chepter-01 & 02
DESCRIPTION
nmhjTRANSCRIPT
CHEPTER-01
1.1 Introduction about the establishment Span Engineering (Pvt) Ltd was established in 2003. They are construct apartments to well
standard architectural designed under observation of qualified Civil engineers.
The Company’s conception is to build a trusted brand name to make their valued clients proud
of being an owner of “Span Tower” apartment where they are going to live with generations for
a longer life. The ambition of Span Tower Management is to maintain reliability and reputation
for years ahead.
The company reaches its tenth year of constructing semi luxury, luxury and super luxury
apartment complexes in the city of Colombo and it is a great achievement of young three
entrepreneurs who grew up the company to the top level of business trade in Sri Lanka. They
have been able to overcome all past challenges with their high dedication, determination and
contribution to the Company. Finally, The Company has been widely expanded its business
bringing their brand name “Span Tower” to the world.
Span Engineering was built with a vision of offering affordable luxury apartments as an aspect
that still remains a cornerstone of the company, having completed over eleven condominium
projects in Colombo over the years. Comfort, style and elegance are the hallmark of Span Tower
brand and the interiors of all apartment complexes reflect these qualities with tasteful,
smoothing and elegant colors and textures combined to create the ambience of graceful luxury
living.
1.1.1 Establishment details
FIGURE 1.1.1 Logo of Establishment
Span Engineering (Pvt) Ltd.
48/3B1, Dharmarama Road, Wellawatte, Colombo-6, Sri Lanka.
Telephone: +94 (0) 11 2508655, +94 (0)11 2507997 Fax: +94 (0)11 2559165
Email: [email protected]
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URL: www.spantower.com
1.1.2 Vision The perfect home for your peaceful life.
1.1.3 Mission Our mission is to exceed the expectations of every client by offering outstanding customer
service, increased flexibility, and greater value, thus optimizing plan functionality and
improving project operation efficiency. Our team is distinguished by their functional and
technical expertise combined with their hands-on experience, thereby ensuring that our clients
ultimately receive a homely apartment up to their satisfactory living style.
1.1.4 Goals Achieve highest level of Technical Standards and professionalism.
To develop, promote use of domestic technology and local materials.
Improve the management and Human Resources of the corporation.
To exceed the expectations of every client by offering outstanding customer service,
increased flexibility, and greater value, thus optimizing plan functionality and improving
project operation efficiency.
1.1.5 Organization chart 1. Hierarchy of head office
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Figure 1.1.2 Organization chart of Head office
2. Hierarchy of site management (under the project manager)
Figure 1.1.3 Organization chart of Site management
1.1.6 Management style
Approximately 40 staffs are employed in this company. Office hours are from 8.30 am to
4.30 pm on week days and Saturday is a half working day. But in construction sites works begin
at 8.30 am and finishes at 6.00 pm, Saturdays and Sundays are considered as normal working
days. Over time payments are paid each and every hour after 6.00 pm at works sites. A new
employee should be worked for 3 months to consider for appointment as a permanent staff. This
duration period of 3 months are called as provisional period. EPF AND ETF are allocated after
this period.
1.1.7 Leaves for employees There are 28 days of leave allocated for employees annually. This leaves consist of 14
annual leaves, 7 sickness leaves and 7 casual leaves. But during the provisional period employee
is allowed to take only ½ day leave per month.
1.1.8 EPF & ETF The EPF & ETF payments contributions as follows;
1. EPF – Employees Provident Fund
8% contribution from the basic salary of employee per month 12% contribution of
employer considering the salary of employee, per month this will be remitted to the Central
Bank of Sri Lanka Employee’s Provident Fund. EPF benefits could be withdraw on
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resignation/retirement or after completion of 55 years for male employees and after completion
of 50 years for female employees.
2. ETF – Employees Trust Fund
Company will contribute an amount of 3% of the employee’s salary to Employees Trust
Fund. This ETF money can be withdrawn after completing five year of working time period.
1.2 Site management Management is a very important process in any kind of work. Site management is the
process of interrelation of major functions such as planning, organizing, controlling, and
leading. Those things are directed in the achievement of objectives and goals of the project.
Four company staffs are worked in this site for technical assistance and other works.
1. Site Engineer
Construction works are checked by him according to the drawing details provided by the
structural engineer and the company’s requirement.
2. Technical Officer
All the construction works are explained to the sub-contractors, laborers are controlled
and petty cash is managed by this person.
3. Store Keeper
Store keeper is in charge of all the stored tools, equipments and materials in the store.
4. Supervisor
Labour supervision and ensuring the quality of the works and Monitor work progress and
quality control by using inspection and test plans.
1.2.1 Labour management Labour management is one of the greatest difficult tasks in construction management.
Labours may come from various backgrounds such as on educational, on ethnic, on local and
outsiders, skilled, on physical status etc.
In our site normally the labours employed at the sites were divided into two groups. They are,
1. Skilled labours – Masons, carpenters, bar benders, electrician, tillers, plumbers…etc. are
considered as skilled labours.
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2. Unskilled labours – All other workers who were working as helpers are considered as
unskilled labours.
A good labour management is a mirror of progress of the company. To increase and
develop the production every worker was involved to a specified work or duty and minimized
the unproductive hours.
Also in some special cases a target was fixed to perform and the workers were given
unproductive O.T hours as incentives if they were able to overcome the target. And also every
unskilled and apprentice workers were given chances to improve their abilities by working with
skilled and semi-skilled persons.
1.2.2 Site documentsIn our site, various types of documents maintained for proper management
1. Documents at site
When we involve in a construction work, always we have to check the dimension and
quality of the work and progress of work. For this work, we have to refer many documents at
site.
Details drawings, bar chart
Shop drawings
Bills of quantities
Specifications
Method Statement
2. Files to be maintained at work site
There are number of files that are maintained at site office in order to have proper
management of work. They are,
Minutes of meetings
Monthly bill file
Staff attendance
Test report file
Sub-contractors file
Clients requirements
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3. Daily maintaining records
Several records are daily maintaining at the site as the work progress.
Weather records
Daily diary
Labour attendance chart.
Vehicle movement books.
Stores inventory.
Concrete pouring chart.
Tool issue register
4. Storage management documents
Store management is a main part acting in a construction site. For this purpose
maintaining documents is very important. The important documents which are commonly used
in our site is as follows,
Goods Receive Note
Goods Transfer Note
Gate Pass Note
Stores Record
Material Requisition Note
Fuel & Spare art Requisition Note
1.3 INTRODUCTION ABOUT THE PROJECT
1.3.1 Span Tower 14 Span Tower 14 is consisting of eight (8) floors, 26 units with five different floor areas. It
situated in Arethusa Lane, these condos are centrally located and very close to major schools,
hospital, restaurants, places of religious worship and markets.
1.3.2 Project detailsName of Project : Span Tower 14
Location : No-06, Arethusa lane, Colombo-06
Main contractor : Span Engineering (Pvt) Ltd
Architect : Archt.P.W.A.H.Wickramarathna
Structural design : Eng.D.T.Rajasekaran
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Date of Commencement : October 2013
Date of Completion : December 2015
Duration : 2 years
Total estimated cost : Rs.387 Million
Type of sub-contracts : Measure and Pay
Amount of retention (for sub-contractors) : The retention from each payment shall be 10% of the Initial contract amount.
1.3.3 Site location
Figure 1.3.2 Site location
1.3.4 Typical floor plans
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Figure 1.3.2 1st, 2nd and 3rd Floor key plan
Figure 1.3.3 4th to 7th Floor key plan
1.3.5 Standard features Electricity: 30A Single Phase, Stand by Generator for Common area.
TV System: Provision for Cable TV in Master Bed Room and Living.
Telephone System: Telephone Outlets in Living and Master Bed Room.
Water System: Main Supply from water board. Individually Metered.
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Sewerage and Waste water System: Design to International Standard, Garbage
Collection by the MC.
Vertical Transport: One Stairway, One Lift.
Fire Protection System: Designed to Municipal Fire Department Requirement.
Recreation System: Gym on the Rooftop and Roof Garden.
Car Parks at the Ground Floor.
24 Hours Security Service.
Overhead water tanks.
1.3.6 Finishes and fittings Windows of rust proof powder coated Aluminum.
Solid Doors and Imported locks.
Standard Light Fittings and Ceiling fan for each Room.
Provision for A/C in Master Bedroom.
Provision for A/C in Living hall
All Floors of Porcelain Tiles.
Pantry Cupboard with Granite top.
Provision for Washing Machine.
Imported toilet fittings and accessories.
Intercom system to Security point and Apartment.
Hot water supply for Master Bathroom.
Electrical Provision for Instant water heater in 2nd bathroom
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Figure 1.3.4 3D rendering view of building
1.4 SAFETY
1.4.1 Introduction of site safety Prevention of accidents is called as safety. So there is a direct ling in between safety and
accident. From the accident in site data it has been seen that 85% - 95% of accidents are
preventable. An accident is an unexpected occurrence which can take place at construction sites
mostly happen to men going about their daily work and consequently.
1.4.2 Common type of accidents at Site Unsafe practice of individual workers.
Falling from height
Electric shock
Uncontrollable contact between men and equipment, material or vehicle.
Because of safety officer of site those personnel injuries and property damage due to accident
can be reduced.
1.4.3 Causes of accidents Accidents may be caused due to,
Mechanical factor
Unsafe Conditions
Environment factor
Unsafe Acts
Management factors
1.4.4 Precautions of accidents Before starting any work officers should be checked about safety.
Any personnel working at high level, safe and proper working platforms and scaffoldings
should be used.
Ladders should always stand on a firm base.
Adequate lateral support bracing should be used when fitting scaffoldings.
A qualified electrician should carry out electrical installations.
Work at heights in strong wind and heavy rain is prohibited.
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Safety rules and regulation should be followed.
Safety precautions have been taken at site in order to avoid unwanted accidents. Labors are
instructed to use safety equipment while they are working. Unwanted accidents and injuries
effected to construction progress as follows,
Working time loss by the injured person.
Working time loss witness and the accidents investigations.
Production stoppages, Work delays.
Possible legal and other costs.
Reduced output when the injured person is replaced and subsequently when he returns to
work etc.
1.4.5 Safety equipments 1. Safety helmet
Everybody should wear a safety helmet while entering to a construction site. Even a drop
of a brick or nail from a higher place can cause major damage.
2. Safety shoes
Safety shoes were worn while working in the site to protect feet and convenience of
working.
3. Safety belts
Safety belt is very useful while working in a very higher place than ground. The rope is
fixed in a permanent place or to a fixed scaffolding, while the belt will be fixed on the
workers hip.
4. Safety goggles
Goggles were worn where there is a possibility of eye injuries due to flying particles and
dust.
5. Safety gloves
Protective gloves were given to the workers whenever there is a danger of injuries to
hands.
6. Safety clothes (Apron)
According to the type of work safety clothes should be used. (E.g. Welding work)
7. Safety mask
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When working with dust or chemicals.
8. Safety net
It prevents the falling materials to be spread over the land which is the best method of
protecting the neighbors.
Also, in our site there is a barrier at the entry, and some advices are displayed on boards as
follows,
“ALWAYS WEAR SAFETY HELMETS”
“SAFETY FIRST”
“NO ENTRY”
A basic first aid box, clean drinking water, toilets and washing facilities are also available in the
site.
Figure 1.4.1 Safety equipments
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CHEPTER-02
2.0 MY TRAINING EXPERIENCES
2.1 FORMWORK Formwork is a structure, usually temporary, used to contain poured concrete and to
mould it to the required dimensions and support itself. Formwork should be accurate enough
and safe since size, shape and alignment of slabs, beams, columns and other concrete
structural elements depend on accurate construction of formwork.
Although several types of materials are available in the market, in our site, we used plywood
sheet and timber joist for formwork.
Factors which were considered in formwork:
Must be rigid to withstand the load and maintain the shape of the member.
Must be stable enough to maintain large members.
Must be reusable – to reduce cost.
Surface of the formwork should be smooth.
Joints should be fixed firmly to resist against leakages.
2.1.1 Materials used in formwork
1. Plywood sheet: 8’x 4’ Plywood sheet with ½” was used since the surface is very
smooth and easy to handle.
Advantages of using plywood sheets
Good surface finish can be obtained.
Plywood formwork is economical because this can be used repeatedly
although the cost of plywood is higher than class II timber planks.
Since the plywood sheet covers large area, the time taken to construct the
entire shuttering is less.
It can be easily sawn to the required shape.
Disadvantage of using plywood sheets
Even after removing the shuttering, adhered plywood particles can be seen on
the surface when normal plywood used.
Peeling of layers with the time.
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Due to the slenderness of the sheet large numbers of strengthening cleats are
required, otherwise formwork gets deflected.
2. Timber joist: 2”x 2”, 4”x 2” joists were used in 8’ and 10’ lengths according to the
requirements
3. Galvanized iron pipes: 2” GI Pipes were used and specially to lock columns and
beams against expansion of the formwork.
4. Adjustable jack: Used to support structural members.
Figure2.1.1 Adjustable jacks
5. U – Jack and T- Jack: Used to support members with GI pipes or Adjustable jacks.
Figure 2.1.2 U-Jack Figure 2.1.3 T-Jack Figure 2.1.4 Coupler
6. Thread bar and Butterfly: Used to lock members with the help of GI pipes.
Figure 2.1.5 Thread bar and Butterflies
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7. Couplers: Used to connect one GI pipe with another.
2.1.2 Formwork for columns Columns are very critical structural members in the building therefore columns
formwork should be prepared carefully. Column formwork was designed by considering the
pressure. In our site column formwork was made by plywood & its height was decided by the
Site engineer according to the design. Verticality of the column, cover of the column,
stability of adjustable steel props were checked before concreting work.
Procedure
1. Before carrying out preparation of formwork, the grid lines were marked. Then
200mm offset lines were marked using the steel tape.
2. After marking the column, small 4 plywood piece were placed around the
marking area (place the kicker). Kicker concrete makes easy to fix the column
formwork as a box and it provides easy handling of the column formwork. Thickness
of the kicker concrete was 4”.
3. All loose particles and debris were removed before to place the side boards and
before fixing formwork, diesel was applied to avoid adhere the plywood particles in
concrete surface also get the even smooth finishing in concrete surface.
4. Then three side of column formwork were fixed and other board was fixed after
finishing the rebar work.
5. Then the ply wood box was made stiffen by using G.I. pipes, separators,”C”
channels & tie rod. After that the column was supported using adjustable steel
supports & cables.
6. Finally the verticality of the column was checked and aligned by referring the
200mm off line. A plumb bob was used for this case.
Figure 2.1.6 Column kicker Figure2.1.7 Column formwork
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Vertical alignment of columns
As soon as concrete was laid on columns, we checked the vertical positions of the
columns to verify whether it is truly vertical. It was performed by using center plumb bobs
and measuring tape. The distance between the outer edge of the formwork and vertical string
was measured, this distance was measured in bottom and top. For the exact vertical both top
and bottom should be equal. It was checked in the four sides of the form work. If those two
readings were different, it was corrected by tightening or releasing the Adjustable jack
reference to the bottom reading.
Figure 2.1.8 Checking verticality of column
2.1.3 Formwork for beams After column concrete was completed, formwork for beams & slab were started.
Normally slabs and beams were casting together to maintain monolithic construction between
the structural elements. Therefore the formworks for slabs and beams were constructed as one
formwork. First formworks for beams were done.
Procedure
1. Initially the height between beam bottom and the floor was calculated from the
drawing.
2. Kickers were prepared using piece of plywood sheet and 2”x2” joist.
3. Prepared kickers were fixed on the columns using wire nails in required height.
4. Beam bottoms were prepared and fixed on the kickers according to the required
length of the beams and those beam bottoms were supported using Adjustable jacks.
5. Beam bottoms were levelled using spirit level.
6. Side boards for the beams were prepared and fixed with the beam bottoms GI pipes
were fixed to beam side boards to lock the beams.
7. Beam side boards were locked after completing slab formwork.
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Levelling of beam bottom
Figure 2.1.9 Schematic diagram of beam bottom levelling
Procedure
1. Plywood pieces A & B was fixed using a wire nail and C is movable.
2. A string was fixed along the beam bottom on top of plywood pieces A, B & C as
shown in the above picture.
3. Plywood piece C was moved along the beam bottom from A to B.
4. While moving, if there was any difference in between the top surface of the
plywood C and the string means the beam bottom is not levelled. In this kind of a
situation the adjustable jacks were adjusted till the string and top of the plywood
C become coincide.
2.1.4 Formwork for slab Slab formwork was started after beam side boards were fixed on their positions
accordingly. Scaffoldings were used for support the slab formwork in our site. Sometimes
adjustable jacks also can be used for formwork.
Procedure
1. After side boards for beams were laid, scaffolding frames were placed and fixed in the
places where slab formwork was required.
2. U jacks were placed inside each and every corner of the scaffolding frames.
3. Two 4” x 2” joists were place along every U jack head according to the required
length of the slab.
4. GI pipes were placed across the joists with another set of 4” x 2” joists parallel to the
GI pipes.
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5. Plywood sheets were placed on top of the GI pipes and nailed to those 4” x 2” joists.
6. Finally the slab was levelled after reinforcement before concreting.
Figure 2.1.10 Arrangement for slab formwork
Levelling of slab and beam formwork
First of all the engineering level was placed and leveled properly. Earlier we have marked
the 1000 mm level on all the columns. Then find the height of collimation (H).
H=1000 mm + X
After we can easily calculation slab and beam bottom level and then we can level the
formwork easily using engineering level. For the calculation we should get to know the floor-
to-floor height, slab thickness, beam height, drop areas etc.
Figure 2.1.11 Levelling the beams and slab formwork
The calculation was done as follows,
Thickness of plywood sheet = 15 mm
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Inverted Staff
Floor to floor height = 3000 mm
Slab thickness = 150 mm
Height of collimation (H) = 1000mm+X
For slab,
Therefore, L = 3000 – H – 150 – 15 mm
For beams,
Beam height = 300 mm
Therefore, L = 3000 – H – 300 – 15 mm
Adjustable jacks to get the required level did small adjustments.
2.1.5 Formwork for walls
There were two types of walls were concreted in our site,
Lift wall
Guard walls for balcony
The wall forms consist of timber of steel sheeting supported by vertical studs and horizontal
Wales. Ties and bracers were also used to make the support strong. Small pieces of timber
known as spacers may be used and they are to be removed as the concrete reaches that level.
Procedure
1. The bracers were provided at horizontal distance of about 2m and they are supported
at ground level by stakes firmly fixed in the floor.
2. In case the wall is very high the formwork was supported on either side by guy wires
instead of bracers.
3. Many patent devices have come in the market to keep the sheets in correct position.
They may be used in place of wire ties and bolts.
4. Reinforcing steel, if necessary, is placed in position properly before laying of
concrete.
5. After placing the sideboards on the kicker they were locked using GI pipes, T rods
and rapid clamps. Normally the walls were constructed from floor to floor.
6. Finally verticality of formwork was checked as like checking of verticality of
columns.
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Figure2.1.12 Formwork for guard wall
2.1.7 Removal periods of formwork Formwork was dismantled in a certain period after the concrete work was done.
Members No of DaysBeam sides, walls & Columns 01Slab soffit 14Beam bottom 21Staircase soffit
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Table 2.1.1 Formwork removal periods
Some precautions and advices were given to worker while removing form work,
1. The time and manner of form removal was determined among the site supervisory
staff.
2. Forms for slabs soffits was removed piece with care. Column and forms can be
removed in full height panels and beam side forms can be removed together with the
corner forms in one piece.
3. Dismantling of forms in to large panels or dropping the forms can be dangerous may
and cause damage to concrete structure below as the forms can easily be released
from the concrete and dropped off unexpectedly. So extra care was taken in removing
props.
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4. Removed forms should not be thrown or dropped on to the floor, but should be
lowered on to a raised platform on trestles or handed from worker to worker.
5. Care was taken not to cause excessive impact to the freshly cast concrete or to cause
damage to its surface when removing forms.
6. Props were removed progressively with the forms and which were not removed too
many at a time.
7. Beams and slabs were re propped immediately after their soffit forms were removed
to avoid the deflection.
2.2 REINFORCEMENT
Reinforcement concrete is the most commonly used structural material in engineering
construction. Concrete is much weaker in tension than in compression. Its tensile strength is
approximately 10% of its compressive strength. Therefore, concrete is generally used in
conjunction with steel reinforcement, which provides the tensile strength in a concrete
member. After concrete gain its strength concrete and steel bars will act homogeneously.
During the training period, I came across the reinforcement works of Beam, Slab, Column,
RCC wall and Lift wall. All the reinforcements were carried out according to the drawings &
specifications.
2.2.1 Types of reinforcement bars In construction industry according to the type of work and design tor steel and mild
steel is used.
1. Mild Steel
This is a soft carbon steel. It is ductile and elastic able. The strength of this type of
steel is 250 N/mm2. The range of diameter available for mild steel are 6,8,10 mm.
2. Tor Steel
The strength of this type of steel is 460 N/mm2. These bars used as main bars of slabs,
columns, beams…..etc. The range of diameter available for Tor steel 10, 12,16,20,25, 32,
36, 40 and 50 mm bar sizes are available for tor steel with lengths of 6 m or 12m.
2.2.2 Identification of bars from drawing Reinforcement details in a drawing were expressed through a coding system to
simplify preparation and read the detail clearly as shown below.
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Example: 20 T 10-7-8” B denotes
20-Number of bars
T-Type of steel-Rib or Tor
10-Diameter of the bar in mm
7-Bar mark
8”-Center to center spacing
B-position of the bar-Bottom or Top
Also following abbreviations used,
B1- Bottom reinforcement
B2- Distribution bars in bottom net
T1- Top reinforcement
T2- Distribution bars in top net
C/C- Center to center
ALT-Alternatively
2.2.3 Bar bending schedule Bar bending schedule is a chart which gives a clear picture of bar length, diameter of
bar, bar mark, location of bar and bar shape.
In preparing bar schedules, a special code of practice was referred which specifies the method
and notations to be used (BS 4466). Cut lengths were calculated according to these
specifications. Lengths were given in near 25mm and weight of the bar was summarizing in
ton with 2 decimal.
The bars of a common diameter and shape were normally grouped together with the same
reference number when included in the same reference number to simplify the reading of
reinforcement details.
Member Bar Mark Type & Size Length of
Bar (mm)
No of Bars Total
Length
(mm)
Shape
B2 05 T25 2500 4 10000
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Table 2.2.1 Bar bending schedule
Rebar Calculation
Calculating No of Reinforcement bars per Ton
Consider diameter of 20mm Rebar,
Density = Weight / Volume, Volume = Area x Length Density of Tor Steel: 7850 kg/m3
Weight of a 20mm bar 6m length: Volume = π/4 x (20 x 10-3)2 x 6
W = [7850 x π x (20 x 10-3)2 x 6] / 4
W = 14.797 kg
No bars per Ton = 1000 / 14.797 = 67 bars
2.2.4 Cutting and bending of reinforcement The cutting and bending machines were located in the steel yard at nearby site. Bar
cutting was done according to the bar schedule. Requirement of shapes of the reinforcement
are varying according to their usages. So it is necessary to cut and bend reinforcement bars to
their required shapes and sizes before using for work. The cutting and bending of
reinforcement shall be in accordance with the requirements of BS4466.
But, in our site bar cutting work was done with electrical power metal cutter and bending
work was done by hands
2.2.5 Placing and tying of the reinforcement Another important factor in the construction work is placing and tying of
reinforcement. To get a better structure with appropriate strength according to the drawing
the following factors were considered in our site:
1. Cover distance
A cover block is essentially a spacer that was used to lift the rebar matrix off the
ground or form so that concrete may flow underneath the rebar.
Cover blocks were prepared by 1:3 cement sand mortar or the same grade of concrete and
binding wire was connected to the cover block. The required size of cover is specified in the
structural drawings.
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Figure 2.2.1 Cover block and it fixed in reinforcement
Table 2.2.2 Clear cover
distance for various concrete components
2. Lap length
When the length of reinforcement bar has to be extended in reinforced concrete structural
member splicing was used to join two reinforcement bars to transfer the force from one bar to the
joining bar. Also it helped to preventing slipping two bars. These lengths are called lap length. The
lap lengths are used according to the BS 8110. Lap length was varying as fallows according to
element. Nearly it was 52x small diameter in our site.
It was required to crank the bars most probably in both columns and beams. After cranking the load
should be transferred to the other bar axially. Typical lapping and cranking details,
Assumed D1>D2 (mm)
LL (Lap Length) = 52 x D2
CL (Crank length) = (D1 +D2+5) x 10 (mm)
Figure 2.2.2 Crank length and Lap length details
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Components Clear cover distance (mm)
Beam side, bottom, top 25
Slab bottom, top 20
Column 25
Lift wall 25
Basement wall 40
3. Anchorage length
This is very important in a reinforced concrete. The end of the reinforced bar was bend as an
anchor to prevent pulling off from the concrete. This length will vary with the bar type & diameter. In
our site the anchorage length was used as 20 times bar diameter.
Chemical Anchoring the Steel bars
In our site chemical Anchoring was used to fixing the starter bars in columns and beams. For
this purpose Hilty – RE 500 was used.
1. Marked the hole location.
2. The holes were cleaned by brush and blown out by blow pump given by the manufacture.
3. Chemical was injected by starting from the bottom of the hole by dispenser. Holes were filled
about half.
4. Required rebar was inserted to the holes.
Connection was kept 8 hours.
Figure 2.2.3 Chemical anchoring
Additionally, during the placement of reinforcement bars following members were involved
for keep the vertical and horizontal distances between reinforcement bars.
1. Stools
A space between top and bottom reinforcement bars was maintained by providing
stools. It was used in arrangement of reinforcement bars of slabs. Stools should strength
enough to bear the load without changing the gap of two layers.
There are different types of stool shapes and also different height it depend on the structure.
2. Stirrups (Shear links)
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For resistance to shear failure of beams and columns, stirrups were provided. For
stirrup preparation, 10mm Tor steel bars were used in the site.
3. Spacer bars
Spacer bars are used in beams of double or multi-layer reinforcements to hold main
bars in proper position. Also it help to enable aggregate particles while concreting. Usually
25 mm rebar was used in our site.
Figure 2.2.4 Stool and spacer bar
4. Starter bars
During placing of reinforcement the additional reinforcements (starter bars) were
provided for the extended elements to have a better bond between each component. In our
site starter bars were provided for balcony walls, stair cases, beams between lift columns,
lintels.
2.2.6 Reinforcement arrangement of beam and slab To tie beam reinforcements, two beam bars were kept in position & stirrups were
passed into these bars. Then the bottom beam bars & additional bars were slide through the
stirrups. When there were second layers of bars, they were tied after tying the intersecting
beams etc.
On top bars of beams, laps were located at the point of contra flexure. On bottom bars of
beams, laps were never located at the mid span of beams (the point with maximum bending
moment).
Slab reinforcement was started after the beams were fabricated. Initially spacing between
bars were marked on the slab formwork and the bottom net was fabricated. Then the top net
was provided near the beams since shear acts near beams. After that stools were placed in
between top and bottom net and finally cover blocks (3/4”) were placed.
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Stool
Spacer Bars
StoolStoolStoolStoolStoolStoolStoolStoolStoolStoolStool
2.2.7 Reinforcement arrangement of columns The main constituents of RC columns are the longitudinal bars, which take the main
load. These are tied by lateral steel bars called stirrups.
Stirrups was fixed while allowing the required spacing as indicated in the drawings. After
construction of the kickers, clear cover was checked. If it is not enough, spacing was kept by
cranking the reinforcement.
Figure 2.2.6 Column reinforcement
During the rebar arrangement of columns some technical points were considered,
The position of lap in column was properly placed and instructed to the labor to
minimize the weakness in main key of structure.
The RF in the lower column was cranked so that it will fit within a smaller column
above as shown below. Hence the lap should be started beyond the slab.
The crank should, if possible, commence above the soffit of the beam so that the
moment of resistance of the column is not reduced.
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Figure 2.2.5 Beams and slab reinforcement arrangement
Figure 2.2.7 Rebar arrangement for columns
For the same reason, the Rebars in the upper column should be the ones cranked when the
both columns are of the same size as in figure
Links were provided at the points where the bars were cranked to resist buckling due to
horizontal component of forces in the inclined length of bars.
2.2.8 Checking of reinforcement Before concreting, reinforcement were checked. This was done by our Site engineer and
Project coordinator. The followings were checked.
Type of Steel
No of bars
Size of bars (length & Diameter)
Lap length & Lap position
Stirrup arrangement
Spacing between multi layers
Steel fixing methods
Covering for steel bar
2.3 CONCRETE WORKS2.3.1 Concrete Concrete is the main composite material used in construction industries to fabricate
structural members. Concrete that is used in sites are expected to be high in quality, durable,
high in strength, impermeable and resistance to abrasion and fire. In order to achieve good
quality of concrete, materials used should be quality and materials should be mixed in proper
ratio as well as concrete should be placed properly and well compacted also well cured.
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In my training experiences, quality of concrete depends on
Type of aggregate
Quality of cement
The grading of aggregate
Water cement ratio
Mixing method and mixing time of concrete
Method of transportation
Method of placing the concrete and type of compaction
Curing the Concrete
Therefore a good concrete should be quality, workability and economical. During my training
experience I have realized that the characteristics vary among the batching plants.
2.3.2 Grades of concrete This is the standard method of expressing the Concrete strength. Concrete grade is the
expected cube strength at 28 days in N/mm2. In our site, according to the work, different
grades of concrete were used.
Grade Proportion Strength at 28
days in (N/mm2)
Usage
10 1:4:8 10 For small works
15 1:3:6 15 For Screed concrete without r/f
20 1:2:4 20 For Screed Concrete,
25 1:11/2:3 25 For Shear walls, lintels
30 1:1:2 30 For Columns, Beams and basement, Foundation
*Proportion Cement: Fine aggregates: Course aggregates
Table 2.3.1 Grades of concrete and their uses
The above-mentioned proportions of concrete aggregates are based on volume measures.
2.3.3 Factors to be considered before concreting The dimensions of the members were checked.
Reinforcement details were checked.
Cover blocks were checked.
Levels of the slabs were checked.
The supports of the members were checked.
Surface was cleaned using an air blower.
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Conduits for building services were checked.
2.3.4 Mixing of concrete In our site manual hand mixing was used only for small construction works like as
lintel placement, protective concrete for water proofing. The mixing can be carried out by
measuring the quantities of materials by volume and the amount of water depend on the
required workability. For this purpose gauge box (300 x 300 x 375 mm3) was used, and this
volume is equal to one 50 kg cement bag, which is 0.035 m.
2.3.5 Ready mixed Concrete Ready mixed concrete was used for larger works in our site as like concreting the
columns and slabs. Which was delivered from ICC Concrete Batching plant. Normally in
ready mixed plants used the weigh batching method to mixed concrete. As this method they
can surely get the necessary strength than the volume batching. Ready mixed concrete is
supplied to sites in specially designed truck mixers. Which are basically mobile mixing
drums mounted on a lorry chassis. The capacity of truck mixtures varies with the models.
Normally 4, 5 and 6 m3 are the common sizes.
The necessary strength of concrete and required slump was checked during the delivery of the
concrete.
2.3.6 Procedure of concreting Concrete was poured through a pump line by using a pump car. Concrete was
transported by using trucks. Slump test and preparing the cubes for the cube test were done in
the site for each truck. Compaction was done using porker vibrators. When placing concrete,
it should be ensured that initial setting of concrete has not started. Initial setting time for
ordinary Portland cement concrete is 45 minutes. Concrete should be deposited as closely as
possible and without segregation.
Normally concrete was placed in even layers and each layer must be well compacted before
the next layer was placed. Also it should be ensured that each layer was placed before the
previous layer has got set.
Thickness of concrete was maintained by level gauge rod. It is a straight rod and set the
thickness in that rod. After spreading and rough levelling the concrete that rod was penetrated
into the concrete in various places and measured the thickness. If thickness is right final
levelling of surface was done by float
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Figure 2.3.1 Placing the concrete
Figure 2.3.2 Poker vibrator & method of applying
Following points to be considered when concreting,
Before discharging the concrete in to the pumping pipe 1:3 cement sand grout was
added to the pump car & pumped through the pipeline to prevent the concrete being
stuck to the pipe inside surface.
Concrete should not be allowed to fall freely about more than 1 m, in order to prevent
the formation of air pockets and segregation of materials.
Concrete should not be allowed to fall freely more than 1500mm or 5 Ft. So the
segregation can be happen and the honeycomb can be seen. To prevent the above case
a P .V .C pipe is used inside of the column for pouring the concrete.
For the elements where the thickness or the height of the work is more than 6 inch
concrete is placed in even layers of thickness not exceeding 150mm. Each layer is
well compacted before the next layer is put. A concrete layer has to be placed before
the previous layer has set.
For the elements where the thickness or the height of the work is more than 6 inch
concrete is placed in even layers of thickness not exceeding 150mm. Each layer is
well compacted before the next layer is put. A concrete layer has to be placed before
the previous layer has set.
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Correct Incorrect
It was placed vertically in concrete and held in one position until air bubbles short to
come to the surface. This was repeated about every 0.5 to 1 m intervals. The concrete
was placed in layers of not more than 600 mm thick.
2.3.7 Field test on concrete 1. Slump test on fresh concrete
It is one of the most important test performed the site to measure the workability of the
concrete in the site. It’s mandatory to identify the workability of the concrete before using it.
Concrete samples were taken from truck mixers at every 5m3. Variations in the results of
slump tests indicate changes have occurred in the grading or proportions of the aggregate, or
in water content.
Slump test Apparatus: Slump cone, Tamping rod, Steel plate, Scoop Trowel
Figure 2.3.3 Slump test apparatus
Procedure of the slump test in our site
1. First steel plate, slump cone, tamping rod, plate knife were well cleaned and washed
properly.
2. Next diesel was applied on slump cone internal surface.
3. The slump cone was kept on a tray and filled 1/3 of the cone with concrete.
4. The concrete was compacted using an iron rod for 25 times (gravity flow).
5. 2/3 of the cone was filled and compacted 25 times.
6. Finally the cone was filled fully and compacted 25 times with the iron rod.
7. Then slump cone was removed vertically & slowly.
8. The height of the slump was measure as shown in Figure 2.
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Figure 2.3.4 Slump test in site
There are three kinds of slump can be occurred as follows,
Table 2.3.2 Measurements of slump
For the greater accuracy of the results, the sample should be consisting of concrete taken
randomly from more than three different places. Normally in our site, slump was around 120
(+/- 20) mm in our site.
2. Cube tests on hardened concrete
4 cubes were casted from one concrete truck mixer when cumulative volume is equal to
the 20m3. The cubes were checked for compressive strength in 7days and 28 days. The
curing of those cubes was done in a water tank at the site.
Test apparatus
1. Mould – mould is 150mm cube which, has a base plate.
2. Steel bar – 380mm long steel bar, which has diameter of 25mm in ramming face.
30 N/mm2 -Grade
145 mm - Slump height
150mm x 150mm x 150mm - Cube size
Procedure of cube test
1. First mould well cleaned by removing all set concrete and other impurities.
2. Next the diesel was applied on the internal faces of the mould for maintaining fine
smooth finish of the concrete cube.
3. Concrete sample was taken from truck mixture.
4. Mould were filled in three layers of concrete.
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Degree of workability Slump (mm)Very low 0 – 25Low 25 – 50Medium 25 – 100High 100 – 175
5. Each layer was tamped with 35 strokes with the tamping rod having 380mm long, 25mm2 area and 1.8 kg weight.
6. After compacted well allow for hardening.
7. After 24 hours remove the mould and concrete cubes were put in curing tank.
8. The cubes were checked after 7day and 28 days.
Figure 2.3.5 Cube test mould
2.3.10 Curing process of concrete
Curing is very important part on concreting. Once the formwork was removed the
surface water will start to evaporate. In our site gunny bags were placed on the surface and
spray water. The characteristic of the gunny bag is absorbing water. Then the gunny absorbs
more water and will keep much time. This type of curing method was very useful in our site.
This minimizes the continuous curing. As site engineer instructed the curing was done for
minimum four days commencing 24 hours after placing. The surface was kept damp for
above mentioned four days.
Figure 2.3.6 Curing process of concrete
2.3.9 Defects on concrete 1. Honeycombs
These are the major defect in concrete. Honeycombs will occur due to,
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Segregation of materials when placing concrete
Usage of improper mixture of concrete
By using incorrect proportions of materials
Due to high water cement ratio
Due to poor mixing of materials
Poor compaction of concrete
Bad formwork arrangement
Honey combs forms due to improper vibrating and grout leakages when placing the
concrete. Small and moderate honey combs were observed in some places of columns, a
special method was followed to rectify them in our site.
Treatment of honeycombs
1. The weak concrete was hacked and removed to expose sound concrete surface.
2. To keep clearance around reinforcement 12mm thick concrete layer was
removed.
3. Surface was cleaned by water.
4. After dried, construction grout was poured. The 25kg grout bag is mixed with
4.2ltr water
5. 3 days curing was done & ledge was removed.
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Figure 2.37 Treatment of honeycomb surface
2. Thermal cracks on Concrete
The reaction between cement and water generates heat. As the concrete’s temperature
increases it expands. Once the peak temperature has been reached, the concrete starts to cool.
At this point concrete attempts to crack.
Figure 2.3.9 Thermal cracks on concrete surface
Cracks may also be caused by differential temperatures in thick members. When the surface
layer cools and contracts, temperature movement is restrained by the core of the member
which is still at a higher temperature, and hence cracks may form in the surface.
2.3.10 Problems and experiences were encountered Slump measurement was slightly difference from measurement of the batching plant,
During the transporting of concrete which was lost small amount of slump. Due to
concrete was lost its workability so we added the small amount of water before
pumping the concrete and as possible as, we poured the concrete quickly without
latency.
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During the pumping the concrete, pipe joint was broken and lost the concrete. We
fixed that problem and ensured the other pipe’s joints and continue the concreting
work.
When screed concreting for roof top, grade 15 concrete was ordered but initially grade
15 concrete was not pumped by pumb car. So first grade 20 concrete one truck was
pumped after grade 15 was pumped to avoid the segregation of particles and deposit
of the grout internal surface of the pipe.
2.4 LEVELLING Mostly levelling in construction sites refers the identification of vertical distance from a
point or surface according to several requirements. A levelling instrument is used to measure
the vertical distance in construction sites. We used a Dumpy Level for levelling purposes in
the site.
2.4.1 Automatic dumpy levelMainly consists of 3 parts:
1. Tripod – The instrument is fixed above this.
2. Automatic Dumpy Level – Used to take the reading.
3. Staff – Staff is held at a point to measure.
Figure 2.4.1 Levelling instrument with tripod and Staff
Procedure to set up the instrument
1. Tripod was fixed on the surface up to visible horizontal level firmly.
2. Instrument was fixed above the tripod.
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3. Two levelling screws in the instrument were turned in opposite directions at the same
time, and the other screw was also turned in required direction to bring the bubble to
the center in the instrument. (At this time the instrument will be levelled)
4. The telescope was turned in 90 degree and the bubbles were checked.
5. Finally the eye piece and the cross hairs were focused clearly.
2.4.2 Marking level line in columns Before fix kickers above columns to lay beam bottoms, a levelled line should be
marked in all the columns. We marked a 5’ line in the columns.
Procedure
1. Point ‘A’ was marked on the column in 5’ height using a measuring tape and a pencil.
2. The instrument was levelled and a pencil was slightly moved up and down while
another person was looking through the instrument. This process was done until the
pencil’s point and the cross hairs become coincide. And the point B was marked as
shown in the first figure.
3. The difference between the reading and 5’ line ‘X’ was calculated.
4. Now the instrument was focused to another column and point E was marked, as
shown in second figure.
5. The difference D is deducted from point E by using measuring tape and the new point
F was marked on the column. As shown in second figure (Point B and Point F will be
in same height)
6. This process was followed to all the columns.
2.4.3 Automatic laser level
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Figure 2.4.2 Mark 5’ level line in columns
This instrument specially used for marking the level lines in bathrooms, balcony areas
and Interior rooms during the tile works.
It can be helped to get and mark the level lines quickly and accurately.
Figure 2.4.3 Automatic laser level
2.5 BRICK WORK Brick masonry is made of brick units bonded together with mortar. Therefore main two
components of brick masonry are bricks and mortar. In our site 1:5 cement sand mortar was
used and 200x100x75 mm size traditional clay bricks were used in brick masonry.
2.5.1 Quality of bricks While purchasing the bricks, some tests were done to ensure good bricks. Some of
them as follows,
The external appearance should be uniform in color, rectangular section, straight
edges, and free from cracks.
While two bricks are struck against, a metallic tone should be heard.
This test ensures that particles in the bricks are well bonded and free from major
cracks going through the body of the bricks.
Low water absorption.
The brick is laid on firm ground and another brick is dropped from above four feet on
to the form. The laid brick should not brake in two pieces after impact. This ensures
that brick has sufficient crushing strength and that brick is unlikely to fall while
handling during brick lying.
Internal appearance should free from cavities and uniform texture.
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FIGURE 2.5.1 Good quality bricks
2.5.2 Classification of wallsIn our site, 2 types of walls were constructed,
1. Load bearing walls: Normally thickness of the load bearing walls is 225mm (9”) or
more. All of exterior walls are this type of walls
2. Non-load bearing walls: Generally the thickness of these walls is 112.5mm (41/2”).
Used as partition walls.
2.5.3 Setting out for brickwork Using the plumb slabs were checked whether all are in same position & according to
them the brickwork was adjusted. Before constructing the brick work the wall markings were
provided referring the Architectural drawing of that floor. Marked the lines, measuring the
distances from the grid off lines. At the same time 200mm off line of the wall also marked
both side of the wall to facilitate the plastering works in future.
2.5.4 Procedure of brick laying1. First of all the rendered surface were cleaned and wetted well and cement grout applied
on the floor which place brick laying also applied on the side surface of the column for
good bonding between mortar and concrete surface.
2. All the bricks to be used in construction are thoroughly soaked in water so that they do
not absorb the water of the mortar.
3. Mortar was spread on the top of the foundations course, over an area to be covered by
the edge of the wall. The depth of spread of mortar may be about 1.5cm.
4. The corner of the wall was constructed first. For that, one brick was laid first at the
corner and pressed with hammer or trowel hand so that the thickness of bed-joint
remains only about 1 cm. Similarly another corner of brick was laid.
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5. The level and the alignment were checked by using line level rule. If the brick is not in
level, they are pressed gently further. Similarly, the placement of the edge of the bricks
were checked. (By offset marked in the setting out).
6. After then other stretcher and header brick layer were alternatively laid up to 5 feet at a
time to avoid recline of wall. Here the plumb as well as alignment should be thoroughly
checked.
2.5.5 Types of brick bonds In our site two types of bonds were used
1. Stretcher bond
In such type of bond all the bricks are laid with their lengths in the longitudinal of the
wall. This bond is only useful for half thick partition walls.
Figure 2.5.2 Stretcher bond wall
2. English bond
In this type of bond alternate courses of stretchers and headers are laid. This type of
bond is very commonly used in all type of construction.
Normally in our site English bond was used for 9” brick walls and Stretcher Bond for ½
Brick walls.
Figure 2.5.3 English bond wall
2.5.6 Supervision of brickworkThe following points should be kept in mind while supervising brick masonry.
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The bricks should be soaked in water before use for a period for the water to just
penetrate the whole depth of the bricks. This period of soaking may be easily found at
site by a field test in which bricks are soaked in water for different periods and then
broken to find the extent of water penetration.
The bricks should be properly laid on their beds. The bricks should be lightly pressed
into the bed mortar so that uniform joint thickness is obtained.
The brick work should be perfectly level and truly plumb.
Use of brick bats should be minimum.
The place where the brick touch concrete frame (super structure) put 0.5” thickness
regiform layer for keep the space between the concrete beam and brick wall for avoid
the cracks in the wall due to thermal movement of concrete structures.
2.5.7 Placement of lintels Main purpose of the lintels to be placed at opening for windows & doors is to bear the
load transferring from the upper part of the wall. Otherwise, that load will affect to the frame.
Figure 2.5.4 Lintel for openings Figure 2.5.5 Lintel between the bricklayers
Also in our site lintels were placed horizontally between the bricklayers at given level 4ft to
avoid the continuity of the crack in the wall due to settlement of structure and thermal
movement of RC structures.
Also stud columns were provided between the walls in certain distances especially for
balcony walls.
Lintel placement can be done in two methods,
1. In situ method
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2. Pre cast method
In our site, mostly in situ method was used. Some places precast method was used. At the
beginning of the form work was done with reference to the given lintel level. Structural 1000
off line was used to get the correct level as site. After fixing reinforcement, it was concreted.
Grade 25 concrete was used for concreting purpose.
2.5.8 Problems and experiences were encountered Sizes of bricks are different. That was hard to construct the brick wall with design
thickness. As well as, it is very difficult to align the wall and the mortar has to be
wasted in the plastering. When select the bricks must considered the sizes.
Before using any bricks for any construction work those should be soaked into the
water. Because if those are too dry they will absorb the water from the mortar and
then the water content of on the mortar will reduce and then we could not be able to
get proper bond between the blocks or bricks. But the workers rarely do according to
our guidance.
Other thing is, when constructing a wall; some person use in straight edge to align the
wall. But it is wrong. It should be used a string of every time. Otherwise it’s very
difficult to align the wall correctly.
2.6 PLASTERING WORK The function of plastering is protection of wall and the appearance of the building. In
our site cement plaster was used. Usually thickness of plastering is 15mm.
Principal purposes of plastering
To provide a true, even, smooth and finished surface to the work and improve the
appearance
To protect the surface from harmful effects of the atmospheric influences.
To enclose the unsound and porous materials.
To cover the defective workmanship.
To provide a suitable color washing easily.
2.6.1 Preparation of mortar
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The mortar or plaster was made by working together a mixture of building material,
which are cement, fine aggregates (usually sand) and water. In our site, Ordinary Portland
Cement (OPC) was used for preparing the mortar. Sand normally forms the greatest
proportion of the constituents of a plaster. Fine sand was often recommended for plastering
and it was graded by a proper sieve (No.4 Sieve according to BS standard). Used sand were
clean, sharp and free from deleterious matters. Normal tap water was used to add.
Mixed proportion of plaster used in our site.
1. Internal plaster
Soffit, columns, beams, concrete walls - 1:3
Brick walls - 1:5
2. External plaster
All walls - 1:5
2.6.2 Procedure of plastering the wallPreparing the level gauges
1. First wall area thoroughly cleaned by water from dust and other foreign matters.
2. When plastering the newly erected walls and the existing walls the thicknesses
sometimes were varied by small amount. It was very difficult to make corners
perpendicular to each wall. So to overcome this first us drawn two strings on the
floor crossing each and tied up. Then using the Pythagoras theory they were
adjusted perpendicular to each. This lines also referred as off lines.
3. Then using a measuring tape mortar spots were kept on the bottom of the wall in
one meter intervals. Then using plum bob spots were kept on the top of the wall.
4. Way of transferring the bottom spot level to the top spot. Then strips of plaster
were made joining the heights of marked spot and the mid is filled with mortar.
Steps to plastering the wall
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Figure 2.6.1 Schematic diagram for preparation of level gauges
1. First, Mortar was thrashed by using steel trowel on the wall in order to get a good
bond with the wall preventing air gaps inside.
2. Then the surface was levelled by a straight edge.
3. For the rough finish, a wooden float finishes the plaster surface. If a smooth finish
is required, a small amount of water was applied by a coir brush and finish with a
metal float or a trowel.
4. After 24 hours plaster should be cured with water.
Following points to be considered when plastering,
The normal thickness of plaster is 15mm. It will depend on the perpendicularity of the
wall. Sometimes the thickness of the plaster is more than 25mm; plaster was applied
in two coats. The first coat is applied as described above with the only difference that
the plastered surface is not leveled. When the first coat is set the finishing coat was
applied over it and got the final finish. Sometimes cement powder used for this
process.
Before plastering we have to fix a chicken mesh at the joints of beams and walls. It
was fixed using concrete nails as shown in the Figure. Plastering process can be
commenced after fixing the chicken mesh.
Figure 2.6.2 Chicken mesh fixed in joint
When plastering the walls 450mm wide strip was kept from the bottom of the wall
plastering half of the thickness of the plaster for waterproofing. Also shower area
walls were plastered half of the plaster thickness for waterproofing.
To lay the plumbing lines and electrical conduits, straits were cut out on the walls
according to the diameters of pipes where necessary, relevant to the plan.
Walls are wetted before plastering with water in order to prevent absorbing water by
the wall from nearly laid plaster mixture. Otherwise, the applied plaster, which would
get dry quickly, so it would fail to set in the wall or come out or crack.
Chip off the wall surface where exposing out of the level points.
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If there is a place where too much filling is needed, first coat is applied.
Small cavities are there on the surfaces of the semi rough internal plaster surface. It
may help to apply finishing filler putty and make good bond.
Too much trowel ling way cause to expose grout. Plaster should cure continuously
until it reaches required strength.
When plastering over a concrete surface, the surface is wire brushed and well cleaned.
The places where there is a tendency to crack, a 6mm groove is placed so that the
crack can propagate through it. It will not damage to appearance.
Figure 2.6.3 Beam plastering work
2.6.3 Defects in plastering In our site, following defects sometimes were noticed in plastered wall, so we used
various treatment methods for that defects.
1. Non-structural cracks
They usually the result of over trowelling the mortar or excessive amount of dusts or
contaminates presents in sand and result of moisture loss after the plaster hardened. These
types of cracks can be filled with filler and painted over.
2. Structural Cracks
Some cracks visible in the plaster may result from cracking the wall. The cracks may
be thin hair or wide open cracks. This can be caused by differential movement of the
foundations, moisture expansion of masonry units or thermal movement of concrete
structures. For these type of cracks, the method was used change cracks into movement
joints. To avoid this for internal walls V grooves left out in plastering along the wall & the
RCC joint.
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Figure 2.6.4 Structural crack
3. Debonding
Debonding of plaster is often noticed as a hollow sound when the surface is tapped. It
is the generally result of the inadequate preparation of the wall. Debonding areas should be
removed and replaced by new plaster. In our site we spread over “L-Bond” chemical to the
patch area and plastered it.
Figure 2.6.5 Treatment for debonding
2.6.4 Problems and experiences were encountered Before plastering wall has to wet by the water. Because the bricks will absorb the
water which is in the mortar. It will reduce the water that need to hydrate the cement
and make bonding with the surface. But in our site workers poorly wet the wall or not.
Sometime the will is not vertical since we have to keep a thick plastering tag. In these
cases, sometimes the wall have to be plastered in two steps.
When the plastering of beams, columns, windows and doorframe we should be
checked the size and perpendicular of edges also we hired high experienced work
force for these types of tasks to avoid the mistakes.
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2.7 WATER PROOFING Water proofing is very important thing in the multi storied building. Where moisture is
present, there is always the danger of damage not only the concrete but to the seal as interior
finish.
In our site, some places which waterproofing work was carried out toilet drops, water sump,
balconies, roof, pit etc.
DAVCO K11 FLEX chemical was used for water proofing work. This method is called liquid
membrane water proofing.
2.7.1 Procedure of water proofing
1. Substrate was thoroughly cleaned from any protrusion or substances that may damage
the membrane.
2. Surfaces were ensured free from dirty, dust grease, oil, wax, curing compounds and
any other loose contaminating materials.
3. Surface irregularities such as blowhole, honeycombs, edges and angles were filled with
cement mortar mix or construction grout for prepare the cleaned surface.
4. DAVCO K11 FLEX liquid was put into a clean mixing container. DAVCO K11 FLEX
powder was added gradually until a lump free plastic consistency was achieved. No
addition of water is allowed. It’s recommended that mechanical mixing 400- 500 rpm
should be used for proper dispersion of the components.
5. Surface was wetted with clean water
6. Mixed material was applied onto the prepared surface using a block brush, squeegee or
roller in a stiffing action.
7. 1-2 coats were applied depending on site condition, specifications and film thickness
required If a 2nd coat was applied, the 1st coat must be left dry tacky approximately 1-3
hours. If over coating was done more than 24 hours after applying the previous coat, or
previous coat has already dried out, the surface must be prevented again before further
application.
8. After they were dried off pool of water was made on the floor and kept for 3 days to
find out whether there are any leakages.
9. After the water dried off sewerage pipes were placed and fixed.
10. Joints between sewerage pipes and wall were filled with construction grout to ensure
the free from leakages.
11. Then DAVCO K11 FLEX chemical was applied on those joints.
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12. After mass concrete was applied.
13. Again DAVCO K11 FLEX chemical was applied on the concrete floor and same
procedure was continued as mentioned earlier
14. After that Barralastic was applied for both floor and wall (1feet height)
15. Next fiber net was placed around corners of walls and near gullies.
16. Again Barralastic coat was applied on it.
17. Also DAVCO K11 FLEX chemical was applied in the wall height of 450mm in
bathroom area for protect from shower water.
Figure 2.7.1 Schematic diagram of chemical water proofing
Figure 2.7.2 Water proofing in bathroom area
2.8 TILING WORK Tilling is a one of the major work of modern world in finishing activity. It’s used for
decorating work of wall areas and floor area. Also it can be easily maintenance than plastered
wall area and tilling provided sound appearance than plastered area.
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Selection of tiles for a project has to be given due consideration taking in to account the
usage, location, interior decor, client requirements etc.
Tiling work was done in 4 steps.
2.8.1. Tile bed layingThe purpose of the tile bed laying is,
To provide required level surface
To get good bonding surface for tiling
To covering treatment like waterproofing and thermal insulation
Steps to laying the tile bed
1. The floor should be rough, free from laitance, dust, coating, paints, loosely bound
particles and other foreign matters.
2. They were removed by chipping (chipping with a chipping chisel). Next, floor surface
was roughened by chipping by electrical hammer.
3. Then surface was washed and allowed to dry sometimes.
4. After, finishing floor level was determined from architectural drawings or structural
drawings.
5. Cover pegs were fixed directly with level instrument considering thickness of the tile
normally 10 mm and the thickness of the cement grout as 3mm. From the finishing
level, we deducted the tile the tile thickness and the grouted thickness. Normally we
considered 3 mm for grout thickness, but that is changing to every tillers. That, the
bed levels of lines were marked in walls.
6. The levels were some places maintained same level, some places for bathrooms,
balconies, and terrace and where slope is necessary to discharge water or other
purposes that was given in the drawing.
7. Cement mortar 1:5 was used preparing tile bed laying. All materials were thoroughly
mixed; the quantity of water was added for getting the minimum necessary to give
sufficient workability for spreading & leveling the mortar. Before spreading the
cement mortar cement grout was applied on the floor for get the good bonding.
2.8.2. Setting out for tiling (Tile line marking)Tile marking is given according to the tile drawing.
1. Floor tile lines marking
During the floor tile line marking following things were considered,
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The type and size of the tile.
Specified groove thickness.
Existing floor dimension.
First two perpendicular reference line are drawn using theodolite on the bed and as
fulfilled architectural requirement and as tile size and groove thickness are known, we can
calculate the sizes of the tile pieces get near boundaries. If they are practicable (should be
larger than 100mm) as above requirements are fulfilled, above lines are fixed as it is. In case
of being not practicable, above two line are adjusted and fix new line parallel to the previous.
Following points were considered during the tile line setting out,
1. Ensure a larger piece of tile at each end, giving a more attractive effect.
Figure 2.8.1 Floor tile setting out
2. If the side walls are out of square, the change in cut tile width is less noticeable. Set
full tiles in a squared rectangle in the center of the floor, with cut tiles all around the
edges.
3. Start with full tiles from a very visible line: e.g. a wide doorway, or where the tiles
give way to carpet.
Figure 2.8.2 Consider the maximum full tiles and less wastages
2. Wall tile lines marking
First of all walls should be checked weather plumb or not and it should be fixed before
tile line marking.
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Wall tile marking also same as floor tile marking. But here we use center plumb bob and sprit
level instrument to draw perpendicular line on each wall. The horizontal line is drawn as a
level line common to all inside walls and each vertical line for each wall is drawn
considering. After batten board was temporarily placed horizontally from the floor tile level
remain the one wall tile space.
Also following points were considered marking the tile line,
Vertical lines should draw as plumbing points coincide on the tile groove as possible
The boundary tile piece should be checked weather practicable.
Wastage should be minimized.
The thickness of 2or 3mm.
Tile is fixed to wall normally groove size is 2mm.
Also above the floor tile laying points were considered.
Figure 2.8.3 Wall tile line setting out
2.8.3. Tile laying 1. Floor tiling
First, tile mortar was prepared with sufficient amount of water to like as creamy
state. In our site we used “Lanka Tile Adhesive”
First the tile bed was cleaned and wetted.
Tiles should be immersed in water at least half and hours to avoid absorption of
water from mortar.
After that strings were stretched along main perpendicular lines and fixed using
concrete nail, cement grout were put and spread by using notch trowel for full of
one raw of tile place along one line.
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Figure 2.8.4 Floor tiles laying
Then start in intersecting lines and continued the tiling with insert the spacer
between two tiles spacer mainly use for maintain the equal space. For the floor
tiles 3mm space were kept.
By the rubber hammer and the sprit level tiles top levels keep accurately.
After passing 24 hours suitable tile grout is used.
Tile cutter and grinder was used to cut the tiles in appropriate sizes.
2. Skirting tile laying
In floor, tilling skirting is very import. There are two method of skirting one method is
¼” exposed from wall and other method is same level in wall. Normally use ¾`` thick
4``high tiles were skirting with `v` grove in 1:3 cement: sand and finished smooth colour
cement float.
Figure 2.8.5 Skirting tiles laying
3. Wall tiling
Wall tiling is quite difficult than floor tiling, they should be well dampened before
laying and walls should be wetted well.
Then cement grout was put on the back side of the tiles and spread neatly then the tiles were
laid. Here also we used the spacer for maintain the equal space. In these two types of tiling
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for maintain the level we use straight edges. But in wall tiling, before use edge we use plumb
bob or sprit level for few rows completion.
2.8.4. Tile grouting Tile grouting is filing tile grooves neatly with tile grout. Tile grout is waterproofing
cement of variety of colours.
1. Before tile grouting is commenced tile groves should be cleaned and free from cement
grout and dust. Using scraper and compressor should clean them.
2. Tile grouting is commenced only after two days since tiling work is completed.
3. Add clean water to grout powder and mix well to get a stiff trowel able.
4. Consistency. Do not make mix soupy as shrinkage cracks may ensure.
5. Keep the mix for 10 minutes and re-mix before use.
6. With the use of brush or sponge apply grout into and around all edges of the tile joints
and compress the grout firmly into the gap.
Remove surplus grout from the tile surface without delay using a moist cloth or sponge and
smooth out the joints using a ground shaped piece of wood. (Some places we used wire for
removes the grout).
2.8.5 Checking the quality of tiling work Groves should be even and straight.
Each tile should be in same level.
There should not be any damaged tile.
Wastage should be minimized.
There should be proper arrangement and layout.
Wall tiles should be plumbed.
Edges should be straight.
2.8.6 Tools used for tiling works 1. Floats
A float is a tool used for spreading the mortar of the surface of the concrete slab.
2. Floating Ruler
This tool has marking which are used to check the level of mortar
3. Tile Cutter
This hand tool is used to cut the tile manually wherever odd size gaps are required to
be fixed.
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4. Tile cutting Plier
Used to cutting the irregular shapes, holes in tile
5. Tile cutting Machine
This tool is electrically operated for cutting the tiles.
6. Notch Trowel
This tool is used to spread the tile adhesive mortar over the tile bed or tile.
7. Masonry Trowel
This tool is used for spread the cement mortar over the concrete slab.
8. Sprit Level
For used check the horizontal and vertical level of tile laying.
Figure 2.8.6 Tools for tiling work
2.8.7 Problems and experiences were encountered The mortar must be spread over the area according to the given level stubs. Thickness
of the spread ding should be normally 20 mm.
but if the bedding thickness is greater than 40 mm a chip concrete is laid before the
mortar bedding to reduce the thickness of it.
During the skirting tiles were installing process, in some places in plastering of wall
was not even at those places skirting tiles were not in straight line. In this case smaller
adjustment in gap between skirting tile and wall was done for entire wall to get
straight line edge.
In some bathrooms (especially 3rd floor bathroom) wall tile lines was not met parallel
to floor tile lines due to dimensions is varied with every floor tiles. In this case floor
tiles laying pattern was changed to diagonal laying pattern.
Floor tiles were selected by clients which tiles thickness vary from 10mm to 15mm
due to this, finishing floor level was changed to room and hall area. So avoid the
problems tile bed thickness was changed according to the tile thickness.
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Some laid tiles were broken or damaged by workers careless. That situations that tiles
should be replaced but in this process will be affect the other adjacent tiles
2.9 PAINTING AND FINISHING WORKS The main purpose of paint is to provide a decorative finish to obtain clean, colourful and
pleasing surfaces. Such surfaces are hygienically good, presence healthy surrounding to live
in. The outside of walls need painting for protects the surface from environmental factors.
Surfaces are usually painted with several coats of paints, each coat performing a specific
function. A series of coats of paint is known as “painting system”.
A typical paint system is comprise of:
Primer – a primer is the first coat of paint applied to an unpainted surface and its
function is to adhere to the surface and provide adhesion to subsequent coats of paint.
In our site we used skim coat as a primer.
Under coats – we used wall putty as under coat to fill up cracks, dents and holes on
surface.
Finishing coat
2.9.1 Painting for interior wallsProcedure
1. Firstly, the plastered surface was cleaned with scraper so it will make an even surface.
2. The surface should be cured thoroughly with water before applying skim coat.
3. Then one coat of skim coat was applied with the help of steel float.
4. After that skim coat was cured for 3 days.
5. Then No.180 Sandpaper was used for smoothing the wall surface under light pressure.
6. Then again checked the smoothness of the wall if any cavities and damages in the
wall surface, leveling compound (putty) was used for leveling the wall surface.
7. After then final sand cutting process was done. In this process straightness and
smoothness of edges of columns and beams, windows edges, corners of wall and
skirting tile areas were checked and fixed it.
8. After then liquid filler was applied by roller on the wall surface.
9. After drying the filler, first coat of paint was applied as per client’s requirements (E.g.
Colour, Area of the wall).
10. Finally finishing coat of paint was applied.
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Figure 2.9.1 Putty work and Sand cutting process
2.9.2 Painting for exterior wallsProcedure
1. Firstly, the plastered surface was cleaned with scraper so it will make an even surface.
If any patches and damages is remains it should be finished before starting the work
2. Then first coat of weather shield primer was applied for protect the exterior walls from
the weather conditions.
3. Then second coat of weather shield primer was applied and kept for drying.
4. After fist coat of paint was applied and kept for drying.
5. Finally, finishing coat of paint was applied and kept for drying.
Figure 2.9.2 Weather shield applied in exterior wall
2.9.3 Finishing method of timber doors and framesProcedure
1. Firstly sand cutting process was done for get smooth surface. To get very smooth
finishing for we used machine mounted sandpaper.
2. If any damages, cavities and holes were remained those filled with special timber dust
mixed gum and again sand cutting was done.
3. Then primer was applied for protect the timber from insects and termites.
4. Finally, Enamel vanish paint was sprayed with the help of air compressed sprayer to
get even surface finish.
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2.10 SCAFFOLDINGS The scaffolding is a temporary structure from which people may get access to a place
of work to carryout building operations safely. Also provide the space for handling materials.
The system is raised gradually as the structure is raised level-by-level. The system used in our
site is a putlog scaffolding system mounted on a thick concrete layer by spiking the base plate
in to the concrete. But as a safety measure scaffold keepers are used supported by the slab.
Scaffolding will be required for
Wall construction.
Preparing or removing formwork.
Plastering of wall.
Painting of wall.
Construction of ceiling and roof work.
2.10.2 Types of scaffoldingsThere are two types of scaffolding used in this site,
1. Putlog scaffolding
This form of scaffolding consists of a single row of an upright or standards set away
from the wall at a distance, which will accommodate the required width of the working
platform.
2. Independent scaffolding
Independent scaffolding has two rows of standards, which are tied by cross members
called transom. This form of scaffolding not relies on the building for support and is therefore
suitable for used in conjunction with frame structure. Mostly these type of scaffoldings used
for temporary works as like brickwork, plastering work, concrete work…etc.
Figure 2.10.1 Elevations of the Scaffolding
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BASE
NUT
ROTATE
4 X 8 FLY WOOD
FORK HEAD
CROSS BRACE
FRONT ELEVATION SIDE ELEVATION
Then two scaffolding sets were connected by four cross braces two braces for each side. Then
four fork heads were inserted to the tubular standards, which have rotate nut for adjustments.
On top of the fork heads rafters were placed and on top of the rafters, plywood were placed.
This was the basic procedure used at the site for assembling scaffolding system.
Joint pins are used when the frame is stacked on the top of the other.
Arm locks are used to fasten upper frames to the lowers. The completion of
assembling can be checked easily by observing arm locks placed in their respective
positions.
Horizontal frame or catwalk is to be placed as the last operation.
All tie should be ate to anchor at every 4 spans in horizontal direction and every 3
spans in vertical direction.
2.10.3 Components of a typical scaffolding systemThere are many components use for the complete the scaffolding.
1. Formwork frame- this is the main part of the formwork. In the construction industry
various size framers are used but generally we use 1219 mm breathe 1700 mm height
frames and 914 mm height framers.
2. Cross Brace – This is use to fix two frames to gather.
3. Catwalk – this steel plate use as the platform on top of the frame to work easily.
4. T base - this is used to support the timber frame which is fixed to the bottom of the
formwork frame.
5. Jack base – this is same as the T base and this can be adjusted manually.
6. Stair – this is use as temporary staircase to climb to the top of the formwork easily.
7. U Base – this is used to support the timber frame which is fixed to the top of the
formwork frame.
8. Pipe Joints – this is use to joint two framers.
9. Flat form– Use for standing easily to workmen , kept the material and tools.
10. GI pipe– In scaffolding GI pipes are used for, Locking two sets of scaffolding
from preventing of movement. As a support of the scaffolding used for making a
handrail.
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2.11 SITE PROBLEMS AND IDEAS
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Figure 2.10.2 Components of scaffolding
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