scholarly journals Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite—The Initial State and the State following Thermal Treatment at 200 °C

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 871
Author(s):  
František Laufek ◽  
Irena Hanusová ◽  
Jiří Svoboda ◽  
Radek Vašíček ◽  
Jan Najser ◽  
...  
Keyword(s):  
Radioactive Waste ◽  
Thermal Loading ◽  
Interlayer Space ◽  
Swelling Pressure ◽  
Liquid Limit ◽  
Detailed Knowledge ◽  
Initial State ◽  
Experimental Conditions ◽  
Swell Index ◽  
Thermally Treated

Bentonites are considered to be the most suitable materials for the multibarrier system of high-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representative of Czech Ca-Mg bentonites in this respect, it has been included in the Czech Radioactive Waste Repository Authority (SÚRAO) buffer and backfill R&D programme. Detailed knowledge of processes in the material induced by thermal loading provides invaluable assistance regarding the evolution of the material under repository conditions. Samples of both original BCV 2017 bentonite and the same material thermally treated at 200 °C were characterised by means of chemical analysis, powder X-ray diffraction, infrared spectroscopy, thermal analysis, cation exchange capacity, specific surface area (BET) measurements, the determination of the swell index, the liquid limit, the swelling pressure and water retention curves. The smectite in BCV 2017 bentonite comprises Ca-Mg montmorillonite with a significant degree of Fe3+ substitution in the octahedral sheet. Two main transformation processes were observed following heating at 200 °C over 27 months, the first of which comprised the dehydration of the montmorillonite and the subsequent reduction of the 001 basal distance from 14.5 Å (the original BCV 2017) to 9.8 Å, thus indicating the absence of water molecules in the interlayer space. The second concerned the dehydration and partial dehydroxylation of goethite. With the exception of the dehydration of the interlayer space, the PXRD and FTIR study revealed the crystallochemical stability of the montmorillonite in BCV 2017 bentonite under the selected experimental conditions. The geotechnical tests indicated no major changes in the mechanical properties of the thermally treated BCV 2017 bentonite, as demonstrated by the similar swelling pressure values. However, the variation in the swell index and the gradual increase in the liquid limit with the wetting time indicated a lower hydration rate. The retention curves consistently showed the lower retention capacity of the thermally treated samples, thus indicating the incomplete re-hydration of the thermally treated BCV 2017 exposed to air humidity and the difference in its behaviour compared to the material exposed to liquid water.

Behavior of clayey soils on drying–wetting paths

1993 ◽  
Vol 30 (2) ◽  
pp. 287-296 ◽  
Author(s):  
Jean-Marie Fleureau ◽  
Siba Kheirbek-Saoud ◽  
Ria Soemitro ◽  
Said Taibi
Keyword(s):  
Experimental Research ◽  
Negative Pressure ◽  
Unsaturated Soils ◽  
Liquid Limit ◽  
The Other ◽  
Clayey Soils ◽  
Initial State ◽  
Stress Increase ◽  
Negative Pressures ◽  
Clayey Materials

Experimental research was carried out on 11 different clayey materials to determine the main characteristics of the drying and wetting paths and the influence of initial state and other factors. Normally consolidated paths are shown to have a large saturated domain, in which a negative pressure is equivalent to an isotropic stress increase; such paths can be derived from correlations with the liquid limit. On the other hand, the behavior of overconsolidated or dried samples is largely dependent on the range of stresses and negative pressures. Key words : suction, unsaturated soils, drying, wetting, correlations, models.

A SURVEY OF THERMODYNAMIC PARAMETERS FOR SOLVOLYSIS IN WATER

1959 ◽  
Vol 37 (4) ◽  
pp. 803-824 ◽  
Author(s):  
R. E. Robertson ◽  
R. L. Heppolette ◽  
J. M. W. Scott
Keyword(s):  
Transition State ◽  
Activation Enthalpy ◽  
Detailed Knowledge ◽  
Standard State ◽  
Initial State ◽  
Enthalpy Of Activation ◽  
Halide Exchange ◽  
Hydrolysis Of Esters ◽  
Hydrolysis Of ◽  
Linear Correlations

A method is suggested for determining the standard state entropies [Formula: see text] of the transition state for the neutral hydrolysis of esters in water. This has required the development of methods for approximating initial state parameters where experimental data are lacking.Characteristic linear correlations between the entropy and enthalpy of activation are observed for hydrolysis in water, as well as for the bimolecular halide exchange reaction in acetone and for acid–base equilibria. Explanations are advanced to explain the observed trends.From the derived standard state entropies, a method for estimating the charge development in the transition state for the methyl and isopropyl halides is proposed. With this further detailed knowledge of the transition state in the methyl halide series, reasonable values of the activation enthalpy can be calculated from available thermochemical data.

Modeling Hydraulic Conductivity and Swelling Pressure of Several Kinds of Bentonites Affected by Salinity of Water

2010 ◽  
Author(s):  
Yukihisa Tanaka ◽  
Takuma Hasegawa ◽  
Kunihiko Nakamura
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Ground Water ◽  
Quantitative Evaluation ◽  
Coastal Area ◽  
Evaluation Method ◽  
Saline Water ◽  
Swelling Pressure ◽  
Compacted Bentonite ◽  
Swelling Characteristics

In case of construction of repository for radioactive waste near the coastal area, the effect of salinity of water on hydraulic conductivity as well as swelling pressure of bentonite as an engineered barrier should be considered because it is known that the hydraulic conductivity of bentonite increases and swelling pressure decreases with increasing salinity of water. Though the effect of salinity of water on hydraulic conductivity and swelling pressure of bentonite has been investigated experimentally, it is necessary to elucidate and to model the mechanism of the phenomenon because various kinds of bentonites may possibly be placed in various salinities of ground water. Thus, in this study, a model for evaluating hydraulic conductivity as well as swelling pressure of compacted bentonite is proposed considering the effect of salinity of water as follows: a) Change in number of flakes of a stack of montmorillonite because of cohesion. b) Change in viscosity of water in interlayer between flakes of montmorillonite. Quantitative evaluation method for hydraulic conductivity and swelling characteristics of several kinds of bentonites under saline water is proposed based on the model mentioned above.

scholarly journals Index Properties, Hydraulic Conductivity and Contaminant-Compatibility of CMC-Treated Sodium Activated Calcium Bentonite

2020 ◽  
Vol 17 (6) ◽  
pp. 1863
Author(s):  
Ri-Dong Fan ◽  
Krishna R. Reddy ◽  
Yu-Ling Yang ◽  
Yan-Jun Du
Keyword(s):  
Heavy Metals ◽  
Hydraulic Conductivity ◽  
Metal Concentration ◽  
Landfill Leachate ◽  
Liquid Limit ◽  
Fluid Loss ◽  
Swell Index ◽  
Flexible Wall ◽  
Lead Zinc ◽  
Calcium Bentonite

A typical sodium activated calcium bentonite (SACaB) was treated with carboxymethyl cellulose (CMC) polymer, called CMC-treated SACaB (CMC-SACaB), and it was investigated for its hydraulic conductivity and enhanced chemical compatibility. Index property and hydraulic conductivity tests were conducted on CMC-SACaB and SACaB with deionized water (DIW), heavy metals-laden water, and actual landfill leachate. Lead-zinc mixed (Pb-Zn) solution and hexavalent chromium (Cr(VI)) solution were selected as target heavy metals-laden water, and calcium (Ca) solution was tested for comparison purposes. The hydraulic conductivity (kMFL) was determined via the modified fluid loss (MFL) test. Liquid limit and swell index in DIW, heavy metal-laden water, and Ca solution increased with increasing CMC content. CMC treatment effectively decreased the kMFL of SACaB when exposed to Pb-Zn solutions with a metal concentration of 1 to 20 mmol/L and landfill leachate. An insignificant change in kMFL of CMC-SACaB occurred with exposure to Pb-Zn solutions with metal concentrations of 1 to 10 mmol/L, Cr(VI) and Ca solutions with metal concentration of 1 to 20 mmol/L, and landfill leachate. A slight increase in kMFL of CMC-SACaB was observed when Pb-Zn concentration increased to 20 mmol/L, and such an increment was more noticeable when the CMC content was lower than 10%. In the DIW, the measured kMFL values of CMC-SACaB and SACaB with a given range of void ratio were consistent with those obtained from the flexible-wall permeameter test.

Use of Natural Analog and Modeling Studies to Constrain the Effects of Magmatic Activity on Long-Term Geologic Repositories

1994 ◽  
Vol 353 ◽  
Author(s):  
Greg A. Valentine ◽  
N. D. Rosenberg ◽  
B. M. Crowe ◽  
F. V. Perry
Keyword(s):  
Radioactive Waste ◽  
Volcanic Eruption ◽  
Thermal Loading ◽  
Yucca Mountain ◽  
Temporal Scale ◽  
Magmatic Activity ◽  
Radioactive Waste Repository ◽  
Natural Analog ◽  
Waste Repository

AbstractExamples of the application of natural-analog studies to the estimation of the consequences of a volcanic eruption penetrating a radioactive waste repository are given, including the criteria for analog selection and new data from ongoing studies. Examples of early modeling results focusing on the spatial and temporal scale of subsurface processes are also provided. All of these examples are taken from studies of the potential Yucca Mountain repository, Nevada, but similar approaches could be applied in other areas. In addition, studies of subsurface processes initiated by magmatic events serve as useful analogs for repository thermal loading studies.

Effect of chemical stabilisation on index and engineering properties of a remoulded expansive soil

2021 ◽  
pp. qjegh2020-142
Author(s):  
E. Ramanjaneya Raju ◽  
B. R. Phanikumar ◽  
M. Heeralal
Keyword(s):  
Expansive Soil ◽  
Dry Weight ◽  
Liquid Limit ◽  
Strength Characteristics ◽  
Engineering Properties ◽  
Compaction Characteristics ◽  
Swell Index ◽  
Granulated Blast Furnace Slag ◽  
Free Swell ◽  
Furnace Slag

This note presents the effect of lime, cement, fly ash and ground granulated blast furnace slag (GGBS) on free swell index (FSI), liquid limit (LL), plasticity index (PI), compaction characteristics, hydraulic conductivity (k) and strength characteristics of an expansive soil. The effect of the above chemicals on California bearing ratio (CBR) was also presented. Lime content was varied as 0%, 1%, 2%, 4% and 6% and the amounts of other additives were varied as 0%, 5%, 10%, 15% and 20% by dry weight of the soil. FSI, LL and PI decreased significantly with increasing additive contents. Compaction characteristics also improved with increasing additive contents. Strength characteristics showed improvement at higher additive contents especially at higher curing periods. CBR (determined in soaked condition) also increased significantly with increasing additive contents.

Experimental Investigation on the Microstructural Properties of Black Cotton Soil Stabilized with Cinder (Scoria) Fines and Class-C Fly Ash

2021 ◽  
Vol 56 ◽  
pp. 95-110
Author(s):  
Biruk Ayehutsega ◽  
Eleyas Assefa ◽  
Costas Sachpazis
Keyword(s):  
Fly Ash ◽  
Experimental Studies ◽  
Engineering Application ◽  
Expansive Soil ◽  
Liquid Limit ◽  
Plasticity Index ◽  
Black Cotton Soil ◽  
Microstructural Properties ◽  
Swell Index ◽  
Class C

Black cotton soil is one of the significant problematic soil for any civil or geotechnical engineering application in the whole world. In the past several decades, different experimental studies have been carried out on the stabilization of expansive soil and different types of stabilizers like lime, Portland cement, cement fly ash, and lime fly ash were used and applied in highway and others construction. However, those traditional stabilizers are not environmentally friendly thus further scientific study is needed to minimize the percentage of carbon-based stabilizers. The fact that Ethiopia encountered major engineering problems due to these problematic soils many researchers have been conducted a vital study using traditional stabilizers for several years however there is no significant study on the microstructural properties of stabilized black cotton soil. In this study, a scoria fines and class c fly ash are used at different blended groups, for each group, the stabilizer content ranges from 10 to 30%. The liquid limit and plasticity index of the soil has been decreased with the increasing content of class c fly ash (FA) and cinder fines (CF). Especially after the soil treated with 25% of class c fly ash and 25% of cinder fines, the liquid limit has decreased by 51.61% and, the plasticity index by 78.61%, linear shrinkage by 66.58%, and the free swell index decreased by 78.9%. The CBR and UCS value has increased by 86.2% and 83.9%, respectively, and CBR swell reduced by 61.2% with increasing stabilizer content. The microstructural properties of Raw black cotton soil and samples that are selected based on strength and index properties (BCS+FA3, BCS+CF3, BCS+CF+FA3) were observed by Scanning electron microscopy (SEM) imagining device, and the result clearly shows the alteration in fabric and morphology of the sample. After treatment with class c fly ash and cinder fines, the laminated configuration of black cotton soil has changed to more flocculated and coherent mass. Also, the SEM image proves that cinder fines impart a mechanical bonding that forms well-developed floccules and a more porous nature. These types of particle arrangement and clay aggregation bring the improvement in index and strength properties.

scholarly journals Effect on the mechanical properties of sheet metals after the use of drawbeads in deep drawing

2018 ◽  
Vol 190 ◽  
pp. 05001 ◽  
Author(s):  
Harald Schmid ◽  
Marion Merklein
Keyword(s):  
Mechanical Properties ◽  
Sheet Metal ◽  
Deep Drawing ◽  
Optical Measurement ◽  
Detailed Knowledge ◽  
Complex Materials ◽  
Initial State ◽  
Blank Holder ◽  
Strip Drawing ◽  
Main Effects

The use of modern and more complex materials leads to a need for detailed knowledge and controlling of the material flow. Next to the blank holder force or the lubrication system, drawbeads are nowadays one common way to bring serial forming processes under control. Although drawbeads are already well investigated regarding their retention forces, the effect on the resulting mechanical properties after a drawbead passage is not analysed in detail yet. This work will show the influence of a common drawbead geometry used in forming processes on typical mechanical properties of sheet metal. Therefore, two different sheet metal materials are preloaded in a modified strip drawing test with industrial used drawbead geometry. In testing, three different pressure levels between 2.5 MPa and 7.5 MPa and three levels of drawing speed between 10 mm/s and 50 mm/s are combined to nine variations which will be examined. Afterwards, specimens are cut out by a laser cutting machine of the drawn strips. Those already preloaded and deformed specimens are then tested under standard conditions with the use of an optical measurement system. The results like tensile strength or elongation at fracture are compared to the initial state and each other and discussed with consideration of pressure and speed levels to work out the main effects. Those results are a contribution for the optimization of deep drawing simulations of parts including drawbeads or to evaluate the influence of drawbeads on forming processes to specify or even expand process limitations.

Liquid Chromatography in Migration Studies

1981 ◽  
Vol 11 ◽  
Author(s):  
Lars Carlsen ◽  
Walther Batsberg
Keyword(s):  
Liquid Chromatography ◽  
Radioactive Waste ◽  
Experimental Technique ◽  
Chemical Properties ◽  
Detailed Knowledge ◽  
Geochemical Environment ◽  
Physico Chemical ◽  
The Media ◽  
A Site ◽  
Sorption Characteristics

A detailed knowledge of the geochemical environment of a site for the disposal of radioactive waste is of fundamental importance. To evaluate the migration behaviour of radionuclides in geological media a series of data are needed, amongst others a number of physico-chemical properties of the media, such as permeability, porosity, dispersion-, diffusion-, and sorption characteristics. In this connection liquid chromatography appears to be advantageous as a facile experimental technique to obtain relevant data for these physico-chemical properties.

scholarly journals Numerische Simulation von Temperaturgradienten und thermisch induzierten Eigenspannungen in Natursteinplatten infolge von Sonneneinstrahlung / Simulation of Temperature Gradients and Stresses in Natural Stone Plates under Solar Radiation

1998 ◽  
Vol 4 (1) ◽  
pp. 53-72 ◽  
Author(s):  
H. Sadouki ◽  
F. H. Wittmann
Keyword(s):  
Solar Radiation ◽  
Thermal Loading ◽  
Swelling Pressure ◽  
Natural Stone ◽  
Maximum Temperature ◽  
Selective Absorption ◽  
Chemical Attack ◽  
Physical Attack ◽  
Thermal Dilatation ◽  
Micro Organisms

Abstract The interaction between micro-organisms and natural stone surfaces has been studied in great detail in the past. The destructive mechanisms of micro-organisms can be roughly subdivided into (a) chemical attack and (b) physical attack. Microorganisms may physically destroy the structure of stones by creating an inter-granular swelling pressure. Recently, it has been shown experimentally that black spots formed by yeast-like fungi lead to a local temperature increase by selective absorption of solar radiation. The maximum temperature observed for clean marble surfaces remained below the maximum temperature observed on inoculated surfaces. As a consequence, thermal dilatation of inoculated marble was shown to be more important. Destruction of the heated stone occurs predominantly if there exists a thermal gradient. In this paper, temperature distribution in clean and stained marble plates have been simulated numerically. Thermal eigenstresses have been determined. It is shown that tensile stresses of up to 5 N/mm2 can be expected. This may cause damage in weak zones of the surface. A sudden driving rain leads to much higher stresses. Cyclic thermal loading may eventually destroy the surface by fatigue.

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