Comparison of the dry densities of highly compacted bentonites

Clay Minerals ◽  
2013 ◽  
Vol 48 (1) ◽  
pp. 105-115 ◽  
Author(s):  
S. Kaufhold ◽  
M. Klinkenberg ◽  
R. Dohrmann
Keyword(s):  
Water Content ◽  
Particle Density ◽  
Swelling Pressure ◽  
Total Porosity ◽  
Dry Density ◽  
Uptake Capacity ◽  
Geotechnical Parameters ◽  
Water Uptake Capacity ◽  
Barrier Performance ◽  
High Level

AbstractBentonites are in worldwide use as candidate materials for the encapsulation of high-level radioactive waste (HLRW). To effectively seal waste canisters, bentonite is compacted to bentonite blocks which can be used to build a wall around the canisters. Compaction significantly improves the swelling pressure, which is currently considered as one of the most important parameters for assessing barrier performance. Most of the studies on compressibility of bentonites consider a few different materials only, which does not lead to a general understanding of bentonite performance. In order to identify the actual compressibility differences of different bentonites, a sizeable set of well characterized materials was investigated with respect to the dry densities after compaction.Different results were obtained for bentonites that had been dried and bentonites that were equilibrated at 70% r.h. (relative humidity) prior to compaction. The dry density of dried bentonites depends on total porosity and particle density. However, the dry density of microporous bentonites depends on the microporosity rather than total porosity because microporosity is not reduced upon compaction. On the other hand, for the samples previously equilibrated at 70% r.h., the water content is most important. However, the water content, i.e. the water uptake capacity at 70% r.h., in turn largely depends on the CEC but also on microporosity. Therefore, under a given load, the 36 bentonites studied showed a significant range of resulting dry densities, depending on water content, CEC and porosity.In conclusion, for a given bentonite, the dry density after compaction explains some geotechnical parameters such as the swelling pressure. However, for reasons explained in the present study, the dry density cannot be generally used to predict these parameters.

Experimental study on swelling characteristics of compacted bentonite

1994 ◽  
Vol 31 (4) ◽  
pp. 478-490 ◽  
Author(s):  
Hideo Komine ◽  
Nobuhide Ogata
Keyword(s):  
Water Content ◽  
Nuclear Waste ◽  
Volumetric Strain ◽  
Swelling Pressure ◽  
Dry Density ◽  
Initial Water Content ◽  
Initial Water ◽  
Compacted Bentonite ◽  
Swelling Characteristics ◽  
High Level

Compacted bentonites are attracting greater attention as back-filling (buffer) materials for repositories of high-level nuclear waste. However, since there are few studies about the swelling characteristics of compacted bentonites, it is first necessary to clarify the fundamental swelling characteristics in detail. For this purpose, various laboratory tests on the swelling deformation and swelling pressure of compacted bentonites were performed and the results analyzed. The following conclusions were drawn from the study. (i) The curve of swelling deformation versus time is strongly dependent on the initial dry density, vertical pressure, and initial water content. The maximum swelling deformation, however, is almost independent of initial water content, and the maximum swelling deformation increases in proportion to the initial dry density, (ii) The maximum swelling pressure increases exponentially with increasing initial dry density, whereas the maximum swelling pressure is almost independent of initial water content. (iii) The swelling mechanism of compacted bentonite was considered on the basis of the swelling behavior of swelling clay particles such as montmorillonite. Furthermore, a model of the swelling characteristics and a new parameter (swelling volumetric strain of montmorillonite), which were able to evaluate the swelling characteristics of compacted bentonite, were proposed. Key words : bentonite, laboratory test, nuclear waste disposal, swelling deformation, swelling pressure.

scholarly journals Thermal Conductivity of Compacted GO-GMZ Bentonite Used as Buffer Material for a High-Level Radioactive Waste Repository

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yong-Gui Chen ◽  
Xue-Min Liu ◽  
Xiang Mu ◽  
Wei-Min Ye ◽  
Yu-Jun Cui ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Radioactive Waste ◽  
Water Content ◽  
Radioactive Waste Disposal ◽  
Dry Density ◽  
Gmz Bentonite ◽  
High Level Radioactive Waste ◽  
Buffer Material ◽  
High Level ◽  
Crucial Parameter

In China, Gaomiaozi (GMZ) bentonite serves as a feasible buffer material in the high-level radioactive waste (HLW) repository, while its thermal conductivity is seen as a crucial parameter for the safety running of the HLW disposal. Due to the tremendous amount of heat released by such waste, the thermal conductivity of the buffer material is a crucial parameter for the safety running of the high-level radioactive waste disposal. For the purpose of improving its thermal conductivity, this research used the graphene oxide (GO) to modify the pure bentonite and then the nanocarbon-based bentonite (GO-GMZ) was obtained chemically. The thermal conductivity of this modified soil has been measured and investigated under various conditions in this study: the GO content, dry density, and water content. Researches confirm that the thermal conductivity of the modified bentonite is codetermined by the three conditions mentioned above, namely, the value of GO content, dry density, and water content. Besides, the study proposes an improved geometric mean model based on the special condition to predict the thermal conductivity of the compacted specimen; moreover, the calculated values are also compared with the experimental data.

Bentonites -

2021 ◽  
Author(s):  
Wen-An Chiou ◽  
Helmut Coutelle ◽  
Andreas Decher ◽  
Michael Dörschug ◽  
Reiner Dohrmann ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Bentonite Clay ◽  
Drilling Mud ◽  
Uptake Capacity ◽  
Water Uptake Capacity ◽  
High Level Nuclear Waste ◽  
And Performance ◽  
Swelling Clay Minerals ◽  
High Level ◽  
And Control

<p><b>Bentonites</b> are rocks mostly consisting of swelling clay minerals. They were first described from the Cretaceous Benton Shale near Rock River, Wyoming, USA. </p> <p> Because of their useful properties (e.g. highly adsorbent, cation exchanging, swelling), bentonites have many uses, in industry (among them as drilling mud, purification agent, binder, adsorbent, paper production), culture (for e.g. pottery) and medicine/cosmetics/cat litter, civil engineering, and in the future even in the disposal of high-level nuclear waste. </p> <p> Particular chemical characteristics of bentonite clay minerals are rather variable but critically determine their suitability for a particular application. </p> <p> The 15 specialist authors discuss bentonite terminology, classification and genesis and use in eight chapters. Individual chapters deal with the methods bentonites are analysed with, their properties and performance in terms of parameters such as cation exchange capactiy, rheology, coagulation concentraion, water uptake capacity, free swelling, and electrical resistivity (amongst others). </p> <p> A chapter is dedicated to the sources of bentonites, the technology employed to produce them, and how quality control is carried out both in the mine and the laboratory. A further chapter is dedicated to methods of processing the mined material, different activation methods, drying, grinding, and purification. </p> <P> Use cases for bentonites are discussed in a chapter of its own. References, a section on norms and standards, and a list of abbreviations complete the text. </p> <p> The volume addresses students, researchers, and professionals in the mineral industry dealing with bentonite and their clay-mineral constituents, quality assessement and control, and persons that use bentonites in their products. </p>

scholarly journals Distinguishing between more and less suitable bentonites for storage of high-level radioactive waste

Clay Minerals ◽  
2016 ◽  
Vol 51 (2) ◽  
pp. 289-302 ◽  
Author(s):  
S. Kaufhold ◽  
R. Dohrmann
Keyword(s):  
Hydraulic Conductivity ◽  
Radioactive Waste ◽  
Swelling Pressure ◽  
Point Of View ◽  
Dry Density ◽  
Swelling Clay ◽  
High Level Radioactive Waste ◽  
Key Issues ◽  
The Individual ◽  
High Level

AbstractOne of today's big challenges is to store safely the increasing amount of high-level radioactive waste (HLRW) in the world. In some of the concepts devised for this challenge, bentonite, a natural swelling clay, plays a key role in encasing the canisters containing the waste. The use of bentonite as a geotechnical barrier in HLRWrepositories is a new venture; specifications to ensure either optimum performance or that a minimum standard is reached at least do not exist yet. The present study summarizes relevant research and discusses possible HLRW-bentonite specifications. The importance of these specifications for any given repositories has to be assessed on a case by case basis, depending on the concept being employed and any special circumstances for the individual repositories.Ten key issues were identified which were used to discuss bentonite specifications. In some of these key issues the optimum bentonite performance depended more on processing and production (compaction) than on the bentonite type (e.g.swelling pressure and thermal conductivity). In contrast, in some of the other key issues, the type of bentonite was found to influence possible specifications: the bentonite should not alter its mineral composition or its geotechnical parameters such as the swellability. Therefore, the bentonite should contain neither soluble nor reactive phases (e.g.organic matter, pyrite, gypsum). The structural Fe content of the smectites should be small because of the lesser stability and greater reactivity of the Fe-rich bentonites. Also, a large layer-charge density of the swelling clay minerals leads to less corrosion at the iron–bentonite interface (relevant if iron canisters are used). The hydraulic conductivity and swelling pressure can be tailored by compaction of the bentonite resulting in different dry densities. From an engineering point of view, a bentonite with least dependence of the hydraulic conductivity/swelling pressure on the dry density would be best. Using a bentonite which has been investigated extensively over many years means less uncertainty compared to unknown materials.

scholarly journals Geotechnical Parameters of Alluvial Soils from in-situ Tests

2012 ◽  
Vol 59 (1-2) ◽  
pp. 63-81
Author(s):  
Zbigniew Młynarek ◽  
Katarzyna Stefaniak ◽  
Jędrzej Wierzbicki
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Particle Density ◽  
Construction Material ◽  
Alluvial Soil ◽  
Undrained Shear Strength ◽  
In Situ Tests ◽  
Geotechnical Parameters ◽  
Earth Construction ◽  
Undrained Shear

Abstract The article concentrates on the identification of geotechnical parameters of alluvial soil represented by silts found near Poznan and Elblag. Strength and deformation parameters of the subsoil tested were identified by the CPTU (static penetration) and SDMT (dilatometric) methods, as well as by the vane test (VT). Geotechnical parameters of the subsoil were analysed with a view to using the soil as an earth construction material and as a foundation for buildings constructed on the grounds tested. The article includes an analysis of the overconsolidation process of the soil tested and a formula for the identification of the overconsolidation ratio OCR. Equation 9 reflects the relation between the undrained shear strength and plasticity of the silts analyzed and the OCR value. The analysis resulted in the determination of the Nkt coefficient, which might be used to identify the undrained shear strength of both sediments tested. On the basis of a detailed analysis of changes in terms of the constrained oedometric modulus M0, the relations between the said modulus, the liquidity index and the OCR value were identified. Mayne’s formula (1995) was used to determine the M0 modulus from the CPTU test. The usefullness of the sediments found near Poznan as an earth construction material was analysed after their structure had been destroyed and compacted with a Proctor apparatus. In cases of samples characterised by different water content and soil particle density, the analysis of changes in terms of cohesion and the internal friction angle proved that these parameters are influenced by the soil phase composition (Fig. 18 and 19). On the basis of the tests, it was concluded that the most desirable shear strength parameters are achieved when the silt is compacted below the optimum water content.

scholarly journals Factors affecting the swelling pressure for Jerash expansive soil

2021 ◽  
Vol 3 (2) ◽  
pp. 44-51
Author(s):  
Talal Masoud ◽  
Abdulrazzaq Jawish Alkherret
Keyword(s):  
Water Content ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Swelling Pressure ◽  
Dry Density ◽  
Initial Water Content ◽  
Content Increase ◽  
Initial Water ◽  
Factors Affecting ◽  
Water Content Increase

  In this study for factors effecting the swelling pressure of jerash expansive soils were investigated in this study, effect of initial dry density and effect of initial water content on the jerash expansive soil were investigated.It show that as the initial dry density decrease from 1.85 gm/cm3  to1.25 gm/cm3 , the swelling pressure also decrease are from 3.1  to 0.25gm/cm2   also it show that as the initial water content increase from 0%to 15% , the swelling pressure of jerash expansive soil decrease from 2.65 gm/cm2  to 1.35 gm/cm2  .  

scholarly journals 10-Years Studies of the Soil Physical Condition after One-Time Biochar Application

Agronomy ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1589
Author(s):  
Jacek Pranagal ◽  
Piotr Kraska
Keyword(s):  
Physical Properties ◽  
Water Content ◽  
Physical Condition ◽  
Particle Density ◽  
Total Porosity ◽  
Good Method ◽  
Soil Physical Properties ◽  
Waste Biomass ◽  
Water Capacity ◽  
Air Capacity

The ten-year experiment on the soil physical properties of biochar-amended Podzol was studied. Biochar was applied to the soil in the following rates: treatment BC10—10 Mg × ha−1, treatment BC20—20 Mg × ha−1, treatment BC30—30 Mg × ha−1 and treatment BC0—Control (soil without the addition of biochar). Biochar was mixed the soil arable layer (0–20 cm). Soil samples were collected ten times, once a year—after harvest rye. They were taken from layers: 0–10 cm and 10–20 cm, in six replicates, using 100 cm3 metal cylinders. The soil physical properties were determined: particle size distribution, particle density, bulk density, total porosity, air capacity and permeability (at −15.5 kPa), water content at sampling, field water capacity (at −15.5 kPa), available and unavailable water content, and the ratio of field water capacity and total porosity was calculated. It was found that biochar application causes changes in the soil physical condition. The soil density decreased, while the porosity, aeration and water retention increased; the ratio of field water capacity and total porosity was favorable. These changes cannot be considered as permanent. Most of the analyzed properties showed a durability of no more than 3–4 years. We found that biochar incorporation into soil is a good method for environmental management of waste biomass.

Swelling Behaviour of GMZ Bentonite

2013 ◽  
Vol 671-674 ◽  
pp. 1756-1760
Author(s):  
De An Sun ◽  
Hai Bo Lv ◽  
Chang Fu Wei
Keyword(s):  
Initial Conditions ◽  
Matrix Material ◽  
Swelling Pressure ◽  
Dry Density ◽  
Gmz Bentonite ◽  
Swelling Behaviour ◽  
Deep Geological Disposal ◽  
Backfill Materials ◽  
Swelling Characteristics ◽  
High Level

Gaomiaozi (GMZ) bentonite has been chosen as a matrix material of buffer/backfill materials in the deep geological disposal to isolate the high level radioactive waste in China. Swelling characteristics of GMZ bentonite and its mixtures with sand wetted with water were studied by experimental methods. The tests result shows that the relation between void ratio and the swelling pressure of compacted GMZ bentonite-sand mixtures at full saturation is independent on the initial conditions such as initial dry density and water content, and dependent on the ratio of bentonite to sand. An empirical equation is proposed to predict the swelling deformation and pressure of the mixtures with different densities and bentonite/sand ratios.

scholarly journals Strengthening of Porcine Plasma Protein Superabsorbent Materials through a Solubilization-Freeze-Drying Process

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 772
Author(s):  
Estefanía Álvarez-Castillo ◽  
Carlos Bengoechea ◽  
Antonio Guerrero
Keyword(s):  
Water Uptake ◽  
Plasma Protein ◽  
Freeze Drying ◽  
Meat Industry ◽  
Drying Process ◽  
Uptake Capacity ◽  
Water Uptake Capacity ◽  
Protein Flour ◽  
Hydrophilic Materials ◽  
By Products

The replacement of common acrylic derivatives by biodegradable materials in the formulation of superabsorbent materials would lessen the associated environmental impact. Moreover, the use of by-products or biowastes from the food industry that are usually discarded would promote a desired circular economy. The present study deals with the development of superabsorbent materials based on a by-product from the meat industry, namely plasma protein, focusing on the effects of a freeze-drying stage before blending with glycerol and eventual injection molding. More specifically, this freeze-drying stage is carried out either directly on the protein flour or after its solubilization in deionized water (10% w/w). Superabsorbent materials obtained after this solubilization-freeze-drying process display higher Young’s modulus and tensile strength values, without affecting their water uptake capacity. As greater water uptake is commonly related to poorer mechanical properties, the proposed solubilization-freeze-drying process is a useful strategy for producing strengthened hydrophilic materials.

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