Plastic Clay Research Articles

Characterization of Brazilian Northeastern plastic clays

Abstract Plastic clays are one of the main raw materials used in ceramic technology. However, there is a shortage of good quality plastic clays in the world for use in porcelain technology. The aim of this study was to characterize plastic clays from Northeastern Brazil. Chemical and mineralogical composition, particle size distribution, plasticity and green strength of the clays were determined. The analyzed clays were predominantly composed of kaolinite and quartz, and some contained smectite. The amount of iron oxide in the clays was higher than 1.0% and for some of them the values were higher than 3%; the liquid and plastic limits ranged from 22% to 48% and 10% to 32%, respectively. According to characterization data, three plastic clays had potential to be used as alternative ball clay, due to their plasticity and mineralogical characteristics.

Characterisation of the multi-scale fabric features of high plasticity clays

An investigation of the microstructural features of a high-plasticity clay, in both its natural conditions and reconstituted in the laboratory, is described. Scanning electron microscopy is used here to characterise the fabric at different magnifications, while image processing of the micrographs delivers a quantitative assessment of the fabric orientation. The results of energy-dispersive X-ray spectroscopy and swelling tests, as reported in a previous study by the authors, are used to characterise the bonding nature and strength, as well as mercury intrusion porosimetry to investigate clay porosimetry. Despite their identical composition, the natural and the reconstituted clay have experienced different deposition and loading history, generating different microstructural features that are shown to underlie their differences in state. For both clays, one-dimensional (1D) compression to medium–high pressures is seen to determine a well-oriented medium magnification fabric. However, larger-scale observations and the corresponding image processing results reveal non-uniform local fabric features, hence making fabric characterisation dependent on the scale of analysis and bringing about the issue of identifying the clay micro-scale representative element volume relating to the clay macro-behaviour. The micro-REV is identified for the clays under study and its connection with the macro-behaviour characterised. The microstructural evolution induced by 1D compression to very high pressures is shown to concern mainly the clay porosity and porosimetry, the fabric orientation being steady, thus explaining the isotropic hardening observed in laboratory tests.

Enhancement of Clay–Sand Liners Using Crushed Limestone Powder for Better Fluid Control

Tunnel boring machine (TBM)-crushed limestone material is a fine powder obtained during tunnel excavations. This material is proposed for use as smart filler in clay–sand liners, which include highly plastic clay and are typically used in waste containment applications and other fields. Replacing a part of bentonite in these liners with an inert, low plasticity material is an efficient way of controlling the compressibility and reducing the swelling index. The objective of this study was to test the water retention capacity under various mixture conditions. The soil–water characteristic curves for mixtures consisting of sand and 15% clay were investigated with regard to three main proportions: clay mixture consisting of one-third of TBM powder and two-thirds of bentonite, clay mixture consisting of two-thirds of TBM powder and one-third of bentonite, and a mixture consisting of only sand and bentonite. The geotechnical properties exhibited a clear improvement in the compressibility and swellability of the clay–sand liner owing to the addition of TBM-crushed limestone filler. The clay–sand mixtures were enhanced by adding crushed filler and could seal off the pores and voids, retain a satisfactory hydraulic conductivity, and prevent or minimize the flow through the layer. Scanning electron microscopy and X-ray investigations were performed for the TBM limestone powder material mixed with commercial bentonite.

Semi-supervised stacked autoencoder-based deep hierarchical semantic feature for real-time fingerprint liveness detection

The popularity of biometric authentication technology benefits from the rapid development of smart mobile devices in recent years, and fingerprints, which are inherent human traits and neither easily revealed nor deciphered, can be used for real-time individual authentication systems. However, the main security issue of real-time fingerprint authentication systems is that most fingerprint scanners are vulnerable to presentation attacks by artificial replicas, made from plastic clay, gelatin, silicon, wood glue, etc. One anti-spoofing attack scheme, called real-time fingerprint liveness detection (RFLD), has been proposed to discriminate live or fake fingerprints. Currently, to resolve the presentation attacks, most RFLD solutions all relied on handcrafted feature extraction and selection. The features extracted by manual method are shallow features of the samples; however, autoencoder can automatically learn deep hierarchical semantic features representation of the samples, thus replacing the operations extracted with hand-designed features. In this paper, we apply stacked autoencoder to RFLD to significantly lower the work-force burden of the feature extraction engineering, and our model consists of two parts: parameter pre-training based on unsupervised learning and FLD based on supervised learning. The performance has been verified on two public fingerprint datasets: LivDet 2011 and 2013, and the experimental results indicate that our proposed approach works well for RFLD as well as the detection performance is satisfactory.

Strength and micro-mechanism of MK-blended alkaline cement treated high plasticity clay

This paper focuses on the strength behavior and micro-mechanisms of treated high plasticity clay-mixtures with Metakaolin- (MK-) blended alkaline cement. The MK-blended alkaline cement was prepared by the alkaline activation of Ordinary Portland Cement (OPC) and MK blends, while the MK-based geopolymer and MK-blended cement were also prepared for comparison purpose. The results show that the unconfined compressive strength (UCS) of the clay treated by MK-blended alkaline cement increases with MK replacement at ranges of 30%. Meanwhile, the pore structure was significantly improved in terms of large pores transferring to the smaller size. The increase of MK replacement from 10% to 20% leads to the increase of UCS of the MK-blended alkaline cement treated clay mixture (L/S = 53.8%, 3.2 M) by 21.8%, and increase of pores ranging from 0.01 to 0.1 μm by 47.5% along with the decrease of pores ranging from 0.1 to 1 μm by 28.1%. This attributes to the notable bonding and filling effect by the coexistence of cementitious gels such as (N,C)-A-S-H and C-A-S-H gels, which differ to the hydration products from traditional OPC hydration. More significantly, the treated clay mixture with 60% MK replacement has the potential to reduce large portion of OPC, due to its appreciable strength of approximately 31.0% increase over the OPC treated clay-mixture.

Akkalkan deposit of bentonite clays (Southeast Kazakhstan): formation conditions and prospects for technological use

The article presents the results of the bentonite clays study of Akkolkanskoye deposit, located in South-Eastern Kazakhstan. Based on the mapping, four main types of bentonites were identified: light gray argillite-like clay; dark gray clay lamellar and crushed stone morphology; waxy light brown and pale yellow clay lamellar texture; black plastic clay. Mineralogical study of these varieties allowed to establish the relationship of crystal-morphological features of the main rock-forming mineral in clays with the conditions of their formation and with the technological properties of bentonite raw materials for use in various industries.

Determination of the adequate dosage of the soil-cement, using clay of high plasticity

The clay is used in the area of constructions, ceramics and industrial applications: insecticides, pharmaceutical industry, cosmetics and painting, for its physical and chemical properties that are suitable for different civil projects (roads, public services network, constructions); the dosage is a technique to modify and improve the conditions of the soil-cement in reference to the resistance, conditions of insolubility, impermeability, durability and appearance. In this study, high plasticity clay was evaluated through different laboratory tests (humidity test, soil liquid limit, plasticity index, granulometric analysis, California Bearing Ratio) for three samples and specifying the methodology used in each step, with the objective of knowing its structure and functioning in rural roads in combination with soil-cement, looking for a more profitable and lasting option in this sector, in order to benefit the people surrounding these sectors, improving the income of the sector and seeking to mitigate the environmental impact.

Feasibility study on the application of alum sludge (AS) as alternative landfill liner material in sustainable landfill infrastructure model: XRD and SEM analysis

The increasing number of Alum Sludge (AS) in water treatment plant (WTP) from water treatment process has been directed to the reduction of storage capacity for keeping of AS waste itself in the landfill. Other than disposed in the landfill site, this accumulated AS can be commercialized into a useful product such as landfill barrier. Conventionally, clay is used as the protection layer in the engineered sanitary landfill to reduce the leachate intrusion into groundwater. However, due to higher usage and demand on the clay (C) material caused its depletion and higher in cost. Therefore, accumulated AS can be recycled and reused to reduce the disposal problem in landfill and financial burden facing by the landfill operator. In this study, AS was investigated and compared with the kaolin clay (KC) in terms of XRD and SEM characteristics. The index properties and hydraulic conductivity, k test were also conducted to classify the AS and KC composition. Based on the testing, AS can be classified as High Plasticity Clay and the value of k for AS is higher than KC. Based on the results from XRD, both of KC and AS samples was having a similar crystalline phase which is Quartz. Based on the summary of compounds elements, the chemical elements of Oxygen, Aluminium, Silicon and Iron presence in AS have a quite similar percentage of weight (%) with KC. From all of these results, it can be concluded that the AS is mostly having similar materials to KC and amorphous in nature.

Study of low plasticity clay for optimum dosage of the soil-cement

The need to improve people’s living conditions starts from the reality of the durability of rural road constructions, which have a short useful life and have a negative impact on the inhabitants of these regions. This project aims to improve access to rural areas, rural economic development and thus improve the quality of life of people in the sector; taking into account that at the moment of building a rural road, has a better resistance and durability in time, this was done by analyzing the properties of the clay mixture of low plasticity in the dosage of soil-cement that were tested by tests to determine the liquid limit of soils, determination of the plastic limit, plasticity index, moisture test, classification of soil by sieving, granulometric analysis, unit weight-humidity relations in soils, soil support relationship in the laboratory; in order to find the best dosage that provides greater strength, long-term durability and risk reduction. The results indicate that this type of clay requires an improvement with cement, due to its bearing capacity of 2% and 4%, which gives it a very poor quality to be used in the construction of rural roads.

Influence of RHA on Engineering Properties of Medium Plastic Clay

Influence of RHA on Engineering Properties of Medium Plastic Clay - written by Nabeel Liaqat , Muhammad Farjad Sami , Naeem Bashir Awan published on 2019/10/22 download full article with reference data and citations

New texture with black grey color of fired clay wall tiles produced from rice husk ash, brown glass cullet, and local plastic clay

Developing fired clay wall tiles by valorising waste materials and local plastic clay was objective of this study. Rice husk and glass cullet are waste materials which had been selected. They were mixed with local plastic clay of Angthong province in Thailand. All materials used were characterized their composition by X-ray Fluorescence technique. Specimens had been prepared by dry pressing and then fired at 950°C and 1050°C. Physical properties, bending strength and water absorption, were tested and compared with Thai Industrial Standard (TIS 2508-2555). In addition, X-ray Diffraction technique and Scanning Electron Microscope were used to analyse microstructure of selected specimens. The results of this experiment shows that utilizing of 60-70% brown glass cullet, 10-30% rice husk ash fired at 950° C is feasible to produce wall tiles for commercial. It provides high bending strength and low water absorption and can pass the TIS 2508-2555. Furthermore, it provides new texture with black grey colour of wall tiles.

Durability of Commercial Waste Bagasse Ash And Ground Granulated Blast Furnace Slag Stabilized High Plastic Clay

In the current work, a problematic expansive high plastic clayey (CH) soil of Surat, Gujarat, India has been treated with commercial waste bagasse ash (BA) and ground granulated blast furnace slag (GGBS) for sustainable development. Swell shrink behavior, California bearing ratio, unconfined compressive strength for different curing period have been studied. As expansive soil is very sensitive to seasonal variation, cyclic drying and wetting study has been carried out on both treated and untreated samples. The optimum blend is observed to be in the proportion of 82.5%CH + 10%BA + 7.5%GGBS. The unconfined compressive test results indicate that strength of 28 days cured samples of optimum mix increases about three times and eight times when compared to untreated sample and uncured sample respectively. The soaked California bearing ratio (CBR) indicate the increase in strength with increasing curing periods from 7 to 28 days. Optimum mix shows the decrease in swelling pressure and an increase in shrinkage limit as compared to untreated soil. The experimental results show good improvement in swell-shrink behavior, unconfined compressive strength, and soaked California bearing ratio when combined with bagasse ash and slag. The findings of this study revealed that bagasse ash in combination with ground granulated blast furnace slag is suitable as a pozzolanic material in stabilization of high plastic clay to reach the target strength for structures with improved swell-shrink behavior.

Stability of Deep Excavation Slopes in Continuous Surface Lignite Mining Systems

The paper investigates the stability of deep continuous surface lignite mining slopes. As excavation slopes are made relatively steep for exploitation purposes, the risk of slope instabilities is often appreciable, while the adverse consequences of a major failure are usually severe. Despite these, the design of lignite mining slopes against instability is often empirical, because the mechanisms causing such instabilities are poorly understood. Experience shows that slope instabilities are usually governed by sliding along a sub-horizontal, unfavourably sloping interface between a coal seam and an underlying stiff, high plasticity clay or marl layer, very close to the bottom of the slope. The typical mechanism of such instabilities is triggered by the sharp contrast in stiffness between adjacent lignite and clay/marl layers causing different elastic rebound upon removal of the horizontal confinement during excavation. The paper examines the effect of specific parameters on slope stability by a set of parametric analyses. It is shown that the most important parameter is the inclination of the sub-horizontal lignite–clay interface at the base of the slope. The paper also reviews several slopes in lignite mines which remained stable despite movements with relatively constant velocities reaching up to 100 mm/day, while others have failed when velocities accelerated abruptly although much smaller. These cases show that the absolute magnitude of slope velocity is not always relevant in predicting slope instability, while slope acceleration is a better indicator.

The Alternatives to Traditional Materials for Subsoil Stabilization and Embankments.

Major infrastructure projects require significant amount of natural materials, often followed by the soft soil stabilization using hydraulic binders. This paper presents the results of a laboratory study of alternative waste materials (fly ash and slag) that can be used for earthworks. Results of high plasticity clay stabilization using fly ash from Serbian power plants are presented in the first part. In the second part of the paper, engineering properties of ash and ash-slag mixtures are discussed with the emphasis on the application in road subgrade and embankment construction. Physical and mechanical properties were determined via following laboratory tests: Specific gravity, grain size distribution, the moisture–density relationship (Proctor compaction test), unconfined compressive strength (UCS), oedometer and swell tests, direct shear and the California bearing ratio (CBR). The results indicate the positive effects of the clay stabilization using fly ash, in terms of increasing strength and stiffness and reducing expansivity. Fly ashes and ash-slag mixtures have also comparable mechanical properties with sands, which in combination with multiple other benefits (lower energy consumption and CO2 emission, saving of natural materials and smaller waste landfill areas), make them suitable fill materials for embankments, especially considering the necessity for sustainable development.

Керамика саргаринско-алексеевского могильника Каратугай

The article considers the results of studying the technology of pottery manufacturing at the Sargarinsko-Alekseevsky burial ground of Karatugay (Central Kazakhstan). By the method of A.A. Bobrinsky using a MBS-10 binocular microscope, 10 archaeologically intact and fragmented vessels have been studied. The information has been obtained on the characteristics of the material, the preparation of molding compound recipes, the methods of constructing the beginning and hollow body, surface treatment, and firing conditions. A set of basic pottery traditions has been defined (selection of raw materials – medium-iron plastic clay with a natural admixture of oolitic brown iron ore; molding mass recipe – medium / large wood pulp at a concentration of 1:5 + small medium-iron chamotte at a concentration of 1:5 + manure; capacitive program; constructing a hollow body in a patchwork-lumpy way), imported vessels have been identified, the sequence of burials has been established. It is shown that the population who left the site lived together with representatives of the Irmen culture.

Micro-scale characterisation of clay at elevated temperatures

The main objective of this study is to use a suite of micro-scale tests to characterise the temperature effects on high plasticity clay. The unheated clay was examined using X-ray diffraction, field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectrometry to characterise the mineralogy, morphology and the elemental composition of natural soil. The clay was then cured under various temperatures ranging from 23 to 1000°C. The characteristics of heated clay were then evaluated using FESEM, cation-exchange capacity (CEC) tests, thermal gravimetric analysis (TGA) and Brunauer–Emmett–Teller (BET) surface area analyser. The results show minimal changes in soil fabric with increased temperature. However, specific surface area and CEC are shown to significantly decrease with temperatures beyond 100°C. TGA results can provide an insight into the drops of BET surface area and CEC. Depending on the range of temperature applied, the changes can be attributed to the temperature effects on the clay microstructure, loss of capillary and adsorbed water and organic matter, and the clay mineral's interaction with the displacement cation or nitrogen. The observed trends are used to discuss possible implications on the hydro-mechanical properties of soil such as the soil–water-retention curve, shear strength and volume change.

Fabrication of electrical porcelain insulator from ceramic raw materials of Oromia region, Ethiopia

Electrical porcelain insulator was fabricated from local ceramic raw materials, Bombowha kaolin/clay, Arero feldspar and Arero quartz available in Ethiopia. The raw materials mineralogy, chemical composition, and thermal properties were characterized by using x-ray diffractometer (XRD), atomic absorption spectrometer (AAS) and thermogravimetry (TGA), respectively. Plasticity of clay was determined according to Atterberg plasticity test. Based on the raw materials chemical composition, five different porcelain insulator test bodies were prepared at firing temperature of 1000 °C, 1100 °C, 1200 °C and 1300 °C. Water absorbance, apparent porosity, bulk density, dielectric strength and microstructure of fired porcelain insulators were studied as a function of firing temperature. The XRD and AAS results revealed that in Bombowha clay, kaolinite mineral was found to be a major mineral constituent with appreciable silica (46.84 wt%) and alumina (36.74 wt%) content with moderate plasticity (PI = 19–21%). The Arero feldspar belongs to anorthoclase feldspar minerals with less alkali content (Na2O + K20) of <7wt %. Among the tested porcelain insulator bodies, the test body with composition of 45% kaolin, 45% feldspar and 10 % quartz exhibited superior properties of having a water absorbance of 0.010%, porosity of 0.088%, density of 2.466 g/cm3, dielectric strength of 8 Kv/mm at firing temperature of 1300 °C with mullite and quartz phase embedded in sufficient glassy phase. Therefore, the experimental result confirmed that standard porcelain insulator can be fabricated from locally available ceramic raw materials (clay and quartz) in Ethiopia at optimized condition.

EXPERIMENTAL STUDY OF STABILIZED EXPANSIVE SOIL USING PUMICE MIXED WITH LIME FOR SUBGRADE ROAD CONSTRUCTION

Unsuitable soil materials along the alignment of road projects have a significant influence on planning, design, construction, and maintenance. Expansive soils are susceptible to considerable volume changes due to seasonal variations and moisture content. Most soils found in Jimma and Ambo Zones composed of plastic clay soil, causing severe damage at the intermittent of pavement sections. This research study conducted laboratory investigation considering combinations of materials blended to stabilize the expansive soil for subgrade construction. An experimental type of study performed which started by collecting specimens. Two clayey soil specimens considered to test the free swell index obtained from a depth of 1.5m to remove the organic impurities. Results indicated the chemical analysis of pumice contained 82.68%, while its physical properties of the test of fineness specific surface and residue on 45 microns showed 3770 cm2/gm and 30%, respectively. As the lime content increased, the CBR strength also increased. But, if the percent content of lime decreased with an increasing pumice content, the CBR value did not show any significant increase. Both the chemical and physical properties satisfied the requirements according to ASTM C-618. Hence, this experiment obtained 7% lime + 3% pumice as an optimum mix ratio to stabilize expansive soils.

EXPERIMENTAL STUDY OF STABILIZED EXPANSIVE SOIL USING PUMICE MIXED WITH LIME FOR SUBGRADE ROAD CONSTRUCTION

Unsuitable soil materials along the alignment of road projects have a significant influence on planning, design, construction, and maintenance. Expansive soils are susceptible to considerable volume changes due to seasonal variations and moisture content. Most soils found in Jimma and Ambo Zones composed of plastic clay soil, causing severe damage at the intermittent of pavement sections. This research study conducted laboratory investigation considering combinations of materials blended to stabilize the expansive soil for subgrade construction. An experimental type of study performed which started by collecting specimens. Two clayey soil specimens considered to test the free swell index obtained from a depth of 1.5m to remove the organic impurities. Results indicated the chemical analysis of pumice contained 82.68%, while its physical properties of the test of fineness specific surface and residue on 45 microns showed 3770 cm2/gm and 30%, respectively. As the lime content increased, the CBR strength also increased. But, if the percent content of lime decreased with an increasing pumice content, the CBR value did not show any significant increase. Both the chemical and physical properties satisfied the requirements according to ASTM C-618. Hence, this experiment obtained 7% lime + 3% pumice as an optimum mix ratio to stabilize expansive soils.

Strength development in fine-grained paddy field soil by lime addition

Due to high population density, the people of Bangladesh are building houses and the government is establishing infrastructure (such as roads, flyovers, bridges) on agricultural land that pose significant settlement issues. Consequently, such development works require prior improvement of the soft soil or improvement during construction to restrict post-construction failures. Soil stabilization, a conventionally used ground improvement method, is often utilized to alter engineering properties of fine-grained soil such as strength, stability, permeability, weathering resistance, etc. to maintain the required construction criteria. Moreover, the addition of lime in the soil is demonstrated to markedly reduce the hydraulic conductivity, which will prevent the vertical movement of pore water. With this in mind, in the current study an attempt has been undertaken to increase the strength of fine-grained soil of agricultural land by adding commercially available hydrated lime, which may in the future be used as foundation material. For this purpose, lime was added at various percentages (0–12%) by weight to soil collected from a paddy field. The study noted the collected soils as being inorganic silts of high plasticity or organic clays of medium to high plasticity. Unconfined compression tests were conducted on cylindrical mold prepared specimens with clayey soil in the presence of lime, and all specimens were cured for 3–90 days for strength development. The study revealed 7% added lime as the optimum content, with the corresponding unconfined compressive strength (UCS) observed to be 344 kPa and 356 kPa at the end of 28 days and 90 days, respectively. The evolution of unconfined compressive strength was higher in hotter and more alkaline environments.