Red Clay Research Articles

Enhancement Mechanism of the Mechanical and Shrinkage Properties of Red Clay Solidified Using the Consolid System

Enhancement Mechanism of the Mechanical and Shrinkage Properties of Red Clay Solidified Using the Consolid System

Heritage clay brick characterization and assessment with compatible contemporary bricks for retrofitting of heritage monuments

Various mughal architecture clay brick masonry monuments were built in the Punjab state of northern India from the late 14th to late 19th centuries. Nanakshahi monuments (era of 1st Sikh Guru-Guru Nanak Dev Ji) are gigantic clay brick masonry structures constructed of lime and lime surkhi mortar (a powdered form of red burnt clay brick). Currently, this study is focused on identifying a suitable material for repairing and strengthening heritage clay brick monuments. Using the mineralogical composition of heritage Nanakshahi clay bricks (NSCB), the study compares them with contemporary clay bricks (CCB) from the same region, and then compares them to newly prepared clay bricks (NPCB), which have similar composition and dimensions to NSCB. The X-ray fluorescence confirms that the NSCB samples of southeast Punjab have an elemental composition consisting of filler SiO2 and binding elements like Al2O3, Fe2O3, CaO, K2O and MgO. The average density of ancient NSCB and CCB has been found to be similar; the ancient NSCB has a lower water absorption rate and porosity in contrast to the present-day clay bricks. The Initial rate of absorption of an ancient NSCB is quite higher. In comparison to the heritage NSCB, the CCB's compressive strength value is lower and uniaxial compression strength of newly prepared clay bricks (NPCB) of similar mineralogical composition and dimensions is comparable to that of the heritage NSCB from Punjab districts. The significance of the study is to suggest a compatible material for strengthening of heritage clay brick monuments of northern India.

Phase Evolution, Mechanical, and Electrical Properties of Lightweight Ceramic Prepared Using Scoria at Low Temperature

This study aimed to produce lightweight, eco-friendly ceramic materials with superior properties using natural raw materials and low processing temperatures. Five ceramic samples were fabricated using red clay and varying contents of volcanic scoria (10%, 20%, 30%, 40%, and 50%) through sintering at 950 °C for 4 h. The crystalline phases, electrical properties, porosity, and mechanical strength of all the ceramic specimens were comprehensively evaluated. It was determined that the chemical composition of the raw materials and the resulting phases significantly influenced these various attributes. The XRD analysis revealed that the ceramic samples primarily consisted of the crystalline phases gehlenite, low quartz, and anorthite, along with the minor wollastonite and hematite phases. As the scoria content was increased, the MgO and Fe2O3 concentrations also increased, leading to a reduction in dielectric constant, dielectric loss, and electric conductivity. Moreover, the porosity of samples decreases from S10 to S50 due to the increase in the percentage of scoria and this reduction in porosity led to increased bending strength. The findings of this study suggest that volcanic scoria can serve as a viable eco-friendly raw material to produce lightweight ceramics with excellent electrical and mechanical properties, presenting cost-effective and energy-efficient solutions for various applications.

Differences in Cytokine Expression at Baseline and in Response to Mineral Stimulation by Peripheral Blood Mononuclear Cells from Podoconiosis Cases and Healthy Control Individuals

Epidemiological, histological, and immunogenetic studies suggest that podoconiosis (a non-infectious tropical lymphoedema affecting approximately 4 million people globally) is an HLA class II-associated inflammatory condition that develops in response to an unknown trigger found in volcanic red clay soils. Silicate particles of the kaolinite and aluminum types have been identified in femoral lymph node biopsy samples from endemic area residents, suggesting a possible role in the pathogenesis of podoconiosis. We measured in vitro peripheral blood mononuclear cell cytokine responses (TNF-α, IL-1β, and IFN-γ) to stimulation with the minerals kaolinite, chlorite, and beryllium sulfate (all at 100 µM) using ELISA. Real time PCR was used to measure gene expression of signature cytokines in fresh whole blood, comparing podoconiosis patients and endemic healthy controls. Our results showed that the levels of TNF-α and IL-1β from in vitro cell cultures were significantly higher in unstimulated samples from patients compared to controls (p = 0.04 and p = 0.005, respectively). The minerals kaolinite and chlorite induced two and three-fold higher levels of IL-1β following 24 h of stimulation in healthy controls compared to patients, respectively. We did not find significant differences in mRNA expression of the cytokine genes assayed, though a slight fold increment in IL-1β and TGF-β was observed. In conclusion, our data suggest that the immune system is in a state of persistent activation in vivo in podoconiosis patients, and additional studies of immune regulation and exhaustion are needed to further characterize immune dysfunction in the pathogenesis of the disease. A better understanding of the underlying processes could lead to the development of a ‘biosignature’ detectable in the early reversible stages that could ultimately contribute to the elimination of this preventable, disabling, neglected tropical disease.

Study on microscopic pores and physico-mechanical properties of red clay modified by calcium carbonate

Red clay as a special soil has a high liquid-plastic limit, water swelling and water loss shrinkage. To solve the problems red clay was modified by calcium carbonate produced in Hezhou, Guangxi. The Liquid-plastic limit, water loss shrinkage, nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and consolidated drained (CD) triaxial shear test were carried out on the modified soils. The results show that when the calcium carbonate content is 20%, the plastic limit is 24.38 and the liquid limit is 38.67, which are reduced by 35.04% and 22.16%, respectively. The Montmorillonite content in the modified soil is reduced by 27.7%. The shrinkage coefficient decreased from 0.325 to 0.102. The NMR test shows that the content is 5% and 10% would lead to a decrease in the macropores and an increase in the micropores pores. The phenomenon is the opposite (15% and 20%). All contents led to the porosity increase. The calcium carbonate content of 5% was selected for triaxial shear tests to obtain the stress-strain curves. The Duncan-Zhang was used to predict the modified soil. The model has a large error in the prediction of the peak of the principal stress difference, but the overall trend is relatively consistent. Therefore, the correction coefficient related to the confining pressure was introduced. The corrected model fits the triaxial shear test well. The research provides a method for the liquid-plastic limits and shrinkage properties of modified red clay, explores the influence of calcium carbonate content on microscopic pores, and the correction of the model provides a theoretical basis for practical application.

DEM simulation of subsoiling in tropical sugarcane fields: Effects of opposing subsoiler design and model parameters

During the subsoiling operation of clayey soil in sugarcane fields in tropical areas, there are key limitations such as high resistance caused by high adhesion and unsatisfactory subsoiling effects of machines and tools. To address these issues, this study first explored the machine's structural characteristics using a mechanism analysis method to identify key optimization parameters. Then, simulation tests were conducted based on the root-soil complex model. Single factor analysis was conducted to evaluate the effects of backsweep angle, plow spacing, and penetration angle on tillage resistance and soil disturbance, determining their optimal ranges. Finally, a multi-factor orthogonal rotation combination experiment was designed using Box-Behnken theory to optimize the subsoiler's structural parameters. The regression analysis results show that the optimized model significantly improves the reliability of simulation results. Field verification test results show that under the conditions of a sweep angle of 50°, a plow spacing of 60 cm, and a soil penetration angle of 45°, the average tillage resistance of subsoiling operations is significantly reduced to 76.2 kN, and the amount of soil disturbance is reduced to 1780cm². The optimization reduced tillage resistance and soil disturbance by 34.42% and 30.50% respectively, significantly improving the subsoiling performance. To our knowledge, this is the first work applying discrete element methods to subsoiling operations in red clay soils in sugarcane growing areas. The proposed machine structure has higher efficiency and better performance, providing an effective reference for the design and application of sugarcane field subsoiling machinery.

Iron removal from red clay using oxalic acid leaching for enhanced ceramic industry applications

This work focused on removing iron with oxalic acid from red clay samples collected from Kapasia Upazila, Gazipur District, Bangladesh. To characterize the red clay, the study employed several techniques: particle size analysis, WDXRF (wavelength-dispersive X-ray fluorescence), AAS (atomic absorption spectroscopy), XRD (X-ray diffraction), TGA (thermogravimetric analysis), and FESEM (field emission scanning electron microscopy). Additionally, leaching experiments were conducted with varying concentrations of oxalic acid, temperatures and times. After leaching, the red clay composition changed significantly: SiO₂ increased from 53.6 % to 63.13 %, Fe₂O₃ decreased from 17.1 % to 3.64 %, Al₂O₃ remained relatively stable at 18 %–18.22 %, and other oxides showed minor variations. 78.71 % of the iron was removed at optimal leaching conditions (1.0 M oxalic acid, 100 °C, 150 min, and 250 rpm). Mineralogically, the red clay samples are composed of illite, kaolinite, quartz, feldspar, hematite and chlorite. Thermal analysis showed significant weight loss at temperatures between 300 and 600 °C. Ceramic trials were conducted at firing temperatures of 900 °C and 1100 °C to evaluate the mechanical properties of tiles. The results obtained showed significant improvements in red clay quality for ceramics. Being a low-cost and eco-friendly process, this becomes a very prominent alternative to conventional iron removal techniques and helps produce high-quality ceramic tiles, contributing towards economic growth in Bangladesh.

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.

Radiation shielding and spectroscopic features of replacement materials: Reusing of agricultural and industrial wastes

Environmental pollution increases due to the large amounts of waste production and raw material consumption depending on the increasing population. Agricultural and industrial wastes which are some of the sources of the pollution need to be reuse to reduce the negative impact on the environment and also contribute positive effect to the economy. In this context, industrial wastes such as clay types (red and green) and agricultural wastes such as egg shell, walnut shell and banana shell were used to prepare materials which can be used as replacement materials for construction industry. Radiation attenuation parameters (mass attenuation coefficients, effective atomic number, linear attenuation coefficients, mean free path, half-value layer, exposure and energy absorption build up factors, fast neutron removal cross-section) were acquired by Phy-X/PSD code. Spectroscopic techniques (XRD, EPR, SEM-EDS) were performed for the structural analysis. The existence of calcite main phase peaks (≈29.7) as well as SiO2 (≈20° and 26°) and cellulose phases (≈16° and 34.7°) were observed by XRD. Mn+2 sextet lines with five weak doublets attributed to the forbidden transition lines of Mn+2 and a singlet with a g value of ≈2.00 and linewidth of ≈10 G were recorded by EPR. Among the samples, it was found that K1 (Red clay (20%)-eggshell waste (60%)-Bayburt stone waste (20%)), K3 (Red clay (60%)-eggshell waste (20%)-Bayburt stone waste (20%)), C3 (Red clay (60%)-eggshell waste (20%)-walnut shell waste (20%)) and Z3 (Green clay (60%)-egg shell waste (20%)-Bayburt stone waste (20%)) have the highest shielding potentials. All samples examined with good protection performances can be used as substitute materials instead of cement or aggregate for the aim of reusing the wastes and supporting the environmental and economic benefits.

Study on the physical properties of red clay cured by different external admixtures combined with enzyme induced carbonate precipitation technology

Study on the physical properties of red clay cured by different external admixtures combined with enzyme induced carbonate precipitation technology

Role of iron-rich clays on sintering of porcelain stoneware tiles

Porcelain stoneware traditionally contains low Fe2O3 (<1 wt%), limiting research on iron's effects beyond coloration to date. However, recent changes in the supply chain induced a shift towards resource efficiency and circular economy, which led to body formulations with Fe2O3 up to 2.5 wt%. This study investigates the impact of iron-rich clays on the firing behaviour of porcelain stoneware, focusing on sintering processes, Fe speciation, and physical properties of the vitreous phase. Results show that red clays influence vitrification paths and maximum densification temperature, as well as composition and properties of the melt. This occurs not only because the relatively high iron percentage (up to 1.7 wt%), but for a set of factors, like the overall mineralogical and chemical composition of batches. Iron turns to be crucial for the stability of ceramic bodies at high temperatures, since Fe3+ can partially reduce to Fe2+, releasing gases and contributing to bloating phenomena.

Investigation of strain-softening behaviours and development of constitutive model of red clays in Guiyang, China

Red clay is widely used in engineering projects; it is characterized by high moisture content, high plasticity, large porosity, high strength and low compressibility. The engineering properties and deformation modelling of red clay in Guiyang differ significantly from those of ordinary soils. Consequently, it is essential to conduct a detailed study of the stress–strain relationship of red clay in order to obtain accurate engineering parameters. Hence, a series of unconsolidated undrained triaxial compression tests (UU) was conducted on red clay in Guiyang under different water contents and confining pressures. The test results show that the stress–strain curve of the clay undergoes three stages: elastic deformation, plastic yielding and stress reduction after failure. After reaching peak deviatoric stress, the deviatoric stress decreases gradually and stabilizes, showing noticeable strain-softening characteristics. The non-linear model from the Nanjing Hydraulic Research Institute (NHRI) was introduced for fitting and obtaining relevant parameters. Then, based on the FLAC 3D platform, numerical simulation was carried out on a standard soil sample. The research results show that the calculated curve from the non-linear model fits the experimental curve quite well, and the numerical test curve also agrees with it. This indicates that the non-linear model from NHRI can effectively reflect the strain-softening behaviour of clay and is highly applicable to Guiyang red clay.

Experimental investigation of fired clay bricks for gamma radiation shielding

In this study, the focus was on evaluating how the physical and structural attributes of red clay bricks influence their ability to shield γ-rays. The red clay brick samples' density (ρ, g/cm3) was measured using the MH-300A density meter. The minerals present in the selected clay were identified through the application of X-ray diffraction. Moreover, the material's morphology and chemical composition were studied using scanning electron microscopy. By increasing the pressure rate (PR) from 7.61 to 114.22 MPa, the density of the synthetic clay bricks was increased from 1.50 to 1.69 g/cm3. Subsequently, the gamma-ray shielding effectiveness of the clay bricks produced was investigated through experiments utilizing a NaI (Tl) detector with exposure to various gamma sources. The experimental data illustrated a rise in the linear attenuation coefficient (μ) of the proposed clay bricks, progressing from 1.352 ± 0.040 to 1.559 ± 0.068 cm−1, from 0.111 ± 0.003 to 0.123 ± 0.005 cm−1 and from 0.087 ± 0.002 to 0.099 ± 0.003 cm−1 at γ-ray energies of 0.033, 0.662, and 1.332 MeV, respectively. The rise in μ resulted in a reduction in the half-value thickness (Δ0.5), lead equivalent thickness (Δeq) and transmission factor (TF), in the synthetic bricks. Additionally, samples with increased thickness exhibited enhanced effectiveness in shielding gamma radiation, making them suitable for various applications requiring radiation protection. Moreover, the detection of pressure rate's influence on the physical and shielding characteristics of clay bricks was observed at specific gamma energies. (0.033, 0.662 and 1.332 MeV).

Experimental Study on the Mechanical Properties of Rammed Red Clay Reinforced with Straw Fibers

Experimental Study on the Mechanical Properties of Rammed Red Clay Reinforced with Straw Fibers

Strength characteristics of phosphogypsum stabilized soil under dry and wet cycles

In order to study the strength characteristics of red clay stabilized by a high dosage of phosphogypsum, a mix proportion design was carried out at the ratio of phosphogypsum:red clay = 1:0.5, 1:1, 1:2, 1:3, 1:4, and 1:5 using 4%, 6%, and 8% cement as a curing agent, and this study was carried out through the unconfined compressive strength test, water stability test, California bearing ratio (CBR) test, and durability test. As the phosphogypsum content increases, the unconfined compressive strength of the mix shows a trend of increasing and then decreasing, the unconfined compressive strength of the mixture is the largest when the ratio is 1:3, and with the increase in the number of dry and wet cycles, the unconfined compressive strength of the mixture decreases, and the decay is the largest at 2–3 dry and wet cycles. The higher the phosphogypsum content, the better the water stability performance of the mix. In addition, the CBR value of the mixture can meet the requirements of freeway, primary highway, secondary highway bed, and embankment filler bearing ratio. In this paper, a mix durability test method is proposed to express the mix durability performance in terms of mass loss rate and durability coefficient; the mass loss rate of the mix increases with the increase in the number of wet and dry cycles, and the durability coefficient decreases with the increase in the number of wet and dry cycles; the higher the content of phosphogypsum, the better the durability performance of the mix.

Disintegration behaviors of red clay under wet-dry cycles

Cyclic wetting-drying alternation has a significant influence on the strength and structure of soils. It is prone to causing soil softening and disintegration, highlighting the importance to improve the soil's resistance to disintegration. This paper utilizes a self-developed disintegration test apparatus to analyze the disintegration characteristics of improved red soil under wet-dry cycles, focusing on the disintegration amount and ratio. Furthermore, XRD (X-ray diffraction), SEM (scanning electron microscope), tensile test, and contact angle test are employed to investigate the anti-disintegration behaviors of the improved red soil. The results show that the disintegrating amount and ratio of undisturbed and improved red soil are distinctly different under wet-dry cycles. Linear, stepped, constant and concave but perfect "S" shapes of the disintegrating ratio are observed in the cyclic tests. Cement and lime strengthen the red soil primarily through hydration reaction. The drop experiment confirms that cement plays a crucial role in restraining the disintegration. When the ameliorant content is low, the correlation between pore parameters and disintegration duration of red soil follows the order: mean shape coefficient > fractal dimension > probability entropy > area probability distribution index. With a high ameliorant content, the correlation remains similar, with slightly higher correlation for probability entropy. Under wet-dry cycle conditions, sludge and kaolin can improve the soil through the bonding of clay particles. The improved water repellency greatly enhances the resistance to disintegration of the altered red soil. The research provides valuable insights for the practical application of soil.

Effect of Pb(II) on hydraulic behavior and microstructure evolution of activated charcoal-bentonite-reticulated red clay barrier

Effect of Pb(II) on hydraulic behavior and microstructure evolution of activated charcoal-bentonite-reticulated red clay barrier

Metagenomic and isotopic insights into carbon fixation by autotrophic microorganisms in a petroleum hydrocarbon impacted red clay aquifer

Autotrophic microorganisms, the pivotal carbon fixers, exhibit a broad distribution across diverse environments, playing critical roles in the process of carbon sequestration. However, insights into their distribution characteristics in aquifers, particularly in those petroleum-hydrocarbon-contaminated (PHC) aquifers that were known for rich in heterotrophs, have been limited. In the study, groundwater samples were collected from red clay aquifers in the storage tank leakage area of a PHC site, a prevalent aquifer type in southern China and other regions. Metagenomics combined with hydrochemical and inorganic carbon isotope analyses were employed to elucidate the presence of microbial carbon fixation and its driving forces. Results showed that there were hundreds of autotrophic microorganisms participating in distinct carbon fixation processes in the red clay PHC aquifers. Reductive tricarboxylic acid (rTCA) and dicarboxylate/4-hydroxybutyrate (DC/4HB), as well as 3-hydroxypropionate (3HP or/and 3-hydroxypropionate/4-hydroxybutyrate (3HP/4HB)) were the predominant carbon fixation pathways. The abundances of carbon fixation genes and autotrophic microorganisms were significantly and positively correlated with hydrocarbon concentrations and δ13C of dissolved inorganic carbon (δ13C-DIC) values. This finding indicated that the petroleum hydrocarbon significantly promoted the proliferation of carbon fixation microorganisms, leading to a substantial uptake of inorganic carbon. Therefore, we deduce that this process holds considerable potential for carbon sequestration in PHC-contaminated aquifers.

Early-age structural build-up and rheological assessment of alkali-activated slag-red clay brick waste pastes: Influence of silica modulus and precursors proportions

Sustainability plays a crucial role in the current context of the cement industry, and alkali-activated materials (AAMs) are emerging as eco-efficient alternative binders. On the other hand, the massive generation of red brick waste worldwide and its lack of a defined destination emphasizes this material as an alternative precursor that has been insufficiently explored in the literature. Based on this context, the present study aims to investigate the structural build-up, reaction kinetics, and rheological properties of alkali-activated pastes based on blast furnace slag (BFS) and red clay brick waste (RBCW). Fresh properties such as structural build-up, rheology, and reaction kinetics are lacking in the literature on RCBW-based AAMs, highlighting these properties as a research gap to be filled and discussed in depth in this paper. The flow sweep test was performed, linked to yield stress and viscosity properties. The structural build-up was evaluated by strain sweep and small amplitude oscillatory shear (SAOS) tests based on viscoelastic parameters: storage modulus, loss modulus, and phase angle. Isothermal calorimetry and in-situ FTIR were also conducted to complement the analysis and provide insight into the reaction kinetics, chemical structure, and product formation. Higher silica modulus (Ms) resulted in a lower structural build-up rate and a delayed reaction. Higher content of RCBW resulted in a delayed structuration process, which was linked to a delay in the precipitation of aluminosilicate gels. Early increase in the structural build-up in 25 % and 50 % RCBW blends (Ms = 1.0) is associated with the early formation of a well-percolated network.

Research on the expansion, shrinkage properties and fracture evolution of red clay stabilised with phosphogypsum under dry-wet cycles.

In view of the special engineering properties of red clay and the waste of phosphogypsum resources, the expansion and contraction deformation and fissure evolution of phosphogypsum stabilized red clay under different conditions were investigated by laboratory tests and image processing system. The research results show that: (1) the absolute expansion and absolute shrinkage of phosphogypsum stabilized red clay are positively correlated with the compaction degree, the number of dry and wet cycles and the cement dosage, and negatively correlated with the initial water content and the phosphogypsum dosage; (2) the fissure rate increases with the increase of the number of dry and wet cycles, and decreases with the increase of the initial water content, the compaction degree, the cement, and the phosphogypsum dosage; (3) The relationship among absolute expansion rate (absolute shrinkage), degree of compaction and fracture rate can be fitted by the equation f(x,y) = ax+by+cx2+dy2+e; (4) Phosphogypsum has an obvious inhibiting effect on the expansion, shrinkage and cracking of the mix. It is recommended that the cement mixing amount of 6% and phosphogypsum: red clay = 1:1~1:2 as roadbed filler.