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Ceramic properties of kaolinized tuffaceous rocks in Kesan region, Thrace, NW Turkey
Applied Clay Science 48 (2010) 499–505
Contents lists available at ScienceDirect
Applied Clay Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l a y
Ceramic properties of kaolinized tuffaceous rocks in Kesan region, Thrace, NW Turkey G. Yanık a,⁎, F. Esenli b, V. Uz c, V. Esenli b, B. Uz b, T. Külah a a b c
Dumlupinar University, Department of Geological Engineering, Kutahya, 43100, Turkey Istanbul Technical University, Department of Geological Engineering, Istanbul, 34469, Turkey Dumlupinar University, Department of Ceramic Engineering, Kutahya, 43100, Turkey
a r t i c l e
i n f o
Article history: Received 14 July 2009 Received in revised form 19 February 2010 Accepted 23 February 2010 Available online 2 March 2010 Keywords: Kaolinized tuff Ceramics NW Turkey
a b s t r a c t The Kesan–Karlikoy kaolin occurrence is located in the SW Thrace (Turkey) and was formed by the alteration of tuffaceous rocks. The tuff and tuffaceous units are made up of (1) bentonite, (2) kaolin and (3) zeolite (mordenite-rich), from bottom to top. The 20–40 m thick kaolin level is beige, yellowish and whitish beige in color and sandy tuff in appearance. The alteration of the rock to kaolin was explained by chemical, optical and scanning electron microscope (OM and SEM) and X-ray diffraction (XRD) studies. In terms of mineral constituents, the samples were generally rich in kaolinite and quartz, and some of them contained minor amounts of smectite, feldspar, opal-CT and calcite as well. The kaolinite contents estimated by XRD-modal analysis range between 20 and 55 mass % in the kaolin zone. Representative sample from the kaolin zone was used for ceramic tests. Flexure strength and Young modulus were measured and porosity, bulk density and water absorption were determined. For the samples fired at 1140 °C, the flexure strength was 9.78 MPa. The elasticity modulus was 7.94 GPa. Water absorption and apparent porosity values were 12.7% and 22.9%, respectively. Finally, the apparent density was 2.33 g/cm3. Plasticity values of kaolin samples were also determined according to the Pfefferkorn plasticity test. The kaolinized tuff can be used for wall tiles, floor tiles, and tableware which are shaped by dry pressing and extrusion. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Kaolin is one of the most valuable, versatile, and widely used industrial raw materials. Although it is particularly important for papermaking, kaolin is used in ceramics, rubber, paints, plastics, and pharmaceutics (Murray, 1991; Bundy, 1993). The main product after firing kaolin at high temperatures is mullite which is an important and widely studied ceramic material (Norton, 1978; Ghorbel et al., 2008). A rock is considered as kaolin when the amount of kaolinite is higher than 50% (Dombrowski, 2000). The physical and chemical properties of the kaolin determine its use as an industrial mineral. The use of kaolin and ball clay has been growing in recent years as a consequence of the increasing ceramics output worldwide. Besides, the ceramics industry has undergone a considerable technological innovation in recent decades, by the development of new types of ceramic products (Dondi, 2003; Fiederling-Kapteinat, 2005). Although such a huge demand for kaolin can be met at present; the sources are being consumed so rapidly that problems will inevitably arise. In case of the depletion of the natural sources, either new sources will have to be explored or the sources of poor quality will have to be rehabilitated since the factories operating in the sector cannot be closed down.
⁎ Corresponding author. Tel.: +90 274 265 2031 1484; fax: +90 274 265 20 66. E-mail address: [email protected] (G. Yanık). 0169-1317/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2010.02.014
The aim of this study is related to the procurement of kaolin for the ceramic industry in Turkey. Kaolinized tuffs in Kesan–Karlikoy (Edirne/Turkey) were characterized, and their suitability for ceramics production was investigated. The kaolinite is a secondary mineral in the tuffaceous rock, which is sandy in character. The large reserve of this material mainly consists of kaolinite and quartz. 2. Geology The regional geological setting of the Thrace basin was reported by Turgut et al. (1991), Sümengen and Terlemez (1991) and Siyako (2006). The Thrace basin (NW Turkey) was opened at the end of the Middle Eocene, and is surrounded by the Stradja, Rhodope and Menderes massifs in the north, northwest and south, respectively, and their thickness in the center reaches up to 8 km (Turgut et al., 1991). Thrace volcanics were classified petrographically and geochemically by Yılmaz and Polat (1998) as (1) Late Eocene–Early Miocene calc alkaline-intermediate volcanics and (2) Late Miocene–Pliocene alkaline basaltic lavas. The former has a mainly dacitic–andesitic composition and tuffaceous interbeds within sedimentary rocks or tuffaceous matrix of clastic rocks. Kesan Formation (Upper Eocene; Sümengen and Terlemez, 1991) is the lowest part of the stratigraphic succession in the studied area (Fig. 1). The upper part of this formation was named as “Ceylan Formation” by Siyako (2006). It was formed in a marine environment and consists of mainly turbiditic sandstones and rarely shales, marls,
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Fig. 1. The geographical and geological maps of the studied area (Karliköy-Mercan, Keşan).
tuff and tuffaceous rocks, as well. This formation, conformably overlain by the Lower–Middle Oligocene Mezardere Formation, was formed in lacustrine and shallow depositional environments and included mainly shale and marl (Siyako, 2006). Tuff and tuffaceous rocks repeatedly occurred in the lower part of this formation, as well. Ternek (1949) and Koop et al. (1969) reported Oligocene andesitic and dacitic lavas and tuffs in the Kesan region; moreover, Koop et al. (1969) also reported an approximately 20 m thick pyroclastic level named as “Kesan tuffs” between the Kesan and Mezardere Formations. The rock types in the study area (Karliköy-Mercan, SW Kesan, Thrace region, Fig. 1) include dacitic–andesitic pyroclastic and epiclastic components. Three types of alteration were observed in these rocks. The vertical variation is expressed as a transition from a
bentonite zone upwards through the kaolin zone and then zeolite zones at the top. Bentonite (smectite-rich) zone possesses a total thickness of 4–5 m at the bottom level of the pyroclastic-rich unit. The kaolin zone overlays the bentonite level, and its thickness ranges from 20 m to 40 m. Geological reserve of this zone (the area demonstrated as K symbol in Fig. 1) is about 8 million tonnes. Zeolite-rich pyroclastics at the top level are probably 20 m in thickness and show a lateral transition to non-altered pyroclastics throughout NW part of the study area. The bentonitic tuffs are whitish, pale greenish grey and soft in color. The Kaolin zone is comprised of sandy tuffs which is beige–yellowish beige. Finally, the zeolite-rich rock is typically pale green in appearance and vitric-crystal tuffs.
Table 1 Mineralogical compositions (by XRD, mass %). Zone (in Fig. 1)
Sample
S K K K K K K SK SK SK Z Z SK K K S S S
1 2 3 4 5 6 7 8 9 10 11 12 13 15 16 17 18 19
Minerals (mass %) Quartz
Kaolinite
Smectite
Feldspar
Opal -CT
Calcite
Mordenite
Dolomite
b5 40–45 35–40 40–45 10–15 30–35 25–30 15–20 15–20 25–30 10–15 10–15 10–15 35–40 35–40 b5 5–10 –
– 45–50 50–55 45–50 20–25 45–50 40–45 15–20 15–20 40–45 – – 15–20 50–55 50–55 – – –
75–80 5–10 5–10 5–10 45–50 10–15 5–10 30–35 40–45 10–15 –
b5 b5 b5 b5 5–10 5–10 5–10 15–20 5–10 10–15 15–20 15–20 5–10 b5 – b5 b5 5–10
5–10 – – – 10–15 – b5 b5 10–15 5–10 – – 10–15 – – 5–10 5–10 15–20
10–15 – – – – – 10–15 10–15 – 10–15 – – – – – 30–35 15–20 10–15
– – – – – – – – – – 65–70 65–70 – – – – – –
– – – – – – – – – – – – – – – b5 – –
45–50 5–10 5–10 50–55 60–65 60–65
G. Yanık et al. / Applied Clay Science 48 (2010) 499–505
Esenli et al. (2005) reported a zeolitic pyroclastic-rich zone with a 33 m total thickness in Kizkapani–Karahisar area, which is neighboring of Karliköy-Mercan area. Zeolitization was described as a production of an open-hydrological system in a geological environment of shallow
501
marine and lacustrine transition. Moreover, mordenite and analcime were identified as diagenetic zeolite minerals formed by the interaction between volcanic glass of the tuffs and water. However, alteration into bentonite or kaolin was not reported in that study.
Fig. 2. X-ray diffraction patterns of (a): bentonite (sample 1), (b): kaolin (sample 3) and (c): zeolite-rich (sample 11) samples.
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3. Materials and methods Twenty rock samples collected from the study area and a representative kaolin sample (mixture of the samples; 2, 3, 4, 15 and 16) were used for the analysis and tests. Mineralogical– petrographical determinations of the samples were made by using the polarizing microscope, scanning electron microscope and X-ray diffractometer. Samples were comminuted gently to 2 mm. Rock fragments were vibrated mechanically in water for 12 h to extract as many clay-size materials as possible. Afterwards, the remaining rock fragments and the coarse grains (approximately N63 µm) were removed by sedimentation and the suspension was ultrasonically dispersed. A Rigaku diffractometer with Cu (Kα) radiation was used for X-ray diffraction (XRD) analysis. Mineral contents were estimated by the quantitative XRD-modal analysis for the kaolin and bentonite samples and by image analysis method using an optical microscope for zeolite samples. The XRDmodal analysis was a modification of the reference intensity method described by Chung (1974, 1975) and Davis and Walawender (1982). Calcite was chosen as a standard mineral, and the highest reflections of the individual minerals and calcite were used. The intensity ratios of calcite/mineral of 50/50% were calculated for the reference intensity constants. The correction factors reported by Bulut et al. (2009) for some minerals were used. The kaolinite factor was obtained in this study using a pure Duvertepe (West Anatolia) kaolinite sample. The factors were calcite: 1.00, quartz: 0.48, albite: 1.39, orthoclase: 1.69, opal-CT: 2.11, dolomite: 1.11, smectite: 7.05 and kaolinite: 4.70. The major elements of the sample were determined by a Spectro X-Lab 2000 X-ray fluorescence (XRF) spectrometer using clay standards. Bulk clay samples ground to fine powder were mixed with lithium tetraborate for chemical analysis. The ignition loss was determined by calcination at 1000 °C. The morphological and chemical composition of the kaolin and fired samples were determined by a Zeiss Supra 50 VP Analytical Scanning Electron Microscope (SEM) and a Tracor Northern 5400 energy dispersive X-ray spectrometer (EDX). Plasticity values of the samples were determined according to the Pfefferkorn plasticity test (Uz, 2004). The samples were shaped to the dimensions of 10 × 10 × 0.6 mm by applying a pressure of 400 kg/cm2 with 5% moisture in the dry pressing process. The shaped samples were fired at 1140 °C for 70 min in a fast firing furnace. The Archimedes method was used for determining the water absorption (ISO 10545-3), bulk density, density and porosity values of the fired products. The strength values were measured (ISO 10545-4) by a Gabrielli three point bending instrument. The brightness and color values were determined using a Data Color spectrocolorimeter. 4. Results and discussion 4.1. Mineralogy–petrography In Fig. 1 tuffs and tuffaceous rocks were shown as smectite- (S), kaolinite- (K), zeolite-rich (Z), smectite/kaolinite (SK) and nonaltered (NA) facieses and also volcanics, which could not be differentiated (V) by the mineralogical determinations. Sample 14 was a sedimentary rock (marl) from Kesan Formation. Sample 20 was from the unaltered pyroclastics, which contained mainly fresh glassy shards. The main mineral of samples 1, 5, 8, 9, 13, 17, 18 and 19 was a smectite. The samples 11 and 12 were zeolite-rich samples while the rest (Nr. 2, 3, 4, 6, 7, 10, 15 and 16) were kaolinite-rich samples. Although it contained mainly smectite, sample 5 was included in kaolinite-rich facies because it had thin level, and there were a few kinds of smectite-rich levels in the vertical scale of kaolinitic facies. The mineralogical compositions of the samples determined by XRD analysis were given in Table 1. As examples, the XRD patterns of
Fig. 3. Crossed polarized optical microscope views of the kaolinized tuffs. Less amounts of fine-grained sample (a), high amounts of fine- and coarse-grained samples (b and c), kaolinized matrix (d).
G. Yanık et al. / Applied Clay Science 48 (2010) 499–505
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Fig. 4. XRD patterns of kaolinized tuff fired at 1140 °C.
the smectite-rich sample 1, kaolinite-rich sample 3 and mordeniterich sample 11were given in Fig. 2. The mineral in the bentonitic zone could be a dioctahedral Ca-smectite. XRD patterns indicated a basal spacing of about 15 Å (15.22 Å in Fig. 2a) and d060 value of about 1.50 Å (1.497 Å in Fig. 2a). The most important 001 and 002 reflections of kaolinite corresponded to about 7.1 Å and 3.57 Å (Fig. 2b). Finally, it was determined that zeolitic tuffs contained mordenite, oligoclase and quartz. Mordenite showed three intensive reflections at d = 9.1 Å, 4.52 Å and 3.47 Å (Fig. 2c). Kaolinitic sandy tuffs were consisted of coarse- and fine-grained phenocrysts (mainly quartz, rarely oligoclase and orthoclase types of feldspar and muscovite), lithic fragments (generally volcanic rocks and sandstone) and very fine-grained matrix. The total content of phenocrysts + lithic fragments ranged from 20 to 50% by vol. The primary groundmass was transformed mainly into kaolinite and in lesser amounts to smectite, quartz and opal-cristobalite/trydimite (opal-CT) and was also altered to iron oxide. The ratio of phenocrysts/ matrix was approximately 40/60% as an average of the studied kaolin samples. Some samples contained small amounts of crystal/mineral grains (Fig. 3a), but there were high amounts of grains in the other samples (Fig. 3b). On the other hand, grains could be finer (Fig. 3b) or coarser (Fig. 3c). The groundmass was largely kaolinitic in the form of regular micro-aggregates (Fig. 3d). Fig. 4a (SEM images) showed kaolinite books of varying sizes with low aspect (crystal-width to thickness) ratios. Individual particles were noticeable. Some pseudo-hexagonal edges were observed. Some of the kaolinite particles had rough edges. The surface of the kaolinite flakes revealed that smaller particles b2 µ. The particles of the kaolinite in Kesan kaolinized tuff were mostly below 3 µ in size, forming books and individual flakes. Some of them presented pseudohexagonal shapes, but the others were irregular; both were very thin (Fig. 4a).
Table 2 Chemical composition of the representative (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16), by XRF. Composition
mass %
SiO2 Al2O3 TiO2 Fe2O3 CaO MgO Na2O K2O Loss of ignition Total
76.68 14.22 0.35 0.96 0.17 0.21 0.40 2.12 4.89 100.00
4.2. Ceramic characterization The kaolinite-rich zone (samples 2, 3, 4, 6, 10, 15 and 16) was the most significant geological level among the above-mentioned three zones for ceramic industry. Therefore, the technological tests were performed with this material. The major element composition of the representative sample (Table 2) was characterized by high amounts of SiO2 and low amounts of Al2O3. The presence of feldspar and smectite was explained by the high content of alkali cations (K2O + Na2O: 2.52%). Iron occurred in the form of hydrated oxides and secondary iron minerals formed in the course of weathering and kaolinization. Color features (L*-value) of the fired ceramic bodies was as important as the other features (physico-mechanical, mineralogical, chemical, etc.). There were many studies on this subject in the literature. In these studies, the L*-value (lightness) of the fired ceramic bodies and kaolins were determined, and their possible uses in ceramic production were determined that L*- value changed between 53and 85 after the clays were fired at 1000 °C. Therefore, they suggested that the clays used in their study were suitable for wall tile production. In the study of Das and Dana (2003), L*-value of the ceramic bodies was reported as 76 when fired at 1160 °C. Kara et al. (2006) also determined L*-value of some ceramic bodies L*-value was 56 for floor tiles fired at 1200 °C, and 62.2 for the multipurpose floor tiles. In addition, it was 78.4 and 74.7 for the wall tiles fired at 1170 °C and for the multipurpose wall tiles, respectively. The Fe2O3 (0.96%) and TiO2 (0.35%) contents in Kesan kaolinized tuffs were rather low, which increased the whiteness of the fired samples (L*-value = 77.66 fired at 1140 °C). When compared to the values reported in the above-mentioned studies. They could be used in white-fired ceramics.
Table 3 Some physical properties of the representative sample (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16). Technological property
Unit
Values
Plasticity, according to Pfefferkorn 24 mm Dry bend strength Total shrinkage Flexure strength Elasticity modulus Water absorption Open porosity Bulk density Color properties of fired sample
mass % MPa % MPa GPa mass % vol.% g/cm3 L a b
20.21 1.30 ± 0.05 0.80 9.78 ± 1.02 7.94 ± 0.90 12.7 22.86 2.33 77.66 − 0.19 8.41
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SEM images of the representative sample fired for 70 min at 1140 °C revealed the particles of submicrometre size (Fig. 4b). Primary mullite (type I) had a particle size of b0.5 µm (length)
(Fig. 4b). Secondary mullite (type II) was also detected in the form of particles with elongated shape (6–7 µm long and 0.5 µm wide). A few needle-like mullite crystals (type III) were observed. The types of
Fig. 5. a. SEM photograph showing books and stacks of kaolinite. b. SEM photograph of fired kaolinite showing primary mullite (type I), secondary mullite type I (rod-shaped) and type III (needle-like) crystals.
G. Yanık et al. / Applied Clay Science 48 (2010) 499–505
mullite formed were recently reviewed by Lee and Iqbal (2001) and Lee et al. (2008). XRD analysis of the fired kaolinized tuffs (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16) indicated the “mullite + cristobalite + quartz + glass” phase. The X-ray diffractograms of the kaolin after fast firing (70 min) at 1140 °C were presented in Fig. 5 showing the XRD reflections of cristobalite (JCPDS pattern no. 11-0695), quartz (JCPDS pattern no. 46-1045) and mullite (JCPDS pattern no. 15-776) as main crystalline phases. In addition, an amorph phase was indicated by the enhanced background. After heating to 1140 °C both cristobalite and quartz were present after together with formed mullite, residual quartz and glass. The presence of mullite in the Kesan kaolin contributed to the mechanical strength. Complete wetting of the crystalline phases, absence of cracks due to the different volume expansion of the crystalline phase and the glassy matrix were favorable for strength development. The flexure strength of the samples fired at 1140 °C was 9.78 MPa, the elasticity modulus was 7.94 GPa (Table 3). Water absorption and apparent porosity values were 12.7% and 22.9%, the apparent density was 2.33 g/cm3. The increase of the density was attributed to the elimination of pores during sintering. High density and the changes in the microstructure increased the resistance of the ceramic materials but reduced the water absorption and the porosity. Thus, the kaolinized tuff may be use in the production of wall tile, floor tile and tableware production (Dondi et al., 2001). The Pfefferkorn plasticity of 20.2% indicated that the kaolin could be used ceramic products shaped through extrusion. The slurry of kaolinized tuff cannot be used in molding. 5. Conclusion A Tuffaceous rock from Kesan–Karlikoy contained high amounts of kaolinite was found highly kaolinitic the kaolinite was formed by alteration of the groundmass of the rock. This pyroclastic-rich unit underwent smectite, kaolinite and zeolite alterations during different periods of various physical and chemical conditions. In the average the kaolinitic facies are composed of 50 mass % kaolinite, 30 mass % quartz and small amounts of smectite, feldspar, opal-CT and calcite. The geological reserves of this material are about 8 million tonnes. The kaolinized tuff can be used for wall tile, floor tile, and tableware production by dry pressing and extrusion . Since this material does not possess appropriate molding properties, it is not suitable for ceramics products, which are shaped by molding. References Bulut, G., Chimmeddorj, M., Esenli, F., Çelik, M.S., 2009. Production of desiccants from Turkish bentonites. Applied Clay Science 46, 141–147. Bundy, W.M., 1993. The diverse industrial applications of kaolin. In: Murray, H.H., et al. (Ed.), Chapter in Kaolin Genesis and Utilization, Special Publ. No. 1. The Clay Minerals Society, pp. 43–73.
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Chung, F.H., 1974. Quantitative interpretation of X-ray diffraction patterns of mixture I: matrix-flushing method for quantitative multi-component analysis. Journal of Applied Crystallography 7, 519–525. Chung, F.H., 1975. Quantitative interpretation of X-ray diffraction patterns of mixture III: simultaneous determination of a set of reference intensities. Journal of Applied Crystallography 8, 17–19. Das, S.K., Dana, K., 2003. Differences in densification behaviour of K- and Na-feldsparcontaining porcelain bodies. Thermochimica Acta 406, 199–206. Davis, B.L., Walawender, M.J., 1982. Quantitative mineralogical analysis of granitoid rocks: a comparison of X-ray and optical techniques. American Mineralogist 67, 1135–1143. Dombrowski, T., 2000. The origin of kaolinite. Implication for utilization. In: Carty, W.M., Sinton, C.W. (Eds.), Science of White Wares II. American Ceramic Society, Westerville, OH, pp. 3–12. Dondi, M., 2003. Technological and compositional requirements of clay materials for ceramic tiles. In: Domínguez, E.A., Mas, G.R., Cravero, F. (Eds.), Proceedings of the 12th International Clay Conference , Bahía Blanca, Argentina, July 22–28, 2001. Elsevier, pp. 23–30. Dondi, M., Guarini, G., Ligas, P., Palomba, M., Raimondo, M., 2001. Chemical, mineralogical and ceramic properties of kaolinitic materials from the Tresnuraghes mining district (Western Sardinia, Italy). Applied Clay Science 18, 145–155. Esenli, F., Uz, B., Suner, F., Esenli, V., Ece, Ö.I., Kumbasar, I., 2005. Zeolitization of tuffaceous rocks in the Kesan region, Thrace, Turkey. Geologia Croatica 58 (2), 151–161. Fiederling-Kapteinat, H.G., 2005. The Ukrainian clay mining industry and its effect on the European ceramic raw materials market. Interceram 54, 4–9. Ghorbel, A., Fourati, M., Bouaziz, J., 2008. Microstructural evolution and phase transformation of different sintered Kaolins powder compacts. Materials Chemistry and Physics 112, 876–885. Kara, A., Özer, F., Kayacı, K., Özer, P., 2006. Development of a multipurpose tile body: phase and microstructural development. Journal of the European Ceramic Society 26, 3769–3782. Koop, K.O., Pavoni, N., Schindler, C., 1969. Geologie Thrakiens. Das Ergene Becken. Beihefte zum Geologischen Jahrbuch 76 171 pp. Lee, W.E., Iqbal, Y., 2001. Influence of mixing on mullite formation in porcelain. Journal of the European Ceramic Society 21, 2583–2586. Lee, W.E., Souza, G.P., McConville, C.J., Tarvornpanich, T., Iqbal, Y., 2008. Mullite formation in clays and clay-derived vitreous ceramics. Journal of the European Ceramic Society 28, 465–471. Murray, H.H., 1991. Overview—clay mineral applications. Applied Clay Science 5, 379–395. Norton, F.H., 1978. Fine Ceramics, Technology and Applications. Robert E. Krieger, USA, p. 142. Siyako, M., 2006. Lignite-bearing sandstones of the Thrace Basin. Mineral Research & Exploration Bulletin 132, 63–73 (in Turkish). Sümengen, M., Terlemez, I., 1991. Stratigraphy of the Eocene deposits surrounding southwest Thrace. Mineral Research & Exploration Bulletin 113, 17–30 (in Turkish). Ternek, Z., 1949. The geology of Keşan–Korudağ region, PhD thesis, İstanbul University, İstanbul, 78 pp. Turgut, S., Türkaslan, M., Perinçek, D., 1991. Evolution of the Thrace sedimentary basin and its hydrocarbon prospectivity. European Assoc. Petroleum Geoscientists Spec. Publ., 1, pp. 415–437. Uz, V., 2004. The Effect on Ceramic Properties of Clays By the Inorganic, Organic and Biologic Based Additives, Ph. D. Thesis, Osmangazi University, 506 pp. (in Turkish). Yılmaz, Y., Polat, A., 1998. Geology and evolution of the Thrace volcanism, Turkey. Acta Vulcanologica 10, 293–303.
Contents lists available at ScienceDirect
Applied Clay Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c l a y
Ceramic properties of kaolinized tuffaceous rocks in Kesan region, Thrace, NW Turkey G. Yanık a,⁎, F. Esenli b, V. Uz c, V. Esenli b, B. Uz b, T. Külah a a b c
Dumlupinar University, Department of Geological Engineering, Kutahya, 43100, Turkey Istanbul Technical University, Department of Geological Engineering, Istanbul, 34469, Turkey Dumlupinar University, Department of Ceramic Engineering, Kutahya, 43100, Turkey
a r t i c l e
i n f o
Article history: Received 14 July 2009 Received in revised form 19 February 2010 Accepted 23 February 2010 Available online 2 March 2010 Keywords: Kaolinized tuff Ceramics NW Turkey
a b s t r a c t The Kesan–Karlikoy kaolin occurrence is located in the SW Thrace (Turkey) and was formed by the alteration of tuffaceous rocks. The tuff and tuffaceous units are made up of (1) bentonite, (2) kaolin and (3) zeolite (mordenite-rich), from bottom to top. The 20–40 m thick kaolin level is beige, yellowish and whitish beige in color and sandy tuff in appearance. The alteration of the rock to kaolin was explained by chemical, optical and scanning electron microscope (OM and SEM) and X-ray diffraction (XRD) studies. In terms of mineral constituents, the samples were generally rich in kaolinite and quartz, and some of them contained minor amounts of smectite, feldspar, opal-CT and calcite as well. The kaolinite contents estimated by XRD-modal analysis range between 20 and 55 mass % in the kaolin zone. Representative sample from the kaolin zone was used for ceramic tests. Flexure strength and Young modulus were measured and porosity, bulk density and water absorption were determined. For the samples fired at 1140 °C, the flexure strength was 9.78 MPa. The elasticity modulus was 7.94 GPa. Water absorption and apparent porosity values were 12.7% and 22.9%, respectively. Finally, the apparent density was 2.33 g/cm3. Plasticity values of kaolin samples were also determined according to the Pfefferkorn plasticity test. The kaolinized tuff can be used for wall tiles, floor tiles, and tableware which are shaped by dry pressing and extrusion. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Kaolin is one of the most valuable, versatile, and widely used industrial raw materials. Although it is particularly important for papermaking, kaolin is used in ceramics, rubber, paints, plastics, and pharmaceutics (Murray, 1991; Bundy, 1993). The main product after firing kaolin at high temperatures is mullite which is an important and widely studied ceramic material (Norton, 1978; Ghorbel et al., 2008). A rock is considered as kaolin when the amount of kaolinite is higher than 50% (Dombrowski, 2000). The physical and chemical properties of the kaolin determine its use as an industrial mineral. The use of kaolin and ball clay has been growing in recent years as a consequence of the increasing ceramics output worldwide. Besides, the ceramics industry has undergone a considerable technological innovation in recent decades, by the development of new types of ceramic products (Dondi, 2003; Fiederling-Kapteinat, 2005). Although such a huge demand for kaolin can be met at present; the sources are being consumed so rapidly that problems will inevitably arise. In case of the depletion of the natural sources, either new sources will have to be explored or the sources of poor quality will have to be rehabilitated since the factories operating in the sector cannot be closed down.
⁎ Corresponding author. Tel.: +90 274 265 2031 1484; fax: +90 274 265 20 66. E-mail address: [email protected] (G. Yanık). 0169-1317/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.clay.2010.02.014
The aim of this study is related to the procurement of kaolin for the ceramic industry in Turkey. Kaolinized tuffs in Kesan–Karlikoy (Edirne/Turkey) were characterized, and their suitability for ceramics production was investigated. The kaolinite is a secondary mineral in the tuffaceous rock, which is sandy in character. The large reserve of this material mainly consists of kaolinite and quartz. 2. Geology The regional geological setting of the Thrace basin was reported by Turgut et al. (1991), Sümengen and Terlemez (1991) and Siyako (2006). The Thrace basin (NW Turkey) was opened at the end of the Middle Eocene, and is surrounded by the Stradja, Rhodope and Menderes massifs in the north, northwest and south, respectively, and their thickness in the center reaches up to 8 km (Turgut et al., 1991). Thrace volcanics were classified petrographically and geochemically by Yılmaz and Polat (1998) as (1) Late Eocene–Early Miocene calc alkaline-intermediate volcanics and (2) Late Miocene–Pliocene alkaline basaltic lavas. The former has a mainly dacitic–andesitic composition and tuffaceous interbeds within sedimentary rocks or tuffaceous matrix of clastic rocks. Kesan Formation (Upper Eocene; Sümengen and Terlemez, 1991) is the lowest part of the stratigraphic succession in the studied area (Fig. 1). The upper part of this formation was named as “Ceylan Formation” by Siyako (2006). It was formed in a marine environment and consists of mainly turbiditic sandstones and rarely shales, marls,
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Fig. 1. The geographical and geological maps of the studied area (Karliköy-Mercan, Keşan).
tuff and tuffaceous rocks, as well. This formation, conformably overlain by the Lower–Middle Oligocene Mezardere Formation, was formed in lacustrine and shallow depositional environments and included mainly shale and marl (Siyako, 2006). Tuff and tuffaceous rocks repeatedly occurred in the lower part of this formation, as well. Ternek (1949) and Koop et al. (1969) reported Oligocene andesitic and dacitic lavas and tuffs in the Kesan region; moreover, Koop et al. (1969) also reported an approximately 20 m thick pyroclastic level named as “Kesan tuffs” between the Kesan and Mezardere Formations. The rock types in the study area (Karliköy-Mercan, SW Kesan, Thrace region, Fig. 1) include dacitic–andesitic pyroclastic and epiclastic components. Three types of alteration were observed in these rocks. The vertical variation is expressed as a transition from a
bentonite zone upwards through the kaolin zone and then zeolite zones at the top. Bentonite (smectite-rich) zone possesses a total thickness of 4–5 m at the bottom level of the pyroclastic-rich unit. The kaolin zone overlays the bentonite level, and its thickness ranges from 20 m to 40 m. Geological reserve of this zone (the area demonstrated as K symbol in Fig. 1) is about 8 million tonnes. Zeolite-rich pyroclastics at the top level are probably 20 m in thickness and show a lateral transition to non-altered pyroclastics throughout NW part of the study area. The bentonitic tuffs are whitish, pale greenish grey and soft in color. The Kaolin zone is comprised of sandy tuffs which is beige–yellowish beige. Finally, the zeolite-rich rock is typically pale green in appearance and vitric-crystal tuffs.
Table 1 Mineralogical compositions (by XRD, mass %). Zone (in Fig. 1)
Sample
S K K K K K K SK SK SK Z Z SK K K S S S
1 2 3 4 5 6 7 8 9 10 11 12 13 15 16 17 18 19
Minerals (mass %) Quartz
Kaolinite
Smectite
Feldspar
Opal -CT
Calcite
Mordenite
Dolomite
b5 40–45 35–40 40–45 10–15 30–35 25–30 15–20 15–20 25–30 10–15 10–15 10–15 35–40 35–40 b5 5–10 –
– 45–50 50–55 45–50 20–25 45–50 40–45 15–20 15–20 40–45 – – 15–20 50–55 50–55 – – –
75–80 5–10 5–10 5–10 45–50 10–15 5–10 30–35 40–45 10–15 –
b5 b5 b5 b5 5–10 5–10 5–10 15–20 5–10 10–15 15–20 15–20 5–10 b5 – b5 b5 5–10
5–10 – – – 10–15 – b5 b5 10–15 5–10 – – 10–15 – – 5–10 5–10 15–20
10–15 – – – – – 10–15 10–15 – 10–15 – – – – – 30–35 15–20 10–15
– – – – – – – – – – 65–70 65–70 – – – – – –
– – – – – – – – – – – – – – – b5 – –
45–50 5–10 5–10 50–55 60–65 60–65
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Esenli et al. (2005) reported a zeolitic pyroclastic-rich zone with a 33 m total thickness in Kizkapani–Karahisar area, which is neighboring of Karliköy-Mercan area. Zeolitization was described as a production of an open-hydrological system in a geological environment of shallow
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marine and lacustrine transition. Moreover, mordenite and analcime were identified as diagenetic zeolite minerals formed by the interaction between volcanic glass of the tuffs and water. However, alteration into bentonite or kaolin was not reported in that study.
Fig. 2. X-ray diffraction patterns of (a): bentonite (sample 1), (b): kaolin (sample 3) and (c): zeolite-rich (sample 11) samples.
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3. Materials and methods Twenty rock samples collected from the study area and a representative kaolin sample (mixture of the samples; 2, 3, 4, 15 and 16) were used for the analysis and tests. Mineralogical– petrographical determinations of the samples were made by using the polarizing microscope, scanning electron microscope and X-ray diffractometer. Samples were comminuted gently to 2 mm. Rock fragments were vibrated mechanically in water for 12 h to extract as many clay-size materials as possible. Afterwards, the remaining rock fragments and the coarse grains (approximately N63 µm) were removed by sedimentation and the suspension was ultrasonically dispersed. A Rigaku diffractometer with Cu (Kα) radiation was used for X-ray diffraction (XRD) analysis. Mineral contents were estimated by the quantitative XRD-modal analysis for the kaolin and bentonite samples and by image analysis method using an optical microscope for zeolite samples. The XRDmodal analysis was a modification of the reference intensity method described by Chung (1974, 1975) and Davis and Walawender (1982). Calcite was chosen as a standard mineral, and the highest reflections of the individual minerals and calcite were used. The intensity ratios of calcite/mineral of 50/50% were calculated for the reference intensity constants. The correction factors reported by Bulut et al. (2009) for some minerals were used. The kaolinite factor was obtained in this study using a pure Duvertepe (West Anatolia) kaolinite sample. The factors were calcite: 1.00, quartz: 0.48, albite: 1.39, orthoclase: 1.69, opal-CT: 2.11, dolomite: 1.11, smectite: 7.05 and kaolinite: 4.70. The major elements of the sample were determined by a Spectro X-Lab 2000 X-ray fluorescence (XRF) spectrometer using clay standards. Bulk clay samples ground to fine powder were mixed with lithium tetraborate for chemical analysis. The ignition loss was determined by calcination at 1000 °C. The morphological and chemical composition of the kaolin and fired samples were determined by a Zeiss Supra 50 VP Analytical Scanning Electron Microscope (SEM) and a Tracor Northern 5400 energy dispersive X-ray spectrometer (EDX). Plasticity values of the samples were determined according to the Pfefferkorn plasticity test (Uz, 2004). The samples were shaped to the dimensions of 10 × 10 × 0.6 mm by applying a pressure of 400 kg/cm2 with 5% moisture in the dry pressing process. The shaped samples were fired at 1140 °C for 70 min in a fast firing furnace. The Archimedes method was used for determining the water absorption (ISO 10545-3), bulk density, density and porosity values of the fired products. The strength values were measured (ISO 10545-4) by a Gabrielli three point bending instrument. The brightness and color values were determined using a Data Color spectrocolorimeter. 4. Results and discussion 4.1. Mineralogy–petrography In Fig. 1 tuffs and tuffaceous rocks were shown as smectite- (S), kaolinite- (K), zeolite-rich (Z), smectite/kaolinite (SK) and nonaltered (NA) facieses and also volcanics, which could not be differentiated (V) by the mineralogical determinations. Sample 14 was a sedimentary rock (marl) from Kesan Formation. Sample 20 was from the unaltered pyroclastics, which contained mainly fresh glassy shards. The main mineral of samples 1, 5, 8, 9, 13, 17, 18 and 19 was a smectite. The samples 11 and 12 were zeolite-rich samples while the rest (Nr. 2, 3, 4, 6, 7, 10, 15 and 16) were kaolinite-rich samples. Although it contained mainly smectite, sample 5 was included in kaolinite-rich facies because it had thin level, and there were a few kinds of smectite-rich levels in the vertical scale of kaolinitic facies. The mineralogical compositions of the samples determined by XRD analysis were given in Table 1. As examples, the XRD patterns of
Fig. 3. Crossed polarized optical microscope views of the kaolinized tuffs. Less amounts of fine-grained sample (a), high amounts of fine- and coarse-grained samples (b and c), kaolinized matrix (d).
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Fig. 4. XRD patterns of kaolinized tuff fired at 1140 °C.
the smectite-rich sample 1, kaolinite-rich sample 3 and mordeniterich sample 11were given in Fig. 2. The mineral in the bentonitic zone could be a dioctahedral Ca-smectite. XRD patterns indicated a basal spacing of about 15 Å (15.22 Å in Fig. 2a) and d060 value of about 1.50 Å (1.497 Å in Fig. 2a). The most important 001 and 002 reflections of kaolinite corresponded to about 7.1 Å and 3.57 Å (Fig. 2b). Finally, it was determined that zeolitic tuffs contained mordenite, oligoclase and quartz. Mordenite showed three intensive reflections at d = 9.1 Å, 4.52 Å and 3.47 Å (Fig. 2c). Kaolinitic sandy tuffs were consisted of coarse- and fine-grained phenocrysts (mainly quartz, rarely oligoclase and orthoclase types of feldspar and muscovite), lithic fragments (generally volcanic rocks and sandstone) and very fine-grained matrix. The total content of phenocrysts + lithic fragments ranged from 20 to 50% by vol. The primary groundmass was transformed mainly into kaolinite and in lesser amounts to smectite, quartz and opal-cristobalite/trydimite (opal-CT) and was also altered to iron oxide. The ratio of phenocrysts/ matrix was approximately 40/60% as an average of the studied kaolin samples. Some samples contained small amounts of crystal/mineral grains (Fig. 3a), but there were high amounts of grains in the other samples (Fig. 3b). On the other hand, grains could be finer (Fig. 3b) or coarser (Fig. 3c). The groundmass was largely kaolinitic in the form of regular micro-aggregates (Fig. 3d). Fig. 4a (SEM images) showed kaolinite books of varying sizes with low aspect (crystal-width to thickness) ratios. Individual particles were noticeable. Some pseudo-hexagonal edges were observed. Some of the kaolinite particles had rough edges. The surface of the kaolinite flakes revealed that smaller particles b2 µ. The particles of the kaolinite in Kesan kaolinized tuff were mostly below 3 µ in size, forming books and individual flakes. Some of them presented pseudohexagonal shapes, but the others were irregular; both were very thin (Fig. 4a).
Table 2 Chemical composition of the representative (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16), by XRF. Composition
mass %
SiO2 Al2O3 TiO2 Fe2O3 CaO MgO Na2O K2O Loss of ignition Total
76.68 14.22 0.35 0.96 0.17 0.21 0.40 2.12 4.89 100.00
4.2. Ceramic characterization The kaolinite-rich zone (samples 2, 3, 4, 6, 10, 15 and 16) was the most significant geological level among the above-mentioned three zones for ceramic industry. Therefore, the technological tests were performed with this material. The major element composition of the representative sample (Table 2) was characterized by high amounts of SiO2 and low amounts of Al2O3. The presence of feldspar and smectite was explained by the high content of alkali cations (K2O + Na2O: 2.52%). Iron occurred in the form of hydrated oxides and secondary iron minerals formed in the course of weathering and kaolinization. Color features (L*-value) of the fired ceramic bodies was as important as the other features (physico-mechanical, mineralogical, chemical, etc.). There were many studies on this subject in the literature. In these studies, the L*-value (lightness) of the fired ceramic bodies and kaolins were determined, and their possible uses in ceramic production were determined that L*- value changed between 53and 85 after the clays were fired at 1000 °C. Therefore, they suggested that the clays used in their study were suitable for wall tile production. In the study of Das and Dana (2003), L*-value of the ceramic bodies was reported as 76 when fired at 1160 °C. Kara et al. (2006) also determined L*-value of some ceramic bodies L*-value was 56 for floor tiles fired at 1200 °C, and 62.2 for the multipurpose floor tiles. In addition, it was 78.4 and 74.7 for the wall tiles fired at 1170 °C and for the multipurpose wall tiles, respectively. The Fe2O3 (0.96%) and TiO2 (0.35%) contents in Kesan kaolinized tuffs were rather low, which increased the whiteness of the fired samples (L*-value = 77.66 fired at 1140 °C). When compared to the values reported in the above-mentioned studies. They could be used in white-fired ceramics.
Table 3 Some physical properties of the representative sample (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16). Technological property
Unit
Values
Plasticity, according to Pfefferkorn 24 mm Dry bend strength Total shrinkage Flexure strength Elasticity modulus Water absorption Open porosity Bulk density Color properties of fired sample
mass % MPa % MPa GPa mass % vol.% g/cm3 L a b
20.21 1.30 ± 0.05 0.80 9.78 ± 1.02 7.94 ± 0.90 12.7 22.86 2.33 77.66 − 0.19 8.41
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SEM images of the representative sample fired for 70 min at 1140 °C revealed the particles of submicrometre size (Fig. 4b). Primary mullite (type I) had a particle size of b0.5 µm (length)
(Fig. 4b). Secondary mullite (type II) was also detected in the form of particles with elongated shape (6–7 µm long and 0.5 µm wide). A few needle-like mullite crystals (type III) were observed. The types of
Fig. 5. a. SEM photograph showing books and stacks of kaolinite. b. SEM photograph of fired kaolinite showing primary mullite (type I), secondary mullite type I (rod-shaped) and type III (needle-like) crystals.
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mullite formed were recently reviewed by Lee and Iqbal (2001) and Lee et al. (2008). XRD analysis of the fired kaolinized tuffs (mixture of the samples; 2, 3, 4, 6, 10, 15 and 16) indicated the “mullite + cristobalite + quartz + glass” phase. The X-ray diffractograms of the kaolin after fast firing (70 min) at 1140 °C were presented in Fig. 5 showing the XRD reflections of cristobalite (JCPDS pattern no. 11-0695), quartz (JCPDS pattern no. 46-1045) and mullite (JCPDS pattern no. 15-776) as main crystalline phases. In addition, an amorph phase was indicated by the enhanced background. After heating to 1140 °C both cristobalite and quartz were present after together with formed mullite, residual quartz and glass. The presence of mullite in the Kesan kaolin contributed to the mechanical strength. Complete wetting of the crystalline phases, absence of cracks due to the different volume expansion of the crystalline phase and the glassy matrix were favorable for strength development. The flexure strength of the samples fired at 1140 °C was 9.78 MPa, the elasticity modulus was 7.94 GPa (Table 3). Water absorption and apparent porosity values were 12.7% and 22.9%, the apparent density was 2.33 g/cm3. The increase of the density was attributed to the elimination of pores during sintering. High density and the changes in the microstructure increased the resistance of the ceramic materials but reduced the water absorption and the porosity. Thus, the kaolinized tuff may be use in the production of wall tile, floor tile and tableware production (Dondi et al., 2001). The Pfefferkorn plasticity of 20.2% indicated that the kaolin could be used ceramic products shaped through extrusion. The slurry of kaolinized tuff cannot be used in molding. 5. Conclusion A Tuffaceous rock from Kesan–Karlikoy contained high amounts of kaolinite was found highly kaolinitic the kaolinite was formed by alteration of the groundmass of the rock. This pyroclastic-rich unit underwent smectite, kaolinite and zeolite alterations during different periods of various physical and chemical conditions. In the average the kaolinitic facies are composed of 50 mass % kaolinite, 30 mass % quartz and small amounts of smectite, feldspar, opal-CT and calcite. The geological reserves of this material are about 8 million tonnes. The kaolinized tuff can be used for wall tile, floor tile, and tableware production by dry pressing and extrusion . Since this material does not possess appropriate molding properties, it is not suitable for ceramics products, which are shaped by molding. References Bulut, G., Chimmeddorj, M., Esenli, F., Çelik, M.S., 2009. Production of desiccants from Turkish bentonites. Applied Clay Science 46, 141–147. Bundy, W.M., 1993. The diverse industrial applications of kaolin. In: Murray, H.H., et al. (Ed.), Chapter in Kaolin Genesis and Utilization, Special Publ. No. 1. The Clay Minerals Society, pp. 43–73.
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