Report_Content

IRB/Training Report/2016-17 1

1. INTRODUCTION

ABOUT THE ORGANIZATION:

IRB Infrastructure Developers Ltd. was incorporated to fund the capital requirements of the IRB

Group initiatives in the infrastructure sector. The company undertakes development of various

infrastructure projects in the road sector through several Special Purpose Vehicles. (Businesses of

holding co. and its subsidiaries will be implemented under superintendence, direction and control of

the board of holding company, with the objective of maximizing value for all stakeholders.)

The company, along with its subsidiaries has constructed or, operated and maintained around 9,295

lane Kms. of road length so far and one of the major road developers in the country. The aggregate

size of all our BOT projects (both completed and under execution) is around Rs. 284,928 Million

Date of Establishment 27-07 1998

Revenue

411.219 ( USD in Millions )

Market Cap

74173.5225 ( Rs. in Millions )

Corporate Address

I R B Complex ,Chandivli Farm ,Chandivli Village, Andheri

(East)Mumbai-400072, Maharashtra

www.irb.co.in

Management Details Chairperson - Virendra D Mhaiskar

MD - Virendra D Mhaiskar

Directors - BL Gupta, Mukeshlal Gupta, Sudhir Rao

Hoshing, Sunil Tandon, Sandeep J Shah, Sunil H Talati,

Chandrashekhar S Kaptan, Suresh G Kelkar, Deepali V

Mhaiskar

Business Operation

Engineering – Construction

Financials

Total Income - Rs. 22008.205783 Million ( year ending

Mar 2015)

Net Profit - Rs. 1383.25346 Million ( year ending

Mar 2015)

Company Secretary

Mehul Patel

Bankers

ICICI Bank, IDBI Bank, Indian Bank, Indian Overseas

Bank, Punjab National Bank, Union Bank of India, Central

Bank of India, Canara Bank, Corporation Bank, Bank of

Baroda, Bank of India, Bank of Maharashtra, Andhra Bank

Auditors

SR Batliboi & Co LLP, Suresh Surana & Associates LLP

http://www.irb.co.in/


2. DETAILS OF THE PROJECT

NAME OF PROJECT: Four Laning of Solapur- Yedshi section of NH-211 from Km. 0.000 to Km.

100.000 in the state of Maharashtra under NHDP Phase-IV through PPP on DBFOT basis.

NAME OF CONCESSIONAIRE: M/s. IRB Infrastructure Developers Ltd.

The project under consideration starts from Solapur to Yedshi. The project length from

Solapur to Yedshi i.e. Km 0.000 to Km. 100.000 = 98.717 Km is under PIU Solapur. The salient

feature of the project length under PIU Solapur is as below:

(A) IMPLEMENTATION DETAILS :-

Sr.

No. Description Details

1 Name of Project

Four Laning of Solapur- Yedshi Section of

NH-211 from Km. 0.000 to Km. 100.000 on

DBFOT basis under NHDP Phase-IV.

2 Name of Concessionaire M/s. IRB Infrastructure Developers Ltd.

3 Client or Employer National Highway Authority of India

4 Date of Start 3rd Septembre 2014

5 Schedule Date of completion 1st March 2017

6 Construction Period 30 Months

7 Concession Period 29 years.

8 Length of Project (Km) 98.717 Km in Maharashtra.

9 Project Cost 14920 Million

(B) SCOPE OF WORK / SILENT FEATURES OF THE PROJECT :-

Sr. No. Description Details

1 Four Laning of Carriageway 98.717 Km. In Maharashtra state

2 Major Bridges 2 Nos.

3 Minor Bridges 25 Nos.

4 Culverts 134 Nos.

5 Construction of new Flyovers 7 Nos.


Sr. No. Description Details

6 Road Over Bridge (ROB) 1 Nos.

7 Vehicular Underpasses 7 Nos.

8 Pedestrian Underpasses 11 nos.

9 Bypasses

2 nos.

i) Tuljapur Bypass - Existing Ch. 39/620

(Design Ch. 39+430) to Existing Ch.

44/000 (Design Ch. 42/867) = 3.437 Kms.

ii) Yedshi Bypass - Existing Ch. 80/500

(Design Ch. 79+770) to Existing Ch.

82/800 (Design Ch. 81/900) = 2.3 Kms.

10 Service Roads 33.622 Kms.

11 Major Road Intersections 11 Nos.

12 Minor Road Intersections 55 Nos.

13 Bus bays with passenger shelter 2 x 24=48 Nos. places in Both directions.

14 Truck Lay byes 4 Nos. LHS & RHS.

15 Toll Plaza

2 Nos. at Design Chainage 19+360 (Existing

Chainage 19+450)

Design Ch. 77+650 (Existing Ch. 78+390)

16 Base Traffic/ (PCU)-2010

15018 PCU at km 20/200

16455 PCU at km 76/050

17 Rest Area

2 Nos.

18 Realignment

5 Nos.


3. STRUCTURAL DEPARTMENT

CONSTRUCTION OF MAJOR BRIDGE

DETAILS OF THE STRUCTURE:

1. Chainage where, Major Bridge is located : CH.23+796

2. Total Length of the Bridge: 60 m Span : 10m

3. No. of Spans : 6 Nos.

4. Cross section of the pier : Circular type

5. Type of the foundation : Pile foundation

6. Grade of the concrete used for R.C.C : M35

7. Grade of the concrete used for P.C.C : M15

8. Size of the bars used for Pier Construction : 10, 12, 16, 20, 25 mm

9. Size of the bars used for Abutment : 10, 12, 16, 20 mm

10. Slump of the concrete used : 150mm

11. Temperature of the concrete : 28 ̊C

12. Grade of the concrete used for

crash barriers & Friction slabs : M40

Figure: Pier Details


4. STRUCTURAL DETAILS

GENEARAL

1. The notes shall apply to the drawing listed as Bridge/Structural drawings.

2. The design is based on the following codes(with latest amendment’s as published in Indian

Highway)

1. IRC: 5-1998 09. IRC:SP:42-1994

2. IRC: 6-2010 10. IS:456-2000

3. IRC: 24-2010 11. IS:458-2003

4. IRC: 78-2000 12. IS:783-1985

5. IRC: 83-(Latest) 13. IS:2911-(Latest)

6. IRC: 89-1997 14. IS:2950-1981

7. IRC: 112-2011 15. IS:6403-1981

8. IRC: SP: 13-2004 16. IS:8009-(Latest)

3. All dimensions are in mm, levels are in meters & Chainage are in Kilometers unless

otherwise mentioned on the drawings only written dimensions shall be followed dimensions

shall not be scaled.

4. The following live loads are considered in the design.

1. Carriageway live loads shall be as per IRC:6-2010

2. Bridge having footpath is designed for three lanes of vehicular loading ignoring

footpath.

5. The design are applicable for ‘moderate’ condition of exposure for over land/elevated

structures and ‘severe’ condition of exposure for structure below High Flood Level(HFL) as

per IRC:122

6. When only wearing coat is provided over RCC slab .The same shall be 50mm thick asphaltic

concrete laid over water proofing membrane.

7. All items of the work shall conform to relevant MORT & H specifications.

MATERIAL SPECIFICATIONS:

CONCRETE:

1. Concrete shall be design mix and shall have a minimum 28 days characteristics strength as

given below on 150mm cubes unless otherwise shown on relevant detailed drawings

Superstructure for Bridge & Flyovers:

1. R.C.C. crash barriers/Friction slab :M40

2. R.C.C. T-Girder and deck slab :M35

3. R.C.C. Solid slab (for bridged) :M30

4. P.S.C. Girder and deck slab :M40

5. Approach Slab :M30

Substructure and Foundation for bridges & Flyovers:

1. RCC Pier & Pier cap :M30

2. RCC abutment and abutment cap :M30

3. RCC Open foundation :M30

4. RCC Piles :M35

5. RCC Pile caps :M30

6. PCC Leveling coarse & annular filling :M15


For Culverts:

1. RCC Box (Under passes/Minor Bridges) :M30

2. RCC Box (Culverts) :M30

3. RCC retaining wall :M30

4. RCC Substructure & Foundation :M30

5. PCC lean concrete :M15

6. RCC Solid slab (For Culverts) :M30

7. PCC Structural Member :M25

2. Only ordinary Portland cement (53 Grade) conforming to IS: 12269 or ordinary Portland

cement (43 Grade) conforming to IS 8112 capable of achieving the required design concrete

strength shall be used.

3. TO improve workability of concrete and cement grout, admixture conforming to IS: 6925

and IS: 9103 could be permitted subjected to satisfactory proven use admixture generating

Hydrogen Nitrogen Chlorides etc. should not be used.

4. The maximum size of aggregate shall be used in RCC & PSC work shall be 20mm

5. Maximum water cement ratio (W/C) shall be restricted to 0.45 for RCC/PSC structural

members and 0.5 for PCC components.

WATER:

Water to be used in concreting & curing shall conform to clause 18.4.5 of IRC: 112-2011.

REINFORCEMENT:

1. All reinforcing steel shall be High Yield Strength Deformed bars (HYSD) (Grade

Designation Fe500) conforming to IS: 1786 structural steel shall conform to IS: 2062.

2. Binding wires should be analyzed 18 gauges mild steel free from any deleterious matter, Dust

etc.

3. At the location where reinforcing bars are congested (Like Girder Bulbs),Mechanical splices

may be used instead of over lapping to provide sufficient clearance between adjacent bars.

REINFORCED CONCRETE PIPES:

1. NP4 type pipes conforming to the requirements of IS: 458 shall be used.

2. Bedding below pipes shall conform to clause 2904 of MORT & H specifications.

BEARING & EXPANSION JOINTS:

1. Tar papers/Elastomeric pad/pot-PTFE bearings shall be used as per drawings.

2. Expansion joints :

(i) Filler type joints : For movement of 0 to ±10 mm

(ii) Elastomeric slab seal type : For movement ±10 mm to ±40 mm.

(iii)Elastomeric strip seal type : For movement more than± 40mm.

3. Fabricated steel parts of expansion joints shall be positioned accurately before the concreting

of that portion of deck slab.

4. Presence of manufacturer’s preventative at the time of positioning of embedment parts and

installation of expansion joints is mandatory.

5. Marginal modification in the structure details e.g. Pedestal etc. for compatibility with the

bearing & expansion joints details shall be permitted. Subjected to approval of the Engineer.

6. The expansion joints must be robust, durable & replaceable they must be provided over the

full width of super-structure including Kerb/Crash barriers & Footpath following the profile

of the same (Where relevant) expansion joints shall be obtained only. From approved

manufacturers.


PRESTRESSING:

1. Cable consisting of 12.7 mm dia. or 15.2 mm dia. (As indicated in the relevant drawings) 7-

ply class 2. Low relaxation stress relieved strands conforming to IS: 14268 shall be used. The

minimum guaranteed ultimate tensile stress shall be 1860 N/mm2.

2. The pre-stressing steel and accessories shall be subjected to acceptance test prior to the actual

use in the works

3. Only multi strands jacks shall be used, for tensioning of cables. Direct and indirect force

measurement device (e.g. pressure gauge) shall be as attached in the construction with

system.

4. Hope corrugated sheathing shall be used. Internal dia. of sheathing shall be mentioned on

relevant drawing.

WORKMANSHIP/DETAILING:

1. The minimum clear cover to all reinforcing shall be as follows.

(i) Superstructure : 40mm

(ii) Substructure/Piers (Element above G.L.) : 40mm

(iii)Abutment/Retaining Walls : 75mm

(iv) Foundation/Elements below G.L. : 75mm

(v) Box/Trough/Manhole Structure : 75mm

(Faces in contact with earth)

(vi) Box/Trough/Manhole Structure : 45mm

(Faces not in contact with earth)

2. For ensuring proper clear cover to reinforcement, the cover blocks of same grade as of parent

concrete shall be provided & should be able to withstand the crushing forces during

construction.

3. Bending & fixing of reinforcement bars shall be as per IS: 2502-1963.

4. The basic lap length ‘Ld’ shall be as follows:

Table No. Basic Lap length ‘Ld’

Sr.

No. Concrete Grade

Lap length for Fe500

grade bar

1 M50 29d

2 M45 32d

3 M40 34d

4 M35 36d

5 M30 40d

6 M25 47d

7 M20 54d

Where’d’ is the diameter of the smaller bar to be lapped.

Actual lap length La shall be ‘k x Ld’ where, value of k is as below laps shall be

suitably staggered anchorage length shall be equal to basic lap length.


% Reinforcement lapped ‘k’ Value

Up to 25 1.0

>25≤33 1.15

>33≤50 1.4

More than 50 1.5

Lap length of main reinforcement bars on top surface of concrete elements shall be ‘1.43xLa’

5. Supporting chairs of 12 mm dia. shall be provided at suitably intervals.

6. Steel spacer bars shall be provided between adjacent layers of parallel reinforcement &

spaced at not more than ‘60 x Smaller bar dia.’ The diameter of the space bar shall be at least

25 mm but not less than the maximum dia. of the parallel reinforcements.

7. Suitably designed form works details shall be prepared by the contractor & got approved

from the superposition agency before concreting.

8. Proper compaction of concrete shall be ensured by use of form & or needle vibrators.

9. Shuttering plates shall be suitably stiffed to enable the compaction by form vibrators.

10. All setting out dimensions R.L. concrete dimensions & cable profile to be verified at site

before construction commences any discrepancy shall be brought to the notice of the engineer

immediately.

11. The location of jacks for lifting the superstructure to replace bearings etc. is shown in thus

(1).This shall be distinctly sketched on soffit of superstructure and on pier/abutment caps.

12. During jacking operation all jacks placed and cross girder shall be operated simultaneously

using stress control system so as to ensure that the reaction on the jacks is equal at all times,

during jacking operation, the traffic shall not be allowed to ply on the carriageway.

CONSTRUCTION JOINTS:

1. Construction joints shall be provided only at locations shown on the drawings for

superstructure concreting operation shall be carried out consistency up to the construction

joints.

2. Construction joints are not allowed in pier abutments caps & open isolated footings.

Construction joints may be provided at desired locations on abutment/pier stem & in RCC

box structure with prior approval from the supervision agency.

3. The concrete surface at the joints shall be brushed with a stiff brush, after casting while the

concrete is still fresh & it has only slightly hardened.

4. Before new concrete is poured the surface of old concrete shall be prepared as under.

A. For hardened concrete, the surface shall be thoroughly cleaned to remove debris & laitance &

made rough, so that 1/4th of the size of the aggregate is exposed but without dislodging the

aggregate or structural damaging the concrete.


5. ASPHALT BATCH MIX PLANT

Location: Tamalwadi Chainage: Ch.16+000 RHS

Details about batch type hot mix Asphalt Plant with picture.

Model : DG3000 Rated Capacity: 240 T/H

Mixer Volume : 3000 Kg. Installed power: 656 KN

S/N : L142430 Installation Date: 06/2014

Cost of Plant : 8-10 Cr. (Approx.)

Fig: Asphalt Batch Mix

Plant


6. QUALITY CONTROL DEPARTMENT

Highway structures are generally constructed above the general ground level with the

following components:

a) Embankment or fill (Soil, Murrum etc.)

b) Subgrade

c) Pavement layers of flexible or rigid pavement structure

For construction of highway, quality control of the highway materials is very important. To

control the quality of materials following tests are conducted.

Table No. Test for Quality Control

Sr.

No. Title of Experiment Code

1 Marshall Test Apparatus ASTM D 1559

2 Bitumen Centrifuge Extraction -

3 Specific Gravity & Water absorption test IS:2386 Part-3

4 Aggregate Impact value test IS:2386 Part-4

5 Flexural strength test IS:516

6 Los Angeles abrasion value test IS:2386 Part-4

7 Digital compression test machine IS:516

8 California Bearing Ratio Test IS:2720 Part-16

9 Slump Test IS:1199

10 Free Swell Index (FSI) test IS:2720 Part-40

11 Atterberg’s Limits test IS: 2720 Part-5

12 Cone Penetration Test IS: 2720 Part-5

13 Flakiness & Elongation Index(FI & EI) IS: 2386 Part-1

14

The desirable properties of soil as a highway material are:

a) Stability

b) Incompressibility

c) Permanency o strength

d) Minimum changes in volume and stability under adverse conditions of weather and ground

water.

e) Good drainage and

f) Ease of compaction

Tests on Soil:

A) Index Properties of soil

a) Water content

b) Specific gravity


c) Particle size distribution

d) Consistency Limits

e) In-situ density

f) Density index

B) Soil compaction

C) Evaluation of Soil Strength

D) California Bearing Ratio (CBR) test

E) Plate Bearing Test

Desired properties of road aggregates may be summarized as follows:

a) Resistance to impact or toughness.

b) Resistance to abrasion or hardness.

c) Resistance from getting polished or smooth/slippery.

d) Resistance to crushing or crushing strength.

e) Good shape factor to avoid too flaky and elongated particles of coarse aggregates.

f) Resistance to weathering or durability.

g) Good adhesion or affinity with bituminous materials in presence of water or less stripping

of bitumen coating from the aggregate.

Tests on road aggregates:

Test which are generally carried out for judging the desirable properties and suitability of stone

aggregates are listed below:

a) Aggregate Impact Test (to assess the toughness or resistance to impact)

b) Los Angeles abrasion test (to evaluate the hardness and also toughness)

c) Polished stone value test or accelerated polishing test.

d) Aggregate crushing test(strength characteristics)

e) Shape tests-Flakiness index, Elongation Index, & Angularity Number.

f) Soundness test or durability test or accelerated weathering test

g) Specific gravity test and water absorption test.

h) Bitumen adhesion test or stripping value test of aggregates

All the above mentioned properties of aggregates and tests need not necessarily be conducted: the

tests may be decided based on the type of pavement, the pavement layer, importance of the road and

location including climatic factors. Some of the important properties and tests that are conducted on

road aggregate are given here.

Test on Bitumen:

Various tests that are generally carried out to evaluate the properties of bitumen binders are:

i) Penetration test

ii) Viscosity tests

iii) Ductility test

iv) Softening point test

v) Specific gravity test

vi) Flash and fire point tests


vii) Loss on heating tests

viii) Solubility test


7. CALIFORNIA BEARING RATIO (CBR)

The California Bearing Ratio test was developed by the California State Highway Department as a

method of evaluating the strength of subgrade soil and other pavement material for the design and

construction of flexible pavements. The CBR test denotes a measure of resistance to penetration of a

soil or flexible pavement material, of standard plunger under controlled test conditions. The CBR test

may be conducted in the laboratory generally on re-moulded specimens; the test may also be

conducted on undisturbed sample soil specimens. The laboratory test procedure should be strictly

adhered if high degree of reproducibility is desired. Procedure for field determination of CBR value

of soil in-place or in-situ has also been developed and standardized by different agencies including

the BIS.

The basic principle in CBR test is by causing a cylindrical plunger of 50 mm diameter to

penetrate into the specimen of soil or pavement component material at a rate of 1.25 mm per minute.

The loads required for 2.5 mm and 5.0 mm penetration of the plunger into the soil/material tested are

recorded. The CBR value of the material tested is expressed as a percentage of standard load value in

a standard material. The standard load values have been established based on a large number of tests

on standard crushed stone aggregate at the respective penetration levels of 2.5 and 5.0 mm. These

standard load values given below may directly be used to compute the CBR value of the test

material.

Table: Standard load values on crushed aggregate for specified penetration values

Penetration , mm Standard load, kg Unit standard load, kg/cm2

2.5 1370 70

5.0 2055 105

Determination of CBR value in the laboratory

The laboratory CBR apparatus consist of mould 150 mm diameter with a base plate and a

collar, a loading frame with the cylindrical plunger of 50 mm diameter and dial gauges for

measuring the expansion on soaking and the penetration values CBR test set up is shown in fig:

CBR Apparatus


The specimen in the mould is compacted to a dry density corresponding to the minimum state

of compaction likely to be achieved in practice. In the absence of the information the specimen may

be compacted to a maximum dry density at the Optimum Moisture Content (OMC). IS heavy

compaction as per IS: 2720 Part VIII is preferred for high trafficked roads like national and state

highways; however IS light compaction as per IS 2720 Part-VII may be adopted for low volume

roads. The specimen is subjected to four days soaking and the swelling and water absorption values

are noted. The surcharge weight is placed on the top of the specimen in the mould and the assembly

is placed under the plunger of the loading frame as shown in fig: The load values are noted

corresponding to penetration values of 0.0, 0.5, 1.0, 1.5, 2.0,2.5, 3.0, 4.0, 5.0, 7.5, 10.0 and 12.5 mm.

The load-penetration graph is plotted as shown in fig: Alternatively the load values may be converted

to pressure values and plotted against the penetration values.

The CBR value is calculated using the relation:

CBR(%)

=Load (or pressure) sustained by the specimen at 2.5 or 5.0 mm penetration

Load (or pressure)sustained by standard aggregates at the corresponding penetration levelx100

The CBR test is essentially an arbitrary strength test and hence cannot be used to evaluate the

soil properties like cohesion or single of internal friction or shearing resistance. Unless the test

procedure is strictly followed, dependable results cannot be obtained. Presence of coarse grained

particles would result in poor re reproducibility of CBR test results. Material passing 20 mm sieve is

only used in the test.

Applications of CBR test in flexible pavement design

Several agencies in different countries have standardized have standardized CBR test method

have developed charts for the design of flexible pavements for roads and runways based on CBR

values of subgrade soil and other pavement materials. CBR test as well as CBR method of flexible

pavement design are simple and the performance studies of these pavements have been extensively

investigated and found to be generally satisfactory. The Indian Roads Congress (IRC) has

standardized the guidelines for the design of flexible pavements based on CBR test (vide IRC: 37-

2001) and this method is being followed for the design of flexible pavements for all the categories of

roads in India.


8. MARSHALL MIX DESIGN

Layer: DBM (Dense Bituminous Macadam) Layer Thickness: 80mm

TEST PROCEDURE:

1. The coarse aggregates, fine aggregates and the filler material are proportioned and mixed in

such a way that final gradation of the mixture is within the range specified for the type of

bituminous mix.

2. Approximately 4500 gm. of the mixed aggregates and the filler are taken and heated to a

temperature of 175 to 190 ̊C.

3. The bitumen is heated to a temperature of 121 to 145 ̊C.

4. The required quantity of the first trial percentage of bitumen (say, 3.5 or 4.0 percent by weight

of aggregates) is added to the heated aggregates.

5. It is thoroughly mixed at the desired temperature of 154 to 160 ̊C.

6. The mix is placed in a pre‐heated mould and compacted by a rammer (10.2 kg) with 112 blows

on either side at temperature of 138 to 149 ̊C

7. Three or four specimens may be prepared using each trial bitumen content.

8. The compacted specimens are cooled to room temperature in the mould and then removed

from the molds using a specimen extractor.

9. The diameter and mean height of the specimen are measured.

10. The weight of each specimen in air and suspended in water is determined.

11. The specimens are kept immersed in water in a thermostatically controlled water bath at 60 ±

10 ̊C for 30 to 40 minutes.

12. The specimens are taken out one by one.

13. The specimen is placed in the Marshall Test head.

14. It is then tested to determine Marshall Stability Value which is the maximum load before

failure and the Flow value which is the deformation of the specimen up to the maximum load.

15. The corrected Marshall Stability value of each specimen is determined by multiplying the

proving ring reading with its constant.

16. If the average thickness of the specimen is not exactly 63.5 mm, a suitable correction factor is

applied.

Marshall Stability Apparatus

Mould


17. The above procedure is repeated on specimens prepared with other values of bitumen contents

in suitable increments; say 0.5 percent, up to about 6 percent.

CALCULATIONS:

I. DENSITY AND VOID ANALYSIS:

i. Voids in Mineral Aggregates (VMA):

VMA =Vv + Vb

Where, Vv =Volume of air voids in compacted mass

Vb =Volume of the bitumen in compacted mass

ii. Voids Filled with Bitumen (VFB):

VFB in percentage = Vb

VMA x 100

VFB in percentage = Vb

Vv+Vb x 100

II. SPECIFIC GRAVITY:

i. Bulk Specific Gravity of Bituminous mix(Gb):

Gb =Weight in Air

Weight in air−Weight in Water

ii. Theoretical Specific Gravity of Bituminous mix(Gt):

Gt = 100

W1G1

+W2G2

+W3G3

+W4G4

Where, G1, G2, G3, G4 are apparent specific gravity of coarse aggregates,

fine aggregate, filler, and bituminous binder respectively.

Where, W1, W2, W3, W4 are percent by weight of coarse aggregate, fine

aggregate, filler and bituminous binder respectively.

III. VOLUME:

i. Volume of Air Voids (Vv):

Vv = Gt−Gb

Gt x100

ii. Volume of Bitumen (Vb):

Vb = W4

G4 x Gb


OPTIMUM BITUMEN CONTENT (OBC)

The optimum bitumen content (OBC) for the mix design is found by taking the average value

of the following three bitumen contents found from the graphs of the rest results.

1. Bitumen content corresponding to maximum stability.

2. Bitumen content corresponding to maximum unit weight.

3. Bitumen content corresponding to the median of designed limits of percent air voids

in total mix (5%)

The Marshall Stability value, Flow value and percent voids filled with Bitumen at the average

value of bitumen content are checked with the Marshall Stability design criteria/specification.

Note: All data relevant to Marshall Stability test are attached at the end of this report in the form of tables.


9. HIGHWAY DEPARTMENT

9.1 Steps for Construction of a New Highway:

Construction for highway construction on embankment

The various steps involved in the construction of a highway are listed below.

(i) ‘Clearing and grubbing’ to remove the vegetation, roots and other organic matter along the

alignment up to the bottom width of the embankment and the side drains.

(ii) Re-compaction of the ground that supports the embankment to the specified density.

(iii) Selected soil is spread and compacted in layers to form the embankment as specified.

(iv) Selected soil is spread and compacted in layers to form the subgrade.

(v) Excavation for cross drainage structure.

(vi) Laying of drains layer-cum granular sub-base course in layers, over the subgrade.

(vii) Building up the shoulders in layers.

(viii) In the case of flexible pavements, construction of base course in layers; in the case of rigid

pavements, construction of lean concrete base course.

(ix) In the case of flexible pavements, construction of bituminous binder and surface course

layers; in the case of rigid pavements construction of cement concrete slab and the

specified joints.

(x) Finishing works as specified.

9.1.1 Design elements of highway embankment

The following design elements are to be considered before constructing a highway embankment:

(a) Height

(b) Fill material

(c) Settlement

(d) Stability of foundation &

(e) Stability of slope

9.1.2 Construction of Flexible Pavements:

Components of flexible pavements:

The typical cross section of flexible pavement for roads with heavy traffic is shown in fig:

The components layers of a flexible pavement laid over the subgrade are:

a) Granular sub-base and drainage layer

b) Granular base course

c) Bituminous binder course

d) Bituminous surface course


Table: Thickness of Pavement Layers.

9.2 Construction of Highway Embankment

Materials for highway embankment

Materials considered suitable for construction of embankment are soil, moorum, gravel and a

mixture of these which are free from organic matter such as stumps, roots, rubbish or such organic

ingredients likely to decay or deteriorate. The maximum permissible size of coarse material or stone

aggregate for the construction of embankment or fill is 75 mm.

The essential requirement of soil properties considered suitable for highway embankment

construction as per IRC specifications are given under:

(i) Liquid limit to be less than 70 percent.

(ii) Plasticity index to be less than 45.

(iii) Free swell index (FSI) to be less than 50 percent.

(iv) Maximum laboratory dry density on compaction as per IS:2728-Part 8 (IS heavy

compaction or Modified Proctor compaction ) to be not less than: (a) 152 kg/m3 for

embankments of height up to 3.0 m and (b)160 kg/m3 for embankments of height more

than 3.0 m

The soil that do not fulfill any of the above four requirements are not suitable for construction of

highway embankment. The general soil types that are considered not suitable for embankments

construction are peat, marshy and swampy soils, logs, stumps and all perishable and combustible

materials. These soils belong to classification groups OL, OI, OH, and Pt as per BIS soil

classification. Also soils containing soluble sulphate (expressed as SO3) extent exceeding 0.5

percent by weight are considered are considered unsuitable.

Fly ash fulfilling properties as per the IRC guidelines may also be used for the construction of

highway embankment.

The steps for the construction of highway embankment are given below:

(i) The selected soil in loose condition is spread to uniform thickness using appropriate

equipment over the prepared ground; the thickness of the loose soil is decided so as to

obtain the specified compacted thickness of the layer, determined during ‘proof rolling’.

(ii) Additional water as required is sprayed so as to obtain the OMC of the soil determined

from the laboratory compaction tests. However in rare situation if the field moisture

content of the soil happens to be higher than the OMC, it may be necessary to delay the

construction until the soil dries to the level of optimum moisture content before further

compaction.

Sr. No. Name of layer Thickness (in mm)

1. Subgrade 500

2. GSB (Granular Sub Grade ) 200

3. WMM (Wet Mix Macadam ) 250

4. DBM (Dense Bituminous Macadam) 75/80

5. BC (Bituminous Concrete) 40


(iii) The soil with the added water is mixed thoroughly using appropriate equipment so that

the water gets disturbed in the soil layer uniformly; the mixed soil is spread again to

uniform layer thickness.

(iv) The soil layer is compacted by rolling using the selected equipment so as to obtain the

specified density.

(v) After ensuring that the layer has been compacted to the desired density, the next layer of

the soil is spread over the already compacted layer, water added, mixed and compacted as

mentioned in steps (a) to (d) above. The process is repeated until the desired height of the

embankment is achieved.

Quality control checks during construction of highway embankment

(i) The representative soil sample collected from the borrow area for the construction of

highway embankment is subjected to relevant laboratory tests so as to check the values of

liquid limit, the plasticity index, free swell index, soluble sulphate content, organic matter

and the compacted density. If the soil fulfills the specified requirements, the use of this is

approved for use in the construction.

(ii) Laboratory compaction test (by BIS heavy compaction) is carried out to determine the

optimum moisture content (OMC) and maximum dry density of the soil.

(iii) The field moisture content of the loose soil after spreading to the desired thickness is

determined by any rapid test method, so as to decide the extra quantity of water to be

added to bring up to the OMC of the soil.

(iv) After adding the additional water as required and mixing thoroughly, the moisture content

is again checked by a rapid method to ensure that the OMC is achieved.

(v) After the soil layer is adequately rolled, the field density and moisture content are

determined by one of the approved methods; in case the average dry density achieved is

less than the specified value ( of 95 % of standard density), further rolling is carried out

until the desired density is achieved.

(vi) The steps (iii) to (v) are repeated for each subsequent layer.

(vii) If the soil type used for construction is different at another stretch, the tests specified

under (i) and (ii) are also to be repeated to ensure that the new soil fulfills the specified

requirements.

The Indian Roads Congress (IRC) and the Ministry of Road Transport and Highways (MORTH)

have specified the minimum number of tests to be conducted per unit volume of soil for the

purpose of quality control during the construction of highway embankments, in their respective

books of specifications. The dry density of the each compacted layer is checked at the rate of one

or two samples per 1000 m2 compacted area or as specified.

9.3 Construction of Granular Sub base Course/ Drainage Layer

Objects

A granular sub-base (GSB) course is laid in between the subgrade and the base course of all

highway pavements, in one or more layers. The GSB layer should be laid over the full width of

the prepared subgrade, extending up to the side drains so as to save as a ‘drainage layer’ of the

pavement, if another separate drainage layer is not provided.


In flexible pavements of highways, the GSB layer performs the following two important

functions:

i) To serve as an effective drainage layer to drain off the water entering into the pavement

layers, leading to the longitudinal road side drains such that only a very small proportion of

water enters into the subgrade. The water entering the pavement layers may partly consist of

surface water which enters through the surface course and the rest of water which enters

through the earth shoulders and earth median of divided highways.

ii) To serve as a structural component of the flexible pavement structure by distributing the

wheel load stresses transmitted through the surface course and granular base course, to a still

larger area before passing on the compressive stresses on the top of the subgrade.

Therefore the GSB-cum-drainage layer serves as an essential component of flexible highway

pavements. However in the case of rigid pavements of highways, the GSB layer serves only as an

effective drainage layer, as the magnitude of load stresses transmitted on the GSB layer will be

negligibly small.

9.3.1 Materials for GSB layers:

The materials used for the construction of the GSB layer are, (i) crushed stone aggregates (ii)

gravel (iii) coarse sand and(iv) Selected soils such as moorum with less fines and very low plasticity.

The material should not contain organic matter or other deleterious constituents. Different grading’s

of GSB materials have been suggested in the MORTH Specifications. The specified requirements of

materials used for GSB layer as under:

a) Passing 0.425 mm sieve shall have liquid limit less than 25 % and plasticity index less than

6%

b) Fines passing 0.075 mm sieve, less than 10%

c) CBR value not less than 30% for important highways with heavy traffic and not less than 25

or 20 percent in other cases.

Based on performance studies of flexible pavements in several parts of the country it is found

that it is desirable to select the materials for GSB-cum-drainage layer which fulfill the following

requirements: (a) proportion of fines passing 0.075 mm sieve to be minimum, but not to exceed

5.0 percent (b) plasticity index to be preferably zero, (c) coarse graded material so as to provide

good drainage characteristics with high permeability in the order of 30 m per day or higher.

9.3.2 Construction Method

The GSB layer is constructed on the top of the prepared subgrade; therefore first the surface

of the subgrade in checked and grass and vegetation if any, are removed. The grade and cross

slope of the top surface of the surface of the subgrade are corrected as required. The construction

steps are given below:

(i) The sub-base material is spread to uniform thickness and specified cross slope using a

motor grader by adjusting the blade of the grader

(ii) The moisture content of the material is checked and the additional quantity of water

required to bring up to the optimum moisture content is sprinkled at an uniform rate using

a truck mounted sprinkler.

(iii) The watered material is mixed properly using machinery such as disc harrows and

rotavators.

(iv) The mixed material is spread to the desired thickness, grade and camber using a motor

grader with hydraulic controls of the blade.


(v) The loose GSB layer is compacted by rolling; if the compacted thickness of the layer is

100 mm or lesser, an ordinary smooth wheeled rollers may be used; for compacted

thickness exceeding 100 mm and up to 225 mm, compaction is done by vibratory roller

of static weight 10 tonnes or more; pneumatic tyred roller of appropriate gross load and

tyre pressure may also be used if the type of materials selected can be effectively

compacted by this equipment.

(vi) Rolling is done starting from the lower edge and proceeded towards the center of the

undivided carriageway or towards the upper edge of the divide carriageway or towards

the upper edge of the divided carriageway, with a minimum one third overlap between

each runoff the roller; the rolling speed is limited to less than 5 kmph.

(vii) Rolling is continued till at least 98 percent of maximum density of the materials

(for heavy compaction as per IS: 2720: Part 8) is achieved.

Quality Controls checks during the construction of the granular sub-base course

(i) The representative samples of GSB materials collected from each source are subjected to

relevant laboratory tests to check the values of liquid limit, plasticity index, gradation and

deleterious constituents; if the requirements are fulfilled, the material is approved.

(ii) Laboratory compaction test ( by BIS heavy compaction ) is carried out to determine the

optimum moisture content (OMC) and maximum dray density (MDD)

(iii)The CBR value of the selected materials is determined in laboratory.

(iv) The field moisture content of the material is determined prior to compaction by any rapid test

method and the extra quantity of water to be added to bring up to the OMC is estimated.

(v) After rolling, the field density and moisture content are determined by one of the approved

methods to ensure that the dry density achieved is not less than 98% of laboratory density.

(vi) The steps (iv) and (v) are repeated for each subsequent layers.

(vii) The finished surface levels of the sub-base course are checked with reference to

desired longitudinal and cross profile of the road (shown in the drawing); if these are found to

exceed the permissible tolerance of (-20 mm and +6 mm), the appropriate correction are

made by removing or adding the part of the material on the surface and by further rolling.

The Indian Roads Congress (IRC) and the Ministry of Road Transport and Highways

(MORTH) have suggested the number of tests to be conducted per specified unit volume of

material mentioned under (i)above for the purpose of quality control of the GSB materials.

Minimum of one moisture content test is to be carried out per 250 m2 area and minimum of one

density test per 500 m2 are on each compacted layer.

9.4 Construction of Granular Base Course

Types of base course materials used in flexible pavements

The common types of base course materials used in India for the constructions of flexible pavement

are ‘Wet Mix Macadam’ (WMM), ‘Water Bound Macadam’ (WBM), soil-aggregate mixes and

stabilized soil mixes.

The flexible pavements of most of the important highways are being constructed these days

using WMM as the base course. However in India, vast majority of old highways and other district

roads constructed up to the 1980’s have WBM in the base course of flexible pavements. Even now

this method of construction of flexible pavements of less important roads carrying moderate to low

traffic. This is mainly because WBM construction is labour intensive method and does not require

construction machinery except a road roller of 8 to 10 tonnes weight.

There various other types of base course materials that can be used in the base course or

lower layer of the base course of flexible pavements; these include ‘Crusher-run-Macadam’, and also


different types of aggregate, soil-aggregate mixes or soils stabilized using different types aggregate,

soil-aggregate mixes or soils stabilized using different types of stabilizers. Several chemical

stabilizers are being effective.

9.5 Construction of Wet Mix Macadam base

Material

Wet Mix Macadam (WMM) base consist of a well graded hard crushed aggregates and adequate

proportion of water mixed thoroughly in a mixing plant; the wet mix is spread over the prepared sub-

base course with a mechanical paver and rolled to a dense mass. The thickness of each compacted

layer depends on the type of roller used; however the minimum and maximum thickness of each

compacted have been specified as 75 and 200 mm respectively. Crushed stone aggregates fulfilling

the following physical properties are used;

Los Angele’s abrasion value : less than 40 percent,

Or

Aggregate impact value : less than 30 percent

Combined flakiness and elongation index : less than 30 percent

Plasticity index of material finer than 0.425 mm sieve : less than 6.0

Two different grading requirements have been suggested for use in WMM layers as given in

table: to be adopted depending on the thickness of each compacted layer.

Table: Grading requirement of aggregate for wet mix macadam

Sieve size,

mm

Passing the sieve, percent by

weight

Grading-I Grading-II

53.00 100 -

45.00 95 to 100 -

26.50 - 100

22.40 60 to 80 50 to 100

11.20 40 to 60 -

4.75 25 to 40 35 to 55

2.36 15 to 30 -

0.06 8 to 22 10 to 30

0.075 0 to 8 2 to 9

Construction steps:

(i) Compaction test is carried out in the laboratory using the selected grade of WMM

material, after removing the fraction of aggregate retained on 19mm sieve and replacing

it with material passing 19 mm sieve and retained on 4.75 mm sieve. The optimum

moisture content of the WMM mix is determined in the laboratory under heavy

compaction.

(ii) The selected WMM mix (with water equal to the optimum moisture content added) is

prepared in a suitable mixing plant like the ‘pug mill’.

(iii) The WMM mix is transported to the site and is spread using a self-propelled type paver-

finisher machine, to the required thickness, grade and cross slope.

(iv) The WMM layer is compacted using a vibratory roller of minimum static weight of 10

tonnes, the compacted thickness of each layer should be less than 200mm. Rolling is

done starting from the lower edge and proceeded towards the center of the divided

carriageway, with a minimum one third overlap between each run of the roller; the rolling

speed is limited to less than 5 kmph.


(v) If the total design thickness of WMM base course is say 250 mm, the base is constructed

in two layers, each of compacted thickness 125 mm. after compaction of the first layer,

the second layer is laid by a mechanical paver-finisher(Preferably by a sensor-paver)and

compacted by a vibrator roller as mentioned in steps (iii) and(iv) above.

(vi) The WMM surface is checked for defects, if any and allowed to dry weather, the

preparation for laying a bituminous pavement layer may start by applying the prime coat.

Quality control check during the construction of WMM base course:

(i) The samples of coarse aggregates controlled are subjected to relevant laboratory tests to

check the values of Los Angeles abrasion value or aggregate impact value, combined

flakiness and elongation index. (ii) Plasticity index (PI) is checked on the fraction of the mixed aggregate that pass 0.425

mm sieve. (iii) The gradation of the combined mix of coarse and fine aggregate is checked.

(iv) Laboratory compaction test (by BIS heavy compaction) is carried out on the selected

mixed aggregates to determine the OMC and MDD (maximum dry density).

(v) The moisture content of the WMM mix is determined while being fed into the mechanical

paver to ensure that it is within the permissible limits of the OMC.

(vi) The filed density and moisture content of the compacted WMM layer are determined by

one of the approved methods to ensure that the dry density achieved is not less than 98

% of standard laboratory density. (vii) The steps (v) and (vi) are repeated for each subsequent WMM layer.

(viii) The finished surface levels of the WMM base coarse are checked with reference to

desired longitudinal and cross profile of the road; if these are found to exceed the

permissible tolerance of (+10 mm and -10 mm), the affected area is scarified (not less

than 5m in length and 2m in width), reshaped with added premix and re-compacted by

rolling.

The Ministry of Road Transport and Highways (MORTH) have suggested that minimum of one

set of aggregate impact, flakiness index and elongation index tests are to be conducted per 200m3

of aggregate and the grading of the mixed aggregates to be checked at one test per 100 m3 of

aggregates; minimum of one density test per 500 m2 on each compacted layer is also to be

carried out.

General Approach for the Construction of Bituminous Pavement Layers:

Types of bituminous pavement layers:

Bituminous pavement layers from an important part of the flexible pavement layers system.

Different types of bituminous layers are being used as surface course of flexible pavement. Thin

bituminous surfacing is provided on roads with light traffic loads; thicker bituminous layers are

needed to withstand heavier traffic loads, additional bituminous pavement layers in the form of

‘binder course’ or ‘base course and binder course’ are laid before laying the bituminous surface

course.

It is essential to provide an appropriate type of ‘interface treatment’ before laying any type of

bituminous layer over another layer. If the bituminous layer is to be laid over an existing bituminous

surface, the interface treatment consists of application of both ‘prime coat’ and ‘tack coat’. If the

bituminous layer is to be laid over an existing bituminous surface, the interface treatment consists of

application of only tack coat.

Different types of bituminous base course that have been used in India are: (i) Bituminous

Macadam (ii) Penetration Macadam and (iii) Built-up Spray Grout.


Different types of bituminous binder coarse that have been in use are: (i) Bituminous

Macadam and (ii) Dense Bituminous Macadam.

Different types of thin bituminous surface course that are being used in this country on roads

with low to moderate traffic volume are (i)Bituminous Surface Dressing (ii) Open-graded Premix

Carpet with Seal Coat (iii) Close Graded Premix Surfacing or Mixed Seal Surfacing.

Thick layer of high quality bituminous surfacing being laid in India generally consist of 40 or

50 mm layer of ‘Bituminous Concrete’ laid over one or more layers of ‘Dense Bituminous

Macadam’ binder course, partially on important roads carrying heavy wheel loads.

Apart from the above conventional types of bituminous surface courses, special types of

surfacing such as ‘Bitumen Mastic’ wearing course is being made use of on certain critical locations

such as bridge decks and also at certain selected stretches of roads.

Preparation before constructing a bituminous layer over granular base course:

The preparations required before constructing a bituminous pavement layers over a granular

base course are given briefly in the following steps:

(i) The surface of the granular pavement layer/base course is checked for defects such as

depressions, inadequate cross slope, etc. and these are rectified.

(ii) The surface is thoroughly cleaned free of dust and loose materials.

(iii) Prime coat is applied by spraying liquid bituminous binder of low viscosity like bitumen

emulsion of appropriate grade.

(iv) After curing of the primed surface, a tack coat is applied by spraying liquid bituminous

binder of low viscosity.

The construction of the desired type of bituminous pavement layer is taken up on this prepared

surface, soon after the application of the tack coat.

Preparation before laying a bituminous pavement layer over existing bituminous layer:

Preparations required before laying a bituminous pavement layer over existing bituminous layer are

briefly given in the following steps:

(i) The existing bituminous surface is carefully checked to identify various types of defects

such as pot-holes, different types of cracks and defects of the surface profile such as

depressions, ruts or inadequate cross slope.

(ii) The pot-holes are patched as specified.

(iii) The areas with wide cracks and alligator type cracks are cut and removed and patched.

(iv) Cracks sealing is done on the areas where fine and medium cracks have developed.

(v) The defects of surface profile are corrected by laying a ‘profile corrective course’ using a

suitable type of bituminous mix.

(vi) The surface is thoroughly cleaned using a mechanical broom or brushes to remove dust

and loose particles.

(vii) Tack coat is applied using liquid bituminous binder of low viscosity.

The construction o the desired type of bituminous pavement layer is taken up on this prepared

surface, soon after the application of the tack coat.


Prime Coat:

Objectives

Spraying of liquid bituminous binder of low viscosity over a granular or non-bituminous surface is

called application of prime coat or ‘priming’; this is an important part of preparation before laying a

bituminous pavement layer over a granular base course. The objective of priming a granular surface

are to: (i) penetrate deep into the surface and plug or seal the voids on the surface (ii) coat and bond

the loose particles on the surface (iii) render the surface of the base course water resistant and (iv)

permit the tack coat to be applied over the primed surface to provide proper adhesion between the

base and the bituminous pavement layer constructed above the treated granular base.

Type and quantity of materials for prime coat:

Cationic bitumen emulsion of SS-1 grade (Slow setting type) or medium curing cutback

bitumen may be used for priming. The specified rate of application of the bitumen emulsion prime

coat over WMM and WBM base is 0.7 to 1.0 kg/m2; the rate of application may be 0.9 to 1.2 kg/m2

for soil stabilized base.

When cutback bitumen is used for priming, 0.6 to 0.9 kg/m2 of MC-30 grade of cutback may

be applied over WMM and WBM base course; the rate of application of MC-70 grade may be 0.9 to

1.2 kg/m2 for soil stabilized base.

The most appropriate quantity of primer to be applied on the granular base course can

actually be decided at the site by the engineering based on the maximum quantity of the binder that

can be absorbed by the receiving surface without resulting in ‘run-off ’.

Method of application of primer:

The binder of the base course is swept clean and made dust free. If bitumen emulsion is used as

primer, no heating of the binder shall be done; the surface of the granular base shall be slightly damp.

Since emulsion contains fine bitumen particles suspended in water, generally, there is no need to add

water to the emulsion, before it is sprayed on the surface. The drums are to be roller few times, so

that the emulsion in homogeneous when applied on the surface. The primer is sprayed uniformly at

the specified rate using a pressure sprayer.

It cutback bitumen is applied as primer, the base course shall be fully dry and the primer is sprayed

uniformly at the specified rate using a pressure sprayer.

The primed surface is allowed to cure for a minimum of 24 hours; traffic shall not be allowed over

the primed surface. After curing, the tack coat is applied and this is followed over the primed surface.

After curing, the tack coat is applied and this is followed by laying of the required bituminous

pavement layers.

Quality control test on prime coat:

(i) Test on quality of bituminous binder, as specified by the BIS.

(ii) Temperature of application of the binder, at regular intervals.

(iii) Checking rate of spread of the binder at one test per 1000 m2 area subjected to minimum

two tests per day; this is done using a set of three metal plates of size 200x200 mm placed


at 10 m intervals between the wheels of the bitumen distributer while spraying the prime

coat and finding the average weight of the binder on the plates.

Tack Coat:

Objectives

Tack coat is application of a small quantity of liquid bituminous binder of low viscosity over

either a primed granular surface or over an existing bituminous or cement concrete surface.

Application of tack coat is also an important part of preparations before laying a bituminous

pavement layer over any other pavement layer .The main objective of tack coat is to provide

adequate interface bond between the receiving pavement surface and the new bituminous layer

being overlaid. The binder of the tack coat is not expected to penetrate into the pavement surface

and plug the voids.

Type and quantity of materials of tack coat:

Cationic bitumen emulsion of grade RS-1(Rapid setting type) or suitable paving bitumen of

low viscosity such as VG-10 grade bitumen may be used as tack coat material. For emergency

construction at sites where the atmosphere temperature during paving is at or below freezing

point (0 o C), cutback bitumen of RC-70 grade may be used as tack coat material.

The specified rate of application of bituminous emulsion tack coat on (a) bituminous surface

is 0.2 to 0.3kg /m2 (b) granular surface treated with primer is 0.25 to 0.30 kg/m2 and (c) cement

concrete pavement surface is 0.30 t o0.35 kg/m2.

The specified rate of application of VG-10 grade paving bitumen tack coat on (a) bituminous

surface is 0.3 to 0.4 kg/m2 (b) granular surface treated with primer is 0.35 to 0.45 kg/m2 and (c)

cement concrete pavement surface treated with primer is 0.4 to 0.5 kg/m2

Method of application of tack coat:

The recommended spraying temperature of RS-1 grade bituminous emulsion is 20 to 70 oC;

the bituminous emulsion shall not be heated. The bituminous emulsion is sprayed uniformly over the

clean receiving surface at the rate as specified above. The bituminous emulsion tack coat is cured by

allowing is to break, indicated by the color turning from chocolate to black; the bituminous layer is

placed over this surface soon after.

If VG-10 grade paving bitumen is used, it is heated in a bitumen boiler to the application

temperature to achieve the desired viscosity of less than 2.0 poise. The heated bitumen binder is

sprayed uniformly over the dust-free receiving surface at the specified rate, as given above. The

bituminous layer may be placed immediately over this tack coat.

Quality control tests on tack coat:

(i) Tests on quality of bituminous binder, as specified by the BIS.

(ii) Temperature of application of the binder, at regular intervals.

(iii)Checking rate of spread of the binder at least one test per 1000m2 area subject to

minimum two tests per day; this may be done using a set of three metal plates of size


200 x 200 mm placed at 10 m intervals between the wheels of the bitumen distributer

while spraying the tack coat and finding the average weight of the binder on the plates.

Dense Graded Bituminous Mixes

General features

Dense graded bituminous mixes are prepared using well graded aggregate, suitable filler material and

appropriate type, grade and proportion of bitumen binder under controlled conditions. These dense

graded bituminous mixes are designed in the laboratory to strictly fulfill the specified properties and

requirements that control the stability and durability under the expected traffic, climatic and

environmental conditions.

Most commonly used dense graded, stiff bituminous pavements layers in this country are the

‘Dense Bituminous Macadam’ binder course and ‘Bituminous Concrete’ surface course.

The IRC has suggested the use of dense graded bituminous mixes in the following three types

flexible pavement layers of highways with heavy to very heavy traffic.

(a) Dense Bituminous Macadam(DBM) to be used as a strong binder course or as overlay along

with suitable dense graded surface course for strengthening existing pavement; the DBM

layers are to be laid as a single or in multiple layers, each of thickness 50 to 100 mm.

(b) Semi-Dense Bituminous Concrete (SDBC) wearing course of thickness 25 or 40 mm laid in

single layer.

(c) Bituminous Concrete (BC) surface course layers of thickness 25 or 40 or 50 mm laid in single

layer.

Materials

The materials required for the construction of dense bituminous mixes are: (i) bitumen binder of

appropriate type and grade, (ii) coarse aggregate and fine aggregate fulfilling the specified properties

and gradation and (iii) suitable filler material. It is essential to carry out the ‘mix design’ of the dense

graded bituminous mix in the laboratory, making use of the actual gradation of the coarse and fine

aggregates collected at site of the hot mix plant in order to specify the optimum bitumen content for

the design-mix and the ‘job mix formula’ to be used at the construction site.

The IRC has outlined the specifications for the component materials as well as the

bituminous mix design requirements to be used for the above three types of pavement layers, namely

DBM, SDBC, and BC. The suggested grading of the aggregates to be used for the three types of

pavement layers and the minimum specified bitumen content slightly differ; all other materials

specifications and mix design requirements are the same.

Bitumen binder

The grade of paving grade bitumen binder to be used for the construction of all the three types of

dense graded bituminous mixes (DBM, SDBC, and BC) is decided based on: (a) the lowest daily

mean air temperature and (b) the highest daily mean air temperature at the project site. The criteria

for selecting the grade of paving bitumen recommended by the IRC are presented in table: Apart

from these paving grades of bitumen, modified bituminous binders such as polymer modified


bitumen (PMB), natural rubber modified bitumen (NRMB) and crumb rubber modified bitumen

(CRMB) of appropriate grades may also be used for dense graded bituminous mixes.

Table: Recommended criteria for deciding the grade of paving bitumen

Lowest mean air

temperature, 0C

Highest daily mean air temperature, 0C

Less than 20 0C 20 to 30 0C More than 30 0C

More than -100C VG-10 VG-20 VG-30

-100C, or lower VG-10 VG-10 VG-20

Aggregates

The course aggregate to be used in the dense graded mixes are obtained from hard variety of crushed

rock/stones or crushed gravel; the aggregates of cubical shape free from dust and other deleterious

materials are preferred for the construction of dense graded bituminous mixes. The aggregates shall

fulfill the physical requirements specified by the IRC, as given under:

Aggregate impact value, or : less than 24 percent

Los Angles abrasion value : less than 30 percent

Flakiness and elongation index (combined) : less than 35 percent

Soundness: loss with sodium sulphate, 5 cycle, or : less than 12 percent

loss with magnesium sulphate, 5 cycles : less than 18 percent

Water absorption : less than 2.0 percent

Adhesion: retained bitumen coating : more than 95 percent

Water sensitivity: retained tensile strength : more than 80 percent

Polishing: Polished stone value (for surface course only): more than 55

Fine aggregate consist of crushed mineral material passing 2.36 mm sieve and also some natural sand

not exceeding 50 percent.

Course and fine aggregate are mixed so as to obtain the specified dense graded mixes for DBM,

SDBC, and BC mixes. The IRC has specified two grading requirements of aggregates for use in

DBM binder course: (i) Grading-1, for compacted layer thickness of 75 to 100 mm, using nominal

maximum size of 26.5 mm.

For SDBC surface course Grading-1 is specified for compacted thickness of 40 mm with nominal

maximum aggregate size of 13.2 mm and Grading-2 for thickness of 25 mm with nominal maximum

aggregate size of 9.5 mm.

Similarly for BC surface course also two gradations have been suggested: (i) Grading-1, for

compacted surface course thickness of 50 mm with nominal maximum aggregate size of 19 mm and

(ii) Grading-2 for compacted surfacing thickness of 25 and 40 mm using maximum nominal size of

13.2 mm.

The grading requirements for DBM and BC layers along with the minimum bitumen content

specified by the IRC are given in table.

The suggested grading for 40 mm and 25 mm thick SDBC surfacing are slightly different; the

minimum binder content specified are 4.5% for 40 mm surfacing and 5.0 % for 25 mm surfacing.


Table: Grading requirement of aggregate and bitumen content for DBM and BC

Specification DBM BC

Nominal maximum

size, mm 37.5 26.5 19.0 13.2

Layer thickness,

mm 75 to 100 50 to 75 50 25 to 40

IS sieve size Cumulative percentage by weight of total aggregate

passing the sieve

45.0 100 - - -

37.5 95 to 100 100 - -

26.5 63 to 93 90 to 100 100 -

19.0 - 71 to 95 90 to 100 100

13.2 55 to 75 56 to 80 59 to 79 90 to 100

9.50 - - 52 to 72 70 to 88

4.75 38 to 54 38 to 54 35 to 55 53 to 71

2.36 28 to 42 28 to 42 28 to 44 42 to 58

1.18 - - 20 to 34 34 to 48

0.60 - - 15 to 27 26 to 38

0.30 7 to 21 7 to 21 10 to 20 18 to 28

0.15 - - 5 to13 12 to 20

0.075 2 to 8 2 to 8 2 to 8 4 to 10

**Minimum

bitumen content, % 4.0 4.5 5.2 5.4

** Only the minimum bitumen contents are given here; the actual design values of bitumen content are to be determined

by Marshall Mix design method.

Mix design requirements

The dense graded bituminous mixes are designed by Marshall Method by applying 75 blows on each

face of the specimens. The designed mixes should fulfill the following mix design requirements for

use in all three types of dense graded bituminous mixes, namely DBM binder course, SDBC surface

course and BC surface course.

Marshall stability at 60 0C : not less than 900 kg or 9.0 kN

Marshall flow value : 2.0 to 4.0 mm

Marshall quotient (stability/flow) : 2.0 to 5.0

Air voids : 3.0 to 5.0 percent

Voids filled with bitumen (VFB) : 65 to 75 percent

Water sensitivity: Tensile strength ratio : not less than 80 percent

The mix design tests are carried out at the site laboratory. The designed bituminous mix should also

fulfill the specified minimum values of voids in mineral aggregates (VMA), depending on the

nominal maximum size of course aggregates and percentage air voids (vv) in the mix as given in

table: The binder content required for the design-mix is selected corresponding to 4.0 % air voids

content in the mix. All other mix design properties are checked corresponding to this binder content

whether they fulfill the specified design requirements.


Table: Requirement of minimum voids in mineral aggregates in the mix

Nominal maximum

size of aggregates, mm

Voids in mineral aggregates (VMA),

percent when:

Vv=3.0% Vv=4.0% Vv=5.0%

9.50 14 15 16

13.2 13 14 15

19.0 12 13 14

26.5 11 12 13

37.5 10 11 12


10. RIGID PAVEMENT-COMPONENTS & THEIR FUNCTIONS

Location: Ch.19+300 to Ch.19+600 (Toll Plaza)

Components of Cement Concrete Pavement & their functions:

The cement concrete pavement structure of major highways catering for heavy traffic loads

consisting of the following components, from the bottom towards the top:

(a) Soil subgrade

(b) Drainage layer

(c) Sub-base course generally constructed using lean cement concrete or ‘dry lean

concrete’(DLC)

(d) Separation membrane laid on the top of the concrete sub-base course and

(e) CC/PQC pavement slab using ‘Paving Quality Concrete’(PQC)

(f) Construction of different types of joints in CC pavements

The main features and important functions of each of these components are briefly explained in the

following paragraph.

Subgrade

The requirements and desired properties of subgrade soil and the construction details have been

presented above. CC pavements can be designed and constructed even over relatively poor or weak

subgrade soil; however, keeping in view the requirements of long service life of the CC pavements, it

is desirable to avoid the use of soils with high compressibility and plasticity characteristics in the

subgrade layer.

The subgrade should be constructed by adequately compacting the soil in layers so as to

achieve a minimum of 97 percent by ‘BIS heavy compaction’ or ‘Modified Proctor Compaction’

tests. If the soil in the subgrade (or even the fill below) is not adequately compacted, the CC

pavement is likely to non-uniform settlement, resulting in deterioration and failure of the pavement

structure.

Drainage Layer

The performance and service life of the CC pavements depends on a great extent on the effective

functioning of the drainage layer during the 30 years design period. Therefore a well designed and

constructed crushed aggregate drainage layer of thickness 200 to 300 mm with permeability not less

than 30m/day is desirable. A geo-filter layer may be laid between the subgrade and the granular

drainage layer to provide a longer service life of this drainage layer.

In the case of CC pavement, the GSB layer is mainly expected to serve as a drainage layer so

as to keep the subgrade soil in relatively dry state and to prevent stagnation of water on the subgrade.

This layer is not expected to serve as a structural member of the CC pavement system.

Sub-base course/DLC


On important highways with heavy traffic, generally a sub-base course consisting of lean cement

concrete or ‘dry lean concrete’ (DLC) is laid between the drainage layer and the CC pavement slab.

It is found that by providing an effective drainage layer and a lean cement concrete sub-base between

the subgrade and the pavement slab, it is possible to prevent the failure of the CC pavement due to

‘pumping and blowing’. Consequently the effective service life of the CC pavement is also

substantially increased.

Separation membrane

The separation membrane is spread on the top of the DLC sub-base slab before laying the CC

pavement slab. This membrane prevents the new concrete from sticking to the old lean concrete sub-

base slab and possible development of interface bond. The separation membrane enables relative

movement of the CC pavement slab with respect to the DLC sub-base due to temperature changes

and consequent warping and contraction of the pavement.

CC/PQC pavement slab

M-40 cement concrete mix (prepared in a suitable mixing plant) with a minimum flexural strength of

45 kg/cm2 is recommend by the IRC for use in the CC pavements of highways with heavy to very

heavy traffic loads. The CC pavement slab is expected to withstand; (i) the flexural stresses

developed due to the temperature differential between the top and bottom of the slab and

consequently warping of the pavement slab and (ii) the flexural stresses caused by the movement of

heavy wheel loads. The stresses caused by the movement of heavy wheel loads. Therefore high

quality CC mix with high flexural strength is used for the construction of the PQC slab of the CC

pavements.


CONCLUSION

It was a wonderful learning experience at IRB Infrastructure Developers Ltd. site of SYBOT project

(Four Laning of Solapur- Yedshi Section of NH-211 from Km. 0+000 to Km. 100+000 on DBFOT

basis under NHDP Phase-IV) for one month. I gained a lot of insight regarding almost every aspect

of site. I was given exposure in almost all the departments (namely Structural Dept., Highway Dept.,

Surveying Dept., Quality Control Dept.,) on the site. The friendly welcome from all the employees is

appreciating, sharing their experience and giving their peace of wisdom which they have gained in

long journey of work. I hope this experience will surely help me in my future and also in shaping my

career.

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