new DuPont 2940 thermomechanical analyzer (TMA). The 2940 TMA is a thermal analysis and mechanical characterization tool that measures the mechanical properties of a material as a function of time, temperature, and force. The instrument offers all of the traditional capabilities of TMA, but with total automation, increased sensitivity and enhanced force control. Specimen measurement and dimension change are controlled by a stepper motor and linear variable differential transformer (LVDT).

Focusing on higher performance polymer systems, this presentation will explore their thermomechanical properties. Application techniques easily managed by TMA include the coefficient of thermal expansion (CTE), glass transition Tg, and three-point flexural bending. The influence of thermal history and processing effects on these properties will be reported on specific polymers and composites.
Characterization of Polymer Electrolytes by Simultaneous Thermomechanical Analysis and Dielectric Thermal Analysis Techniques
Authors: McGhie AR , Jones GK , Farrington GC , Paul E
Published: March 2009

High molecular weight poly(ethylene oxide) (PEO) and a polymer electrolyte based on PEO containing the divalent metal halide salt, NiBr2, have been characterized using simultaneous thermomechanical and dielectric thermal analysis. Simultaneous measurement on the same sample allows separation of effects caused by simple expansion or flow from those caused by chemical reaction or phase transition. In fresh “as cast” samples, particularly under low load conditions, unexpectedly large expansions have been observed below room temperature on passing through the glass transition, and contractions have been seen on melting of pure PEO phases in both systems. Normal behavior, however, is observed after a sample has been melted and allowed to cool in the TMA. In NiBr2PEO8, a very large transitory expansion, up to 50%, has been observed well above the crystalline PEO melting temperature that appears to correlate with precipitation of the metal salt from solution.
Compositional Effects of Fiber Reinforced Composites on the Coefficient of Thermal Expansion
Authors: Adams RD
Published: March 2009

A McLean-Anderson experimental design for mixtures was used to design formulations for an automotive grade sheet molding compound (SMC). With the use of the Scheffe special cubic model, a predictive equation has been calculated to predict the coefficient of linear thermal expansion (CLTE) for an automotive grade SMC. The experimentally designed formulations included four control factors: resin, initiator, filler, and glass. The range levels were chosen based on the criteria for an automotive grade SMC. CLTE predicted values versus observed values have residuals ranging from 0.03 to 14.9% deviation based on four test formulations. Qualitative predictions were determined based on experimental work from various types of resin and glass.
In-Plane and Out-of-Plane Coefficient of Thermal Expansion Characterization of New High-Performance Printed Circuit Boards Using Dilatometer and Thermomechanical Analysis
Authors: Ibrahim AM , Klemens ML , Cozzo TF
Published: March 2009

This paper provides both in-plane and out-of-plane coefficient of thermal expansions (CTEs) of a high-performance QUATREX 5010 epoxy/Kevlar-120 fabric composite printed circuit board (PCB). Although both a quartz push-rod dilatometer and a thermomechanical analyzer (TMA) were used to measure the in-plane CTEs, the results indicate that the dilatometer is a better choice for accurate, precise determinations, especially for Kevlar/epoxy composites that had a CTE of 3.5 ppm/°C in the x and y direction. Based on our past experience testing various composite PCB materials based on E-glass, quartz, and Kevlar reinforcements, epoxy, polyimide, BT/epoxy, cyanate ester, and so forth, we recommend the dilatometer for accurately measuring the in-plane CTEs of Kevlar- and quartz-reinforced PCBs, which generally are below 9 ppm/°C. The TMA method, which is a faster and easier method than the dilatometer method, can be used reliably for accurately measuring the in-plane CTEs of E-glass-reinforced PCBs, which generally range from 12 to 16 ppm/°C.
Asphalt Cement Characterization by Thermomechanical Analysis
Authors: Lee D-Y , Enustun BV , Kim S-S
Published: March 2009

Thermomechanical analysis (TMA) techniques were used to characterize 60 original and aged asphalt cements. The objectives were to find better methods to characterize asphalts at low temperatures, to predict low-temperature cracking potentials, and to develop correlations between thermal properties of asphalts and their field performance for specification purposes.

A DuPont 943 Thermomechanical Analyzer was used in conjunction with a DuPont 1090 Thermal Analyzer Programmer. Glass transition temperatures of some asphalts, both original and aged, were also determined by both thermomechanical and differential scanning calorimetry (DSC) techniques. Although a number of test variables were examined, the results presented for TMA were run under expansion mode between -70 and 25°C, and those presented for DSC were obtained by scanning between -80 and 80°C, both at heating rate of 5°C per min. Thermal analysis results were correlated with Theological properties and molecular size distribution of asphalts based on high performance gel permeation chromatography (HP-GPC) profiles.

Glass transition temperatures varied between -22.5 and -35.0°C for original asphalts and between -22.0 and -37.0°C for aged asphalts, depending on viscosity grade, source, and rate of heating. Reasonable correlations were obtained between glass transition temperature determined by DSC and TMA methods. It was also found that TMA parameters correlated with ring-and-ball softening point, predicted cracking temperature, temperature corresponding to critical stiffness of 138 MPa (20 ksi) at long loading time, and molecular size distribution data.