lee_jin_an
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COMPRESSiVE 91RENCTffI OF HIGH SIRENGIH CONCREIF USING BRuSH STANDARD, EURO CODE AND NON- DESWUCHVE ThSI' APPROACHES
LFEJINAN
A thesis submitted in partial fulfillment of the requirements for the award of degree of Bachelor of Civil Engineering.
Faculty of Civil Engineering and Earth Resources
Universiti Malaysia Pahang
NOVEMBER 2010
ABSTRACT
High strength concrete has been widely used in civil engineering in recent
years. High strength concrete provides high compressive strength but lower the
ductility than normal strength concrete. In this study, the compressive strength of cube
and cylinder specimens was compared. Cube test is the common measurement of
concrete compressive strength. According to British Standard 8110, the design of
concrete structures is depend on the cube strength. In industries, the cube strength
test is conducted to obtain the grade of concrete before it is applied to the work. In
future, Eurocode 2 (EC2) will replace the existing British code 13S8 110 for the design of
concrete structure. EC2 have some benefits compared to British Standard. Concrete
strengths are referred to by cylinder strength, which are typically 10-20% less than the
corresponding cube strengths. In this investigation, the concrete cube and cylinder
were tested on 7 and 28 days of water curing. The result show that the value of
cylinder strength is about 18-21% less than the cube strength. Nondestructive test
which are Rebound Hammer test and Ultrasonic Pulse Velocity test was also used to test the concrete strength.
V
ABSTRAK
Konkrit kekuatan tinggi digunakan secara meluas dalam bidang kejuruteraan
awam pada kebelakangan mi. Konkrit kekuatan tinggi mernpunyai daya mampatan
yang tinggi tetapi kerapuhan yang rendah berbanding konkrit biasa. Dalam kajian mi,
daya mampatan antara konkrit kiub dan konkrit sunder dibandingkan. Ujian kiub
adalah ujian biasa digunakan untuk mengukur daya manpatan konkrit. Berdasarkan
kepada British Standard BS8 110 (BS8I 10), reka bentuk struktur bergantung kepada
kekuatan kiub. Dalam industri, ujian kekuatan kiub dijalankan untuk mendapatkan gred
konkrit sebelum diaplikasikan dalam keija pembinaan. Walaubagaimanapun Eurocode
(EC2) akan menggantikan Bs81 10 dalam merekabentuk struktur pada masa yang akan
datang. Eurocode rnempunyai kelebihan berbanding dengan British Standard.
Knkuatan konkrit silinder adalah antara 10 - 20 1/o kurang daripada kekuatan kiub.
Dalam kajian ml, kekuatan konkiit kiub dan silkier diukur pada hari ke 7 dan hari ke 28
selepas rendaman air dijalankan. Hasil ujikaji menunjukkan kekuatan sunder adalah
18-21% kurang daripada kekuatan Idub. Ujian nondestructive iaitu ujian Rebound
Hammer dan ujian Ultrasonic Pulse Velocity juga digunakan untuk mengiiji kekuatan
konkrit ]dub.
vi
TABLE OF CONTENT
CHAPTER
TITLE PAGE
TITLE i DECLARATION DEDICATION iii ACKNOWLEDGEMENT iv ABSTRACT v AI3STRAK vi TABLE OF CONTENTS vii LIST OF TABLES xi LIST OF FIGURES xiii LIST OF SYMBOLS xv
1 INTRODUCTION 1
1.1 Background of Study 1
1.2 Problem Statements 3 1.3 Objectives of Study 4
1.4 Scopes of Study 4
LIM
Mm
2 LITERATURE RIVIEW 5
2.1 Introduction 5
2.2 History of Concrete 6 2.2.1 Background of High-Strength Concrete 7 2.2.2 Advantages and Disadvantages of High- 8
Strength Concrete
2.3 Material 8 2.3.1 Fine Aggregate 8 2.3.2 Water 9 2.3.3 Portland Cement 9 2.3.4 Coarse Aggregate 10
2.4 European Standard 10 2.4.1 History of European Standards 11 2.4.2 Eurocode 2 11 2.4.3 Comparison between EC2 and BS8I 10 12
2.5 Strength of concrete 13 2.5.1 Compressive Strength of Concrete 13
2.6 Characteristic of Concrete i 2.6.1 Workability 15 2.6.2 Strength 16 2.6.3 Elasticity 17 2.6.5 Slenderness Ratio 17 2.6.6 Buckling 18
2.7 Mechanical Properties of Concrete 18 2.8 Factor Affecting Properties of Concrete 19
2.8.1 Water to Cement Ratio (W/C) 19 2.8.2 Concrete Material Factor 19 2.8.3 Temperature and Relative Humidity 20 2.8.4 Aggregate Properties 21
2 LITERATURE RIVIEW 5
2.1 Introduction 5
2.2 History of Concrete 6 2.2.1 Background of High-Strength Concrete 7 2.2.2 Advantages and Disadvantages of High- 8
Strength Concrete
2.3 Material 8 2.3.1 Fine Aggregate 8 2.3.2 Water 9 2.3.3 Portland Cement 9 2.3.4 Coarse Aggregate 10
2.4 European Standard 10 2.4.1 History of European Standards 11 2.4.2 Eurocode 2 11 2.4.3 Comparison between EC2 and BS81 10 12
2.5 Strength of concrete 13 2.5.1 Compressive Strength of Concrete 13
2.6 Characteristic of Concrete 15 2.6.1 Workability 15 2.6.2 Strength 16 2.6.3 Elasticity 17
2.6.5 Slenderness Ratio 17 2.6.6 Buckling 18
2.7 Mechanical Properties of Concrete 18
2.8 Factor Affecting Properties of Concrete 19 2.8.1 Water to Cement Ratio (W/C) 19
2.8.2 Concrete Material Factor 19
2.8.3 Temperature and Relative Humidity 20
2.8.4 Aggregate Properties 21
vJ-u
ix
2.9 Compressive strength test 21 2.9.1 Non Destructive Test (ND!) 23
2.9.1.1 Purpose ofNDF 24 2.9.1.2 Types ofNDF 25
3
METHODOLOGY 26
3.1 Introduction 26 3.2 Material 28
3.2.1 Fine Aggregate 28 3.2.2 Coarse Aggregate 29 3.2.3 Water 30 3.2.4 Ordinary Portland Cement 30
3.3 Preparation of Materials 31 3.4 Sieve Analysis 31 3.5 Mould of Specimen 33
3.5.2 Number of Specimens 34 3.6 Concrete Mix 35 3.7 Curing 35 3.8 Compressive Strength Test 36
3.8.1 Cylinder Test 37 3.8.2 Cube Test 38 3.8.3 Rebound Hammer Test 39 3.8.4 Ultrasonic Pulse Velocity Test 40
Iz-
x
4 RESULT AND DISCUSSION 42
4.1 Introduction 42 4.2 Comparison of concrete cube compression test 43
with concrete cylinder Compression test,
4.3 Comparison of concrete cube test 46 4.4 Result of Concrete Compression Test 49
4.4.1 Compressive Strength Test 49 4.4.1.1 Cube Test 49:. 4.4,1.2 Cylinder Test 51
4.4.2 Nondestructive Test 53
4.4.2.1 Rebound hammer Test 53
4.4.2.2 Ultrasonic Pulse Velocity Test 55
5 CONCLUSIONS AND RECOMMENDATIONS 58
5.1 Conclusion 58 5.2 Recommendation 59
REFERENCES 60
APPENDIX A 65 APPENDIX B 72
LIST OF TABLES
TABLE NO. TITLE PAGE
3.1 Volume of Sample 31 3.2 Quantity of Material for Concrete Grade 40 31 3.3 Quantity of Material for Concrete Grade 50 31 3.4 Quantity of Mould Used In Testing 34 4.1 Result of Concrete Cube Test and Concrete Cylinder 43
Test of Concrete Grade 40
4.2 Result of Concrete Cube Test and Concrete Cylinder 44 Test of Concrete Grade 50
4.3 Result of Concrete Cube Compression Test and 46 Nondestructive Test for Concrete Grade 40
4.4 Comparison between Concrete Cube Compression Test 47 and Nondestructive Test for Concrete Grade 50
4.5 Result of Cube Test for Concrete Cube Grade 40 49 4.6 Result of Cube Test for Concrete Cube Grade 50 50 4.7 The Result of Compressive Strength of Concrete 51
Cylinder Grade 40
4.8 The Result of Compressive Strength of Concrete 52 Cylinder Grade 50
4.9 Result of Rebound Hammer Test ofConcrete Grade 40 54 4.10 Result of Rebound Hammer Test of Concrete Grade 50 54 4.11 Result of Ultrasonic Pulse Velocity Test of Concrete 56
Grade 40
4.12 Result of Ultrasonic Pulse Velocity Test of Concrete 56
Grade 50
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Ratio of Compressive Strength to 28-Day 14 Cylinder Strength versus Time
2.2 Summary of Compressive Strength-Temperature By 20 Relationships for Normal Weight Concrete Obtained
Unstressed Test
2.3 The Effect of the Aggregate Type on Compressive
Strength 21 2.4 Compression Testing on Cube and Its Various Failure 22
Modes
2.5 Failure Mode of Cylindrical Specimen 23 3.1 Flowchart ofLaboratory Work 27 3.2 Fine Aggregate 28 3.3 Coarse Aggregate
3.4 Ordinary Portland Cement. 30 3.5 Sieve 32 3.6 Mechanical Sieve Shaker 33 3.7 Cube Mould of15Ommx15Omnxi5nn 33 3.8 Cylinder Mould of 150mm in Diameter and 300mm 34
Height.
3.9 Drum Mixer 35 3.10 Curing Tank 36
3.11 Compressive Test Machine 37 3.12 Cylinder Test 38 3.13 Rebound Hammer 40 3.14 Ultrasonic Pulse Velocity Test Equipment 41 4.1 Comparison of Concrete Cube Test with Concrete 43
Cylinder Test of Concrete Grade 40
4.2 Comparison of Concrete Compression Test with 45
Concrete Cylinder Compression Test of Concrete Grade
50
4.3 Comparison between Concrete Compression Test with 46
Nondestructive Test of Concrete Grade 40
4.4 Comparison of Concrete Compression Test with 48
Nondestructive Test of Concrete Grade 50
4.5 Comparison of Concrete Cube Compression Test 50
- between 7 and 28 Days Ages of Concrete
4.6 The Comparison of Concrete Cylinder Compression. 52
Test between 7 and 28 Days Ages of Concrete
4.7 Comparison of Rebound Hammer Test between 7 and 54
28 Days Ages of Concrete Grade 40 and 50
4.8 Comparison of Ultrasonic Pulse Velocity Test between 57
7 and 28 Days Ages of Concrete
MV
LIST OF SYMBOLS
fck - Characteristic cylinder strength
fYd - Design yield strength fc - Concrete strength
TM - Partial safety factor T - Time in second V - Velocity
cm - Centimeter mm - Millimeter km - Kilometer
UPV - Ultrasonic Pulse Velocity NSC - Normal Strength Concrete NDT - Non Destructive Test
ASTM - American Society of Testing Material
CHAPTER 1
INTRODUCTION
1.1 Background of Study
High strength concrete has been widely used in civil engineering in recent
years.This is because most of the rheological, mechanical and durability properties
of these materials are better than those of conventional concretes.
High strength is made possible by reducing porosity, inhornogeneity and
microcracks in concrete and the transition zone (Nawy, 1996). A definition of high
strength concrete in quantitative term which is acceptable to everyone is not
possible. In North American practice, high strength concrete is usually considered
to be a concrete with a 28-day compressive strength of at least 42 MPa. In a
recent CEB-FIP state-of-the-art report on high strength concrete, it is defined as
concrete having a minimum 28-day compressive strength of 60 MPa. In many
developed countries, the concrete producers arbitrarily defined the high
strength concrete as the concrete having the 28-day cube strength of above 45
MPa when the normal weight aggregate is used. Clearly then, the definition of high
strength concreteis relative; it depends upon both the period of time in question, and the location (Neville, 1997).
The use of high strength concrete results in many advantages, such as
reduction in beam and column sizes and increase in the building height with many
stories. In pre-stressed concrete construction, a greater span—depth ratio for
beams may be achieved with the use of high strength concrete. In marine
structures, the low permeability characteristics of high strength concrete reduce
the risk of corrosion of steel reinforcement and improve the durability of concrete
structures. In addition, high strength concrete can perform much better in
extreme and adverse climatic conditions, and can reduce maintenance and repair
costs (Mehta and Monteiro,1993).
The progress in the manufacturing of increasingly high strength concrete
and their successful use in high rise structures over the last 20 years is well known.
Most recently, concretes having the strength of around 138 MPa are being used in
columns of high rise buildings and in a few European bridges. Concretes having the
strength up to 800 MPa have been produced in France for special purposes (Gjorv, 1992).
By far, the most common test carried out on concrete is the compressive
strength test. The main reason to understand this fact is that this kind of test is
easy and relatively inexpensive to carry out Mindess et al, 2003). Testing standard
requirements use different geometries of specimens to determine the compressive
concrete strength, j. The most used geometries are cylinders with a
slenderness equal to two and cubes. Shape effect on compression strength has
been widely studied and different relationships between the compressive strength
obtained for these geometries have been proposed, mainly from a technological
standpoint. Such approach eludes the fact that there is a direct relation between
the nucleation and propagation of fracture processes and the failure of the
specimen, indeed, experimental observations confirm that a localized micro-
cracked area develops at peak stress (Mier, 1984) or just prior to the peak stress
(Torreti et al, 1993). For this reason compressive failure is suitable to be analyzed by means of Fracture Mechanics.
1.2 Problem Statement
Eurocode 2 (FC2) gives many benefits such as less restrictive than British
Standards, extensive and comprehensive, logic and organized to avoid repetition
and the new R2 are claimed to be the most technically advanced codes in the
world. In Europe, all public works must allow the Eurocodes to be used for
structural design. Use of the EC2 will provide more opportunity for United Kingdom
(UK) designers to work throughout Europe and for Europeans to work in the UK.
Other than that, EC2 also give the economic benefit. It is expected that there will be material cost saving of between 0 and 5% compared to using BS 8110 (Moss et. al,2004). In future the Malaysia will use Eurcode as a standard in construction and
British Standard will eliminate. The testing result in this study can be made as a
reference in our future study ofEurocode in Malaysia.
According to the grade of concrete, EC2 allows benefits to be derived from
using high strength concretes, which BS8I 10 does not. Concrete strengths are
referred to by cylinder strengths, which are typically 1020% less than the
corresponding cube strengths. The maximum characteristic cylinder strength, fk permitted is 90N/mm2, which corresponds to characteristic cube strength of 150N/mm 2 (Moss et.al, 2002). However, the data are obtained from Europe and the
strength of cylinder test less than the corresponding cube test for material from
Malaysia is unknown? This study will conducted to make a comparison of cylinder
strength with cube strength using material from Malaysia.
The non-destructive tests used are mainly focus on rebound hammer test and
Ultrasonic Pulse Velocity test in order to check the accuracy of these testing
ompared to the actual concrete grade by compressive strength test.
1.3 Objectives of Study
The objectives of this study are:
i. To determine the compressive strength of high strength concrete using
British Standard and Eurocode approaches. ii. To check the strength of concrete using non-destructive test. iii. To compare the compressive strength of concrete using difference method
of test.
1.4 Scope of Study
The scope is related to the materials and equipments that involved in this
study and fulfill the requirement according to standards below:
i. The concrete grades covered are G40 and G50.
ii. The non-destructive test is mainly focus on rebound hammer test and Ultrasonic Pulse Velocity test.
iii. Method to cure the concrete is water curing. iv. Testing will be carried out on 7 and 28 day age of concrete. V. The testing will be carried out according to:
• C 192/C 192M - 05 Standard Practice for Making and Curing Concrete Test
Specimen in the Laboratory.
• C 136-05 Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates.
• C 19/C 39 M - 04a Standard Test Method for Compressive Strength of
Cylindrical Concrete Specimens.
• BS 1881: Patti 16: 1983 Concrete Compressive Test.
BS 1881:Part2O2: 1986 Rebound Hammer Test.
• BS 1881 :Part2O3: 1986 Ultrasonic Pulse Velocity Test.
CHAPTER 2
LITERATURE REVIEW
21 Introduction
Construction achievement always associated with the availability of suitable
material and its design. The recent tendency has been develop more accurate and
elaborate method of design which effect saving material. Due to industrial demand
and the development of high strength concrete have improved rapidly because the
industrial demand of new features in concrete have improved rapidly because the
industrial demand of new features in concrete member stiffness. The benefit of
increased in compressive strength is lower volumes and produce smaller design in
term of design perspectives (Jefily, 2008)
In recent year, high strength concrete has rapidly used on the construction
industry especially for buildings and infrastructures. The utilization of high strength
concrete has been spurred on by the superior mechanical properties of the material
and it cost-effectiveness. However, high strength concrete tends to be more brittle
or less tough than normal strength concrete under compression load (Neville, 2002).
High strength concrete provides high compressive strength but lower the
ductility than normal strength concrete. The low ductility and compressive strength
can be increased by applied the confining reinforcement to the concrete under
compression. However, these confining effects are most determined by
experimental test. When the general view of studies is observed, many cases are
found in which experimental results were investigated analytically and give a
feedback between experiments and analyses.
In future, Eurocode 2 (EC2) will replace the existing British code BS8 110 for
the design of concrete structure. For example, EC2 allows benefits to derived from
using high strength concretes, which BS8I 10 does not. Concrete strengths are
referred to by cylinder strength, which are typically 1020% less than the
corresponding cube strengths (Moss et.al 2002).
2.2 History of Concrete
The word concrete comes from the Latin word "concretus" which mean "to
harden". In Serbia, remains of a hut dating from 5600 BC have been found, with a
floor made of red lime, sand, and gravel. The pyramids of Shaanxi in China, built
thousands of years ago, contain a mixture of lime and volcanic ash or clay. The
Assyrians and Babylonians used clay as cement in their concrete. The Egyptians used lime and gypsum cement.
According to-Rubin (2008), during the Roman Empire, Roman concrete made
from quicklime, pozolanic ash/pozzolana and an aggregate made from pumice was
very similar to modern Portland cement concrete. The secret of concrete was lost for 13 centuries until in 1756, the British engineer John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate.
Portland cement was first used in concrete in early 1840s.
In modern times, the use of recycled materials as concrete ingredients is
gaining popularity because of increasingly stringent environment legislation. The
most conspicuous of these is fly ash, a byproduct of coal fired power plants. This has
a significant impact by reducing the amount of quarrying and landfill space required,
and, as it acts as a cement replacement, reduces the amount of quarrying and
landfill space required, and, as it acts as a cement replacement, reduces the amount
of cement required to produce a solid concrete. As cement production creates
massive quantities of carbon dioxide, cement replacement technology such as this
will play a huge role in future attempts to cut CO2
The lightweight foam concrete has been discovered for a very long time ago.
Two thousand years ago the Romans were making a primitive concrete mix
consisting of small gravel and coarse sand mixed together with hot lime and water.
They soon discovered that by adding anima blood into the mix and agitating it, small
air bubbles were created making the mix more workable and durable (Aldridge, 2005).
2.2.1 Background of High-Strength Concrete
Although high-strength concrete is often considered a relatively new
material, its development has been gradual over many years. As the development
has continued, the definition of high strength concrete has changed. In the 1950s,
concrete with a compressive strength of 34 MPa was considered high strength. In
the 1960s, concrete with 41 and 52 MPa compressive strength were used
commercially. In the early 1970s, 62 MPa concrete was being produced.
More recently, compressive strength approaching 138 MPa have been used
in cast-in-place buildings. For many years, concrete with compressive strength in
excess of 41 MPa was available at only a few location. However, In recent years, the
applications of high-strength concrete have increased, and high-strength concrete
has now been used in many parts of world. The growth has been possible as a result
of recent developments in material technology and a demand for higher-strength concrete.
21.2 Advantages and Disadvantages of High-Strength Concrete
High strength concrete gives a lot of advantages in construction industry. It's
provides an economical benefits as it used in a primary member such as structural
members. Designer can design small size of structural member and ease the
construction method. With an increase in concrete strength, the engineers can
design a smaller member that carries the same amount of load. Hence, it's become
more economical advantage and gives a lot of aesthetical values.
However, high strength concrete is brittle and will crack when it is under
tension. Thus, it has lower ductility compare to normal strength concrete. Besides,
careful materials selection is necessary these materials may need more materials in
lower quality. Furthermore, allowable stress design stress design stress design
discourages the use of high strength concrete and load factor and resistance design
will be used. The used of load factor and resistance will increase the size of the high
strength concrete member. High strength concrete-has more issue relating to the
lack of performances standard because lack of control to maintained special properties required.
23 Material
The material that produced high strength concrete is fine aggregate, water,
Portland cement and course aggregate. The proportion of mix design should be
accurate to get the actual grade of high strength concrete designed.
2.3.1 Fine Aggregate
Natural materials such as river sand and crushed fine stone are generally
used in concrete as fine aggregates. Most of the aggregates used in our country are
river and sand as fine aggregates. Fine aggregate S used for concrete should conform to the requirements for the prescribed grading zone as per IS: 383 - 1970.
The stone particles comprising the sand should be hard and sound. The sand
particles should be near cubical or spherical in shape. They should not be covered
with deleterious materials like clay slumps and should be clean. They should not
contain organic or chemically reactive impurities.
Natural or river sand may not conform to all the above requirements and
may have to be improved in quality. Improvements by washing, grading and
blending may have to be done before use at consumer end. But, in the case of
crushed stone sand / manufactured sand all these processes can be done in the
plant itself and quality sand can be made available to the consumer directly by supplier.
23.2 Water
Water is the important factor to determine the strength of concrete. In
construction work, extra in utilizing water is not efficient. Pouring and mixing
concrete process will be and uncomplicated but the strength of concrete will
become low. This situation affects the durability of concrete in future. Sea sand is
totally cannot used because sea sand contain high value of salt. The kind of sand is
not suitable for masonry construction because affect reinforcement bar of structure.
The usage of sea sand also can expose a concrete structure to sulphate attack which can cause expansion, corrosion and cracking in concrete.
2.3.3 Portland Cement
The properties of concrete depend on the quantities and qualities of
Portland cement. Because cement is the most active component of concrete and
usually has the greatest unit cost, its selection and proper use are important in
obtaining most economically the balance of properties desired for any particular
concrete mixture.
Type I/LI portland cements, which can provide adequate levels of strength
and durability, are the most popular cements used by concrete producers. However,
some applications require the use of other cements to provide higher levels of
properties. The need for high-early strength cements in pavement repairs and the
use of blended cements with aggregates susceptible to alkali-aggregate reactions are examples of such applications.
It is essential that highway engineers select the type of cement that will
obtain the best performance from the concrete. This choice involves the correct
knowledge of the relationship between cement and performance and, in particular,
between type of cement and durability of concrete.
23.4 Coarse Aggregate
The grading and shape of coarse aggregates and maximum size of coarse
aggregates have important effects on workability. The maximum size of coarse
aggregate must be selected for each specific concrete condition. The choice will
usually involve consideration of such factors as spacing of reinforcing bars,
minimum width of form, and methods of placing and compacting the concrete mass.
2.4 European Standard
European Standard is containing common structural rules for the design of building and civil engineering structures.
2.4.1 History of European Standards
In 1975, the Commission of the European Community decided on an action
programme in the field of construction, based on article 95 of the Treaty. The objective of the programme was the elimination of technical obstacles to trade and
the harmonization of technical specifications. Within this action programme, the
Commision took the initiative to establish a set of harmonized technical rules for
the design of construction works which, in a first stage, would serve as an
alternative to the national rules in force in the Member State and ultimately, would
replace them (European Committee for Standardization, 2002).
European programme, led the first generation of European codes in the
1980s. The Structural European programme comprises the following standard
generally consisting of a number of Parts (European Committee for Standardization, 2002):
EN 1990 Eurocode 0: Basis of Structural Design
EN 1991 Eurocode 1: Actions on structures
EN 1992 Eurocode 2: Design of concrete structures
EN 1993 Eurocode 3: Design of steel structures
EN 1994 Eurocode 4: Design of composite steel and concrete structures
EN 1995 Eurocode 5: Design of timber structures
EN 1996 Eurocode 6: Design of mansory structures
EN 1997 Eurocode 7: Geotechnical design
2.4.2 Eurocode 2
Eurocode 2 (EC2) is a set often Eurocode programme in European Standards
that contain the design standard for concrete structures.
112 gives many benefits such as less restrictive than British Standards,
extensive and comprehensive, logic and organized to avoid repetition and the new
112 are claimed to be the most technically advanced codes in the world. In Europe,
all public works must allow the Eurocodes to be used for structural design. Use of
the EC2 will provide more opportunity for United Kingdom (UK) designers to work
throughout Europe and for Europeans to work in the UK. Other than that EC2 also
give the economic benefit. It is expected that there will be material cost saving of
between 0 and 5% compared to using BS 8110 (Moss et. al,2004).
2.4.3 Comparison between EC2 and BS81I0
According to the grade of concrete, EC2 allows benefits to be derived from
using high strength concretes, which BS8 110 does not. Concrete strengths are referred to by cylinder strengths, which are typically 10-20% less than the
corresponding cube strengths. The maximum characteristic cylinder strength, Ik permitted is 90N/mm2, which corresponds to characteristic cube strength of 150N/mm 2 (Moss et.al , 2002).
As with BS81 10, EC2 uses a basic material partial safety factor, yn for concrete of 1.5. Several years ago the material partial safety factor for reinforcing steel in BS81I0 was reduced from 1.15 to 1.05. 112 uses a value of 1.15 although this is subject to a National Annex. This is unlikely to have any practical impact however as steel intended to meet the existing yield strength of 460N/mm2 assumed by BS81 10 is likely to be able to meet the 50ON/mm2 assumption made by
so that the design yield strength, f'd will be virtually identical (Moss et.al , 2002).
In designing for fire and cover, 112 does not considered this topic and in
making comparisons between BS81 10 and EC2 assumes that covers and dimensions
of members are largely unaffected by the changed design process.