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ACKNOWLEDGMENTS
First of all, I would like to praise almighty God, who has been there for me all the times
when I was in need of him. Next to this I would like to thank my company supervisor,
Assistant Resident Engineer Ato Tekeste for his kindly advice and supervising
throughout the internship program.
My deep appreciation and many thanks go to my mentor Ato Tsehaye for his open
handed support and for directing me to focus on important issues. Without his guidance
and valuable supervision, i would not have this knowledge.
I would also need to thank the Material Engineer Ato Muluneh and the each staff of
Materials laboratory for their unreserved support and co-operation while conducting the
laboratory tests. Besides, I cannot step without mentioning that, honorable thanks to Ato
Kaleab Mame, who has helping me by answering all of my question and his friendly
advice.
I am deeply indebted and thankful to my team mates Abey and Setargew; they were a
constant source of encouragement. They also helped me in sharing knowledge and helped
me during execution of laboratory tests.
Finally I want to pass grateful acknowledgement for Laboratory Technicians, Work
Inspectors, and laboratory assistant, and for those person I have received valuable
assistance either in word or in material, those who have been beside me in the internship
program.
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EXECUTIVE SUMMERY
This report is an outcome of the exercise I conducted during my internship period at
Gondar-Debark road upgrading project. This was an opportunity for me to put in practice
the theoretical knowledge I had gathered during my three years of study at Bahir Dar
University.
The purpose of this report is to put in writing the work experience I had performed and
the learning attained from performing specific tasks while working in a professional
environment.
In the first part of my report, I briefly described the back ground of my internship hosting
company, including the history and objectives of the company, its main products and
services, the overall organization and work flow. I also explained the background of the
project like its contract, alignment terrain, location, climate and typical cross sections.
The second part of my report briefly explains the overall internship experience I have
gained during my practical periods. I started by telling how I get into the company, in
executing. I also explained clearly what the general work flow in our site looks like.
The procedures I have used while performing my tasks, are also included in this part of
the report. I tried to explain all of my experience during this time, starting from the
earthwork like cutting and construction of embankment then I explained the material and
the steps we used during construction of pavement layers like sub-grade, sub-base, base
course, prime coat, tack coat and surface layer. After pavement layers I described about
the structures which is very use full for a goodly functioning highway like side ditches,
culverts, and retaining walls. Next to this I briefly described the objectives, main
principle and calculation of the laboratory tests I conducted during my internship time.
While I writing all the report I insert some tables and pictures which can express the
works easily and shortly.
The challenges I have faced during my internship period, both site challenges and
personal challenges are covered in this report.
The third part of my report briefly explains about the overall benefits and experience I
gained from my internship in terms of improving my practical skills, interpersonal
communication skills, team playing skills, leadership skills, upgrading my theoretical
knowledge and work ethics.
Finally, I covered my conclusions and recommendations for my hosting company.
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Table of contents
1. BACKGROUND OF THE INTERNSHIP HOSTING COMPANY .................................................... 1
1.1. Brief History of the Company ....................................................................................................... 1
1.2. The Main Product and Service of the Company ........................................................................... 2
1.3. .......................... 2
1.4. Overall Organization and Work Flow ........................................................................................... 3
1.5. Description of the Project ............................................................................................................. 6
2. OVER ALL INTERNSHIP EXPERIENCE ......................................................................................... 9
2.1. How I get in to the Company ........................................................................................................ 9
2.2. The Section of the Company I have been working ....................................................................... 9
2.3. The work flow in the sections:- .................................................................................................... 9
2.4. The work I have been executing ................................................................................................. 10
2.5. The Meaning and Procedures of the works ................................................................................. 11
2.5.1. Earthwork ............................................................................................................................ 11
2.5.2. Construction of Pavement layers ........................................................................................ 15
2.5.2.1. Sub-Grade ....................................................................... Error! Bookmark not defined.
2.5.2.2. Sub-Base ......................................................................................................................... 15
2.5.2.3. Base course ..................................................................................................................... 17
2.5.2.4. Bituminous Prime Coat ................................................................................................... 18
2.5.2.5. Asphalt Concrete Layer (Surface Course) ...................................................................... 19
2.5.3. Construction of Structures .................................................................................................. 22
2.5.3.1. Drainage structure ........................................................................................................... 22
Side Ditch ........................................................................................................................ 22
Minor Drainage Structures .............................................................................................. 23
Slab culvert ...................................................................................................................... 23
Box Culvert ..................................................................................................................... 23
Pipes culvert .................................................................................................................... 24
2.5.3.2. Retaining wall ................................................................................................................. 24
2.5.4. Laboratory Tests I Have Been Executing .......................................................................... 25
2.5.4.1. Tests on Asphalt (Bitumen) ............................................................................................ 25
Asphalt Penetration Test ................................................................................................. 25
Softening Points of Bitumen ........................................................................................... 26
Ductility Test ................................................................................................................... 27
Cut back distillation test .................................................................................................. 27
2.5.4.2. Tests on Asphalt Mixture ................................................................................................ 28
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Extraction of bitumen and mechanical analysis of extracted aggregate .......................... 28
Maximum Theoretical Specific Gravity of Bituminous Paving Mixture ........................ 29
Asphalt concrete mix resulted by marshal method ......................................................... 30
2.5.4.2. Tests on soil and aggregate ............................................................................................ 30
Atterberg limit test .......................................................................................................... 30
Particle size distribution wet sieve ............................................................................... 31
Aggregate Shape Test...................................................................................................... 32
Specific Gravity of Aggregate ......................................................................................... 33
Absorption Aggregate ..................................................................................................... 33
Los Angeles Abrasion Test (LAA ................................................................................... 33
Aggregate Crushing Value (ACV) .................................................................................. 34
Ten Percent Fines Value (TFV) ...................................................................................... 35
Proctor Compaction Test (Modified Proctor) ................................................................. 35
California Bearing Ratio (CBR) ...................................................................................... 36
2.5.4.3. Tests on the site ............................................................................................................... 37
Density of Soil in Place by Sand-Cone Method ........................................................... 37
Core cut ........................................................................................................................... 38
Application of Bituminous Coat ..................................................................................... 38
2.5.4.4. Tests on concrete ............................................................................................................ 39
Compressive strength test................................................................................................ 39
Mortar test ....................................................................................................................... 40
Slump Test ...................................................................................................................... 40
2.6. The Challenges I faced and the measures I took while performing my Tasks ............................ 41
3. Overall Benefits I got from the internship .......................................................................................... 42
3.1. Improving my Practical skills ..................................................................................................... 42
3.2. Upgrading theoretical knowledge ............................................................................................... 43
3.3. Improving my interpersonal communication skills ..................................................................... 43
3.4. Improving my team playing skills .............................................................................................. 44
3.5. Improving my leadership skills ................................................................................................... 44
3.6. Understanding about work ethics related issues ......................................................................... 45
3.7. Entrepreneurship skills ................................................................................................................ 46
4. CONCLUSION AND RECOMMENDATION .................................................................................. 47
4.1. Conclusion .................................................................................................................................. 47
4.2. Recommendation ........................................................................................................................ 48
5. Reference
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List of Figure
Fig. 1.1 Consultant Office Organizational Chart .
Fig. 1.2 Project Location Map
Fig. 2.1 cut (rock and soil excavation) . 2
Fig. 2.2 construction of embankment
Fig. 2.3 Construction of Base Course
Fig 2.4 Application of prime coat
Fig 2.5 Tack coat 19
Fig. 2.6 Construction of Bituminous Surface Course .. 1
Fig. 2.7 Construction of Side Ditches ..
Fig. 2.8 slab culvert .
Fig. 2.9 box culvert
Fig. 2.10 Pipe Culvert
Fig. 2.11 Construction of Retaining Wall
Fig. 2.12 Execution of Asphalt Penetration Test. 26
Fig. 2.13 Execution of Softening Point Test 26
Fig. 2.14 Execution of Ductility of Bitumen Test . ..
Fig. 2.15 Execution of cut-back distillation test ..
Fig. 2.16 Extraction Equipment ... 29
Fig. 2.17 Vacuum Vessel 29
Fig. 2.18 Marshal Method, for stability and flow
Fig 2.19 Atterberg limit test using Cassagrande Cup Method .. 31
Fig. 2.20 sieve analysis 32
Fig. 2.21 flakiness sieve 32
Fig. 2.22 LAA Test Equipment 34
Fig 2.23 ACV test .. 34
Fig. 2.24 Proctor Compaction Test 36
Fig. 2.25 Execution of CBR Test 37
Fig. 2.26 Execution of Field Density 37
Fig. 2.27 Core Cutter Machine ... .. .38
Fig. 2.28 Measurement of Application Rate ... . 39
Fig. 2.29 Measuring Compressive Strength of Concrete 39
Fig. 2.30 Effect of raining on base course 41
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List of Table
Table 1.1 Terrain classification ...
Table 2.1 cut slope 12
Table 2.2 Inspection and test plan for: embankment, capping layer and sub-grade 15
Table 2.3 Inspection and test plan for: sub base materials 16
Table 2.4 Grading requirements for sub base material
Table 2.5 Inspection and test plan for: base course 17
Table 2.6 Grading requirement of base course material 18
Table 2.7 Inspection and test plan for: Coarse Aggregates (Asphalt concrete).. .. 20
Table 2.8 Gradation Requirement of Asphalt Aggregate 20
Table 2.9 Asphalt Mix Requirement 20
Table 2.10 Temperature of the mix 21
Table 2.11 Inspection and test plan for: Masonry stone 22
Table 2.12 The range at which the volume of distillate must lie 28
Table 2.13 Gradation of Asphalt Aggregate 28
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1. BACKGROUND OF HOSTA GE COMPAN
1.1. BRIEF HISTORY OF THE COMPANY
Foundation
The origins of J. Burrow Limited dates back to 1963, when an entrepreneurial Civil Engineer by
the name of John Burrow established an Engineering Consulting practice in Lusaka, Zambia.
The firm then known as John Burrow & Partners, rapidly expanded to become a leading provider
of Civil and Structural Engineering design and construction services in the East and Southern
African regions. When the development of primary infrastructure services were being developed
in these areas, John Burrow & Partners became one of the leading engineering service providers
with an enviable track record in providing a successful service.
Expansion
By the mid-eighties, from its African roots the company had expanded to a sizable operation
with an unblemished track record and reputation for delivering reliable, relevant and high quality
consulting services. The company was represented in over a dozen countries on the African
Continent & the United Kingdom and from this base was executing assignments in countries as
far afield as Thailand, Malaysia and China. In order to improve its operational efficiency and
management effectiveness a decision was taken to form two separate entities for the United
Kingdom & African based operations. This gave rise to John Burrow & Partners Overseas which
held all the African business units.
During the following two decades John Burrow & Partners Overseas went through three
ownership and name changes. The company also implemented a policy of local capacity building
and empowerment of local professionals by grouping the businesses into stand-alone enterprises
in Zambia, Botswana, Zimbabwe and Swaziland. The local professionals in each of these
subsidiary companies were then invited to become majority shareholders, thus creating leading
consulting engineering firms in each of these four countries.
The Present
From the 1st January 2006 the company became known as J Burrow Limited and has
operational bases in South Africa, Zambia, Swaziland & Zimbabwe with project offices in
Uganda, Tanzania, Mozambique, Sierra Leone and Zanzibar.
J. Burrow Limited now has significant experience at delivering Engineering and Project
Management services for the development of infrastructure in Africa. The Company and its
professionals are thoroughly familiar with the requirements of Multilateral development finance
agencies like the World Bank, European Union and the African Development Bank; and
Bilateral institutions like the United States Agency for Aid and Development, Japan International
Corporation Agency and the Kuwaiti Fund for Economic Development.
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To support integrated project development, J. Burrow assembled multidisciplinary teams of
professionals comprising engineers, construction and project management specialists,
environmental scientists, planners, financial analysts, business modelers, project finance
specialists, lawyers and insurance experts.
Some works (products or service) of the company:-
A long distance bulk water transfer project, Botswana
Construction of 360 km (1.1 to 1.4 m diameter) pipeline to transport water from a Dam at
Letsebogo River in Northern Botswana to the towns and cities in the populated Eastern
corridor of the country, including the capital city Gaborone.
Upgrading a gravel road to bitumen paved standard, Tanzania
The Manyoni - Singida section (122 km) on the Central Transport Corridor was upgraded
to bitumen standard utilizing a design and build contract model.
Road Rehabilitation, Sierra Leone
Rehabilitation of the 164 km long Masiaka-Bo Highway.
1.2. The Main Product and Service of the Company
J. Burrow Limited provides professional services for the development of infrastructure which
include:
Intercity motorways, trunk roads or urban streets
Systems for the abstraction, treatment and supply of water; or solutions for collecting,
treating and reusing or disposal of wastewater.
Plant or network for the generation, transmission and distribution of power.
1.3. ct
or Service
As I have mentioned above, on the history, the company can provide different kinds of
consultation (product or service) on civil infrastructure. These are the main products of this
company, but as I am working on highway construction I will only describe the end users of this
highway construction and the advantages they have gained from it.
It is known that highway is public service which is constructed to help peoples rather than to
make profits. And as a public service all the peoples along the road and our country Ethiopia
are also the main users of the product of the company (which in this case is Highway). Some of
the advantages that the peoples along the highway gained are getting fast and easy access to
referral hospitals and preparatory schools which are not available in small towns, safe journey
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The federal democratic republic of Ethiopia represented by the Ethiopian road authority (ERA)
endeavors to upgrade the Gondar-Debark road in order to meet the requirements of the increased
socio-economic activities along the project road corridor. These upgrading and construction of
environment like:-
Increase the national integrity of peoples of the country.
Promotion and enhancement of social and economic development along the project road
corridor;
Reduced vehicle operating cost ( e.g. fuel consumption, maintenance cost);
Increase road safety;
Reduced travel time and greater comfort to motorist;
Reduced noise and air pollution as well as dust nuisance.
Basically (Ethiopian Road Authority) ERA and other governmental and nongovernmental
organizations are the customers of this construction company.
1.4. Overall Organization and Work Flow
Resident engineer:- the resident engineer is accountable to the engineer (j. Burrow company).
matters related to construction of
the works like liaise with the regional officials and other institutions for right-of-way issues and
others. He has a responsibility to monitor progress of the works, monitor contractor's equipment
& manpower availability
the contractor, the consultant and era's representatives, perform periodic inspection and make all
the necessary changes in design, review and approve quantities and payment certificate.
Assistant resident engineer:- Assistant Resident Engineer is accountable to Resident Engineer.
He is the one who assist the Resident Engineer in all aspects and perform all the duties of the
Resident Engineer during his absence and follow up the activiti
actively engage in the design review process and makes all the necessary changes. He has a
responsibility to inspect the fieldwork daily and recommend solutions of problems to the
Resident Engineer and perform survey of the road geometry and keep continuous monitoring of
all changes regarding road geometry, roadside furniture and other facilities. He checks drawings,
plans, calculations, measurements and payment certificates prepared by the Contractor.
Pavement/material engineer:- Material Engineer is accountable to Resident Engineer. He is the
one who directly concerned with construction material. He assists the Resident Engineer in
approving or rejecting construction materials, also locate possible sources of construction
materials. And visit the site to solve major problems concerning subsurface conditions,
construction materials and pavement. He controls and assists the laboratory technician in
devising appropriate sampling and testing programs.
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Geotechnical engineer:- Geotechnical Engineer is accountable to Resident Engineer. And
perform the necessary reviews on design documents pertaining to geotechnical investigation and
associated design. He inspects at periodic intervals the quality of the works, also visit the site to
solve major problems.
Highway engineer:- Highway Engineer is accountable to Resident Engineer. He makes the
necessary reviews on design, drawings and quantities to make the design changes to suit site
conditions and inspects the site at periodic interval to solve outstanding problems regarding the
design of the roadway, minor structures and other facilities.
Structural engineer:- Structural Engineer is accountable to Resident Engineer. He inspects the
works at periodic intervals to solve major problems concerning major and minor drainage
structures. And he inspects the structures for the proper interpretation of design drawings and set
inspection and testing requirements to be used by the Structural Inspector.
Claim expert:- He is accountable to Resident Engineer. And assist the Resident Engineer in all
contractual matters and interpretation of the tender document. He provide the necessary services
in examining Claims, assist during negotiations, and make the necessary cost break down
analysis for new items as well as escalated items.
Quantity surveyor:- Quantity Surveyor is accountable to Assistant Resident Engineer. He has a
responsibility to monitor the quantities of all pay items routinely and as requested by the
Contractor and make measurements of all works done by the Contractor as appropriate.
Senior surveyor:- Senior Surveyor is accountable to Assistant Resident Engineer. He has a
regarding the lines, levels and sections of finished works.
Draftsperson:- Draftsperson participates in the preparation of reviewed drawings, review all
working drawings received from the Contractor. Generally perform any drafting works needed
by the Consultant staffs for the use in the project
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CONSULTANT OFFICE ORGANIZATIONAL CHART
Fig. 1.1 Consultant Office Organizational Chart
The Engineer J.BURROW
Project Director
Resident Engineer
Sociologist
Head Office Support
Claim Expert
Highway Engineer
Structural Engineer
Geotechnical Engineer
Assistant Resident Engineer
Secretary
Quantity Surveyor Pavement/Material
Engineer
Work Inspector Senior Surveyor Lab. Technician
Surveyor
Draftsperson
Lab. Assistant
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1.5. Description of the Project
The Gondar -Debark road is located in the North part of Ethiopia which is the major links road of
the Amhara and Tigray regional states which are at border with Sudan and has approximately
99.90Km long.
The project is an upgrading of the existing gravel road to an asphalt road standard which was
built years ago as Telford base and penetration macadam during the period of 1936/40 and being
deteriorated for several periods that haltered the socio-economic condition. The road has a
prominent important as it located along the most scenic area of tourism to simian mountain in
addition to the various tourist location from the tourist town of Gondar to Debark.
The contract project was awarded to SINOHYDRO CORPORATION LTD; contractor and
construction supervision to J. BURROW South Africa LTD in association with OMEGA
Consulting Engineers, consultant. And accordingly the construction of project contract was
commenced on April 1st 2009. Originally the preliminary study of review of feasibility study,
Environmental Impact Assessment (EIA), Review of Detailed Engineering Design and Tender
documents was made by the KOCKS CONSULT GERMANY in JV with Metaferia Consulting
Engineers under the contract made on November 29th 2005. The above preliminary design as
well as construction of the project was made by the contract agreement with ERA (Ethiopian
Road Authority) under the financial grant of World Bank. The accepted contract amount of
money is 744,612,013.580 ETB.
The road was now planned to upgrade the road to an asphalt road standards and the road is to be
upgraded to 7m carriageway with 1.5m hard shoulders. The works include earthwork,
construction of pavement with bituminous AC surface, repair/rehabilitation of existing bridges,
construction of a new bridge, rehabilitation of minor drainage structures.
The improvement/upgrading include the provision of a 2*3.50m wide carriage way paved with
5cm asphalt concrete and gravel shoulders of 1.50m width in general and near major towns the
carriage way is widened to 2*3.50m + 2*2.50m.
In line with the classification of the road network in Ethiopia and traffic volume (AADT) the
standard and a traffic class of T6 (km0+730 to km4+500) and T5 (km4+500 to km99+900)
according to ERA Geometric Design Manual.
The road passes through number villages of Weleka, Shembekit, Ambagergioes, Gedebiye,
Dabat, and Woken.
Most of the existing major structures, bridges, culverts between Gondar and Debark are arch
structures of stone masonry type, other types are concrete pipes, slab culverts where by 16 small
to large bridges of which 4 will be removed and replaced and 10 will be rehabilitated with one
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will be retained and one will also be extended. In addition there are 332 culverts to be extended,
replaced or maintained based on the hydraulic reassessment of the areas in line with the
structural integrity of the existing structures and improved geometric designs.
Alignment and Terrain
The start of the project is at Gondar with altitude of 2300m and varies the altitudes from its peak
of 3000m at km 34.10 and reaches 2870m at Debark town.
Table 1.1 Terrain classification
No. Terrain Chainages (km )
From To
1 Hilly 0+732 , 15+400 4+603, 27+948
2 Rolling to Hilly 4+603 ,95+984 9+441,99+900
3 Rolling 9+441,27+948 10+957,95+984
4 Mountainous 10+957 15+400
Climate
The temperature of the project area is basically altitude induced and it is predominately cool
highland temperature. In day time temperature rarely rises above 30C in Gondar and 25C in
debark and rarely fall below 10C and 6C respectively. The average mean temperature is 21C
in Gondar and 14C in Debark. The mean annual rainfall in the project area varies between
980mm and 1,100mm.
Location Map
The project road is located in Amhara National Regional State in the northern part of Ethiopia. It
ween longitude 37-38 and Latitude 12-14
north.
Typical Cross sections
The road, in general, will have a 7m wide carriageway and 1.5m wide gravel shoulder on both
sides. In town sections the shoulder will be 2.5m wide and surfaced. In mountainous /very hilly
terrain/ the shoulder on the hilly side is provided as 1.50m wide, which has the combined
function of shoulder and longitudinal drainage.
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PROJECT LOCATION MAP
Fig. 1.2 Project Location Map
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2. OVER ALL INTERNSHIP EXPERIENCE
2.1. How I get in to the Company
I get in to the company by giving the letter, which was given to us by the University Industry
Linkage (UIL) office, to ERA (Ethiopian Road Authority) main office. The Northern regime
Manger, Ato Abey, positively accepted the letter to give training as an intern student for four
months and wrote a letter to the Gondar-Debark road upgrading project office of J Borrow and
Omega consulting company in Ambagiorgis town. As I arrived on the project area the company
received me with a great hospitality.
Next to this the assistant resident engineer, Ato Tekeste, control me as a supervisor and guide me
to understand the whole system of the construction. Even though they received me and control
me, for the first one month I was really bored, because I was only watching the works, moving
month of watching I begun to take samples from site and execute the laboratory tests with my
friends.
2.2. The Section of the Company I have been working
The sections I have been working are:
Site inspection
Laboratory: Lab-Assistance
2.3. The work flow in the sections:-
Inspection
Site Inspection
This work is done for approving the work that is done by the contractor. The main responsible
person for this work is the site Inspectors and Laboratory Technician on that site. They have a
duty to control each steps of the works and made their own evaluation to approve the work.
Assistant Resident Engineer
Work Inspectors Surveyor Site Lab-Technician
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Inspector: Inspectors are accountable to Assistant Resident Engineer. They are an authorized
representative of the Engineer assigned to make detailed inspections of the construction process
or contract performance.
Site Laboratory Technician: Site Laboratory Technicians are accountable to Assistant Resident
Engineer and Material Engineer. They are an authorized representative of the Engineer to make
detailed inspections of Materials quality and control execution of field tests. And perform
sampling and testing on sources of materials, stock piles and finished works.
Laboratory
Laboratory Technician: Laboratory Technicians are accountable to Material Engineer. They
have a responsibility to check/control the execution of the laboratory test and field tests. And
perform sampling and testing on sources of materials, stock piles and finished works.
Laboratory -Assistant: Lab-assistants are accountable to the laboratory technician. They have a
responsibility to control each and every steps of the execution of lab tests and field tests. They
record all the test results and check by their own self and transfer to laboratory technician.
2.4. The work I have been executing
In my internship time I have been executing different works in two sections of the company.
This works are inspection and execution of laboratory tests. Generally I have tried to cover the
basic works which are related to civil engineering works.
Material Engineer
Lab-Technician
Soil & Aggregate
Lab-Assistant
Asphalt
Lab-Assistant
Labors Labors
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2.5. The Meaning and Procedures of the works
2.5.1. Earthwork
This Division covers all works in connection with the preparation of the natural in-situ material
on which the embankment or capping layers are to be constructed. It is the preparation of the
sub-grade prior to the construction of pavement layers.
Equipment used for the preparation of roadbed and sub-grade are the following.
Loader
Excavator
Roller
Grader
Bulldozer
Chain Excavator
Cut
Cut mean all excavations from the road prism including side drains. In this portion of the road
prism the material was excavated to sub-grade or road bed level. All cuttings excavated below
the specified levels were back-filled with suitable material and compacted to the desired level.
Some considerations are taken when cutting is done. These are:
Type of material to be excavated
Water table
Slope determination
Volume and position of materials
Drainage and protection against erosion
Type of material to be excavated
Type of material to be excavated governs the construction method, the suitability of the cut
material for the sub grade and slope that can be safely adopted. At the place where there is a
Black-Cotton soil, which has low bearing capacity, undercut of 50cm was applied, and back
filled with suitable material to the desirable level. At the place where there is a massive rock and
boulders, the use of explosive material like dynamite and rock cutting machine was applied.
Water table
A water table may be permanent or seasonal. In any case its presence and characteristics (level,
flow of water etc.) is determined, as they affect the method of excavation and stability of cut
slope and the drainage system.
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Slope determination
The design slope of cut section is a compromise between the following requirements
Stability
Erosion
Appearance and visibility
Need of fill material
Minimum cost
Volume and Position of Different Materials:
Some materials need high energy to excavate and transport away from the excavation area. For
example at hilly place excavation by volume was considered.
Drainage and Protection against Erosion:
Cut section always needs drainage to drain out the water which comes from catchment area. For
the purpose of avoiding erosion, intercepting ditch was provided where slope of existing ground
is towards road and height of cut slopes exceeds 1m and it was constructed prior to the start of
earthworks. One meter of Berm at the foot of the cut slope was applicable where height of cut
slope exceeds 3m.
Fig. 2.1 cut (rock and soil excavation)
Table 2.1 cut slope
No. Material description Cut slope inclination (H:V)
1 Colluvial Deposit of Boulders, of Soils
or of Soil and Boulder
2:1 if condition permits, or else Retaining wall
2 Soil or common material 1:1
3 Decomposed Rock with Boulder 1:1 if condition permits, or else 1:2
4 Highly Decomposed Rock 1:1
5 Highly Weathered Rock 1:1
6 Decomposed Rock 1:2
7 Weathered Rock 1:4
8 Fresh or Hard Rock 1:10
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Construction of Embankment (Fill)
Embankment are the portion of the road prism composed of approved fill material which lies
above the original ground and is bounded by the side slopes, extending downwards and outwards
from the outer shoulder breakpoints and on which the pavement is constructed. The materials
used for the construction of the embankment are called fill material or embankment material.
This materials usually comes from borrow areas within the vicinity, approved for the purpose of
this road construction and are used to replace unsuitable road material.
Embankment is classified as
Earth embankment and
Rock fill embankment
The following factors are taken in to the consideration during embankment construction
Foundation condition
Acceptable fill material
Stability of slope
Settlement
Foundation condition
Foundation condition beneath embankment requires special attention to avoid shear failure and
excessive settlement. Wherever an embankment is built, detail investigation is done to determine
the most suitable construction method.
Acceptable fill material
Sometimes fill materials were obtained from cuttings. If the material is not suitable, other
material is transported from the borrow areas to the embankment. The requirement of
embankment material is shown in table 2.2.
Stability of slope
The edge of embankment should have a stable slope. The stable slope preserves sliding of the
soil at the age of embankment by its weight or environmental actions. This is done with suitable
slope with respect to the soil type. The slope of embankment depends on Depth of fill and Types
fill material. In this project, general embankment slope is 3:2 (H: V), but for embankment height
less than 1m the slope is 2:1 (H: V) as instructed.
The Embankment was constructed as follows:-
The surveyors fixed the slope stick limits according the design data.
Any unsuitable material was removed and replaced with appropriate materials as per the
preparation of the road bed)
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Field density test was done to check whether the necessary compaction have been attained at
the optimum moisture content.
After water showering, fill material was dumped.
The dumped fill material was placed at moisture content near the Optimum Moisture
Content (OMC) using Grader.
The placed material was compacted using Roller to attain 95% compaction on the field.
Fig. 2.2 construction of embankment
Sub-Grade
Sub-grade is the top portion of the natural soil, either undisturbed (but re-compacted) local
material in cut sections, or soils excavated in cut or borrow areas and placed as compacted
embankment. The type of subgrade soil is largely determined by the location of the road. The
Sub-grade level is the foundation on which the vehicle load and the weight of the pavement
layers finally rest.
The strength of subgrade for flexible pavement is commonly assessed in terms of California
Bearing Ratio (CBR). For this project the sub-
-base
but in some part, where black cotton soil is encountered, it constructed below the capping layer.
The Sub-grade was constructed as follows:-
The setting out work was done by surveyors.
The surface was showered over which the sub-grade layer is to be constructed
The subgrade material was dumped using Dam Trucks.
If the material to be used is dry water should be added and mix to attain the Optimum
Moisture Content, if the material is moist, it should be exposed to the sun to reduce moisture.
The material was placed by Grader following the pegs elevation.
To protect intrusion of materials the surface should be smooth and visually good.
The surface was compacted using single Roller to attain the desired field compaction level.
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Capping Layer
Where very weak soils and/or expansive soils (such as black cotton soils) are encountered, a
capping layer is sometimes necessary. It consists of better quality subgrade material imported
from elsewhere or subgrade material improved by stabilization (usually mechanical), and may
also be considered as a lower quality sub-base.
For this project capping layer was provided in small area where there was black cotton soil is
encountered. The construction process of capping layer is the same as sub-grade layers
For the determination of the suitability of the material, the contract document established
material requirement for embankment, capping layer and sub-grade material as follows in table:
Table 2.2 Inspection and test plan for: embankment, capping layer and sub-grade
No Description Testing method Acceptance criteria conducted on
1 Max. particle size Visual 4% for Fill
>15% Capping
Field Lab
3 Percent swell AASHTO T-193
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volume (Dam Trucks). The ratio is 1:2, means, one Dam Truck of crushed rock and two Dam
Trucks of natural soil from Borrow area. The thickness of the sub-base is 250mm for km0+730
to km4+500 (Traffic class T6) and 225mm for km4+500 to km99+900 (Traffic class T5).
The Sub-Base was constructed as follow:-
After setting out work was done by surveyors, the material came from the borrow pit
using Dam Trucks and dumped on the prepared sub-grade.
The material was thoroughly mixed, spread and arranged to the required (settled) width
and thickness. But segregation (pockets of fine and courser material) shall be avoided.
The Roller passed two or three times.
The shower truck showered the layer to satisfy the desired moisture content during
compaction and compacted with rollers until the desired compaction level was reached.
During leveling and compacting, the elevation was continuously checked by surveyors.
For the determination of the suitability of sub-base material, the contract document established
testing methods and requirements on materials properties as follows in table:
Table 2.3 Inspection and test plan for: sub base materials
No Description Testing method Acceptance criteria conducted on
1 Max. particle size Visual 30% Field Lab
3 LAA AASHTO T-96
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2.5.2.3. Base course
Base course is a layer of material of specified dimension constructed on the top of sub-base. It is
the main structural part of the pavement contributing to the spreading of the traffic loads and it
provides a level surface for laying the surface layer. Base course materials must have a particle
size distribution and particle shape which provide high mechanical stability and should contain
sufficient fines (passing of 0.425 mm sieve) to produce a dense material when compacted.
Material source: For this project the material used for road base layer is crushed rock. It is
produced from crushing of rocks
The base course is found about 5 cm below the finished surface level. It has 200mm thickness
fromkm0+730 to km4+500 (Traffic class T6) and 175mm thickness from km4+500 to
km99+900 (Traffic class T5).
In most part of the road the base course and the shoulder are constructed from the same material
and constructed simultaneously. But at the place where the base course and the shoulder are
constructed from different material, the shoulders was first constructed and neatly cut to the
required line to provide lateral support for the base course.
Fig. 2.3 Construction of Base Course, it was the same as sub-base as expressed above
For the determination of the suitability of base course material, the contract document
established testing methods and requirements on materials properties as follows in table:
Table 2.5 Inspection and test plan for: base course
No Description Testing method Acceptance criteria conducted on
1 Grading AASHTO T-27 Sts. Table 5200/1 Field Lab
2 Plasticity index AASHTO T-90 100% Field Lab
4 LAA AASHTO T-96
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Table 2.6 Grading requirement of base course material
Sieve Size Specification by % passing
63 100
50 100-90
37.5 100-80
25 51-80
10 70-35
5 -
2.36 -
0.425 -
0.075 5-15
Pan -
2.5.2.4. Bituminous Prime Coat
It is bituminous treatment applied to the surface of a newly constructed unbound road base prior
to the construction of a bituminous layer or surface treatment (generally it is an application of
liquid bituminous material to previously untreated base course surface). It serves:-
To consolidate the surface on which the new treatment is to be placed;
To promote bond between base and wearing surface;
To act as a deterrent to the rise of capillary moisture into the wearing surface;
No prime was applied under the following adverse conditions;
a) During foggy or wet conditions;
b) When the rain is imminent;
c) When the surface (base course) is wet, i.e. more than dump;
d) when wind is sufficiently strong to cause uneven spraying;
Note: Not more than 24 hours before spraying, the layer to be primed must be broom and cleaned
of all loose or deleterious material.
For this project, according to the contract document, the priming material should be MC-30
cutback bitumen and the application rate is 0.9-1.12 lit/m
Fig 2.4 Application of prime coat
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Tack coat
A bituminous treatment applied to the surface of an existing bituminous layer prior to the
construction of a new bituminous layer. During construction, to give accesses to transportation
one of the lanes was constructed (finished) first. To continue the other, tack coat is used as a
binder of the two lanes. This material is rapid curing material with a composition of 60% of
water and 40% of bitumen mixed by the process of Emulsion. Bitumen is inert material to
combine with water the chemical called Dinorium is added. The material used for tack coat was
called RC-70 cutback bitumen.
Fig 2.5 Tack coat
2.5.2.5. Asphalt Concrete Layer (Surface Course)
It is a structural part of the pavement constructed on top of the road base, which is tough enough
to resist distortion under traffic and provide a smooth and skid resistant riding surface. It is the
layer of asphalt concrete, mixture of different gradation of aggregates, internal and external
fillers and asphalt cement, the highest quality material is necessary. To perform satisfactorily, the
finished bituminous layer needs to possess the following characteristics.
High stiffness in order to reduce the stresses in underlying layer.
High resistance to deformation.
The surface course must be waterproof to protect the entire pavement and subgrade form
the weakening effect of water.
High resistance to fatigue and ability to withstand high strain.
High resistance to the environmental degradation.
This work consists of furnishing and mixing aggregates with asphalt binder at a mixing plant to a
specific temperature, transporting, laying and compact the mixture on an approved primed or
tacked base in accordance with the specification.
Material source: The asphalt concrete layer is made from high quality crushed stone and
bitumen. Both the aggregate and the bitumen have to pass different types of tests that are done on
the design stage. The design was conducted based on marshal mix design method. The
aggregates used for asphalt concrete were produced from the quarry site located at km44+500
and mixed at the mixing plant located at km44+500. The total thickness of surface course is 5 cm
all over the length of the road (0+730 to 99+900).
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Fillers: If the grading of the combined aggregates for asphalt surfacing mixes shows a deficiency
in fines, approved filler may be used to improve the grading. Filler may consist of active filler of
inert material such as rock dust having the required grading necessary to improve the grading of
the combined aggregates. In no instance shall more than 2% by mass of active filler be used in
asphalt mixes.
Table 2.7 Inspection and test plan for: Coarse Aggregates (Asphalt concrete)
No. Description Testing method Acceptance criteria conducted on
1 Grading AASHTO T-27 Sts. Table 6400/8 Field Lab
3 ACV BS 812-1990
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The surface course was constructed as follows:-
The primed base was prepared using Air Compressor to remove dusts or unwanted material
To keep the temperature of mixture during transportation, the Tucks were covered.
The paver placed the mixture about 6.5cm depth.
Compacted by steel-tired and pneumatic-tired Roller. Then, it cooled and opened to traffic.
During compaction the Rollers shall be equipped with adjustable scrapers for cleaning the
drums and an efficient means of moistening the drums to prevent adhesion of asphalts.
Thing that we should note during compaction:-
On hilly areas the direction of compaction should be from the bottom to the top, this is
to protect the pavement layer from sliding down.
The compaction paths should be overlapped to each other; this is to avoid the bulging
of materials in between two paths.
On curves compaction should be started from inner side (smaller radius) of the road
curve and continues to the outer part, this is done to protect the super elevation from
sliding down.
Fig. 2.6 Construction of Bituminous Surface Course
At all stages the work inspector check the temperature of the asphalt mix. If it is below the
acceptable temperature the contractor has to remove the asphalt mix.
Table 2.10 Temperature of the mix
Measurement taken at
Temperature c
Loading the truck at the plant 145-170
The truck reaches the site 145-150
The finisher paves 135-145
The steel roller makes compaction 120-125
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2.5.3. Construction of Structures
2.5.3.1. Drainage structure
Adequate and economic drainage is absolutely essential for the protection of the investment
made in highway and for safeguarding the lives of the person who use it. The measures taken to
control the flow of surface water is generally termed as surface drainage. In surface drainage
system, the water is first collected in longitudinal drains, and then disposed to the nearest stream,
valley or watercourse. Cross drainage structures like culverts and small bridges may be necessary
for the disposal of surface water from the roadside drains. Road surfaces are normally crowned
to facilitate the removal of surface water from the surface trough cumber slope. The materials
(aggregate, sand, masonry) used for the construction of drainage structures are tested properly
and must qualify the requirements of the contract document.
Table 2.11 Inspection and test plan for: Masonry stone
No. Description Testing method Acceptance criteria conducted on
1 Specific gravity AASHTOT-85-94
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All of these ditches the thickness of stone is 20 cm. The slope used for side ditches are the same
as those used on centerline of the road. In major town sections, due to the limitation of land
width, underground longitudinal drains (pipes or U-shaped with ditch cover) were provided on
both sides. They are made from concrete and stones. The concrete is mixed with ratio of 1:3 and
has a grade of C-30/20 (C-30 and maximum aggregate size is 20mm)
Minor Drainage Structures
Minor drainage structures are structure, other than Bridge, which provide an opening under the
carriageway for drainage. And used where bridges are not hydraulically required, where debris is
tolerable, and where they are more economical than a bridge. Whenever streams have to cross
the roadway, facility for cross drainage is to be provided. The water from the side drain is taken
by those cross drains in order to divert the water away from the road, to a watercourse or valley.
Slab culvert
In slab culvert, RC slab is placed over abutments made of masonry and the span is generally
limited to 4.5m. They are usually specified for larger flow than pipe culverts. Headwall and
Wing walls are provided to protect the sides of the embankment against erosion. The upstream
wall is called headwall and the downstream is called end wall. In this project this culverts are
constructed from a concrete of grade C-30/20
Fig. 2.8 slab culvert
Box Culvert
Concrete box culverts are constructed with a square/rectangular opening, made from reinforced
concrete (RC) with wing walls at both ends. They are usually specified for larger flows and
where the area of the foundation soil is weak (exposed to differential settlement). Headwall and
Wing walls are provided to protect the sides of the embankment against erosion.
In this project this culverts are constructed from a concrete of grade C-30/20
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Fig. 2.9 box culvert
Pipes culvert
They are locally produced and economical. They have bell and spigot joints, which are sealed
during construction with Portland mortar. The foundation on which the pipes laid could be a
natural bed or concrete cradle depending on foundation conditions and loads on the pipe. Pipe
culverts can often be placed particularly on lower volume roads without headwalls or wing walls.
They are constructed from a concrete grade of C-35/20.
During construction of all culverts, to create working
space the edge of excavation limit was 60cm away from
the edge of structure the foundation of the structures
were done by 10cm concrete bedding (lean concrete).
The back fill material was advised by Material
Engineer.
Fig. 2.10 Pipe Culvert
2.5.3.2. Retaining wall
Reta
the road is built up on it. At the place where there is a high cut and a high fill, the uses of
retaining walls is recommended. It used to retain the soil when the load is applied on it.
This Gondar-Debark road upgrading project comprises 15 stone masonry retaining walls. Five
retaining walls replaced the existing ones and ten new classes A masonry retaining walls are
constructed. The foundation of the stone masonry shall be prepared on the approved foundation
material. Where the foundation material is rock, 100mm thick layer of grade 15concrete was
used. And where the foundation material is other than rock, 100mm thick layer of crushed stone
compacted to 97% of its MDD and a second 100mm thick layer of grade 15 concrete was used.
The slope of the retaining walls is 3:8 (H:V) for front part and 1:8 (H:V) for the back. For the
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purpose of drainage of the soil retained 10cm diameter weep holes are provided at every 3m
horizontally and 1m vertically. The walling is constructed with stones and 6:1 sand: cement
mortar. Before placing all the stones were thoroughly wetted with water. After completion the
walling should be protected from the elements and kept moist for a minimum period of four
days. The masonry used for this structure is tested according to table 2.6.
Fig. 2.11 Construction of Retaining Wall
2.5.4. Laboratory Tests I Have Been Executing
2.5.4.1. Tests on Asphalt (Bitumen)
Asphalt Penetration Test
Objective: The penetration test is used to measure consistency (hardness or softness) of solid or
semi-solid bituminous material.
Main Principle: The sample was melted and cooled under controlled condition. The penetration
was measured with penetrometer by means of which a standard needle was applied to the sample
under specified conditions. A needle (50.8mm length and 1/1.02mm diameter) was allowed to
penetrate vertically into a sample under specified load (100g), temperature (25C) and time (5 sec)
conditions. The distance the needle penetrates in units of 1/10 mm is termed as penetration value.
For each test a minimum of three valid measurements were performed, the locations on the
sample surface must be a minimum of 10 mm apart and away from the container side.
For this project the penetration value is expected to lie between 80 and 100 (80/100), because,
the average weather condition of the project area is cold weather (14C -21C). The higher
values of penetration indicate softer consistency, so we should use the softer bitumen for cold
weathered environment and vice versa.
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Calculation: When the requirements in table above are met, calculate the average value to the
nearest whole unit (1/10-mm).
Fig. 2.12 Execution of Asphalt Penetration Test.
Softening Points of Bitumen
Objective: The softening point test is used to measure the temperature at which the bitumen shows
fluidit y. It is an indicative of the tendency of material to flow at elevated temperature encountered
in service. It is also useful in evaluating the uniformity of shipment or source of supply.
Main Principle: Two samples of bitumen were casted in shouldered brass ring. A steel ball of
3.5g was placed on a sample contained in brass rings and suspended in water. Water is used for
softening points of 80 C and below, and glycerin is used for softening points greater than 80 C.
The bath temperature is raised at 5 C/min, the binder gradually soften and eventually deform
slowly as the ball falls through the rings. At the moment the bitumen and steel ball touches the
base plate 25 mm below the ring, the temperature of water is recorded as softening point.
For this project the value should be 42C-45C, for hot weather condition the softening point
would be higher.
Calculation: The test was performed in duplicate, if the difference between the two does not
exceed 1C, the mean of the two measured temperatures is reported, which otherwise entails
test repetition.
Fig. 2.13 Execution of Softening Point Test
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Ductility Test
Objective: The ductility test is used to describe the ductile and tensile behavior of bitumen. The
ductility of Bitumen is an indication of its elasticity and ability to deform under load and return
to original condition upon removal of the load. The result also indicates the extent to which the
material can be deformed without breaking.
Main Principle: the Bitumen sample was casted in the mold consisting of two jaws, and then
placed in a water bath of specified temperature (25C). One jaw moved (stretched) away from
the other at a standard rate of 50mm/min. The distance it moves before the thread between the
two break is the ductility in centimeters.
Calculation: The ductility of a bituminous material is measured as distance to which it will
elongate before breaking when two ends of a briquette specimen of the material are pulling apart
at a specified speed and at specified temperature. The Distance (cm) between the end clips in cm
when the test specimens break. For this project the value should lie above 100.00cm.
Fig. 2.14 Execution of Ductility of Bitumen Test.
Cut back distillation test
Objective: This test method covers a distillation test for cut-back asphaltic products. This
procedure measures the amount of the more volatile constituents in cutback asphaltic products.
Main Principle: Two hundred milliliters of the sample was distilled in a 500ml flask at a
controlled rate to a temperature in the liquid of 360C (680 F) and the volumes of distillate
obtained at specified temperatures are measured. The residue from the distillation and also the
distillate may be tested as required.
For this project this test is applicable for prime material. This material is a mixture of 60%
cutback asphalt and 40% of kerosene, MC-30. To check its composition we applied distillation.
And the result must lie within the specified range in the table below.
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Table 2.12 The range at which the volume of distillate must lie
Description (C) Amount of distillate (ml) Specification
Temperature Test result in the cylinder Min Max
225 - 25
260 40 70
316 75 93
360
Calculation:- Asphaltic Residu- the volume percent residue(R) to the nearest 0.1 as follows:
R = [(200-TD)/200]100, TD%=(TD/200)100 w/r TD = total distillate recovered to 360C,ml.
Fig. 2.15 Execution of cut-back distillation test
2.5.4.2. Tests on Asphalt Mixture
Quantitative extraction of bitumen and mechanical analysis of extracted aggregate
Objective: These methods cover the quantitative determination of bitumen in hot-mixed paving
mixture. The aggregates obtained by this method may later be sieved to determine the aggregate
grading within the pavement material.
Main Principle: The paving mixture was washed (extracted) with trichloroethylene, using the
extraction equipment. The extracted aggregate again washed with soap to remove the solution
from the aggregate. Then bitumen content was calculated by the differences in mass of the
original sample and the oven dried extracted binder-free aggregate. Finally by making sieve
analysis for oven dried binder-free aggregate, we checked the gradation of the aggregate in the
pavement material.
For this project the amount of bitumen content should be 5.00.2%. And the mechanical sieve
analysis of extracted aggregate should lie between the specification (upper and lower limit)
Table 2.13 Gradation of Asphalt Aggregate Sieve(mm) 26.5 19 13.2 9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075 pan
% passing
Upper limit 100 97.2 84.5 74.8 58.7 43.0 28.0 21.5 15.2 11.7 10.6
Lower limit 100 87.2 74.5 64.8 50.7 35.0 20.0 13.5 9.2 7.4 6.6
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Calculation: Bitumen content (%), I = H/A, w/r H=A-(B+F), H = Mass of bitumen
A = original (total) sample, B = mass of aggregate after extraction, F = mass of filler
Fig. 2.16 Extraction Equipment
Maximum Theoretical Specific Gravity of Bituminous Paving Mixture (MTD)
Objective: This method is used to determine the maximum theoretical specific gravity and density of
uncompacted bituminous paving mixture. It is also called the void-free density. Maximum
theoretical density is influenced by the compositions of mixture in terms of types and amount of
aggregates and bituminous materials. It is used to calculate air void in compacted asphalt mixture.
Main Principle: A weighted sample of oven-dry paving mixture in the loose condition was
placed in a tared vacuum vessel. Sufficient water at a temperature of 25 4C was added to
completely submerge the sample. To remove the entrapped air within the sample, vacuum was
applied for 15min. At the end of the vacuum period, the vacuum gradually released. And the
vacuum container with sample was immersed in to a water bath for 10 min. The volume of the
sample was obtained by measuring the mass of a vacuum container with sample and level full of
water, mass of the container filled with water, and mass of dry sample in air. If the temperature
employed is different from 25C an appropriate correction is applied.
Calculation: Maximum theoretical specific gravity (Gmm) = K*A/(A+B -C),
W/r A=mass of dry sample in air, B=mass of jar filled with water, C=mass of jar filled with water
and sample, k=water temperature correction.
Fig. 2.17 Vacuum Vessel
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Asphalt Concrete Mix Resulted by Marshal Method (Conformtive Test for Mix
Design)
Objective: This method covers the measurements of the resistance to plastic flow and its
stability of cylindrical specimens of bituminous paving mixture (with max. aggregate size is
25.4mm) loaded on the lateral surface by means of the marshal apparatus.
Main Principle: A cylindrical Asphalt specimens, 1200gm of asphalt mixture compacted with
75 blows of 4.5kg mass on the top and bottom in 101.6mm diameter and 76.2mm high mold, are
loaded on the lateral surface by means of the Marshal apparatus at a specified loading rate and
temperature (60C). The resistance against plastic flow is measured.
This method works based on the determined optimum bitumen content for a particular grading
of aggregate which results good stability and flow that satisfies the requirement.
For this project the flow and stability should lie within 2 4 and minimum10KN, respectively.
Calculation: The Marshall stability is calculated by multiplying the maximum load value with a
correction factor depending on the specimen height.
Fig. 2.18 Marshal Method, for stability and flow
2.5.4.2. Tests on soil and aggregate
Atterberg limit test
The water content level at which the soil changes from one state to other are known as Atterberg
limits. It includes liquid limit (LL) and plastic limit (PL). it is determined using Casagrande cup
method.
Objective: Used to determine the moisture content at which the soil changes from liquid state to
plastic state and from plastic state to solid state, is called Liquid Limit and Plastic Limit
respectively. They are important limits of engineering behavior, because they facilitate the
comparison of water content at which the soil changes from one state to another. It also used to
determine the stiffness or consistency of the soil, which in turn depends on moisture content.
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Main Principle: The liquid limi t (LL): is arbitrarily defined as the water content in percent at
which part of soil in a standard cup and a cut by a groove of standard dimension wil l flow together
at the base of the groove for a distance of 13 mm when subjected to 25 shocks from the cup being
dropped 10 mm in a standard liquid limi t apparatus operated at a rate of two shocks per second.
Plastic limit: The plastic limit (PL) is the water content, in percent, at which a soil can no longer be
deformed by rolling into 3.2 mm (1/8 in.) diameter threads without crumbling.
Plasticity index (PI): The Plasticity Index is the range of moisture content in which a soil is
plastic. It is the numerical difference between the liquid limit and plastic limit of the soil.
(PI=LL-PL).
Fig 2.19 Execution of LL and PL test using Cassagrande Cup Method
Particle size distribution wet sieve
Objective: A particle size distribution analysis is a necessary classification test for soils,
especially coarse soils, which contain relative portions of different sizes of particles. From this it
is possible to determine whether the soil consists of predominantly gravel, sand, silt or clay sizes
and, to the limited extent, which of these size ranges is likely to control the engineering properties
of the soil. For coarse and fine aggregates which are free from particles that cause agglomeration,
Dry Sieving may be performed. But for aggregates which may contain clay or other materials
likely to cause agglomeration, preliminary separation by washing through a fine sieve is required
before dry sieving, i.e. washing and sieving.
Main Principle: A minimum of 2.5kg sample were allowed to dry then washed the material
through 75m sieve, allowing the material passing sieve 75m to run to waste. All the retained
materials were dried in oven and sieved the dried fractions through the appropriate test sieve.
Finally weigh the amount retained on each sieve and any fines passing the 75 m test sieve and
record. The value of silt and clay can be obtained by difference of dried sample of before wash
and after wash.
Calculation: Calculate the cumulative percentage by mass of the sample passing each of the
sieves, from the general relationship: (% passing this sieve ) = (% passing previous sieve) - (%
retained on this sieve).
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Fig. 2.20 sieve analysis
Aggregate Shape Test
Objective: The shapes of aggregate particles play an important role in pavement strength.
Aggregate particles may have rounded, cubical, anger, flaky or elongated shapes. Flakiness Index
and Elongation Index are one of the tests used to classify aggregates. For base course and
wearing course the presence of flaky and elongated particles are considered undesirable as they
may cause inherent weakness with possibilities of breaking down under heavy loads.
Main Principle: Flakiness Index: Aggregates are classified as flaky when they have the
thickness of less than 60% of their mean sieve size. The flakiness index of an aggregate
sample was found by separating the flaky particles using thickness gauge and expressing
their mass as a percentage of the mass of the sample. The test is not applicable to material
passing a 6.30mm test sieve or retained on a 63.0mm test sieve.
Calculation: FI=100(M1/M2), M1=Wt. of sample passing the gauge, M2=the sample
taken
Elongation Index: Aggregate particles are classified as elongated when they have a length
(greatest dimension) of more than 1.8 of their mean sieve size. The Elongation Index of an
aggregate sample was found by separating the elongated particles and expressing their mass as a
percentage of the mass of the sample. The test is applicable to material passing a 50 mm sieve
and retained on a 6.3 mm sieve.
Calculation: FI=100(M1/M2), M1=Weight of elongated particles M2= the sample taken
Fig. 2.21 flakiness sieve