Clay Type Research Articles

Application of LIBS and LA-ICP-MS analysis to Hellenistic tableware

Greek and Hellenistic painted vases have attracted scholars of classical archaeology for centuries, either because of the artistic value of the painted decorations or because of the depicted scenes of ancient everyday life. Due to the application of thin slips on the surface, different methods are used for the chemical characterisation of the slips and the body of the same vase. The slips are commonly analysed by X-ray microanalysis, offering point-by-point analysis of mostly major elements, while different tools, such as X-ray fluorescence (XRF), inductively coupled mass spectrometry (ICP-MS), and instrumental neutron activation analysis (INAA), are used for bulk body analysis. This can cause difficulties in comparing the bulk composition and thus in determining the similarities and differences in the preparation process of the clay paste for the slips and bodies of an object. Given the artistic value of these objects, museum curators tend to be reluctant to provide samples for invasive characterisation. Micro-destructive laser ablation methods offer a robust solution to addressing both the relationships between ceramic body and surface treatment chemistry and destructive sampling. To provide a proof-of concept, we analysed slips and bodies of a small sample of Hellenistic fine wares from the Greek colony of Issa in modern Croatia with Laser-Induced Breakdown Spectroscopy (LIBS) and Laser ablation-ICP-MS. Results show remarkable diversity in the use of clay types and processing techniques.

Valorization of Different Clays Used in the Treatment of Oily Wastewater in the Development of Construction Products

AbstractThe aim of this research is to study the feasibility of using clays used in the decontamination of wastewater containing olive oil wastewater (OOW), new lubricating oil (NOW) or motor oil (MOW) in the manufacture of ceramic bricks. Three types of clays were used for filtration, kaolinite type clay (KT), smectite type clay (CT) both from Tunisia and illitic chloritic clay (CS) from Jaén (Spain). These clays containing different types of oils, as well as the control clays, were used in the manufacture of bricks fired at 900 °C. These bricks were characterized by physical, mechanical and thermal tests. The sintered microstructure’s evolution was followed by tracked through scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The results indicate that the specific type of clay used influences the technological characteristics of the bricks. The use of CT clay gives rise to increase bulk density, greater compressive strength, and reduced apparent porosity and water absorption. The use of clays used in the decontamination of water containing oils produced a decrease in bulk density, compressive strength and thermal conductivity and leads to an increase in apparent porosity and water absorption in the order OOW > NOW > MOW according to the total organic carbon content (TOC). Therefore, the use of clays used in the filtration of water that contain different oils can represent a promising way of valorizing this waste, which can alleviate the environmental impact and represents economic savings for the industry of construction materials with properties of thermal insulation, getting closer to a circular economy.

Clay mineral mediated dynamics of CO2 hydrate formation and dissociation: Experimental insights for carbon sequestration

Marine sediment-based CO2 sequestration through hydrate formation is a promising approach for long-term CO2 storage. Despite the prevalence of clay minerals in marine sediments, their impact on CO2 hydrate dynamics remains disputed and necessitates validation. This study systematically investigated the effect of clay minerals, specifically Ca-montmorillonite (Ca-mmt) and illite, on CO2 hydrates nucleation, growth, and dissociation in clay suspensions (0–10 wt% concentrations). Clay minerals significantly promoted CO2 hydrate nucleation by providng additional nucleation sites and influencing water distribution through the surface electric field. Ca-mmt exhibited a more pronounced nucleation effect due to stronger hydration ability of Ca2+ increasing nucleation sites and local CO2 concentration. Both clay minerals enhanced CO2 hydrate growth, with concentration-dependent effects that differ between clay types. Ca-mmt exhibited a higher growth rate at lower concentrations (≤1 wt%), but a lower rate at higher concentrations (>1 wt%) due to the stronger swelling and aggregation ability upon water contact. Morphological analysis revealed the clay minerals’ impact on fluid behavior and mass transfer during hydrate growth. During dissociation, clay minerals impeded the process, prolonging overall dynamics. This study highlights the impact of physicochemical disparities between Ca-mmt and illite on CO2 hydrate dynamics, underscoring the importance of these interactions for CO2 sequestration.

Layered Double Hydroxide: An Economical and Dynamic Choice for Water Remediation with Multiple Functionality

AbstractIn terms of environmental pollution, water pollution is the most significant problem facing living organisms worldwide. Pollutants of various types, including toxic, inorganic, and organic materials, have a detrimental impact on terrestrial and aquatic ecosystems. Materials with layers, such as layered double hydroxides (LDHs), a type of synthetic anion clay, have a wide range of potential applications. In this comprehensive study, we have discussed variety of LDHs, and their explicit properties which have significant advantages for the removal of a variety of pollutants from water. Besides these, LDHs are easily synthesized with high yield and, tuneable structure based on choice of metals, etc. Based on these unique potentials, we have summarized how layered double hydroxides and their hybrids are synthesized efficiently. The performance and applications in removing water pollutants involving heavy metals, inorganic anions, and organics at different parameters such as temperature, adsorbent dosage, pH, and contact time are discussed. Consolidated information has been provided regarding the LDH synthesis, conditions for adsorption, and reference of the particular work. The worked‐up LDH's regeneration potential and methods evolved for regenerating it, different kinetic models and isotherms are also discussed.

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.

Quantitative elemental analysis and petrographic investigation of ancient potteries from archaeological sites of Tamil Nadu, using total reflection X-ray fluorescence spectroscopy

In order to investigate the elemental composition, a total of 19 potteries and two representative clay samples from Senjikothamangalam (Villupuram district) and 12 potteries and one representative clay sample from the Palayanur (Chengalpattu) archaeological sites in Tamil Nadu were analyzed using total reflection X-ray fluorescence spectroscopy. The presence of elements such as Fe, Ca, K, Ti, Al, Sr, Mn, P, V, Cr, Zn, Rb, Ni, Cu, Pb, Ga, Y, Bi, Br, and As were identified in the pottery and clay samples. Statistical analysis, such as Pearson correlation, cluster and principal component analysis were used to categorize the samples based on their elemental composition. The outcome of the Pearson correlation and cluster analysis corroborated that the Senjikothamangalam pottery samples (P-1 to P-19) were made using the same type of clay, except P-10. Similarly, all Palayanur pottery samples (P-20 to P-31) were manufactured from the same clay. The petrographic analysis of the potteries revealed further information about its provenance and making methods.

Antibacterial and therapeutic potential of historic deposits of silesian healing clay – terra sigillataSilesiaca

Ethnopharmacological relevanceThe increasing evolution of pathogen resistance is a global problem that requires novel solutions. Recently, an increased interest in ethnomedicinal sources can be observed in the derivation of new medicines. The return to traditional medicinal formulations handed down for generations is being followed, but it is necessary to revise them again, taking into account the generally accepted research protocol. Aim of the studyWe aimed to evaluate the antimicrobial potential of historical deposits of Silesian healing clay (SHC), used in ethnomedicine against Gram-positive bacteria and to assess their biological activity using a primary dermal fibroblast line (NHDF) and a model monocyte line (THP1). Materials and methodsInformation on medicinal clay deposits that occur in Silesia and are traditionally used in ethnomedicine or ancient medicine and known as terra sigillata Silesiaca or SHC, was selected on available source materials and old prints and maps from the archives of the Polish Geological Institute (Wrocław, Poland). Subsequently, their places of occurrence were identified and traced in the field by taking three deposits from the Silesia territory: Upper Silesia (D1), Opole Silesia (D2), and Lower Silesian (D3) Voivodeships for analysis. Their basic parameters and antimicrobial efficacy against pathogenic bacteria, Gram-positive streptococci and staphylococci, including methicillin-resistant strains, were examined. The study evaluated the effects of clays on growth and vitality using a primary dermal fibroblast line (NHDF) and a monocytic line (THP1). Studies were performed on a cell culture model to determine the effects on tissue regeneration (fibroblasts) and anti-inflammatory effects (monocytes). The study attempted to identify the mechanism of antimicrobial action, especially the textural characteristics and geochemical composition, as well as the environmental reaction (pH). ResultsSHCs were classified into the following textural classes: clay loam (D1), clay (D2), and sand (D3). The tested deposits have antimicrobial properties that reduce the bacterial population (104 CFU) compared to the control (108 CFU). The antimicrobial effect depends on the type of clay and the species or strain of bacteria used. In-house studies clearly showed that Staphylococcus aureus Pcm 2054 and Staphylococcus epidermidis MRSE ATCC 2538 cells were completely adsorbed by clay minerals from clay D3.13. Furthermore, 10% leachates also showed an antimicrobial effect, as a reduction in bacterial populations was observed ranging from 91 to 100%. The results showed stimulation of fibroblast culture proliferation and inhibition of the growth of inflammatory cells (monocytes). ConclusionSHCs tested have antimicrobial potential, in particular D2.7, D2.11, and D3.13. The D3.13 deposit had a bactericidal effect against the staphylococci tested. Aqueous solutions of clays also showed bacteriostatic effect. The results obtained in cell culture model tests indicate properties that modulate the healing process – stimulation of fibroblast growth (NHDF line) and inhibition of monocyte growth (THP1 line).

Boron toxicity in plants: understanding mechanisms and developing coping strategies; a review.

Boron is essential for plants, but excess can induce toxicity. Boron (B) is a vital micronutrient for plants, but excess B can induce toxicity symptoms and reduce crop yields. B bioavailability depends on soil properties, including clay type, pH, and organic matter content. Symptoms of B toxicity include reduced shoot and root growth, leaf chlorosis and necrosis, impaired photosynthesis, and disrupted pollen development. This review paper examines the current knowledge on B toxicity mechanisms, tolerance strategies, and management approaches in plants. This review covers (1) factors affecting B bioavailability; (2) toxicity symptoms in plants; (3) uptake, transport, and detoxification mechanisms; and (4) strategies. To mitigate toxicity, plants reduce B uptake, activate efflux transporters, compartmentalize B, and enhance antioxidant systems. On the basis of this review, future research should focus on identifying novel tolerance mechanisms, exploring genetic strategies for improved B management, and developing innovative agronomic interventions. These insights will facilitate the breeding and management of crops for enhanced productivity under B toxicity stress.

Comparative Chemical Study of Three Different Market Samples of an Important Clay Mineral Drug “Gil-E-Makhtum” with A Brief Ancient Description of Earth's Natural Resources

The medical use of earth's natural resources or mineral drugs is probably as old as the history of man kinds and has been used widely for the ailments of many diseases despite knowing the presence of chemical constituents or pharmacological activities of that particular substance but in the present era, with the modern techniques much more research work has been done to know the active components and their pharmacological properties which could have now been used in the modern medicine. Among the various earth natural resources or mineral drugs Gil-e-Makhtum (Sealed earth or the type of clay) also known by the name Lemnian earth, is a medicine in the shape of a stamped clay tablet (Sphragis) from Lemons, northeastern Greece, was much valued in antiquity and is utilized as such as well as an ingredient in the number of compound formulations in the Unani system of medicine for the treatment of various diseases. In this paper with the description of the brief history of Earth’s Natural Resources, the comparative chemical study of three different market samples of Gil-e-Makhtum was carried out by following some parameters of qualitative analysis and quantitative estimations. The analysis included Loss of weight on drying at 105oC, solubility in 1 normal hydrochloric acid and water, total ash, acid insoluble ash, bulk density, and tapped density. Besides, some major estimations e. g. Hematite (Fe2O3), Alum (Al2O3), Quartz (SiO2), and Calcium oxide (CaO) were also carried out.

Effects of clay type and component fineness on the hydration and properties of limestone calcined clay cement

Effects of clay type and component fineness on the hydration and properties of limestone calcined clay cement

Use of a Glaciogene Marine Clay (Ilulissat, Greenland) in a Pilot Production of Red Bricks.

Uplifted occurrences of fine-grained glaciogene marine sediments are found throughout the northern hemisphere. These sediments could be used to produce local construction materials, to rely less on imported construction materials from southern regions. In this study, a representative occurrence from Ilulissat, West Greenland, was investigated as a potential resource for local brick production. The study comprised three parts: (1) raw material characterization based on grain size distribution, major element chemistry, including total carbon, sulfur, and chloride concentrations, mineralogy, morphology, and Atterberg limits; (2) the production of test bricks at a Danish brickwork; and (3) testing of the bricks based on total shrinkage, water absorption, hygroscopic adsorption, open porosity, bulk density, compression strength, and mineralogy. The bricks produced proved to have excellent compression strength, low open porosity, and low water absorption. The shrinkage could be reduced by adding 10% chamotte to the marine sediment. Based on the investigated properties, this indicates that this type of clay is highly suitable as a resource for bricks.

A new method for CBR prediction using fuzzy set theory

California Bearing Ratio (CBR) values of the subgrade soils are key parameters in highway route survey and project design. However, in order to calculate the CBR value, time-consuming and specialized tests must be performed in the laboratory or in the field. In this study, a model based on Fuzzy set theory is proposed to predict the CBR value of soils. The geological characteristics of the fine-sized aggregate in soils are considered as the key parameter in the prediction model.For this purpose, novel Fuzzy membership functions are defined. Logarithmic interpolation approach, which takes into account the Atterberg limits and Proctor parameters of the soils, was used to determine the membership degrees of the gravel and sand sized aggregates forming the soil. The membership degrees of fine-sized aggregates were determined by basic sigmoid membership function according to the type of clay they contain. In order to verify the accuracy of the model, the calculated results were compared with the soaked CBR values obtained from laboratory tests and it was found that there was a high correlation (R2=0.86) between each other. Considering the obtained results together, it was determined that the effect of variables such as the geological class to which the aggregates forming the soil belong, which have the potential to affect the CBR value of the soils, on the results of the CBR prediction models can be eliminated by means of membership functions.

The Effect of Adding the Mishraq Sulfur Ore on the Physical and Chemical Properties of Al-Angor and Al-Nahrawan Clays to Producing Lightweight Bricks

This paper aims to examine the possibility of producing lightweight laboratory clay Bricks by adding sulfur ore powder in different weight ratios ranging from 0, 10, 20, 30, 40, to 50% as supplementary materials to two types of clays taken from two different sites, which is the Al-Angor clay region near the city of Ramadi and the Al-Nahrawan clay region. The bricks burned at temperatures of 950 and 1050 C°٬ and the longitudinal Shrinkage tests, bulk density, water absorption, compression strength, and efflorescence were measured. The X-ray diffraction analysis was executed to determine the formed metal phases. The results of the tests showed a direct proportion between longitudinal contraction and water absorption ratio with the addition of sulfur ore and high burning temperature. While bulk density and compression strength are inversely proportional to the sulfur ratio and high burning temperature. Efflorescence tests showed a decrease in the efflorescence rate with an increase in the proportion of sulfur ore.

Deep regolith weathering controls δ30Si composition of groundwater under contrasting landuse in tropical watersheds

Land use changes are known to alter terrestrial silicon cycling and the export of dissolved silicon from soil to fluvial systems, but the impact of such changes on groundwater systems remain unclear. In order to identify the processes responsible for groundwater geochemistry and to assess the impact of agricultural processes, we examined multiple isotopic tracers (δ30Si, oxygen (δ18O) and hydrogen (δ2H) isotopes) in groundwater, soil porewater and surface water from two contrasted watersheds having the same gneissic lithology, one forested (Mule Hole) and one intensely cultivated (Berambadi) in the Kabini basin in South India. In the cultivated watershed, groundwater exhibits high Cl− and NO3− concentrations indicative of fertilizer inputs and solute enrichment from evapotranspiration due to multiple groundwater pumping/recharge cycles. The DSi concentration in groundwater is significantly higher in the cultivated watershed (980 ± 313 μM) than in the forested one (711 ± 154 μM), indicating more intense evapotranspiration due to irrigation cycles. The groundwater δ30Si values ranged from 0.6 ‰ to 3.4 ‰ and exhibit no significant differences between cultivated (1.2 ± 0.5 ‰) and forested (1.0 ± 0.2 ‰) watersheds, indicating limited impact of land use and land cover. Groundwater also shows no significant seasonal differences in DSi and δ30Si within watersheds, indicating a buffer to seasonal recharge during wet season. The δ30Si of a majority of groundwater samples fits a steady-state open flow through system, with an isotopic fractionation factor (30ε) between precipitating phase and groundwater ranging from −1.0 ‰ and − 2.0 ‰, consistent with precipitation of kaolinite-type clays, dominant in the study area. The steady-state flow through system in groundwater can be interpreted as a continuous DSi input from mineral weathering reactions with a dynamic equilibrium between Si supply and precipitation of secondary phases. We also observe, in both watersheds, similar DSi and δ30Si values in local surface water that includes small streams and a river (406 ± 194 μM, 1.6 ± 0.3 ‰) and in soil porewater (514 ± 119 μM, 1.6 ± 0.2 ‰). Compared to soil porewater, groundwater exhibits significantly lower δ30Si signatures and higher DSi, reflecting the contribution of an isotopically light silicon source, resulting from water-rock interaction during percolation through the unsaturated zone. We assign this steady input of DSi to the weathering of primary silicate minerals in the regolith, such as Na-plagioclase, biotite and chlorite, with formation of kaolinite and smectites type clays. A simple isotopic mass balance suggests that deep regolith weathering can contribute to almost half of the DSi in groundwater. We conclude that silicon cycling in soil porewaters, and surface waters are directly impacted by land use, while the isotopic composition of groundwater remains unaffected. Our results indicate that Si isotopic signatures of weathering, adsorption, and plant uptake occurring in the shallow soil and saprolite horizons are partly overprinted and homogenized by the regolith weathering in the deep critical zone, irrespective of land use and seasonality.

Profiling of Tayammum Clay Product in Malaysia by Spectroscopic-Chemometric Approach

Tayammum is a dry purifying method that uses earthen materials, mostly clay. The technique is applied when there is no access to water or in specific circumstances, such as when a person has susceptible skin on water. In tayammum, Islamic law describes clay as pure dust or soil used as a cleansing agent. Nevertheless, no scientific report examined the components of clay present in tayammum clay. Therefore, this study aimed to characterise and profile the mineral composition of tayammum clay, which is a commercially available product in Malaysia. Twelve commercial clay samples and one representative sample were analysed by ATR-FTIR spectroscopy in the range of 4000 to 600 cm-1. PCA exploratory analysis clearly demonstrated the differentiation of the tayammum clay product into seven groups according to its functional group. Following the FTIR analysis, the samples underwent examination using X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectrometers further to identify the mineral and element composition of the clay, respectively. The XRD analysis indicated that there were possibly four types of mineral powder commonly distributed in the market for Tayammum purposes which are three types of clay: palygorskite, kaolinite, and phengite, and another one is zeolite-type: Na-heulandite. All four of them are common materials used for adsorbent and cleansing purposes.

The effect of biosecurity heat treatment on soils: implications for soil analytical methods and mineral exploration

Soils are widely used as geochemical sample media. A recent advancement in soil analytical methods for exploration developed in Australia, the UltraFine+ ® method, concentrates the clay-sized fraction of <2 µm and then analyses this fraction for over 50 elemental concentrations, pH, electrical conductivity and spectral mineralogy/properties (i.e., visible –near- to shortwave and mid- infrared reflectance spectroscopy). This new approach was initially limited to Australian soils due to strict biosecurity legislation. However, since 2022 samples can be shipped to Australia and heat-treated to 160 °C to be released from quarantine-approved premises prior to analysis. A study was undertaken to determine the influence of the temperature heat treatment on the spectral and geochemical properties of soils. One hundred and three soils were collected from multiple regions of Australia to provide a background set of samples to test the effect of heat treatment on the analytical response using the clay-sized fraction analytical method. These soils comprised multiple clay types and are representative of general soil types and target commodities in mineral exploration settings. Results show that heat treatment did not significantly impact elemental abundance of common pathfinder and target elements in minerals exploration with strong correlation and linear trends between the treatments. Spectral parameters measured in the visible to mid infrared range were also unaffected by heating. Some observed elemental changes were related to inconsistent extraction of resistate elements (Hf, Nb, Zr). Counter to other studies, a pH decrease was observed in heat-treated samples. The study concludes that biosecurity release heat treatment at 160 °C does not hinder analysis of the ultrafine fraction soils with a concentrated aqua regia assay and spectral mineralogy measurements.

Archaeometric analysis of pottery sherds from Barveh Tepe: Insights into Early Bronze Age pottery‐making techniques and firing temperatures

AbstractBarveh Tepe, an archaeological site from the Early Bronze Age in the Zagros Mountains of Iran, was the focus of an archaeometric analysis in this study. The aim was to evaluate the firing temperature of excavated pottery sherds from Barveh Tepe and to gain insights into the pottery‐making techniques employed. A range of analytical methods, including optical microscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy‐dispersive X‐ray spectroscopy (EDS), thermal gravimetric analysis (TGA) and X‐ray diffraction (XRD), was utilized to characterize the pottery sherds. The results revealed the utilization of two primary types of raw clays: calcite‐rich (calcareous) and calcite‐poor (non‐calcareous). The presence of calcite in calcareous pottery samples was confirmed, with the calcareous pottery showing a low CO3−2 vibrational band, indicating a low firing temperature. Through the integration of SEM images, FTIR spectra, TGA curve and XRD pattern results, the estimated firing temperature range for Barveh Tepe pottery was determined to be between 600 and 1100°C. These findings provide new insights into the pottery‐making practices of the Early Bronze Age and shed light on the technological advancements of the period.

Enhancement of solar water disinfection using different types of clay

This study delves into the impact of incorporating natural nanoparticles (mineral clays) into contaminated water during the Solar water disinfection (SODIS) process. The experiment involved introducing contaminated water samples into glass containers containing 1 × 10−3 gm/ml of a specific clay type. These containers were then exposed to solar radiation for varying time intervals. Subsequently, samples were extracted from each container, and the total counts of Total Coliform, P. aeruginosa aeruginosa, and E.coli were measured using the IDEXX setup. The results revealed that Zeolite, a specific type of clay, exhibited the shortest disinfection process among the mineral clay samples. The optimal concentration of Zeolite, which effectively reduced the concentration of Total Coliform, P. aeruginosa, and E.coli concentration, was 1 × 10−3 gm/ml. In conclusion, adding Zeolite to wastewater was observed to positively impact the disinfection process, accelerating the inactivation process by reducing the number of pathogenic microorganisms.

The Role of Different Clay Types in Achieving Low-Carbon 3D Printed Concretes

Concrete 3D printing, an innovative construction technology, offers reduced material waste, increased construction speed, and the ability to create complex and customized shapes that are challenging to achieve with traditional methods. This study delves into the unique fresh-state performance required for 3D printing concrete, discussing buildability, extrudability, and shape retention in terms of concrete rheology, which can be modified using admixtures. Currently most 3D printing concretes feature high cement contents, with little use of secondary cementitious materials. This leads to high embodied carbon, and addressing this is a fundamental objective of this work. The research identifies attapulgite, bentonite, and sepiolite clay as potential concrete admixtures to tailor concrete rheology. Eight low-carbon concrete mixes are designed to incorporate GGBS at a 50% replacement level and are used to measure the influence of each clay on the concrete rheology at varying dosages. A comprehensive rheological test protocol is designed and carried out on all mixes, together with other tests including slump-flow and compression strength. The objective is to determine the applicability of each clay in improving the printability of low-carbon concrete. The findings reveal that at a dosage of 0.5%, sepiolite was seen to improve static yield stress, dynamic yield stress, and rate of re-flocculation, resulting in improved printability. The addition of attapulgite and sepiolite at a dosage of 0.5% by mass of binder increased compressive strength significantly; bentonite had very little influence. These gains are not repeated at 1% clay content, indicating that there may be an optimum clay content. The results are considered encouraging and show the potential of these clays to enhance the performance of low-carbon concrete in 3D printing applications.

The Impact of Polyphosphates on the Colloidal Stability of Laponite Particles.

The effect of polyphosphate (polyP) adsorption on the colloidal properties of disc-shaped laponite (LRD) particles was examined in aqueous dispersions with a focus on elucidating the interparticle forces that govern the colloidal stability of the systems. The charge and aggregation rate data of bare LRD exhibited an ionic strength-dependent trend, confirming the presence of double-layer repulsion and van der Waals attraction as major surface interactions. The charge of LRD particles significantly increased in magnitude at elevated polyP concentrations as a result of polyP adsorption and subsequent overcharging of the positively charged sites on the edges of the LRD discs. A transition from stable to unstable LRD colloids was observed with increasing polyP doses indicating the formation of aggregates in the latter systems due to depletion forces and/or bridging interactions induced by dissolved or adsorbed polyP, respectively. The degree of phosphate polymerization influenced neither the charge nor the aggregation mechanism. The findings clearly confirm that polyP adsorption was the driving phenomenon to induce particle aggregation in contrast to other clay types, where phosphate derivatives act as dispersion stabilizing agents. This study provides valuable insights into the early stages of aggregation in colloidal systems involving LRD and polyPs, which have a crucial role in predicting further material properties that are important to designing LRD-polyP composites for applications such as potential phosphate sources in chemical fertilizers.