Clayey Raw Materials Research Articles

Tracing the origin of raw materials used for the production of ancient ceramics: a case study of multi-period archaeological sites in the Turopolje area (Continental Croatia)

The selection of raw materials for ancient pottery production was influenced by a variety of technological and cultural factors, underscoring the importance of characterising these materials to understand the technology of ancient societies. This research examines ancient ceramics from two multi-period archaeological sites: Staro Čiče-Gradišće (Neolithic, Copper Age, Copper/Early Bronze Age, Early Bronze Age, Late Bronze Age, Roman period, and Late Mediaeval period) and Kurilovec-Belinščica (Early Bronze Age and Middle/Late Bronze Age), alongside potential clayey raw materials collected near these settlements. Using a multi-analytical approach (optical microscopy, X-ray powder diffraction, mass and emission spectrometry, and laser granulometry), the research aims to determine the characteristics of the paste recipes (raw clay and tempers) and to examine the type and provenience of the raw materials used for ancient pottery production over different periods of the past (from the Neolithic to the Late Mediaeval period). The results showed that ancient potters preferred to use moderately plastic, sandy clay, while Bronze Age potters often used highly plastic clay. Potters utilised various non-plastic tempering materials, such as sands and gravels, grog, and mollusc shells, with their choice being influenced by the need to enhance technological properties as well as by regional and culturally determined pottery traditions. Most of the ceramics are of local origin, made from easily available raw materials that represent flood sediments of the nearby Sava River. However, non-local materials were detected in Neolithic samples, indicating the presence of exchange networks among those communities.

Evaluation of Clayey Raw Materials and Ceramic Masses from Ceramic Building Material Companies Located in Northeastern Brazil

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.

Effect of the coconut fibers and cement on the physico-mechanical and thermal properties of adobe blocks

This work aimed to investigate the effect of cement and coconut fibers on the thermal and physico-mechanical characteristics of adobe blocks. Thus, a clayey raw material consisting of kaolinite (62 wt%), quartz (31 wt%), goethite (2 wt%) with a plasticity index of 21.5 % was used to manufacture adobe blocks amended with cement and coconut fibers. First the adobe blocks were formulated with an optimal cement content of 4 wt% before adding coconut fibers up to 1 wt%. The physico-mechanical and thermal characteristics of manufactured composites were then studied. According to the results obtained, the incorporation of coconut fibers into the clay-cement matrix decreases the apparent density and volume shrinkage and increases the porosity of the adobe blocks. The presence of coconut fibers in adobe blocks promotes the phenomenon of water absorption. The combined effect of the formation of calcium silicate hydrate (CSH) and hydrogen bonds between fibers molecules and those of clayey minerals leads to an improvement in the mechanical properties of adobe blocks. The thermal conductivity of adobe blocks decreases with the fiber content due to the presence of pores and cellulose molecules in the fibers which have an insulating nature. Taking into account their physico-mechanical and thermal properties, adobe blocks containing 0.6 wt% coconut fibers and 4 wt% cement are suitable for building sustainable habitats and thermally comfortable.

The influence of addition of fly ash from biomass combustion on selected properties of red building ceramics

The paper characterizes waste in the form of fly ash generated in a power plant during the combustion of biomass in a fluidized bed in terms of its possible use in the ceramic building materials industry. This is important from the point of view of environmental protection. In order to assess the possibility of using ash in the production of red ceramics (e.g. bricks), two different clay raw materials (Clay I and Clay II) were selected to prepare the raw material sets. First of all, the investigated fly ash was subjected to thermogravimetric TG-DTG analysis and its basic chemical composition was determined. Then the specific density was determined for all the raw materials, XRD analysis was also performed and finally characteristic temperatures were determined by means of a high-temperature microscope. The basic raw material sets included clayey raw material and fly ash in various contents: 5 wt%, 10 wt% and 15 wt%. Samples were pressed from the ready sets and fired at the temperature of 1000℃. Afterwards, the obtained samples were subjected to XRD and microstructural tests, then selected physical properties were determined, i.e. water absorption, porosity, apparent density, and compressive strength. Based on the research and analysis of the results, it was found that the introduction of fly ash from biomass combustion into the raw material set in the range of 5–15 wt% has a positive effect on the insulating properties of red ceramics. In addition, the density of the red ceramics decreases with the increase in the addition of fly ash, while its porosity and water absorption increase. Furthermore, the addition of fly ash decreases the compressive strength and visually brightens the microstructure of the products.

Decoding Capua’s roof terracotta: A multi-analytical study of the Fondo Patturelli sanctuary and Alveo Marotta furnace (6th century BCE – 1st century BCE)

The main focus of this study was to examine 25 samples of archaeological ceramic materials currently preserved in the Archaeological Museum of the Ancient Capua and Mitreo investigated in the framework of an international project. These samples primarily consist of architectural terracotta from the Fondo Patturelli extra-urban sanctuary, as well as architectural terracotta, pottery and waste material from the nearby Alveo Marotta furnace.To investigate these artifacts, a multi-analytical mineralogical-petrographic approach was performed. Thin section observations revealed that almost all samples exhibit a coarse-grained paste. The fragments were categorized into three petrographic groups based on the type and quantity of temper, which is mostly composed of volcanic grains. They include lithics and juvenile fragments (obsidians and pumices) ascribed to the products of the major Campanian eruptions as detected via FESEM-EDS. Bulk chemical analyses (WD-XRF) show that almost all samples form a homogeneous group made with Ca-rich clayey raw materials, also including three wastes of tiles from the Alveo Marotta. By contrast, other two wastes from Alveo Marotta were produced with Ca-poor clay suggesting the use of a different raw material.From a technological point of view the samples are characterized by a thermal range that varies from 750 to 900 °C, notably different between the earlier and later production periods, with the former fired at lower temperatures.

A Tailored Approach in the Bentonite-like Raw Material Characterization Using Thermal and Water Sorption Techniques

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.

Incorporation of wine industry waste into red ceramic: study of physical and mechanical properties

This study examines the potential of adding grape skins to red ceramics to evaluate its effect on the physical and mechanical properties of the clayey body. Five compositions were prepared with different percentages of biomass incorporation: 0%, 2.5%, 5%, 7.5%, and 10%. The specimens were conformed using vacuum extrusion in a laboratory extruder, with dimensions of 120 mm in length and a straight section of 30 × 15 mm. After drying, the pieces were sintered in a laboratory muffle furnace at 700 °C, 800 °C, 900 °C and 1000 °C. Chemical, mineralogical, thermal, physical, morphological, and microscopy tests were conducted on the clayey raw materials. An acceptable formulation was achieved by incorporating up to 5% biomass, fired at 900 °C. For water absorption, the incorporation of up to 5% of biomass fired at 700 °C satisfies the normative limits to produce structural blocks and sealing blocks. From 900 °C onwards, it meets the parameter intended for making roof tiles. The linear shrinkage of the pieces fired up to 900 °C is slightly altered by the incorporation of up to 5% of biomass fired under 800 °C are below 2%. The bending strength, at 700 °C there was an increase in mechanical strength directly proportional to the increase in biomass. However, at 800 and 900 °C, there was a gradual decrease in the bending strength. In turn, at 1000 °C, there was a sudden reduction in bending strenght for all formulations with biomass incorporation.

An Insight into the Suitability of Clayey Raw Materials: The Ceramic Provinces of the Northern Peloponnese and South Epirus, Greece

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.

Ceramic building materials from the ancient Témesa (Calabria region, Italy): Raw materials procurement, mix-design and firing processes from the Hellenistic to Roman period

Ceramic building materials (CBM) are interesting archaeological items for gathering the material culture identity and urban setting of the ancient populations since their production is generally related to the local availability of clayey raw materials and advancements of technological skills of ancient makers.This paper investigates the Hellenistic and Roman productions of ceramic building materials from the archaeological site of Témesa on the Tyrrhenian coastline of Calabria region (southern Italy), a settlement where a flourishing ceramic tradition has been attested for all of its occupation phases, from the late Archaic to the Roman period. Here, the local availability of clayey and sandy raw materials permitted the development of a thriving worksite. A combined study of mineralogical, petrographic and micropaleontological features of archaeological samples and geological raw materials collected nearby the archaeological settlement, permitted to constrain the raw materials sources, and investigate the technological level achieved between the second half of the 4th century BCE and the 3rd century CE.This study highlighted that most of CBM was made by mixing sands from a nearby fluvial deposit with upper Miocene clayey raw materials. Chemical composition and micropaleontological investigation of the foraminiferal content of archaeological samples and clays validated the possible exploitation of local raw materials. Textural parameters and the mineralogical assemblage of temper grains, characterized by the peculiar presence of metamorphic lithics, also attested the use of Savuto river sands. Ceramic technology accounts for a firing process at reasonably high temperatures, evidencing the good technological level of production.Moreover, the presence of samples characterized by mix-designs and mineralogical assemblages consistent with geological materials from Campania region witnesses the importation of ceramic materials from other sites, suggesting the existence of operating trades as already attested for other sites of Tyrrhenian coast.

Assessment of clayey raw material suitability for ceramic production, in the Northern Peloponnese, Greece

The Achaea and Corinth regions of the northern Peloponnese are renowned for their rich archaeological record. Achaea is part of mainland Greece in the North-Western Peloponnese, whereas Corinth is in the North-Eastern Peloponnese. Since ancient times, ceramic production has played an important role in the local and regional social and economic evolution in both regions. Our aim is to identify and evaluate sources of clayey raw materials outcropping in the territory of the northern Peloponnese, potentially used for ceramic production during antiquity, by means of their compositional and technological properties. This was accomplished by the systematic sampling of clayey raw materials from a wide area spanning the Northern Peloponnese. In spite of the inter-regional chemical homogeneity recorded in their geochemical analysis in terms of major, minor, and trace elements, the data obtained led to their intra-regional compositional distinction into calcareous, calcareous-dolomitic, and siliceous clayey sediments. In addition, the presence of the clay minerals (illite, chlorite, smectite, mixed phases), their granulometry, and their bulk mineralogy all proved to considerably influence some of their performance characteristics, such as their plasticity. After a full characterization of the studied material, the clay deposits in all areas did not show significant differentiations, but they did need improvement to be suitable for the production of ceramic artifacts.

Mineralogical and Microstructure Analysis for Characterization and Provenance of Ceramic Artifacts from Late Helladic Kastrouli Settlement, Delphi (Central Greece)

The present study deals with the characterization of a ceramic assemblage from the Late Mycenaean (Late Helladic III) settlement of Kastrouli, at Desfina near Delphi, Central Greece using various analytical techniques. Kastrouli is located in a strategic position supervising the Mesokampos plateau and the entire peninsula and is related to other nearby coeval settlements. In total 40 ceramic sherds and 8 clay raw materials were analyzed through mineralogical, petrographic and microstructural techniques. Experimental briquettes (DS) made from clayey raw materials collected in the vicinity of Kastrouli, were fired under temperatures (900 and 1050 °C) in oxidizing conditions for comparison with the ancient ceramics. The petrographic analysis performed on thin sections prepared from the sherds has permitted the identification of six main fabric groups and a couple of loners. The aplastic inclusions recognized in all fabric groups but one confirmed the local provenance since they are related to the local geology. Fresh fractures of representative sherds were further examined under a scanning electron microscope (SEM/EDS) helping us to classify them into calcareous (CaO > 6%) and non-calcareous (CaO < 6%) samples (low and high calcium was noted in earlier pXRF data). Here, the ceramic sherds with broad calcium separation are explored on a one-to-one comparison on the basis of detailed mineralogical microstructure. Moreover, their microstructure was studied, aiming to estimate their vitrification stage. The mineralogy of all studied samples was determined by means of X-ray powder diffraction (XRPD), permitting us to test the validity of the firing temperatures revealed by the SEM analysis. The results obtained through the various analytical techniques employed are jointly assessed in order to reveal potters’ technological choices.

Evaluation of the Mechanical Behavior of Clay Bricks Stabilized at 4% Cement and Mixed with Limba Wood Waste

In this study, the authors evaluated the mechanical behavior of bricks made of clay material stabilized with 4% cement and mixed with different contents (0; 2; 4; 6 and 8%) of limba wood waste (sawdust and chips). The clayey raw material ANMK was characterized by the method of X-ray diffraction (XRD) on oriented sheets (normal, glycol and heated to 490°C), by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The chemical and mineralogical compositions of cement used were determined by inductively coupled plasma – optical emission spectrometry (ICP-OES) and by X-ray diffraction. This clay material consists of 96% kaolinite and 4% of the chlorite / montmorillonite interstratified. The morphology of the material observed by scanning electron microscopy showed an irregularity of clusters. The elementary analysis by energy dispersive spectroscopy shows that this material is essentially aluminosilicate. The chemical analysis of the cement showed a predominance of CaO (67%) and SiO₂ (21%), however the mineralogical analysis showed the presence of calcite, alite, hatrurite and brownmillerite. This clay material has a mass shrinkage on drying of 26.6% and the linear shrinkage is 6.4%. The formulation with sawdust appears to give greater flexural and compressive strengths than those obtained with chips.

A multitechnique, quantitative characterization of the pore space of fired bricks made of five clayey raw materials used in European brick industry

The development and improvement of brick materials is still based on empirical knowledge and large testing series. To enable a physically based optimization in terms of thermal and mechanical properties of clay bricks, detailed knowledge of their microstructure is required. We here present comprehensive investigations on the pore space of bricks made of five different clayey raw materials used in European brick production. Application and combination of micro-computed tomography and scanning electron microscopy delivered precise pore size distributions based on the real pore diameter and unaffected by the pore throat. The former also enabled to resolve the 3D pore structure down to a pore diameter of approximately 5.5 micrometers and gave access to porosity distributions over the sample's thickness. Furthermore, the brick's true densities were determined applying the Archimedes' principle and verified by helium pycnometry measurements. The extensive database generated in this work and the linking of results from different methods allow for new insights and a better understanding of these often used brick materials.

Ceramic raw materials: how to recognize them and locate the supply basins—mineralogy, petrography

This tutorial paper is focused on the mineralogical-petrographic characterization of clayey raw materials with the purpose of sourcing supply basins and answering questions about the provenance of the corresponding archaeological ceramic artefacts. The first part gives general indications of how to profitably study archaeological ceramic thin sections through the polarizing microscope. Brief notes are provided on the theoretical basis of optical microscopy. A scheme is then provided for the petrographic description of ceramic samples, concerning the textural and compositional characteristics of aplastic inclusions and groundmass. Suggestions are also given for identifying any minero-petrographic marker and establishing minero-petrographic groups (MGP) aimed at archaeological ceramic provenance studies. After broadly describing the geological origin of the clay deposits, there is discussion of how to plan a field survey aimed at the location of clay sources and sampling. The importance of the ethnoarchaeometric approach in provenance studies is also underlined. The third part of the paper describes the preliminary treatments to which the clayey raw materials are subjected before reporting on a grain size analysis and how to proceed when performing experimental firing tests. Finally some suggestions are made about how to compare clay firing tests (experimental briquettes) and archaeological ceramic finds when assessing a production centre.

An end of waste alternative for volcanic ash: A resource in the manufacture of ceramic tiles

The paper deals with an experimental study aimed at assessing the possible re-use of volcanic ash as temper in the manufacture of ceramic tiles. Needing to find end of waste alternatives for this material arises from the awareness that the fall-out of large quantities of ash in active volcanic areas causes many inconveniences to communities living and working in close proximity to the volcano. Volcanic ashes recently erupted by Mount Etna volcano have been here chosen as case study for these purposes. Ceramic test-tiles were manufactured by mixing volcanic ash with a calcareous clayey raw material, by using specific proportions of clay/temper. In order to assess the quality of the products, the tiles underwent several physical–mechanical tests including: a) water absorption; b) bending resistance; c) impact resistance; d) resistance to deep abrasion; e) thermal shock resistance; f) frost resistance; and g) accelerated aging test by salt crystallization. The obtained results have been then compared with those of a reference product manufactured by using another volcanic material known as azolo (i.e., ground basalt) for a long time on the market. Our data demonstrate how basaltic ash recovering through this methodological approach is highly promising in the sector of building materials.

Imobilizacija teških metalnih jona Zn2+, Ni2+, Pb2+ i Cu2+ u strukturi materijala na bazi cementa

Natural zeolite and bentonite were utilized as mineral additives in the mix-design of environmentally safe cement-based building materials. The adsorptive abilities of these two clayey raw materials, i.e. their affinity to immobilize heavy metal ions Zn2+, Ni2+, Pb2+ and Cu2+ were investigated. Singleand multi-solutions of Zn2+, Ni2+, Pb2+ and Cu2+ were prepared for the experiment. The obtained results were submitted to analysis via pseudo-first and pseudo-second order kinetic models. Langmuir and Freundlich isotherms were analyzed. Bentonite exhibited better adsorption affinity than zeolite towards all four investigated cations. As a proof, a leaching test was conducted on seven different cement binders with different mineral additives (fly ash, zeolite, bentonite). The leachates obtained on the samples of cement with addition of fly ash and clay (either zeolite or bentonite) contained lower concentrations of Zn2+, Ni2+, Pb2+ and Cu2+ ions than leachates obtained on the samples of cement binder with fly ash solely as a result of adsorption and hydration mechanisms that immobilized heavy metals within cementitious composites.

Growth of metastable phases during brick firing: Mineralogical and microtextural changes induced by the composition of the raw material and the presence of additives

This paper studies the mineralogical and textural changes that take place during the firing in an electric kiln at 800, 950 and 1100 °C of brick samples made with or without additives. Samples were made with a clayey raw material which was mixed with either halite or calcined diatomite sludge and then fired. These samples were then compared with control samples made without additives. Different analytical techniques (X-ray fluorescence, thermogravimetric and differential scanning calorimetric analyses, X-ray diffraction, polarized optical microscopy and scanning electron microscopy) were used to reconstruct the changes that took place inside the bricks from a mineralogical and textural point of view, changes that are similar to those that take place in nature during pyrometamorphism. The carbonates decomposed and reacted with silicates to form gehlenite, diopside and wollastonite; the plagioclase was enriched in calcium and the quartz concentration fell; the clay minerals favoured the melting of the matrix and the appearance of mullite, and K-feldspar changed from microcline to sanidine. The extent of vitrification increased in line with the increase in the firing temperature. When halite was added, new silicates appeared earlier at lower firing temperatures and molysite was formed, while the most important mineralogical difference in the bricks made with added calcined diatomite sludge was the presence of cristobalite, a component of the sludge. It is interesting to observe that the newly-formed phases contain certain chemical elements that are not normally found in their standard chemical composition.

Phase Composition of the Core–Shell Transition Layer in a Construction Ceramic Matrix Structure Made from Non-Plastic Raw Material with Clay Additives

The process of forming, by means of a proposed technology, the transitional layer between a dispersed medium and a dispersed phase of a ceramic matrix composite is investigated and a method of fabricating multilayer samples modeling at the macro level the interface between phases in the direction matrix–core of the composite material is presented. A qualitative and semiquantitative analysis is presented of new phases which are products of an interaction, occuring during firing, of a core made from sludgy iron-ore wastes and a matrix made from clayey raw material.

Moroccan clay deposits: Physico-chemical properties in view of provenance studies on ancient ceramics

Features of clayey raw materials from most important traditional pottery centers in the vicinity of the main medieval sites in Morocco, and their fired products were investigated. Besides clay from the North of Morocco, the used raw material was illitic clays (10–100%) and smectite-rich clays (0–67%) with variable amount of kaolinite, quartz and feldspars. Chlorite was also present in a small amount. The main major oxides were Si2O, Al2O3 and CaO. The fired tests (800–1100 °C) displayed a decrease in open porosity of the sintered clay by raising the temperature, mainly from 1000 °C due to the inception of melting. This change was coupled with the change in mineralogical composition. New crystalline phases as Ca-silicates (diopside and gehlenite), hematite, spinel and mullite occurred during firing process, attesting to the inception of melting and were responsible for porosity reduction.Reference clays for pottery were established based on the clay mineralogy and chemical composition. The present study would help to answer some archeological questions concerning possible sourcing areas for archeological ceramics, to determine techniques for the production of artefacts, and then to interpret cultural influences. Furthermore, the obtained results will support the inception of development of a compositional database for Moroccan pottery.

Elaboration of ceramic material with sludge from the wastewater treatment plant of the tomato processing industry

The tomato processing industry generates huge quantities of sludge annually (1.5% of the tomato) which represents an environmental problem, especially in the large producing areas such as Extremadura in Spain. The substitution of clayey raw materials for other wastes, in this case tomato sewage sludge, in the production of traditional ceramics, could be cost-effective from the utilization and recycling of these wastes as a secondary raw material. Different quantities of sewage sludge from the tomato processing industry have been added to the body of the clay to produce ceramic materials. It has achieved a ceramic material with greater porosity to improve its thermal and acoustic insulation capacity.