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Low cost mass housing using precast RCC
National Institute of Technology, Warangal 1
CHAPTER 1
INTRODUCTION
1.1 GENERAL
Housing need is one of the most elementary human needs. The need of the
houses for the refugee of the tsunami disaster in Aceh in five year ahead reached up to 78,000
units. Not to mention the earthquake that occurred Yogyakarta and Central Java that demolished
and devastated 5,69,825 houses.
Apart from that, other various kind of disaster that recently attacked Indonesia has
increase the amount of housing needs that is necessary as the action of emergency response.
In additional to emerge of the needs of housing as the effect of natural disaster,
the increase needs of housing also emerge as the increase of population and urbanization.
Affordability is the main requirement of house provisions for low income society to achieve. On
keeping the price of the house down, there is a tendency of the builders to curtail the building
quality, so that a large scale squandering happened.
1.2 LOW COST HOUSING
Low Cost Housing is a new concept which deals with effective budgeting
and following of techniques which help in reducing the cost of construction through the use of
steel wire mesh along with improved skills and technology without sacrificing the strength,
performance and life of the structure. There is huge misconception that low cost housing is
suitable for only sub- standard works and they are constructed by utilizing cheap building
materials of low quality. The fact is that Low cost housing is done by proper management of
resources. Economy is also achieved by postponing finishing works or implementing them in
phases.
The building construction cost can be divided into two parts namely:
Building material cost: 65 to 70 %
Labor cost: 65 to 70 %
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National Institute of Technology, Warangal 2
Now in low cost housing, building material cost is less because we make use of the locally
available materials and also the labor cost can be reduced by properly making the time schedule
of our work. Cost of reduction is achieved by selection of more efficient material or by an
improved design.
1.2.1 Areas from where cost can be reduced are:-
1) Reduce plinth area by using thinner wall concept.Ex.15 cm thick solid concrete block wall.
2) Use locally available material in an innovative form like soil cement blocks in place of burnt
brick.
3) Use an energy efficiency material which consumes less energy like concrete block in place of
burnt brick.
4) Use environmentally friendly materials which are substitute for conventional building
components like use R.C.C. Door and window frames in place of wooden frames.
5) Preplan every component of a house and rationalize the design procedure for reducing the
size of the component in the building.
6) By planning each and every component of a house the wastage of materials due to demolition
of the unplanned component of the house can be avoided.
7) Each component of the house shall be checked for necessity.
Since concrete is a brittle material and is strong in compression. It is weak in
tension, so steel is used inside concrete for strengthening and reinforcing the tensile strength of
concrete. The steel must have appropriate deformations to provide strong bonds and
interlocking of both materials. When completely surrounded by the hardened concrete mass it
forms an integral part of the two materials, known as "Reinforced Concrete".
In this technique, we are using precast reinforced cement concrete wall panels of
size 1m x 0.5m x .08m in place of conventional brick masonry. All these reinforced cement
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National Institute of Technology, Warangal 3
concrete wall panels are pre-casted units. Each element in this technique is capable of
transferring loads. Frames for Doors & Windows, sunshades, provisions of drainage facility and
other mandatory provisions have to be installed at the time of casting.
1.2.2 Prefabrication as applied to `Low Cost Housing (P.K.Adlakha and H.C.Puri, 2002)17:
Advantages of prefabrication are:
1. In prefabricated construction, as the components are readymade, self supporting,
shuttering and scaffolding is eliminated with a saving in shuttering cost.
2. In conventional methods, the shuttering gets damaged due to its repetitive use because of
frequent cutting, nailing etc. On the other hand, the mould for the precast components
can be used for large number of repetitions thereby reducing the cost of the mould per
unit.
3. In prefabricated housing system, time is saved by the use of precast elements which are
casted off-site during the course of foundations being laid. 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. Thus, saving of
time attributes to saving of money.
4. In precast construction, similar types of components are produced repeatedly, resulting
in increased productivity and economy in cost too.
5. Since there is repeated production of similar types of components in precast
construction, therefore, it results in faster execution, more productivity and economy.
6. In prefabricated construction, the work at site is reduced to minimum, thereby,
enhancing the quality of work, reliability and cleanliness.
7. The execution is much faster than the conventional methods, thereby, reducing the time
period of construction which can be beneficial in early returns of the investment.
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National Institute of Technology, Warangal 4
1.3 AIM:
The research of ‘Low Cost Mass Housing Using precast Reinforced cement
concrete wall panels and slabs’ is aiming to give an inexpensive alternative building system by
using simple technology. The main objective of this project is to find out:-
1. To establish Construction sequence or methodology
2. To identify Element shape & dimensions
3. To examine Estimated time of completion, Cost and Bill of quantities
4. A comparative study with Conventional framed structure and Ferro cement
1.4 SCOPE:
The objective of this research focuses to give an alternative house construction
technology, which exploiting the use of precast reinforced cement concrete wall panels and
slabs. Basically, this research is an explorative research in design and implementation on the
building material, prefabricated building components, casting equipment and method, and
assembling process. There are a number of significant benefits of using this technology as
compared to most traditional construction approaches, the major being:
Speed of construction
can reduce the dead weight of the structure by half
More strength & better quality than conventional brick masonry
Low cost
Durability, versatility and ease of deployment
Low Level of Skilled Staff - construction system is extremely simple to use and requires
very few highly skilled staff on site. This has important benefits in areas where in which
there are skills shortages.
Plastering can be avoided
Less construction time period
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National Institute of Technology, Warangal 5
CHAPTER 2
LITERATURE REVIEW
The illustration in the literature review covers the entire construction industry. It is then
narrowed down to the types and resources of construction from global and local studies in the
past. Subsequently the review is focus to the results and recommendations in applying and
implementing project management methods in small and big scale projects.
2.1 The Elements of Project Management
The project management elements consist of planning, scheduling and controlling (Keizer &
Render, 2008)9. The review of literature finding are discussed in the following sub-sections
2.1.1 Project Planning
Project planning is the first element in project management. It is initiated in the early stage of
the construction. The planning, organizing, directing and controlling of project activities are
part of project planning. It is the basis of project management while contractors or home-
builders are required to comply with the client’s needs and wants Keizer, 20069; Barley &
Saylor, 2001)2. Generally, small project is defined by the length of time it can be completed, i.e.
within six (6) months (Rowe, 2000)13. Meanwhile, the construction of each bungalow house
normally takes between 6-12 months to complete. There are several indicators of unplanned
projects activities (Zamini & Bachan, 2008)19. Two common indicators are project delay and
financial loss (Badron, 20053; Alan, 2007)2.
2.1.2 Project Scheduling
Project scheduling is another important element in project management. Projects with proper
scheduled activities can produce better quality work, cost saving and faster construction periods
(Keizer & Render, 2008)9. Indeed, project scheduling is vital to project execution success and in
accomplishing the objectives and goals of a project (Graham, 2006)6. What is equally important
is that the contractors adhere to the schedule of projects so that it does not breach the obligation
and responsibility of completing the construction of house according to the stipulated time (Al-
Kharashe & Skitmore, 2009)14. The failure to employ proper project scheduling might result in
high risk of project being delayed, interruption in project completion and project financial lost
(Badron, 20054; Alan, 20072).
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National Institute of Technology, Warangal 6
2.1.3 Project Controlling
Another important element of project management is project control. Its function is to
coordinate resources, people, money, equipment, machinery and time into a designated time
frame to accomplish project objectives and obtain satisfying performance and results (Keizer,
20069; Tan, 2005; Pinto & Trailer12). The area of control in project management are objective
control, design control, budgeting and cost control, authority and approving control as well as
financing control and to control costs (Tan, 2005). In Malaysia, the controlling activities of
construction and providing its guideline are facilitated through the Construction Industrial
Development Board (CIDB). Thus, in short the basic rule of management is that no project is
likely to be successful unless objectives are properly defined and adequate allocations are being
made for the necessary labor and materials.
Project cost is equally important as project control regardless of the size of the project (Keizer,
2006)9. The success of the project is determined by the effective implementation of the
management of the project cost (Pinto & Trailer, 1999)12. Hence managing cost with the scope
of time would provide good project outcome (Melton, 2008). Otherwise, the consequence of not
applying project costing during the construction process would be reflected by improper
material control thus causing excessive wastage of resources (Poon Yu & Jai Bon, 2004).
2.1.4 Resources of Construction
The method of project management in residential constructions in Malaysia still remains
backward primarily in terms of the methods used (Kader et al. (2004). This was supported by
Tan’s (2005) argument that in Malaysia, builders are in general slow to respond to the changing
needs of the building industry. Home builders, particularly in small constructions are too
sluggish in their approach to new methods and techniques. These factors result in poor
workmanship, low standards, longer project durations, completion delays, massive cost
overruns, industrial related incidents and building failures (Tan, 2005). What that has been
described by Tan (2005) is the reality of home builders not only in the area of this study, but
also in the whole nation. The application of management methods in residential construction
acts as an adjustment (Wong, 1997) to the building industry. If project management methods
were to be employed, a lot of improvements can thus be achieved. The successful factors in
managing housing construction industry are linked to the economic environment, project
manager experience and qualification as well as commitment of the project team (Inna Didenko
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National Institute of Technology, Warangal 7
& Ivan Kohrt, 2009). The residential construction productivity is still low due to the incapability
of the contractor to organize activities (Kader et al., 2006). To put it more succinctly,
contractors (home builders) of single-family housing or bungalow are still lacking in their
ability to adopt project management methods in the implementation of the project.
2.2 A Brief History of Levittown, New York
Abraham Levitt was a real estate lawyer by trade, but also dabbled in real estate investment,
purchasing land and selling it off to developers in the late 1920s. When the onset of the
1930's Great Depression caused the developer of a Rockville Centre property to default on
his payments, the senior Levitt was forced to complete the development himself to protect
his investment. Having no previous experience with construction, he called on his two sons,
in college at the time, for help. Together, Levitt & Sons labored to learn everything there
was to know about construction techniques, and together, they completed the project.
Strathmore, as the upscale Rockville Centre development was named, was such a success that
Levitt and Sons continued to purchase land and build new homes throughout the Depression.
With each new development, their construction methods became more and more efficient.
When the U.S. entered WWII in 1941, Levitt and Sons won a Navy contract to build homes
for shipyard workers in Norfolk, Virginia. Here, they developed and perfected the mass
production techniques they later used in the construction of Levittown, New York.
2.3 Concept of prefabrication
Concept of prefabrication / partial prefabrication has been adopted for speedier construction,
better quality components & saving in material quantities & costs. Some of these construction
techniques & Materials for walls, roof & floor slab, doors & windows are as follows:
2.3.1 In Walls: - Several prefabrication techniques have been developed and executed for walls
but these medium and large panel techniques have not proved economical for low rise buildings
as compared to traditional brick work. (P.K.Adlakha and H.C.Puri, 2002)16
i. Non erodable mud plaster:
The plaster over mud walls gets eroded during rains, which necessitates costly
annual repairs. This can be made non erodable by the use of bitumen cutback emulsion
containing mixture of hot bitumen and kerosene oil. The mixture is plugged along with mud
mortar and wheat/ rice straw. This mortar is applied on mud wall surface in thickness of 12 mm.
Low cost mass housing using precast RCC
National Institute of Technology, Warangal 8
One or two coats of mud cow dung slurry with cutback are applied after the plaster is dry. The
maintenance cost is low due to enhanced durability of mud walls.(R.K.Garg, 2008)
ii. Fly –Ash sand lime bricks:
By mixing of lime and fly ash in the presence of moisture, fly ash sand lime
bricks are made. Fly Ash reacts with lime at ordinary temperature and forms a compound
possessing cementitious properties. After reactions between lime and fly ash, calcium silicate
hydrates are produced which are responsible for the high strength of the compound. Bricks
made by mixing lime and fly ash are therefore, chemically bonded bricks. (R.K.Garg, 2008)
iii. Solid concrete and stone blocks:
This technique is suitable in areas where stones and aggregates for the blocks are
available locally at cheaper rates. Innovative techniques of solid blocks with both lean concrete
and stones have been developed for walls. The gang-mould is developed for semi-mechanized
faster production of the blocks. (R.K.Garg, 2008)
2.3.2 In Floor and Roof:- Structural floors/roofs account for substantial cost of a building in
normal situation. Therefore, any savings achieved in floor/roof considerably reduce the cost of
building. Traditional Cast-in-situ concrete roof involve the use of temporary Shuttering which
adds to the cost of construction and time. Use of standardized and optimized roofing
components where shuttering is avoided prove to be economical, fast and better in quality.
Some of the prefabricated roofing/flooring components found suitable in many low cost housing
projects are:
i. Precast RC Planks.
ii. Prefabricated Brick Panels
iii. Precast RB Curved Panels.
iv. Precast RC Channel Roofing
v. Precast Hollow Slabs
vi. Precast Concrete Panels
vii. L Panel Roofing
viii. Trapezon Panel Roofing
ix. Un reinforced Pyramidal Brick Roof
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National Institute of Technology, Warangal 9
2.4 Case histories in India Demonstrations Construction Using Cost- Effective & Disaster
Resistant Technologies
BMTPC has been promoting cost-effective & environment- friendly building
materials & construction techniques in different regions of the country. During recent past the
council has been laying emphasis on putting up demonstration structures utilizing region
specific technologies. Details of the major projects handled by them are given as under:-
1. Demonstration Housing Project at Laggerre, Bangalore, Karnataka.
Project Profile:-
Name of scheme : VAMBAY – Ministry of HUPA
Location of site : Laggere, Bangalore
No. of Units : 252 (Ground +2)
Built-up area of a unit: 275sq.ft
Unit consist of : 2 rooms 1 kitchen,1 bath room, 1WC
Cost per unit : Rs.60000
Cost per Sqft : Rs.218/-
Nodal State Agency : Karnataka slum clearance Board
Technologies / Specification
Foundation
Random Rubble Stone Masonry
Walling
Solid Concrete blocks for 200mm thick walls
Clay Bricks for partition walls
RCC Plinth Band for Earthquake resistance
Roof/Floor
RC Filler slab using clay bricks as fillers in ground
RC slab for second floor
IPS flooring
Doors & Windows
Pre-cast RCC door frames
Coir polymer Door shutters
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National Institute of Technology, Warangal 10
Steel Sheet window shutters
Clay jalli in ventilators
Others
External Cement plaster
White wash on internal walls
Water proof cement paint on external walls
Precast Ferro cement lofts, shelves, chajjas.
2. Demonstration Housing Project at Dehradun, uttarakhand
Project Profile:-
Name of scheme : VAMBAY – Ministry of HUPA
Location of site : Dehradun Ram Kusth Ashram, Ryagi Road{28 Double Units(DUs)}
No. of Units : 100
Built-up area of a unit: 181sq.ft
Unit consist of : 1room,kitchenspace, 1 bath room, 1WC
Cost per unit : Rs.45000
Cost per Sqft : Rs.249/-
Nodal State Agency : District Urban Development Agency
Technologies / Specification
Foundation
Step footing in solid concrete blocks
Walling
Solid /Hollow concrete blocks
RCC plinth, lintel, roof level band, vertical reinforcement in corners for earth quake resistance
Roof/Floor
RCC planks & joist with screed
IPS flooring
Doors & Windows
Pre-cast RCC door frames
Wood substitute door shutters
Fly ash polymer door shutter for toilet.
Cement jalli in ventilators and windows
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National Institute of Technology, Warangal 11
2.5 Why RCC is used?
1. The wall thickness can be reduced up to 8 cm
2. The dead weight of the structure can be reduced by 50% Suppose for a 23 cm conventional masonry wall,
Mass density as per IS 456 = 1.8 T/m3
If Volume = 100 m3
Dead weight = 1.8 * 100 = 180 tons
But for a 8 cm thick RCC wall,
Mass density as per IS 456 = 2.5 T/m3
Volume = 100 * 1/3(for RCC wall, thickness reduce by one-third)
= 33.33 m3
Dead weight = 33.33 * 2.5 = 83.33 tons
This light weight property will give the following savings :
- Size of foundation and other concrete elements of the building , if any, will be
reduced.
- Foundation depth, excavation and backfill will be reduced.
- Number of trailers required to transport precast panels is much less.
- Erection work can be carried out without the use of heavy equipment. 3. The floor area space can be increased.
Saves huge amount of space by reducing the wall thickness up to 8 cm.
Provide significant social and environmental benefits to the residents.
Enables architects more freedom to design more livable and open spaces through
design flexibility.
4. The overall cost can be reduced by 50% for Structure Alone Suppose for a 100 m3 of 23 cm thick masonry wall,
Overall cost comes around 7000 Rs/m3
Total cost = 100 * 7000 = 7, 00,000 Rs
But for a 33.33 m3 of 8 cm thick RCC wall,
overall cost comes around 11000 Rs/m3
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National Institute of Technology, Warangal 12
Total cost = 33.33 * 11000 = 3, 66,630 Rs
5. The foundation plan area can be reduced by 50% Generally SBC of a black cotton soil = 5 T/m3
Dead weight for 100 m3 of 23 cm thick masonry wall = 180 tons (calculated above)
Therefore, Area = load / SBC = 180/5 = 36 m2
But dead weight for 33.33 m3 of 8 cm RCC concrete precast unit is 83.325 tons
Therefore, Area = load/ SBC = 80/5 = 16 m2
6. Plastering can be avoided- shutter finished products
7. Better quality than conventional brick masonry & Ferro cement
8. More strength
9. Less construction time period- time is saved by the use of precast elements which are
casted off-site during the course of foundations or during other activities being laid. The
execution is much faster than the conventional methods, thereby, reducing the time
period of construction which can be beneficial in early returns of the investment.
10. More economical than Ferro cement: - The problem with Ferro cement construction is the labor intensive nature of it–, which
makes it expensive for industrial application in the western world. In addition, threats to
degradation (rust) of the steel components is a possibility if air voids are left in the
original construction, due to too dry a mixture of the concrete being applied, or not
forcing the air out of the structure while it is in its wet stage of construction, through
vibration, pressurized spraying techniques, or other means. These air voids can turn to
pools of water as the cured material absorbs moisture. If the voids occur where there is
untreated steel, the steel will rust and expand, causing the system to fail.
11. Shuttering can be avoided
As the components are readymade, self supporting, shuttering and scaffolding is
eliminated with a saving in shuttering cost.
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National Institute of Technology, Warangal 13
CHAPTER 3
PRE-CAST RCC THINNER WALL HOUSE
The objective of this research is to give an alternative house construction technology, which
exploiting the use of precast reinforced cement concrete wall panels and slabs. Basically, this
research is an explorative research in design and implementation on the building material,
prefabricated building components, casting equipment and method, and assembling process.
This system consists of various product types: wall panels, floor/roof slabs and lintels, which
can be combined to form a load bearing structure. By using this system costly labor and
material intensive in situ concrete structures of columns, beams, floor and roof slabs can be
eliminated.
This alternative technique is useful only for mass housing for example: construction of a colony
having 50 – 100 houses having same plan or an emergency rehabilitation center which need to
be completed within stipulated time period.
From the four objectives mentioned earlier, discussions regarding wall panels shape and sizes
are finalized.
There are five types of precast panels used for constructing a single unit in this alternative
technology. They are: -
I. Rectangular wall panel (1 x 0.5 x 0.08)
II. L- shaped panel (1 x 1 x 0.15)
III. T- shaped panel (2 x 1 x 0.15)
IV. Lintel beams (2 x 0.30 x 0.15)
V. Slabs (3.2 x 0.50 x 0.08)
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National Institute of Technology, Warangal 14
3.1 PLAN:
First of all, a simple drawing of a single storey house (refer Fig 3.1) with plan area 700 sq.ft is obtained, which consist of : -
1. 1 kitchen (3m x 3m) 2. 2 bed room (3.5m x 3m) 3. 1 bath room (2m x 2m) 4. Drawing hall (7m x 3) 5. Sit out (3.5 x 2m)
Fig.3.1: Plan of a single storey house 700 sq.ft
Fig 3.2: Plan of a single storey house 700 sq.ft arranged with precast panels
1 1
1
1
1 1 1
1 2 2
2
2
2
2
2
2
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National Institute of Technology, Warangal 15
Fig 3.3: 3-Dimentional view after arranging precast panels
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National Institute of Technology, Warangal 16
3.2 Wall panels shape and dimensions:
Precast concrete wall panels that act as load bearing elements in a building are both a
structurally efficient and economical means of transferring floor and roof loads through the
structure and into the foundation. In many cases, this integration can also simplify construction
and reduce costs. Architectural load carrying components can be provided in a variety of custom
designed or standard section shapes. In the interest of both economy and function, precast
panels should be as large as practical, while considering production efficiency and
transportation and erection limitations. By making panels as large as possible, numerous
economies are realized. Panels may be designed for use in either vertical or horizontal positions.
For low-rise buildings, by spanning load bearing panels vertically through several stories,
complex connection details can be minimized, and consequently the economic advantages of
load bearing wall panels are increased. For high-rise buildings, it is normally more practical to
work with single storey horizontal panels connected at each floor level. The elements can be
more slender, simplifying the erection.
Panels should be designed in specific widths to suit the buildings modular planning. When such
a building is designed properly, the economic advantages of load bearing wall panels are
significantly increased. Panel dimensions generally are governed by architectural requirements.
Most shapes, textures, and surface finishes commonly associated with cladding are possible,
provided structural integrity and other technical requirements can be satisfied at the same time.
In this technique, only 5 types of precast panels are used for each unit. Each type of precast
panels are discussed below:
3.2.1 Rectangular wall panels
Fig 3.4: Rectangular wall panel with size 1m x 0.5m x .08m
8 cm thickness
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National Institute of Technology, Warangal 17
Purpose: wall panel
Specifications: - Length L = 100cm, height = 50cm, thickness = 8cm
Bar diameter = 8mm ф@120 mm spacing square mesh
Number of panels used in a single unit: 75
Number of rectangular steel moulds used: 20
Rectangular wall panels are reinforced units, for load bearing applications as either external or
internal walls in a wide variety of low and medium rise buildings. Here rectangular wall panel
thickness is 8cm(refer Fig 3.4), due to this reduced thickness we can reduce the dead weight of
the structure by 50 %, we can increase the floor area space, we can reduce the overall cost by
50% approx for structure alone, can reduce the foundation plan area by 50%, more strength &
less construction time period, more economical & better quality than conventional brick
masonry.
Male (4.8cm x 2.3cm) and female sockets (5cm x 2.5cm) are provided (refer Fig 3.5) at ends
for connecting each panel properly without having any change in dimensions. That is, Wall
units are milled along their edges to standard profiles and may be chamfered or fluted on one or
both faces. Figure below shows the shape and size of the milling. They can also be used as non
load-bearing cladding for steel or concrete framed structures.
These male and female sockets are sealed using aluminium tower bolt of 100mm. Panels are
designed in such a way it can lay in either vertical or horizontal positions.
Fig 3.5: 3-D view of a rectangular panel
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National Institute of Technology, Warangal 18
3.2.2 L- shaped panels
Purpose: As a corner support for rectangular wall panels (as a column)
Specification: - Length L= 100cm (one leg), height= 300cm, thickness= 15cm
Number of panels used in a single unit: 8
Number of L-shaped steel moulds used: 3
Bar diameter = 8mm ф@75 mm spacing square mesh
L-shaped panels are placed in corners for load transfer from slabs. This type of panels serves as
a column in conventional framed structure. In this type of panels, concrete haunch (0.15m x
0.15m) is provided(refer Fig 3.6) at the bending portion in order to increase the moment of
inertia there by to decrease slenderness ratio.
Only female sockets (5cm x 2.5cm) are provided on L-shaped panel, such that male sockets of
each wall panels are attached firmly to the female sockets of L-shaped panel properly without
affecting its dimensions. These male and female sockets are sealed using aluminium tower bolt
of 150 mm.
Fig 3.6: L- shaped panel with size 3m x 1m x .15m
1m 1m
3m
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National Institute of Technology, Warangal 19
3.2.3 T- shaped panels
Purpose: As a corner support for rectangular wall panels at junctions (as a column)
Specification: - Length L= 100cm (one leg), height= 300cm, thickness= 15cm
Number of panels used in a single unit: 7
Number of T-shaped steel moulds used: 3
Bar diameter = 8mm ф@75 mm spacing square mesh
T-shaped panels are placed in corners for load transfer from slabs. This type of panels serves as
a column in conventional framed structure. In this type of panels, concrete haunch(0.15m x
0.15m) is provided (refer Fig 3.7) at the bending portion in order to increase the moment of
inertia there by to decreasing slenderness ratio.
Only female sockets (5cm x 2.5cm) are provided on T-shaped panel, such that male sockets of
each wall panels are attached firmly to the female sockets of T-shaped panel properly without
affecting its dimensions. These male and female sockets are sealed using aluminium tower bolt
of 150 mm.
Fig 3.7: T- shaped panel with size 3m x 2m x .15m 1m
2m
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National Institute of Technology, Warangal 20
3.2.4 Lintel beam
Purpose: To fix all rectangular wall panels in a straight line (as a continuous beam)
Specification: - Length L= 2.1m (depends upon the dimensions of the room), height= 30cm, thickness= 15cm
Number of panels used in a single unit: 15
Number of lintel steel moulds used: 4
Bar diameter = 2-12mm ф (top), 3-16mm ф (bottom), stirrups= 8mm ф@75mm c/c spacing
Lintel beam act as a continuous beam over
rectangular wall panels in order to fix all panels in a
straight line. Male (4.8cm x 2.3cm) and female sockets
(5cm x 2.5cm) are provided at ends for connecting each
wall panel properly without affecting its dimensions. Here
male sockets are located on sides(refer Fig 3.9), in order to
fix inside the female sockets of L-panels or T- panels while
female sockets of lintel beam are located on above and below.
Male and female sockets are sealed using aluminium tower bolt of 150 mm.
Fig 3.8: Lintel beam with size 2.1m x 0.3m x .15m
Fig 3.9: Male socket- 4.8cm x 2.3cm & female socket- 5cm x 2.5cm
2.1 m
0.30m
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National Institute of Technology, Warangal 21
3.2.5 Slabs
Purpose: roof covering
Specification: Length L= 3.2m, width= 50cm, thickness= 12cm
Number of panels used in a single unit: 46
Bar diameter: 8mm ф@75 mm spacing (1º), 8mm ф@ 120 mm spacing (2º)
A concrete slab is a common structural element of modern buildings. Here precast concrete slabs are arranged depending upon the room dimensions. Male (2.3cm x 4.8cm) and female sockets (5cm x 2.5) are provided (refer Fig 3.10)at ends for connecting each slab properly without affecting its dimensions
Fig 3.10: Slab with size 3.2m x .5m x .08m
Fig 3.11: Arrangements of 3.2 m precast slabs
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National Institute of Technology, Warangal 22
TYPES OF PANELS SIZE No. OF PANELS/ UNIT
WEIGHT DIAMETER OF BARS
1. Rectangular 1m x 0.5m x .08m 75 .096 T 8mm ф@120 mm 1.1. Square 0.5m x 0.5m x .08m 4 .020 T 8mm ф@120 mm
2. L shaped 3m x 1m x .15m 8 .450 T 8mm ф@75 mm 3. T shaped 3m x 2m x .15m 7 .900 T 8mm ф@75 mm 4. Lintel beam 2.1m x .30m x .15m 15 .095 T 2-12mm ф(top)
3-16mm ф(bottom) 5. slab 3.2m x 0.5m x .12m 46 .192 T 8mm ф@75 mm(1º)
8mm ф@ 120 mm(2º)
Fig 3.12: Final 3- Dimensional view of pre-cast rcc
Table 3.1: Table showing the specifications of all types of precast panels
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National Institute of Technology, Warangal 23
CHAPTER 4
CONSTRUCTION METHODOLOGY
Precast concrete is a construction product produced by casting concrete in a reusable mold or
"form" which is then cured in a controlled environment, transported to the construction site and
lifted into place. The use of precast concrete panels makes building much easier as they are
useful for many different applications. They can be used as the outside of a home, or for walls
inside the home. Most commonly found in commercial applications, precast concrete panels are
also very popular among modern home builders.
4.1 Site clearing: The construction process involves a large amount of materials and employees
who are often working on a tight schedule. It's no surprise then, that at the end of most projects
the site is quite messy, full of debris, extra materials and dirt. The area to be excavated filled
shall be cleared of fences, trees, plants, logs, stumps, bush, vegetation, rubbish, slush, etc. and
other objectionable matter. If any roots or stumps of trees are met during excavation, they shall
also be removed. The material so removed shall be burnt or disposed off as directed by
Engineer.
4.2 Supply of steel moulds: The advances in casting technology were made possible through the
continued development of high performance moulds. Using one steel mould we can construct
large number of panels (refer Table 4.1).
TYPE
NUMBER OF MOULDS USED
COST PER MOULD
Rectangular mould
20
Rs9,600.00/ea
Square mould
2
Rs2,000.00/ea
L-shape mould
3
Rs45,000.00/ea
T- shape mould
3
Rs90,000.00/ea
Lintel mould
4
Rs9,500.00/ea
Slab mould
12
Rs12,000.00/ea
Table 4.1: Number of steel moulds ordered with cost
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National Institute of Technology, Warangal 24
4.3 Excavation:
All excavation work shall be carried out by mechanical equipments unless, in the opinion of
Engineer, the work involved and time schedule permit manual work. Excavation for permanent
work shall be taken out to such widths, lengths, depths and profiles as shown on the drawings or
such other lines and grades as may be specified by Engineer. Rough excavation shall be carried
out to a depth 150 mm above the final level. The balance shall be excavated with special care.
Soft pockets shall be removed even below the final level and extra excavation filled up as
directed by Engineer should be carried out just prior to laying the mud-mat.
All excavation shall be done to the minimum dimensions as required for safety and working
facility. Prior approval of Engineer shall be obtained by Contractor in each individual cases, for
the methods he proposes to adopt for the excavation, including dimensions, side slopes,
dewatering, disposal, etc.
4.4 Supply of materials:
To calculate the number of bags of cement you need for a job you need to know two things.
How many cubic meter of concrete does the job require?
How many cubic meter of concrete does each bag produce?
4.4.1 PRECAST RCC HOUSE
Total quantity includes (from the detailed estimation APPENDIX A):
Plinth belt = 3.65 m3
T-shaped panel = 9.1 m3
L- shaped panel = 6.85 m3
Rectangular panel = 3.04 m3
Square panel = 0.08 m3
Lintels = 1.27 m3
Slab = 6.17 m3
Total = 30.19 m3
Mix = M 20 grade
Cement: Sand: Aggregate = 1 : 1.5 : 3
Volume = 5.5
Total volume Ingredients using = 30.19 / 5.5 = 5.489 m3 ~ 5.5 m3
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National Institute of Technology, Warangal 25
Volume of cement = 1 x 5.5 m3 x 1440 kg/ m3 = 7920 kg
Therefore, number of bags of cement = 7920 / 50 = 159 bags
Volume of sand = 5.5 x 1.5 x 1.5 (voids space = 1.5)
= 12.4 m3 per house
Volume of aggregate = 5.5 x 3 x 1.8 (voids space = 1.8)
= 30 m3 per house
4.4.2 CONVENTIONAL BRICK MASONRY
Total quantity includes (from the detailed estimation APPENDIX H):
Plinth belt = 3.75 m3
Column = 8.1 m3
Beam = 7.5 m3
Lintel = 2.875 m3
Square panel = 0.08 m3
Slab = 16.238 m3
Total = 42.213 m3
Ready mix concrete:
PCC - 15 m3
Column footing - 9.06 m3
Reinforcement :
Beam - 0.5 Tons
Column - 0.52 Tons
Slab - 0.4 Tons
Lintel - 0.33 Tons
Total - 1.75 Tons
Mix = M 20 grade
Cement: Sand: Aggregate = 1 : 1.5 : 3
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National Institute of Technology, Warangal 26
Volume = 5.5
Total volume Ingredients using = 42.213 / 5.5 = 7.67 m3
Volume of cement = 1 x 7.67 m3 x 1440 kg/ m3 = 11044.8 kg
Therefore, number of bags of cement = 11044.8 / 50 = 220 bags of cement per house
Volume of sand = 7.67 x 1.5 x 1.5 (voids space = 1.5)
= 17.25 m3 per house
Volume of aggregate = 7.67 x 3 x 1.8 (voids space = 1.8)
= 41.41 m3 per house
Brick 6-inch = 230 x 150 x 100 = 0.00345 m3
Number of bricks = 40 / 0.0035 = 11594.2 bricks
Mortar
Cement : Sand = 1 : 6
Brick Size = 0.23 x 0.15 x 0.10
Brick with mortar = 0.24 x 0.16 x 0.11 = 0.004224 m3
Number of bricks for 1 m3 of brick work with mortar = 237
Volume of bricks without mortar = (0.23 x 0.15 x 0.10) x 237
= 0.817 m3
Volume of mortar = 1 – 0.817 = 0.183 m3
Total volume of ingredients = 0.183/7 = 0.026 m3
Volume of cement = 1440 x 0.026 = 37.64 kg
Number of bags of cement = 37.64/50 = 1
Volume of sand = 0.026 x 6 = 0.156 m3
Plastering
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Area = 187.5 m2
Thickness of external plastering = 1.5 cm
Volume = 187.5 x 0.015 = 2.8125 m3
Thickness of internal plastering = 1 cm
Volume = 187.5 x 0.01 = 1.87 m3
Total volume = 2.81 + 1.87 = 4.6 m3
Cement : sand = 1 : 4
Total volume of ingrediants = 4.6/5 = 0.92 m3
Volume of cement = 1440 x 0.92 = 1324.8 kg
Number of bags of cement = 1324.8/50 = 27 bags
Volume of sand = 0.92 x 4 = 3.68 m3
4.5 Making of precast panels:
Precast concrete is a construction product produced by casting concrete in a reusable mold or
"form" which is then cured in a controlled environment, transported to the construction site and
lifted into place. In contrast, standard concrete is poured into site-specific forms and cured on
site.
By producing precast concrete in a controlled environment (typically referred to as a precast
plant), the precast concrete is afforded the opportunity to properly cure and be closely
monitored by plant employees. Utilizing a Precast Concrete system offers many potential
advantages over site casting of concrete. The production process for Precast Concrete is
performed on ground level, which helps with safety throughout a project. There is a greater
control of the quality of materials and workmanship in a precast plant rather than on a
construction site. Financially, the forms used in a precast plant may be reused hundreds to
thousands of times before they have to be replaced, which allows cost of formwork per unit to
be lower than for site-cast production.
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National Institute of Technology, Warangal 28
3 stages of precast construction:
Casting – includes mesh placing inside steel mould, fixing of embedded parts,
concrete pouring,
Curing - Steam curing - a process for hardening concrete, cement, and mortar that
involves exposure to warm steam. Materials subjected to this hardening technique tend
to cure more uniformly and also much more quickly than those hardened via other
processes. There are some disadvantages to this process that must be considered before
deciding to use it for curing, and there may be certain applications
where steam curing is not appropriate. Steam curing requires a fraction of the time
involved with traditional curing and quickly strengthens the products so they can be
used immediately.
Formwork removal
4.6 Storage of panels :
Working with the precast concrete panels is not like working with plywood or other building
materials. They are bulky and very heavy. This means that you will need to have the assembled
materials in place before you go trying to lift these heavy panels into place. Plan for how many
panels you will need, and have them ready for when a crane can be available. You will also
have to determine the different elements like windows, doors, and interior walls. The walls will
require use of a crane to lift the precast walls off of the delivery truck and into the correct spot
for installation. You need to arrange for a crane, and crane access to the construction site. Be
sure to check with your city to see if permits are needed for the crane usage. 4.7 Installation :
Once the plinth belt is built and level, you will need to bring the crane into position to lift the
panel off the truck and position it to start the wall (refer Fig 4.1).
L-shape panel - First of all, Place the L-shape precast concrete panels on a corner of a wall so
that you have a definite starting point. Use the crane and set the first wall into place. This wall
will need to be braced with 2 by 4's on either side to keep it upright and vertical. L-shaped
panels are placed in corners for load transfer from slabs. This type of panels serves as a column
in conventional framed structure. In this type of panels, concrete haunch (0.15m x 0.15m) is
provided at the bending portion in order to increase the moment of inertia there by to decrease
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National Institute of Technology, Warangal 29
slenderness ratio. Only female sockets (5cm x 2.5cm) are provided on L-shaped panel, such that
male sockets of each wall panels are attached firmly to the female sockets of L-shaped panel
properly without affecting its dimensions. These male and female sockets are sealed using
aluminum tower bolt of 150 mm.
T-shape panel - Then place T-shaped panels on all the junctions. Use the crane again for placing
heavy T-shape panel. This should be at a right angle to the first so that the braces can be
removed and the wall will have a stable starting point. The next wall should form a 90 degree
angle to the first and will make it possible to remove the braces. The manufacturer builds in pre
set holes that will fit together and allow for bolts to hold them in place. T-shaped panels are
placed in corners for load transfer from slabs. This type of panels serves as a column in
conventional framed structure. In this type of panels, concrete haunch (0.15m x 0.15m) is
provided at the bending portion in order to increase the moment of inertia there by to decreasing
slenderness ratio.
Only female sockets (5cm x 2.5cm) are provided on T-shaped panel, such that male sockets of
each wall panels is attached firmly to the female sockets of T-shaped panel properly without
affecting its dimensions. These male and female sockets are sealed using aluminium tower bolt
of 150 mm.
Then place rectangular wall panels in between corner L-panels and junction T-panels. Once you
have set a few concrete panels into position along your wall, it is a good idea to take the time to
seal them with a waterproof sealer or bolt them with aluminium tower bolt of 100 mm. After
you have a few panels set, and sealed, you can continue to erect with lintel beam panels, square
panels and slab panels. Take your time and make sure that they form a tight seal. Lintel beam
act as a continuous beam over rectangular wall panels in order to fix all panels in a straight line.
A concrete slab is a common structural element of modern buildings. Here precast concrete
slabs are arranged depends upon the room dimensions.
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National Institute of Technology, Warangal 30
Figure 4.1: Construction stages of Precast RCC panels