NONDESTRUCTIVE TESTING TECHNIQUES. By. Hashem Mohd Ali AI-Mattarneh. Thesis is submitted in fulfillment ofthe requirements for the degree of.
ELECTROMAGNETIC PROPERTIES OF PORTLAND CEMENT CONCRETE USING MICROWAVE NONDESTRUCTIVE TESTING TECHNIQUES
By
Hashem Mohd Ali AI-Mattarneh
Thesis is submitted in fulfillment of the requirements for the degree of Master of Science in Civil Engineering
UNIVERSITI TEKNOLOGI MARA MAY 2000
DEDICATION TO MY PARENTS MOHD, & MARIAM TO MY WIFE SITI HAFSAH
ACKNOWLEDGEMENTS .I would like to thank my supervisors Professor Dr. Ir. Wan Mahmood B. Wan A. Majid and Associated Professor Dr. Deepak Kumar Ghodgaonkar for their support and encouragement during the duration of my study. This work would not have been possible without their guidance and input. Also I would like to thank the post graduate committee in the faculty of civil engineering, Universiti Teknologi MARA, Assoc. Prof. Dr. Mohd Salleh Mohd Noh and Dr. Mohd Yusuf for their advice and assistance during the completion of this work. My sincere and special thanks to The examiners of this thesis Prof. Dr. L. F. Boswell, Director, Ocean Engineering Research Center, City University, London, UK, and Assoc. Prof. Dr. Khafilah Din, Universiti Teknologi MARA, Malaysia for their advices and comments during the completion of this work. My sincere and special thanks to all lecturers and staff of microwave lab, Faculty of Electrical Engineering, UiTM for their support and providing access to the required materials and instruments for the completion of this study. Also special thanks for staffs of the concrete lab, Faculty of Civil Engineering, UiTM for their support and help during the study. Finally I would like to express my deepest thank to my family, especially my parents (Mohd & Mariam) and my wife Siti Hafsah for their understanding, support and encouragement during the study.
111
TABLE OF CONTENT TITLE ACKNOWLEDGEMENT
iii
LIST OF TABLES
viii
LIST OF FIGURES
x
ABBREVIATIONS AND SYMBOLS
xv
ABSTRACT
xvi
CHAPTER ONE: INTRODUCTION
1
1.1 Background
1
1.2 Problem Statement
2
1.3 Objectives
3
1.4 Scope of Research
4
CHAPTER TWO: PORTLAND CEMENT CONCRETE, STRUCTURE AND PROPERTIES 2.1 Portland Cement Concrete
6 6
2.1.1 Cement
6
2.1.2 Aggregate
9
2.1.2.1 Types of Aggregate
9
2.1.2.2 Properties of Aggregate
11
2.1.2.3 Effect of Aggregate on PCC
15
2.1.3 Water
15
2.1.4 Transition Zone
16
2.2 Hydration of Portland Cement
17
2.3 Water Cement Ratio
19
2.4 Curing of Concrete
22
2.4.1 Methods of Curing
23
2.4.2 Effects of Curing on PCC
24
-2.5 Permeability of Portland Cement Concrete 2.6 Moisture Content
24
26
IV
2.7 Compressive Strength
26
2.7.1 Factors Affecting Compressive Strength
27
2.7.2 Methods of Measuring Compressive Strength
29
CHAPTER THREE: MICROWAVE NONDESTRUCTIVE TESTING, BACKGROUND, THEORY AND APPLICATIONS 3.1 Introduction
30 30
3.1.1 Advantages of Microwave NDT
30
3.1.2 Limitations of Microwave NDT
31
3.2 Electromagnetic Properties
33
3.2.1 Dielectric Theory and Polarization
33
3.2.1.1 Resistivity
34
3.2.1.2 Dielectric Constant
34
3.2.1.3 Polarization Concept
36
3.2.2 Electromagnetic Field in Media
38
3.2.2.1 Complex Permittivitty
39
3.2.2.2 Dielectric Constant and Loss Factor
40
3.2.2.3 Loss Tangent
40
3.2.2.4 Conductivity
40
3.2.3 Electromagnetic Wave Propagation
41
3.2.3.1 Reflection and Transmission of Waves at an Interface
41
3.2.3.2 Velocity of the Wave Inside Concrete
42
3.2.3.3 Wavelength Inside Concrete
43
3.2.3.4 Attenuation of the Wave Inside Concrete
43
3.2.3.5 Penetration Depth in Concrete
44
3.3 Measurement Methods and Techniques
45
3.3.1 Non-Contacting Method (Free Space)
46
3.3.2 Contacting Methods
46
3.3.2.1 Resistivity Cell
46
3.3.2.2 Parallel Plate
47
3.3.2.3 Coaxial Probe
47
3.3.2.4 Transmission Line
47
3.3.2.5 Resonant Cavity
47
3.3.2.6 Open-ended Waveguide Probe
48
v
3.4 Microwave NDT Applications
48
3.4.1 Clinkers for Portland Cement
48
3.4.2 Setting and Hydrating ofPCe
49
3.4.3 Microwave Curing ofPCC
49
3.4.4 Measuring Moisture Content ofPCe
50
3.4.5 Determination ofW/C Ratio and Compressive Strength
50
3.4.6 Deterioration ofPCC
51
3.4.7 Aggregate Size and Segregation
51
3.4.8 Detection Reinforce Bars in PCC
51
3.5 Method of Measurement Adopted
52
CHAPTER FOUR: RESEARCH PROGRAM
53
4.1 Materials
53
4.1.1 Cement
53
4.1.2 Aggregate
53
4.1.3 Water
53
4.2 Specimens Preparation
55
4.3 Specimen Conditioning
57
4.4 Measurement System and Calibration
58
4.4.1 Measurement System
58
4.4~2
61
Calibration
4.4.3 Check of Calibration and Measurement Technique
61
4.4.4 Measurement of Electromagnetic Properties
61
CHAPTER FIVE: ANALYSIS AND DISCUSSION OF RESULT
65
5.1 Effect of Frequency
65
5.2 Effect of Curing Age and Water Cement Ratio
69
5.3 Effect of Moisture Content
83
5.4 Determination ofW/C Ratio and Compressive Strength
91
5.5 Effect of Cement
99
5.5.1 Effect of Cement Type
99
5.5.2 Effect of Cement Content
101
5.6 Effect of Aggregate
103
5.6.1 Effect of Type of Aggregate
103
vi
'
5.6.2 Effect of Aggregate Ratio
104
5.6.3 Effect of Maximum Aggregate Size
107
5.7 Effect of Curing Type
109
5.8 Velocity and Wavelength of Microwave Inside Concrete
110
5.9 Depth of Penetration
116
5.10 Electromagnetic Properties of PCC Constituent
117
5.11 Summary of Findings
118
CHAPTER SIX: CONCLUSIONS, RECOMMENDATIONS AND FUTURE WORK
122
6.1 Conclusions
122
6.2 Recommendations and Future Work
124
REFERENCES
125
APPENDIX A: Fortran program for calculating dielectric constant s 130
and loss tangents
VII
LIST OF TABLES Table 2.1: Main types of Portland cement
7
Table 2.2: Usual composition limits of Portland cement and their limits
8
Table 2.3: Typical compound composition of various types of Portland cement
8
Table 2.4: Classification of natural aggregates according to rock type(BS 812:Part1: 1975).
10
Table 2.5: Typical chemical composition of limestone and granite
10
Table 2.6: British and equivalent American sieves
13
Table 2.7: BS 882:1992 grading requirements for fine aggregate.
13
Table 2.8: BS 882:1992 grading requirements for coarse aggregate.
14
Table 2.9: ASTM C33-93 grading requirements for fine aggregate.
14
Table 2.10: ASTM C33-93 grading requirements for coarse aggregate.
14
Table 3.1: Microwave frequency band.
32
Table 4.1: Physical properties of aggregates
54
Table 4.2: Properties of concrete samples
56
Table 5.1: The parameters of nonlinear regression analysis of the reflection coefficient and curing time for pee
72
Table 5.2: The parameters of nonlinear regression analysis of the dielectric constant and curing time for PCC
73
Table 5.3: The result ofNRA of loss factor with curing time for six pec mixes.
78
Table 5.4: The result ofNRA ofl08s tangent with curing time for six pee mixes.
78
-Table 5.5: The result ofNRA of conductivity with curing time for six pee mixes.
78
Table 5.6: The shifted value of the parameter a ofNRA for loss tangent, loss factor and conductivity of the sixth pec mixes.
81
Table 5.7: The parameters of nonlinear regression analysis of the reflection coefficient and moisture content of pcc.
viii
86
Table 5.8: The parameters of nonlinear regression analysis of the dielectric constant and moisture content of PCC
87
Table 5.9: The summation of parameter a and b of reflection coefficient and dielectric properties.
87
Table 5.10: Measurement of compressive of the six mixes of PCC at 28 days of curing.
91
Table 5.11: The result ofNRA of the relation ofw/c ratio and compressive strength.
92
Table 5.12: Result of regression analysis of the relation of reflection coefficient and dielectric constant versus w/c ratio 93
and compressive strength. Table 5.13: Result of regression analysis of the relation of loss factor, loss tangent and conductivity versus w/c ratio and compressive strength.
97
Table 5.14: Statistical analysis of the reflection coefficients and cement type at different time of curing.
100
Table 5.15: Statistical analysis of the reflection coefficients and cement content at different time of curing.
102
Table 5.16: Statistical analysis of the reflection coefficients and aggregate type at different time of curing.
104
Table 5.17: Statistical analysis of the reflection coefficients and aggregate ratio at different time of curing.
105
Table 5.18: Statistical analysis of the reflection coefficients and maximum aggregate size at different time of curing.
109
Table 5.19: Microwave velocity and wavelength Inside PCC (saturated and 0.45 w/c ratio) at different frequency.
111
Table 5.20: Microwave velocity and wavelength inside PCC at different w/c ratios.
112
Table 5.21: Microwave velocity and wavelength inside PCC at different moisture content and w/c ratio 0.45. Table 5.22: Electromagnetic properties ofPCC constituents.
IX
112 118
LIST OF FIGURES Figure 2.1 : Hydration of cement as a w/c ratio of 0.36
21
Figure 2.2: The relation between strength and w/c ratio ofPCC.
28
Figure 2.3: Influence of maximum size of aggregate on the 28-day compressive strength of PCC of different richness (cement content).
28
Figure 3.1 : Volume resistivity cell.
34
Figure 3.2: Parallel plate capacitor.
35
Figure 3.3: Types of dielectric polarization
37
Figure 3.4: Reflected and transmitted microwave at the boudary of two different mediums
42
Figure 4.1: Gradation of fine aggregates
54
Figure 4.2: Gradation of coarse aggregates
54
Figure 4.3: A schematic diagram of the microwave measurement system
58
Figure 4.4: Arrangement ofPCC specimen under test
60
Figure 4.5: Flowchart for finding complex permittivity , (dielectric constant and loss factor).
64
Figure 5.1: The reflection coefficient of six w/c ratios at microwave frequency range from 7.0 to 13.0 GHz after 28 days of curing
66
Figure 5.2: The dielectric constant of saturated pce of three different w/c ratios at frequency range from 8.0 to 13.0 GHz after 28 days of curing
66
Figure 5.3: The loss factor of saturated pee of three different w/c ratios at frequency range from 8.0 to 13.0 GHz after 28 days of curing
67
Figure 5.4: The loss tangent of saturated pce of three different w/c ratios at frequency range from 8.0 to 13.0 GHz after 28 days of curing
67
x
Figure 5.5: The conductivity tangent of saturated PCC of three different w/c ratios at frequency range from 8.0 to 13.0 GHz after 28 days of curing
68
Figure 5.6: The experimental results of the reflection coefficients of PCC with curing age at frequency 12.0 GHz
69
Figure 5.7: The experimental results of the dielectric constant of PCC with curing age at frequency 12.0 GHz
70
Figure 5.8: The results ofNRA of reflection coefficients of PCC with curing age at frequency 12.0 GHz
73
Figure 5.9: The results ofNRA of dielectric constant of PCC with 'curing age at frequency 12.0 GHz
74
Figure 5.10: The parameters a (reflectin coefficients after 28 days of curing) of PCC with six w/c ratios at frequency 12.0 GHz
74
Figure 5.11: The parameters a (dielectric constant after 28 days of curing) of PCC with six w/c ratios at frequency 12.0 GHz
75
Figure 5.12: The experimental results of the loss factor of PCC with curing age at frequency 12.0 GHz
76
Figure 5.13: The experimental results of the loss tangent of PCC with curing age at frequency 12.0 GHz
76
Figure 5.14: The experimental results of the conductivity of PCC with curing age at frequency 12.0 GHz
77
Figure 5.15: The results ofNLR of loss factor ofPCC with curing age at frequency 12.0 GHz
79
Figure 5.16: The results ofNLR of loss tangent ofPCC with curing age at frequency 12.0 GHz
79
Figure 5.17: The results ofNLR of conductivity of PCC with curing age at frequency 12.0 GHz
80
Figure 5.18: The parameters a (loss factor at early age of curing) of PCC with six w/c ratios at frequency 12.0 GHz
81
xi
Figure 5.19: The parameters a (loss tangent at early age of curing) of PCC with six w/c ratios at frequency 12.0 GHz
82
Figure 5.20: The parameters a (conductivity at early age of curing) ofPCC with six w/c ratios at frequency 12.0 GHz
82
Figure 5.21 : Measured values of reflection coefficient ofPCC at 85
different moisture content Figure 5.22 : Measured values of dielectric constant ofPCC at different moisture content
85
Figure 5.23 : NRA results of reflection coefficient ofPeC at 85
different moisture content Figure 5.24 : NRA results of dielectric constant of pce at
85
different moisture content Figure 5.25: Measured values of loss factor of pec at
85
different moisture content Figure 5.26: Measured values of loss tangent pce at different moisture content
85
Figure 5.27: Measured values of conductivity of pce at different moisture content
85
Figure 5.28: The 28 days compressive strength of pee mixes at different w/c ratio and the curve fit
92
Figure 5.29: The relation between the reflection coefficient and w/c ratio at frequencies 11.0 and 12.0 GHz after 28 days of curing
94
Figure 5.30: The relation between the reflection coefficient and compressive strength at frequencies 11.0 and 12.0 GHz after 28 days of curing
94
Figure 5.31: The relation between the dielectric. constant and w/c ratio at two moistures content
95
Figure 5.32: The relation between the dielectric constant and compressive strength at two moistures content
XII
95
Figure 5.33: The relation between the dielectric properties: loss tangent, loss factor, conductivity and and w/c ratio ofPCC
98
Figure 5.34: The relation between the dielectric properties: loss tangent, loss factor, conductivity and compressive strength of PCC
98
Figure 5.35: Effect of cement type on reflection coefficient of PCC at different curing time
100
Figure 5.36: Effect of cement content on reflection coefficient of PCC at different curing time
102
Figure 5.37: Effects of aggregate type on reflection coefficients of PCC at different curing time
104
Figure 5.38: Effects of aggregate ratio (coarse to fine) on reflection coefficient of PCC at different curing age
106
Figure 5.39: The standard deviation of reflection coefficient of PCC with different coarse to fine aggregate ratio at different curing age.
106
Figure 5.40: The reflection coefficient ofPCC containing different maximum aggregate size at different curing time
108
Figure 5.41: The standard deviation of the reflection coefficient of PCC containing different aggregate size
108
Figure 5.42: Effects of type of curing ofPCe on electromagnetic properties at 12 GHz.
110
Figure 5.43: Microwave velocity inside saturated PCC at different frequency and w/c ratios.
113
Figure 5.44: Microwave wavelength inside saturated PCC at different frequency and w/c ratios.
113
Figure 5.45: Microwave velocity inside air and oven dry PCC at different w/c ratios.
114
Figure 5.46: Microwave wavelength inside air and oven dry PCC at different w/c ratios.
114
Figure 5.47: Microwave velocity inside PCC at different moisture content and w/c Ratios.
115
XIII
Figure 5.48: Microwave wavelength inside pee at different moisture 115
content and w/c ratios. Figure 5.49: Penetration depth of microwave in pee after 28 days of curing and early age of curing at frequency 12.0 GHz
xiv
116
ABBREVIATIONS AND SYMBOLS PCC
: Portland Cement Concrete.
NDT
: Nondestructive Testing.
W/C
: Water Cement Ratio.
tc
: Compressiv'e Strength of PCC.
f
: Frequency in Hz. : Angular Frequency. : Wavelength.
c
: Velocity of Light.
c
: Capacitance. : Complex Permittivity. : Dielectric Constant. : Loss Factor. : Conductivity.
v
: Velocity of Microwave inside PCC.
dp
: Depth of Penetration.
MUT : Material Under Testing. 811
: Log Magnitude of reflection Coefficient in dB I
VNA : Vector Network Analyzer.
IF
: Intermediate Frequency.
M
: Moisture Content.
PVC
: Poly Vinyl Chloride.
HCP
: Hydrated Cement Paste.
r
: Reflection Coefficient.
CSH
: Calcium Silica Hydrate. : Relative Complex Permittivity. : Microwaves Attenuation. : Phase Constant. :Correlation Factor Square
xv
ABSTRACT The use of electromagnetic waves as a nondestructive evaluation technique to evaluate Portland cement concrete (PCC) structures is based on the principle that the change in structure, composition, condition, or basic properties of PCC results in a change in its electromagnetic properties. The near field open-ended rectangular waveguide is one of the few devices that can make accurate measurements of the electromagnetic properties ofPCC in the frequency range of7.0 GHz to 13.0 GHz. A microwave measurement system using open-ended rectangular waveguide developed at Universiti Teknologi MARA was used to measure the electromagnetic properties of PCC. Also, a study was conducted to investigate the effect of the basic properties and conditions of PCC, namely, curing time, water cement ratio (w/c), moisture content, curing type, compressive strength, cement type, cement content, aggregate type, aggregate ratio and maximum aggregate size on the electromagnetic properties ofPCC. Measurements were conducted in the frequency domain. The research found that, the electromagnetic properties decrease with increasing curing age. The electromagnetic properties of PCC with lower w/c ratio is lower than the PCC with higher w/c ratio at early age of curing, this is reversed after hydration (curing) is completed. The electromagnetic properties of PCC increase with increasing moisture content. There is a significant difference in the electromagnetic properties of PCC cured using different type of curing methods such as, submerged in water, cover by wet cotton and cured in air and ambient humidity. The microwave nondestructive testing using near field open-ended rectangular waveguide can be used for determination of w/c ratio, compressive strength and moisture content from the measurement of reflection coefficients, dielectric constants, loss factors and conductivity. There is no significant difference between the electromagnetic properties of PCC mixes using different type of Portland cement (Type I and Type II). Mixes containing limestone aggregate had a lower reflection coefficient than those containing granite. Also, mixes containing limestone had a greater dielectric constant and loss factor than those containing granite.
xvi
CHAPTER ONE INTRODUCTION 1.1 Background Portland Cement Concrete (PCC) is a widely used man-made building and construction material. The construction of large public works and infrastructure systems has almost been completed in many countries. Also, a large 'number of these PCC structures are currently deteriorating. Before any repairs can be undertaken on PCC structures, an evaluation to determine the existing conditions and to understand the mechanism of deterioration needs to be undertaken. This has effectively shifted the emphasis from the construction of new structures to system preservation, maintenance and rehabilitation. For maintenance and rehabilitation purposes, information should be gathered by destructive and nondestructive methods depending on the measurement requirements. Destructive methods are mostly less expensive and time consuming. On the other hand, nondestructive testing usually does not require removal of material, and allows the user to test more extensively. These considerations may increase the use of nondestructive technique. The demand for the development of reliable nondestructive testing for construction materials and constructed facilities is ever increasing. Among the nondestructive testing (NDT) methods, microwave NDT seems to be promising for the evaluation of PCC. Electromagnetic properties of materials represent the interaction of a material with the propagation of electromagnetic fields through the material. Out of many electromagnetic properties of pee, the one that are interesting to study are, the reflection and transmission coefficients, the dielectric
1
properties, conductivity, velocity and wavelength inside the concrete. Changing the properties and conditions of
pce
will result in a change of electromagnetic
properties. Magnitude and phase of reflected microwave, from a PCC target could provide information about internal flaws, material composition, water cement ratio, moisture content, curing type, curing condition, aggregate type and aggregate size. The open-ended rectangular waveguide is one of the few microwave NDT measurement methods available to measure the electromagnetic properties of PCC. This method is simple and suitable to use both in laboratory and in-situ. Recently, an open-ended waveguide has been used to measure the dielectric properties of pce in microwave frequency range. The study shows significant differences in the dielectric constant and loss factor of PCC with different water cement ratio and different sizes of aggregate[l].
1.2 Problem Statement Compared to the extensive information available for the mechanical properties of concrete, knowledge about the electromagnetic properties of concrete for nondestructive testing purposes is very limited, especially over wide range of frequency. Development of the microwave method as a tool for NDT of concrete still requires three areas to be studied. The first area is an understanding and development of electromagnetic properties of concrete as a function of frequency, moisture content, density, water cement ratio, curing type and age, and properties of concrete constituents. Second is the development of computer simulation techniques which can be used in predicting and interpreting microwave measurement results using a
2
modeling scheme; and finally development of microwave system which is suitable· for specific area of application ofNDT on PCC. Up to today, established research work directed toward the measurement of the electromagnetic properties of hardened concrete has .been in a limited range of frequency and most of the available data-is'in the range of 0.25-0.70 GHz[2-4]. In addition, some researches were conducted on Portland cement paste and mortar[5-9]. Few research studies have been undertaken to determine the electromagnetic properties ofPCC with limited aggregate size Le. less than 10mm[10] or on a special PCC condition such as wet and dry[ 11 ]. Some research studies have investigated the fresh concrete or pastes at early ages to monitor the hydration process[12]. Therefore, there is a need to study and provide values of electromagnetic properties of hardened Portland cement concrete over a wide range of frequency and concrete with different properties and conditions to be used for the nondestructive testing of existing concrete structure and construction facilities.
1.3 Objectives The main objectives of this research are to develop a measurement technique for microwave nondestructive testing of PCC, measuring and calculating the electromagnetic properties of PCC with various mixes and different conditions. Also this research will study the effects of water cement ratio, moisture content, curing age, compressive strength, curing type, cement type, cement content, aggregate type, aggregate ratio, and maximum aggregate size of PCC on its electromagnetic properties.
3
Other objectives of this research are to establish a correlation between the electromagnetic properties of PCC and the basic properties and conditions of PCC, water cement ratio, moisture content, curing age, compressive strength, maximum aggregate size and cement to aggregate ratio.
1.4 Scope of Research To achieve the objectives mentioned earlier, a Microwave Nondestructive Measurement System using open-ended rectangular waveguide probe has been developed at University Technology MARA. Portland cement concrete mixes with various parameters and PCC specimens with various conditions were cast and prepared. The parameters are the aggregate type, cement type, water cement ratio, moisture content, curing type and curing age. The system was used to measure the electromagnetic properties of PCC in microwave frequency range from 7.0 to 13.0 GHz. The effects of the basic properties and conditions of PCC on its electromagnetic properties were investigated. Finally, the relationship between the electromagnetic properties of PCC and the basic properties was established.
Chapter two describes the PCC and its constituent like cement, water, and aggregate. It discusses the hydration of cement, water cement ratio, compressive strength, moisture content, permeability, and curing of Portland cement concrete to be studied in this research. Chapter three discusses the electromagnetic and dielectric properties of materials and the different measurement techniques and methods currently used in PCC. The chapter also includes the different investigations and applications of microwave nondestructive testing, which has been conducted using Portland cement concrete and construction materials. 4
Chapter four focuses on the experimental program. It describes the materials used in this research, the methods of preparing the specimens, and the method of testing. Also, this chapter describes the measurement system developed for the purpose of this research, method of measurement, calibration of the system, check of the system measurement, and method of calculating the dielectric properties from the measured reflection coefficient. Data analysis and results together with their interpretation are presented in chapter five.
Chapter six summarizes the findings
recommendations for this study.
5
and provides conclusions and
CHAPTER TWO PORTLAND CEMENT CONCRETE, STRUCTURE AND PROPERTIES 2.1 Portland Cement Concrete Portland Cement Concrete (PCC) is a widely used man-made building and construction material. It is formulated by mixing cement, water, aggregate and admixtures in required proportions. When the ingredients are mixed and allowed to cure, it becomes hard like stone. The hardening is caused by chemical action between water and cement and it continues for a long time, and consequently the concrete attains its strength with increase in age.
pce is a widely used construction material
because of its abundance, ease of preparing and moulding, and low price of its constituents.
2.1.1 Cement The maIn constituent of PCC is cement, which is made up of calcium, silica, alumina, and iron oxide. Calcium carbonate materials like limestone provide the calcium, while clay is usually the source for silica, alumina, and iron oxide. The manufacture of cement involves crushing and grinding of the raw materials to about. 75 microns in size and then mixing them together in the kiln. This mix is then heated to about 1400°C. The reactions inside the kiln produce tricalcium silicate (3CaO.Si0 2), dicalcium silicate (2CaO.Si02), tricalcium aluminate (3CaO.AI203), and tetracalcium aluminoferrite (4CaO.AI203.Fe203). In order to simplify the usage of these terms, they have been abbreviated as C3S, C2S, C3A, and C4AF, respectively.
6
The composition of these compounds ranges from 45-60%~ 15-30%~ 6-20/0 and 6-8%, respectively[13]. These compounds do not exist in a pure form. The C3S phase is a solid solution containing magnesium and aluminum and is called alite. The phase containing C2S along with aluminum, magnesium and potassium dioxide is called belite. The C3A phase is called aluminate phase and consists of magnesium, sodium, potassium, and silica along with the C3A. The C4AF phase is called the ferrite phase.
Types of Portland Cement Several types of Portland cement are available commercially and additional special cements can be produced for specific purposes. The various types of Portland cement according to British and ASTM description are listed in Table 2.1. Ordinary Portland cement is the most common cement in use. About 90% of all cement used in USA and England is Ordinary Portland cement [14].
Table 2.1 Main types of Portland cement British Description
ASTM Description
Ordinary Portland Cement
Type I
Rapid Hardening Portland
Type III
Extra Rapid Hardening Portland Ultra Rapid Hardening Portland Low Heat Portland
Type IV
Modified Cement
Type II
Sulfate Resisting Portland
Type V
Portland Blast-furnace
Type IS
Portland-Pozzolana
TypeIP TypeP Type S
Slag Cement
7
There are different percentages of compounds used for different type of cement according to their usage. Table 2.2 and Table 2.3 show the typical values of compound composition of various types of Portland cement. Approximately the strength of all type of the cement is the same after 90 days.
Table 2.2: Usual composition of Portland cement and their limits[14] Oxide
Content (%)
CaO
60-67
Si02
17-25
Al 203
3-8
Fe203
0.5-0.6
MgO
0.5-4.0
Alkalis ( as Na20 )
0.3-1.2
S03
2.0-3.5
Table 2.3: Typical compound composition of various types of Portland cement [14]. ASTM
General
type
description
C3 S
C2S
C3 A
C4AF
I
General purpose
45-55
20-30
8-12
6-10
II
General purpose
40-50
25-35
5-7
6-10
50-65
15-25
8-14
6-10
40-50
25-35
0-4
10-20
Compound composition range (%)
with moderate sulfate resistance and moderate heat of hydration
III
High early strength
V
Sulfate resistance
8
