High Kaolinite Content Research Articles

Mineralogical Characterization and Geochemical Signatures of Supergene Kaolinitic Clay Deposits: Insight of Ropp Complex Kaolins, Northcentral Nigeria

This study presents the chemical and mineralogical composition of clay deposits and associated rock types within the Ropp Complex in order to assess the influence of parent lithology on the kaolinization, genesis, and utility of the deposit. Representative kaolin samples from E horizons of the weathering profiles and their bedrocks were collected from six sites in the Ropp Complex. Clay mineralogy was determined via the XRD technique, while a geochemical analysis was conducted using XRF, SEM coupled with EDS, and ICP-MS. The results showed that all kaolins dominantly contain kaolinite with a content of 77%–98% except for the AS1 kaolin with only minor kaolinite (20%) but mainly illite (65%). The notably lower crystallinity of kaolinite (HI value of 0.53–1.1) as well as its markedly small grain size is consistent with the formation of kaolinite from intensive chemical weathering of igneous rocks. The AS1 kaolin was probably formed from hydrothermal alteration in the burial stage due to the heating of groundwater by the late volcanism. Mobile trace elements (Sr, Ba, and Eu) exhibited a depletion trend, while immobile elements (Hf, Ta, Th) showed enrichment. The relatively more zirconium in kaolins implies the formation of low-temperature kaolinization. The notably high kaolinite content, accompanied by reasonable levels of Fe2O3 and TiO2, signifies a medium-grade quality. Furthermore, chondrite-normalized rare earth element (REE) patterns exhibit congruent trends in rocks and kaolin samples, indicating a relative enrichment in light rare earth elements (LREEs) alongside a discernible negative Eu anomaly. The abundant kaolinite and silicon–aluminum composition make the kaolins suitable for refractories, pharmaceutics, cosmetics, and supplementary cementitious material (SCM).

Influences of metakaolin and calcined clay blended cement on chloride resistance and electrical resistivity of concrete

There are many different grades of kaolinite clays around the world. Low-grade kaolinite clay is more abundant than high-grade kaolinite clay in various regions. To aim toward the utilization of low-grade kaolinite clay having an original kaolinite content of about 40% to produce calcined clay, this paper investigated the durability properties of concrete incorporating calcined clay produced from high-grade kaolinite clay or high kaolinite content (commercially available metakaolin or CC1) and calcined clay produced from a low-grade kaolinite clay (CC2). Concrete mixtures were designed to have a water-to-binder ratio of 0.60. A fly ash-to-binder ratio of 0.20 and calcined kaolinite clay-to-binder ratios of 0.10 and 0.20 were studied. The chloride penetration resistance and the electrical resistivity of concrete were assessed, while the mercury intrusion porosimetry (MIP) was utilized in evaluating the pore structure of concrete. The test results revealed that concrete with CC1 and CC2 exhibited superior chloride penetration resistance and chloride binding capacity than OPC and FA20 concretes. Moreover, using a higher calcined clay-to-binder ratio resulted in a more refined pore structure, which significantly enhanced the chloride resistance of concrete. Although CC2 revealed less performance in improving chloride resistance than CC1, it had superior performance compared to fly ash.

Byrd Ice Core Debris Constrains the Sediment Provenance Signature of Central West Antarctica

AbstractProvenance records from sediments deposited offshore of the West Antarctic Ice Sheet (WAIS) can help identify past major ice retreat, thus constraining ice‐sheet models projecting future sea‐level rise. Interpretations from such records are, however, hampered by the ice obscuring Antarctica's geology. Here, we explore central West Antarctica's subglacial geology using basal debris from within the Byrd ice core, drilled to the bed in 1968. Sand grain microtextures and a high kaolinite content (∼38–42%) reveal the debris consists predominantly of eroded sedimentary detritus, likely deposited initially in a warm, pre‐Oligocene, subaerial environment. Detrital hornblende 40Ar/39Ar ages suggest proximal late Cenozoic subglacial volcanism. The debris has a distinct provenance signature, with: common Permian‐Early Jurassic mineral grains; absent early Ross Orogeny grains; a high kaolinite content; and high 143Nd/144Nd and low 87Sr/86Sr ratios. Detecting this “fingerprint” in Antarctic sedimentary records could imply major WAIS retreat, revealing the WAIS's sensitivity to future warming.

High activity pozzolan obtained from selection of excavation soils in a Construction and Demolition Waste landfill

Excavations soils from construction sites, when included as Construction and Demolition Waste (CDW) can double waste amount and represent up to 80 % of waste composition. Limited recycling strategies are available for the material. In this work, soils with higher kaolinite contents were selected by X-ray diffraction (XRD) to produce high activity pozzolan. Twenty soil samples were collected in an inert CDW landfill, and seven samples (one-third of the total) containing higher kaolinite content were composed as a single sample for thermal and mechanical activation as pozzolan. At the temperature of 600 °C, low crystallinity kaolinite was transformed into amorphous material (37 % g/g) achieving the highest pozzolanic activity [consumption of 519 mg Ca(OH)2/g of the sample]. The replacement of Portland cement by calcined soil (6, 10 and 18 %) had no significant rheological impact on the water to solid ratio and optimal dispersant content and affected slightly the heat and setting time of the pastes; therefore, workable, and technically applicable. The Portland cement replacement by calcined soil, despite a fixed water to solid ratio of 0.3 led to an increase in the water to cement ratios and in the porosities of the pastes. Due to the pozzolanic reaction, 6 and 10%-replacement of Portland cement by calcined soil did not impair the tensile strength of the pastes when compared to that of Portland cement paste. A 42-MPa 28-day age blended Portland with calcined soil might be feasible to produce regarding Brazilian cement industry standard.

Performance of a Single Source of Low-Grade Clay in a Limestone Calcined Clay Cement Mortar

The high kaolinite content of metakaolin makes it valuable to other industries, thereby affecting its availability and affordability for the production of limestone calcined clay cement (LC3). This work presents a study on the potential utilization of low-grade clay in place of pure metakaolin in the preparation of LC3 for mortar formulations. CEM I was partially substituted with calcined clay and limestone by 20, 30, 40, and 50 wt.%. The weight ratio of calcined clay and limestone was maintained at 2:1 for all mixes and the water-to-binder ratio was 0.48. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and isothermal conduction calorimetry were used to study the hydration process and products after 28 days. Mechanical and durability assessments of the LC3 mortar specimens were conducted. LC3 specimens (marked LC20%, LC30%, LC40%, and LC50%) trailed the control sample by 1.2%, 4%, 9.8%, and 18%, respectively, at 28 days and 1.6%, 2.3%, 3.6%, and 5.5%, respectively, at 91 days. The optimum replacement of OPC clinker, calcined clay, and limestone was 20% (LC20%).

ИССЛЕДОВАНИЕ АРХЕОЛОГИЧЕСКИХ ОБРАЗЦОВ ДРЕВНЕЙ КЕРАМИКИ И ГЛИНИСТОГО СЫРЬЯ МЕСТОРОЖДЕНИЙ ЦЕНТРАЛЬНОЙ ЯКУТИИ

The paper considers the results of chemical and mineralogical analysis of ceramics of different times and deposits of clay raw materials of Central Yakutia. 7 ceramic fragments were examined, and a chemical and mineralogical analysis of three deposits of clay raw materials of the Republic of Sakha (Yakutia) was performed. The clay raw materials of Yakutia have a different chemical and mineralogical composition, depending on the deposit of raw materials. The studied clay raw materials can be used to recreate the ancient technology of ceramics. There is also a prospect for use in the ceramic industry. For a more detailed study, Kangalas clay raw materials were studied, this raw material is characterized by a high content of kaolinite, and it can be further used to create high-temperature ceramics. As a result of the conducted studies of samples of ceramic fragments, it was possible to find out the microstructure, chemical and mineralogical composition and temperature regime of firing of ceramic fragments. The ceramic samples have a common chemical and mineralogical composition. The conducted research allowed us to obtain detailed information on the manufacture of ceramic fragments from different eras. These results can be used for a deeper understanding of the ancient technology of ceramics production and will allow a broader disclosure of general and particular issues of the historical development of pottery in different regions of Yakutia

Desorption characteristic of oil from sludge surfaces under low-frequency ultrasound

Oil and solids in oily sludge have complex composition and exhibit strong interaction, which both make difficult the oil removal. In this paper, experiments focused on oil/solid property analysis and oil removal have been conducted to determine desorption characteristics of oily sludge in low-frequency ultrasonic fields. Polar components have a high fraction of heteroatoms that form strong van der Waals forces and hydrogen bonds with solid particles. In comparison to nonpolar, polar components were found to be less desorbed from solid surfaces in the ultrasonic field. Metals in kaolinite had strong electrostatic interactions with carboxylic acid in oil. In addition, porous structure of kaolinite increased the re-adsorption probability of oil. In comparison to quartzite, kaolinite showed lower oil removal efficiency. Therefore, higher acoustic intensity with shorter treatment time was found to be effective for oily sludge with high content of polar components and kaolinite at constant energy.

Change of sediment transport direction within the Rio Jaguaribe estuary, NE Brazil, by means of clay mineralogical analyses

The estuary of the Rio Jaguaribe (NE Brazil) is filled by a sediment sequence of more than 23 m and characterised by estuarine plains that – today - extend 30 km upstream.We investigated the sedimentary dynamics in the Rio Jaguaribe estuary since the early Holocene by means of clay mineralogical analyses, as well as sediment analyses from 11 sediment cores. The clay mineralogical approach proves to provide the most robust results. A transition of the illite/kaolinite peak area ratio from 0.3 to 1.8 within the vertical depositional record suggests a change of sediment transport direction over time. Whereas in the lower sequence marine influence dominates, characterised by the relatively high kaolinite content originating from the weathered Barreira formation at the coast, in the upper sequence sediments of fluvial origin dominate, which are characterised by the relatively high illite content originating from the crystalline rocks in the source area of the Jaguaribe river. The depositional architecture of the Holocene sediments of the Jaguaribe estuary shows a seawards prograding infill, assumed to have occurred since the mid-Holocene and supports studies suggesting a stagnating or slightly falling relative sea level (RSL) since ∼7000 BP.

Microstructure Investigations of Natural Clay From Pattallassang District, Takalar Regency, South Sulawesi Province, Indonesia

The study aimed to investigate the microstructure of natural clay from Pattallassang District, Takalar Regency, South Sulawesi Province. The clay was characterized using X-ray diffractometer (XRD), surface area analyzer (SAA), and scanning electron microscope (SEM). The XRD analysis showed that the main mineral composition of the clay was kaolinite, quartz, hematite, geothite, magnetite, and anatase phases. The SAA using BET analysis shows the large surface area of 59.26 m2/g and BJH analysis for pore distribution of 32.77 nm. SEM observations revealed that the clay consists of plate-like kaolinite particles arranged randomly. The results indicate that the natural clay from Pattallassang District has good potential for use in various industrial applications due to its high kaolinite content and favorable microstructure.Keywords: kaolinite, microstructure, mineral, clay.

Study of Structural Transformation and Chemical Reactivity of Kaolinite-Based High Ash Slime during Calcination

The transformation of kaolinite into metakaolinite by thermal activation to obtain highly active aluminosilicate is commonly known. In addition to kaolin, the high content of kaolinite in coal mining waste is another potential source for obtaining an aluminosilicate precursor, thereby protecting the environment and adding value to industrial wastes. In this paper, the kaolinite-based high ash slime (KAS) was calcined at temperatures ranging from 400 °C to 1000 °C under air, N2, and CO2 atmospheres, respectively. The thermal behaviors and structural evolution of each component in KAS were analyzed by thermal analysis (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Moreover, the chemical reactivity of Al2O3 and SiO2 in calcined KAS was evaluated by HCl and NaOH leaching methods. The results show that the applied KAS in this study primarily consisted of kaolinite and carbon, while the minor mineral phases included quartz, calcite, and pyrite. Additionally, the structural transformation of kaolinite during calcination included dehydroxylation, sintering, and the formation of mullite. Crystalline kaolinite completely decomposed into semicrystalline metakaolinite at 600–800 °C, accounting for the increase in chemical reactivity. The interlayer sintering of metakaolinite and the recrystallization of amorphous components led to the decrease in chemical reactivity after 800 °C. Furthermore, the thermal behaviors of carbon in KAS are greatly affected by the calcination atmosphere. The presence of carbon reduced the chemical reactivity of calcined KAS.

Geotechnical investigations on Alccofine stabilized kaolin clay

Clay soil having high kaolinite content are strenuous to work with as it has low compressive strength and bearing capacity. They tend to cause failures in supporting structures and pavements overlying them. Chemical stabilization is a viable option to improve the strength of the clay. A new soil stabilizer made from processed GGBS, Alccofine 1109SS , is used for stabilization. Alccofine is being used as a micro filler for concrete. The same has been used in 3,6,9, and 12 % to prepare specimens, and these specimens were tested after controlled curing of 0,7,14 and 28 days. The geotechnical strengths of these specimens were tested for Unconfined compressive strength (UCS) and split tensile strength (STS). Mixing 12% of Alccofine led to an improvement of around 500 % in UCS strength fa or cud of 28 days. The UCS strength for K91A9 and K88A12 exceed 1700 kPa, recommended by IS code for sub-base courses in low-volume roads, and thus can be used for it. Soaked and unsoaked CBR values were found to have increased by more than 100 % than pure kaolin clay. Further, the morphological test results of SEM and XRD are discussed. The optimum recommended percentage of Alccofine to be used as a stabilizing agent considering economy and sustainability is 9 %.

Clay mineralogy mediated by pH and chemical weathering intensity of Permian–Triassic boundary K-bentonites at Dongpan (Guangxi, South China)

Volcanic ash deposits of the Permian-Triassic (P-T) transition in South China, in addition to being associated with the Permian-Triassic boundary mass extinction, are useful marker beds for regional correlation of sedimentary strata. This study investigates the source(s) of P-T volcanic ash layers in South China by studying their clay mineralogy and geochemical characteristics in deep-marine facies at Dongpan. Mineralogically, the Dongpan deposits consist mainly of clay minerals and quartz, with small amounts of anatase and feldspar. C lay minerals in the volcanic ash layer are mainly composed of R1 mixed-layer illite/smectite (I/S) (56.2–74.8%), smectite (14–22.8%), kaolinite (5.4–27.3%) and illite (1.2–5.3%). The relatively high content of kaolinite and weak illitization of smectite at Dongpan differ from the features of clay-mineral assemblages in other contemporaneous deep-water facies. Our results indicate that strong chemical weathering in an acidic and oxidizing environment characterized by low K+/H+ ratios inhibited uptake of K+ in the interlayers of I/S clay minerals and, thus, illitization of smectite. We infer that weathering intensity rather than redox state was the primary influence on the rate of kaolinization of clay minerals in these deep-marine facies. The Dongpan section exhibits a uniform REE pattern, indicating a single and stable source of volcanic ash during the P-T transition. Trace-element and REE distribution patterns and mixed-layer I/S clay-mineral morphologies are consistent with the source of the volcanic ash at Dongpan being a nearby continent-margin volcanism.

Fines effect on gas flow in sandy sediments using μCT and pore networks

Gas production from hydrate-bearing sediments requires methane dissociation, which induces two-phase gas flow, mobilizing fine clay particles from within saturated pores. Fines migration within sandy sediments results in subsequent pore clogging, reducing reservoir connectivity. Sediments complex pore morphology, require direct 3D microscopic pore-scale imaging to investigate fines' influence on the porous media. The work uses synchrotron microcomputed tomography, to understand how fines migration due to gas injection, affects pore morphology and gas connectivity within sandy sediments. The goal is to study the impact of fines type and content at different gas injection stages, on gas flow regime and sediments rearrangement.Six saturated samples of sand and fines mixtures (Kaolinite and Montmorillonite at different contents) underwent four stages of gas injection during in-situ 3D scanning. X-ray images were segmented for direct visualization, as well to quantify gas ganglia distribution, also to extract pore networks to statistically measure changes in pore and throats distributions, and to simulate single-phase and relative permeability.Findings reveal that the extent of deformation to pore morphology increases with fines content and gas injection regardless of fines type. High kaolinite content (equal to or larger than 6%) results in fractured porous media, while high montmorillonite content (equal to or larger than 5%) results in disconnected vuggy media. Lower contents cause a gradual reduction in pore and throat sizes during gas injection. As fines content increases, clogging intensifies, thus gas connectivity and flow regime changes from connected capillary to disconnected vugs and microfractures. Both hydrophobic and hydrophilic fines reduced throat sizes, due to dislocations in sand grains. A unique pattern is discovered using pore networks, which describe pore-size fluctuations during fractures and vugs formation, due to fines migration.

Depositional conditions of the Upper Cretaceous shales from the Anambra Basin, SE Nigeria: Constraints from mineralogy and geochemistry

Thirty-four core shale samples from the Upper Cretaceous Mamu Formation, southeastern Nigeria, were studied using XRD and geochemical analyses to constrain their provenance, tectonic setting, palaeoweathering and palaeoredox conditions during deposition. X-ray diffraction analysis revealed the presence of clay minerals (kaolinite, illite and illite-smectite mixed layer) and non-clay minerals (quartz and feldspar). The dominance of kaolinite and the high kaolinite/illite (K/I) contents indicate warm and humid climatic conditions during sediment accumulation. The total organic carbon (TOC) content of the shales ranges between 0.31 and 55.34%. The high Chemical Index of Weathering (CIW; mean∼98.8%), Chemical Index of Alteration (CIA; mean∼92%) and Plagioclase Index of Alteration (PIA; mean∼98.7%) for the shales, including a high content of kaolinite, indicate intense chemical weathering in the source area. The positive correlations between V, Cr, Ni, Co, Ga, Cd, Be, Sc, TiO2, MgO with Al2O3 and Ba with K2O suggest that these elements in the shales are mainly held in clay minerals. The elevated contents of Zr and the high Zr/Cr and Zr/Sc ratios imply that the shales were derived from predominantly felsic source rocks. However, TiO2/Zr and Y/Ni ratios suggest a derivation from an admixture of complex felsic and mafic basement rocks. The low average enrichment factor values of Mo (MoEF), V (VEF) and U (UEF), along with low concentrations of redox-sensitive trace element ratios (Mo/U, Ni/Co, V/Cr and Cu/Zn) and high TOC contents infer oxic conditions during deposition. Furthermore, Fe2O3–S-TOC relationships, along with DOPT, V/(V + Ni) and Fe2O3/Al2O3 ratios, suggest dominantly oxic to slightly dysoxic/anoxic conditions during the accumulation of the Mamu Formation shales. Binary plots of K2O/Na2O ratio versus SiO2 indicate a passive margin tectonic setting for the shales.

Effect of clay mineral content on soil strength parameters

The impact of clay mineralogy on engineering properties relevant to road design, such as the strength and stiffness of road materials, has recently been the subject of intensive investigations, aiming at providing indirect measures of soil performance out of mineralogical data. This study deals with the effects of clay minerals on soil strength, expressed in terms of California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS), and stiffness, represented by the constrained modulus, which are commonly used as engineering properties for pavement materials. The study is performed on six clayey soils (S1-S6) of different geographic origins. Five of the six soils are highly plastic, potentially swelling, and one is kaolinitic soil. The mineralogical characteristics of the samples were analyzed through X-ray diffraction (XRD). The testing program included Atterberg limits, sieve analysis, CBR, UCS, and consolidation tests. The measured properties of the samples were compared in light of the mineralogical composition of the soils. The investigation showed that the kaolinite mineral is significantly more effective than the montmorillonite in reducing the plasticity of the clays. Higher strength indicators (CBR and UCS) were observed for samples with high kaolinite content (S4, S5, and S6). Moreover, the kaolinitic soil samples are characterized by a larger constrained modulus (Ec) than the other samples.

Eocene Paleoclimate Evolution under the Background of Warmhouse-Hothouse Conditions in the Continental Fushun Basin: Implications from Magnetic Susceptibility and Color Reflectance.

Paleocene–Eocene hyperthermal events are a current research focus in the fields of sedimentology and paleoclimatology. The Fushun Basin in northeast China contains continuous continental Eocene fine-grained rocks, and a series of Eocene hyperthermal events in the Fushun Basin have been identified. Because of the high cost of high-precision isotope data testing, it is necessary to find new and alternative paleoclimate parameters. In this study, Eocene coal and oil shale-bearing layers in the Fushun Basin are used as research objects. The high-precision data of magnetic susceptibility, color reflectance, rock composition, and cluster analyses are used to conduct a vertical comparison in the same category and compare that analysis with the identified Eocene hyperthermal events in the Fushun Basin. The preliminary results show that high-frequency-dependent susceptibility, high color reflectance a* (redness)/L* (lightness) values, and high kaolinite content in the study area have good correspondence with global hyperthermal events and can be used as effective parameters for the identification of continental basin hyperthermal events. The detailed magnetic susceptibility and color reflectance data also reveal that the Eocene strata in the Fushun Basin recorded the Late Lutetian Thermal Maximum (LLTM) and 13 short-term hyperthermal events during the Early Eocene Climatic Optimum (EECO). These results indicate that the parameters of rock physical properties can be used to study the evolution of the paleoclimate in geological history, and it has universal practicability in continental and marine fine-grained sedimentary rocks.

Spatiotemporal Discharge Variability of the Doce River in SE Brazil During MIS 6 and 5

The modern precipitation balance in southeastern (SE) Brazil is regulated by the South American summer Monsoon and threatened by global climate change. On glacial-interglacial timescales, monsoon intensity was strongly controlled by precession-forced changes in insolation. To date, relatively little is known about the spatiotemporal distribution of tropical precipitation in SE Brazil and the resulting variability of fluvial discharge on glacial-interglacial timescales. Here, we present X-ray diffraction-derived mineralogical data for the 150–70 ka period (marine isotope stage (MIS) 6 to MIS 5) from the Doce River basin. This area was sensitive to changes in monsoonal precipitation intensity due to its proximity to the South Atlantic Convergence Zone. The data, obtained from a marine sediment core (M125-55–7) close to the Doce river mouth (20°S), show pronounced changes in the Doce River suspension load’s mineralogical composition on glacial-interglacial and precessional timescales. While the ratio of silicates to carbonates displays precession-paced changes, the mineralogical composition of the carbonate-free fraction discriminates between two assemblages which strongly vary between glacial and interglacial time scales, with precession-forced variability only visible in MIS 5. The first assemblage, dominated by high contents of kaolinite and gibbsite, indicates intensified lowland erosion of mature tropical soils. The second one, characterized by higher contents of the well-ordered illite, quartz and albite, points to intensified erosion of immature soils in the upper Doce Basin. High kaolinite contents in the silicate fraction prevailed in late MIS 6 and indicate pronounced lowland soil erosion along a steepened topographic gradient. The illite-rich mineral assemblage was more abundant in MIS 5, particularly during times of high austral summer insolation, indicating strong monsoonal rainfall and intense physical erosion in the upper catchment. When the summer monsoon weakened in times of lower insolation, the mineral assemblage was dominated by kaolinite again, indicative of lower precipitation and runoff in the upper catchment and dominant lowland erosion.

Granite-bauxite provenance of abnormally enriched boehmite and critical elements (Nb, Ta, Zr, Hf and Ga) in coals from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, China

Critical elements in coal have attracted much attention in recent years as some coals and coal combustion products may provide an alternative source of these. This paper provides mineralogical and geochemical data on the No. 4 coal seam, the major minable coal from the Eastern Surface Mine, Ningwu Coalfield, Shanxi Province, northern China. It also discusses the provenance of mineral matter, the origin of aluminum minerals (boehmite), carbonates (calcite and ankerite) and phosphates (goyazite) and the potential economic significance of critical elements (e.g., Al, Nb, Ta, Zr, Hf, and Ga). Mineralogically, the studied coal samples are characterized by high kaolinite (64.7% on average, low-temperature ash basis) and boehmite (24.1%) contents, followed by carbonates (calcite, ankerite, siderite, and dolomite), titanium oxides (anatase and rutile), goyazite, quartz, and apatite. In comparison with average values for Chinese coals, the studied coal samples are characterized by high Al2O3 contents (mean 11.82% on a whole-coal basis and mean 49.49% on an ash basis). Compared with world hard coals, the No. 4 Coal is enriched in Ga, Se, Zr, Nb, La, Ce, Hf, Ta and Pb. In addition to Al, critical elements including Nb, Ta, Zr, Hf, and Ga in this coal have an economic significance. The Al2O3/TiO2 vs. Nb/TiO2, Al2O3/TiO2 vs. Zr/TiO2, Zr vs. Nb, Hf vs. Ta, and REY distribution patterns (REY, rare earth elements plus Y), indicate that the provenance of mineral matter (e.g., boehmite and critical elements Nb, Ta, Zr, Hf and Ga) in the No. 4 Coal is a number of sediment-source regions including the Neoarchean granites of the Yinshan Oldland, and the Paleoproterozoic granites and Benxi Formation bauxites (Late Carboniferous, to the northeast of the coal basin) of the northern Trans North China Orogen. Carbonate minerals (calcite and ankerite) are of epigenetic origin while the phosphate mineral (goyazite) was syngenetically deposited in the peat swamp during a period of a low water table.

Mineralogy and lithogeochemistry of lower Cretaceous kaolin deposits in the Malha Formation, Southwestern Sinai, Egypt: Implications for the building and construction industry

This study analyses the exposed outcrops of the Lower Cretaceous (Aptian-Albian) kaolin deposits of the Malha Formation, and characterizes them in terms of lithological, mineralogical, and chemical composition. In addition, the effect of thermal treatment on kaolinite mineral behavior is evaluated. The Malha Formation comprises kaolin deposits, which were sampled at the Rewekna, Ras Watta, Abu El-Nomerat, Essela, and Mosaba Salama sections. The studied samples are composed of kaolinite and quartz as the main constituents, followed by anatase and hematite as accessory (coloring) minerals. X-ray fluorescence (XRF) analysis reveals high Al2O3, SiO2, and LOI, low CaO, MgO, Cl, SO3, and P2O5 contents as well as alkali metals (e.g., K2O and Na2O). An increase in aluminum and silicon oxides is observed along with the presence of high kaolinite content in these samples. Calcination of the studied kaolinite, by thermal treatment, leads to dehydroxylation and/or transformation to High Reactive Metakaolinite (HRM). The partial replacement of cement by different ratios (3, 5, 10, 15, and 20%) of the produced Metakaolinite (MK) was completed to enhance the physical and mechanical properties. These procedures make the concrete more flexible and workable, increase durability, and are stronger. Besides, reduce the temperature produced from the hydration, as well as decreasing permeability and water absorption of the concrete. This work concludes that the cement substitution and mineral admixtures using Metakaolinite (MK) between 10 and 15% by weight of cement gave rise in compressive strength by 20% if compared by the control mix.

Pozzolanic and hydraulic activity of bauxite for binder production

Bauxite is mainly used to produce aluminium and calcium aluminate cements. Both applications carry high environmental impacts. However, the carbon emissions generated from mining bauxite (3–5 kg CO2e/t) are negligible when compared those generated for aluminium or cement production (620–700 kg CO2e/t for CEM II). Hence, an alternative use for bauxite would lower environmental impacts worldwide. This paper measures the pozzolanic and hydraulic capacity of raw and thermally activated bauxite with a view to use it, as a binder, in construction.The results indicate that the bauxite is pozzolanic and, when fired over 900 °C it becomes slightly hydraulic. An amorphous reactive phase begins to appear at 300 °C, but the lime binding potential is enhanced at 550 °C because most of the aluminium is in amorphous form. Some active phases (except for ϒ- Al2O3) could not be detected with XRD due to their amorphousness. However, their pozzolanicity was evidenced with direct and indirect measurements.The bauxite's pozzolanic and mechanical indices are high, comparable or superior to other pozzolanic and cementing materials. Gibbsite, boehmite and kaolinite are the main phases in the bauxite. Their layered atomic structures with high specific surface areas (SSA) and active surface hydroxyls that enhance adsorption, and hence nucleation, precipitation and dissolution, provide a high pozzolanic activity. The high kaolinite content, and the presence of the highly-reactive, kaolinite-polymorph nacrite, enhance reactivity, and the presence of sulphates also contributes to the initial activity.The SSA of the bauxite particles, is superior to CEM II and other pozzolanic and cementing materials, and heating, even at low temperature (300 °C), drastically increases the SSA of the particles (by∼60%). The methods that determine initial pozzolanic activity rate the 550 °C bauxite as the most active, while the mechanical methods rate the 700–800 °C bauxites as the most reactive. This is because the high SSA of the 550 °C bauxite enhances lime combination in the earlier stages of the pozzolanic reaction, while the 700–800 °C bauxite has the highest amorphous/active alumina content which control late pozzolanic activity. As evidenced with XRD, at 700–800 °C, boehmite has disappeared, transformed into amorphous transition aluminas, and kaolinite has completely turned into reactive metakaolin.