Search Results (30)

Clays are fundamental raw materials in the ceramics industry due to their plasticity, mineralogical composition, and thermal behavior. This study characterizes four clay samples from Bustos (Portugal), aiming to assess their suitability for ceramic applications through granulometric, geochemical, mineralogical, and technological assays, looking at aspects such as their plasticity and sintering behavior. A textural analysis of the samples revealed distinct granulometric profiles, being dominated by silty–clayey fractions and low amounts of coarse particles, indicating high plasticity potential. Three samples showed an alkaline pH (8.17–8.63), and one an acidic pH (5.11), which can significantly influence the rheology and firing behavior of the ceramic body. Samples had a predominance of phyllosilicate minerals, followed by quartz and magnetite–maghemite, and trace amounts of feldspars, anatase, bassanite, and siderite. In the clay fraction, smectite, illite, and kaolinite were identified. By combining classical analysis techniques with ceramic technology principles, this study contributes to the sustainable development of local ceramic industries, emphasizing the importance of characterizing natural raw materials for industrial applications. The plasticity tests showed strong workability in two samples, which exhibited high values of plasticity and moldability, making them suitable for shaping processes in ceramic production. Also, sintering behavior tests revealed that the same clays exhibited good densification during firing, with relatively low shrinkage. Full article

Between the 5th and 8th centuries AD, several (semi-)nomadic populations invaded ancient Tokharistan (Central Asia), introducing political, socio-economic and cultural changes that also affected pottery production. The study of ceramic materials thereby represents a useful tool for shedding light on the transformations related to such historical events. Unfortunately, no systematic research on ceramics from this region and this period has been conducted to date, and the information available mostly concerns the formal characteristics and imprecise relative chronologies. Aiming to contribute to the knowledge of Early Medieval pottery production in the territory north of the Amu Darya, we present a preliminary investigation on tableware and common wares recovered in the settlements of Khosijat Tepe, Shurob Kurgan, Balalyk Tepe and Dabil Kurgan. This paper provides new data on the vessels’ morphological/stylistic characteristics and relative chronologies, allowing their contextualisation and categorisation. In order to explore the manufacturing processes and their provenance (production areas), a multidisciplinary approach that combines WD-XRF, powder XRD and thin-section optical microscopy was carried out, allowing us to determine the chemical, mineralogical and petrographic compositions, respectively. The results suggest that most vessels consist of local/regional products. The choice and processing of the raw materials are broadly similar. However, slight variations are observed among the ceramics from distinct sites, related to the procurement of clayey sediments from different sources. Although a certain degree of morphological and technological continuity regarding the preceding Kushano-Sasanian pottery tradition is attested for some functional categories, new shapes and decorations appear, confirming the introduction of new practices in the region. Full article

The challenge of improving the quality of ceramic products is faced worldwide, especially in areas where artisanal production is common and the need for in-depth knowledge about raw materials, together with inefficient production processes, limits the advancement of the ceramic industry. Scientifically, detailed investigation of ceramic masses’ physical, chemical and mechanical properties can provide essential insights to optimize production, contribute to developing more advanced and sustainable techniques, and increase competitiveness. This study evaluated raw clay materials and ceramic masses obtained from northeastern Brazilian, focusing on their chemical composition, mineralogical phases, thermal behavior, and particle size distribution. Rectangular samples (80 mm × 20 mm × 7 mm) prepared using uniaxial pressing (25 MPa by 30 s) were fired at different temperatures (950 and 1050 °C) and linear shrinkage, flexural strength, water absorption, and apparent porosity measurements were taken. The results showed that the companies still need to improve the production process to meet the minimum strength requirement of 1.5 MPa according to the Brazilian standard NBR 15270. Full article

The unconfined compressive strength (q_u) weakness of low-compressibility clay (CL) reduces its structural safety. As part of the present study, waste glass powder (WGP) was mixed with Portland cement to improve the geotechnical properties of clayey soil, thus contributing to sustainability through the recycling of municipal waste. Based on the stiffness and chemical composite of WGP and cement, the adopted mixing ratio of the mixed soil was 10% and 20% WGP and 3% and 6% cement. The soil mixing ratio was selected and tested considering the percentage of the cement, WGP, water/cement ratio, dry unit weight, porosity of the specimen, and curing times of 7 days and 28 days. SEM-EDS tests were conducted to examine the impact of raw materials on the microstructural mixed soil. The results from SEM-EDS show that the cement–WGP–CL mixture caused different degrees of cementation and bonding products. Modifying multiple layers of water in the particle of the clay surface led to the enhancement of the interaction of the interlayer of hydrated clay, achieving the best unconfined compressive strength and stiffness of the designed specimen. From the viewpoint of unconfined compressive strength and stiffness enhancement, blending content of 20% WGP and 6% cement and dry unit weights compaction was recommended for stabilizing CL. The process of q_u and stiffness improving CL involved an optimized mixing ratio and particle densification reaction efficiency. The soil’s q_u and stiffness were predicted using ANN (artificial neural networks) and the porosity/cement index was predicted based on the experimental results. Full article

The damming of watercourses results in sediment accumulation and, therefore, in the reduction of useful storage capacity. The storage capacity can be recovered through dredging, but this process generates large volumes of sediments that require proper management. To avoid landfilling and promote recovery operations, sediment characterization is the preliminary step to any assessment and decision. This paper presents the results of tests on sediments sampled at two reservoirs in southern Italy, the Camastra and the San Giuliano, in Basilicata. These investigations include testing of organic matter, heavy metals grain size distribution, and the assessment of the pollution degree. A lack of correlation between the sampling point and the heavy metal content was observed in sediments, except Be, Cr and Ni for the San Giuliano reservoir. This may be attributed to the presence of agricultural activities and fertilizer use in its watershed. Similarly, there is no dependence between the organic carbon and the grain size distribution, the former being scarcely found in both reservoirs (on average 0.91% for the Camastra sediments and 0.38% for the San Giuliano sediments), the latter being predominantly characterized by sandy matrices downstream of the reservoirs (on average 64.3% ± 32.9%) and by silty-clayey matrices in the upstream areas (on average 65% ± 14.3%). Finally, the determination of the single pollution index P_i and the Nemerow integrated pollution index P_N highlights that sediments are not contaminated with heavy metals. Most of them show values of the indices above between 0 and 1 (“unpolluted”) and, in a few cases, values between 1 and 2 (“poorly polluted”). The findings suggest that these sediments can be reused for environmental and material recovery, using them as secondary raw materials for sub-bases and embankments, for filling in disused quarries, for reprofiling and reconstructing the morphology of coastlines or riverbeds, for beach nourishment and in the agronomic and construction industry fields. Full article

In the hinterland of Soverato (in the Catanzaro province CZ) in Calabria, Italy, in the territory of Gagliato, on a series of terraced plains, the remains of an extensive settlement have been identified with archaeological evidence that includes the various phases of the protohistoric period and the Greek age. In the settlement, numerous protohistoric ceramic finds consisting in fragments of vascular shapes of various sizes and large dolia were recovered. This paper presents the preliminary results of the mineralogical, petrographic and paleontological analyses performed on dolia samples selected on the basis of the typology and the characteristics of the ceramic impasto. The dolia analyses were obtained through various analytical techniques. Petrographic and micropaleontological studies were performed using polarized optical microscopy (POM). The mineralogical analyses were carried out using X-ray diffractometry (XRD), both on selected ceramics and on the clayey and sandy sediments sampled for comparison around the settlement area. Furthermore, micromorphological observations have been performed, using scanning electron microscopy (SEM), on selected foraminiferal tests picked up from the clay sediments collected in the study area. Data highlight the remarkable compatibility between the mineralogical composition of the dolia and the sampled sediments, and they confirm that the raw materials for ceramic production may have occurred in an area not far from the settlement, as assumed by archaeologists. Full article

Clayey raw materials present a wide variety of uses depending on their specific composition. Bentonite-like clays are considered suitable candidates to be used in some industrial applications, such as pharmaceutics, catalysis, antibacterial agents or food additives because of their highly desired adsorption properties, concretely regarding water vapor behavior. In the present study, a specific methodology for the characterization of some clayey raw materials used in the ceramic industry and its correlation with water vapor sorption properties is presented. Six different clayey raw materials have been wholly characterized until their specific chemical formula are obtained, and their water vapor adsorption behavior was correlated to their specific composition. The whole protocol has been validated with certified standard reference materials. The obtained results show a relationship between montmorillonite content in clay with water vapor adsorption behavior and certain thermal events of clayey particles, which can help the industry to understand product behavior and characterization during ceramic manufacturing process. Full article

Sedimentary phosphate extraction in open-pit operations generates large volumes of waste rock (WR), which are mainly overburdens and interburdens. Traditionally, the WR is mixed and stored on the surface in waste rock piles (WRPs). This paper presents a case study of the Benguerir mine site in Morocco. It investigates the potential valorization of each WR lithology based on the geological and geomechanical properties to reduce their environmental footprint and create added value to “waste.” The WR samples (soils and rocks) were collected from drill cores and mining trenches in the Benguerir mine. The geological characterization results using petrographic descriptions indicate the presence of nine phosphate layers and, in addition to the overburdens, eight interburdens. Four types of WR are identified: carbonate, siliceous, marly clay, and phosphate. The geomechanical characterization of soil-like samples showed an average plasticity index (PI) of 50% according to the methylene blue value (MBV) of 7.1, classifying them in the A3–A4 categories as plastic and clayey marl soils. The hard rock samples have excellent mechanical properties in terms of their uniaxial compressive strength (UCS), Los Angeles abrasion value (LA), and micro-Deval value (MD). The average compressive strength is 104 MPa for the flint, 35 MPa for the phosphate flint, 32 MPa for the silexite, 26 MPa for the limestone, 11 MPa for the indurated phosphate, and 8 MPa for the marly limestone. Based on the obtained results, these WRs can be considered as an excellent alternative secondary raw material for use in civil engineering applications, ceramics, and cement industries. Full article

Water potabilization sludges (WPS) are a heterogeneous waste generated from the coagulation–flocculation process of drinking water production, whose composition is highly dependent on the geological context of reservoirs, the composition and volume of treated water, and the types of coagulants used. For this reason, any feasible approach for reusing and valorising of such waste cannot be disregarded from the detailed investigation of its chemical and physical characteristics and they have to be evaluated at a local scale. In this study, WPS samples from two plants serving the Apulian territory (Southern Italy) were subjected for the first time to a detailed characterization with a view to evaluating their recovery and reuse at a local scale as a raw material for producing alkali activated binders. WPS samples were investigated by X-ray fluorescence (XRF), X-ray powder diffraction (XRPD) including phase quantification by the combined Rietveld and reference intensity ratio (RIR) methods, thermogravimetric and differential thermal analysis (TG-DTA), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). Samples showed aluminium–silicate compositions with up to 37 wt% of Al₂O₃ and up to 28 wt% of SiO₂. Small amounts of CaO were also found (6.8 and 4 wt%, respectively). The mineralogical investigation indicates the presence of illite and kaolinite as clayey crystalline phases (up to 18 wt% and 4 wt%, respectively), in addition to quartz (up to 4 wt%) and calcite (up to 6wt%) and a large amorphous fraction (63 wt% and 76 wt%, respectively). WPS were subjected to heating from 400 °C to 900 °C and mechanical treatment by high energy vibro-milling in order to determine the best pre-treatment condition in view of their use as solid precursors to prepare alkali-activated binders. Alkali activation (8M NaOH solution; room temperature curing) was attempted on untreated WPS, on 700 °C heated and on 10-minute high-energy milled samples, which were considered the most suitable based on the preliminary characterization. Investigations of alkali-activated binders confirmed the geopolymerisation reaction occurrence. Variations in gel features and compositions depended on the amount of reactive SiO₂, Al₂O₃ and CaO available in the precursors. WPS heated at 700 °C led to the most dense and homogeneous microstructures, due to a greater availability of reactive phases. The results of this preliminary study demonstrate the technical feasibility of preparing alternative binders from the investigated Apulian WPS, paving the way for a local reuse of these waste products, leading to economic and environmental benefits. Full article

Corinth, Achaea in the northern Peloponnese, and Nicopolis in Epirus (Greece) have a strong archaeological record of ceramic production, from the Early Helladic to Late Roman periods. Important archaeological sites, such as Helike, Aigeira, the settlement of Derveni, and the cities of Patras and Nicopolis, offer data and findings of exceptional quality. One of the main pillars for the development of the ceramic production in these areas was the availability of local natural resources, among which are the clayey sedimentary deposits that outcrop in the area. This study investigates the physical-technological properties (plasticity and granulometry), the mineralogical composition of clayey raw materials, in order to test their suitability for ceramic production across the entire geographic area. Our aim was to differentiate the three main “ceramic” provinces, based upon the above-mentioned properties. New data from western Achaea and south Epirus are presented and compared with previous research conducted in Corinthia and eastern Achaea. The results obtained showed that the clays sampled from Corinthia and eastern Achaea are carbonatic materials of poor plasticity, whereas those from western Achaea and Epirus are either Ca-rich or Ca-poor materials, with the majority exhibiting a better plasticity. The results from this study are expected to constitute an important archaeometric tool for tackling archaeological issues by means of provenance and ceramic technology within the region and in the surrounding areas. Full article

The paper presents experimental results regarding the synthesis of Portland clinker starting from raw mixes based on two types of clayey precursors, i.e., clay and marl (the most common types of raw materials used in the cement industry), with and without glass waste content. The soda-lime glass waste addition (5.36–5.59 wt %), used to control the silica ratio of the raw mix, improved the raw mix burnability and decreased the calcination temperature (by 20 °C), leading to a decrease in fuel consumption and contributing to the reduction in CO₂ emissions associated with clinker and cement production. The clinkers obtained by the calcination of raw mixes with glass waste content at 1430 °C with a 30 min plateau had a similar mineralogical composition and microstructure to the clinkers obtained from the reference raw mixes and fulfilled the requirements of the specific standard EN 197-1. The obtained clinkers were used to produce two types of Portland cement, i.e., a unitary cement (CEM I) and a binary blended cement with slag (CEM II/B-S). The main characteristics of these cements, i.e., loss on ignition, insoluble residue, sulfate and chloride contents, as well as the setting time and soundness, meet the conditions stipulated in the EN 197-1 standard. The values of compressive strength, assessed on mortars after 2, 7 and 28 days of curing, allow the classification of all CEM I cements in the 42.5 R class. In the case of CEM II/B-S cements, those obtained from raw mixes with clay can be classified in the 42.5 N class, while those obtained from raw mixes with marl are classified in the 32.5 R class. Full article

The sedimentary clays of the Douala sub-basin (Cameroon) were studied to determine their mineralogical composition and physicochemical properties to boost their potential suitability as materials for traditional ceramics and eventually modern ceramics. These clayey materials are not widely used locally as building materials and little data are available on these materials in the field of ceramics and they are relatively unknown. Three profiles from 3.9 to 7.4 m thickness were studied on the field in order to determine their mineralogical (X-ray diffraction, infrared), chemical (X-ray fluorescence) and physicochemical (particle size, Atterberg limits, organic matter, cation exchange capacity and hydrogen potential) properties. Globally, ten (10) clay samples were analyzed to highlight the nature and technological properties of these clays. Mineralogically, kaolinite (48.3–69.2 wt.%) and quartz (20.5–41.2 wt.%) were the most abundant minerals in these raw clay materials. They were associated with a very small or moderate quantity of illite, hematite, goethite, feldspar, gibbsite and micas. Geochemically, the clayey materials had high silica (SiO₂, 22.21–58.03%) and alumina (Al₂O₃, 12.84–22.94%) contents, with a significant amount of iron oxides (Fe₂O₃, 1.07–17.92%). Other oxides (K₂O, MgO, TiO₂, Na₂O, MnO, CaO and P₂O₅) were in a relatively lower proportion. A high level of alumina content explains the kaolinitic nature of these clayey materials. The results of the granulometric analysis of the clayey materials showed the following distribution: clay (26–99%) followed by silt (1–70%) and sand (0–4%). This corresponds to silty clay soils according to the Belgian textural classification diagram, with high plastic index (63.9%) characteristics. The studied clay materials are good candidates for the production of ceramics and terracotta building. This study is therefore important for any application of this type of clay in various industrial fields. Full article

This study aims to compare two approaches for the reserve calculation of cement raw material by geological sections and structural maps. The first is legally based, and its accuracy is approved by periodical calculation of the exploited material on site. In this research, it was crucial to determine deviation in the calculation approach, i.e., geological section volume calculation versus the volume obtained as a software solution estimated as a number of cells between two structural maps, i.e., maps interpolated at the top and bottom of the analysed lithological unit. Due to complex mineralogy, raw cement needs different energy consumption that directly affects the procedure of cement production, e.g., increases in air pollution through CO₂ emissions. The research area was the exploitation field “St. Juraj–St. Kajo,” situated near the town of Split, region of Dalmatia, Southern Croatia. In the deposit, there are seven different lithological units, and all were technologically divided based on their chemical compounds. The lithology included dominantly marl and sandstone with occasional alternations of the conglomerate. Although in the geological sense it is considered a single unit, it partially contains interlayers in the form of lenses such as limy (calcitic) marl, clacisiltite (clayey limestone), and clayey marl. Generally, the knowledge of interlayers’ existence is more important than their exact quantity because it affects expectations of a nonuniform material’s technological quality at the location. For the purpose of the analysed lithological unit calculation, the volumes of the interlayers within were determined as well. Using geological sections for volume calculation is based on the calculation of the block volume (V) between two parallel vertical sections (P₁, P₂), which is obtained as a product of the mean areas (Paverage) of adjacent parallel sections (P₁, P₂) multiplied by the distance between them (d). Structural maps represent the calculation of the volume of the analysed object under a function f (x, y) defined by a double definite integral. Comparison of research results encourages the use of software solutions for the volume calculation of cement raw material volume in the future. Full article

Siltation is the biggest environmental challenge associated with nickel laterite mining in the Philippines. The amount of silt generated is huge and one mitigation strategy currently employed by the mining companies is the construction of siltation ponds where the bulk of the clayey- and silt-sized surface runoffs is collected. However, this poses several serious environmental hazards such as landslides due to heavy rainfall and the potential release of hazardous heavy metals. A promising approach to reduce the risks associated with long-term storage of nickel mine waste (NMW) is to employ circular economy by repurposing it for ceramic applications. While generating useful materials with economic value out of a mine waste, it will result in a reduction in volume of waste for disposal. In this study, the method employed to produce NMW-based ceramic wall and floor tiles is slip casting as it is the most appropriate method in forming tiles with complex surface features. Five formulations of NMW-based slips were made for the casting of ceramic tiles and each slip was characterized for its suitability as raw material. The results of NMW characterization show that NMW could be utilized as raw materials for both ceramic wall and floor tiles and the addition of feldspar can enhance casting and physical properties. Full article

This study included the testing of normal (Gaussian) distribution of input data and, consequently, spatially interpolating maps of chemical components and cement modules in the flysch. This deposit contains the raw material for cement production. The researched area is located in southern Croatia, near Split, as part of the exploited field “St. Juraj–St. Kajo”. There are six lithological units: (1) alternation of marls and sandstones with inclusions of conglomerates, (2) marl, (3) calcsiltite, (4) calcarenite, (5) marl with nummulites, (6) debrites, and (7) clayey marl. All of them are deposited in the (a) northern and (b) southern beds. Only debrites are divided into the (a) western and (b) eastern layers. Those lithological units were divided technologically based on their cement modules (lime saturation factor (LSF), silicate module (SM), and aluminate module (AM)). The average thicknesses were analysed, followed by normality tests (Kolmogorov–Smirnov (K–S) and Shapiro–Wilk (S–W)) of the chemical analyses: CaO, SiO₂, Al₂O₃, Fe₂O₃, MgO, SO₃, Na₂O, K₂O, CaCO₃ (%) and three cement modules (LSF, SM, AM), available in the six lithological units. The normality tests were applied based on a number of input data. The further interpolation was performed using two methods, kriging and inverse distance weighting, mapping CaO (%), SiO₂ (%), and LSF (−) in three different lithological units. The interpolation methods were selected based on two criteria: (a) normality test pass or fail and (b) the amount of data. In total, 144 tests were calculated, including sets from 7 to 36 points. The results show the current situation in the quarry, after decades of production, making reliable the future predictions of cement raw material exploitation. Full article