PRELIMINARY STUDY ON BRICKS DRYING PROCESS USING

MICROWAVE TECHNOLOGY

SALEM SALAH ABDULLAH BAGABER

UNIVERSITI TEKNOLOGI MALAYSIA

3

PRELIMINARY STUDY ON BRICKS DRYING PROCESS USING

MICROWAVE TECHNOLOGY

SALEM SALAH ABDULLAH BAGABER

A project report submitted in partial fulfilment of the

requirements for the award of the degree of

Master of Engineering (Mechanical - Advanced Manufacturing Technology)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

JUNE 2015

iii

To my beloved parents SALAH and NOUR who have supported me all the

time, to my waif Um Muaad for her unyielding support during my study period, as

well as my brothers (Abdullaziz, Khalid, Mouhammed, and Ahmed) and my sisters.

And all that help me in any way for the successful completion of this work.

ى ا لب ى ق اس ال ى واحب الن ل

ى اغ ى ل ة امى واب الي ى الغ ب وح ى ز ى. ام مغاذ , ال ى ال ى . ال

اب ن ى اب ب رة عي ى ا ق

واب خ

ى واب غا, . واخ مي ى ج

اب ى اصدق .ال

iv

ACKNOWLEDGEMENT

All praises are due to Allah the cherished, who taught man with a pen, what he

knew not. My thanks and gratitude go to Allah for bestowing me with wisdom, will, and

good health throughout the period of my master study. I asked Allah Subhanahu

wataallah to bestowed peace and blessings upon His Messenger, Muhammad S.A.W, and

all his family and companions.

I would like to express my deepest gratitude towards my supervisor Assoc. Prof.

Dr. Izman Bin Sudin for his guidance, encouragement and valuable comments during

the research and writing of this project report. His attentions and technical expertise were

key elements to my success. I am satisfied in gaining an in depth knowledge from him.

My respectful also to my co-supervisor Dr. Denni Kurniawan and Dr. Engku Nazim

for their advices, valuable comments and suggestions.

I wish also to express my sincere appreciation to my friends Mr. Yahaya Bashir

and Mr. Tijjani Abdullahi for their cooperation, time and insight on related matters

during this research.

Last but not the least, I am thankful to my friend Mr. Thamer and indebted to all

those who helped me directly or indirectly in completion of this project report.

v

ABSTRACT

Clay brick is one of the essential materials in building construction. The

demand for clay brick has been increased over the years as it goes along with the rise

of world population and industrial building constructions. The current state of brick

manufacturing process is still very traditional where drying of clay brick takes very

long time and labour intensive. Adding to this problem, uneven heating during drying

and firing affect a lot to bricks quality which often cause cracks. This research aims to

evaluate the effectiveness of microwave energy source against the conventional

methods for drying four different types of clay bricks. Green clay samples were

pressed into a slab specimen at different compositions (%clay, %water, %lime, %fly

ash). Later, the green samples were dried under four different mediums (natural, hot

air, electric oven and microwave). The quality of dried bricks was compared in terms

of water absorption, density, and porosity. It is found that microwave heating

outperforms the three conventional heating methods by drying all types of brick

samples without crack. Design of experiment (DOE) was utilized to evaluate

significant factors (temperature (60-70-80oC), time (6-8-10 min) and percentage of

charcoal (0-3-6%)) to dry red brick samples. Responses were crack density, brick

density, water absorption and moisture contents. Analysis of variance indicates that

all three factors are significant. Temperature is the most influential factors among the

three affecting all responses. It is found that drying bricks at 70oC succeeding without

any crack generation on the samples. It is also noted that a significant faster drying

rate is seen when adding various percentages of charcoal contents in brick samples.

From the results obtained, it is concluded that microwave technology has a great

potential to be applied as a heating source in the production of bricks. The usage of

this technology is foreseen able reduce the intensive labour dependent in brick

manufacturing industry and this method is able to manufacture brick in a more

sustainable environment.

vi

ABSTRAK

Bata tanah liat bahan penting dalam industri dan ia telah digunakan untuk

pelbagai jenis tujuan membina. Kaedah tradisional bata tanah liat pengeringan

mengambil masa yang lama untuk kering. Dalam tempoh itu, banyak masalah berlaku

disebabkan pemanasan tidak sekata ia akan menjejaskan kualiti batu bata itu. Tesis ini

bertujuan untuk memberikan kaedah alternatif pengeringan dan mengesan

kemungkinan menggunakan gelombang mikro sebagai teknologi baru untuk proses

pengeringan yang berkesan. Microwave disebabkan cepat kering adalah dicadangkan

untuk produk baru bata tanah liat atau bahan buangan kitar semula seperti abu terbang

dengan menukar kepada produk bata. Satu sampel basah tanah liat ditekan ke dalam

papak yang telah tertakluk dalam penyinaran gelombang mikro daripada 2.45 GHz.

Kelakuan pengeringan telah dibandingkan antara empat mod: ketuhar gelombang

mikro, ketuhar elektrik, udara panas, dan pangkalan udara semula jadi pada masa

pengeringan, retak, penyerapan air, ketumpatan dan keliangan. Data dan keputusan

yang diperolehi daripada ujian yang telah dianalisis dan dipersembahkan dalam format

yang lebih sesuai, seperti graf, jadual, dan kenyataan. Pemanasan gelombang mikro

dengan kuasa yang tinggi menyebabkan pecah spesimen apabila persediaan suhu yang

dicapai pada 100oC. Walau bagaimanapun, jika kuasa yang dikawal untuk

mengekalkan suhu yang kurang daripada titik wap air pada 70oC atau kurang,

pengeringan berjaya tanpa generasi retak sehingga selesai dengan berbanding dengan

sumber-sumber pemanasan konvensional. Ia juga menyatakan menambah peratusan

variasi arang (3-6%) Kadar pengeringan secara signifikan lebih cepat. Kesan tiga

parameter input, yang suhu (60-70-80oC), masa pengeringan (6-8-10 min), dan

peratusan arang pada generasi retak, dan masa pengeringan telah dianalisis dengan

menggunakan reka bentuk eksperimen (DOE) kaedah. Melalui analisis ANOVA, ia

telah mendapati bahawa suhu adalah parameter yang paling penting yang memberi

kesan untuk semua tindak balas. Penambahan adalah arang yang besar ke atas kadar

pengeringan dan kepadatan. Daripada keputusan dari ujian yang diperolehi

menunjukkan bahawa teknologi gelombang mikro boleh diperkenalkan kepada

pengeluaran bata talian sebagai sumber pemanas. Ia akan menyumbang untuk

membuat proses automatik industri bata, mengurangkan masa pengeluaran dan

mengurangkan potensi kerosakan ke atas manusia dan alam sekitar.

vii

TABLE OF CONTENTS

CHAPTER TITLE PAGE

DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENT iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF ABBREVIATIONS xvi

LIST OF APPENDICES xvii

1 INTRODUCTION 1

1.1 Introduction 1

1.2 Background of Problem 1

1.3 Problem Statement 3

1.4 Objectives of Study 3

1.5 Scope of the Study 3

1.6 Signification of Study 4

2 LITERATURE REVIEW 5

2.1 Introduction 5

2.2 Type of bricks 6

2.2.1 Common Burnt Clay Bricks 6

2.2.2 Sand lime bricks 6

viii

2.2.3 Engineering Bricks 6

2.2.4 Concrete Bricks 7

2.2.5 Fly Ash Clay Bricks 7

2.2.6 Specials Bricks 7

2.3 Clay Brick 8

2.3.1 Properties of Clay Brick 9

2.3.1.1 Water Absorption rate 9

2.3.1.2 Density 10

2.3.1.3 Brick Strength 10

2.3.1.4 Durability 11

2.3.1.5 Texture 11

2.3.1.6 Color of brick 12

2.3.1.7 Efflorescence 12

2.3.2 Sizes of Brick 13

2.3.3 Clay Brick Production 13

2.4 Drying Process 14

2.4.1 Mechanism of drying process 14

2.4.2 Drying Process Phases 16

2.8 Drying Methods of Clay Bricks 17

2.8.1 Natural Drying 17

2.8.2 Artificial Drying 18

2.8.2.1 Chamber Dryers 19

2.8.2.2 Tunnel Dryers 19

2.8.2.3 Advantage of artificial Drying 19

2.8.2.4 Disadvantages of Artificial

Drying 20

2.9 Microwave Technology 20

2.9.1 Properties of Microwave 21

2.9.2 Microwave Heating Mechanism 22

2.9.3 Application of Microwaves Heating 24

2.9.4 Microwave Processing of Materials 25

2.9.5 Industrial Application of Microwave

Heating 26

ix

2.9.6 Advantage of microwave heating 26

2.9.7 Benefits of Microwave Hybrid Drying

in Manufacturing 27

2.9.8 Disadvantages of Microwave Heating 28

2.9.9 Previous Studies on Microwave

Technology 28

3

RESEARCH METHODOLOGY

30

3.1 Introduction 30

3.2 Research Flowchart 30

3.3 Preparation of Samples 32

3.4 Experiment Details 34

3.5 Analysis of A moisture content, Water

Absorption, Porosity and Density 37

3.6 Experimental And Analytical Equipment 38

3.6.1 Drying Process Equipment 38

3.6.2 Compaction And Weighting Machine 38

3.7 Characterization of Micro Cracks 39

4 RESULTS AND DISCUSSION 41

4.1 Introduction 41

4.2 4.2. Analysis of Dried Bricks 41

4.2.1 Analysis of Water Absorption 41

4.2.2 Analysis of Moisture Content 43

4.2.3 Analysis Density of Bricks 45

4.2.4 Crack Analysis of Dried Bricks 46

4.2.5 Analysis Porosity of Bricks 48

4.2.6 Overall Results Discussion 49

4.3 Design of experiment (DOE) analysis 50

4.3.1 Collection of Experimenter Data 50

4.3.2 ANOVA Results 53

4.3.3 Main And Interaction Effects 57

4.3.4 Contour And Surface Plots 60

x

5 CONCLUSION AND RECOMMENDATIONS 64

5.1 Introduction 64

5.2 Conclusions 64

5.3 Recommendations for Future Work 65

REFERENCES 67

Appendices A 71

Appendices B 72

Appendices C 73

xi

LIST OF TABLES

TABLE NO TITLE PAGE

2.1 Classification of brick by compressive strength

and water absorption 10

2.2 Various combinations of dimensions of bricks 13

3.1 Composition of clay samples 32

3.2 Preparation size of brick sample 32

3.3 Parameters setting of for drying bricks without

charcoal 35

3.4 The process setting for microwave drying of red

clay 36

3.5 Experimental planning 36

3.6 The process setting using in this experiment 65

4.1 Comparison difference types of drying heating 49

4.2 The process setting using in this experiment 50

4.3 The recorded of factors and responses 51

4.4 Complete matrix for all effects 51

4.5 Analysis of variance (ANOVA) for factorial model

(a) water absorption (b) moisture content (c)

density (d) crack 52

4.6 Mean and R-squared value (a) water absorption (b)

moisture content (c) density (d) crack 54

4.7 Summary for Appropriate Drying Setting by

Microwave 62

xii

LIST OF FIGURES

FIGURE NO TITLE PAGE

2.1 Diagram of clay brick making 14

2.2 Schematic drawing of drying in three phases 28

2.3 Microwave frequency band in the electromagnetic

spectrum 21

2.4 Microwaves interactions with different materials 24

3.1 Simplified of flow chart methodology 31

3.2 General Flowchart of the Research Methodology 31

3.3 Flow chart of green brick sample preparation 33

3.4 Schematic brick sample size 33

3.5 Sequence of brick sample preparation 34

3.6 Compression machine 38

3.7 Digital scale for weight brick 39

4.1 Percentage of water absorption against (a) time (b)

temperature 42

4.2 Percentage of moisture content against (a) time (b)

temperature 43

4.3 Percentage of density against (a) time (b)

temperature 45

4.4 Percentage of cracks against (a) time (b)

temperature 46

4.5 Percentage of porosity against (a) time (b)

temperature 48

4.6 Half-Normal probability plot for the effects 55

4.7 Pareto chart for effects 56

xiii

4.8 One factor plot for water absorption versus

temperature 57

4.9 One factor plot for water absorption versus rate of

charcoal 58

4.10 Interaction factor plot between temperature and

rate of charcoal 58

4.11 Contour plot for water absorption 59

4.12 3D surface response plot 60

4.13 Moisture content response plot 61

4.14 Density response plots 61

4.15 Crack response plot 62

xiv

LIST OF ABBREVIATIONS

ANOVA- Analysis of Variance

DF - Degree of Freedom

BS - British Standard

CMC - Critical Moisture Content

DOE - Design of Experiment

MMC - Minimum Moisture Content

MS - Mean Square

MW - Microwave

RSM - Response Surface Methodology

SABS - South African Bureau of Standards

SBF - Simulated Body Fluid

SS - Sum of Square

xv

LIST OF APPENDICES

APPENDIX TITLE PAGE

A f TABLE WITH 95%CONFIDENCE LEVEL 71

B DLH1000 V1.2 SOFTWARE 72

C DESIGN OF EXPERIMENT TABLES 73

1

CHAPTER 1

INTRODUCTION

1.1 Introduction

This chapter provides an insight the research conducted on bricks drying

process using various methods including microwave technology. A brief overview on

microwave technology and related issues are also discussed. It is followed by the

problem statement, objectives, scopes and significance of the research work.

1.1 Background of Problem

Microwaves were fundamentally used for communication. In the middle of

the last century 1950, it was discovered that microwave energy can heat materials.

Now microwave ovens have become more common for cooking and heating food

products. Researchers have been looking for ways to utilize the advantages of

microwave for industrial applications. Microwave is primarily used for heating, but

non-thermal applications have also been studied. The most striking feature of

microwave heating is volumetric heating, which is rather different from conventional

heating where the heat must diffuse in from the surface of the fabric. Volumetric

heating means that materials can absorb microwave energy internally and convert it

2

to heat. It is this characteristic that leads to advantages using microwaves to process

materials (Wu, 2002).

In the past, microwave heating had been successfully applied in the next

fields: tempering meat, preheating rubber slugs, vulcanizing rubber, precooking

bacon, drying pasta, drying crushed oranges, and so on (Kamble and Patil, 2015).

Clay brick is an important materials used in the building industries. Its

applications range from building houses, factories, waterways, tunnels, bridges, etc.

Its properties vary according to the purpose for which they are intended, but it have

provided the basic material of construction for centuries. Clay brick have been used

for construction for thousands of years, and some advances have been achieved to

make the process easier and faster. The essential technique for making bricks from

clay has remained unchanged. Green clay products can be dried "naturally" or

artificially" (Gillott, 2012).

Common Issues in conventional drying of clay brick; drying process consists

of many stages. Therefore that take a lot of time from 2-5 days. For natural drying

which are using natural sources such as Sun, wind, and open-air drying, the complete

drying need a long time (3days-week) depend weather condition. And required to use

a large of space (220 x 106 m2) for 1000 pieces. Cracking is one of the major issues

in brick manufacturers and the losses can be up to 20% because these conventional

heating often creates uneven heating in the clay brick which cause cracking.

Artificial drying process using chamber dryers, tunnel dryers, and kiln that need

equipments such as fans, channels, valves, controlling systems, heating source, and

power. Additionally, the energy and labour intensive, long time production, large

area, and high fuel consumption (5MJ kg-1) that will be make production process

costly. Other more important problem the conventional heating using fuel is

extremely harmful to the environment (Dlamini, 2014).

3

1.2 Problem Statement

Clay bricks are usually fired using fuel, gas or even natural wood. These

conventional heating often creates uneven heating in the clay brick which cause

cracking. Cracking is one of the major issues facing by brick manufacturers and the

losses can be up to 20% of monthly production (Musielak and Śliwa, 2015). Brick

production can be categorised as energy and labour intensive industry (Pirasteh et al.,

2014). Since a lot of energy used for drying process as well as involving many

manual operations. Microwave technology has been seen a more sustainable method

to the current heating techniques for brick industry. Despite many studies using

microwave technology in drying processes, however, there is not much research

reported that applies this technology for brick drying and firing process.

1.3 Objectives of Study

The objectives of this project were as follows:

1. To determine the feasible range of microwave parameters for effective

drying different clay bricks

2. To evaluate the properties of clay bricks after dried using microwave

energy source with and without adding charcoal contents

3. To determine significant microwave parameters that affect dried brick

properties.

1.4 Scopes of Study

1. Modified domestic microwave oven (Elba Operating at 2.45GHz and

output power of 700W) was used to dry brick specimens. Operating

4

temperature and time were varied: 60-70-80oC and 6-8-10 minutes

respectively.

2. Charcoal was varied from 3 – 6% in the clay and served as a microwave

susceptor during heating.

3. Three types of bricks were prepared, namely; Kaolin, Red and Fly ash

4. Properties of dried bricks were compared in terms of moisture contents,

water absorption, density, porosity and cracking nature.

1.5 Significance of Study

It is well known that microwave technology has a great potential for reducing

energy consumption as compared to high power furnace and kiln that powered by

fuel/gas for drying process of brick. The successful application of microwave energy

in brick drying would also potential in reducing processing time from days to hours

and able to reduce percentage of cracks due to uniform heating. This process is

simple and possible to be automated for mass production. It uses very low current,

clean production and utilize non-toxic raw material which makes the whole process a

more environmental friendly.

66

REFERENCES

Appleton, T., Colder, R., Kingman, S., Lowndes, I. and Read, A. (2005). Microwave

technology for energy-efficient processing of waste. Applied energy. 81(1), 85-113.

Bell, F. G. (2013). Engineering properties of soils and rocks. Elsevier.

Breccia, A., Esposito, B., Fratadocchi, G. B. and Fini, A. (1999). Reaction between methanol

and commercial seed oils under microwave irradiation. Journal of microwave power

and electromagnetic energy. 34(1), 2-7.

Cha-um, W., Rattanadecho, P. and Pakdee, W. (2009). Experimental analysis of microwave

heating of dielectric materials using a rectangular wave guide (MODE: TE 10)(case

study: water layer and saturated porous medium). Experimental Thermal and Fluid

Science. 33(3), 472-481.

Chiu, K., Cheng, F. and Man, H. (2005). A preliminary study of cladding steel with NiTi by

microwave-assisted brazing. Materials Science and Engineering: A. 407(1), 273-

281.

Davis, C. T. (1895). A Practical Treatise on the Manufacture of Brick, Tiles and Terra-cotta.

HC Baird & Company.

Deboucha, S. and Hashim, R. (2011). A review on bricks and stabilized compressed earth

blocks. Scientific Research and Essays. 6(3), 499-506.

Demir, I. (2008). Effect of organic residues addition on the technological properties of clay

bricks. Waste management. 28(3), 622-627.

Dlamini, M. (2014). Clay and concrete brick.

Domínguez, A., Menéndez, J., Inguanzo, M. and Pis, J. (2005). Investigations into the

characteristics of oils produced from microwave pyrolysis of sewage sludge. Fuel

Processing Technology. 86(9), 1007-1020.

Fernández, Y., Arenillas, A. and Menéndez, J. Á. (2011). Microwave Heating Applied to

Pyrolysis, Advances in Induction and Microwave Heating of Mineral and Organic

Materials, Stanisław Grundas (Ed.), ISBN: 978-953-307-522-8, InTech. InTech.

Gillott, J. E. (2012). Clay in engineering geology. Elsevier.

67

Hammouda, I. and Mihoubi, D. (2014). Comparative numerical study of kaolin clay with

three drying methods: Convective, convective–microwave and convective infrared

modes. Energy Conversion and Management. 87, 832-839.

Hayes, B. L. (2004). Recent advances in microwave-assisted synthesis. Aldrichimica Acta.

37(2), 66-77.

Itaya, Y., Uchiyama, S., Hatano, S. and Mori, S. (2005). Drying enhancement of clay slab by

microwave heating. Drying technology. 23(6), 1243-1255.

K.Sabid (2014). Experimental Study on Interface Behavior of Masonry Structures. IJSRD -

International Journal for Scientific Research & Development. 2, Issue 09,

2014(2321-0613).

Kamble, Y. and Patil, S. (2015). An Overview of Study of Microwave Heating Technique

and Its Applications. IJSRD - International Journal for Scientific Research &

Development. Vol. 3, Issue 02, 2015( 2321-0613), 3.

Kekkonen, P. i. M., Ylisassi, A. and Telkki, V.-V. (2014). Absorption of Water in Thermally

Modified Pine Wood As Studied by Nuclear Magnetic Resonance. The Journal of

Physical Chemistry C. 118(4), 2146-2153.

KHOSO, S., WAGAN, F. H., KHAN, J. S., BHATTI, N.-u.-K. and ANSARI, A. A. (2014).

Qualitative analysis of baked clay bricks available in Larkana Region, Pakistan.

Architecture–Civil Engineering–Environment. 7(2), 41-50.

Koroneos, C. and Dompros, A. (2007). Environmental assessment of brick production in

Greece. Building and Environment. 42(5), 2114-2123.

Lam, S. S., Russell, A. D. and Chase, H. A. (2010). Pyrolysis using microwave heating: a

sustainable process for recycling used car engine oil. Industrial & Engineering

Chemistry Research. 49(21), 10845-10851.

Lidström, P., Tierney, J., Wathey, B. and Westman, J. (2001). Microwave assisted organic

synthesis—a review. Tetrahedron. 57(45), 9225-9283.

Liu, Z., Guo, B., Hong, L. and Lim, T. H. (2006). Microwave heated polyol synthesis of

carbon-supported PtSn nanoparticles for methanol electrooxidation.

Electrochemistry Communications. 8(1), 83-90.

Ludlow-Palafox, C. and Chase, H. A. (2001). Microwave-induced pyrolysis of plastic

wastes. Industrial & engineering chemistry research. 40(22), 4749-4756.

Luque, R., Menéndez, J. A., Arenillas, A. and Cot, J. (2012). Microwave-assisted pyrolysis

of biomass feedstocks: the way forward? Energy & Environmental Science. 5(2),

5481-5488.

Lynch, G. (1994). Bricks: properties and classifications. Structural Survey. 12(4), 15-20.

68

Makul, N., Rattanadecho, P. and Agrawal, D. K. (2014). Applications of microwave energy

in cement and concrete–A review. Renewable and Sustainable Energy Reviews. 37,

715-733.

Malafronte, L., Lamberti, G., Barba, A. A., Raaholt, B., Holtz, E. and Ahrné, L. (2012).

Combined convective and microwave assisted drying: Experiments and modeling.

Journal of Food Engineering. 112(4), 304-312.

Metaxas, A. (1991). Microwave heating. Power Engineering Journal. 5(5), 237-247.

Metaxas, A. (1996). Foundations of electroheat: a unified approach. John Wiley & Sons Inc.

Molnar, K. (2014). 2 Experimental Techniques in Drying. Handbook of Industrial drying.

31.

Mujumdar, A. S. (2014). 1 Principles, Classification. Handbook of Industrial Drying. 1.

Musielak, G. and Śliwa, T. (2015). Modelling and Numerical Simulation of Clays Cracking

During Drying. Drying Technology. (just-accepted).

Okunade, E. A. (2008). The effect of wood ash and sawdust admixtures on the engineering

properties of a burnt laterite-clay brick. Journal of Applied Sciences. 8(6), 1042-

1048.

Ottosen, L. M. and Christensen, I. V. (2012). Electrokinetic desalination of sandstones for

NaCl removal—test of different clay poultices at the electrodes. Electrochimica

Acta. 86, 192-202.

Parnell, J., Watt, G., Chen, H., Wycherley, H., Boyce, A., Elmore, D., Blumstein, R., Engel,

M. and Green, P. (2004). Kaolin polytype evidence for a hot-fluid pulse along

Caledonian thrusts during rifting of the European Margin. Mineralogical Magazine.

68(3), 419-432.

Pirasteh, G., Saidur, R., Rahman, S. and Rahim, N. (2014). A review on development of

solar drying applications. Renewable and Sustainable Energy Reviews. 31, 133-148.

Rao, K., Vaidhyanathan, B., Ganguli, M. and Ramakrishnan, P. (1999). Synthesis of

inorganic solids using microwaves. Chemistry of Materials. 11(4), 882-895.

Salema, A. A. and Ani, F. N. (2012). Pyrolysis of oil palm empty fruit bunch biomass pellets

using multimode microwave irradiation. Bioresource technology. 125, 102-107.

Shang, X.-Y., Zhou, G.-Q., Kuang, L.-F. and Cai, W. (2014). Compressibility of deep clay in

East China subjected to a wide range of consolidation stresses. Canadian

Geotechnical Journal. 52(2), 244-250.

Sharma, A., Aravindhan, S. and Krishnamurthy, R. (2001). Microwave glazing of alumina–

titania ceramic composite coatings. Materials Letters. 50(5), 295-301.

Stuerga, D. (2006). Microwave-material interactions and dielectric properties, key

ingredients for mastery of chemical microwave processes. Microwaves in Organic

69

Synthesis (Loupy A, ed). 2nd ed. Weinheim, Germany: Wiley-VCH Verlag Gmbh &

Co. KgaA. 1-61.

Sulaiman, S., Baharudin, B., Arifin, M. and Hambali, A. A. (2011). Design and Simulation

on Investment Casting Mold for Metal Matrix Composite Material. Proceedings of

the 2011 Applied Mechanics and Materials: Trans Tech Publ, 1676-1681.

Thomas, K. (1996). Masonry walls: specification and design. Butterworth Architecture.

Thostenson, E. and Chou, T.-W. (1999). Microwave processing: fundamentals and

applications. Composites Part A: Applied Science and Manufacturing. 30(9), 1055-

1071.

Todaro, L., Dichicco, P., Moretti, N. and D’Auria, M. (2013). Effect of combined steam and

heat treatments on extractives and lignin in sapwood and heartwood of Turkey oak

(Quercus cerris L.) wood. BioResources. 8(2), 1718-1730.

Tontand, S. and Therdthai, N. (2009). Preliminary study of chili drying using microwave

assisted vacuum drying technology. Asian Journal of Food and Agro-Industry. 2(2),

80-86.

Wang, Z. H. and Shi, M. H. (1999). Microwave freeze drying characteristics of beef. Drying

technology. 17(3), 434-447.

Wilson, M., Carter, M. and Hoff, W. (1999). British standard and RILEM water absorption

tests: a critical evaluation. Materials and Structures. 32(8), 571-578.

Wu, X. (2002). Experimental and theoretical study of microwave heating of thermal runaway

materials.

Yu, F., Deng, S., Chen, P., Liu, Y., Wan, Y., Olson, A., Kittelson, D. and Ruan, R. (2007).

Physical and chemical properties of bio-oils from microwave pyrolysis of corn

stover. Applied Biochemistry and Biotechnology. 137(1-12), 957-970.