Clayey Fraction Research Articles

The starting stoichiometry, keys parameter to enhance the intrinsic microstructural and functional properties of synthesized hybrid nanocomposites chitosan/Na-montmorillonite/ZnO nanoparticlest type

To improve the intrinsic qualities of hybrid nanocomposite (NC), polymer, clay, and metallic oxide are combined. This study investigates the effects of starting stoichiometry variation on the microstructural and functional properties of synthesized hybrid NC composed of chitosan (CTS), Na-montmorillonite (MMT), and ZnO nanoparticles (NPs). To carry out the synthesized process, a solution blending approach is used. A correlation of the outcomes from the several analyses methods such as X-ray diffraction (XRD), Fourier Transform InfraRed spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Impedance spectroscopy (IS), and UV–VIS spectrophotometry ensures the accuracy of the analysis. Regardless of the initial stoichiometry rate, the microstructural analysis shows that NC can be successfully synthesized. The growth and changes in the intensity and sharpness of the characteristic reflections shown by the semiquantitative XRD analysis suggest that the synthesis process was certainly successful. The apparent structure aberration, caused by the stoichiometry fluctuation, is manifested as an XRD reflection position shift and varied intensity strength.The intercalation process and the exfoliation of "clay-particles" enclosing the organic fraction, according to TEM/EDX experiments, occurred as the clayey fraction's abundance surged. Despite the variable ratio approved at the start of the synthesis process, FTIR spectroscopy displays the polymer fraction's characteristic absorption bands. Synthesized NC has significant UV blocking properties while retaining good transparency in the visible range. This behavior may have its roots throughout the fact that the CS surface modification has induced the bandgap energy fluctuation of ZnO NPs. The photocatalytic activity of the produced NC is evaluated using MB degradation measurements. The outcomes are extremely positive for the sample with a starting stoichiometry almost equally distributed between CTS and ZnO (NPs). Results from the IS, for the selected sample, shows that synthesized NC exhibits semiconductor behavior,and as a dielectric material, the sample is dispersive with a power loss over a specific frequency range.

Evaluation of CO 2 sealing potential of heterogeneous Eau Claire shale

Abstract During geological carbon dioxide storage in deep saline aquifers, buoyant CO 2 tends to float upwards in the reservoir overlaid by a low permeable formation called a caprock. Caprocks should serve as barriers to potential CO 2 leakage that can happen through diffusion and permeation through faults, fractures or pore spaces. The leakage through intact caprock would mainly depend on its permeability and CO 2 breakthrough pressure and is affected by the heterogeneities in the material. Here, we study the sealing potential of a caprock from the Illinois Basin – Eau Claire shale, with sandy and clayey fractions distinguished via electron microscopy, grain/pore size analyses and surface area characterization. The direct measurements of permeability of sandy shale provide the values on the order of 10 −15 m 2 , while clayey specimens are three orders of magnitude less permeable. The CO 2 breakthrough pressure under in situ stress conditions is 0.1 MPa for the sandy shale and 0.4 MPa for the clayey counterpart – these values are higher than those predicted by the porosimetry methods performed on the unconfined specimens. Sandy Eau Claire shale would allow penetration of large CO 2 volumes at low overpressures, while the clayey formation can potentially serve as a caprock in the absence of faults and fractures.

Surface Microanalysis and Sequential Chemical Extraction as Tools for Reliable Environmental Mobility Assessment of Sb and Other Metals.

Sequential extraction procedures (SEPs) are widely used in environmental studies to infer the chemical and/or mineralogical forms of pollutants of concern in soils and sediments. Although there is no general agreement among the scientific community, these methods have shown some limitations, especially those with a lack of objectivity in their interpretation. In this work, a soil sampling campaign was carried out in an area affected by an abandoned Sb mine. Samples (0–15 cm) were carefully prepared and analyzed by an SEP. They were also studied by conventional mineralogical methods (optical and electronic microscopy, both scanning and transmission, with a coupled energy dispersive X-ray (EDX) spectrometer). When comparing the results obtained from both techniques, some discrepancies are highlighted, with As, Cu, Pb, Sb and Zn as elements of concern. For Sb, Cu, Pb and As the predominant fraction (excluding the residual one) is that associated with organic matter (from 8.54 for Sb to 18.90% for Cu). The fractions of pollutants linked to Fe and/or Mn oxides are quantitatively important for As, Pb and Zn (6.46%, 12.05% and 7.43%, respectively) and almost negligible for Cu and Sb. On the contrary, analyses carried out by EDX at a grain scale pointed out that no detectable quantities of the elements of concern were present on the surface of the organic particles. Sb and Pb were always detectable in Fe oxides (up to 1.84 and 5.76%, respectively). Regarding the role of the clayey fraction, the only disagreement between the employed SEP and the microanalysis is in relation to As. Arsenic bound to clay minerals was found to be an order of magnitude lower than As associated with Fe oxides (0.56% and 6.46%, respectively); in contrast, EDX microanalyses showed similar As contents in both groups. Given the objectiveness of EDX microanalysis, these differences should be considered inaccuracies in the interpretation of the sequential extraction results.

Characteristics of the sediments hosting the Thracian settlement near the town of Letnitsa

The Thracian settlement near the town of Letnitsa is situated on the left fluvial terrace of the Osam River. Hosting sediments are determined as sandy clayey silts, limy in various degrees. Deposits from the western and central parts are compared and both show similar mineralogical composition. These from the central parts contain more fine silt and clayey fraction, which supposes that these parts could have been flooded by the river.

Petrological Characterization of Pelites from the Mintom Basin and Their Weathering Mantle

The aim of the present study is to characterize a weathering mantle developed on pelitic rock in the tropical forest region precisely in Mintom (South East Cameroun). This characterization include morphology, physico-chemical and mineralogic analyses. The region is characterize by a hot and wet climate consisting of four seasons of inequal length and intensity. The average temperature is about 24°C and the mean rainfall is about 1633mm/years. The rocks in the area consist of limestone, dolomites and pelites. Fieldwork consist of landscape analysis, geologic prospection and soil profile description. Mineralogical and physico-chemical was carried out on various samples in the laboratory. Morphological results show that the studied profile has a general brownish yellow aspect, with a thickness of about 6m and a silty-clayey texture. Five horizons can be distinguished from top to bottom: a humiferous horizon, a loose yellow set, a yellow horizon bearing quartz fragments and large indurated blocks, a saprolite consisting of a fine and coarse saprolite possessing some pelite relics of variable sizes and a deep red colour just like that of the parent rock. The parent rock is a massive pelite with a reddish colour when wet and a violet colour when dry. It has a powdery feel. Analytically, the soils have an acidic pH (4,0 to 4,2), a high organic matter content (4,8%), a C/N ratio of about 6,76, a cationic exchange capacity of 7,64meq/100g with a saturation rate S/T of about 7. Particle size distribution shows that the silty fraction is dominant (59%), followed by the clayey fraction (30%). The main minerals are kaolinite, quartz, smectites, calcites, dolomites, goethite and hematite.

Detection of land degradation caused by historical Zn‐Pb mining using electrical resistivity tomography

AbstractSoil contamination with trace elements in mining areas still remains an urgent research problem due to their negative environmental impact that needs to be assessed. Despite the wide application of the electrical resistivity tomography (ERT) method to different environmental problems, it continually remains methodologically challenging in soil contamination near waste dumps of post‐metal historical mining. The aims of our study were: (1) to validate ERT measurements for detecting soil contamination by trace elements in the vicinity of a waste dump containing post‐processing spoil from Zn‐Pb ore smelting, (2) to determine the extent of soil contamination, and (3) to analyze the mineralogical, physical, and chemical properties of the soils affected. ERT enabled us to study the variability of electrical properties of soils, to locate the area of contamination, and to evaluate its spatial diversity in both. The impact of soil pollution is reflected on ERT cross‐sections in the form of electrical resistivities that decrease with increasing depth and distance from the waste dump. The respective maximum contents of Zn, Pb and Cd in the soils were 28,903, 12,407, and 136 mg kg−1. The total concentration of trace elements in soils was the highest down to a depth of 0.25 m and decreased in the order: Zn > Pb > Cu > Cd > Tl > As > Cr > Ni. The electrical resistivities of the soil samples were negatively correlated with the silty and clayey fraction content (−0.78), specific electrical conductivity (−0.75), total trace element content (−0.67), organic matter content (−0.57), and gravimetric water content (−0.53). The results also indicate that the electrical properties of the topsoil depend directly on the type of mineral components. Hydrated iron sulphates, lead sulphates, water‐bound in aluminosilicates, Fe oxides/hydroxides, and hydrated Fe, Zn, and Pb sulphates present in the soil all decrease its electrical resistivity. Our results show the impact of the mineralogical, physical, and chemical properties of the soils on the measured electrical resistivity and that including this information in the interpretation of ERT results enables non‐invasive detailed determination of soil contamination by trace elements.

Mineralogical, physico-chemical and technological characterization of clay from Bensmim (Morocco): Suitability for building application

This study aims at the valorization of unexploited clay from a rural village called Bensmim by investigating its potential suitability as a construction material. Two clays samples (Babmansour and Extrabrick) used in the clay brick manufacturing were also considered as a reference. The followed methodology consists of identifying the physicochemical properties of the raw materials and examining its influence on the final products properties (linear shrinkage, thermal conductivity, and compressive strength). The firing characteristics of the samples under study at different temperatures (650 °C, 850 °C, and 950 °C) were determined by linear shrinkage, compressive strength, and thermal conductivity. The results show that the clayey fraction of Bensmim consists mainly of illite and kaolinite. However, Extrabrick and Babmansour contain kaolinite with moderate amounts of smectite. The major oxides presented in all clays samples are SiO2 (57–59.6 wt%), Al2O3 (10.38–23.29 wt%), and Fe2O3 (3.78–6.58 wt%). The amount of CaO in Extrabrick clay is about of 10.61% and 11.14% for Babmansour, whereas it is almost absent in Bensmim clay. Extrabrick and Babmansour clays samples are considered as calcareous clay (CaO > 10%) characterized by a moderate specific surface and high plasticity due to their high clay fraction and moderate smectite content. While Bensmim has a weak specific surface and low plasticity due to the absence of swelling phase in its clay fraction and the excessive amount of sand. The performed tests attest high thermal properties of Bensmim clay, with good linear shrinkage. Unfortunately, under 950 °C, Bensmim clay presents low compressive strength. However, this can be adjusted by a small addition of the plastic clays.

Status and Speciation of Silicon and Its Interaction with Physico-Chemical Properties

The effectiveness of three different extractants soil mixtures—HCl, HCl + H2S04, and DTPA-TEA, in order to determine Si from soil and the forms of Silicon as influenced by different parent materials under acidic medium.
 Seven forms of Silicon; namely water soluble, specifically adsorbed, oxides bound, organic matter bound, exchangeable, residual, total viz sequential fractionation.
 Extractable Si value established in this study was (50.0 mg kg-1), indicating negative effect on plant physiology. The physico-chemical properties decreased significantly with increase in soil depth vs soil parent materials. In addition, the forms of Si in the parent materials decreased in the pattern RES, bound residual fractions > EXC, soluble & exchangeable fractions > OM, organic matter fraction.
 Among the properties the silt fraction, pH & OM significantly and positively correlated with the forms of silicon, with negative correlation vs clay which maybe due to silicon adsorption by clayey fraction of the soil (redox). Therefore the soil maybe be maintained and conserved for farming activities.

Recycling and Reuse of Sediments in Agriculture: Where Is the Problem?

Though suggested by international conventions for a long time, there are still several technical and legislative limitations to a complete reuse and recycling of dredged sediments. In particular, reuse of unpolluted sediments can be practiced, whereas sediment recycling is still affected by several downsides, and a significant proportion of the recycled fine sediments has no practical use and must be landfilled. However, the silty clayey fraction of the recycled sediments is rich in organic matter and macro- and micronutrients useful for plant growth. Nevertheless, sediment recycling in agriculture is not possible, even in non-food agricultural sectors, due to the lack of a permissive legislation and of consolidated supply chains. In addition to plant nutrients, the silty-clay sediment fraction may also accumulate organic and inorganic pollutants, and while the organic pollutants can be effectively biodegraded, metals and metalloids may concentrate at concentrations higher than the limits set by the environmental and agricultural legislations. In this paper, I briefly summarize the scientific evidence on the potential reuse and recycling of sediments in agriculture, and I discuss the main reasons for hindrance of sediment recycling in agriculture. I also present evidence from a real industrial biodegradation process that produces bioremediated fine sediment fractions with suitable properties as a mineral ingredient for plant-growing media. I propose that nutrient-rich recycled sediments could be reconsidered as a component material category in the new EU regulation on fertilizers.

The nature of Zn-phyllosilicates in the nonsulfide Mina Grande and Cristal zinc deposits (Bongará District, Northern Peru): The TEM-HRTEM and AEM perspective

Abstract Zn-phyllosilicates are common minerals in nonsulfide Zn deposits and can give crucial information about the genesis of these oxidized mineralizations. They seldom represent the prevailing economic species but might have a significant impact on mineral processing. This study has been carried out on the Mina Grande and Cristal Zn-sulfide/nonsulfide deposits, which occur in the Bongará district (Amazonas region, northern Peru). The Cristal and Mina Grande orebodies are hosted by the sedimentary (prevailingly carbonate) successions of the Pucará Group (Condorsinga formation, Lower Jurassic), in an area affected by Neogene tectonics and characterized by Late Miocene and Pliocene-Early Pleistocene uplift phases (Andean and Quechua tectonic pulses). The Cristal deposit consists of both sulfide (sphalerite with minor pyrite and galena) and nonsulfide concentrations. The nonsulfides consists of smithsonite, hemimorphite, hydrozincite, chalcophanite, goethite, and greenockite, locally associated with Zn-bearing phyllosilicates. The Mina Grande deposit consists almost exclusively of Zn-oxidized minerals in limestone host rocks. The nonsulfides association consists of hydrozincite, hemimorphite, smithsonite, fraipontite, and Fe-(hydr)oxides, also containing a clayey fraction. The study deals with TEM-HRTEM and AEM investigations on clayey materials, to determine their crystal-chemical features and the origin of the complex Zn-clays-bearing parageneses. In both deposits, Zn-bearing illites (1Md and 2M polytypes) and I/S clay minerals (I3) are the main detected phases, with few compositions close to (Zn-bearing) muscovite. In the clayey fraction at Mina Grande, fraipontite, a Zn-bearing mica called K-deficient hendricksite, and (Zn-bearing) kaolinite also occur. Zn-illites and smectites (always containing Zn in variable amounts) characterize the mineral association at Cristal. The investigated compositional gap between di- and tri-octahedral Zn-phyllosilicates gives indications on the genetic relationships between them and advances on the knowledge of these species. The present work gives an insight into the Zn-bearing phyllosilicates systems by determining the amount/mode of metal incorporation in their lattices and understanding the relationships of natural occurring clay-rich complex associations, which can act as models for possible synthetic counterparts.

Mechanisms involved in the increase of borosilicate glass alteration by interaction with the Callovian-Oxfordian clayey fraction

The influence of clay minerals of the Callovian-Oxfordian claystone on the alteration of international simple glass (ISG) was investigated through batch experiments conducted at 90 °C and via geochemical modeling. Several clay/glass weight ratios ranging from 0.9 to 91 were tested. These experiments revealed that the mechanisms controlling glass alteration were indirectly dependent on that ratio. The solution and solid characterizations indicated the presence of non-clay minerals such as pyrite, Mg-calcite, quartz, dolomite, and magnesite in the treated clay material, which influenced the results. The clay minerals were poorly reactive. The carbonates and clay exchanger released reactive magnesium in solution. Furthermore, it is worth noting that the reactors did not prevent air-solution interactions. The simulations demonstrated that O2 contribution needs to be considered to explain the clay-glass interactions. The mechanisms controlling clay-glass interactions were deciphered based on mineralogical characterizations and geochemical modeling. At high clay/glass ratio, glass dissolution was sustained by pyrite oxidation and possibly iron silicate precipitation, while at low clay/glass ratio the passivation of the glass was prevented by the precipitation of magnesium silicate minerals.

THE MICROMORPHOLOGY AND MINERALOGY OF GRAY FOREST SOILS IN VLADIMIR OPOLYE

The investigations were conducted on the gray forest heavy clay loamy soils, formed on the loess-like loams, which are widely spread on the territory of Vladimir Opolye. The eluvial-illuvial profile differentiation, its different intensity and the specificity of illuvial coatings (fine dispersed clayey and humus-clayey coatings with sparse skeletal content of soil) is confirmed. The presence of the coarse wooden plant residues, thick humus-clayey illuvial coatings within the illuvial horizons speak about the forest origin of the grey forest soils in Vladimir Opolye. The micromorphology of humus horizon reflects the direction of the soil forming process and the ecological status of soils. The illimerization is the main process of the matter migration and soil profile differentiation. The mixed-layer formations prevail in the clayey fraction. Mica, quartz, and K-feldspars are the prevailing compounds of the fine and medium silt within the gray forest soils. In the silt fraction of the second humus horizon prevail quartz and feld-spar. The most of the nutrients is concentrated in the clayey and fine-silt frac-tion. The micromorphological investigations confirmed the theory, which speaks about the presence of forest (the presence of illuvial coatings) as well as steppe soils (mull humus type in the SHH, the presence of primary and newly formed carbonates) specificities in the modern soil forming process within the gray forest soil of Vladimir Opolye.

Suitability of Foumban Clays (West Cameroon) for Production of Bricks and Tiles

Particle size analysis, Atterberg limits, X-ray diffraction, X-ray fluorescence and firing tests were used to determine physico-chemical, mineralogical and technological characteristics of residual lateritic (K1M, Ma2) and alluvial (KB3, KG3) clays from Foumban (West-Cameroon). For technological properties, the samples were pressed and fired over a temperature range of 900d relative high feldspars (20%) and illite contents (10%) in KB3 and MA2; high smectite content in KG3 (up to 20%). Chemical analyses indicate high SiO2 (49% - 77%) and low Al2O3 (14% - 23%) contents in the four samples, with comparatively low contents of iron oxides (4% - 7% in samples KB3 and KG3, 2.5% in MA2 and ~1.5% in sample K1M). The particle size distribution of the alluvial clays (KG3 and KB3) differs considerably: 7% to 37% of clay fraction, 20% to 78% of silt, and 15% to 58% of sand, while residual clays (K1M and MA2) present on average 12% of clay, 51% of silt and 37% of sand. Two raw clays (KB3 and MA2) can be used for bricks/tiles production without beneficiation or addition. K1M requires some flux addition to decrease the sintering temperature while KG3 presents poor properties due to the combined occurrence of smectite and a high clayey fraction (37%). Such mineralogical composition is responsible for very high plasticity (PI: 50), high shrinkage (LS: 5% - 16%), low porosity (OP: up to 21%) and high flexural strength (FS: 16 - 23 N/mm2) above 1050&degC. This last clay is therefore less appropriate for bricks and roofing tiles production since degreasers must be added to the raw material.

О некоторых аспектах моделирования геодинамического риска на территориях рас-пространения просадочных грунтов.

In modeling geodynamic risk, the issues of developing special models of risk on the territories of distribution of loess and loess-like subsident soils under technogenic impact are of great relevance. Developing such models is a multi-stage process, which requires developing a model of the geological structure of a studied massif and setting predicted values of the properties of loess soils for preliminary quantitative evaluation of possible deformations in the natural conditions and in the zone of impact of constructions. Standard quantitative evaluation concerning the subsidence is carried out using results of testing the sample in limit states. Prognosis of the degradation of subsidence properties as a result of the break-up of the microaggregates in the zone of aeration is possible in conditions of impact of changes in the microaggregate compound on the subsidence. Using the method of defining the granulometric composition of the soil allows one to determine the area of soil condition in relation to dispersity. The method of GMDH allows one to develop a mathematical model of degradation of subsidence properties and calculate the predicted values of deformation in the zone of insufficient water content. The degradation of the subsidence properties of subaerial horizons is manifested most significantly at mild (30% of possible) increments of moisture and pressure of 0.1 mPa. In the area of additional pressure, predicted values of deformation insignificantly increase under moisture due to degradation, with increased moisture the break-up of the aggregates of sand fraction is followed by increase in the number of aggregates of smaller size (large-grained pulverescent ΔА3). The content of free thin fine-grained sandy (ΔM2), and clayey particles (ΔМ5, ΔМ6) increases, connected with aggregates of thin fine-sandy and large-grained clayey. The share of aggregates of large-grained pulverescent fraction also increases; the content of particles of this fraction assembled in the aggregates decreases. The dependency of deformation intensity in conditions of degradation of paleosol is of another character: the intensity of degradation increases as the pressure rises. The analysis of predicted values of aggregate content, free and assembled particles when there is change in moisture conditions showed that the process of the break-up of thin fine-sandy aggregates and increase in the share of large-grained clayey aggregates (composed of thin fine-sandy particles) is followed by occurrence of free particles of thin fine-sandy and thin clayey fractions.

Перераспределение минералов в элювиально-иллювиальном горизонте агродерново-подзолистой почвы

The structure of micromonoliths from eluvial horizon (EL), transitional horizon (BEL) and iluvial horizon (BT1) of agro soddy-podzolic soil developed on clay loam mantle, underlain by non-calcareous moraine was studied. The following methods were applied: microtomography, x-ray diffractometry analyses, laser diffractometry, and soil particles sedimentation method. The objects are located on the experimental field of Zelenograd stationary related to Dokuchaev Soil Science Institute (Yeldigino village, Moscow Oblast). The method of computer tomography helped to determine the zones, from which the silty and clayey fragments of transitional horizon were extracted. The method of sedimentation allowedustomark the differences in the amount of fractions with sizes 10 mm. The method of x-ray diffractometry allowed us to determine the correlation of minerals in fractions with different particles sizes and also their qualitative composition. The minimal content of the clayey fraction is set is set in the sample from the eluvial part of the profile. The maximal content was set in the sample of separated clayey material from the transitional horizon. The most significant differences in the mineralogical composition are observed in the fraction lower than 1 mm. The eluvial part of the profile is characterized by the prevailing of hydromicasand chlorite vermiculite mixed-layer minerals. The same correlation of minerals is observed within the sample of silty part from the transitional layer. The iluvial part of the profile is characterized by the decrease of compounds with rigid structure (hydromicas, chlorite vermiculite). The clayey part of the transitional horizon is characterized by the highest content of silt and mica smectite within it. The distribution of fractions of fine (1-5 mm) and medium (5-10 mm) silt and their mineralogical content is less informative in relation to the differentiation of the soil profile during the podzolization.

Ecological-genetically peculiarities and diagnostics of the cultivated urban soils in the Central Botanical Garden of NAS of Azerbaijan

The soil forming process leaks under the conditions of semidesert, dry and hot climate as a result of what is formed weak developed saline – salty grey-brown soils in the research object. In the virgin land the humic – accumulative horizons of the grey-brown soils are weakly developed and capacity doesn't rise 15–20 sm. The humus content on the upper horizons is little and forms 0,9–1,1%, but nitrogen – 0,07–0,09%. The high calcareous soils, CaCO3 content over the whole profile is 19–26%. A quantity of the absorbing capacity is also little and forms 16-18 m-ekv per 100 g of soil on the upper horizons. The long (more than 70 years) intensive use of the garden territory under various green grove and performance of the scientific – research works and lines of the agrotechnical measures (deep tillage, regular irrigation, application of manure and mineral fertilizers) have been strongly represented in formation of the morphological profile from urban soils and their diagnostic indices. Enough powerful cultivated layer (AUa = 40-50 sm) is formed with the granular – cloddy structure where humus content is 2,4–2,7%, nitrogen – 0,20–0,22%, which aren't characteristic with grey-brown soils in Absheron. Maximal content of carbonates (CaCO3 = 18–20%) and clayey fractions (<0.01 mm = 40–50%) are noted in the mean part of the soil profile, as a result of leaching from upper layer. The cultivated urban soils are distinguished with enough increased capacity of absorption (23-25 mg-ekv) and profile weight is leached from light soluble salts (dense residue 0.088–0,230%)

Occurrences of kaolin in Koutaba (west Cameroon): Mineralogical and physicochemical characterization for use in ceramic products

AbstractThirty clay samples collected from three hills in Koutaba (west Cameroon) were characterized in order to evaluate their potential use as raw materials for ceramics. After preliminary mineralogical identification by X-ray diffraction, three representative samples from the three different hills, referred to hereafter as K1M, K2M and K3M, were selected for further investigation by X-ray fluorescence, plasticity, granularity and thermogravimetric analysis. The main clay minerals are kaolinite (32–51%) and illite (up to 12%). Additional major phases are quartz (32–52%), goethite (6–7%) and feldspars (0–4%). The chemical composition showed variable amounts of SiO2(60–72%), Al2O3(15–20%) and Fe2O3(1–9%), in accordance with the quartz abundance in all of the samples studied. The particle-size distribution showed a large proportion of silty fraction (64–88%) with moderate sandy (9–19%) and clayey fractions ( &lt; 5% for K2M, 12% for K1M and 20% for K3M). All of the clays showed moderate plasticity-index values (8–11%). Because of these characteristics, K1M and K3M may be suitable for use in common bricks and hollow ceramic products. Sieving or the addition of ball clays is recommended to increase the plasticity of sample K2M for use in common bricks.

Pleistocene sediments of Lake Baikal: Lithology and stratigraphic correlation

The Cenozoic sediments of Lake Baikal penetrated by boreholes and investigated by the manned submersible Pisces, as well as coeval deposits cropping out in beach scarps, recovered by mine workings, and drilled in the coastal zone were the object of this investigation. The main attention was paid to Pleistocene bottom sediments penetrated by Borehole BDP-99-2. The investigations included the detailed analysis of the lithology (grain-size composition, immersion mineralogy of light and heavy fractions, X-ray structural analysis of clayey fraction) and palynological assemblages to specify facies features of Cenozoic sediments, correlate all their known stratigraphic units constituting the sedimentary section of the lake with their analogs in the onshore part of the Baikal rift zone, and compile the composite Cenozoic section. The following features of these sediments are noted: (1) as a whole, Pleistocene sediments are characterized by the hydromica-smectite composition of their clayey fraction with an insignificant share of kaoline; (2) the heavy fraction is dominated by the terrigenous epidote-amphibole association poorly resistant to weathering; (3) Pleistocene sediments of the lake contain siderite, vivianite, pyrite, and goethite concretions and micrometeorites, in addition to well-known ferromanganese nodules; (4) the presence of relict palynomorphs in Pleistocene sediments of Baikal is determined by their erosion from Miocene and Pliocene cavernous clays cropping out on underwater slopes of the Posol’skaya Bank and subsequent reburial along with Pleistocene palynological assemblages.

Accounting for evolving pore size distribution in water retention models for compacted clays

SummaryWater retention in compacted clays is dominated by multi‐modal pore size distribution which evolves during hydro‐mechanical paths depending on water content and stress history. A description of the evolutionary fabric has been recently introduced in models for water retention, but mostly on a heuristic base. Here, a possible systematic approach to account for evolving pore size distribution is presented, and its implications in models for water retention are discussed. The approach relies on quantitative information derived from mercury intrusion porosimetry data. The information is exploited to introduce physically based evolution laws for the parameters of water retention models. These laws allow tracking simultaneously the evolution of the aggregated fabric and the consequent hydraulic state of compacted clays. The influence of clay microstructure, mechanical constraints and water content changes on the water retention properties is highlighted and quantified from experimental data on different compacted soils with different activity of the clayey fraction. The framework is discussed with reference to a widespread water retention model and validated against experimental data on a Sicilian scaly clay compacted to different dry densities and subjected to a number of hydro‐mechanical paths. Copyright © 2014 John Wiley &amp; Sons, Ltd.

The long-term accelerated expansion of various ladle-furnace basic slags and their soil-stabilization applications

Ladle furnace basic slag (LFS) is a by-product of the steelmaking industry that can be used in civil works, especially for soil stabilization. This sustainable application is based on the reactivity of certain compounds at ambient temperatures such as calcium aluminates, free calcium oxide and free magnesium oxide. These compounds show hydraulic reactivity and subsequent interaction between each other and with the clayey fraction, resulting in improvements to the geotechnical properties of the soil such as its bearing capacity and free swelling.This study looks at the long-term aging reactions of LFS and the properties of various soil–LFS mixes, to gain further knowledge of the behaviour of this by-product as a construction and building material and the inherent risk of volumetric instability associated with its use. The final conclusion is that LFS can be applied in soil stabilization as efficiently as conventional soil stabilizers.