pavement design and construction

8/11/2019 Pavement Design and Construction

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HIGHWAY CONSTRUCTION

IRC: 58 - 2002, Guidelines for the design ofPlain Jointed Rigid Pavements for Highways

IRC: 15 - 2002, Code of practice for

Construction of Cement Concrete Roads

IRC: 44 - 2008, Guidelines for cement

concrete mix design for pavements

IRC:SP 62 2004, Guidelines for design of CCroads for Rural Roads


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Types of Pavements


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HIGHWAY CONSTRUCTIONS

Pavement Design

Pavement means surfacing layer only.

In terms of highway design, it means

the total thickness of road includingsurfacing , base & subbase, if any.

Thus pavement includes all the

structural layers of road structure lying onsubgrade of the road


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Parameters for Design of Pavements

Design of pavements mainly consists of twoaspects

1. Design mix of materials

2. pavement thickness


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Factors for Design of Pavements

Following factors are responsible for pavement design

1. Climate : rainfall, Temp, Frost action

2. Environment : Ht of embankment, foundation cutting

3. Geometry:

4. Pavement materials: they have to resist climaticconditions ,durability, maintenance.

5. Subgrade Soil : decides thickness of pavement

6. Traffic : Repetitions, Speed, Wheel Loads , contact

pressure, volume of traffic , no of vehicles/day .


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Design Approach for rigid Pavements

Variables for design

1. Wheel Loads

2. Traffic

3. Climate4. Terrain

5. Subgrade conditions

6. Properties of Cement Concrete


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Properties Flexible Rigid

Design

Principle

Empirical method

Based on load distribution

characteristics of the

components

Designed and analyzed by using the elastic

theory

Material Granular material Made of Cement Concrete either plan,

reinforced or prestressed concreteFlexural

Strength

Low or negligible flexible

strength

Associated with rigidity or flexural strength

or slab action so the load is distributed over

a wide area of subgrade soil.

Normal

Loading

Elastic deformation Acts as beam or cantilever

Excessive

Loading

Local depression Causes Cracks

Stress Transmits vertical andcompressive stresses to the

lower layers

Tensile Stress and Temperature Increases

Design

Practice

Constructed in number of

layers.

Laid in slabs with steel reinforcement.

Temperature No stress is produced Stress is producedForce of

Friction

Less. Deformation in the

sub grade is not transferred

to the upper layers.

Friction force is High

Opening to

Traffic

Road can be used for traffic

within 24 hours

Road cannot be used until 14 days of curing

Surfacing Rolling of the surfacing is

needed

Rolling of the surfacing in not needed.


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Components of CC pavement


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Types of Rigid Pavements

1. Jointed Plain Concrete Pavement (JPCP)

No temperature steel

2. Jointed Reinforced Concrete Pavement (JRCP)

Temperature steel placed at mid height and discontinued at

the joints

3. Continuously Reinforced Concrete Pavement (CRCP)

Not popular in Indiavery costly

4. Prestressed Concrete Pavement (PCP)

Not popular


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Cement Concrete roads provides a highly rigid

surface and hence for the success of such roads,

following two conditions should be satisfied

1. They should rest on non- rigid surface having

uniform bearing capacity.

2. The total thickness or depth of the concrete

pavement & the non rigid base should be

sufficient to distribute the wheel load on asufficient area of subbase so that the pressure on

unit area remains with the permissible SBC of the

soil.


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Concrete slab has high modulus of elasticity,

high rigidity & flexural strength, so wheel loads

are distributed over large areas of Subgrade .

This leads to small deflections and also leads

compressive stresses imposed on the Subgrade. This leads to fatigue damage in concrete slab in

form of development of micro cracks, due to

repeated application of traffic loads. This is arrested by limiting flexural stresses and

increasing the Concrete mix grade.


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Design Steps ( parameters )

1. Traffic parameters : Design Wheel load, Traffic intensity

2. Environmental parameters : temp differential ( CRRI

table)

3. Foundation strength k ( modulus of subgrade reaction )

4. Foundation surface characteristics ( As per IRC )5. Concrete characteristics ( IRC :58-1988 )

6. Modulus of elasticity

7. Coefficient of thermal expansion.

8. Design slab thickness


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Purpose of joints in Concrete Roads

1. To absorb expansion & contraction due to variation intemperature. ( horizontal movements of slabs)

2. To avoid warping of slab edges

3. To grant facility in construction .


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TYPES OF JOINTS

Concrete pavements are provided with Jointsin Transverse & Longitudinal directions which

are classified as

a) CONTRACTION JOINTS b) EXPANSION JOINTS

d) CONSTRUCTION JOINTS


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CONTRACTION JOINTS

These are purposely made weakened planeswhich relieve the tensile stresses in the concrete

Caused due to changes in the moisture content(Drying shrinkage) and/or temperature and

Prevent the formation of irregular cracks due torestraint in free contraction of concrete .

They are also provided to

1) )Relieve stresses due to warping

2) To permit the contraction of the slab


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Details of the contraction joints are given in IRC:SP 62

They are formed initially by sawing a groove of 3-5

mm with up to about one-fourth to one-third the slabDetails of the contraction joints are given in IRC:SP 62.They are formed initially by sawing a groove of 3-5mm with up to about one-fourth to one-third the slabthicknesses. This facilitates the formation of a natural

crack at this location extending to the full depth. In order to seal the joint, the top 10-20 mm of this

groove is widened to 610 mm.

Spacing of contraction joints may be kept at 2.50m to

3.75m. Length of panel shall not be more than width of

panel.


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LONGITUDINAL JOINTS

Lanes are jointed together by joint known as Longitudinal joint

Longitudinal joints are provided in multilane pavements and also when the

pavement is more than 4.5 m wide.

They are provided normally at 3.5m c/c to

1) Relieve stresses due to warping.

2) To allow differential shrinkage & swelling due to changes of sub grade

moisture

3) To prevent longitudinal cracking

Procedure of construction

Initially joint is cut to a depth 1/3rd slab Initially joint is cut to a depth 1/3rd

slab thick 5mm. Tie bars are provided at the joints not for load

transference but for keeping the adjoining slabs together. The details of

such joints are given in IRC:SP 62.

The top 15-20 mm of the joint is sawn to a width of 6-8 mm for sealing


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Expansion joints There are full-depth joints provided transversely into which pavement can

expand, thus relieving compressive stresses due to expansion of concrete

slabs, and preventing any tendency towards distortion, buckling, blow-upand spalling.

The current practice is to provide these joints only when concrete slab

abuts with bridge or culvert.

They allow expansion of slabs due to temperature

They permit contraction of slabs Normal Details of these joints are given in

IRC:SP62.

They are about 20 mm in width

A joint filler board of compressible material conforming to IRC:SP:62 is used

to fill the gap between the adjacent slabs at the

joint.

The height of the filler board is such that its top is 23-25mm below the

surface of the pavement.

The joint groove is filled by a sealant .


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Construction joints

The need for such joint arises when construction work is

required to be stopped at a place other than the location ofcontraction or an expansion joint, due to some breakdown of

the machinery or any other reason.

Such joints are of butt type and extend to the full depth of

the pavement.

The sealing of such joints shall be done in the same manner as

for contraction joints, by cutting a groove 10-12 mm wide and

20-25 mm deep.

Generally, such joints are avoided in highways. The work is

normally terminated at a contraction or expansion joint


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JOINT FILLER

Joint spaces are first filled with compressible

filler materials and top of the joints are sealedusing sealer

Joint filler should possess following properties

o Compressibility

o Elasticity i.e they should be capable of regaining

their shape when compression is released

o Durability


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Load Transfer at Transverse Joints

IRC:58-2001 had adopted equations developed by

Friberg for analyzing long beam on elastic foundation(bar embedded in concrete) , for computation ofmaximum bending stress in the dowel bar & maxbearing stress in concrete .

High bearing stress on the concrete surrounding thedowel bar can fracture the same, leading to thelooseness of the dowel bar and the deterioration of thetransfer system leading to faulting of the slab.

The dowel bars are installed at a suitable spacing acrossthe joints and the system is assumed to transfer 40% ofthe wheel load.


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TYPES OF SEALANTS

Hot poured rubberized Asphalts

(Thermoplastic type)

Cold applied poly sulphide sealants

Cold silicone Sealants


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Cleaning of Longitudinal Joint


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Fixing of Back up Rod after Initial Cut


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Widened Groove after 14 days


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Finished PQC surface with Sealed Joints


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Desirable Properties of Soil as Subgrade Material

Stability Incompressibility

Permanency of strength

Minimum changes in volume and stabilityunder adverse condition of weather and

ground water

Good drainage

Ease of compaction


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Fly ash can be as a partial replacement of

cement (OPC) up to an extent of 35%.

Fly ash for blending shall satisfy the following

Properties conforming to IS:3812-2004


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Advantages in adding Fly Ash

a)Increases CSH ( Calcium Silicate Hydrate) volumeb) Denser CSH formed by secondary reaction

c) Better Pore structure and composition

d) Low heat of hydratione) Resistance to adverse exposure conditions

Reaction when Fly Ash is added:

CS + H CSH + CaOHCaOH + Fly AshCSH (cementing gel)


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Design Approach for Flexible Pavements

Traffic is considered in terms of the cumulative

number of standard axles (8160 kg) to be

carried by the pavement during the design life

For estimating the design traffic, the following

Information is needed:

1. Initial traffic after construction (CVPD)

2. Traffic growth rate during the design life

3. By studying the past trends of traffic growth4. As per the econometric procedure outlined in

IRC:108


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Bituminous paving mixes.

Following factors are involved in design ofbituminous paving mixes

1. Durability

2. fatigue resistance3. flexibility

4. fracture or tensile strength

5. permeability6. Skid resistance

7. Thermal characteristics


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Mix Design Methods

1. Marshall method of Mix Design

2. Hveem method of Mix design


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Marshall method of Mix Design

Stability Flow Test

Max load resistance that a Std specimen will

develop at 60 Deg C

Flow is measured as a deformation or total amountin units of 0.25 mm between no of load & maximum

during the stability test expressed as 0.10 mm



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Marshall method of Mix Design criteria

Test Property Category of traffic

Heavy Medium Light

Stability kg Min 340 230 230

Flow value

(0.25 mm)

8 to 16 8 to 16 8 to 20

% Voids

a) For surfacing 3 to 5 3 to 5 3 to 5

b) For base course 3 to 5 3 to 8 3 to 8

i h f l ibl


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Hveem method of Mix design

This method of mix design starts with

obtaining an estimate of optimum bitumen

content by use of Centrifuge Kerosene

equivalent ( C.K.E)

The % of kerosene retained in the aggregate

after being soaked and centrifuged as a

specified is called C.K.E value & charts areavailable to find out the optimum bitumen

content from C.K.E value


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Methods of Design

Group Index Method ( G I )

California Bearing ratio ( C B R ) Method


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Group Index Method

Volume of traffic is divided as below

Very light Less than 50 vehicles per day

Light 50-250 vehicles per day

Medium 250-500 vehicles per day

Heavy 500-750 vehicles per day

Very heavy 750-1000 vehicles per day


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Group Index Method

Depending upon G I grading of soil , daily

volume of the traffic, thickness of surface,

base, & subbase are designed as per the chart

below


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California Bearing Ratio Method

GI method does not take in account

characteristics of the pavement material , So

I.R.C has recommended CBR method for

design of flexible pavements

h f l bl


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Design Approach for Flexible PavementsCalifornia Bearing Ratio Method

CBR test : It is a property of a grade soil which is measured by an test designed byCalifornia State highways USA. It has been standardized by IS also.

It is made on the sample of subgrade soil in a standard loading device whichmeasures the load required to cause 2.5 mm penetration of the plunger havingcross section area 1690 Sq.mm

The plunger is made to penetrate the sample, at a rate of 1.25mm/min unit a

penetration of 2.5 mm is obtained. This pressure at 2.5 mm penetration is worked out and it is expressed as a % of

unit standard pressure. This % is known as CBR

The test is repeated for 5 mm penetration & the CBR is worked out.

Generally 2.5 mm value is higher

Standard loads

2.5 mm 70 kg/cm25 mm 105 kg/cm2


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CBR Test

L d P i C ( CBR T )


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Load Penetration Curve ( CBR Test )

Relation Between CBR and E


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Relation Between CBR and E

Subgrade

E (MPa) = 10 * CBR if CBR 5%

Granular subbase and base

E2 = E3*0.2*h0.45

E2 = Composite modulus of sub-base and base

(MPa)

E3 = Modulus of subgrade (MPa)

h = Thickness of granular layers (mm)


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Typical pavement section

St i d i f fl ibl t


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Steps in design of flexible pavements

The following steps are used in design of flexiblepavements for stage construction.

i) Provide design thicknesses of subbase and base coursesfor 20 years.

ii) Provide bituminous surfacing course for traffic of msa.iii) Provide a shoulder of thickness equal to that of the sumof the layers in steps (i) and (ii) on both sides.

iv) Provide bituminous surfacing course for traffic of msa

after 10 years.v) Provide shoulder thickness equal to the thickness

calculated in step (iv) at the same time


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Modulus values for Bituminous materials

i l


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Penetration value

Penetration value is a measure of hardness or consistency of

bituminous material.It is the vertical distance traversed or penetrated by the

point of a standard needle in to the bituminous material

under specific conditions of load, time and temperature.

This distance is measured in one tenths of a millimeter.

AIM:

(i) To determine the consistency of bituminous material

(ii) To assess the suitability of bitumen for use under differentclimatic conditions and various types of construction.

This test is used for evaluating consistency of bitumen.


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Penetration value

Penetration test is a commonly adopted test on bitumen to

grade the material in terms of its hardness. A 80/100grade bitumen indicates that its penetration value

lies between 80 & 100.

Grading of bitumen helps to assess its suitability in different

climatic conditions and types of construction. For bituminous macadam and penetration macadam, IRC

suggests bitumen grades 30/40, 60/70, 80/100.

In warmer regions, lower penetration grades are preferred to

avoid softening whereas higher penetration grades like180/200 are used in colder regions to prevent the occurrence

of excessive brittleness. High penetration grade is used in

spray application works.

SPECIFICATION OF PENETRATION GRADE BITUMEN


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SPECIFICATION OF PENETRATION GRADE BITUMEN

Default Values of Poissons Ratio ()


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Default Values of Poisson s Ratio ()

(as suggested in IRC:37-2001)

Subgrade and unbound granular layers

Default value of = 0.4

Bituminous Layers

Default value of at 35/45 degree C = 0.5

Default value of at 20 - 30 degree C = 0.35

: Poisson's ratio

T ffi


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Traffic

1. Design life in number of years

NH & SH15 years

Expressways & Urban Roads20 years

Other roads10 to 15 years

2.Vehicle damage factor (VDF)

Need to be worked out from axle load survey

3.Distribution of commercial traffic over the

carriageway. (D & L Factors)

Computation of design traffic


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C t ti f d i t ffi


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D = Lane distribution factor F = Vehicle damage factor

n= Design life in years

R= Annual growth rate of commercial vehicles


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Traffic in the year of completion

A= P(1+r)x

P = Number of commercial vehicles as per

day last countx = Number of years between the last count

and the year of the completion of

construction

Subgrade


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Subgrade

The subgrade should be compacted to 97% of

the dry density achieved with heavy compaction

(modified proctor density) a per IS:2720 (Part 8).

For Expressways, National Highways and State

Highways, the material used for subgrade construction

should have the dry density of not less than 1.75 gm/cc.


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P t C iti (S b b )


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Pavement Composition (Sub-base course)

Granular Sub-base (GSB) materialsconforming to clause 401 of MORT&Hspecifications for road and bridge works isrecommended

The sub-base material should have minimumCBR of 20% for cumulative traffic up to 2 msaand 30% for traffic exceeding 2 msa.

The thickness of sub-base should not be lessthan 150 mm for design traffic less than 10msa and 200 mm for design traffic of 10 msaand above.

Pavement Composition (Sub base course)


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Pavement Composition (Sub-base course)

Preferably the subgrade soil should have a CBR of

2%

If the CBR


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p

(Base course)

The recommended minimum thickness ofgranular base is 225 mm for traffic up to 2 msa

and 250 mm for traffic exceeding 2 msa.

For heavily trafficked roads, use of WMM base

laid by paver finisher or motor grader is recommended.

Where WBM construction should be adopted in

the base course for roads carrying traffic more than 10

msa, the thickness of WBM shall be increased from 250

mm to 300 mm.

Bituminous Surfacing


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Bituminous Surfacing

Shall consists of either a wearing course or a

binder course with a wearing course depending

upon the traffic to be carried.

The selection criteria for the grade of bitumento be used for bituminous courses are given inthe table shown

Where the wearing course adopted is premix

carpet of thickness up to 25 mm, the thicknessof surfacing should not be counted towards the

total thickness of the pavement

Criteria for selection of Grade of Bitumen for Bituminous courses


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Criteria for selection of Grade of Bitumen for Bituminous courses

P t Thi k D i Ch t f T ffi 1 10


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Pavement Thickness Design Chart for Traffic 1-10 msa

Pavement Composition


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Pavement Composition

Pavement Thickness Design Chart for Traffic


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10-150 msa


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Life Cycle Cost Analysis of rigid & Flexible


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Life Cycle Cost Analysis of rigid & Flexible

Pavements

According to a rough estimate ,the physical &financial needs of highway sector for the next

20 years indicates an average annual outlay of

Rs 250000 Crores in the next 10 years & Rs

37500 Crores in the next subsequent period.

In addition to this, Rs 10000 Crores per year

would be required for maintenance with a

steady increase of 5 to 6 %

Comparative Study of Rigid & flexible pavements


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Co pa at e Study of g d & f e b e pa e e ts

Flexible pavements are widely used despite

some doubts regarding their economics underdifferent conditions

Two most important parameters that govern

the pavement design are soil sub-grade andtraffic loading

The Indian guidelines for the design of flexible

pavements use soil sub-grade strength in termsof California Bearing Ratio (CBR) and traffic

loading in terms of million standard axles (msa).


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pavement design and construction

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