Kaolinite Content Research Articles

Optimisation of Using Low-Grade Kaolinitic Clays in Limestone Calcined Clay Cement Production (LC3).

LC3 (limestone calcined clay cement) is poised to become the construction industry's future as a so-called low-carbon-footprint cement. Research into this subject has determined the minimum kaolinite content in calcined clays to guarantee good mechanical performance. This study examines the use of clay from the Valencian Community (Spain), which has a lower kaolinite content than the recommended amount (around 30%) for use in LC3 and how its performance can be enhanced by replacing part of that clay with metakaolin. This study begins with a physico-chemical characterisation of the starting materials. This is followed by a microstructural analysis of cement pastes, which includes isothermal calorimetry, thermogravimetry, and X-ray diffraction tests at different curing ages. Finally, this study analyses the mechanical performance of standard mortars under compression to observe the evolution of the control mortars and the mortars with calcined clay and metakaolin over time. The results show that the LC3 mortars exhibited higher compressive strength in the mixtures with higher calcined kaolinite contents, achieved by adding metakaolin. Adding 6% metakaolin increased the compressive strength after 90 days, while 10% additions surpassed the control mortar's compressive strength after 28 days. Mortars with 15% metakaolin exceeded the control mortar's compressive strength after just 7 curing days. The hydration kinetics showed an acceleration of LC3 hydration with metakaolin additions due to the nucleation effect and the formation of monocarboaluminate and hemicarboaluminate (both AFm phases). The results suggest the potential for combining less reactive materials blended with highly reactive materials.

Spatial and temporal variability of physicochemical characteristics in Lancang River sediments amid hydropower development

The construction of river dams disrupts river continuity and sediment transport, altering the riverbed between sediment “sources” and “sinks” and changing the sediment characteristics of the river. In this study, 256 sediment samples from 54 major control cross-sections of the Lancang River (LCR) were analyzed to examine the spatial and temporal distribution of clay and non-clay minerals in the sediment and their relationship with the environmental changes caused by the construction 11 hydropower plants. The results indicate that the construction of terrace dams on the LCR interrupted the downstream refinement trend of sediments, which reappeared once the terrace reservoirs stabilized. Additionally, the interception of the dam increased the accumulation of clay mineral in sediments. From 2011 to 2023, the relative abundance of clay mineral in the regulated reaches (RRs) increased by 2.4 %, the quartz content decreased by 26.2 %, and the contents of calcite, mica, kaolinite, and chlorite increased, respectively. Consequently, the main non-clay mineral assemblage in the sediments shifted from quartz+feldspar to quartz+feldspar+mica. Furthermore, the clay mineral content was higher upstream the main dams (15.3 %) than downstream (14.8 %), with the sediment quartz and calcite contents being higher downstream, and mica and chlorite contents being higher upstream. The feldspar content showed a minimal change. However, the mineral composition of the sediments in individual reservoirs varied significantly, owing to the specific environmental conditions of each reservoir. The distribution of sediment clay also differed between the dry and rainy seasons. This study provides a scientific basis for managing reservoir sediment scheduling and regulating the ecological and environmental safety in watersheds.

Application of clay minerals in the synthesis of cretaceous mudstones and microstructural analysis of their deterioration mechanism

The Cretaceous mudstone undergoes significant argillization and disintegration when in contact with water due to its high content of clay minerals, posing a severe challenge to the stability of roadways in coal mines during construction and operation. This research aimed to prepare water-sensitive mudstone–like materials by the method of clay mineral composition similar to that of natural Cretaceous mudstone to reproduce the mechanical and hydraulic properties of natural rocks and meanwhile reveal the deteriorating effect of clay minerals on its microstructure and macroscopic properties. Using binary clay-gypsum mixtures and considering the aggregate-binder ratio, the clay-gypsum ratio, the iron sand content in fine sand, and the powder sand content in aggregate as controlling factors, 16 groups of proportioning schemes were established using the orthogonal test method and a series of physic mechanical experiments were conducted to determine its mechanical and hydraulic properties. Subsequently, sensitivity analysis was applied to characterize the effects of different influencing factors on mudstone-like materials’ mechanical and hydraulic properties. The result shows that the distribution ranges of physical, mechanical, and hydraulic parameters of the newly prepared similar material overlap noticeably with those of the natural mudstone, suggesting that this new material can better meet the requirements of modeling natural mudstone. In addition, the range analysis showed that the aggregate-binder ratio was the dominant factor for the material’s UCS, E, and cohesion, while the clay-gypsum ratio had a significant effect on its density and disintegration time. Then, qualitative and quantitative microstructural analysis was carried out on the SEM images of the four samples based on kaolinite-gypsum binary mixtures by Avizo software via the dynamic threshold segmentation method. The result indicates that the material microscopic parameters, such as pore size distribution, equivalent diameter, porosity, fractal dimension, etc., are significantly altered with the increase of kaolinite content, resulting in a marked deterioration of the material’s micromechanical properties. This mineralogical and microstructural change transforms the cementation type from homogeneous and dense crystalline cementation to anisotropic and loose argillaceous cementation, exhibiting strong water sensitivity and extremely weak macro mechanical properties, which explains the deterioration and disintegration mechanism of natural mudstones from a micro mineralogical point of view. Importantly, the synthesis and microstructural analysis method based on mineralogy proposed in this study may be widely employed in rock mechanics and engineering.

Enhancing the properties of high-density oil well cement with Qusaiba kaolinite

High-density cement slurries used in oil well cementing often face challenges such as particle settling, poor rheological properties, permeability, and compressive strength degradation, which can compromise zonal isolation and well integrity. This study focuses on using kaolinite, a clay mineral, as an additive due to its potential to improve the performance of high-density cement by modifying key properties. Several concentrations of kaolinite were examined to evaluate their influence on several cement properties such as rheology, thickening time, permeability, porosity, and compressive strength. Additionally, it assesses the impact of kaolinite on cement sheath solids settling using both conventional methods and nuclear magnetic resonance (NMR). The results revealed that an optimal concentration of 1% kaolinite by weight of cement (BWOC) significantly reduced particle settling by 74.4%, enhanced compressive strength by 13%, and lowered permeability and porosity by 74% and 7%, respectively. Additionally, kaolinite improved rheological properties by an 8.4% reduction in plastic viscosity, a 19.4% increase in yield point, and a 30% increase in gel strength. Kaolinite also acted as a retarder, increasing thickening time. These improvements contribute to better cement sheath integrity and wellbore stability, highlighting kaolinite’s potential as an effective additive for high-density cement.

Integrating rhizosphere bacterial structure and metabolites with soil Cd availability in different parent paddy soils

Soil bacterial community structure and rhizosphere metabolites are important pathways for rice to respond to external Cd stress. The specific correlations between these microorganisms, metabolites and inherent soil properties, as well as the mechanisms they utilize to regulate Cd availability across different parent soils remain underexplored, emphasizing the need for deeper understanding to inform effective soil management strategies. In this study, five typical parent soils with large differences in properties (quaternary red clay soil (hereby defined as Q), granite soil (G), river sandy mud (R), yellow mud soil (Y), stucco field (S)) in Chinese paddy soils were collected, and extra Cd were added (CK: 0 mg·kg−1, Cd: 2.4 mg·kg−1).The result indicated that the toxicity impact of Cd in rice grains in G was the weakest, and the highest Cd bioavailability in S. The abundance of Proteobacteria, Bacteroidota and Firmicutes showed an increasing trend in G, while they decreased significantly in S. The contents of Cis-9-palmitoleic acid and phosphoethanolamine increased by 170.02 % and 154.03 % in G, decreased by 218.62 % and 181.58 % in S. MBNT15 and Desulfobacterota showed a significant negative correlation with humic acid molecular weight (MW) extracted from parent soils and Clay (montmorillonite, illite, kaolinite) contents, while they exhibited a positive correlation with soil organic matter (OM) content (P < 0.01). The MW played a crucial role in shaping rhizosphere metabolites with R2 value of 0.8498. These results elucidate how soil bacterial communities, rhizosphere metabolites, and inherent soil properties interact to regulate Cd availability across different parent soils.

In-Depth Characterization of Natural Clays from Southeast Albania

Clays have been exploited in the manufacture of diverse products from ceramics to paints, pharmaceuticals, plastics, cosmetics, and more. Thus, they can be used in many industrial applications, showing good adsorbent ability thanks to their lamellar structure, high cation exchange capacity, pore size distribution, and large surface area. For this reason, considerable attention has been paid to their in-depth characterization, for further integration in sectors such as biomedicine, construction, remediation, aerospace, and nanotechnology. For this aim, two samples of natural clays, ALO1 and PRE4, from the southeast part of Albania, were subject to a multi-methodological characterization, with the aim of addressing the use of such geomaterials in possible sensing applications. X-ray fluorescence analysis, morphological characterization of the samples, and energy-dispersive system spectroscopy pointed to an extreme mineralogical variety, with kaolinite in AL01 and montmorillonite in PRE4 as the most abundant phases. This fact was further confirmed by powder X-ray diffraction, showing a quartz content of 20%, a kaolinite content of 64%, and a muscovite content of 16% for ALO1; meanwhile, for PRE4, we found a content of quartz of 45%, a content of montmorillonite of 34.9%, and a content of clinochlore of 20%. Infrared spectroscopy and thermal analyses confirmed the presence of hydroxyl groups in both samples, suggesting a higher content in ALO1. Measurement of N2 adsorption isotherms on the clay samples yields specific surface areas of 87 m2/g for PRE4 and 32 m2/g for ALO1, pore volumes of 0.721 cm3/g for PRE4 and 0.637 cm3/g for ALO1, and similar pore sizes in the range of 6–12 nm. Electrochemical analysis highlighted a good conductivity of ALO1 and PRE4 when used for the modification of commercial carbon-based screen-printed electrodes. In detail, higher currents were registered by differential pulse voltammetry for the electrodes modified with the clays with respect to bare electrodes, as well as good repeatability of the measurements. In addition, a comparative study with nanomaterials, known for their good conductivity, was achieved, using carbon black and gold nanoparticles as a reference, showing that the conductivity of the clays was lower than but not so different from those of the reference materials.

Feasibility study on the preparation of ternary blended cements with low-kaolinite calcined coal gangue and limestone

This paper presents a feasibility study on the production of ternary blended cements with low-kaolinite calcined coal gangue (CCG) and limestone, considering kaolinite contents varying from 11.7 % to 40.6 % in coal gangue (CG). The ternary systems were designed with 15 %, 30 %, 45 % and 60 % by mass of cement replaced by CCG and limestone with a fixed mass ratio of 2:1. The fluidity and compressive strength of the mortars were measured, followed by the strength efficiency analysis combined with CO2 emission. The potential hydration mechanism was revealed by analysing the hydration kinetics, hydrates and microstructural evolution of these ternary pastes. The results showed that it is possible to use low-kaolinite CCG and limestone to prepare ternary blended cements with adequate mechanical strength that can fulfill the 28-day strength requirement of 32.5 or 42.5 grade cement. In addition, Increasing the kaolinite content in CG can increase the substitution of cement up to 60 %. Microstructural studies indicated that the compressive strength of these ternary mortars at 3 and 7 days was mainly dominated by cement hydration and the pozzolanic reaction between CCG and portlandite (CH), respectively. The precipitation of carboaluminates from the synergy of CCG and limestone significantly reduced critical pore size and increased the volume fraction of fine capillary pores from 7 days, well supporting the strength development of the ternary mortar. The findings of this work underscores the potential of using low-kaolinite CCG as a supplementary cementitious material (SCM) to reduce carbon footprint in the field of construction, and also in contributing to a high-value green utilization of solid waste.

Clay mineral composition and transport pattern of surface sediments in the Ganges Submarine Delta

The Ganges Submarine Delta is a key land-sea transitional area in the northeastern Indian Ocean. An understanding of sediment distribution, provenance, and transportation in this area is of great importance for understanding its sedimentary environment and the sediment “source-sink” system of the northeastern Indian Ocean. This study aimed to identify the provenances and transport patterns of fine-grained sediments in the Ganges Submarine Delta through analysis of the grain size and clay mineral content of 84 surface sediment samples. Sediment illite, chlorite, kaolinite, and smectite contents were ∼66%, 18%, 11%, and 5%, respectively. Sediment illite content decreased from north to south; smectite and chlorite decreased and increased from northwest to southeast, respectively; kaolinite content was highest in the south. Spatial cluster analysis of the four clay minerals grouped the study area into two provinces: province I in the north is characterized by a clay mineral assemblage similar to that of the Ganges-Brahmaputra rivers; province II in the south is characterized by deep water and changes to clay mineral characteristics due to the mixing of material originating from the Indian Peninsula. This study used the illite/(smectite + chlorite + kaolinite) and kaolinite/illite ratios to discuss sediment transport paths in the two provinces. Himalayan material is widely distributed throughout the study area, and mainly transported from the estuary to the southwestern area by the tides, plume, and monsoons; sediments of the Mahanadi river are transported from southwest to northeast by the southwest monsoon, thereby affecting the sediment composition of province II.

Characterization and processing of kaolin from southern Brazil for potential strategic application in the porcelain stoneware tiles manufacturing

The ceramic industry in the productive hub of Santa Catarina needs some raw materials with specific characteristics such as kaolin to manufacture its products. This clay mineral with a naturally variable chemical composition in relation to its geolocation (in extraction area composed by rock and combined with sediment materials), attributes significant increases in transport costs due to its distance from the main productive areas in southern Brazil. Thus, as a strategic alternative, the improvement of kaolin with a high quartz content (69.9%) from the northern region of the state of Santa Catarina (∼400 km from ceramic hub in the south of the state), more precisely from the municipality of Garuva, was sought. Unit processing operations by classifying this mineral for suitability for use in industry, resulted in an increase in the concentration of kaolinite. The results indicated that the proposed method reduced the amount of quartz and consequently increased the kaolinite content, resulting in an aluminum oxide content of approximately 28.20%, a value higher than the normal natural content of ∼19%.

Characteristics, main controlling factors and densification mechanisms of unconventional tight reservoirs in Triassic Yanchang Formation in southern Ordos Basin, China

The key factors controlling the densification of unconventional reservoirs (e.g., tight oil and gas reservoirs) remain poorly understood and directly affect the distribution of exploitable resources. Here, systematically explored reservoir characteristics, depositional microfacies, and the main factors controlling densification of the tight oil reservoir in the Chang 8 Member (Yanchang Formation, Middle Triassic) in the Zhenjing area of the southern Ordos Basin by thin section analysis, scanning electron microscopy, physical property measurement, X-ray diffraction, and mercury injection. Our results confirm the Chang 8 reservoir as an extremely low permeability tight sandstone reservoir mainly comprising lithic feldspathic sandstone with various primary and secondary pores and fine pore channels. The highest quality reservoir is mainly restricted to the middle and lower parts of subaqueous distributary channel microfacies. Dissolution partly contributed to reservoir formation, but the persistence of early, non-compressed storage space was more important. The compression of plastic rock debris removed a significant amount of porosity, and calcite and kaolinite both fill pores and contribute to the structural strength of pore space. We identified three densification processes: the persistent densification of highly plastic rocks, calcite cementation, and feldspar dissolution and subsequent kaolinite precipitation. After their compaction, the Chang 8 Member reservoirs were charged with hydrocarbons. We applied clustering analysis to eight reservoir characteristics (porosity, permeability, median pore-throat radius, maximum pore-throat radius, median capillary pressure, pore discharge pressure, chlorite content, kaolinite content) to quantitatively classify the Chang 8 reservoir into three categories. Type-I reservoirs have the best conditions for hosting tight oil reservoirs, with ∼12% porosity, permeabilities of ∼0.2 × 10−3 μm2, trial oil production rates of >5 m3/d, and, indeed, occur in subaqueous distributary channel microfacies. Type-II reservoirs ∼10% porosity, permeabilities of ∼0.1 × 10−3 μm2, and trial oil production rates of 1–5 m3/d. Type-III reservoirs have ∼5% porosity, permeabilities of ∼0.05 × 10−3 μm2, and trial oil production rates <1 m3/d. These results provide an important basis for predicting the distribution of exploitable zones in the Chang 8 sandstone and other adjacent tight sandstones.

Evolution characteristic and mechanism of microstructure, hydraulic and mechanical behaviors of sandstone treated by acid-rock reaction: Application of in-situ leaching of uranium deposits

The main difficulty in understanding the effects of chemical-physical composite stimulation for low-permeability sandstone-type uranium deposits is clarifying the influence of acidification on pore response mechanism and permeability-mechanical properties evolution during loading-deformation-failure process. Therefore, the acid-rock reaction experiment was first performed, the multiple testing methods (X-ray Diffraction, thin-section identification, high-pressure mercury intrusion porosimetry, stress-seepage coupling experiment) were then conducted, the evolution laws and mechanisms of reservoir physical characteristics after acidification were finally clarified. Results show that after the acid-rock reaction, the contents of calcite, feldspar and kaolinite of samples are decreased and the quartz content is increased, the permeabilities of samples are all promoted, the peak strength, elastic modulus, and shear modulus of samples are reduced and the Poisson’s ratio is raised. The acid-rock reaction changes the energy storage performance and promotes the plasticization of samples. It is suggested to adopt a lower sulfuric acid concentration (2 g/L) and longer reaction time (>45 d) for the ISL of uranium deposits. This work has important theoretical and practical significance for an in-depth understanding of the enhanced mining of low-permeability sandstone-type uranium deposits.

Mineral composition, pore structure and mechanical properties of coal measure strata rocks: A case study of Pingdingshan Coalfield

The microstructure and mechanical properties of coal measure rocks (CMR) are critical factors in the successful geological storage of CO2. While previous research has predominantly focused on coal seams, the overlying and underlying bedrock strata are equally significant yet often overlooked. This study addresses this gap by selecting coal and adjacent strata from the Twelve Mine as representative samples. A comprehensive suite of analyses was conducted, including thin section identification, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), uniaxial compression, and acoustic emission tests. These analyses were used to determine the mineralogical composition and pore structure characteristics of the CMR, elucidate the mechanical failure mechanisms of different CMR types, and explore the relationships between rock strength, mineral composition, and pore characteristics. The findings indicate that the primary minerals in coal are clay minerals, while mudstone is composed predominantly of clay minerals and quartz, sandstone is rich in quartz and feldspar, and limestone contains significant amounts of calcite. The porosity of CMR varies between 1.73 % and 10.12 %, with 82.72 % of the pores being micro- to mesopores and the remaining 17.28 % being macropores. The pore structures exhibit fractal characteristics, with the fractal dimension of mesopores ranging from 2.581 to 2.902, and that of macropores from 2.968 to 2.997. Coal predominantly fails through a combination of tensile and shear failure mechanisms, mudstone and limestone through tensile failure, and sandstone through shear failure. Furthermore, the results suggest that rock strength is positively correlated with quartz content and negatively correlated with kaolinite content and porosity. In terms of their influence on coal rock strength, the factors in descending order of impact are kaolinite, quartz, calcite, microporosity, macroporosity, dolomite, and mesoporosity. Thus, while the mechanical properties of these rocks are primarily governed by their mineralogical composition, the pore structure also plays a significant role.

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).

Enhanced erosion and silicate weathering of the West African craton during the late Cretaceous cooling evidenced by mineralogical and Hf[sbnd]Nd isotope proxies

The evolution of oceanic temperatures between the Turonian and the K/T boundary indicates a long-term cooling coincident with a decrease of atmospheric CO2 levels, yet the cause of climate cooling at that time still remains debated. In this study, we evaluated the possible implication of enhanced silicate weathering as a sink for atmospheric CO2 by applying paired NdHf isotope measurements to detrital clay records from the West African margin. The use of this novel proxy for chemical weathering intensity (ΔɛHf(t)clay) was complemented by additional mineralogical and major-trace element analyses in order to investigate the variability of mechanical erosion patterns and further explore potential linkages between tectonics, weathering and climate during the late Cretaceous.Our ΔɛHf(t)clay data suggest more intense silicate weathering on the West African Craton during the Santonian to the middle Campanian period, coincident with enhanced physical erosional inputs as inferred from higher Quartz/Clays and Feldspar/Clays ratios. This observation suggests that the shift towards intensified chemical weathering at that time was driven by enhanced mechanical erosion, possibly related to a moderate tectonic event on the West African craton. Evidence for increasing kaolinite contents and higher ΔɛHf(t)clay values during the Maastrichtian point towards more hydrolysing conditions, inducing either destabilization of older Mesozoic lateritic material or favouring the development of kaolinite-rich soils.Overall, this study was compared with several new data of chemical weathering evolution along the south Atlantic margins, adding new insights on tectonic-weathering-climate interactions during the late Cretaceous, suggesting a possible link between silicate weathering feedbacks and global cooling at that time.

On the hydration of limestone calcined kaolinitic clay cement and energy-efficient production

Understanding hydration kinetics of cement composite incorporating calcined clay is crucial in further progressing low-carbon binder designs. However, due to diversity of clays and complex synergy with further limestone addition, it is challenging to predict the hydration process. In this study, a coupled kinetic-thermodynamic model is developed based on unified functional form to generate comprehensive hydration studies on cement binders including calcined kaolinitic clay and limestone. Dedicated model parameterisation analyses are performed, following available rapid, relevant, and reliable (R3) tests, to determine the kinetic models. Moreover, a numerical framework is proposed to describe the synergy in hydration of limestone calcined clay cement (LC3) utilising clays of diverse kaolinite contents. The model is demonstrated to be capable of generating robust hydration assessments on both binary and ternary systems. In enhancing the overall sustainability, the proposed hydration model is leveraged to gauge the energy-efficient production of LC3 binders utilising local resources.

Cotransport of Thallium(I) and kaolinite colloids in quartz sand media containing sodium humate: Ionic strength, pH and kaolinite colloid concentration

In real soil environments, humus, colloids and other components significantly affect pollutant migration behavior. Investigating Tl(I) and kaolinite colloids’ cotransport in quartz sand media containing sodium humate (HA-Na) is vital for comprehending Tl(I) migration underground. This study examined the migration of Tl(I) and kaolinite colloids across varying pH levels (5, 7), ionic strengths (ISs) (1, 5, 50 mmol/L), and kaolinite colloid concentrations. Results indicate that lower IS and pH promote Tl(I) migration when transported alone. In cotransport system, kaolinite promotes Tl(I) migration under acidic conditions but inhibits it under neutral conditions, except at high kaolinite concentrations, where the effect shifts from inhibition to promotion. This is primarily due to changes in the zeta potential of quartz sand, HA-Na, and kaolinite, as well as Tl(I) adsorption after HA-Na and kaolinite occupy binding sites. Competitive adsorption between cations and Tl(I) also plays a significant role. Conversely, in individual system, higher IS and pH inhibit kaolinite migration, while increased kaolinite concentration promotes it. In cotransport system, Tl(I) promotes kaolinite migration under acidic conditions but inhibits it under neutral conditions, except at low kaolinite concentrations. This relates to changes in the zeta potential between kaolinite and the medium, as well as the retention of HA-Na in the column and its adsorption onto kaolinite. Competitive adsorption and binding site saturation also have an impact. This study enhances understanding of Tl(I) migration by revealing the dual effect of kaolinite colloids under different environmental conditions, contributing to better knowledge of Tl(I) fate and transport in natural environments.

Reservoir Characteristics of Marine–Continental Transitional Taiyuan Formation Shale and Its Influence on Methane Adsorption Capacity: A Case Study in Southern North China Basin

To further study the reservoir characteristics and adsorption capacity of the Taiyuan Formation shale in the South North China Basin (SNCB), the pore structure and adsorption capacity of shale are discussed using various analysis tests, including elemental geochemistry, organic geochemistry, mineral composition, low-temperature nitrogen adsorption (LTNA), and methane adsorption experiments. The results indicate that the Taiyuan Formation shale formed in a poor oxygen and anaerobic sedimentary environment in still water. The average value of total organic carbon (TOC) content is 2.37%. The organic matter type mainly consists of type III kerogen. The vitinite reflectance (Ro) ranges from 3.11% to 3.50%. The clay mineral content varies greatly, averaging at 40.7%, while the quartz content averages at 37.7%. The Taiyuan Formation shale mainly develops interparticle (InterP) pores, followed by organic pores, intraparticle (IntraP) pores, solution pores, and microfractures. BET specific surface area (SSA) is between 9.47 m2/g and 22.14 m2/g, while pore volume (PV) ranges from 0.0098 cm3/g to 0.022 cm3/g, indicating favorable conditions for shale gas storage. According to the results of the CH4 adsorption experiment, Langmuir volume from Taiyuan Formation shales exhibits 1.35~4.30 cm3/g, indicating excellent adsorption capacity. TOC content shows a positive correlation with both Langmuir volume and BET SSA from Taiyuan Formation shales, suggesting that TOC plays a crucial role in controlling microscopic pores and gas adsorption capacity. Organic matter enhances the shale adsorption capacity by providing abundant pore SSA. Due to formation compaction, the pore size of clay minerals decreases, leading to an increase in pore SSA, while kaolinite exhibits weak hydrophilic ability. Consequently, with the increase in clay minerals and kaolinite content, the shale adsorption capacity is enhanced to a certain extent. However, an increase in the carbonate mineral content may result in a decrease in the proportion of clay minerals, therefore reducing the CH4 adsorption capacity of shale.

Performance of cementitious systems containing calcined clay in a chloride-rich environment: a review by TC-282 CCL

In this review by TC- 282 CCL, a comprehensive examination of various facets of chloride ingress in calcined clay-based concrete in aggressive chloride-rich environments is presented due to its significance in making reinforced concrete structures susceptible to chloride-induced corrosion damages. The review presents a summary of available literature focusing on materials characteristics influencing the chloride resistance of calcined clay-based concrete, such as different clay purity, kaolinite content and other clay minerals, underscoring the significance of pore refinement, pore solution composition, and chloride binding mechanisms. Further, the studies dealing with the performance at the concrete scale, with a particular emphasis on transport properties, curing methods, and mix design, are highlighted. Benchmarking calcined clay mixes with fly ash or slag-based concrete mixes that are widely used in aggressive chloride conditions instead of OPC is recommended. Such comparison could extend the usage of calcined clay as a performance-enhancing mineral admixture in the form of calcined clay or LC2 (limestone-calcined clay). The chloride diffusion coefficient in calcined clay concrete is reported to be significantly lower (about 5–10 times in most literature available so far) compared to OPC, and even lower compared to fly ash and slag-based concrete at early curing ages reported across recent literature made with different types of cements and concrete mixes. Limited studies dealing with reinforcement corrosion point out that calcined clay delays corrosion initiation and reduces corrosion rates despite the reduction in critical chloride threshold. Most of these results on corrosion performance are mainly from laboratory studies and warrant field evaluation in future. Finally, two case studies demonstrating the application of calcined clay-based concrete in real-world marine exposure conditions are discussed to showcase the promising potential of employing low-purity calcined clay-based concrete for reducing carbon footprint and improving durability performance in chloride exposure.

Mapping global distributions of clay-size minerals via soil properties and machine learning techniques

Clay-size mineral is a vital ingredient of soil that influences various environment behaviors. It is crucial to establish a global distribution map of clay-size minerals to improve the recognition of environment variations. However, there is a huge gap of lacking some mineral contents in poorly accessible remote areas. In this work, machine learning (ML) approaches were conducted to predict the mineral contents and analyze their global abundance changes through the relationship between soil properties and mineral distributions. The average content of kaolinite, illite, smectite, vermiculite, chlorite, and feldspar were predicated to be 28.69 %, 22.30 %, 12.42 %, 5.43 %, 5.03 %, and 1.44 % respectively. Model interpretation showed that topsoil bulk density and drainage class were the most significant factors for predicting all six minerals. It could be seen from the feature importance analysis that bulk density notably reflected the distribution of 2:1 layered minerals more than that of 1:1 mineral. High drainage favored secondary minerals development, while low drainage was more benefited for primary minerals. Moreover, the content variation of different minerals aligned with the distribution of corresponding soil properties, which affirmed the accuracy of established models. This study proposed a new approach to predict mineral contents through soil properties, which filled a necessary step of understanding the geochemical cycles of soil-related processes.

Experiment and simulation assessment of supercritical underground coal gasification in deep coal seam

To explain the impact of geological and process factors on underground coal gasification in deep coal seam (>2200 m) and promote the efficient and clean extraction and conversion of coal, this study employs the orthogonal experimental design method to investigate the impact of CO2 coefficient (0–1), moisture content (30–80 wt%), calcite content (0–10 wt%), albite content (0–10 wt%), kaolinite content (0–20 wt%), reaction temperature (550–650 °C), and reaction pressure (23–27 MPa) on the characteristics of coal underground gasification under supercritical H2O/CO2 conditions. Furthermore, range analysis and variance analysis are utilized to determine the degree of influence of each factor and the interaction between factors. Finally, the Gibbs free energy minimization method is used to conduct a thermodynamic equilibrium analysis of coal supercritical H2O/CO2 gasification at high temperatures (750–1000 °C). The results indicate that the three most significant factors affecting the process of coal supercritical H2O/CO2 gasification are the CO2 coefficient, moisture content, and reaction temperature. The maximum carbon gasification efficiency at 650 °C in experimental cases and 1000 °C in simulation cases is 22.2% and 88.1%, respectively. Although the addition of CO2 at lower temperatures reduces the carbon gasification efficiency, at high temperatures (>900 °C), a higher initial CO2 concentration increases the carbon gasification efficiency. The addition of CO2 under conditions of low moisture content increases the mole fraction of H2, but reduces it under conditions of high moisture content (≥70 wt%). Among the three minerals, calcite has the most significant influence on the gasification process.