SCHOOL OF MATERIALS AND MINERAL RESOURCES ENGINEERING UNIVERSITI SAINS MALAYSIA
SUITABILITY OF BALL CLAY FROM MUKAH, PALOH AND CHAMEK TO BE USED IN THE PORCELAIN TILE INDUSTRY IN MALAYSIA BY JOANNA ANUSHA A/P DARMARAJAH
Supervisor: Assoc Prof. Dr. Hasmaliza bt Mohamad Co-Supervisor: Mr Chin Chee Lung
Dissertation submitted in partial fulfillment of the requirements for the Degree of Bachelor of Engineering with Honors (Materials Engineering)
Universiti Sains Malaysia
JUNE 2016
DECLARATION
I hereby declare that I have conducted and completed the research work and written the dissertation entitled “Suitability Of Ball Clay From Mukah, Paloh And Chamek To Be Used In The Porcelain Tile Industry in Malaysia”. I also declare that this has not been previously submitted for the award for any degree or diploma or other similar titles of this for any other examining body or University.
Name of Student: Joanna Anusha a/p Darmarajah Signature:
Date:
Witnessed by:
Supervisor: Assoc. Prof. Dr. Hasmaliza binti Mohamad Signature:
Date:
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ACKNOWLEDGEMENT
First and foremost, I give all thanks and praise to God for His goodness and faithfulness. I thank Him for granting me the wisdom and perseverance needed to carry out this study. It is truly only by His grace, favor and mercy that this final year project was completed successfully.
I would also like to express my deepest appreciation and gratitude to my FYP supervisor, Assoc Prof. Dr. Hasmaliza bt Mohamad for her continued support, encouragement and guidance throughout the course of this project. The concern and level of detail she has shown in guiding me is extremely humbling, and for that I am thankful. I am honoured to have had the chance to carry out my FYP under her supervision.
Special thanks and appreciation goes out to the manager at CRC, Mr Sow for giving me the opportunity to carry out my project in collaboration with Guocera. Not forgetting also my FYP co-supervisor, Mr Chin Chee Lung, the Manager of the Quality at
Source (QAS) department at the Ceramic Research Company (CRC) in Kapar, Klang.
Many thanks are due for his guidance and helpful suggestions that have allowed this project to take shape. He has helped me increase my knowledge on the procedures that need to be carried out in the clay selection process. I would also like to thank the other
CRC managers and technicians who have shared their knowledge with me and offered their assistance to me throughout the course of this project. They have played a very important part in the completion and success of this project. Not forgetting also the technicians at USM who have helped me greatly.
Last but not least, I wish to thank my beloved family and friends who have supported me and motivated me. Without their persistent prayers and unconditional love, this project would not have reached completion. Thank you all.
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TABLE OF CONTENTS
DECLARATION ii ACKNOWLEDGEMENTS iii TABLE OF CONTENTS iv LIST OF TABLES vii LIST OF FIGURES x LIST OF ABBREVIATIONS xi ABSTRACT xii ABSTRAK xiii
CHAPTER 1 1 INTRODUCTION 1 1.1 Clays 1 1.1.2 Clay Mining in Malaysia 1 1.1.3 The tile manufacturing scenario in Malaysia 2 1.1.4 Research Background 3 1.2 Problem Statement 4 1.3 Objectives 5 1.4 Scope of Study 5 1.5 Thesis Outline 6 CHAPTER 2 7 LITERATURE REVIEW 7 2.1 Introduction 7 2.2 Clays 7 2.2.1 Formation of clays 8 2.3 Types of clays 11 2.3.1 Ball Clays 12 2.3.2 Structure present in clay raw materials 13 2.3.2.1 Kaolinites 15 2.3.2.2 Illites 18 2.3.2.3 Smectites 20 2.4 Silica Sand 22 2.5 Clay Mines in Malaysia 23
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2.5.1 Batang Berjuntai 29 2.5.2 Paloh and Chamek 30 2.5.3 Mukah 30 2.6 Tile Manufacturing Industry 31 2.6.1 Porcelain tile Production 34 2.7 Technical aspects and specification of porcelain tiles 37 2.7.1 Water absorption of porcelain tiles 38 2.7.2 Dimensional and surface quality 40 2.7.3 Modulus of Rupture (MOR) 42 2.7.4 Fired Color 45 2.8 Processing Processes Involved 45 2.8.1 Sorting of raw material 48 2.8.2 Milling Process 49 2.8.3 Viscosity Measurement 51 2.8.4 Firing 53 CHAPTER 3 54 METHODOLOGY 54 3.1 Selection of mine site 55 3.2 Property testing of the clays 57 3.2.1 Milling 57 3.2.2 Viscosity Measurement 58 3.2.3 Drying and Pressing 59 3.2.4 Firing 60 3.2.5 Fired Shrinkage and Weight loss 60 3.2.6 Fired Color 61 3.2.7 Water Absorption 62 3.3 Characterization methods of porcelain tiles 62 3.3.1 Scanning Electron Microscope (SEM) 62 3.3.2 X-ray Diffraction (XRD) 63 3.3.3 Coefficient of Thermal Expansion (CTE) 65 CHAPTER 4 67 RESULTS AND DISCUSSION 67 4.1 Introduction 67 4.2 X-Ray Fluorescence (XRF) of clay 67
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4.3 Scanning Electron Microscopy (SEM) of clays 69 4.4 X-Ray Diffraction (XRD) of clays 72 4.5 Raw Material Milling Behavior 75 4.6 Water absorption results 77 4.7 Fired Shrinkage Measurement 78 4.8 Fired Color 79 4.9 Modulus of Rupture (MOR) of clays 80 4.10 Coefficient of Thermal Expansion (CTE) 81 4.11 Comparison of clay properties 83 4.12 Comparison of the milling results of porcelain tiles 84 4.13 Porcelain tile property 85 4.14 Modulus of Rupture (MOR) of porcelain tiles 88 4.15 Comparison of properties of porcelain clays 89 CHAPTER 5 92 CONCLUSION AND RECOMMENDATIONS 92 5.1 Conclusion 92 5.2 Recommendation for future works 94 REFERENCES 95 APPENDIX 99
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LIST OF TABLES
PAGE
Table 2.1 Current names of clay 12
Table 2.2 Malaysia’s production of kaolin by state 17
Table 2.3 Malaysia’s production of kaolin 18
Table 2.4 Malaysia’s production of Silica by state 23
Table 2.5 Malaysia’s Historic production of silica 23
Table 2.6 Malaysia’s production of Clay and Earth Materials by state 26
Table 2.7 Malaysia’s production of clay and earth materials 26
Table 2.8 Top ceramic tile exporting countries 36
Table 2.9 Worlds top ceramic tile manufacturers 37
Table 2.10 MOR calculation 43
Table 3.1 Milling conditions for the clays 58
Table 4.1 XRF analysis results of the clays 68
Table 4.2 Properties of the milled clays 76
Table 4.3 Weight measurements of the clay samples 77
Table 4.4 Length Measurements of the clay samples 78
Table 4.5 Fired Color of the clays 79
Table 4.6 Dry MOR values for the clays 80
Table 4.7 Comparison of all the properties of the fired clays 83
Table 4.8 Properties of the milled porcelain tile using different plastic 84
clays
Table 4.9 Properties of porcelain tiles fired at 1113.5°C 85
Table 4.10 Properties of porcelain tiles fired at 1120°C 87
Table 4.11 Properties of porcelain tiles fired at 1127°C 88
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Table 4.12 Dry MOR values for the porcelain tiles using different clays 89
Table 4.13 Comparison of the properties of the porcelain tiles fired at different temperatures 90
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LIST OF FIGURES
PAGE
Figure 2.1 Schematic illustration of rock alteration 10
Figure 2.2 Diagram of the structure of the kaolinite layer 15
Figure 2.3 The structure of illite 19
Figure 2.4 Smectite structure 20
Figure 2.5 Mines in Peninsular Malaysia 27
Figure 2.6 Mines in Sarawak 28
Figure 2.7 Site location of the BB clay mine 29
Figure 2.8 Location of the MS mine in Sarawak 32
Figure 2.9 Dimensional changes of the porcelain tile 35
Figure 2.10 Central elements in the ceramic tile manufacturing process 38
Figure 2.11 Scheme of dimensional properties 41
Figure 2.12 Loading system in the measurement of modulus of rupture 43
and breaking strength
Figure 2.13a Stage 1 of the selection process of mines 46
Figure 2.13b Stage 2 of the selection process of mines 46
Figure 2.13c Stage 3 of the selection process of mines 47
Figure 2.13d Stage 4 of the selection process of mines 47
Figure 2.14 Coning and quartering method 48
Figure 2.15 Typical Alumina fortified jar mill 50
Figure 2.16 Porcelain mill in a polymer encasement 50
Figure 2.17 Slip Rheology curves 52
Figure 3.1 Summary of research methodology 54
Figure 3.2 Location of Batang Berjuntai (BB) in Selangor 55
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Figure 3.3 Location of Paloh (PJ) in Johor 56
Figure 3.4 Location of Chamek (CJ) in Johor 56
Figure 3.5 Ford cup for viscosity measurement 58
Figure 3.6 Schematic diagram of an x-ray diffractometer; 64
Figure 3.7 X-ray diffraction geometry 65
Figure 4.1 SEM images taken under 3x and 5x magnification 75
Figure 4.2 XRD plot of the BB clay 77
Figure 4.3 XRD plot of the CJ clay 78
Figure 4.4 XRD plot of the PJ clay 79
Figure 4.5 XRD plots of the MS clay 80
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LIST OF ABBREVIATIONS
BB Batang Berjuntai
CJ Chamek, Johor
CRC Ceramic Research Company
CTE Coefficient of Thermal Expansion
GTI Guocera Tiles Industries
MOR Modulus of rupture
MS Mukah, Sarawak
PJ Paloh, Johor
SEM Scanning electron microscope
XRD X-ray diffraction
XRF X-ray Fluorescence
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SUITABILITY OF BALL CLAY FROM MUKAH, PALOH AND CHAMEK TO BE USED IN THE PORCELAIN TILE INDUSTRY IN MALAYSIA
ABSTRACT
Ball clays are an important raw material in the manufacture of porcelain tiles to offer fired strength. In Malaysia, there are several locations of ball clay mining, such as
Batang Berjuntai in Selangor, Chamek and Paloh in Johor and Mukah in Sarawak.
Guocera Tiles Industries currently uses the ball clays from Batang Berjuntai in their porcelain tile manufacturing. However, the Batang Berjuntai clay is running low on stock.
Therefore this thesis presents the properties of the clays from Paloh, Chamek and Mukah to determine their suitability to be used in the porcelain tile manufacturing process of
Guocera Tile Industries. In order to study this, physical property testing was carried out on all the four clays and their clay properties were analyzed. These four clays were also used in the porcelain tile formula to study the effects of changing the source of ball clay on the properties of the tiles. The processes involved in the production the test samples of clay and porcelain tiles include batching, milling, drying pressing and firing. The tests carried out on these samples were shrinkage, water absorption, fired color, MOR and COE. The main properties looked into were the dry MOR and water absorption values for both the clay and the porcelain tiles. Based on the results, the Paloh and Chamek clay showed near zero porosity that is 0.02 % and 0.08 % respectively when fired at a temperature of
1120°C, as compared to the Batang Berjuntai clay that had a porosity of 0.15 % and 1.02% porosity for the Mukah clays at that same temperature. The MOR values for the porcelain tiles using these four clays were in the range of 23-30 N. Judging by these values, the
Paloh and Chamek clays exhibit properties most similar to the Batang Berjuntai clay and therefore is most suitable to replace it in porcelain tile manufacturing.
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KESESUAIAN TANAH LIAT BEBOLA DARI MUKAH, PALOH DAN CHAMEK UNTUK DIGUNAKAN DALAM INDUSTRI PEMBUATAN JUBIN PORSELIN DI MALAYSIA
ABSTRAK
Tanah liat bebola adalah satu bahan mentah penting dalam pembuatan jubin porselin. Di Malaysia, terdapat beberapa lokasi lombong tanah liat bebola seperti Batang
Berjuntai di Selangor, Chamek dan Paloh di Johor dan Mukah di Sarawak. Guocera Tiles
Industries kini menggunakan tanah liat bebola dari Batang Berjuntai dalam pembuatan jubin porselin mereka. Namun tanah liat Batang Berjuntai hampir kehabisan stok. Oleh itu laporan ini membentangkan sifat-sifat tanah liat dari Paloh, Chamek dan Mukah untuk menentukan kesesuaiannya untuk digunakan dalam proses pembuatan jubin porselin
Guocera Tile Industries. Dalam usaha untuk mengkaji ini, ujian sifat fizikal telah dijalankan ke atas keempat-empat tanah liat dan sifat-sifat tanah liat mereka telah dianalisis. Tanah liat ini juga telah digunakan dalam formula jubin porselin untuk mengkaji sifatnya dalam jubin porselin. Proses yang terlibat untuk menghasilkan sampel tanah liat dan porselin jubin termasuk, pencampuran, pengeringan, menekan dan pembakaran. Ujian yang dijalankan ke atas sampel ini adalah pengecutan, penyerapan air, warna, MOR dan COE. Sifat-sifat utama yang dilihat adalah MOR dan penyerapan air untuk kedua-dua tanah liat dan jubin porselin. Berdasarkan keputusan, proses pembuatan
Paloh dan Chamek tanah liat menunjukkan keliangan hampir sifar iaitu 0.02% dan 0.08% masing-masing apabila dibakar pada suhu 1120°C, berbanding dengan tanah liat Batang
Berjuntai yang mempunyai keliangan 0.15% dan tanah liat dari Mukah yang mempunyai keliangan 1.02% pada suhu yang sama. Nilai MOR untuk jubin porselin menggunakan empat tanah liat adalah dalam lingkungan 23-30 N. Berdasarkan nilai-nilai ini, tanah liat
Paloh dan Chamek paling serupa dengan tanah liat Batang Berjuntai dan paling sesuai untuk menggantikannya dalam pembuatan jubin porselin.
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CHAPTER 1
INTRODUCTION
1.1 Clays
Clays are one of the more important industrial raw materials that are used for a variety of industries (Konta, 1995). Clays are widely utilized in many sectors worldwide.
They are important in geology, agriculture, construction, engineering, process industries and even environmental applications. Traditional applications of clays are many, and these include industries such as ceramics, paper, paint, plastics, drilling fluids, foundry bondants, chemical barriers, liquid barriers, and catalysts (Murray, 2000). The applications of the clay minerals in the various industries are closely related to their structure and composition, important characteristics relating to applications of clay minerals are particle size, surface chemistry, particle shape, surface area, and other physical and chemical properties specific to a particular application such as viscosity, color, plasticity, green, dry and fired strength and water absorption among others (Murray 1991). In the ceramic tile industry, the clay properties of interest are plasticity, chemistry, color, refractoriness, solubility and corrosion resistance, electrical properties etc. (Burst, 1991).
1.1.2 Clay mining in Malaysia
Sustainability in the mining of clays depends on the nature of the resource, its usage, extraction practices, and the reuse of land affecting the mining. Although there are abundant clay resources in Malaysia, a large quantity of these clays are common clays used in large volumes for simple structural products like bricks, pipes, roof tiles and flower pots. Other less common clays have special properties that enable them to be used in higher value products. Sustainable extraction of clay resources will depend on using the 1 appropriate clay for a given application, avoiding the use of high value clays for the production of low value products, and avoiding excessive digging and ground disturbances during extraction. Most clay resources that have been identified occur in thin layers and at shallow depths (less than 10 meters). Mining is extensive rather than intensive. If large volumes of clays are extracted, land areas affected can be substantial. Good clays should be properly stockpiled and conserved otherwise it may go to waste or become inaccessible
(Wan, 2016). A problem that may be faced when it comes to the mining industry is the availability of the minerals in the long run.
1.1.3 The tile manufacturing scenario in Malaysia
Ceramic tile manufacturers in Malaysia have been long out of investor’s radar due to low profile and tight shareholding The major tile manufacturing companies in Malaysia include Guocera, Seacera, White Horse, MML and Kim Hin (The Star, 2014). With nearly
50 years of manufacturing experience. Guocera is the tile brand of choice in over 50 countries from the America and Europe to the Middle East and Asia-Pacific. Guocera is one of Malaysia’s largest manufacturers and exporter of tiles. Modern manufacturing facilities in the manufacturing plants use the latest production technologies and design to meet ever growing global demands and expectations. Guocera’s R&D centre (Ceramic
Research Company-CRC) which is ISO-IEC 17025:2005 accredited, the only one of its kind in South East Asia. At CRC, comprehensive analysis and testing of raw materials are conducted according to stringent measures, resulting in unmistakable quality and reliability that are the hallmarks of Guocera tiles (Guocera, 2016).
The production of ceramic tiles is growing worldwide at a rate of 300 million m2/year and has already passed 10 billion m2 in 2012. This sort of rapid growth results in
2 an increasing demand for raw materials, whose global consumption can be estimated around 230 million tons/year (Dondi et al. 2014). The raw materials used in Guocera originate from several mines both in Malaysia and worldwide.
1.1.4 Research Background
This research was carried out as part of a collaboration between the Universiti
Sains Malaysia (USM) Engineering campus, and the Ceramic Research Company (CRC), to find out the properties of plastic clays mined from several mines in Malaysia, more specifically the clays mined from Batang Berjuntai (BB) in Selangor, Chamek (CJ) and
Paloh (PJ) in Johor, and Mukah (MS) in Sarawak. The reason for doing this study is to determine the suitability of these clays to be used as raw materials in the porcelain tiles production, to replace some of the current plastic clays being used by Guocera Tiles bhd, because the current supply of the plastic clays that are being used in production (from BB) are running in short supply. Before the supply completely diminishes, the company needs to find a suitable alternative replacement.
All the techniques and methodology for this experiment were in accordance to the methods and standards used in CRC. In order to carry out this research, physical tests, rheological tests, and mineralogical tests were carried out at the labs of CRC to determine the properties of the clays, with respect to a control clay sample which is currently being used in factory production. These clays were then plugged into a porcelain tile body formula to determine how these clays will behave when used in tiles, and to see whether the properties of the tiles meet the specification as required by Guocera. Based on the properties determined from these tiles, the suitability of these clays to be used in the manufacturing on a large scale was determined.
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1.2 Problem Statement
Ball clays are fine grained, highly plastic sedimentary clays which fire to a light or near white color. They are used in the manufacture of ceramic whiteware and are valued for their plasticity, which makes them easy to mould, their unfired strength and the fact that when fired they have a light color (Virta, 2000). When ball clays are added in porcelain tiles, they contribute towards the property of the porcelain tiles such as water absorption and open porosity close to zero (Galos, 2011a). Without the presence of ball clays, the porcelain tile will not exhibit such properties. Guocera Tiles Industries (GTI) both in Kluang in Johor and Meru in Selangor are using the Batang Berjuntai clays as their main source of ball clays in the production of porcelain tiles. However the ball clays being mined from Batang Berjuntai (BB) are depleting and considered medium grade raw material (Hussin et al., 2014), and the supply is depleting and may possible run out in the next few years. Therefore, this research paper will assist in finding new ball clay mine reserves to be used in the GTI porcelain tile industry.
In Malaysia, there are currently no published studies on properties of clays from
Paloh (PJ), Chamek (CJ) and Sarawak (MS). There is only a published paper on the properties of clays mined from Batang Berjuntai (Hussin et al., 2014). This does not provide sufficient results on the overall plastic clay situation in Malaysia. To the knowledge of the author, no property testing has been carried out on determining the suitability of the , PJ,CJ and MS clays. This presents a research gap that this study intends to fill seeing as ball clays are an important material in a variety of industries and possesses many uses.
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1.3 Objectives
This study aims to achieve several objectives
1. To study the properties of clays from Mukah, Paloh and Chamek
2. To prepare a record of the properties of clays from Mukah, Paloh and Chamek
3. To determine the suitability of Mukah, Paloh and Chamek clays to be used in
porcelain tiles.
1.4 Scope of study
This research involved a detailed study of several clays from Malaysia. The locations of these mines were in Malaysia, more specifically Paloh and Chamek in Johor and Mukah in Sarawak. Various testing was used to determine the properties of these clays, particularly (i) the properties of the raw materials; and (ii) the properties of the clays when included in a porcelain tile formula. The properties determined from these tests are significant in gauging whether or not the studied clays are suitable to be used in the manufacturing process. To determine the properties, several tests were carried out that includes tests such as physical, chemical and mineralogical tests, to determine the properties of the clays. Once the properties of these clays are compared to the control clay sample, then these clays were used in an actually body formulation to determine the properties of the tiles that were produced using these clays, and whether they conform to the existing standards used in Guocera’s tile production.
From January to April 2016, tests were carried out at CRC and USM, and the data collected was analyzed, in order to achieve the research objectives. All information obtained from this report are going to be kept in CRC for future reference and future
5 works. In the event that the plastic clay mines in Malaysia are on short supply, the results from this work can be used as a reference for plastic clay properties.
1.5 Thesis Outline
This thesis is organized into five main chapters:
Chapter 1 introduces briefly the coverage of the thesis, including the overview on the research background, problem statement, objectives and scope of the research work.
Chapter 2 covers in detail existing literature on clays and clay minerals, its properties and usage in the tile industry. Information on the technology used is also included in this chapter.
Chapter 3 presents the overall flow of this study, information about the location, equipment and methodology of the experimental work.
Chapter 4 discusses the results obtained from the study. This includes the physical property results, the mineralogical properties, and porcelain tile properties.
Chapter 5 summarizes and draws conclusions for this study. Recommendations for future work were also proposed.
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CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
Malaysian is abundant with a variety of natural resources, and this includes a number of different types of clay. As of 2015, there were approximately 9 billion metric tons of land consisting of various clays such as ball clays, kaolinitic clays, silica sand, quarts rock and marine clay in Malaysia (Tan, 2015). All these clays can be mined from various locations around Malaysia, each location providing a substantial amount of each type of the clay. However in this study, the area of interest lies in studying the characteristics of ball clays mined from specific mines in Mukah, Paloh and Chamek, as compared to the properties of plastic clays mined from Batang Berjuntai. The data obtained from this research will be analyzed and the suitability of the Sarawak and Johor clays will be determined, to assess their suitability to be used in the tile making industry, more specifically in the porcelain tile manufacturing in ‘Guocera’, which manufactures a large range of porcelain tiles both for import and export purposes.
2.2 Clays
The main use of clays is in the ceramic industry. The word “Ceramic” itself has originated from the Greek work, “Keramos”, which means pottery. It also relates to the ancient Sanskrit word whose root meaning is to burn (Nitesh, 2009). Since ancient times, fired clays have been used as building materials in various fields. In general, the common clays are the most widely used raw materials for clays (Barreiro 2015). Clays are widely used in the manufacture of many traditional ceramics, and each ceramic product requires clays having particular and appropriate characteristics. For example, they must not contain 7 a swelling phase, their loss of weight and shrinkage, after drying firing have to be low.
Clay deposits areas have a high economic potential, and soil mineralogical compositions, plasticity and porosity are fundamental properties for industrial applications. Kaolinite- illite is the most widely used clay mixture in the ceramic industry. Fluxes such as alkaline oxides (mainly K2O and Na2O) in reaction with silica and alumina promote liquid phase formations that facilitate densification (Baccour et al., 2008).
The oldest ceramic raw material is clays. Clays are defined as an earth that forms a coherent, sticky mass when mixed with water. When wet, this mass is readily moldable, but if dried it becomes hard and brittle and retains its shape. Moreover, if it is heated to redness, it becomes still harder and is no longer susceptible to the action of water. Clays may take various forms, but it is easily recognized as the sticky, tenacious constituent of soil, but it frequently occurs as a rock. However, owing to compression, this initial rock is so hard and compacted that it initially is not plastic and is almost impermeable to water.
However, these rocks can be rendered plastic by suitable treatment. Like all rocks, these clays contain a number of different minerals, that are divided into two main groups, the kaolinites and the montmorillonites, the former being the more important industrially
(Worall, 1986).
2.2.1 Formation of clays
The origin of clay starts with rocks. Rocks are hard, compact and are generally originated below the surface of the earth, which is below the interface of air, water and rock. They are hard and compact because they have been compressed by the weight of the sediments or other rocks at some depth at significant temperatures. When these dense materials are brought to the surface at the air-water-rock interface through mountain-
8 building forces or volcanic eruption, they are unstable. These rocks are unstable in the rain. Rainwater, combined with atmospheric carbon dioxide (CO2) becomes slightly acidic, containing an excess of hydrogen (H+) ions, and this attacks the rocks. More specifically, the minerals in the rocks are attacked. Under these atmospheric conditions, rocks become hydrated. Overall they exchange hydrogen ions for other similarly charged elements (cations) in the crystals which compose the rock. This phenomenon is called chemical weathering when it occurs on the surface of the earth. This weathering is essentially an exchange of hydrogen for different ions such as sodium (Na), potassium (K) or magnesium (Mg) in minerals. In effecting this exchange, new minerals are formed.
There are considered as clay minerals when they are silicates. Some elements especially iron (Fe) tend to form oxides, which is they combine directly with the oxygen in the air to form a phase or mineral of the element and oxygen. The elements easily expelled from minerals are absorbed into the slightly acidic water as ions, such as Na+ as an example.
These are soluble elements. The end result of these chemical alteration processes is to produce clay and oxides which is the basis of mud and to produce ion-charged water. This is shown schematically in Figure 2.2. The interaction of acidic water and rocks, weathering is one of the segregation of the major elements into new minerals. The cation elements which are found in new clays of weathering origin are silicon (Si), aluminiun
(Al), hydrogen (HO and some iron (Fe) and manganese (Mn). Some potassium (K) is also fixed in the mineral. The oxides are mostly iron (Fe). (Velde et al., 1999)
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Figure 2.1. Schematic illustration of rock alteration to form different clays (Velde et al., 1999).
Figure 2.1 shows the schematic illustration of how rocks form clays. Mineral components of the rock are illustrated as minerals A to D. Hydrogen-rich rainwater falling on the rock alters the minerals by introducing hydrogen ions in the solids in place of ions such as sodium (Na), potassium (K) calcium (Ca) or magnesium (Mg)which become dissolved ions in solution. Some minerals do not alter readily, such as mineral D, and become sand grains of smaller size. Some elements form oxides (notably iron, Fe) and others clay minerals (Al and Si). Three materials are produced by the alteration process, solutions containing soluble elements, those exchanged for hydrogen ions, unaltered solids and new solids which are clay and oxides. These clay and oxides are predominant in soils.
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The works of Jordan et al., and Meseguer et al., in the tile industries in Spain and
Chile show that the properties of the clay there are reflective of the mineral composition and geographical topography of the land (Jordán et al. 2015; Meseguer et al. 2010). When properly studied, the clays from various locations are able to be used for a variety of uses in various fields, and can contribute significantly to the economy of the country.
2.3 Types of clays
Clay materials are composed of solid, liquid and vapor phases. The solid phases are of mineral and organic phases that make up the framework of the clay materials. The mineralogy can be broadly subdivided into the clay and non-clay minerals, including poorly crystalline, so-called ‘amorphous’ inorganic phases. By definition, minerals are crystalline solids with well-ordered crystal structures but clay minerals and other inorganic phases in clay materials are often poorly crystalline compared to minerals such as quartz and feldspar (Geological society of London, 2006). According to Bergaya and Lagaly there are several types of clays (Bergaya & Lagaly 2006). This is shown in table 2.1. The different compositions of the clay lend to its unique properties. For example, the quartz is a nearly infusible, non plastic, has a very little shrinkage and is of low tensile strength, whereas the properties of kaolinite are plastic and quite refractory, but shrinks considerably when burning (Weems, 1903)
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Table 2.1 Current names of clay (Bergaya & Lagaly 2006)
Types of clay Origin Main clay constituent Ball clay Sedimentary Kaolinite Bentonite Volcanic rock alteration Montmorillonite Bleaching earth Acid-activated bentonite Decomposed Common clay Sedimentary or by weathering Various Fire-clay Sedimentary Kaolinite China clay Sedimentary Kaolinite Flint clay Sedimentary with subsequent diagenesis Kaolinite Fuller’s earth Sedimentary, residual or hydrothermal Montmorillonite, palygorskite, sepiolite Primary kaolin Residual or by hydrothermal alterarion Kaolinite Secondary Kaolin Authigenic sedimentary Kaolinite Laponite Synthetic Hectorite-type clay Nanoclay Montmorillonite
2.3.1 Ball Clays
Ball clays are defined as fine grained, highly plastic, mainly kaolinitic clays, the
higher grades of which fire to a near white color in oxidizing atmospheres (Zanelli et al.
2015a). Ball clays lend a number of desirable properties to fired tile bodies. As shown by
the research works of researches in Poland, ball clays, because of their composition
provide the fired porcelain tile with good mechanical strength after firing and a desirable
fired color (Galos, 2011a). These plastic white-firing clays (ball clays) assure good
molding properties of ceramic batch and high mechanical strength of the raw tiles after
drying. The presence of kaolinite promotes mullite formation, while occurrence of illite
and smectites contributes to formation of glassy phase assuring good densification of the
ceramic body during its firing.
To date, the properties of the Ukrainian ball clays are the best in the world. This
fact can be attributed to the mineralogical composition of the clays that are unique 12 comparing to other ball clays from around the world (Zanelli et al. 2015b). The peculiarity of the Ukrainian ball clays are due to the unique mineralogical composition and the grain size distribution. However their chemical composition is similar to conventional ball clays.
Due to the morphology of the Ukrainian clays that appear as subhedral thin flexible lamellae, this and the other factors explain the technological behavior of these clays that make them have higher plasticity and slip viscosity, lower compressibility and faster sintering kinetics with respect to conventional ball clays.
2.3.2 Structure present in clay raw materials
The structures present within the clay are the ones responsible for the difference in property in the clay. This is known as the clay mineral composition. Clay mineral composition refers to the identity and relative abundance of all the clay-mineral components. Since certain clay minerals which may be present in small amounts may exert a tremendous influence on the attributes of a clay material, it is not adequate to only determine the major clay-mineral compositions. Thus, a small amount (5%±) of smectite in clay is likely to provide a material very different from another clay with the same composition in all ways, except for the absence of smectite. In order to make complete clay-mineral determinations, it is frequently necessary to fractionate the clay grade to concentrate minor constituents so that adequate analytical data can be obtained.
There are several structures in the clay when mined (Weems, 1903). The clays are generally divided into three classes; the porcelain clay which is approximately pure kaolin that burns to white or light-cream color. Plastic clays contain more impurities than the porcelain clays which burns to a yellow-red color and is used for ordinary earthenware.
The last class of clays is the fire-clays that are similar to the porcelain clays in
13 composition, but contain larger quantity of iron, silica and quartz. In order to quantify the clays, methods of rational analysis are used. It is necessary and customary for the manufacturers of clay products made from high grade clay to use rational analysis as a guide for their mixture to obtain a constant product. This method separated clays into the middle components and enables one to obtain an idea of the physical characteristics of the material. This is said to be more important than the determination of the chemical composition of the clays. The object of the analysis may be used to supply information on the purity of the clay, showing the properties of silica, alumina, combined water and fluxing properties. From this analysis we can also form an estimate of the refractoriness of the clays and the sum of the fluxing impurities. Also, the color to which a clay will burn may also be judged approximately. The greater amount of iron present, the deeper red the clay will burn, provided the iron is evenly and finely distributed.
Rational analysis is used to solve the problem of quantitative determination of mineralogical phases. The mineralogical composition is defined by the type and quantities of minerals that constitutes the material. With a combination of quantitative chemical and qualitative mineralogical analyses, enough information is available to solve the problems of quantitative determination of mineralogical phases (Coelho et al. 2001).
Clays are among the most widespread sedimentary rocks, which are mainly composed of minerals such as kaolinite, illite, montmorillonite and other aluminium silicates, as well as other various ingredients. These include quartz, apatite, granite, iron hydroxide and many more. According to the mineralogical composition, there are three main groups of clays, the kaolinites, montmorillonites and illites. There are also 30 different types of pure clays within these categories. However, most of the natural clays are a mixture of these different types (Barreiro 2015).
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2.3.2.1 Kaolinites
Kaolinitic clays are versatile industrial materials that are generally used as fillers or raw materials in ceramics, plastics, paints, paper, rubber and a variety of other applications
(Ariffin et al. 2008). The idealized structure of the kaolinite mineral is that of a single sheet of hydroxyls octahedrally coordinated to aluminium cations linked to a single sheet of oxygen tetrahedral centred by silicon atoms. (Zbik & Smart 1998)
Figure 2.2 Diagram of the structure of the kaolinite layer (adapted from Grim 1962)
Other members of the kaolinite group can be formed by the replacement of some of the silicon in the tetrahedral layers by aluminium, and by the replacement of aluminium in the octahedral layers by magnesium or iron. In the kaolins, there are two forces acting between the kaolinite sheets, van der Waals’ forces and hydrogen bonds (Ryan, 1963).
Kaolinite, as shown in figure 2.2 is less reactive as compared to smectites and palygorskites when incorporated into most industrial formulations. The more important properties that kaolin and ball clay impart to ceramics are plasticity, green strength, dry strength, fired strength and color, refractoriness, ease of casting in sanitaryware, low to zero absorption of water, and controlled shrinkage. Shrinkage is an important property 15 because ceramic articles undergo shrinkage at two different points in the manufacturing sequence. During drying, the article will shrink in varying amounts depending on the composition and the percentage of water present. During firing, the ceramic article will further shrink. Therefore, it is important to know both the drying and firing shrinkage. decrease as the particle size increases. In the fired body, the firing shrinkage and water absorption generally decrease, whereas the modulus of rupture (MOR) and fired whiteness generally increase as the particle size increases (Murray 2006).
The works carried out by Ariffin and team (Ariffin et al. 2008) for kaolinitic clays in the Lampas region in Simpang Pulai, Ipoh, Perak meets the specifications and requirements of various industrial applications. The crude kaolin clay exhibited low levels of iron oxide, titania and total alkali content. The brightness or whiteness before and after firing was excellent. However, if the size of the Lampas kaolin clays were finer, the properties could be improved. Another research carried out showed that higher amount of kaolinitic clays showed lowest water absorption and higher strength due to better densification (Das et al. 2005). However other studies showed that the amount of kaolin present in a clay system does not affect the fired color in a liner pattern (Glass et al. 2013).
Kaolin is white inert clay with a broad pH and low conductivity. It has an excellent coating properties and suitable for most of the important applications such as in the ceramics, paper, rubber, plastics and aluminium industries. In Malaysia, about 112 million tonnes (Mt) of kaolin reserves have been identified. The major deposits are located mainly in Perak, 59 Mt; Johor, 25 Mt; Sarawak, 23 Mt; Terengganu, 5.3 Mt; Pahang, 4.5 Mt;
Sabah, 0.6 Mt; Pulau Pinang, 0.4 Mt; and Kelantan, 0.2 Mt. In 2010, there were 25 active kaolin mines and most of these mines are small-scale mines that operate by relying on demand. Perak had the most number of producers with 17 mines, Johor, 7 mines and
Pahang, one mine.
16
The total kaolin production in 2010 increased to 530,331 tonnes from 487,632 tonnes recorded in the previous year. About 52 per cent of the produced kaolin came from
Perak and it continued to be the major kaolin producing state in Malaysia. In 2010, the total kaolin production from Perak was 273,153 tonnes. The largest country's kaolin producers also located in Perak namely, Greatpac Mineral Sdn Bhd, Kaolin (M) Sdn Bhd and Tinex Corporation Sdn Bhd. These producers produced various grades of processed kaolin for local as well as for the export markets. The main uses of kaolin in Malaysia are for paper filler and for manufacturing ceramics, cement, paint, rubber and chemical products. In 2010, Malaysia exported a total of 55,150 tonnes of kaolin worth RM25.5 million mainly to Thailand, Singapore, Taiwan, Vietnam and Bangladesh. Malaysia also imported a total of 94,151 tonnes of premium grade kaolin worth RM59,592 million for the manufacturing of high quality ceramic products, in particular the porcelain figurines.
The major sources for imported kaolin were China, USA, United Kingdom, India and
Thailand (Anak Ginung & Abdullah 2015). Table 2.2 and 2.3 shows the kaolin production in Malaysia.
Table 2.2 Malaysia’s production of kaolin by state (Anak Ginung & Abdullah
2015)
State 2007 2008 2009 2010 tonnes mines Tones Mines Tones mines tonnes Mines Perak 259699 15 269702 16 225734 16 273153 17 Johor 73020 13 80962 8 44769 8 62878 7 Pahang 253000 1 154000 1 212000 1 194300 1 Selangor 1789 1 1789 1 5129 1 - - Total 587508 30 506462 26 487632 26 530331 25
17
Table 2.3 Malaysia’s production of kaolin (Anak Ginung & Abdullah 2015)
Year Tonnes 2001 364458 2002 323916 2003 425942 2004 326928 2005 494511 2006 341223 2007 587508 2008 506462 2009 487632 2010 530331
2.3.2.2 Illites
The basic structural unit of illites is a layer composed of two silica tetrahedral sheets with a central octahedral sheet. The tips of the tetrahedrons in each silica sheet point toward the centre of the unit and are combined with the octahedral sheet in a single layer. The unit is the same as that for montmorillonite except that some of the silicons are always replaced by aluminiums and the resultant charge deficiency is balanced by potassium ions.
18
Figure 2.3 The structure of illite (source: the internet, modified from Grim, 1962)
Illite, as seen from figure 2.3 can be formed under several minerogenetic conditions. The most abundant ores were originated in weathering, diagenetic, metamorphic or hydrothermal environment, where formation mechanism is termed illitization. This process mainly involves the transformation of smectite into illite.
Sedimentary environments may also contain illite although, because of their limited spatial distribution, they have minor importance (Ferrari & Gualtieri 2006).
Illite is one of the main clay phases used for the preparation of traditional ceramics
(Ferrari & Gualtieri 2006). This study of illitic clays in tile production shows that increasing the illite content will yield a higher percent of glassy phase and lowers the water absorption because of the lowering of the melting point. Illite can also provide plasticity and enhance fluxing action to the fired body
19
2.3.2.3 Smectites
The smectite minerals also known as montmorillonite occur only in extremely small particles. Smectite is composed of units made up of two silica tetrahedral sheets with a central aluminium octahedral sheet. All the tips of the tetrahedrons point in the same direction and toward the centre of the unit. The tetrahedral and octahedral sheets are combined so that the tips of the tetrahedrons of each silica sheet and one of the hydroxyl layers of the octahedral sheet form a common later.
Figure 2.4 Smectite structure (image source: taken from the internet, adapted from Grim
1962)
Figure 2.4 shows the structure of the smectite or the montmorillonite layer. In the stacking of the silica-alumina-silica units, O layers of each unit are adjacent to O layers of the neighboring units, with the consequence that there is a very weak bond and an excellent cleavage between them. The outstanding feature of the smectite structure is that
20 water and other polar molecules can enter between the unit layers, causing the lattice to expand (Grim, 1962)
2.4 Silica sand
Silica is claimed to decrease the shrinkage during firing and up to certain limits of temperature will increase the refractoriness. However, if present in combination with feldspar, it acts as a flux and somewhat increases the plasticity. Large amount of silica in the clay would also indicate the sandiness of the clay (Weems, 1903).
Silica sand is a strong granular material, with its main materials being quartz (Shi et al. 2016). Quartz is a common mineral with the same chemical composition but quartz and silica are not synonyms. Specific minerals always have a definite crystal structure while chemical compounds have no such restriction — just like every piece of carbon is not a diamond. Quartz is made of silica but so are also cristobalite, tridymite and few other minerals (polymorphs of silica). They are collectively referred to as silica minerals.
Quartz is the most common sand-forming mineral. However, it is not the most common mineral in the crust. That honor goes to feldspars. If the particular sand deposit contains almost nothing but quartz, we often call it a silica sand. Such sand deposits are said to be mature because other rock-forming minerals are already broken down by the weathering process leaving only the super-resistant quartz as a residue. Silica sand is a mineral resource. It is mined mostly for glass-making. Another major use of sand is a concrete production but that does not need sand to be as pure.
Malaysia has a large amount of silica sand resources. The Minerals and Geoscience
Department in Malaysia has estimated about 141.8 million tonnes (Mt) of silica sand resources throughout the country (Anak Ginung & Abdullah 2015). The largest of these 21 are in Sarawak, 45.7 Mt; Terengganu, 45.6 Mt; and Sabah, 29.9 Mt. Other states with silica resources are Perak (10.9 Mt), Selangor (8.41 Mt), Johor (1.0 Mt) and Kelantan
(0.27 Mt).
At present, silica was produced from silica sand mining and retreatment of amang.
In 2010, silica sand mining was carried out in the states of Johor, Sarawak, Perak and
Selangor. Amang retreatment plants in Perak also contributed to the overall silica production. There were 28 active producers in the country, with 14 of them in Perak, 11 in
Johor, two in Sarawak and one in Selangor. The total production of silica increased by 48 per cent to 932,159 tonnes from 630,394 tonnes produced in 2009. These was contributed from the huge jump in production from Johor and Sarawak. Johor produced a total of
608,967 tonnes , compared with 361,551 tonnes in 2009. This was 65 per cent of Malaysia total production of silica, while Sarawak produced 210,139 tonnes, Perak and Selangor produced only 94,500 tonnes and 18,553 tonnes respectively.
The bulk of the domestic silica produced goes towards the manufacturing of glass products. It is also consumed in minor quantity by ceramics, foundries, glass wool production industry and for water treatment. Export of silica sand in 2010 decreased slightly to 311,847 tonnes compared with 346,642 tonnes recorded in the previous year.
The main export destination were to Singapore, Japan, Republic of Korea, Indonesia and
Philippines (Anak Ginung & Abdullah 2015).
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Table 2.4 Malaysia’s production of Silica by state (Anak Ginung & Abdullah 2015)
State 2007 2008 2009 2010 Tones mines Tones Mines tonnes mines Tones Mines Johor 196140 8 242655 8 361551 8 608967 11 Sarawak 185838 2 345447 2 161115 2 210139 2 Perak 322000* 13 862500* 19 94500* 10 94500 14 Selangor 15243 1 16302 1 13228 1 18553 1 Total 719221 24 1466904 30 630394 21 932159 28 *included by-product from amang plants and tin mines
Table 2.5 Malaysia’s production of silica (Anak Ginung & Abdullah 2015)
Year Tonnes 2001 575105 2002 447398 2003 533617 2004 631402 2005 542297 2006 512277 2007 719221 2008 1466904 2009 630394 2010 932159
2.5 Clay mines in Malaysia
Malaysia is abundant with a variety of natural resources. All over Malaysia, there are mines for various minerals and clays, which have been exploited for decades.
Kaolinitic and plastic clays suitable for use in the ceramic an related industries are extensively found in Kuching, Sarikei and Sibu divisions. As shown in table 2.5 ad
2.6.There are currently 9 deposits of kaolinitic clays with an estimated reserve of about 22 million tones and 24 deposits of ball clays with an estimated reserve of about 38 million
23 tones have been identified. The major deposits are found in the Sibu area, with 16 million tones of ball clays, and the Sarikei-Bintangor area with 18 million tones of ball clays
The largest producer of ball clays in Malaysia is Unisil, which controls more than
90 % of the market with up to 500,000 tons per year, mainly destined for tile manufacture.
The main tile producers are in Johore State with Guocera Tiles Industries (GTI) in Kluang, producing 50000 m2/day. Other producers are MML, Yilay and Niro. The ball clay deposits are located near Kuala Lumpur, with recent discovered deposits in the Langgor area. The clays obtained from here are exported to Taiwan and Thailand. The clays mined can be described as low-carbon, kaolinitic ball clay of medium particle size and low plasticity. The clay has low combined iron and titania, 2.2 % but alkalis are higher at about
3 %. It has a reasonable fired properties with 75 reflectance at 1120°C. Carbon and salts are low.
The clay has a potential in sanitary ware and possible earthenware. The low carbon would make it suitable for fast firing applications, but the low strength may detract from its use in tiles unless combined with more plastic ball clays. In general, its properties would lend themselves to a number of uses (Kogel et al., 2006)
In a review by the Malaysian Mineralogical department in 2010, clays include common clay, ball clay, fire clay, shale, and earth materials such as laterite, earth and red earth. Most products made from them are fired such as structural and face bricks, pavers, vitrified clay pipes, tiles and various other building related products. Shale and common clay are used in the making of Portland cement clinker. Fire clay is used in refractory products such as firebrick and block, high alumina brick and others.
Malaysia has abundant clay resources estimated at 685 million tonnes (Mt) with ball clay about 583 Mt and the rest being mottled or structural clay. Deposits of ball clay
24 are found in many states such as Terengganu (151 Mt), Johor (128 Mt), Kelantan (103
Mt), Pahang (94 Mt), Selangor (72 Mt), Sarawak (36 Mt), Pulau Pinang (10 Mt), Negeri
Sembilan (8.5 Mt), Kedah (6.5 Mt), and Perak (3.6 Mt).
In 2010, the total clays and earth materials production was 27 Mt, increase by 18 per cent from 23 Mt produced in 2009. The highest production came from Perak with 6.3
Mt, followed by Johor with 5.4 Mt; Kedah, 4.0 Mt; Terengganu with 2.5 Mt; Perlis; 2.4
Mt; and Selangor, 1.7 Mt. In addition, the clay production in 2010 experienced a drop of
29 per cent to 5.3 Mt from 4.1 Mt recorded in 2009. Similarly, the production value decreased to RM42.6 million in 2010 compared with RM51.1 million in 2009. Johor contributed about 38 per cent of the total clay production, amounting to 1.9 Mt, followed by Kedah with 0.66 Mt; Selangor with 0.65 Mt; and Pahang with 0.42 Mt.
The extraction of earth materials during 2010 also experienced a decrease of 15 per cent to 22.2 Mt valued at RM152 million, from 19 Mt in the previous year. Perak was the largest producer of earth materials with a total production of 6.2 Mt. Other states with high earth materials output were Johor (3.5 Mt), Kedah (3.3 Mt) Terengganu (2.3 Mt) and
Perlis (2.2 Mt) (Anak Ginung & Abdullah 2015). Table 2.6 and 2.7 show the production of the clay minerals and earth minerals in Malaysia.
25
Table 2.6 Malaysia’s production of Clay and Earth Materials by state (Anak
Ginung & Abdullah 2015)
State 2007 2008 2009 2010 Tones Min tonnes Mine Tones mine Tones Mine im s s s Terengganu 9841749 354 4965143 201 5713341 160 2542808 305 Perak 6001264 198 6591500 206 4817393 137 6361050 192 Johor 4324725 174 3337547 178 2998167 174 5444958 188 Kedah 484815 34 2100067 93 2114706 161 3996551 171 8 Perlis 323284 7 662034 7 1574618 16 2418384 21 Pahang 925731 97 841924 97 1522884 134 949311 96 Sarawak 3979441 158 3053252 135 1133849 139 1321500 115 N.Sembilan 985331 89 779875 80 1059959 76 1612947 130 Selangor 1246559 63 1109592 76 870135 59 1726846 93 Melaka 207799 33 383899 83 670954 159 623493 150 Kelantan 141725 69 195924 71 237670 104 187732 66 Sabah 190000 NA 307850 13 202891 10 298158 NA P.Pinang - - 736000 16 23893 2 65584 5 Total 2829242 126 2506521 1256 2296603 1330 2754322 1532 3 7 8 6
Table 2.7 Malaysia’s production of clay and earth materials (Anak Ginung & Abdullah
2015)
Year Tonnes 2001 29596 2002 23092 2003 23909 2004 22109 2005 28758 2006 25081 2007 28292 2008 25065 2009 22966 2010 27534
26
Figure 2.5 Mines in Peninsular Malaysia (Anak Ginung & Abdullah 2015)
27
Figure 2.6 Mines in Sarawak (Anak Ginung & Abdullah 2015)
28
2.5.1 Batang Berjuntai
Another area abundant with clays is the Batang Berjuntai area, in Selangor.
Geologically the area of Batang Berjuntai is overlain by pre-quarterner rocks and alluvial deposits. The pre-quarterner rock were classified as shale, schist and phyllite, whereas the alluvial deposits composed mainly of holosen and plestosen sediments such as clay, silt, sand and gravels. All these alluvial sediments were grouped either as part of Gula and
Beruas. (Hussin et al., 2014) Figure 2.7 shows an image of the clay mine from Batang
Berjuntai.
Figure 2.7 Site location of the BB clay mine (Hussin et al., 2014)
Based on prior research conducted investigations, it can be concluded that the clay resources from Batang Berjuntai can be considered as inhomogeneous and suitably classified as medium grade raw material. The investigation has confirmed that the clays from the studied area is kaolinitic type with small amount of quartz, muscovite and localized concentration of impurities (Hussin et al., 2014).
29
2.5.2 Paloh and Chamek
Both Paloh and Chamek are located in Johor. Johor is the 5th largest state by land area and 2nd most populous state in Malaysia, with a total land area of
19,210 km2(7,420 sq mi), and a population of 3,233,434 as of 2010. It is the southernmost state in Peninsular Malaysia, and is located between the 1°20"N and 2°35"N latitudes. The highest point in Johor is Gunung Ledang (1276 m). Johor has a tropical rainforest climate with monsoon rain from November until February blowing from the South China
Sea. The average annual rainfall is 1778 mm with average temperatures ranging between
25.5 °C (78 °F) and 27.8 °C (82 °F). Humidity is between 82 and 86%.
Paloh is a small town in the Kluang district of Johor, Malaysia. It has a rather balanced population of Chinese, Malays and Indians. This town is located 35 kilometers away fromKluang and about 32 kilometers away from Yong Peng.
Chamek is a village in the district of Kluang, Johor, Malaysia. The name originated from the Chinese variation of the word Jambi, which is rather hard to pronounce. The village is a multiracial village, having all Chinese, Malays and Indians. Mostly, the Malays are of the Javanese descendants, and they practiced the Javanese culture in their everyday life. The populations mainly work in rubber plantation, palm plantation, and a few opened grocery stores.
2.5.3 Mukah
Mukah is located in Sarawak, and Sarawak is located on the north-west coast of
Borneo and its area is 48300 square miles (Kaur 1998). Recent exploration in Sarawak identified a series of ball clays over and underlying coal seams in the Mukah Basin (Kogel et al., 2006) as shown in figure 2.8. These deposits are attracting attention from 30 international companies because they show potential for tiles, sanitary ware and tableware.
These Sarawak clays are similar in quality to the ball clay deposits of the Pontianak region of Kalimantan.
Figure 2.8 Location of the MS mine in Sarawak (image source: Google maps)
2.6 Tile Manufacturing Industry
Tiles manufactured in the industry are different than tiles produced for testing purposes. Industrial scale tile manufacturing processes involve several processes. In the end of these processes, the ceramic tile must meet specific requirements that range from technical characteristics (low porosity and wear resistance) to aesthetic properties (gloss and design) (Santos-Barbosa et al. 2013).
One of the factors that govern the properties of fired clays is the milling time.
Milling time is responsible for producing fineness in the grains of the clays produced, which will indirectly affect the sintering behavior, mechanical properties, and rheological properties of the clay, among other properties (Halima, 2015).
31
A study carried out in the Thai tile industry stated that small and medium ceramic tile production enterprises in Thailand consumes a substantial amount of energy (Tikul,
2014). With the exception of global warming effects, the environmental impacts of small and medium tile manufacturing plants need to be considered, in terms of energy wastage.
Therefore, any production method that saves energy and cost is most desirable in the manufacturing plant.
Plasticity is defined as the property of a material which permits it to be deformed under stress without rupturing and to retain the shape produced after the stress is removed
(Grim, 1962). The measurement of plasticity has been difficult to determine quantitatively.
In general, three ways have been used to measure plasticity. One is to determine the amount of water necessary to develop optimum plasticity or the range of water content in which plasticity of the material is demonstrated. Atterberg proposed that the lower value, called the plastic limit, and the higher limit, called the liquid limit, is the plasticity index.
A second method is to determine the amount of penetration of a needle or some type of plunger into a plastic mass of clay under a given load or rate of loading. Another way is to determine the stress necessary to deform the clay and the maximum deformation the clay will undergo before rupture.
Green strength is measured as the transverse breaking strength of a test bar suspended on two narrow supports in pounds per square inch or kilograms per square centimeter. Green strength has to be adequate for the piece to be handled without bending or breaking. Ball clays, which are finer in particle size than most kaolins, have a higher green strength
Drying shrinkage is the reduction in size, measured either in length or volume, that takes place when the clay piece is dried to drive off the pore water and absorbed water.
The drying shrinkage is expressed in percent reduction in size based on the size after 32 drying. In the laboratory, the measurement is made on a test bar after drying for a minimum of 5 h at 1051C. The drying shrinkage is related to the water of plasticity. It increases as the water of plasticity increases and also increases as the particle size decreases. Ball clays have higher dry shrinkage than most kaolins. The drying shrinkage of kaolinite increases dramatically with a decrease in particle size.
Dry strength is the transverse breaking strength of a test bar that has been dried to remove all the pores and adsorbed water. The dry strength of kaolins and ball clays is greater than their green strength. Dry strength is closely related to particle size (Murray
2006).
When studying the properties of any type of clays used in a tile, the main considerations are the physical properties such as the shrinkage, plasticity, fired and unfired strength etc. For example, the works of Galos and Boussak studied the effect of varying parameters of clays on the properties of the final end product of porcelain clays
(Galos 2011a; Boussak et al. 2014).
The increase in demand worldwide for the use of clays has lead to an increase in the study of the properties of the various types of clays. Some studies even used modeling to predict the behavior of tiles under different parameters (Santos-Barbosa et al. 2013). A computational model that permits predicting the intermediate variables of ceramic tiles during their processing (mass, dry bulk density, size, and thickness) and their final dimensions’ properties (size and thickness) was obtained. The multivariable model found makes use of both material balance equations and correlated equations. The used methodology proved to be a useful tool for planning and analyzing experiments to find the influence of the mean press operational conditions on the variables of the empirical relationships needed to complete the calculation model. These modeling make it easier to conduct experiments on tiles while obtaining reliable results. 33
2.6.1 Porcelain tile production
Porcelain tiles belong to the group of ceramic materials obtained by forming an appropriate ceramic batch under high pressure, usually between 35 to 45 MPa, and its single fast firing (40-50 min cycle) in roller kilns at a temperature up to a maximum of
1200-1230°C. Porcelain tiles have a very compact microstructure, with water absorption and open porosity being very close to zero. Figure 2.9 shows the changes that occus during firing of a tile body. The works of Martín, Rincón and Romero has told us that the porosity of the fired sample is directly linked other properties such as the linear shrinkage and the water absorption (Martín-Márquez et al. 2008). It is because of this that porcelain tiles possess very good physical and mechanical properties that includes high hardness, bending strength, torsion and abrasion resistance among others (Manfredini et. al, 1995).
As defined by the Spanish Ceramic tile Manufacturers association, porcelain tiles best meet requirements such as geometric tolerances, low water absorption, usually less than 0.5%, high mechanical strength and frost resistance, high hardness, high chemical and stain resistance with a broad spectrum of aesthetic possibilities (Santos-Barbosa et al.
2013). Thus this makes it desirable to be used in many applications such as floor tiles of hotels, toilet floor tiles, etc.
The properties of the porcelain tiles are distinctly related to the mineral composition of the raw materials used in the formula. Other factors that affect the properties are the process during batch processed and the firing cycle.
34
Figure 2.9 Dimensional changes of the porcelain tile (Santos-Barbosa et al. 2013)
In industry, porcelain tiles are produced via a wet milling route which covers three main stages: (i) milling/mixing and spray drying of the raw materials, (ii) pressing, drying and decoration of the green body, and (iii) firing and classifying of the finished product.
The schematic is as shown in figure 2.9.The first stage starts with the homogenization and wet milling of the raw materials, followed by the spray-drying of the resulting suspension.
In the second stage, the spray-dried powder with moisture content between 0.05 and 0.07 kg water/kg dry solids is pressed. The resulting body is dried and decorated. Finally in the third stage, the decorated body is fired in a single-layer roller kiln, to obtain maximum densification. After firing usually the tiles are classified according to the aesthetic properties and dimensional aspects, which are naturally related to the processing and compositional characteristics. Throughout these stages of the process, the porcelain tile will undergo a significant reduction in the size, depicted below.
35
According to a report featured in the magazine Ceramic World Review in 2009,
Malaysia was the 14th top exporting country for tiles, with 23 sq.m Mill. in 2009, ranking it as number 14 on the list of top exporting countries (Stock, 2014). As one of the top manufacturing companies in the world, Malaysia constantly needs to improve its tile manufacturing process to keep up with demands. Table 2.8 and table 2.9 show the top producing countries in the world for ceramic tiles and the world’s top exporting countries for ceramic tiles.
Table 2.8 Top ceramic tile exporting countries (2001-2009) (Stock, 2014)
Country 2005 2006 2007 2008 2009 % on 2009 % on (Sq,m (Sq,m (Sq,m (Sq,m (Sq,m consumption 2009 Mill) Mill) Mill) Mill) Mill) world exports 1. China 342 450 500 570 584 6.9 33.7 2. Italy 390 396 379 355 281 3.3 16.2 3. Spain 341 336 333 306 253 2.8 13.6 4. Turkey 97 93 104 92 67 0.8 3.9 5. Brazil 114 115 102 81 61 0.7 3.5 6. Mexico 46 55 56 62 51 0.6 2.9 7. Iran 14 19 17 27 49 0.5 2.3 8. Thailand 25 27 25 25 36 0.4 2.1 9. Poland 19 21 30 34 35 0.4 2.0 10. Portugal 34 36 37 37 32 0.4 1.8 11. UAE 25 32 38 34 31 0.4 1.8 12. Vietnam 12 15 25 25 28 0.3 1.3 13. Egypt 16 17 22 23 23 0.3 1.3 14. Malaysia 18 22 18 23 23 0.3 1.3 15.Germany 21 24 26 28 23 0.3 1.3 Total 1514 1657 1712 1722 1550 18.3 89.4 World Total 1715 1865 1910 1919 1935 20.5 100
36
Table 2.9 Worlds top ceramic tile manufacturers (Stock, 2014)
Country 2005 2006 2007 2008 2009 % 2009 on (Sq,m (Sq,m (Sq,m (Sq,m (Sq,m consumption Mill) Mill) Mill) Mill) Mill) 1. China 2500 3000 3200 3400 3600 42.3 2. Brazil 568 594 637 713 715 8.4 3. India 298 340 385 390 490 5.8 4. Italy 570 569 559 513 368 4.3 5. Iran 190 210 250 320 350 4.1 6. Spain 609 608 585 495 324 3.8 7. Vietnam 176 199 254 270 295 3.5 8. Indonesia 175 170 253 275 278 3.3 9. Turkey 261 265 260 225 205 2.4 10. Egypt 112 122 140 160 200 2.3 11. Mexico 196 210 215 205 200 2.3 12. Thailand 138 139 130 130 128 1.5 13. Russia 100 115 135 147 117 1.4 14. Poland 108 110 112 118 112 1.3 15. Malaysia 71 75 75 85 90 1.1 16. UAE 68 75 76 77 77 0.9 17. Portugal 72 74 74 74 70 0.8 18. Argentina 48 54 60 60 56 0.7 19. Saudi Arabia 20 22 34 40 55 0.6 20. Morocco 44 47 50 51 54 0.6 21. Germany 62 64 67 59 51 0.6 22. Colombia 40 44 48 50 50 0.6 23. USA 61 58 51 45 50 0.6 24. Ukraine 20 21 27 35 44 0.5 25. South Korea 46 44 42 39 42 0.5 26. South Africa 33 37 38 38 32 0.4 27. Taiwan 53 53 50 40 32 0.4 28. Syria 19 19 19 28 30 0.4 29. Algeria 28 28 28 28 30 0.4 30. Venezuela 26 28 30 32 30 0.4 Total 6713 7395 7866 8145 8176 96.0 World Total 7077 7760 8252 8495 8151 100.0
2.7 Technical aspects and specification of porcelain tiles
All the properties and specifications of porcelain tiles are in conformance to the
ISO 13006 standard of ceramic tiles. The manufacturing process of porcelain tiles to achieve its desired properties are shown in figure 2.10
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Figure 2.10 Central elements in the ceramic tile manufacturing process (Gabaldón-Estevan
et al. 2014)
2.7.1 Water absorption of porcelain tiles.
Porcelain is a vitrified product of mixtures of clay, quartz, and feldspar. Porcelain microstructures are grain and bond type with large particles of filler (usually quartz) held together by a finer matrix which is almost fully dense (Martín-Márquez et al. 2008).
Porcelain tiles have very compact microstructure with water absorption and open porosity being close to zero (Galos 2011b). The ASTM C373 standard describes the test methods and procedures to determine and ensure the water absorption of porcelain tiles is close to zero. In this test method, water absorption of tile specimens is calculated based on a five
38 hour boiling water method. This test is used to determine the degree of maturation of the ceramic tile body or for evaluating structural properties that may be required during installation. Five test pieces, weighing at least 50 grams and cut from the center of whole tiles are required for one test. Test pieces are dried to a constant mass, weighed and placed in boiling water for five hours then soaked in room temperature water for 24 hours. Wet weights are determined after soaking for 24 hours. The difference in weights of test pieces before and after boiling is used to calculate percent water absorption (ASTM C373 standard).
EN ISO 10545 - Part 3 standards describes in great detail the procedures to determine water absorption, apparent porosity, apparent relative density and bulk density.
This method is applicable to all ceramic tiles. The test must be performed on 10 whole tiles in cases where the surface of each tile is less than 0.04 m2; if greater than 0.04 m2, 5 tiles will suffice. In any case, every test sample must weigh a minimum of 50 g. After tiles are brought to a constant weight through drying, they are weighed with a precision which depends on the weight of the tile. Tiles are then placed to be boiled in a container of distilled or deionized water, in such a way that they do not touch the bottom and are completely immersed. Container should be kept at boiling point for two hours. Then tiles should be left cooling for four hours immersed in water. Once the tiles have been removed from the container, excess water is removed with a chamois leather and tiles are then weighed, again as precisely as for dry weight. The absorption of water, expressed as a percentage of the weight of the dry material, is expressed in the formula shown in
Appendix A.
The average absorption of water of the sample is determined by the arithmetic average of the individual results, and results must be rounded off to a single decimal place.
The determination of water absorption, which is required for a product’s assignment to a
39 group, remains the same as that stipulated by the European Standards (EN 99); other properties have also been added for which no requirement exists (that is, these properties are not considered in the sections on product requirements) but which may be useful in typifying the structure of the tile’s ceramic mass: for thesis properties, water absorption is measured through water impregnation at a residual pressure of 1001 kPa for 30 min.
2.7.2 Dimension and surface quality.
Warped tiles are considered useless, and have an undesirable appearance.
(Watchman 1991). ASTM C485, ASTM C499, ASTM C502: defines warpage, facial & thickness dimensions, and wedging. In these test methods, diagonal and edge warpage
(flatness), wedging (squareness), facial dimensions and thickness of ceramic tiles are determined. The diagonal warpage, edge warpage, and wedging are all reported as a percentage. Facial and thickness dimensions are reported in inches. All these faults may be due to inconsistencies during pressing. For optimum transport and pressing of tiles, the spray-dried body needs to contain a minimal moisture of approximately 4.5-7.5 % of water
(Watchman 1991). Figure 2.11 shows the dimensional properties of tiles that have undergone deformation such as warpage and centre curvature. These defects are set by
ISO 10646 standards to define dimensional properties of the tile.
One way to measure the surface quality of tiles is by looking at the quality of the surface, and the stains on them. The viscosity of tiles may affect the stain resistance of the porcelain tiles (Suvaci & Tamsu 2010). This reduction in viscosity occurs when the ratio of Na2O/K2O ratio increases. This will result in improvement of microstructure, that is the spherical pore morphology and the reduced closed porosity. This will cause the stain resistance to increase. For any slip system and the viscosity range, two critical viscosity
40 values need to be notices (i) the upper viscosity limit above which insufficient densification occurs and/or irregular pore structure is observes and (ii) the lower viscosity limit below which the tiles exhibit pyroplastic deformation. If for any system the viscosity of the tile is in between these two limits, then a high stain resistant polished porcelain tile can be readily produced.
Figure 2.11 Scheme of dimensional properties (ISO 10646 standards)
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2.7.3 Modulus of rupture (MOR)
The modulus of rupture (MOR) is also termed bending strength, which is derived from the magnitude of breaking strength by a mathematical formula. The result of the test, expressed in Newtons per square millimeter (N/mm2) provides the approximate mechanical strength of the ceramic tile independent of tile thickness. The breaking strength in direct relation to the load applied on to the tile with a corrective coefficient that relates the distance between supports and the width of the test pieces expressed in
Newtons (N). The result of the test is a function of tile thickness for the same type of material.
International standard ISO 10545-4 establishes a test method for the determination of the bending strength or modulus of rupture and breaking strength for all types of ceramic tiles. The calculation of MOR involves the measurement of the breaking load, F, and the breaking load on the entire piece. From the breaking load, the breaking strength, S can be calculated, which is then used to finally calculate the MOR, R of a sample. The description on the values of F, C, S and R are described in table 2.10. The modulus of rupture is only measures in tiles whose breaking strength is below 3000 N. The test method encompasses the following magnitudes (En, 2000). A diagram of the test machine used is also shown in Figure 2.12.
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Table 2.10 MOR calculation
Code Characteristic Definition F Breaking Load Force necessary to cause the test piece to break, expressed in Newtons according to a pressure gauge reader C Breaking load on entire piece In this case, the test is conducted on the entire tile, this being the most representative test S Breaking strength Breaking Strength 퐿 S=퐹 × 푏 Magnitude expressed in Newtons per square millimeter obtained by dividing the breaking strength by the square of the minimum thickness at the rupture cross section. R MOR Bending strength 3퐹퐿 3푆 R= = 2푏ℎ^2 2ℎ^2
Figure 2.12 Loading system in the measurement of modulus of rupture and breaking
strength
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The MOR is an intrinsic tile characteristic, which means that two ceramic tiles made by the same process but differs in the thickness will have the same modulus of rupture, even though the force required to break them is much larger in the thicker tile. An important modification has been introduced: the test report must note not only the load F required to break the sample and the modulus of rupture from bending, but also the
“breaking strength calculated S”. The modulus of rupture σ is undoubtedly an important parameter, but it refers to an intrinsic property of ceramic material: in physical terms, it represents work per unit of volume, a value that may be useful for the specifier but that gives no information on the maximum load that a tile can bear. This last parameter depends on the dimensions of the sample: in fact, given the same level of water absorption
(and thus the same intrinsic properties of the material), the value of the modulus of rupture from bending σ is the same, but the force F required to break the sample varies depending on the dimensions of the sample itself. (ISO 10545)
The works of Cavalcante et al studied the properties of white porcelain stoneware with different microstructure (Cavalcante et al. 2004). Porcelain tiles although have smooth and glossy surfaces, need to possess excellent mechanical properties due to the zero porosity. The excellent mechanical properties can be attributed to the porosity and phase composition. Also, mullite and zircon tend to increase the mechanical performance via matrix reinforcement, while quartz plays an opposite role. Another study also showed similar results. The research studied the proportion of crystalline and amorphous phases on the mechanical properties of the tile. The results obtained were that mullite increases the bending strength of the tile. However, the bending strength is not dependent on closed porosity, but is dependent on the open porosity of the sample (Martín-Márquez et al.
2010). From these research carried out, the mechanical properties of the tiles are
44 dependent on several factors other than just the mineralogical composition of the clays and raw materials.
2.7.4 Fired Color
EN ISO 10545 - Part 16 is a standard used for ceramic tiles to determine small color differences. This method was not included in the EN standards, but appears as part of the U.S. standards. The test method used is the one described in the standard ASTM C-
609, and measures small differences in color between an unknown sample and a reference tile; the standard specifies that this method should be used to measure only tiles that are solid color and smooth; with other tiles, the results may not be valid. The test is based on the use of a colorimeter; any colorimeter on the market may be used, so long as it gives values that can be mathematically transformed into the tristimulus values X,Y and Z The instrument is first calibrated using a primary standard (magnesium oxyde) or a secondary standard, depending on the indications of the supplier of the instrument. Measures are then taken of the unknown sample and the reference sample, alternately, until three readings have been taken of every tile. Finally, the standard specifies the method to be followed to calculate differences of color, specifically as regards instruments that give the values in L, a and b (which are transformed into X, Y and Z) ( ISO 10646-18 standards).
2.8 Processing Processes Involved
In any assessment of an industrial clay resource, the explorer or the developer needs to go through the various stages of resource assessment, raw material testing, and assessment of product quality, market size and market demand. All these data must then be analysed to establish development strategies and likely project costs. Such 45 categorization can provide a useful insight into the complexities of such studies, and be useful to determine which clays fall into which category. There are 4 different categories of clays, with category 1 being the clay with the most ideal property, and category 4 which includes all the clays found worldwide, typically mined. The chart in figure 2.13 a-d shows the process of selection of the clays. (Kogel et al., 2006)
STAGE 1: Reconnaissance
Property Negotiations Geological surveys Surface sampling and testing Preliminary market survey
Broad Product Categorization
Evaluation
Figure 2.13a Stage 1 of the selection process of mines (Kogel et at., 2006)
STAGE 2: EXPLORATION
Property Negotiations Exploration Drilling Detailed Testing Detailed Survey
Product Categorization
Resource Estimation
Preliminary Engineering Studies
Economic Studies
Pre Feasibility Study
Figure 2.13b Stage 2 in the selection process of mines (Kogel et at., 2006)
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STAGE 3: DELINEATION AND FEASIBILITY
Detailed (Delineation Drilling) Extraction of Bulk Samples Market surveys and negotiations
Detailed Testing Detailed Engineering Studies
Process Flow Sheet Design
Resource Calculation Pilot Scale Testing Market Product Testing
Economic Studies
Feasibility Study
Figure 2.13c Stage 3 in the selection process of mines (Kogel et at., 2006)
STAGE 4: DECISION TO INVEST
Construction
Commisioning
Figure 2.13d Stage 4 in the selection process of mines (Kogel et at., 2006)
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2.8.1 Sorting of raw material
This method applies to all ceramic raw materials and bodies such as clays, feldspars, pottery stone, silica sand, and other minerals that are brought in for testing. Clay samples collected from the mine ( about 5 kg) was placed in a metal tray and dried to remove any moisture that may have been accumulated from the mine. The dried samples were homogeneously mixed. . After being dried completely, batching was carried out to ensure that the clays were uniformly distributed. Batching was done via the cone and quartering method as shown in figure 2.14. The cone and quartering method begins by arranging all the clay samples into a pile, flattening the pile and dividing it into quadrants
(as shown in figure) Opposing quarters were combined and coned and quartered in the same manner, each time saving the rejected piles for further quartering. Quarter selection for combining was always the first and third quadrants, starting in the upper right in a clockwise direction. The second and fourth quadrants were always saved for later coning and quartering. This was carried out till all the samples were fully divided.
Figure 2.14 Coning and quartering method (Gerlach et al. 2002)
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2.8.2 Milling Process
Milling produces a particular particle size distribution and deagglomeration of fine powders. Milling is done in a jar mill as shown in figure 2.15 Physical processes include impact, shear between two surfaces, and crushing by a normal force between two hard surfaces. When a solid is fractured, energy is given off as heat from fracture, friction in the equipment, and energy necessary to create additional surface area. It is the energy from creating additional surface area that does the work sought. There are two broad types of ceramic raw materials that require milling. These are classified as lumpy and powdered ceramics. Lumps result from mining, fusion, and sintering. These are usually premilled by the supplier and are available in various screen sizes. Depending on your requirements, these may require further milling in the lab. Mined materials include talc, shale (clays), bauxite, and quartz. Fused materials include fused alumina, magnesia, mullite, and zirconia.
Figure 2.15 Typical Alumina fortified jar mill (King, 2002)
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Figure 2.16 Porcelain mill in a polymer encasement (King, 2002)
Milling is done in a ball mill with milling media. Milling is done in porcelain mills made from an alumina fortified porcelain. This is shown in figure 2.15 and 2.16
Composition of the media includes the following: porcelain, high alumina, pure alumina, TZP, MgO stabilized zirconia, silicon nitride, silicon carbide, steel, modified fused zircon,3 and a variety of mineral products such as flint, agate, or the material that is ground by itself (autogenous milling). Mineral products are cheap and can be surprisingly wear resistant. When processing fine ceramics, a general rule is to use the same composition of the media as that of the batch, if possible. For general lab applications, high alumina is perhaps the most commonly used media.
50
Depending on which media is selected, the size ranges from 1 mm to 3 inches in diameter. The choice of size depends on the material being milled. A general rule is to use the smallest size that has sufficient energy to fracture the particles in the batch. Most common shapes are spheres, satellite spheres, cylinders, and round-ended cylinders. Media with sharp edges should be prerun in the mill to round off the edges; otherwise, they will tend to chip and contaminate the batch.
Jar mills are filled about half full with grinding media. When the jar is over filled, there is not enough space for the media to tumble. When under filled, there is excessive media wear. Media that cascade with too much energy can chip or break. (King, 2002)
Halima in her paper noted that the milling time has an effect on the rheological properties of slip (Halima 2015).The milling time also has an effect on the fineness of the grains which will influence the sintering mechanism. This highlights the relationship between the size of powders and the rheological properties.
2.8.3 Viscosity measurement
Viscosity is a measure of the resistance of a slip to flow, or a liquid to shear. When pouring a slip out of a beaker, if the viscosity is high, it will pour slowly like molasses. When the viscosity is low, it will pour out like water. In both these cases, the flow rate is low and shear-like.
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Figure 2.17 Slip Rheology curves (King, 2002)
Figure 2.17 shows the different types of rheology that may be exhibited by slips.
Most slips are pseudoplastic in that viscosity decreases as the shear rate increases; this can be called shear thinning. The more one stirs these slips the thinner they become. Coarse grained slips are dilatant when the volume percent solid is high. A dilatant slip feels solid when poked. Tip the container and the slip will readily flow. One can observe this quality with corn starch in water as it forms a dilatant slip.
Viscous behavior is important in ceramic processing. With fine grained slips, the following factors control viscosity: volume % solids, deflocculant concentration, dissolved polymers, pH, particle size distribution, and ionic strength. Ionic strength is generally expressed as the concentration of an electrolyte in the slip. These are the variables one can work with; a combination of them determines the slip's processing properties. Dissolved polymers are often binders that will increase green strength and aid in pressing a part.
Temperature is also a factor as slips become thinner with an increase in temperature.
Milling often significantly increases the temperature of the slip; hence, before measuring viscosity, the slip should first cool to room temperature.
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2.8.4 Firing
Ceramics are sintered by raising them to a high temperature. This process consolidates the material, increases its strength, and usually causes it to shrink (King,
2002). The sintering of porcelain tiles is accomplished in roller kilns at maximum temperatures in the range of 1180°C-1240°C (Dondi et al. 2004) During firing, although the thermal reaction pathways may be different, in the end, similar phases are formed towards the stage of stable products (Aras 2004).
During firing, vitrification occurs (Martín-Márquez et al. 2008). During vitrification, the clays will be fused together to form a mass of fired body with lesser porosity with little to no spaces between them. When vitrification occurs, the materials will reorientate and rearrange themselves and shrink in the process. During this process also, the size of the material will shrink, and the excess moisture will be removed.
Densification occurs during the firing process by particle rearrangement and viscous flow that usually occurs above 1100°C. The sintering involves melting, pore coalescence and coarsening (Dondi et al. 2004).
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CHAPTER 3
METHODOLOGY
This study was carried out in a few major steps. These include site selection, experiments on the clays from the mines, property testing of porcelain tiles with different plastic clays included, and the determination of suitability of the clays in porcelain tiles. The research methodology is summarized in Figure 3.1 below.
Mine site selection by company
Experiments on clay properties from the different mines
Property testing of porcelain tiles with different plastic clays
Analysis to determine suitability of different plastic clays in porcelain tile body formula and characterization
Figure 3.1 Summary of research methodology
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3.1 Selection of mine site.
This study was conducted by using clays obtained from Batang Berjuntai in
Selangor ( 3.3329° N, 101.3658° E) , Paloh and Chamek in Johor (2° 11' 9.992" N 103°
11' 45.427" E and 2.1397° N, 103.2315° E respectively) and Mukah in Sarawak (2.8997°
N, 112.0934° E). The locations of these mines are shown in Figure 3.2, 3.3, 3.4 and 3.5.
Under the advice of the Ceramic Research Company (CRC), the research division of
Guocera Tiles Industry (GTI) under the Hong Leong bhd Group, these mine sites were chosen as the location for sample collection, due to the fact that these mine sites have an abundance of plastic clays.
Figure 3.2 Location of BB in Selangor
55
Figure 3.3 Location of Paloh (PJ) in Johor.
Figure 3.4 Location of Chamek (CJ) in Johor
56
Figure 3.5 Location of Mukah (MS) in Sarawak
3.2 Property testing of the clays
The period of the experimentation on the clay properties was carried out from
January 11th to February 5th 2016 at CRC to collect data on physical, chemical and mineralogical properties of the different clays.
3.2.1 Milling process
The dry sample from the mine is prepared into a slip by wet milling process using pot mills in a rapid mill, using alumina as the milling media. The samples are milled with deflocculants and water according to the specifications mentioned in the table 3.1 specified by CRC to obtain a clay slip by following the standards set by CRC. The amount of water and deffloculants added were determined via trial and error methods by the CRC, and are followed in this thesis to produce results that can be comparable to CRC standards.
Due to confidentiality agreements, the formula used for the porcelain tile body formulation
57 is not included in this thesis. But the method of milling is the same as that of pure clay samples; milling is carried out in a rapid mill until the residue weight fell within the range.
Table 3.1 Milling conditions for the clays
Clay (400g) Amount of Amount of deflocculant Milling time, water , % (STPP), g mins BB 70 % 1.2 18 CJ 60 % 1.0 22 PJ 60 % 1.0 14-18 MS 60 % 1.0 23-25
3.2.2 Slip Viscosity Measurement
The viscosity of the milled slip is measured by using a Ford cup and a stopwatch.
An image of slip in a Ford cup is shown in figure 3.5.
Figure 3.5 Ford cup with slip for viscosity measurement 58
The milled slips for clays and porcelain tile body is poured into the Ford cup while one hand holds the nozzle of the Ford cup closed. When the stop watch is started, the hand is simultaneously released and the time taken for the slip to break is measured. The breaking of the slip refers to the moment at which the slip does not flow smoothly, but starts to flow out in a non smooth manner.
Viscosity is a measure of the resistance of a slip to flow, or a liquid to shear. When pouring a slip out of a beaker, if the viscosity is high, it will pour slowly like molasses.
When the viscosity is low, it will pour out like water. In both these cases, the flow rate is low and shear-like.
3.2.3 Drying and pressing
After viscosity measurements of the various clay and porcelain tile slip formula are taken, the slip is dried to increase its green strength and prepare it for firing. The easiest method of drying that is used in ceramic laboratories is the pan drying method in the oven where the slip is simply poured into a stainless steel pan and left to dry in an oven that has a good exchange of air. During drying, the coarser particles will sink to the bottom and the slimes, which are very fine materials, will migrate to the free surface. In addition, the dissolved materials will also migrate to the free surface, creating a crust. When broken up, the crust will form a distribution of moderately hard agglomerates, which after sintering will shrink more than the rest of the body and create voids. The slip was dried in an oven overnight.
The test pieces of clay and porcelain tile formula were pressed in a rectangular block shape with dimensions of 200mm x 100 mm from the dried milled powders using a the GABTEC PRESS 110 TON (Serial No. : 1873, Year : 2013). Test pieces were used for
59
MOR measurement. 24g of crushed powder was weighed in a small plastic bag. This powder was used to produce buttons measuring 50mm button. The powders were crushed into buttons with pressure of about 270 bar. Buttons were used for physical property measurement such as shrinkage fired colour, weight loss and water absorption.
3.2.4 Firing
The clays are fired to a temperature of 1177°C to study the properties. This temperature is chosen based on preliminary studies carried out by CRC. The porcelain tiles are fired at three different temperatures to study the properties of the tiles at these different temperatures, which is at 1113.5 °C, 1120°C and 1127°C. These temperatures were achieved inside the furnace and determined by a thermocouple.
3.2.5 Fired Shrinkage and Weight Loss
The diameter of the dried test piece (before firing) was measured at two different locations using a pair of vernier callipers. The dried weight of the buttons was recorded as
W4. After the length measurements were taken, the buttons were fired in a muffle kiln at
1200oC with 10 minutes soaking. The fired test buttons are left to cool in the kiln until the temperature on the controller showed 300oC. The test buttons were completely cooled to room temperature. Then the diameter and weight of the fired test piece was measured again after firing and the fired shrinkage and weight loss was determined by calculation.
The fired shrinkage and weight loss will show what happens to the clay materials during the firing process.
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3.2.6 Fired Color
The fired color has an effect on the aesthetic value of the tiles produced. One of the main factors to consider when customers are buying tiles is the color of the tiles. Red firing tiles will affect the overall tile color when fired. The measurement of fired color is carried out via a calorimeter. The calorimeter will provide information on the redness, yellowness and the whiteness, by taking the a, b and L values from the calorimeter. A more positive a value means the sample is more red, while a negative a value shows a more green sample. A more positive b value shows a more yellow sample, and a more negative b value shows a more blue sample. The whiteness is indicated by the L value, where a more positive L value indicates more whiteness, whereas a more negative L value shows a darker and blacker color. The whiteness index, WI shows the brightness of the overall fired sample. Based on these values, the tiles are compared in terms of aesthetic value.
EN ISO 10545 - Part 16 is a standard used for Ceramic tiles to Determine small color differences. The test method used is the one described in the standard ASTM C-609, and measures small differences in color between an unknown sample and a reference tile; the standard specifies that this method should be used to measure only tiles that are solid color and smooth; with other tiles, the results may not be valid. The test is based on the use of a colorimeter which is first calibrated using a primary standard (magnesium oxide) or a secondary standard, depending on the indications of the supplier of the instrument.
Measures are then taken of the unknown sample and the reference sample, alternately, until three readings have been taken of every tile. Finally, the standard specifies the method to be followed to calculate differences of color, specifically as regards instruments that give the values in L, a and b to give the whiteness, redness and yellowness of the fired clays.
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3.2.7 Water absorption
Fired test buttons were used for this determination. This test was done only after the fired colour testing was complete. Weight measurements were taken before the samples were immersed in water. The test buttons were immersed in boiling water for two hours. After two hours, the specimens were removed from boiling water and placed in a warm water bath for 4 hours, ±15 minutes. After a total 6 hours of soaking in water, the weights were measured again and a formula (shown in Appendix ) was used to determine the water absorption. This allows sufficient time for the water to penetrate the open porosity to determine the porosity of the fired clays.
3.3 Characterization methods for porcelain tiles
In order to determine the properties of the porcelain tiles, several characterization techniques were used. This includes SEM, XRD, XRF and CTE analysis.
3.3.1 Scanning Electron Microscope (SEM) analysis
In the SEM study, the surface of the specimen to be examined is scanned with an electron bean and the reflected beam of electrons is collected, then displayed at the same scanning rate on a cathode ray tube. This study utilized a Field Emission Scanning
Electron Microscope (SEM), model Supra 35vp manufactured by Zeiss, Germany. The image on the screen which may be photographed represents the surface features of the specimen. The surface may or may not be polished and etched, but it must be electrically conductive. For non conductive materials a very thin metallic surface coating must be applied to the surface. To make the sample conductive, the clay powders were crushed
62 into a smaller size and were then mounted on the mount using carbon tape, with a light covering of the powder samples. The mounted samples were then coated with conducting material for an hour, to make the surface a conductor . Once the samples were coated, they were ready to be viewed under the SEM machine. The samples were placed in the sample holders in the machine. The controllers of the SEM were used to obtain the best and clearest view of the sample. The focus was adjusted to obtain maximum sharpness of the image, and once the desired image was obtained, the image was saved. The magnification used for these clay samples were 3000 and 5000 magnifications., although magnifications ranging from 10 to in excess of 50000 times are possible. The analysis centers on particle shape, size, agglomeration, and phase composition.
3.3.2 X-ray Diffraction (XRD)
Diffraction occurs when a wave encounters a series of regularly spaced obstacles that (1) are capable of scattering the wave, and (2) have spacings that are comparable in magnitude to the wavelength. Furthermore, diffraction is a consequence of specific phase relationships established between two or more waves that have been scattered by the obstacles. X-rays are a form of electromagnetic radiation that have high energies and short wavelengths—wavelengths on the order of the atomic spacing for solids. When a beam of x-rays impinges on a solid material, a portion of this beam will be scattered in all directions by the electrons associated with each atom or ion that lies within the beam’s path
One common diffraction technique employs a powdered or polycrystalline specimen consisting of many fine and randomly oriented particles that are exposed to monochromatic x-radiation. Each powder particle (or grain) is a crystal, and having a large
63 number of them with random orientations ensures that some particles are properly oriented such that every possible set of crystallographic planes will be available for diffraction.
Figure 3.6 Schematic diagram of an x-ray diffractometer; T= x-ray source, S= specimen,
C= detector and O = the axis around which the specimen and detector
The diffractometer is an apparatus used to determine the angles at which diffraction occurs for powdered specimens; its features are represented schematically in figure 3.6. A specimen S in the form of a flat plate is supported so that rotations about the axis labeled O are possible; this axis is perpendicular to the plane of the page. The monochromatic x-ray beam is generated at point T, and the intensities of diffracted beams are detected with a counter labeled C in the figure . The specimen, x-ray source, and counter are all coplanar. The counter is mounted on a movable carriage that may also be rotated about the O axis; its angular position in terms of 2θ is marked on a graduated scale.4 Carriage and specimen are mechanically coupled such that a rotation of the
64 specimen through is accompanied by a 2θ rotation of the counter; this assures that the incident and reflection angles are maintained equal to one another.
Figure 3.7 X-ray diffraction geometry
X-rays from a source pass through a monochrometer, collimated, and impinge upon the sample being analyzed. The sample is usually powderpacked in a rectangular holder, but can also exist as a film on a glass slide or a solid ceramic planer surface.
Interplaner spacings in the crystal lattice diffract the beam at different angles, producing a spectrum. A sketch of the geometry is presented in figure 3.7.
3.3.3 Coefficient of thermal expansion
Ceramic tiles have expansion coefficients similar to those of other construction materials, but may be subject to much greater temperature oscillations which makes it necessary to know and take into account the expansion of the ceramics (Spanish Ceramics 65
Institute, 2011)
ISO standard ISO 10545-8 contains the test method used to measure the coefficient of thermal expansion of a ceramic tile. The test takes place in a dilatometer, which subjects the test piece to a heating process of 5°C/min up to 100°C. For the determination of the fired coefficient of expansion, the raw samples are cut into test pieces at the length range from 60mm – 65mm with about 7 mm in diameter and flattened edges at both sides.
The strips were then fired in a muffle kiln at the required temperature given. The fired strip was then cooled to ambient temperature, then ground to the length range 30mm
– 50mm and about 6mm in diameter. The length was then measured with vernier callipers and determined the length to accuracy of 0.002 times the length, and keyed in the reading as measured into the programmer. The test piece was then oven dried at about 600C before analysis was carried out.
The measurement was carried out is per the dilatometry operation method. The heating rate was programmed at 10oC/min and to about 530o C. The calculations for the determination of coefficient of linear thermal expansion are based on equation as mentioned in Appendix A.
The gradient of the graph generated provides the thermal expansion coefficient of the samples. This shows the changes in length in meters that occur per meter of the material with changing temperature.
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CHAPTER 4
RESULTS AND DISCUSSION
4.1 Introduction
The results and discussion are separated into two portions, the portion that deals with the raw material properties, and the portion that deals with the properties of the clay tile when put into the porcelain tile formula. The results obtained from these two sections will gauge whether the clays being studied are suitable to be used in the tile manufacturing process.
4.2 X-Ray Fluorescence (XRF) of clay
Table 4.1 shows the XRF analysis results for the four clay samples. The XRF analysis is done to determine the mineral content in the clay.
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Table 4.1 XRF analysis results of the clays
BB Clays CJ Clays PJ Clays MS Clays Mineral % % % %
Na2O-C 0.053 0.115 0.204 0.157 MgO-C 0.602 0.399 0.474 0.377
Al2O3-C 24.600 18.029 24.040 19.139
SiO2-C 59.914 68.639 57.583 68.156
P2O5-C 0.031 0.020 0.014 0.025
K2O-C 1.684 1.816 2.094 1.056 CaO-C 0.006 0.046 0.105 0.039
TiO2-C 1.017 0.619 0.593 1.014 MnO-C 0.005 0.013 0.007 0.002
Fe2O3-C 1.788 3.337 5.511 0.951
Cr2O3-C 0.012 0.003 0.005 0.008 ZrO2-C 0.032 0.039 0.052 0.039 HfO2-C 0.004 0.003 0.000 0.002 SO3-C 0.000 0.000 0.000 0.000 SrO-C 0.004 0.002 0.004 0.005 LOI 10.038 7.053 9.343 8.437 Total 100 100 100 100
The minerals present in the clay are responsible for the properties of the final end product. For example, the Fe2O3 is responsible for the reddish color of the fired clays.
(Sengphet et al 2012) Based on the XRF results obtained below, the PJ clays have the highest Fe2O3 content at 5.511 %, followed by the CJ clay, BB and MS with the least
Fe2O3 content, with 3.377 %, 1.778 % and 0.951 % respectively. This means that when burnt, the PJ clays will have the deepest color, followed by the CJ clay, BB clay, and the
MS clay will burn with the brightest color. This statement was proven true by the fired color results of the clay which showed that the MS clays burnt with the brightest color, followed by the BB clays, and the PJ clays had the most red and darkest color when fired.
The works of Sengphet and team also obtained similar results, that is the clays with more
Fe2O3 will burn with a more red color (Sengphet et al. 2012). Other constituents such ad
Cao, MgO, Mno and TiO2 are also responsible for the fired color of clays (Sengphet et al.
68 n.d.) By looking at the results in the table 4.1, the content for Cao, MgO, Mno and TiO2 in the MS clays are less compared to the BB, CJ, and PJ clays. Therefore the MS clays burn with a lighter color compared to the other clays, and these results correspond to the fired color results obtained in section 4.8.
4.3 Scanning Electron Microscopy (SEM) of clays
Figure 4.1 shows the SEM images of the different clays taken under 3X and 5X magnification.
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Clays
Quartz
BB
CJ
Kaolinite
PJ
Kaolinite
MS
3000 5000
Magnification (x)
Figure 4.1 SEM images taken under 3X and 5X magnification
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The series of images in figure 4.1 show the Scanning Electron Microscope images for the different clays being studied. According to Bergaya and Lagaly, there are several types of clays present within each type of clay (Bergaya & Lagaly 2006). The SEM images of the MS clays show a microstructure that is abundant with kaolinite and illite microstructure. Kaolinite is distinguished by its white or whitish colour of microstructure.
(Murray 2000). The shape of the kaolin can be described as pseodu-kexagonal along with plates, some larger books and some vermicular stacks. The different coarseness of kaolin will affect the physical and optical properties. Although kaolinites have a variety of traditional and modern uses, due to its properties, the main use of kaolinite is in the ceramics industry due to its whiteness, and refractory behavior. On the other hand, illite occurs as aggregates of small, monoclinic grey to white crystals.
The SEM image of the BB clays show an occurrence of more quartz phase in the microstructure. This is characterized by the appearance of arrowhead or triangular form, similar to the ones observed by Mancktelow, Grujic and Johnson in their work
(Mancktelow et al. 1998). Silica sand is a strong granular material, with its main materials being quartz (Shi et al. 2016). Quartz is a common mineral with the same chemical composition but quartz and silica are not synonyms. The properties that the quartz lend to the final product are that they are nearly infusible, quite non-plastic and have a very little shrinkage, in addition to being of low tensile strength. This is obviously seen in the results of the firing of the clays, where the BB clays, with a higher percentage of quartz exhibit less fired shrinkage compared to the other clays.
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4.4 X-ray Diffraction (XRD) of clays
The series of images below show the XRD plots obtained for all the clays. Based on the plot, it can be seen that all the clays possess quartz and kaolinite as their main clay constituent. It is no surprise as quartz are the most abundant clay forming component.
K – Kaolinite
Q – Quartz
Figure 4.2 XRD plot of the BB clay
The XRD plot for the BB clay is shown in figure 4.2. The BB clay picked up peaks of quartz (ICDD number: 98-000-5727 98-000-5885 and 98-000-6046), and kaolinite
(ICDD number: 98-001-2782 and 98-001-2946) more than the MS clays. The kaolinite will provide a good plasticity and exhibit good refractory behavior when fired, which is also reflected in the other physical property results obtained in earlier sections. The quartz will act as a filler in the system, (Martín-Márquez et al. 2010) however the huge presence of quartz in the system will cause closed porosity to increase before the open porosity disappears (Das et al. 2005)
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K – Kaolinite
Q – Quartz
K K
Figure 4.3 XRD plots of the CJ clay
The XRD plot for the CJ clays is shown in Figure 4.3. Similar to the other clays, the peaks detected are that of quartz (ICDD number: 98-000-5727, 98-000-5885 and 98-
000-6046) and kaolinite (ICDD number: 98-001-2752). The quartz and kaolinite present is in a hexagonal shape.
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K – Kaolinite
Q – Quartz
Q
Q K
Figure 4.4 XRD plot of the PJ clay
The XRD plot in figure 4.4 shows the composition of the PJ clay by looking at the composition of the PJ clay, the main composition are hexagonal quartz (ICDD number :
98-000-5727 and 98-000-5885). The PJ clay also has a small amount of the kaolin (ICDD number: 98-000-2782) phase present in it. Since it consists mainly of a small amount of kaolinitic clays, the fired color is not as bright as the BB or MS clays (Zanelli et al.
2015a). Kaolinitic clays are versatile industrial materials that are generally used as fillers or raw materials in ceramics, plastics, paints, paper, rubber and a variety of other applications (Ariffin et al. 2008). The idealized structure of the kaolinite mineral is that of a single sheet of hydroxyls octahedrally coordinated to aluminium cations linked to a single sheet of oxygen tetrahedral centred by silicon atoms (Zbik & Smart 1998). The more important properties that kaolin and ball clay impart to ceramics are plasticity, green strength, dry strength, fired strength and color, refractoriness, ease of casting in sanitaryware, low to zero absorption of water, and controlled shrinkage (Murray 2006).
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K – Kaolinite
Q – Quartz
Q K K K
Figure 4.5 XRD plot of the MS clay.
The XRD plot for the MS clays is shown in figure 4.5. The MS clay is made up of more quartz phase (ICDD number: 98-000-5727 and 98-000-5883), and a large amount of kaolinite (ICDD number: 98-001-2782). The amount of quartz accounts for most of its behavioral properties, such as low fusibility and high shrinkage values. Seeing as quartz is the most common sand-forming mineral this corresponds to the XRD plot obtained (Anak
Ginung & Abdullah 2015). The large amount of kaolinite corresponds to the fired color of the MS clays which fires to a bright white color (Zanelli et al. 2015a).
4.5 Raw Material Milling Behaviour
Table 4.2 illustrates the physical properties of the clays from the four mines (BB, CJ, PJ,
MS).
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Table 4.2 Properties of the milled clays
Type of clay Milling time Residue weight Viscosity (s) Density of slip (min) (g) (g/cm3) BB 18 1.05 14 1.56 CJ 25 1.06 25 1.63 PJ 30 1.06 39 1.62 MS 28 0.98 13 1.60
Based on the table 4.2, the milling time increases in the order of BB, C, M, P, with milling time of 18 min, 25 min, 28 min and 30 min respectively. The milling times were obtained by a trial and error method, to see which milling time produced the desired residue of between 0.8-1.05 (g), and these milling times are recorded in table 4.3.
Although milling time varies from batch to batch, these results indicate that just by looking at the milling time, the PJ clays contain the most amount if hard materials and are the toughest. The milling time is a measure of the hardness of the clay. The longer the milling time, the harder the clays, because a longer time is used to crush the clay to the required size (Vdovic et al. 2010; Halima 2015).
The values of the residues were 1.06g for both the Chamek and Paloh clays,
10.5g and 0.98 g respectively for the Batang Berjuntai and Sarawak clays. The density of the clays does not show much variation, varying between the values of 1.56-1.63 g/cm3.
The viscosity is a measure of the ability to flow of the slip. The viscosity increases in the order of MS, BB, CJ and PJ clays, with viscosity of 23s, 14s, 25s and 39s respectively. Halima in her paper noted that the milling time has an effect on the rheological properties of slip (Halima 2015).The milling time also has an effect on the fineness of the grains which will influence the sintering mechanism. This highlights the relationship between the size of powders and the rheological properties.
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4.6 Water absorption results
Table 4.3 shows the weight measurement results which were used to calculate the water absorption of the clays. Water absorption measurements were taken by calculating the difference in weight between fired samples and soaked samples.
Table 4.3: Weight measurements of the clay samples
Type of clay Weight after Weight Weight Weight Water drying, W4 after loss, % after absorption, (g) firing, W5 soaking, W6 % (g) (g) BB 23.08 21.12 8.49 22.17 4.97 CJ 23.09 21.85 5.37 21.96 0.503 PJ 22.82 21.05 7.76 21.09 0.19 MS 22.95 21.38 6.84 23.73 10.99
The water absorption of the PJ clay was the least, with 0.19 % water absorption, as compared to the MS clay which had a water absorption of 10.99 %. The BB and CJ clays had water absorption of 4.97 and 0.503 respectively. One of the properties of porcelain tiles are characterized by the low porosity. The lower the porosity, the more desirable the characteristics. This is reflected by the weight loss and water absorption characteristics of the clays. Densification also happens during sintering which causes changes in shape after firing (Dondi et al. 2004). During firing, vitrification occurs, and water loss will occur as well (Martín-Márquez et al. 2008). Porcelain tiles are defined as tiles with porosity of close to zero, to be more precise they have porosity less than 0.1%. (Galos 2011a)
Therefore, in the study of clays, the lower the water absorption indicates a lower porosity.
This will make it more suitable to be added into a porcelain tile formula. Therefore, the water absorption properties are an important consideration to look at when carrying out the screening process of clays. By this logic, the PJ clays exhibit the lowest porosity, because the value of water absorption is the least among the four clays.
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4.7 Fired Shrinkage measurement
Table 4.4 shows the length measurements of the clay buttons before and after the firing process. The changes in the length of the samples can give us a measurement of how much the tiles shrunk or expanded in the furnace during the firing process.
Table 4.4 Length Measurements of the clay samples
Samples Dried Weight, L1 Fired Weight,L2 Fired Shrinkage (%) (mm) (mm) 1 2 1 2 1 2 Average BB 50.21 50.21 46.34 46.32 7.71 7.75 7.73 CJ 50.30 50.31 45.58 45.60 9.38 9.36 9.37 PJ 50.22 50.22 45.28 45.29 9.84 9.82 9.83 MS 50.23 50.20 47.99 48.01 4.46 4.36 4.41 `
The fired shrinkage for the clays increased in the order of MS, BB, CJ and PJ with the average fired shrinkage of 4.41%, 7.73%, 9.37% and 9,83% respectively. The CJ and
PJ clays show the most fired shrinkage in terms of the reduction of the diameters of the button. This is followed by the control sample of BB with a fired shrinkage of 7.73 %. The
Sarawak clay has the least value of fired shrinkage of 4.41%. This means that during the firing process, the MS clay has the least change in its shape. This may be due to the microstructure of the clays, as explained by Murray (Murray 2006). He observed that the drying and firing processes will cause shrinkage in the samples. During firing, vitrification occurs (Martín-Márquez et al. 2008). During vitrification, the clays will be fused together to form a mass of fired body with lesser porosity with little to no spaces between them.
When vitrification occurs, the materials will reorientate and rearrange themselves and shrink in the process. During this process also, the size of the material will shrink, and the excess moisture will be removed. Densification occurs during the firing process by particle rearrangement and viscous flow that usually occurs above 1100°C. The sintering involves melting, pore coalescence and coarsening (Dondi et al. 2004), which contributes to the 78 shrinkage of the samples once fired.
However, the presence of kaolinite in the clay will cause controlled shrinkage of clay. Santos-Barbosa demonstrated that during shrinkage, the sample will undergo a significant reduction in its size (Santos-Barbosa et al. 2013). The works of Martín, Rincón and Romero have told us that the porosity of the fired sample is directly linked other properties such as the linear shrinkage and the water absorption (Martín-Márquez et al.
2008). Therefore, the fired shrinkage can be linked to other properties such as water absorption and porosity. This will also affect other properties such as the hardness, bonding strength, abrasion resistance and other mechanical properties of the sample
(Manfredini et. al, 1995).
4.8 Fired Color
Table 4.5 below shows the results of the fired color of the clay samples
Table 4.5 Fired Color of the clays
Sample L value a value b value Whiteness Index, WI BB 74.67 4.22 20.78 -84.05 CJ 38.74 12.31 10.34 -110.48 PJ 37.65 9.33 9.14 -100.3 MS 82.62 3.12 13.76 -10.28
The color of the samples become darker and intensifies after firing. By taking a look at the BB, the whiteness value is 74.84, the a value is 4.22, the b value is 20.78 and the whiteness index is -84.05. Based on these values, the BB clays have a light color when fired. This makes it suitable to be dyed with other colors to give it an attractive color. The
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CJ and the PJ clays yet again exhibit similar characteristics when it comes to the fired color. The difference in the whiteness, redness and the yellowness is very slight. The L, a, b and WI values for the CJ and the PJ clays are 38.74, 12.31, 10.34, -110.48 and 37.65,
9.33, 9.14, and -110.3 respectively. The fired color of these two samples are not as white as the BB clays, but they are not too dark either as compared to the Sarawak clays, which have L, a, b and WI values of 82.62, 3.12, 13.76 and -10.28. This depicts very dark colored sample upon firing. Table 4.5 illustrates the fired color of the clays
The color may be affected by the amount of kaolin present in the clay. The brightness of kaolin changes during firing. From about 350 °C to 800 ° C, the brightness of kaolin will reduce generally. Above this temperature, the brightness increases with the firing temperature under oxidizing conditions because of iron going into the structure of the phase (Agrawai P., 2013). Murray also observed that the particle size also effected the fired whiteness (Murray 2006).
4.9 Modulus of Rupture (MOR)
Table 4.6 shows the MOR values for the clays
Table 4.6 Dry MOR values for the clays
Clays Dry MOR value (N) BB 44 CJ 39 PJ 22 MS 40
Based on the MOR values shown in table 4.7, the BB clay has the highest dry
MOR value, of 44 N, followed by the Sarawak clay, CJ clays and finally the PJ clays, with
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MOR values of 40 N, 39 N and 22 N respectively. This means that the BB clays have the highest unfired strength, followed by the MS Clays, CJ clays, and the PJ clays have the least unfired strength. The major function of plastic clays is to provide the dry strength to the unfired green body, and strength even after firing (Galos 2011a). Therefore the plastic clay needs to have a high dry MOR value. The higher the dry MOR value, the better its green strength. Green strength is measured as the transverse breaking strength of a test bar suspended on two narrow supports in pounds per square inch or kilograms per square centimeter. Green strength has to be adequate for the piece to be handled without bending or breaking. Ball clays, which are finer in particle size than most kaolins, have a higher green strength (Murray 2006).
The works of Cavalcante et al studied the properties of white porcelain stoneware with different microstructure (Cavalcante et al. 2004). The MOR may be affected by the microstructure of the sample. The presence of quartz in the sample will have a negative effect on the strength. It will reduce the mechanical properties performance. Mullite of zircon will increase the mechanical performance via matrix reinforcement, while quartz plays an opposite role. Martin-Marquez observed that the strength is dependent on the number or open porosity of the sample (Martín-Márquez et al. 2010). This is related to the water absorption.
4.10 Coefficient of Thermal Expansion (CTE) results.
Materials expand and contract with changes in temperature. The ratio that a material expands in accordance with changes in temperature is called the coefficient of thermal expansion. This varying expansion and contraction is measured with a
81 dilatometer. The expansion of the material is a critical performance attribute in considering its use for various applications. Characterization of phase changes of clay provides key insight into the material’s performance before, during, and after firing. The
CTE curves will provide the fired behavior of the clays. The purpose of the CTE is to determine the thermal expansion of the material when subjected to high temperatures in the kiln or furnace. This is an important criterion as well to determine the outcome of the size of the fired tiles.
Ceramics generally have strong bonds and light atoms. Thus, they can have high frequency vibrations of the atoms with small disturbances in the crystal lattice. The result is that they typically have both high heat capacities and high melting temperatures.As temperature increases, the vibrational amplitude of the bonds increases, and increases the
CTE value. Compared to other materials, ceramics with strong bonds have potential energy curves that are deep and narrow and correspondingly small thermal expansion coefficients.
Based on the CTE curves for all the clays, they showed a steady increase in size from the temperature range 50-500OC (see Appendix). The CTE for BB is 65.8ε-7 °C-1, CJ is 83.5ε-7 °C-1, PJ is 63.0 ε-7 °C-1, and 79.0 ε-7 °C-1 for the MS clays. The expansion coefficient for the CJ clays is the highest, followed by the MS, BB and finally PJ clays.
Coefficient of thermal expansion measurements are carried out to determine the appropriate fit of the glaze to the tile body. A large coefficient of thermal expansion in the glaze with respect to the body can cause crazing which will make the tiles produced defective, which will translate as losses in a large manufacturing plant. Therefore, it is desirable to obtain a tile with a lower CTE value, which is why the CTE for the PJ clays is the most desirable.
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4.11 Comparison of clay properties
The table 4.7 shows the comparison of all the properties of the clays after firing.
Table 4.7 Comparison of all the properties of the fired clays
Properties BB clay PJ Clays CJ Clays MS Clays Fired Shrinkage 7.73 9.82 9.44 4.37 Water Absorption 4.45 0.20 0.57 11.10 Weight loss 8.05 7.74 5.39 6.81 L 74.67 37.65 38.74 82.62 A 4.22 9.33 12.31 3.12 B 20.78 9.14 10.34 13.76 WI -84.05 -100.03 -110.48 -10.28
By looking at the fired shrinkage, the shrinkage of the MS clays is the least, with a shrinkage of only 4.37 %, as compared to the BB clay with a fired shrinkage of 7.73 %.
The PJ and CJ clays have almost similar shrinkages of 9.82 % and 9.44 % respectively.
The fired shrinkage is an important property because it will determine whether or not the final tile produced conforms to the standards set by the company when manufacturing.
The water absorption should be as low as possible, because these clays will be used in the porcelain tile body formula, and the characteristic of the porcelain tile is that the water absorption is less than 0.01 %. By looking at the results, the PJ clays are the most fused or vitrified clays, with a water absorption of only 0.2 %. This means that during the firing process, the clays are fused more closely together. Even the control clay has a water absorption of 4.45 %, which is even higher than the CJ clays with a water absorption of
0.57 %. The MS clays again have an extremely high water absorption, which is 11.10 %.
This indicated that it behaves more refractory rather than a vitrified body.
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4.12 Comparison of the milling results of porcelain tiles
The table 4.8 shows the properties of milling time, residue weight, viscosity and the density of the slip for the porcelain tiles.
Table 4.8: Properties of the milled porcelain tile using different plastic clays
Clays used in Milling time Residue weight Viscosity (s) Density of slip porcelain tiles (min) % (g/cm3) BB 19 0.95 19 1.72 CJ 19.5 0.85 18 1.70 PJ 21 0.88 19 1.70 MS 19 1.02 17 1.69
The milling time for the porcelain tiles using the different clays is within 19-21.5 minutes. Taking a look at the control tile using clays from BB, the milling time is 19 minutes, to produce tiles with viscosity of 19s and have a residue weight % of 0.95. The milling time of the MS clay is also 19 minutes, but it produces a viscosity of 17s and a residue weight of 1,02%. The CJ clay has a milling time of 19.5 min and the PJ clay has the longest milling time of 21 minutes.
By comparing this milling time to the milling time of the clay bodies, the milling time for the porcelain tiles is shorter than the pure clay bodies. This is due to the interaction between the studied clays and the other clays, fillers, binders, and additives added. In both cases though, the Pjclays took the longest milling time, indication that the
PJ clays are the hardest among the four clays being studied. However having said that, looking at the dry MOR of the PJ clays, it is the weakest among the four clays.
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4.13 Porcelain tile property
Table 4.9 shows the properties of the porcelain tiles. These porcelain tiles were fired at three different temperatures, To make it easier for analysis purposes, the properties of the clays are classified according to the firing temperature, then the properties are compared.
Table 4.9: Properties of porcelain tiles fired at 1113.5OC
Properties/Tile BB CJ PJ MS Fired Shrinkage 7.82 7.52 8.05 7.85 Weight Loss 3.72 3.25 3.56 3.44 Water 0.38 0.15 0 1.74 Absorption L 63.03 53.97 50.47 67.41 A 3.89 5.08 6.13 4.48 B 10.77 10.16 10.01 10.57 WI -40.60 -59.65 -67.97 -27.60
The main property to be looked here at for porcelain tiles is the water absorption
(Martín-Márquez et al. 2008). The water absorption test results will determine the amount of porosity of the fired tile. The lower the water absorption value, the lower the porosity of the fired tile, and vice versa. Ideally, the porcelain tile should obtain zero percent porosity, to signify complete vitrification of the raw materials during the firing cycle. Any porcelain tile formula that can attain this porosity level is considered good. By looking at the data in the table below, the porcelain tile using the PJ clay has a porosity of zero percent when fired with 1113.5OC temperature. This is followed by the porcelain tile made from the CJ clay that has a porosity of 0.15 %. The control tile using the BB clay, has a high porosity value of 0.38 %, which shows it behaves more as a refractory rather than a vitrified body, rendering it unsuitable to be classified as a porcelain tile. The MS clay porcelain tile has the highest porosity level, with 1.74 % level, the least desirable value. After taking a look
85 at the porosity of the tile, only then other properties of the tile are taken a look at. In terms of the fired shrinkage, there is a slight variation between the fired shrinkages of all the four porcelain tiles, with values ranging from 7.52-8.05 % of fired shrinkage. These values fall within the acceptable limit for the fired shrinkage. The weight loss for all the porcelain tiles also have very little variations between them, from 3.25-3.72 % weight loss. This corresponds to the burning off of organic matter present in the different types of clays.
The aesthetic value of the tiles are also another consideration to be considered, and are recorded by the L,a,b and WI values below. A more positive a value means the sample is more red, while a negative a value shows a more green sample. A more positive b value shows a more yellow sample, and a more negative b value shows a more blue sample. The whiteness is indicated by the L value, where a more positive L value indicates more whiteness, whereas a more negative L value shows a darker and blacker color. The whiteness index, WI shows the brightness of the overall fired sample. Based on the results shown below, there is some variation in the color values when compared to the control tile. The control tile burns with a brighter color, but the MS clay burns with an even brighter color than the control. However, the PJ and CJ clays burn with a more reddish- brown color as compared to the control tile. This shows that one of the things that customers look at when purchasing items are the aesthetics of the product as mentioned in the works of Chang et.al that studied this (Chang et al. 2014).
The table 4.10 shows the properties of the tiles fired at temperature 1120°C. This is the temperature that is being used currently by GTI to fire the porcelain tiles for manufacturing in the plant.
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Table 4.10 Properties of porcelain tiles fired at 1120OC
Properties/Tile BB CJ PJ MS Fired Shrinkage 8.06 7.76 7.85 7.78 Weight Loss 3.8 3.35 3.63 3.54 Water 0.15 0.08 0.02 1.02 Absorption L 62.30 53.60 50.28 65.88 A 3.66 4.82 5.79 4.03 B 10.28 9,75 9.63 9.89 WI -38.53 -56.79 -64.71 -26.56
The table 4.10 shows the properties of the tiles fired at temperature 1120°C. Again, by looking at the water absorption, there are two tiles that showed almost zero porosity, which is desirable in porcelain tiles. Generally by definition, porcelain tiles are an tiles that have less than 0.1% porosity (Dondi et al., 2004) From the second firing cycle, the tiles that have this property of porosity less than 0.1% are the tiles using the PJ and the CJ
Clays, with 0.02 and 0.08 % porosity respectively. However, unusually enough, the control tile did not exhibit zero porosity. The porosity was slightly high and unacceptable at 0.15%. For the MS clay, the porosity level is still high, with a value of 1.02 %, which is characteristic of floor tiles.
As the temperature increased also, the weight loss of the tile also increased. The weight loss increased in the order of CJ, MS, PJ and BB, with weight loss values of
3.35%, 3.54%, 3.63%, and 3.8% respectively. This is corresponding to higher amount of organic material being burnt off during the firing process. The shrinkage also increased as the temperature increased, because the higher temperature allowed for more compaction during the fusion process that occurs between the clayey materials in the tile compact.
Shrinkage increased in the order of CJ clay with 7.76%, MS with 7.78%, PJ with 7.85%< and BB with the highest shrinkage of 8.06%.
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The table 4.11 shows the results when the different porcelain tiles when fired at a temperature of 1127°C, which is a higher temperature than the temperature used in manufacturing.
Table 4.11 Properties of porcelain tiles fired at 1127°C
Properties/Tile BB PJ CJ MS Fired Shrinkage 8.14 7.99 7.82 8.19 Weight Loss 3.96 3.81 3.5 3.73 Water 0.03 0 0 0.49 Absorption L 61.60 49.79 53.16 64.67 A 3.53 5.87 4.72 3.69 B 10.16 9.95 9.74 9.59 WI -39.37 -69.58 -57.96 -26.56
This time when fired, the porosity of three of the tiles was zero, which is the tiles made using the BB clay, PJ clay and the CJ clay. The tiles made using the MS clay still had a high water absorption of 0.49 % . Again, since the temperature was higher, the weight loss and the fired shrinkage was more than the previous temperatures. A higher temperature means more movement and fusibility of the clay materials.
4.14 Modulus of Rupture (MOR) of porcelain tiles
Table 4.12 shows the results of the dry MOR carried out on the porcelain
tiles.
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Table 4.12 Dry MOR values for the porcelain tiles using different clays
Different clays for the porcelain tiles Dry MOR value (N) BB 28 CJ 26 PJ 25 MS 23
Based on the results in table 4.12, all the clays in the porcelain tile exhibit
MOR within this range of 25-30 N. These values are in compliance with the
standards brought forward by GTI and CRC. Although the new clays do not provide
MOR as high as the BB clays, certain steps can be taken to improve the MOR of the
ew clays. In order to improve the MOR of the clays, more binders such as Bentonite
could be added into it, and the MOR and other property measurements have to be
taken again. Green strength has to be adequate for the piece to be handled without
bending or breaking (King, 2002; Murray 2006).
4.15 Comparison of properties of porcelain clays
The table 4.13 shows the comparisons of all the properties of the porcelain
clays fired at different temperatures. This table will give us a better overview of the
properties of the porcelain tiles.
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Table 4.13 Comparison of the properties of the porcelain tiles fired at different
temperatures
Firing Properties Batang Paloh clays Chamek clays Sarawak Temperature Berjuntai clay clays 1113.5 OC Fired Shrinkage 7.82 8.05 7.52 7.85 Weight loss 3.72 3.56 3.25 3.44 Water Absorption 0.38 0 0.15 1.74 L 63.03 50.47 53.97 67.41 A 3.89 6.13 5.08 4.48 B 10.77 10.01 10.16 10.57 WI -40.60 -67.97 -59.65 -27.60 1120 OC Fired Shrinkage 8.06 7.85 7.76 7.78 Weight loss 3.8 3.63 3.35 5.54 Water Absorption 0.15 0.02 0.08 1.02 L 62.30 50.28 53.60 65.88 A 3.66 5.79 4.82 4.03 B 10.28 9.63 9.75 9.89 WI -38.53 -64.71 -56.79 -26.33 1127 OC Fired Shrinkage 8.14 7.99 7.82 8.19 Weight loss 3.96 3.81 3.50 3.73 Water Absorption 0.03 0 0 0.49 L 61.60 49.79 53.16 -64.87 A 3.53 5.87 4.72 3.69 B 10.16 9.95 9.74 9.59 WI -39.37 -69.58 -57.96 -26.56
The first property to consider other than the MOR is the water absorption. As mentioned in the literature review, the water absorption of the porcelain tiles should be less than 0.01 % (Santos-Barbosa et al. 2013). Therefore the tile formula that achieves this criteria first is more desirable. By looking at the different firing conditions, the PJ clays achieve the desired porosity at the lowest firing temperature of 1113.5OC. This is even better than the BB porcelain tile that only achieved less than 0.01 % porosity at a temperature of 1127OC. The CJ clay achieved less than 0.01 % porosity at a temperature of 1120OC.
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Comparison of other properties at this porosity is compared. For the dry MOR values of the clay, the BB, PJ and CJ porcelain tiles exhibited almost similar values, that is
28, 26 and 25 N respectively. Although the CJ clay exhibited slightly lower MOR value, this can be rectified by adjusting the formula and adding in some binders such as bentonite that will make the MOR value increase. Bentonite is currently being used on a large scale in the tile manufacturing process, but trial runs need to be carried to determine if the addition of more bentonite will affect any other properties drastically. By looking at the overall properties of the MS clays, it can be said that it is the least suitable to be used in the manufacturing process to replace the current BB clays in the tile formulas. And the PJ clays seem to be the most promising, because they achieve zero porosity at a relatively lower temperature than the production. This would save up on time and cost in the long run if it is used for mass production. The fired shrinkage of the PJ clays at 1113.5OC are very similar to the BB clays at 1127OC, with the PJ clays having a shrinkage of 8.05 %, and the BB clay having a shrinkage of 8.14 %. This means that there is little difference in the size of the tile after firing, therefore it will have little to no effect on the production in factory. Even the weight loss between the two have little differences between them. It is sufficient to say that the MS clays do not even achieve zero porosity at the high temperature of 1127OC. To increase the temperature further to reduce the porosity would mean an increase in the firing temperature or the firing time, which would constitute to a waste in time and cost. This is not feasible in a large scale manufacturing process that focuses on saving cost and energy in the long run.
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CHAPTER 5
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion
Based on the results obtained, the closest clays that can substitute the current clays are the CJ and PJ clays, both originating from Johor. The properties of these two clays are almost similar to the BB clays, and in fact exhibit even better firing properties when placed in the body formula. The porosity of the CJ clay when fired at reached a zero porosity at a lower temperature than the control clay. This will enable the firing temperature to be reduced, which leads to energy and cost saving. The PJ clays obtained a porosity of zero at the same firing temperature at a lower temperature than the control as well. In fact, the BB clays only obtained a zero porosity at a higher temperature than the one commonly used in industry. The zero porosity is characteristic to the porcelain tile.
Therefore, obtaining a zero porosity makes these clays more suitable to replace the current clay. Based on the results obtained from the MS clays, it is the most unsuitable to replace the current clays. In addition to it not achieving zero porosity even at higher firing temperatures, the fired color was also much darker than the control.
However, the main property for plastic clays is to provide unfired strength to the green body. This is gauged by the dry MOR value. Therefore, in addition to having zero porosity when fired, the clays need to have a high dry MOR value. Based on the results, all the clays exhibited almost similar dry MOR values. The control had the highest dry
MOR value, followed by the Paloh, Chamek and Sarawak clays. However, since the difference between the MOR values are not too big, all these clays can be considered for use, based on the MOR alone. To increase the MOR value, additives such as bentonite binders may be added to improve the MOR.
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As a conclusion, based on the MOR values alone, the MS, CJ and PJ clays are able to replace the BB clay being used in production. But based on the water absorption of the porcelain tiles, only the PJ or CJ could be used to replace the BB clays. But before these changes can be made, other considerations need to be taken into account. Physical properties need to be considered such as the physical properties, water absorption, fired color and shrinkage. In addition to these properties, there are also other factors to be considered, such as the transportation of the clays and its cost. In the case of the MS clays, it is extremely costly to ship the clays all the way from Sarawak. Other than that, the availability in the long run is another consideration. The clays chosen need to be able to sustain production for many years before the supply runs out. Other factors that need to be considered are other properties such as the pyroplasticity, which is the ability to be fired without distortion and warpage. Unfortunately those criteria were not able to be completed in this study.
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5.2 Recommendations for future works
Therefore the researcher would like to suggest that for future works, a comprehensive study of the clay properties is carried out, rather than just the basic property testing that was done in this study. Properties of the porcelain tile such as the
Coefficient of Thermal Expansion (CoE), Thermal analysis (via TG/DTA), pyroplasticity index, Loss of Ignition (LOI) can be carried out to determine with extreme certainty on the choice of clay to be used to replace the BB clays. Once these are done, more comprehensive property tests can be done when the Sarawak and Johor clays are used to produce floor and wall tiles, to see if these clays are suitable to be used as floor and wall tiles, instead of just using these tiles for porcelain tiles.
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APPENDIX A
Appendix A shows the list of formulae used in the thesis
W1−WO 1.푀표𝑖푠푡푢푟푒 푐표푛푡푒푛푡 = W1−W2
Where
Wo = Weight of the empty bowl
W1 = Weight of the bowl and 20g of powder
W2 = Weight of bowl and powder after drying in the oven
W4−W5 2.푊푒𝑖𝑔ℎ푡 푙표푠푠 = × 100 W4
Where W4 = dried weight
W5= fired weight
L1−L2 3.퐹𝑖푟푒푑 푆ℎ푟𝑖푛푘푎𝑔푒 = L1
Where L1 = length after drying
L2 = length after firing
W5−W6 4. 푊푒𝑖𝑔ℎ푡 푙표푠푠 = × 100 W6
Where W5 = Weight after drying
W6 = Weight after soaking
5. Water absorption = [(m2- m1)x100]/m1 where: m1 = the mass of the dry tile 99
m2 = the mass of the wet tile.
푟푒푠𝑖푑푢푒 푤푒𝑖푔ℎ푡 푚푒푎푠푢푟푒푑 ×표.623 6. 푊푒𝑖𝑔ℎ푡 푟푒푠𝑖푑푢푒 푝푒푟푐푒푛푡 = × 100% 푑푒푛푠𝑖푡푦 표푓 푠푙𝑖푝−1
relative change in length L 7. ∝= = t ish x 1/T Temperature interval L0
Where
Lo = the length of the test specimen at ambient temperature (Using Netzsch dilatometry with auto length correction. Lo is always taken to be 50.0mm in calculation.
L = the increase in length of test specimen between 50oC and 500oC (for fired test pieces, with 10oC/min heating rate.
T = the rise in temperature from 50oC to 500oC (for fired test piece with 10oC/min heating rate)
-3 o lish = correction due to the fused silica sample holder = 0.26 x 10 (from 50 C to 500oC
100