Hasil untuk "Mineralogy"

D. Mittlefehldt, T. Mccoy, C. Goodrich et al.

Yaocheng Wang, Xiong Xie, Xin Wang et al.

Carbonation has been considered an effective approach to improve quality of steel slag (SS) as supplementary cementitious material in concrete manufacture and relief overall CO2 emission. To reveal impact of carbonation degree on properties of SS, experiments regarding effects of carbonation duration, pressure and liquid-solid ratio (L/S) were conducted. Also, mineralogy and morphology of SS during the carbonation process and impacts on properties of cementitious materials were compared. Results showed that CO2 uptake rate could reach 12.06 % after a 2 h treatment with the pressure and L/S of 0.3 MPa and 0.2, respectively. The carbonation treatment decreases contents of f-CaO and C2S in SS, yield CaCO3 and SiO2 gel; surface roughness is increased, leading to an elevated water requirement of normal consistency, extended setting times and higher rheological yield stress; resolves retarding effect of SS on cement early hydration. Furthermore, carbonation treatment improves SS activity, a high carbonation degree enhances compressive strength and reduces porosity in cementitious materials, attributed to SiO2 gel and nucleation effect of CaCO3.

Q. Williams, E. Garnero

Fabrício de Araújo Pedron, Gabriel Antônio Deobald, Paulo Ivonir Gubiani et al.

ABSTRACT Regosols (Neossolos) are soils with use limitations mainly related to effective depth, abundant presence of rock and saprolite fragments, and frequently high slope gradients; besides that, they represent a new agricultural frontier for grain production in southern Brazil. This study evaluated soil saturated hydraulic conductivity (Ksat) and water retention and availability in Regosols and saprolites derived from volcanic rocks in southern Brazil and the relationship of these variables with porosity in saprolithic horizons characterized by mineralogical weathering. The study was carried out on eight profiles derived from basic and acidic volcanic rocks of the Serra Geral Formation. We evaluated soil morphology, granulometry, porosity, bulk density (BD), Ksat, water retention, electronic/ optical microscopy and chemical composition of parent materials, and soil mineralogy. Soil Ksat ranged from 0.0 to 6.40 cm h-1 in the evaluated horizons, without significant difference between the A and Cr horizons. Seven soil profiles showed BD equal to or less than 1.28 Mg m-3 for the Cr samples. Total porosity in the Cr horizons was above 0.5 m3 m-3 and not significantly different from A horizons. In five of the eight soil profiles, one or more Cr horizons presented greater available water than A horizons. Electronic and optical microscopy evidenced abundant cracks and mineralogical weathering in the rock samples. X-rays diffraction data also indicated advanced degree of weathering of Cr horizons, evidencing abundant formation of pores in the saprolite. and justifying the high-water retention in Regosols profiles in southern Brazil.

Utkarsh, Pradeep Kumar Jain

This paper discusses efforts made by past researchers to steady the expansive (problematic) soils using mechanical and chemical techniques - specifically with EPS beads, lime and fly ash. Administering swelling of problematic soils is critical for civil engineers to prevent structural distress. This paper summarizes studies on reduction of swelling potential using EPS, lime and fly ash individually. Chemical stabilization with lime and fly ash are conventional methods for expansive soil stabilization, with known merits and demerits. This paper explores the suitability of different materials under various conditions and stabilization mechanisms, including cation exchange, flocculation, and pozzolanic reactions. The degree of stabilization is influenced by various factors such as the type and amount of additives, soil mineralogy, curing temperature, moisture content during molding, and the presence of nano-silica, organic matter, and sulfates. Additionally, expanded polystyrene (EPS) improves structural integrity by compressing when surrounded clay swells, reducing overall swelling. Thus, EPS addresses limitations of chemicals by mechanical means. Combining EPS, lime and fly ash creates a customized system promoting efficient, long-lasting, cost-effective and eco-friendly soil stabilization. Chemicals address EPS limitations like poor stabilization. This paper benefits civil engineers seeking to control expansive soil swelling and prevent structural distress. It indicates potential of an EPS-lime-fly ash system and concludes by identifying research gaps for further work on such combinatorial stabilizer systems.

G. Henderson, F. Groot, B. Moulton

P. Biscaye, F. Grousset, M. Revel et al.

R. P. G, D. Viete, Bailin Chen et al.

Andrei V. Korsakov, Denis S. Mikhailenko, Le Zhang et al.

The mineralogical and geochemical features of diamond-bearing tourmaline crystals (schorl-uvite series) from garnet-clinopyroxene rocks of the Kumdy-Kol deposit (Northern Kazakhstan) have been studied in detail. The formation of the main rock-forming minerals (garnet + K-bearing clinopyroxene) occurred in the diamond stability field at 4-6 GPa and 950-1000 °C. Crystallization of K-bearing clinopyroxene at these parameters is possible in the presence of an ultra-potassic fluid or melt formed because of crustal material melting in subduction zones. Tourmaline crystals (up to 1 cm) containing diamond inclusions perform veins crosscutting high-pressure associations. The composition of individual zones varies from schorl to uvite within both a single grain and the sample as a whole. The potassium content in this tourmaline does not exceed 0.1 wt.% K2O, and the isotopic composition of boron  δ11B varies from –10 to –15.5 ‰, which significantly differs from the previously established isotopic composition of boron in maruyamaite crystals (δ11B 7.7 ‰ in the core and –1.2 ‰ in the rim) of the same deposit. Analysis of the obtained data on δ11B in the tourmalines from the diamond-grade metamorphic rocks within the Kumdy-Kol deposit suggests the existence of two boron sources that resulted in crystallization of K-bearing tourmaline crystals (maruyamaite-dravite series) and potassium-free tourmalines of the schorl-uvite series.

Tõnu Meidla, Leho Ainsaar, Olle Hints et al.

Ordovician rocks are widely distributed in the Baltoscandian region as well as in Poland, Belarus, Ukraine and Moldova. The Ordovician studies in this area were initiated in the 19th century in the outcrop belt in northern Estonia. The strata are well accessible here and fossils and sedimentary structures are excellently preserved. Further south, in other countries, the succession is lying progressively deeper (up to 2500 m) in the subsurface, except for limited exposure in Ukraine. The thickness of the Ordovician within the Estonian outcrop area reaches about 100 m but exceeds 200 m in several parts of the subsurface area. Since the 1960s, several Ordovician correlation charts have been compiled for this area. Recent developments in the stratigraphy are summarised in the volume ‘A Global Synthesis of the Ordovician System: Part 1’ (Geological Society, London, Special Publication, 532). The system of bio-, litho- and chronostratigraphic units is highly detailed in the area. The regional stages defined in Estonia were introduced for the western part of the East European Platform in the 1980s. The correlation of the regional succession to the global stratigraphic standard is generally well constrained, although it still needs to be refined in some details. A novel element of the stratigraphic standard, the isotopic zones, is based on secular variations of stable carbon isotopic composition of bulk carbonates and allows amendments to the correlation of strata. The application of a regular timescale is based on a well-dated system of biostratigraphic marker levels that were traced into the Baltic Palaeobasin and further to the south. The dated boundaries were tied to the regional succession mainly based on the correlation of conodont, chitinozoan and graptolite zones, but also using chemostratigraphic events. Correlation of formations to the chronostratigraphic standard in ten subregions (North and Central Estonia, South Estonia together with West Latvia and West Lithuania, Kaliningrad Region, East Latvia, Central Lithuania, East Lithuania together with northwestern Belarus, southwestern Belarus, West Volyn and Podillya together with East Volyn and Moldova) is summarised in an emended correlation chart. Development of the subregional correlation charts was well coordinated before the 1990s and the charts were based on a unified nomenclature of lithostratigraphic units for major facies zones that crossed the national borders. Trends in the development of nomenclature and correlation of formations have been different in different countries after 1991. This resulted in increasing differences in nomenclature and rank of lithostratigraphic units in subregions and led to an increase of the number of subregions. The development towards a more detailed stratigraphic classification in Lithuania has elevated the rank of many former units (several formations are now ranked as superformations, etc.). In 2011, a completely new system of formations and members replaced the formerly applied standard in the Kaliningrad Region. The climatic history of the region presented in papers of the last decades is modified in the light of the newest results of isotope-geochemical studies on Baltoscandian sections, which do not support the idea of gradual warming throughout the Middle and Late Ordovician in the region. The global cooling trend was also influencing Baltica despite the continental drift towards the lower latitudes. The richly fossiliferous regional succession has been extensively studied, but analyses with a broader view have been sparse. According to the general understanding, backed by data on different fossil groups, the main origination episodes in the early Darriwilian and Darriwilian–Sandbian transition led to the peak of regional diversity in the early Sandbian. Remarkable extinction events known from the early Darriwilian, early Sandbian and early Katian are expressed to a different degree in different fossil groups. The major extinction event in the latest Katian–Hirnantian, which impacted all major invertebrate groups, has been ascribed to the Hirnantian glaciation, the related glacioeustatic sea-level fall and the repeated rapid rearrangement of facies. A recovery that started in the latest Ordovician was relatively slow. Significant spatial differences in the dynamics of biodiversity within the eastern Baltic area and between this area and Scandinavia are considered partly due to uneven data coverage.

R. Fandrich, Ying Gu, D. Burrows et al.

A. King, H. Bates, D. Krietsch et al.

We report new mineralogical, petrographic and noble gas analyses of the carbonaceous chondrite meteorites Y-82162 (C1/2ung), Y-980115 (CI1), Y-86029 (CI1), Y-86720 (C2ung), Y-86789 (C2ung), and B-7904 (C2ung). Combining our results with literature data we show that these meteorites experienced varying degrees of aqueous alteration followed by short-lived thermal metamorphism at temperatures of >500 °C. These meteorites have similar mineralogy, textures and chemical characteristics suggesting that they are genetically related, and we strongly support the conclusion of Ikeda (1992) that they form a distinct group, the CYs (“Yamato-type”). The CY chondrites have the heaviest oxygen isotopic compositions (δ17O ˜12‰, δ18O ˜22‰) of any meteorite group, high abundances of Fe-sulphides (˜10 ‒ 30 vol%) and phosphates, and contain large grains of periclase and unusual objects of secondary minerals not reported in other carbonaceous chondrites. These features cannot be attributed to parent body processes alone, and indicate that the CYs had a different starting mineralogy and/or alteration history to other chondrite groups, perhaps because they formed in a different region of the protoplanetary disk. The short cosmic-ray exposure ages (≤1.3 Ma) of the CY chondrites suggest that they are derived from a near-Earth source, with recent observations by the Hayabusa2 spacecraft highlighting a possible link to the rubble-pile asteroid Ryugu.

C. Butt, Dominique Cluzel

T. Goudge, R. Milliken, J. Head et al.

D. A. Paige, M. Foote, B. Greenhagen et al.

The Diviner Lunar Radiometer Experiment on NASA’s Lunar Reconnaissance Orbiter will be the first instrument to systematically map the global thermal state of the Moon and its diurnal and seasonal variability. Diviner will measure reflected solar and emitted infrared radiation in nine spectral channels with wavelengths ranging from 0.3 to 400 microns. The resulting measurements will enable characterization of the lunar thermal environment, mapping surface properties such as thermal inertia, rock abundance and silicate mineralogy, and determination of the locations and temperatures of volatile cold traps in the lunar polar regions.

C. Gunawardana, A. Goonetilleke, P. Egodawatta et al.

R. Morris, D. Vaniman, D. Blake et al.

E. Garzanti, S. Andó, C. France‐Lanord et al.

Nataliya Kryuchenko, Edward Zhovinsky, Petro Paparyga

The results of studies of chemical pollution (Pb, Zn) of perennial grasses—Elymus repens L., Artemisia absinthium L., and Hypericum perforatum L.—on background plots and within the areas of impact of industrial enterprises in Kropyvnytskyi (Ukraine) are presented. It is noted that chemical pollution is the most dangerous. The activity of enterprises is considered, in the result of which heavy metals enter the air. Testing of plants (stems and leaves) was carried out at a distance of 10–100 m from the enterprises. The content of heavy metals in the aboveground part of plants was analysed by atomic absorption spectrophotometer in the laboratory of the Department of Exploratory and Ecological Geochemistry, IGMR NAS of Ukraine. The comparison of sorption properties of different plants in the same phases of development allowed plants with bioindication capabilities to be identified. The results of the analysis showed that plants most effectively accumulate the maximum amount of heavy metals from the atmospheric air at the end of the summer dormancy phase (second half of August). At this time the plant requires the minimum amount of nutrients that it takes from the soil. Stems and leaves of perennial grasses actively accumulate aerosols and fine dust on their surface due to plant secretions with the formation of a mucous film that actively adsorbs heavy metal ions. The background, minimum, and maximum content of heavy metals in plants is determined. Comparing the content of heavy metals in plant samples in the background and study plots, it was found that E. repens near industrial enterprises is the most effective bioindicator of air pollution. In order to determine the level of atmospheric air pollution using bioindication methods, the index of plant contamination (Sр) was proposed, which is the ratio of concentration coefficient of heavy metals and their amount. An assessment scale for atmospheric air pollution with heavy metals has been developed based on the contamination index (Sр) of bioindicator plants: the degree of pollution is 1–3—weak, 3–6—medium, 6–9—strong, more than 9—very strong. The proposed coefficients allow for conducting a situational assessment of atmospheric air pollution with heavy metals using bioindication methods.

Eyyüb Karakan

In geotechnical engineering applications, it is very important to obtain the undrained shear strength of remolded soils accurately and reliably. This study aims to obtain a trustworthy solution to determine the undrained shear strength of remolded clay mixtures using Atterberg limit test results in various states of consistency. An experimental study was carried out involving a wide range of clay mixtures of varying plasticity and geological origin. In the analyses, the variation in the undrained shear strength of remolded soil depending on the cone penetration depth, water content, flow index, liquidity index and log liquidity index was investigated. In the study, the highest undrained shear strength of 100% Na-montmorillonite (<i>NaM</i>) was obtained at 171.89 kPa and 56.60% water content, while the lowest undrained shear strength was obtained for 100% Sepiolite (<i>S</i>) at 9.28 kPa and 31.65% water content. The results of this study revealed that the shear strength is significantly affected by soil conditions, rather than dominant clay mineral. Moreover, it was observed that the undrained shear strength at the plastic limit was approximately 30–35 times greater than that at the liquid limit. Equations for liquid limit–flow index and plasticity index–flow index were proposed. It was concluded that the interdependence between undrained shear strength, liquidity index, log liquidity index and flow index is not unique due to the different physical and chemical properties of clays.