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BTEC HIGHER NATIONAL DIPLOMA
In
CIVIL ENGINEERING
Edexcel International - UK
International College of Business & Technology
31 & 33, Hotel Road,
Mount Lavinia, Sri Lanka.
INDIVIDUAL PROJECT
By
A.F.HAZEEF AHAMED
MT/HNDCIVIL/05/103
Edexcel International - UK
ICBT Campus

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ACKNOWLEDGEMENT.
First of all I would like to express my gratitude with all my heart to
Almighty god for giving me the courage and the strength to complete this assignment.
As far as I concern I think it is my fortune following the course Civil Engineering at
ICBT. I think ICBT Campus is one of the institute seeks to give the best and updated
knowledge in theory and project works. This is the place where all the students’ future
is lightened up.
This dissertation was written as part of the final semester of the education as
Higher National Diploma in Civil Engineering. Many people have contributed to this
work. First of all, I want to express my gratitude to my senior colleges, they really gives
me great help and conduct which makes my report orientation and study scope smoothly
going. And then, I would like to say thanks to my friends He also helps me a lot this
time. He lends to me some reference books which are very helpful to my report.
A.F.HAZEEF AHAMED
MT/HNDCIVIL/05/103

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TTAABBLLEE OOFF CCOONNTTEENNTTSS
FRONT PAGE ………………………………………………………………………………………….
ACKNOWLEDGEMENT …………………………………………………………………………….
TABLE OF CONTENTS ......................................................................................................................... I
ABSTRACT............................................................................................................................................ V
1.0 INTRODUCTION ............................................................................................................................... 1
1.1. BACKGROUND................................................................................................................................... 1
1.2. AIM AND OBJECTIVES ....................................................................................................................... 4
1.3. METHODOLOGY ................................................................................................................................ 5
1.3.1. Literature review ...................................................................................................................... 5
1.3.2. Informal interviews .................................................................................................................. 5
1.3.3. Questionnaire survey................................................................................................................ 5
1.3.4. Field survey.............................................................................................................................. 5
1.4. SCOPE AND LIMITATION .................................................................................................................... 6
1.5. STRUCTURE OF DISSERTATION.......................................................................................................... 6
2.0 LITERATURE REVIEW ................................................................................................................... 7
2.1. INTRODUCTION ................................................................................................................................. 7
2.2. DEMAND FOR HOUSING IN SRI LANKA .............................................................................................. 7
2.3. BUILDING SYSTEM ............................................................................................................................ 9
2.4. PREFABRICATED SYSTEM ................................................................................................................ 12
2.4.1. Types...................................................................................................................................... 13
2.4.2. Process.................................................................................................................................... 14
2.4.3. Material .................................................................................................................................. 15
2.4.4. Advantages and disadvantages............................................................................................... 16
2.4.5. Prefabrication of precast concrete .......................................................................................... 20
2.4.6. Types of precast structures ..................................................................................................... 23
2.4.7. Types of precast concrete elements........................................................................................ 25
2.4.8. Advantages of Pre-cast Concrete system in prefabrication .................................................... 27
2.4.9. Disadvantages of Precast Concrete system ............................................................................ 30
2.5. PREFABRICATION APPLICATION IN BUILDING ELEMENTS................................................................. 32
2.5.1. Foundations ............................................................................................................................ 32
2.5.2. Walls ...................................................................................................................................... 32
2.5.3. Floor and roof......................................................................................................................... 32
2.6. SLAB SYSTEM IN HOUSING CONSTRUCTION ..................................................................................... 33
2.6.1. Conventional slab system....................................................................................................... 33
2.6.2. SBS slab system ..................................................................................................................... 35
2.7. KIT FORM HOUSE............................................................................................................................ 36
2.7.1. Erection of a kit form house ................................................................................................... 37
2.7.2. Benefits of the kit houses ....................................................................................................... 37
2.8. SUMMARY....................................................................................................................................... 38

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3.0 RESEARCH METHODOLOGY ..................................................................................................... 39
3.1. INTRODUCTION ............................................................................................................................... 39
3.2. LITERATURE REVIEW...................................................................................................................... 39
3.3. INFORMAL INTERVIEWS .................................................................................................................. 39
3.4. QUESTIONNAIRE SURVEY ................................................................................................................ 39
3.5. FIELD SURVEY................................................................................................................................. 40
3.6. QUESTIONNAIRE STRUCTURE.......................................................................................................... 40
3.7. LIMITATION OF THE STUDY............................................................................................................. 42

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AABBSSTTRRAACCTT
Prefabrication has been used extensively and widely for many years around the world. It
has been widely adapted in housing construction. The main reason in adopting this
system particularly for housing construction is to boost the development of low cost
housing project for the lower income group.
This project was conducted to study the basic concept of and application of
prefabricated system in building construction. The study further assessed the benefit of
the using prefabrication system in building construction. The methodology adopted for
the study includes literature review, informal interview, field survey and using
questionnaire survey. An informal interview was carried out to facilitate on designing
the questionnaires. These questionnaires were then distributed to the respondents which
represent the professional in construction industry that have experience and knowledge
on the precast concrete technology. The study concluded that the prefabrication system
is viable alternative construction method that can improve construction industry with
regard to the achieving better quality of works and increasing productivity. The study
has determined that the adoption of this technology can greatly benefit the building
industry in various aspects such as reducing the construction cost, better planning and
design coordination. Speed of construction. Speed of construction, minimising
manpower involved in the project.
Key words: prefabrication, precast concrete

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1.1. BACKGROUND
Buildings should be designed with the system in mind, to best utilize the advantages of
the particular system. Before going to accomplish the construction work, the builder has
to choose a suitable system according to the client requirement and with the available
resources. In addition, the chosen system needs to be well specified to prevent major
problems during construction. Moreover, a poorly specified system could result in
misalignment of components, or incompatibility of the components with other systems,
structure, or existing conditions (Obiso 1997). Prefabricated systems have been widely
adopted in housing construction for the purpose of modular coordination, efficient use
of time and assure the quality of a product. Unlike the conventional practices of
construction, prefabrication guarantees the production of high quality building
components and facilitates the fast track construction. Chan (1998) mentioned that, the
quality of the prefabricated items is usually higher than the in-situ components and
speed of the construction is comparatively high.
Prefabrication has been used extensively and widely for many years around world (Hao
et al 2002).The application of pre fabrication techniques has signified a turning point in
the construction industry. Over the years, prefabrication has evolved to be one of the
most remarkable construction techniques in the industry (Chan et al, 2002). Unlike the
traditional concreting methods, prefabrication guarantees the production of high quality
building components and facilitates the fast track construction by removing those
concreting works from critical path into non-critical and dirty in-situ works into clean
all-weather precast factory production, leaving the assembly work to be performed on
site (Wong and Yau 1999 ). The application of prefabrication techniques has brought a
profound change in the development of the construction industry worldwide. Several
advantages are accrued from its use including less time and reliance on site labour,
easier site inspection, as well as greatly improved design details and quality control. A
wide use of prefabrication products would help to overcome many of the hurdles

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inherent in traditional in situ construction, and engender move technically feasible and
cost effective installation. (Chan et al, 2002).
With the labour shortages prevalent in the building industry, prefabrication together
with the greater use of standardization and modular flat designs are frequently
considered in the design and construction of domestic buildings (Chan 1998). It was
clarified by Elliott (2000) that, a particular combination of material could be needed to
meet architectural requirement or speed of construction, but it may or may not have to
act compositely to do so. As it is common to all prefabrication, most of the work carried
out in the factory, leaving little to be done on-site. This increase the likelihood of more
efficient, high quality and faster construction being achieved (Rosenfeld 1994).
In Sri Lanka, the usage of prefabricated concrete in housing construction has been in the
increase after the Tsunami. The annual new demand for houses in Sri Lanka is
estimated to be around 100,000. In addition, there is an estimated housing shortage of
350,000. Further, about 30 % (about 1.3 million) of the existing houses are semi-
permanent, improvised, or unclassified needing substantial improvements. In addition to
individual housing, government supported programmes and private sector investments
are expected to provide 645,000 housing units during the ten year period up to 2016
(Central Bank Report, 2006). The construction of houses damaged by the tsunami will
pose a gigantic challenge in 2005. About 65,000 houses are estimated to have been
completely destroyed and 44,000 houses partly damaged by the tsunami in December
2004 (Central Bank Report, 2004).
The people who lost their shelters needed to resettle in permanent homes that they could
call their own and it should be build within the very short period, if their lives are to
regain any sense of normalcy. But how does one go about re-building? In this situation
any one can realize that the speed and cost as the main parameters of reconstruction
task. What are the low cost housing options that are available in Sri Lanka now and
what are building methods available to build those houses very quickly? To increase the
speed of the construction the contractors tense to use pre-fabricated system. The
National Engineering Research and Development (NERD) Centre attached to the State
Engineering Corporation (SEC) under the Ministry of Science and Technology has

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come forward with several short and long term solutions, using innovative and cost
effective construction technology. Columns, beams, door frames, window frames and
many other components are pre-made out of concrete (The Sunday Observer, 2005). But
there is a question arising that, while achieving the speed of the construction by using
precast concrete elements, can they achieve the required quality of the building? If they
used prefabricated system, what would be the effect for the environment? There is a
labour shortage in construction industry in Sri Lanka. Therefore to overcome this
problem the contractor has to select a building system which required minimum labour
involvement. By doing this research it is intended to identify the benefit of pre
fabricated concrete structures in terms of cost, time, quality, environment friendly and
labour saving against the conventional system in Sri Lankan housing construction.
In a concrete frame building, floor construction is the most time and cost element,
representing about 70% of the super structure cost (Domel & Ghosh 1990; Goodchild
1997; Idrus 2001; Passiki et al, 1995). In addition, Elliot (2000), said that pre-stress,
precast concrete units provide the economical flooring systems in worldwide.
Considering the above information if the contractors use pre-stress concrete floor
system to housing construction such as suspended beam slab (SBS) instead of in-situ
concrete slab, how it is effective in terms of cost time and quality?

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1.2. AIM AND OBJECTIVES
The study is carried out to examine the usage of prefabricated system in the housing
construction. The objectives of this study are as follows:
 To study the basic concept of prefabrication system in building construction
 To evaluate the benefit of using prefabricated system in Sri Lankan housing
construction
 To ascertain the cost effectiveness of the prefabricated floor system against
conventional slab system in housing construction

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1.3. METHODOLOGY
1.3.1. LITERATURE REVIEW
The study was initiated through a comprehensive review and an empirical study. A
literature method was carried out as preliminary study in gaining information about the
research topic and recently prefabricated system applied in the construction industry. It
is done by referring to many sources such as published books, articles in journals and
papers, other published research works, academic and research magazines, newsletters,
brochures and information from the internet.
1.3.2. INFORMAL INTERVIEWS
The empirical study used informal interviews and questionnaire. The informal interview
with experience personal regarding the usage of this prefabricated system was
conducted to obtain ideas and data valuable for designing the questionnaire.
1.3.3. QUESTIONNAIRE SURVEY
Questionnaires were distributed to gauge respondent’s opinion regarding the beneficial
in using this prefabricated system in the construction. It was distributed to the
respondents involve in the construction industry in Colombo area through electronic
mail and by hand. After the data had been collected, detailed analyses were done using
frequency analysis and Relative Indices RI technique.
1.3.4. FIELD SURVEY
Simple field survey was conducted to ascertain the cost effectiveness of the
prefabricated floor system against conventional slab system in housing construction.

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1.4. SCOPE AND LIMITATION
The scope and limitation of this study is confined to housing construction only. The
research was based on the experience of local developers, engineering and architectural
consultants, building contractor, manufactures, quantity surveyors and government
building authorities on the usage of prefabricated system. The study considered only on
the use precast concrete element in housing construction. The data collected are only
confined to the respondents within the Colombo area. The identification of the cost
saving of prefabricated system is done only to the slab in two story housing projects.
1.5. STRUCTURE OF DISSERTATION
The dissertation is consisting of five chapters. First chapter discussed on the background
of the research, objectives, scope and limitation of the research and the research
methodology adopted to achieve the objective of the research.
Chapter 2 discusses about the building system and the basic concept of the
prefabricated system in building industry. Also the advantages, disadvantages of the
prefabricated system are discussed in this chapter.
Chapter 3 discussed in details the research methodology adopted for the study.
Chapter 4 illustrates the detail analysis of collected data and discuss about the research
findings.
Chapter 5 conclude the study and makes recommendations to the usage of
prefabricated system in housing construction in terms of design and total building cost.

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2.1. INTRODUCTION
This chapter looks into key definitions, concepts, practices and procedures relevant to
this study. The first part of this report 2.2, discuss about the demand for housing in Sri
Lanka. In section, 2.3 discussed about the building system and different types of
building system adapted in other countries. Prefabricated system, types of prefabricated
system and process of prefabrication and the advantages and disadvantages of
prefabrication are described briefly in section 2.4. The section 2.5 described about the
prefabrication building methodologies for housing. Section 2.6 discussed about the slab
system in housing construction. Section 2.7 is consisting of the details of kit house. The
summary of this chapter is described in section 2.8.
2.2. DEMAND FOR HOUSING IN SRI LANKA
In 1948, the United Nation Declaration of Human Rights formally recognised the right
to decent housing for all human beings (Harun 1996). In Sri Lanka the demand for
houses and urban infrastructure is expanding rapidly with the population growth and
urbanisation. The population is growing at 1.1 percent annually, where as the urban
population is growing at a higher rate of 3 percent (Central Bank Report, 2006). Many
of developing countries faces higher urban population growth due to the migration of
population from rural to urban areas took place due to economics reasons. Hence, this
high population growth in developing countries has given rise to housing problems
where proper and adequate accommodation is an important need for every human being
(Rahim 2004). The annual new demand for houses in Sri Lanka is estimated to be
around 100,000. In addition, there is an estimated housing shortage of 350,000. Further,
about 30 percent (about 1.3 million) of the existing houses are semi-permanent,
improvised, or unclassified needing substantial improvements. In addition to individual
housing, government supported programmes and private sector investments are
expected to provide 645,000 housing units during the ten year period up to 2016
(Central Bank Report, 2006).

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On 26th
December 2004, an earthquake off Sumatra triggered a massive Tsunami that
devastated around two thirds of the coast of Sri Lanka and entire fishing communities
disappeared from some areas. A large proportion of economic losses is concentrated in
housing, tourism, fisheries and transportation while total losses were estimated to equal
4.4 percent of the GDP (Prabodha 2005). The construction of houses damaged by the
tsunami will pose a gigantic challenge in 2005. About 65,000 houses are estimated to
have been completely destroyed and 44,000 houses partly damaged by the tsunami in
December 2004 (Central Bank Report, 2004). Construction of 61,000 houses has been
completed by end of 2006 and construction of balance houses was in progress (Central
Bank Report, 2006). The people who lost their shelters needed to resettle within the
very short period. Therefore, it was recognised that the Speed as the main parameter of
reconstruction task. Rahim (2004) concluded that, the usage of prefabricated system has
been implemented due to the needs to provide housing for the people in a short period
of time given.
The demand for housing in Sri Lanka is very high in future. Therefore, the system that
the contractor going to use to build the houses is take major part in terms of achieving
the best quality, reasonable time and cost. According to the Daily Mirror (2005), the
prefabricated housing systems could be the ideal fast track solution in the process of
building new houses to compensate the totally destroyed houses from the Tsunami
devastation.

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2.3. BUILDING SYSTEM
The building should be designed with the system in mind, to best utilize the advantages
of the particular system. In addition, the chosen system needs to be well specified to
prevent major problems during construction. Moreover, it said that a poorly specified
system could result in misalignment of components, or incompatibility of the
prefabricated components with other systems, structure, or existing conditions (Obiso
1997). A building system is a highly engineered method of producing buildings or
building components in an efficient and cost effective manner. The use of building
systems is common in many different types of residential and commercial construction
(Wikipedia, 2007a). As foster (1997,p.20) mention, the component parts of the building
fabric, whatever the form of construction, must be fabricated and then assembled or
erected on the site to produce the completed building. These processes must be
organised and the manner of organisation differs from country to country and from time
to time in any particular country.
Foster (1997, p.26) identified some type of building systems developed in Great Britain.
Those are as follows,
 Post-traditional or conventional building
 Rationalised building
 System building
 Component building
Pre-assembly, prefabrication, modularisation, system building and industrialised
buildings are the terms which have been frequently used to describe that the
manufacture of building components are constructed either on-site or off-site in a
factory covering manufactured, modular and pre-cut or pre-engineered systems.
Although the terms, are often interchangeably used, their precise definitions depend
heavily on the users’ experience and understanding, which vary from countries to
countries.
Off-site fabrication is a topic of international interest and provides an effective
construction technique in terms of quality, time, cost, function, productivity and safety.
It is adopted worldwide as the ideal means of producing an immense array of elements

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from structural members, cladding units, and bathrooms to fully-finished modular
buildings. (Hao et al, 2002).As an organisational process industrialisation may be
applied to any method of building and whether applied to traditional methods or factory
methods will introduce these four characteristics, a mechanised and continuous
fabrication and assembly process to speed up production and reduce labour
requirements, a standardisation of components to reduce cost and facilitate continuous
production and a properly integrated system of design, fabrication and assembly to
speed up the whole building process, with feedback from the fabricating and assembling
process to the designer so that changes and developments may be made leading to
reduced cost and greater productivity (Foster 1997, p.24).
The meaning of industrialisations is to build on site with elements or components
produced by series in plants. In addition, industrialization of building means that these
components can be assembled together even though they are produced on different
plants (Rahim 2004). For the building industry industrialisation involves the
rationalisation of the whole process of buildings (which includes the process of design,
the forms of construction used and the method of building adapted), in order to achieve
an integration of design, supply of materials, fabrication and assembly so that building
work is carried out more quickly and with less labor on site and, if possible, at less cost
(Foster 1997, p.24).
Generally, there are four types of building system available in Malaysia, namely
conventional, cast in-situ, prefabricated and composite building system (Chew 1986).
As in addition, each building system is represented by its respective construction
method which is further characterized by its construction technology, functional and
geometrical configuration (Walled et al 2003, cited Rahim 2004). Over a five-year
period, hundred of proprietary system where brought into existence, but few had any
real chance of achieving the size or continuity of orders that were essential to make
them viable. The use of industrialized system was not confined to housing; a proportion
of offices, factories, hospitals, stores and schools were constructed by industrialized
methods (Seeley 1973, p.68). Rahim (2004) concluded in his research saying that the
concept of prefabrication system as one of the industrialised building system.

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Prefabricated housing Systems have become the conventional way to build a one or
two-story commercial, community or industrial building world-wide. Technological
advances in products and materials, combined with new manufacturing techniques, have
led to the development of structural systems, which are compatible with ordinary
construction materials (Daily Mirror, 2005). Prefabricated housing has been used in the
UK during periods of high demand, such as after the World Wars and during the slum
clearances of the 1960s. In total about one million prefabricated homes were built
during the 20th century, many of which were designed to be temporary. However,
problems arose over the quality of building materials and poor workmanship, leading to
negative public attitudes towards prefabrication (Parliamentary office of science and
technology 2003, cited Suriyaarachchi 1998). There has been a great improvement in
prefabricated housing over the past decades and it is becoming a valid alternative to
traditional housing (Wikipedia, 2007a).
The details that given by the construction relative professionals, there are four types of
building systems are identified in Sri Lanka. Those are traditional, insitu, prefabricated
and composite system. According to the mentioned information of the prefabricated
system, it is clearly understood that the application of the prefabrication system in
construction gives several advantages such as reduce the construction time and cost,
while achieving the best quality. Because of the huge demand for the housing in Sri
Lanka, the application of prefabricated system will become effective in building those
houses. Out of the all types of building system in Sri Lanka, the prefabricated system is
to consider my research in a comprehensive way.

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2.4. PREFABRICATED SYSTEM
Prefabricated system of construction means breaking a whole housing unit into different
components such as the floors, the walls, column, beam, roofs, etc. and having these
components separately prefabricated or manufactured in modules or standard
dimensions in a factory. The components are then assembled and erected on the site and
properly joined to form the final units (Chew 1986). Prefabrication is the practice of
manufacturing the components of an assembly in one location and assembling them in
another. This practice was widely used in the construction of prefabricated housing
during the 20th and 21st centuries. In theory, using a product made in a factory would
save time on-site and improve quality. However, prefabricated housing and many other
items acquired a certain level of stigma because of flimsy designs and low cost. There
has been a great improvement in prefabricated housing over the past decades and it is
becoming a valid alternative to traditional housing (Wikipedia, 2007a).
By using a prefabricated building system, as much as 50% of the total construction time
can be cut out of the schedule (Mark 1993). A shorter production time not only cuts
down direct and overhead costs, but also allows the house to be occupied sooner, as
recognized significant in the case of the large-scale flat production programmed in
Hong Kong (Chan et al, 2000). In addition he said that, in most cases, the saving in
construction time due to the employment of prefabricated elements has also significant
economic value to both the client and the contractor. As many prefabrication
technologies deliver a better product because building is done in a quality controlled,
sheltered environment, the move to more prefabrication in construction industry is
inevitable. It is seen as one of the tenets of improving construction in the 21st
century
(Egan 1998; Chan & Chan 2002). This is also echoed by Ranford (2000), ‘a much
greater emphasis on off-site assembly was one of the key ingredients to changing the
construction culture to retain and recruit talent and at the same time deliver
improvements in performance required by increasingly demanding clients.’

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2.4.1. TYPES
Mainly there are two types of prefabricated systems in the market (Chew 1986):
a) Fully Prefabricated Systems
b) Partially Prefabricated Systems
2.4.1.1. FULLY PREFABRICATED SYSTEMS
Fully prefabricated system is referring to the components produced in the factory and
transported to the construction site for erection. Fully prefabricated system can be
grouped under 3 categories based on these methods:
2.4.1.1.1. BIG PANEL SYSTEM
This consists of pre-cast wall (load bearing type) and slab elements. A heavy capital
outlay is required for this system because the usage of heavy moulds and machinery in
concrete mixing, transporting, lifting, storing and assembling. A maximum turn over
per day is a must in the production line because of the heavy initial capital cost for each
of the metal mould. In the operation which consists of preparing the bed, casting and
curing the concrete and stripping the moulds can be done within the shorter time.
Concrete is subjected to heat curing for hardening process for the panel can be lifted in
about three hours instead of the normal curing time.
2.4.1.1.2. THE FRAMING SYSTEM
The structural members such as the columns and beams are cast together to form a
frame. However the floors are cast separately as panels. Then the members are
transported to the site for erection and fixing. As for the wall, it can be non-load
bearing light weight material, hollow blocks and conventional bricks. The example of
components in this system is prefabricated bathrooms, toilets, staircases, balconies,
parapets, facades etc. The components can be fixed onto the main units.

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2.4.1.1.3. MODULE SYSTEM
This system involves the casting of a unit in the form of module or modules.
Several of openings for doors, windows can be pre-formed in the steel mould before
casting.
2.4.1.2. PARTIALLY PREFABRICATED SYSTEMS
Partially prefabricated system is a type of system in construction where certain
elements that can be standardised are prefabricated in the factory while other
components are cast-in situ. In this construction method, the assembly of pre-cast
elements involve are floor slabs, wall, bathroom, staircase for incorporation into the
main unit. The columns and beams usually cast-in situ because it is easier and less
time-consuming. According to Chew (1986), this system usually give a more rigid
construction and better water tightness characteristic which are not usually found in Big
Panel and Farming System. The advantage of this system is in its low initial investment
because it is not necessary to have full automation factory with its supporting heavy
machineries.
2.4.2. PROCESS
Prefabricated system of construction means that breaking a whole housing unit into
different components such as the floors. The walls, columns, beams roofs etc. and
having these components separately prefabricated or manufactured in modules or
standard dimensions in a factory. The components are then assembled and erected on
the site and properly joined to form the final units (Chew 1986). The Figure 2.1 shows
the process of prefabricated system from design to form a final unit

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Figure 2-1: The basic concept of prefabricated system
(Source: Rahim 2004)
2.4.3. MATERIAL
In Sri Lanka Steel, timber and precast concrete are the material widely used in the
prefabricated construction. Steels are economical to use only in wide span and high load
bearing structure such as where houses, store room and car park etc. because of the
short span the timber and precast concrete are suitable and economical in the pre
fabrication of the housing construction. But due to the unavailability of the timber and
government rules for cutting the trees, now days the timber is not extensively used in
construction. Precast concrete unites are very commonly used in the prefabricated
housing construction in Sri Lanka due to the several reasons such as easy availability of
material, economical, quality, etc..
Hybrid Concrete Construction (HCC) is a method of construction which integrates
precast concrete and cast in-situ concrete to take best advantage of their different
inherent qualities. The term hybrid concrete construction (HCC) describes the

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combination of concrete with other materials (Goodchild 1995).The accuracy, speed and
high-quality finish of precast components can be combined with the economy and
flexibility of cast in-situ concrete. Hybrid concrete technology embraces a number of
different forms of structural frame, but in all cases precast concrete and cast in-situ
concrete elements are used where they are most appropriate for the project. The results
are remarkable: faster construction and considerable cost savings – in some cases of up
to 30% compared with conventional structural frame systems.
Figure 2-2: Concept of Hybrid construction
(Source: Trent Concrete Photo courtesy)
2.4.4. ADVANTAGES AND DISADVANTAGES
There are some advantages and disadvantages in prefabricated system. Those are
describing in detail below.
2.4.4.1. ADVANTAGES OF PREFABRICATED SYSTEM
Adoption of prefabrication system has many merits in the context of availability of
materials, labour and technical skills. Advantages of prefabrication are identified by
Adlakha & Puri (2003) as follows.
(1) In prefabricated construction, as the components are readymade, self-supporting,
shuttering and scaffolding is eliminated with a saving in shuttering cost.
(2) In traditional construction, the repetitive use of shuttering is limited, as it gets
damaged due to frequent cutting, nailing etc. On the other hand, the mould for the

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precast components can be used for large number of repetitions thereby reducing, the
cost of the mould per unit.
(3) In prefabricated housing system, there is saving of time as the elements can be
casted before hand during the course of foundations being laid and even after laying
slab, the finishes and services can be done below the slab immediately. While in the
conventional in-situ RCC slabs, due to props and shuttering, the work cannot be done,
till they are removed. Saving of time means saving of money.
(4) In prefabricated construction, there is better quality control, shape and size of
precast elements. Therefore, in structural design, full advantage of properties of cement
and steel can be exploited. There is disciplined use of scarce materials like cement, steel
and timber.
(5) In precast construction, similar type of components are produced repeatedly,
resulting in increased productivity and economy in cost too.
(6) In precast construction, the construction is not affected due to weather, rain, wind
etc.
(7) In prefabricated construction, the work at site is reduced to minimum and therefore,
work is qualitatively better, more reliable and clean.
(8) Because of faster completion and reduction in time period of construction the houses
can be occupied earlier, which means early return of the investment.
Chan et al, (2003) recommends that, prefabrication will contribute to improved build
ability and associated efficiency gains in terms of time, cost, quality, safety and
environmental targets. Some of the benefits of prefabrication techniques are listed
below:
(a) Higher productivity levels of construction trades;
(b) Cost savings at every level of the supply chain due to mass production, e.g. labour
and materials costs;
(c) Faster return on investment for the client;
(d) Reduced programme durations for fixing and erection operations;
(f) Savings in space allocated to materials storage;

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(g) Better quality control leading to more accurate profiles and dimensions of
components;
(h) Less materials wastage because of fewer defective products;
(i) Safer working environment at prefabrication factories;
(j) Enhanced teamwork spirit and manufacturing ethos under a repetitive production
process;
(k) More efficient testing requirements of the products at the manufacturing facility than
at the construction site;
(l) Less influence of site tasks by inclement weather conditions;
(m) Re-engineered project delivery and supply chain system based on wide scope of
prefabrication and preassembly; and
(n) Application to public and private sector housing, commercial building and road
construction projects in collaboration with industry and government partners.
A number of significant benefits provided by prefabricated elements comparing with
on-site building erection process as shown in the below table.

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Table 2-1: Comparing the benefit of prefabrication and on-site erection
(Source: Hao et al. 2002)
Factor Prefabrication On-site
Quality
In a climate-controlled environment
using efficient equipment operated by
well-trained people.
Uncertain weather can result in less-
than expected construction.
Speed Speedy process (up to 70% less)
Time consuming. The process can be
delayed by weather or scheduling
conflicts.
Cost
Greater control over manufacturing
results dramatically reduces the chance
of cost overruns.
Uncontrollable variables such as
weather and scheduling can increase
the construction cost
Versatility Less More
Site space
Panels arrive on a flat-bed trailer and are
installed with sufficient listing plants.
Bigger space is needed. In addition
costly scaffolding is often necessary for
installation.
Site
refuse
Less waste is generated at the site.
A significant amount of waste
produced and removed from the site,
which often adds to cost.

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2.4.4.2. DISADVANTAGES OF PREFABRICATED SYSTEM
There are some disadvantages also in prefabrication. Following are some disadvantages
identified by Adlakha & Puri (2003)
(1) As the precast elements have to behave monolithic on erections, extra reinforcement
may be necessary in some cases.
(2) Extra reinforcement is required to take care of handling and erection stresses.
(3) Temporary props may be required in some cases, before the in-situ concrete joints
achieve strength.
(4) The cracks may develop at the joints between the precast and in-situ concrete due to
shrinkage and temperature stresses. To overcome them, extra steel is required across the
joint.
(5) As there are chances of leakage/seepage through the joints between the precast
components, extra care is required to make them leak proof.
2.4.5. PREFABRICATION OF PRECAST CONCRETE
Prefabrication of concrete structures is one of the most remarkable developments in the
construction process of concrete structure in the last two decades (Bruggeling &
Huyghe 1991). According to Shahrul et al, (2003), numerous construction projects in
Malaysia have utilized prefabrication of pre-cast concrete technology structure
especially when the project requirement is to build in shorter period of time within the
given budget and quality workmanship. The major reason for acceptance of such system
is basically supply and cost of labour, speed of construction, wastage control etc. But
the context of Sri Lanka precast concrete construction was introduced during the period
of 1969 in Colombo port commission. But it was slow improvement for the introduction
construction stage. In 1979s pre stress concrete roof beam which span 20 ft from the
basic components for the school type building frame which is marketed successfully by
the State Engineering Corporation (SEC). Its versatility has been proved by its
beneficial use in low cost housing projects (Sri Lankan Building research, 1979).
Much more use of precasting and of-site prefabrication should be encourage for
reducing construction duration and maintaining consistently high quality standard of
the product (Chan et al, 2003). Usage of precast concrete technology in building

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construction has contributed various benefits in terms of cost, time, manpower,
environment and quality (Rahim, 2004). Prefabrication is closely related to the
development of the pre-casting industry, which in turn is one of the important steps
towards industrialisation of the building industry. The cost of manufacturing of the pre-
cast elements should be low as possible. This result in the necessity of repetition of the
same production cycle on every working day (Bruggeling & Huyghe, 1991). To date,
the extensive use of prefabrication includes the production of pre-cast façades, pre-cast
staircases, semi-pre-cast slab, pre-cast partition wall and fabric reinforcement (Wong &
Yau 1999).
As mention by Idrus & Newman (2002), designers have a wide choice of structural
system for concrete frame buildings. They can choose from three basic types available:
in situ, pre-cast or hybrid construction. Bruggeling & Huyghe (1991) discussed that, it
has to be realised that the preparatory period of a prefabricated concrete structure is
totally different from that of concrete structure cast in situ. This means that the different
discipline will have to be followed by the architect and the designer in case of pre-cast
concrete structure. Not only the construction time – on the site – will be considerably
reduced, but the preparatory period should already be over when manufacturing of the
element starts. If the concrete structure is cast in site the preparation process may
overlap the construction process. In the case of prefabrication this overlap is impossible.
All the decision that influence the dimension and the shape of the concrete structure
must be taken a long time before the construction starts with the activities on the site.
If the parties involved in this process are skilled, the erection of prefabricated concrete
structure will take place with fewer problems than in the case of in situ concreting. All
the aspect of the design is, as a rule, considered that a basic condition for successful
prefabrication is a well-organised team of architect, designer, contractor and
manufacturer. (Bruggeling & Huygh 1991). For high rise development it was found that
generally the precast concrete where erected more quickly and cheaply than in situ
concrete system. In contrast, in situ concrete system often provides the cheaper method
for low rise dwelling although not the quickest. This result mainly from reduction in
repetition and standardisation in low rise housing compared with high rise construction.

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Furthermore, the high initial cost of precast concrete factory and its high overheads tend
to make precast concrete unit expansive. Timber and steel frames have both been used
extensively for low-rise housing and have the benefit of fast erection time. Both
materials are relatively expensive (Seeley 1973, p.69).
Most popular building construction technology among various practices is the use if
prefabricated building components such as columns, beams, slabs, and items required to
roof structure. Most commonly the buildings are consist of structural skeleton to carry
and transfer the load. The precast usage was mostly significant on the low rise buildings
and package type housing units which was repetitive type construction. Apart from that
one other popular concept was the use of “building frame” for the low rise buildings,
housing units, secondary buildings and ware houses. The most significant feature with
this method was cheap rather than the conventional method, while it provides a simple
yet steady permanent structure, which could be erect within a short period of time
(Ediriweera 1988, cited in Suriyaarachchi 1998).
There are only few companies are manufacturing precast unites for housing
construction. Namely State Engineering Cooperation (SEC) and International
Construction Consortium (ICC) are the major two companies manufacturing precast
units for building construction. ICC introduces an effective alternative to in-situ
concrete slab call Suspended Beam Slab (SBS) pre stressed concrete floor system. This
system also coming under the category of partially pre-fabricated system. In this
construction method, the columns and beams are usually cast insitu. Considering the
span and the load bearing capacity the number of pre stressed beam using this system is
varies. There are single beams, double beams and continuous beams are available for
this type of flooring system. But single beam system is enough in housing construction
up to 4 meters of maximum span. Due to the several advantages, the application of SBS
concrete floor system is rapidly growing in building construction in Sri Lanka.
National Engineering Research and Development (NERD) also producing the same
type of slab system like SBS slab system. This system is called as NERD Floor-slab
System.

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2.4.6. TYPES OF PRECAST STRUCTURES
(Elliott 2000; Rahim 2004) stated that there are three basic types of precast structures:
1. wall frame
2. portal frame
3. skeletal frame
2.4.6.1. WALL FRAME
The precast structure consist of vertical wall and horizontal slab units only. It is used
extensively for housing, offices, hospitals, multi storey hotels, commercials, retail units,
shopping complexes etc.
2.4.6.2. PORTAL FRAME
The precast structure consists of columns and roof rafters only. It is mainly constructed
for single storey retail warehouse and industrial manufacturing facilities.
2.4.6.3. SKELETAL FRAME
It is consists of columns, beams and slabs particularly for low rise buildings and with
a small number of walls for high rise building. It is used in constructing schools,
commercial, offices and car parks. The Figure below shows an example of skeletal
structure.

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Figure 2-3: Skeletal structure
(Source: Rahim 2004)
Legend:
i. Main suspended beam
ii. Hollow core unit
iii. Internal Rectangular beam
iv. Gable spandrel beam
v. Gable beam
vi. Main edge beam
vii. Landing support beam
viii. Staircase and landing
ix. Ground beam
x. Column
xi. Wall
xii. Double tee unit
xiii. Internal beam
xiv. Main edge spandrel beam

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2.4.7. TYPES OF PRECAST CONCRETE ELEMENTS
Rahim (2004) identified that, various precast concrete components have been
introduced through technology transfer from developed countries and research by the
local manufacturer. There are varieties of precast concrete components for use in
building construction available in the market such as:
 Hollow Core Slab
 Precast Solid Plank
 Precast Half Slab
 Precast Parapet and Facade
 Precast Beam
 Precast Column
 Precast Staircase
 Precast Double Tee Slab
 Precast Waffle Slab
 Precast Load Bearing Wall
Hollow core slab Solid plank Beam Half slab

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Half Slab Staircase Facade Wall Panel
Column Waffle Slab Double Tee Slab
Figure 2-4: Example of precast concrete components
(Source: Rahim, 2004)

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2.4.8. ADVANTAGES OF PRE-CAST CONCRETE SYSTEM IN
PREFABRICATION
The following are the advantages of adopting precast concrete in the construction.
2.4.8.1. ENVIRONMENT FRIENDLY
The use of conventional timber formwork are reduced to minimum or even eliminated
and less usage of scaffolding through the use of prefabricated components or system
formwork for site casting. This contributed less demand of timber and therefore reduced
the cutting of trees activities in our forest. It also produces minimum wastage due to
factory controlled prefabrication environment. There are also show a cleaner site with
less dumping of unwanted materials and debris within the site compound. A well-
managed and neater working environment at site can be accomplished. Since the
components are made in factory, there will be minimal noise and air pollution causes by
machineries, vehicles and during erection of structural works. All wasted concrete and
rejected in production can be recycled in the factory again and it being re-used in
production. This may minimises the dumping activities to the land fill in our country.
2.4.8.2. SPEED AND TIME SAVING
The introduction of prefabrication technology which replaces in-situ construction, it
helps to reduce the duration of the project. As the prefabricated components are being
cast at factory or off site yard, the preparation work can proceed concurrently. Once the
precast components arrived at the work site, installation works begin from unloading the
material from the transporter to the required location. According to the statistic from a
manufacturer the average rates of 40 to 50 pieces of precast components within eight
hours of working days are sent to site for installation. This innovative technology can
also minimizes the unnecessary works that lead to delays that may caused by site
weather, erection of formwork and pouring of cast in situ concrete for the particular
structure frame. During the construction stage, once the prefabricated components are
installed at the required structure, it provides a sturdy and safe working platform for
carrying out other site works. The duration taken to complete the installation of precast
concrete superstructure per floor is much faster compared to the conventional method.

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2.4.8.3. LABOUR SAVINGS:
Most of the precast products are manufactured by a highly technology machine for a
long production line with minimum usage of labour. The required man power on site
is less which few site workers are required during installation of prefabricated panels
and others building works. Hence, it creates safer and neater sites due to reduction of
site workers.
2.4.8.4. HIGH QUALITY PRODUCT:
Basically the ranges of precast concrete products are manufactured in a controlled
factory which used high technology that complies with international and local
standards. The technology is controlled by the professional and experienced team
(designers and manufacturers) in order to produce high quality finished products as well
as to fulfil clients’ satisfaction. Most of the local manufactures of prefabrication
products has good construction practice with a high commitment in producing best
quality products and services towards achieving MS ISO 9001:2000 Quality
Management System through quality assurance and quality control. Most of precast
members used as part of the building structure must conform to all applicable design
and detailing according to BS 8110 Part 1: Section Five. On the other hand, the precast
work on site must be constructed according to the method statement to achieve the
accuracy and the quality of work as well as to meet the design requirement. This shows
the quality control plan need to be adopted during precast work. In practice, few forms
are used to implement the quality control of precast work on site. An example of these
forms is as follows:
i) Request of inspection and testing
ii) Checklist for precasting work in factory
iii) Checklist for the installation of precast beam
iv) Checklist for the installation of the hollow core slab and plank
v) Checklist for the installation of the precast column

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2.4.8.5. COST ECONOMICAL AND EFFECTIVE:
The productions of prefabricated products are minimizing total construction cost.
With mass production which lead to faster construction time as well as savings in
material and financing costs.
As the process of construction speed up the construction loan periods are shortened and
it lead to income generated for the clients as well as for the interim payment to the
contractors and manufacturers.
In fact the prefabricated components may contribute to low maintenance cost. The
costing for personnel or labour are reduced comparing to the conventional method
where the panels are installed with the use of cranes machine and 2 experiences workers
for installation work. With the reduced slab weight the structure frame can made lighter
and reduced combined weight of frame and flooring system leads to lighter foundation
without compromise to quality and safety aspect.
2.4.8.6. SPACE EFFECTIVENESS
Basically the precast components are transported from factory and installed to the
required location. The panels reached on site are stack neatly and put temporary at a
side adjacent to the working area. On- site storage is unnecessary. The precast concrete
are unload from the truck to the structures at the same time is much ideal for the
constraint project site which usually in urban area. In spite of the reduced weight of
precast slabs, the handling costs are minimized and lifting of these components is easy
especially in congested site area.
2.4.8.7. ENHANCE BUILDABILITY
Build ability as the ability to construct a building efficiently, economically and agreed
quality levels from its materials, components and subassemblies. Hence, the project
team must ensure the continuity of activities by managing manpower, materials,
components and sub-assemblies are delivered to site, stored and installed according to
the building works.

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2.4.8.8. PROVIDE VOID FOR SERVICES
The services such as electrical wiring, mechanical work and internal/external plumbing
and sewerage can be easily installed neatly by using void at hollow core. Well prepared
planning and supervision, these services can be installed through voids without
providing conduits. Hence, it is considered cost savings.
2.4.8.9. SOUND INSULATION
The precast concrete is resistant to airborne noise and transmission of impact noise. It
provide sound insulation superior to solid concrete slabs of the same mass.
2.4.8.10. HEAT INSULATION
The existence voids provides good heat insulation compared to solid slabs. It is believe
that it has better thermal insulation properties in cold or heat which contribute to cost
savings for heating and air - conditioning.
2.4.8.11. FLEXIBILITY
As an example, the hollow core slabs are designed to carry brick wall. It means that
flexibility for any renovation can be done where it involves the use secondary beams.
2.4.9. DISADVANTAGES OF PRECAST CONCRETE SYSTEM
Even though there are many benefits in the precast concrete system as describe above,
there are some disadvantages also in system. They are as follows.

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2.4.9.1. IMPOSSIBLE DESIGN CHANGES
Freedom of changing after the design stage is less possible in the precast concrete
prefabrication system. If any changes required by user, it is very difficult to adjust an
existing system design to suit with specific needs of particular user. The design and
planning has to be firm at an earlier date than is the case with an in-situ structure. Last
minute changes cannot be accommodated once the precast members are cast and such
items architecturally fixing and holes for services must be known in time to be
incorporated in the detail of the members.
2.4.9.2. OTHER DISADVANTAGES
 A required for large capital investment that makes the contractor very
susceptible to fluctuation in demand for building
 The joint between members generate the problem to the Engineer. Skill
knowledge shall be required for the jointing and fixing of units
 If a large number of units are required or if they large in size problem can be
arise for storage, transportation and erection costs.
 Pestering is not suitable for irregular shaped buildings
 There is a restriction on the size and weight of precast concrete units. In other
words it is significant that more plants and machineries are required for the
handling of precast items
 Consumption of space for precast components with comparing steel structures
are large. Due to the heavy weight of the components, the structure has to
support the self loads and a result the components will be bulk rather than the
steel items.

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2.5. PREFABRICATION APPLICATION IN BUILDING
ELEMENTS
In a building the foundation, walls, doors and windows, floor and roof are the most
important components.
2.5.1. FOUNDATIONS
According to the Adlakha & Puri (2003), for foundation, conventional methods using
in-situ techniques are found to be economical and more practical for low cost housing.
In seismic regions, special attention is required to make the foundations continuous
using horizontal reinforcement. Prefabrication is not recommended for foundation in
normal situation.
2.5.2. WALLS
In the construction of walls, rammed earth, normal bricks, soil cement blocks, hollow
clay blocks, dense concrete blocks, small, medium and room size panels etc of different
sizes are used. However, bricks continue to be the backbone of the building industry. In
actual construction, the number of the bricks or blocks that are broken into different
sizes to fit into position at site is very large. As a result of this, there is wastage of
material and the quality of construction also suffers. Increasing the size of wall blocks
will prove economical due to greater speed and less mortar consumption, which can be
achieved by producing low density bigger size wall blocks and advantages of industrial
wastes like blast furnace slag and fly ash can be made.
2.5.3. FLOOR AND ROOF
Structural floors/roofs account for substantial cost of a building in normal situation.
Therefore, any savings achieved in floor/ roof considerably reduces the cost of
buildings. Traditional cast-in-situ concrete roof involve the use of temporary shuttering
which adds to the cost of construction and time. Use of standardised and optimised
roofing components where shuttering is avoided prove to be economical, fast and better
in quality (Adlakha & Puri, 2003).

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In a concrete frame building, floor construction is the most time consuming and costly
element of the superstructure cost. Therefore the selection of the floor construction
method is very important when compare to the other element of the building. Compared
with steel or timber, concrete floor systems are the more appropriate and popular choice
for concrete frame buildings.
2.6. SLAB SYSTEM IN HOUSING CONSTRUCTION
The slab system in building construction can be classified in to three categories namely
inset, prefabricated, Hybrid construction. In Sri Lanka the application of the
conventional in-situ concrete slab system in building construction is higher than the
prefabricated system. It is used as a conventional method of construction. There some
prefabricated slab systems are adapted in housing construction in Sri Lanka. The slab
system called SBS pre-stressed concrete floor system is becoming popular in housing
construction.
2.6.1. CONVENTIONAL SLAB SYSTEM
A In-situ Concrete slab is a common structural element in buildings. In Sri Lanka and
most of the countries it is used as a conventional slab system. Horizontal slabs of steel
reinforced concrete, typically between 100 and 500 millimeters thick, are most often
used to construct floors and ceilings, while thinner slabs are also used for exterior
paving. Normally in housing projects the In-situ slab thickness is 150 millimeters. In-
situ concrete slabs are built on the building site using formwork a type of boxing into
which the wet concrete is poured. If the slab is to be reinforced, the rebars are
positioned within the formwork before the concrete is poured in.
Formwork, reinforcement, and Concrete are the three primary expenses in cast-in-place
concrete slab construction to consider throughout the design process.
Formwork is the term given to either temporary or permanent molds into which
concrete or similar materials are poured. In the context of concrete construction, the
false work supports the shuttering moulds. Traditional timber formwork is built on site
out of timber and plywood or moisture resistant particleboard. It is easy to produce but
time consuming for larger structures and the plywood facing has a relatively short

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lifespan. It is still used extensively where the labor costs are lower than the costs for
procuring re-usable formwork. It is also the most flexible type of formwork, so even
where other systems are in use, complicated sections may use it.
Reinforcement can be used to increase the strength of concrete and to help control
cracking. Reinforcing bars are needed to resist the bending tension in the bottom over
the central portion of the span. Fewer bars are necessary on the bottom near the ends of
the span where the bending moment is small. For this reason, some bars may be bent so
that the inclined portion can be used to resist diagonal tension. The reinforcement must
be covered by a set amount of concrete which protects the steel from rusting. This is
called cover. The amount of cover depends on whether it is inside or outside and is
measured to the top or bottom of the outer surface. It is around 20-30 mm for slab.
Concrete is made by mixing cement, water, coarse and fine aggregates and admixtures
(if required). Aggregates are of two basic types. Those are coarse (crushed rock, gravel
or screenings.) and fine sands. Admixtures are mixed into the concrete to change or alter
its properties, is the time concrete takes to set and harden, or its workability.
After Concrete mixing amount of concrete should be transporting, placing, compacting
and finishing. Compaction is done by shaking or vibrating, the concrete which liquefies
it, allowing the trapped air to rise out. The concrete settles, filling all the space in the
forms. Curing means to cover the concrete so it stays moist. By keeping concrete moist
the bond between the paste and the aggregates gets stronger. Concrete doesn’t harden
properly if it is left to dry out. Concrete will take 28 days to harden properly, until that
the props can not be removed from the site and can not continue the construction on the
slab.
Form work and positioning the reinforcement work take more time in this conventional
slab system. Also Labour and machinery involvement is high in this method compare to
the prefabricated method.

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2.6.2. SBS SLAB SYSTEM
One of the precast manufacturing and C1 grade construction company in Sri Lanka
namely International Construction Consortium Ltd (ICC) has designed a novel concrete
system, which allows to reduce time of a construction by almost half. (Factory profile-
ICC publication, 2003).
The SBS pre-stressed concrete floor system also helps to save over 30 percent the
concrete slab installation charges. ‘The system is easy and does not require skilled
labourers for installation’. Senior Project Manager ICC, Palitha Ranasinghe said.
The industry faces a problem when building several storied buildings as the masons
cannot construct an upper floor until the concrete slab laid gets hardened. This takes
around 20 to 30 days and stilts too are needed which makes work on the lower floors
impossible.
To overcome this problem, ICC has designed the SBS system which is now very
popular. No frame work is necessary for the slab and the soffit blocks once in place
offers an immediate working platform for further construction. Rapid method of
construction due to the use of precast elements and the non-use of frame work is a great
advantage under this system.
The SBS pressurised slab system is made up of four components, consisting of
 Pressurised beam- Grade 40/10 concrete.
 Concrete masonry soffit block of grade 10/10 concrete
 Distribution reinforcement GI weld mesh 3mm (dia) 50 X 50 (sqrs)
 Structural concreting topping grade 20/10 concrete
The sequence of installation of SBS slab in a housing construction is explained with
photograph in Annex -4

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2.7. KIT FORM HOUSE
One of the famous precast manufacturing company called International Construction
Consortium (ICC) has introduced a special housing unit, (KIT), designed and precasted
by them and comes down in knock down form. This can be easily assembled by four
workers in four days.
The lay-out of this KIT house can be designed and constructed according to the needs of
the end user. The owners can decide the material for wall cladding and finishing and the
company A would also supply an instruction manual and a tool kit. Kit form houses are
widely constructed everywhere in Sri Lanka. It is quietly enough for a family for their
living purpose. If the numbers of members are high in a family, there is a possibility to
merge the kit unit with another.
One unit of kit form housing is for a house with a plinth area of 40.69 m2. The house
could be developing to consist of living and dining room, bed room, a kitchen, a
varandah and a toilet. The Figure 2.5 shows the plan of Kit form house.
Figure 2-5: Plan of Kit form house

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A kit form housing units consists of Column pocket footing, Pad footings, Columns,
Plinth beams, Tie beams, Toilet pedestal, Roof beams, Purlins, and lintels. The table 2.2
shows the detail about the each elements in a kit form house.
Table 2-2: Elements in a typical kit house
Elements Material Numbers
Column
pocket footing
Precast concrete
9
Pad footings Precast concrete 4
Columns Pre-stressed
concrete
9
Plinth beams Pre-stressed
concrete
12
Tie beams Pre-stressed
concrete
6
Toilet pedestal Precast 1
Roof beams Pre-stressed
concrete
6
Purlins Timber 16
Lintels Pre-stressed
concrete
9
2.7.1. ERECTION OF A KIT FORM HOUSE
Now days Kit form houses becoming very popular in Sri Lanka due to reduce the
construction duration and to reduce the cost of the building. A kit form house can be
easily assembled by four workers in four days. The method of the erection of a typical
kit form house is explained with photograph in Annex -5
2.7.2. BENEFITS OF THE KIT HOUSES
 The elements for the Kit are manufactured under TQM condition in the precast
factory. So the quality of the Kit house is high
 The components which come in knock down form could be easily assembled at
ground level and erected by four workers in 4-5 days. The time taken to build
the same area of house in conventional method is very high Compare with this

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method. So that by reducing the total duration of the construction and reducing
the labour involvement there is the huge amount of cost saving in this type of
Kit houses.
 An erection manual with tools and implements required for erection is provided
and included in the kit.
 The internal layout of the houses could be designed and constructed according to
the needs of the end user
 The material for wall cladding and the type of finishes could be decided by the
house owners themselves based on their requirements and their budgets.
2.8. SUMMARY
In Sri Lanka the demand for houses and urban infrastructure is expanding rapidly with
the population growth and urbanisation. In addition most of the people who lived in
costrel area lost their shelters. This also increased the demand for houses. So there was a
need to build those houses in very short period. To achieve this target, using
prefabricated technology is better alternative for the conventional method. Numerous
constructions in the world have utilized prefabrication of precast concrete system
especially when the project requirement is to build in shorter period of within the given
budget and quality workmanship
Prefabrication is the practice of manufacturing the components of an assembly in one
location and assembling them in another. By using a prefabricated building system, as
much as 50% of the total construction time can be cut out of the schedule (Mark 1993).
There are mainly two types of prefabricated system adopted in building construction
namely, fully prefabricated systems and partially prefabricated systems. In Sri Lanka
Steel, timber and precast concrete are the material widely used in the prefabricated
construction. Precast concretes unites are very commonly used in the prefabricated
housing construction in Sri Lank due to the several reasons such as easy availability of
material, economical, quality, etc..

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CCHHAAPPTTEERR 0033
33..00 RREESSEEAARRCCHH MMEETTHHOODDOOLLOOGGYY
3.1. INTRODUCTION
The research objectives of this project report uses two methods: literature method and
empirical study. Firstly, the preliminary study is done to gather information about
research topic and recently technology applied in our construction building industry.
Informal interviews with professionals and experienced personnel in the usage of the
precast concrete in prefabricated system were carried out in designing questionnaire
form. Questionnaire survey forms are distributed to gauge respondents’ opinion
regarding the benefits in using prefabrication in the housing construction. The findings
of the study were discussed and few suggestions are listed. Finally, the study research is
concluded.
3.2. LITERATURE REVIEW
A literature review was carried out as preliminary study in gaining knowledge of the
research topic. Through the literature review, research mapping was established. The
literature review was drawn by referring to several sources such from published books,
articles in journals and papers, other published research works, academic and research
magazines and newsletter, brochures and information from the internet
3.3. INFORMAL INTERVIEWS
An informal interview with experienced personnel from the construction industry with
regards to the usage of precast prefabricated system in housing construction were
carried out. These interviews were conducted to obtain ideas and data valuable for
structuring the questionnaire survey form.
3.4. QUESTIONNAIRE SURVEY
A questionnaire survey forms were distributed to the developers, architects,
engineers, manufacturers, quantity surveyors, government agencies, contractors and
consulting firms in eastern province. Some sets of questionnaire survey forms
were distributed to get the necessary details.

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3.5. FIELD SURVEY
Simple field survey was conducted to ascertain the cost effectiveness of the
prefabricated floor system against conventional slab system in housing construction.
The cost detail of five number of two story housing projects, which are constructed by
using conventional in-situ concrete slab system, were selected within the addalaichennai
housing plan. As well as the cost detail of another five number of two story housing
projects were selected, which are constructed by using SBS slab system, while other
parameters are constrain.
Average cost of both slab system per square meter were calculated by using simple
average equation. The cost saving of the SBS slab system was calculated by comparing
the average unit cost of both Insitu and SBS slab system. The calculation part is
attached in the Annex 3.
3.6. QUESTIONNAIRE STRUCTURE
The questionnaire was structured into three sections:
 Section A: Obtain information about the respondent’s profession and role in the
construction building industry and the organization in which he or she served.
 Section B: Obtain information about the respondent’s working experience or
knowledge on the application of prefabrication system in the
projects involved by his or hers organization business area.
 Section C: Evaluate the benefits of using precast concrete technology in
construction industry. And comments regarding the application of this
system in improving our construction industry.
Questions in Section C are based on Likert scale of five ordinal measures of agreement
towards each statements (from 1 to 5) as shown in the below Figure 3.1

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Figure 3-1: Five ordinal measure of agreement of Likert scale
The data collected from the questionnaire survey was analysed using frequency analysis
and “Relative Indices” (RI) technique. RI was calculated using the following formula:
RI = ∑ (1n1 + 2n2 + 3n3 + 4n4 + 5n5)
5 (n1 + n2 + n3 + n4 + n5)
Where: ni = the number of respondent agreeing with each choice
The computation of RI using this formulae yield the value of RI ranging from
0.2 to 1.0, where 0.2 represent minimum strength and 1.0 the maximum strength. The
table below shows the categories for RI ranges.
Table 3-1: Categories for RI ranges
RI Range Category
0.20 - 0.35 Very Low
0.36 - 0.51 Low
0.52 - 0.67 Average
0.68 - 0.83 High
0.84 - 1.00 Very High
(Source: Rahim 2004)

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3.7. LIMITATION OF THE STUDY
This study is limited to literature review and evaluation from personnel involved in the
construction industry. The study considered only on the use precast concrete element in
housing construction. The data collected are only confined to the respondents within the
eastern area. The identification of the cost saving of prefabricated system is done only
housing projects.
The research methodology flowchart was shown in below Figure 4.2 which indicates
the general procedures for this study

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Literature Review
Establish framework of
the research
Data collection
Data Analysis
Discussion
Conclusion

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CONCLUSION.
This Individual Project would have given me a good
knowledge about prefabricated building and these constructions. I got
much information from all the sources possible. This assignment would
have helped us to come to know the methods used in the industry and
construction site. In today many buildings were built in this format. Its
method very easy way to the building.

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REFERENCES & BIBLIOGRAPHY
1. Adlakha, PK & Puri, HC 2003, ‘Prefabrication building methodologies for low
cost housing’, IE Journal, vol. 84, pp. 4-9.
2. Al-Rashid, K, Kartam, N, & Koushiki, PA 2005, ‘Delays and cost increases in the
construction of private residential project in Kuwait’, Construction management
and economics, vol. 23, pp. 285-294.
3. Brook, KM, & Murdock, LJ 1979, Concrete material and practice, Edward Arnold
(Publishers) Ltd, London.
4. Bruggeling, ASG & Huyghe, GF 1991, Prefabrication with concrete,
A.A.Balkema Rotterdam, Netherlands.
5. Central Bank of Sri Lanka 2005, Central Bank Report 2004, Colombo.
6. Central Bank of Sri Lanka 2007, Central Bank Report 2006, Colombo.
7. Chan, APC & Tam, CM 2000, ‘Factors affecting the quality of building projects
in Hong Kong’, International Journal of Quality & Reliability Management, vol.
17, no. 4/5, pp. 423-441.
8. Chan, APC, Chan, DWM & Yeung, NSY 2002, ‘Application of prefabrication in
construction - A new research agenda for reform by CII-HK’, Conference on
precast concrete building system, Hong Kong.
9. Chan, APC, Lam, PTI & Wong, FKW 2006, ‘Assessing quality relationships in
public housing: An empirical study’, International Journal of Quality & Reliability
Management, vol. 23, no. 8, pp. 909-927.
10. Chew, SP 1986, ‘The scenario of industrial building system in Malaysia’,
Proceeding of the 1986 UNESCO/FEISAP regional workshop on “Towards

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Industrialization In the Building Industry, July 29-31, Malaysia: UPM, Serdang,
pp. 126-128.
11. Chudley, R 1989, Building superstructure, Longman Group UK Limited, London.
12. Chudley, R 1999, Construction Technology, 3rd edn, Addition Wesley logman
Limited, London.
13. Domel, AW & Ghosh, SK, 1990, Concrete Floor Systems:Guide To Estimating
and Economizing, Portland Cement Association, Tokyo.
14. Egan, J 1998, Re-thinking construction, DETR. London.
15. Elliott, KS 2000, ‘Research and development in precast concrete framed
structures’, Prog. Struct. Engng .Mater, vol. 2, pp. 405-428.
16. Foster, JS 1997, Structure and Fabric part 1, Willianm Colwes & Sons Ltd,
London.
17. Glass, J 1999, The future for pre cast concrete in low rise housing, British precast
concrete federation, London.
18. Glass, J 2005, ‘A best practices process model for hybrid concrete construction’,
Construction management and economics, vol. 23, pp. 169-184.
19. Goodchild, CH 1997, Economic Concrete Frame Elements, British Cement
Association, Crowthorne.