Firoz Project Mtech

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 %



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



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.



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



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).



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



& 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.



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



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



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



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



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.



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)



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



Fig 3.3: 3-Dimentional view after arranging precast panels



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



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



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 L-shaped steel moulds used: 3


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



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 T-shaped steel moulds used: 3


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


of 150 mm.

Fig 3.7: T- shaped panel with size 3m x 2m x .15m 1m

2m



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 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



3.2.5 Slabs

Purpose: roof covering

Specification: Length L= 3.2m, width= 50cm, thickness= 12cm


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



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



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



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



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



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



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.



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



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


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.



Figure 4.1: Construction stages of Precast RCC panels

Documents

Firoz Project Mtech