pavements ppt

HIGHWAY CONSTRUCTION

IRC: 58 - 2002, Guidelines for the design of

Plain Jointed Rigid Pavements for Highways

IRC: 15 - 2002, Code of practice for

Construction of Cement Concrete Roads

IRC: 44 - 2008, Guidelines for cementconcrete mix design for pavements

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

Types of Pavements

HIGHWAY CONSTRUCTIONS

Pavement Design

• Pavement means surfacing layer only.

• In terms of highway design, it meansthe total thickness of road includingsurfacing , base & subbase, if any.

• Thus pavement includes all thestructural layers of road structure lying onsubgrade of the road

Parameters for Design of Pavements

Design of pavements mainly consists of twoaspects

1. Design mix of materials

2. pavement thickness

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

Design Approach for rigid Pavements

• Variables for design

1. Wheel Loads

2. Traffic

3. Climate

4. Terrain

5. Subgrade conditions

6. Properties of Cement Concrete

Flexible Rigid

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 concrete

Flexural

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 and

compressive 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 produced

Force 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.

Components of CC pavement

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 atthe joints

3. Continuously Reinforced Concrete Pavement (CRCP)

• – Not popular in India – very costly

4. Prestressed Concrete Pavement (PCP)

• – Not popular


• Cement Concrete roads provides a highly rigidsurface and hence for the success of such roads,following two conditions should be satisfied

1. They should rest on non- rigid surface havinguniform bearing capacity.

2. The total thickness or depth of the concretepavement & the non rigid base should besufficient to distribute the wheel load on asufficient area of subbase so that the pressure onunit area remains with the permissible SBC of thesoil.


• Concrete slab has high modulus of elasticity,high rigidity & flexural strength, so wheel loadsare distributed over large areas of Subgrade .This leads to small deflections and also leadscompressive stresses imposed on the Subgrade.

• This leads to fatigue damage in concrete slab inform of development of micro cracks, due torepeated application of traffic loads.

• This is arrested by limiting flexural stresses andincreasing the Concrete mix grade.

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

Purpose of joints in Concrete Roads

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

2. To avoid warping of slab edges

3. To grant facility in construction .

TYPES OF JOINTS

• Concrete pavements are provided with Joints in Transverse & Longitudinal directions which are classified as

• a) CONTRACTION JOINTS

• b) EXPANSION JOINTS

• d) CONSTRUCTION JOINTS

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 to1) )Relieve stresses due to warping2) To permit the contraction of the slab

Details 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 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 naturalcrack at this location extending to the full depth.

• In order to seal the joint, the top 10-20 mm of thisgroove is widened to 610 mm.

• Spacing of contraction joints may be kept at 2.50m to3.75m.

• Length of panel shall not be more than width ofpanel.

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

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

expand, thus relieving compressive stresses due to expansion of concreteslabs, and preventing any tendency towards distortion, buckling, blow-upand spalling.

• The current practice is to provide these joints only when concrete slababuts with bridge or culvert.

• They allow expansion of slabs due to temperature

• They permit contraction of slabs Normal Details of these joints are given inIRC:SP62.

• They are about 20 mm in width

• A joint filler board of compressible material conforming to IRC:SP:62 is usedto 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 thesurface of the pavement.

• The joint groove is filled by a sealant .

Construction joints

The need for such joint arises when construction work isrequired to be stopped at a place other than the location ofcontraction or an expansion joint, due to some breakdown ofthe 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 asfor contraction joints, by cutting a groove 10-12 mm wide and

20-25 mm deep.

Generally, such joints are avoided in highways. The work isnormally terminated at a contraction or expansion joint

JOINT FILLER

• Joint spaces are first filled with compressible filler materials and top of the joints are sealed using 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

Load Transfer at Transverse Joints

• IRC:58-2001 had adopted equations developed byFriberg 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.

TYPES OF SEALANTS

• Hot poured rubberized Asphalts(Thermoplastic type)

• Cold applied poly sulphide sealants

• Cold silicone Sealants

Cleaning of Longitudinal Joint

Fixing of Back up Rod after Initial Cut

Widened Groove after 14 days

Finished PQC surface with Sealed Joints

Desirable Properties of Soil as Subgrade Material

• Stability

• Incompressibility

• Permanency of strength

• Minimum changes in volume and stability under adverse condition of weather and ground water

• Good drainage

• Ease of compaction

Cements that can be used as per IRC: 44-2008

Any of the following types of cements capable ofachieving the design strength and durability maybe used with the prior approval of the Engineer.

1. Ordinary Portland Cement, 33 grade, IS: 269



4. Portland Pozzalona Cement (fly ash based, IS:1489, part1

5. Portland Slag Cement, IS: 455

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

Advantages in adding Fly Ash

a) Increases CSH ( Calcium Silicate Hydrate) volume

b) Denser CSH formed by secondary reaction

c) Better Pore structure and composition

d) Low heat of hydration

e) Resistance to adverse exposure conditions

Reaction when Fly Ash is added:

CS + H CSH + CaOH

CaOH + Fly AshCSH (cementing gel)

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 growth

4. As per the econometric procedure outlined in

IRC:108


Bituminous paving mixes.

• Following factors are involved in design of bituminous paving mixes

1. Durability

2. fatigue resistance

3. flexibility

4. fracture or tensile strength

5. permeability

6. Skid resistance

7. Thermal characteristics


Mix Design Methods

1. Marshall method of Mix Design

2. Hveem method of Mix design


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 & maximumduring the stability test expressed as 0.10 mm


• 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


Hveem method of Mix design

This method of mix design starts withobtaining an estimate of optimum bitumencontent by use of Centrifuge Keroseneequivalent ( C.K.E)

The % of kerosene retained in the aggregateafter being soaked and centrifuged as aspecified is called C.K.E value & charts areavailable to find out the optimum bitumencontent from C.K.E value


Hveem method of Mix design • It consists of 3 tests on bituminous samples of 100 mm diameter &

63.50 mm ht. Each specimen is tested for subsequent tests

• Following tests are conducted

1. Swell Test 100 mm dia

2. Stabilometer Test

3. Cohesive meter Test

• Swell should not be < 0.76 mm 63.50 mm

• Stabilometer values for light, medium, heavy should be 30,35 & 67respectively

• Cohesive meter value should not be more than 50

• Air voids % should have minimum value of 4%


Methods of Design

Group Index Method ( G I )

California Bearing ratio ( C B R ) Method


Group Index Method

• GI is a arbitrary index given to the type ofsoil and is based on % of fines ,liquid limit, andplasticity index of the soils

• GI values range from 0 to 20

• Greater GI value, poorer the soil


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


Group Index Method

• Depending upon G I grading of soil , dailyvolume of the traffic, thickness of surface,base, & subbase are designed as per the chartbelow


California Bearing Ratio Method

GI method does not take in accountcharacteristics of the pavement material , So

I.R.C has recommended CBR method fordesign of flexible pavements

Design Approach for Flexible Pavements California 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 apenetration of 2.5 mm is obtained.

• This pressure at 2.5 mm penetration is worked out and it is expressed as a % ofunit 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/cm2

5 mm 105 kg/cm2

CBR Test

Load Penetration Curve ( CBR Test )

Relation Between CBR and E

• Subgrade

• E (MPa) = 10 * CBR if CBR<5% and

• = 176 *(CBR)0.64 for 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)

Typical pavement section

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 msaafter 10 years.

v) Provide shoulder thickness equal to the thicknesscalculated in step (iv) at the same time

Modulus values for Bituminous materials

Penetration valuePenetration value is a measure of hardness or consistency ofbituminous material.

It is the vertical distance traversed or penetrated by thepoint of a standard needle in to the bituminous materialunder 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.

Penetration value

• Penetration test is a commonly adopted test on bitumen tograde the material in terms of its hardness.

• A 80/100 grade bitumen indicates that its penetration valuelies between 80 & 100.

• Grading of bitumen helps to assess its suitability in differentclimatic conditions and types of construction.

• For bituminous macadam and penetration macadam, IRCsuggests bitumen grades 30/40, 60/70, 80/100.

• In warmer regions, lower penetration grades are preferred toavoid softening whereas higher penetration grades like180/200 are used in colder regions to prevent the occurrenceof excessive brittleness. High penetration grade is used inspray application works.

SPECIFICATION OF PENETRATION GRADE BITUMEN

Default Values of Poisson’s Ratio (μ)

(as suggested in IRC:37-2001)

Subgrade and unbound granular layers

Default value of μ = 0.4

Bituminous Layers

Default value of μ at 35/45 degree C = 0.5

Default value of μ at 20 - 30 degree C = 0.35

μ: Poisson's ratio

Traffic

1. Design life in number of years

• NH & SH – 15 years

• Expressways & Urban Roads – 20 years

• Other roads – 10 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

Computation of design traffic

• D = Lane distribution factor

• F = Vehicle damage factor

• n= Design life in years

• R= Annual growth rate of commercial vehicles

Traffic in the year of completion

A= P(1+r)x

P = Number of commercial vehicles as per day last count

x = Number of years between the last count and the year of the completion of construction

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

Subgrade

• For determining the CBR value, the standard

test procedure described in IS:2720 (Part 16)

should be strictly adhered to.

• The test must always be performed onremoulded samples of soils in the laboratory

• It is recommended that the samples be soaked

in water for four days prior to testing

• In situ CBR test is not recommended

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)

• Preferably the subgrade soil should have a CBR of2%

• If the CBR<2%, the design should be based on

a CBR of 2% and a capping layer of 150 mmthickness of material with a minimum CBR of 10%shall be provided in addition to the subbase

• Where stage construction is adopted, the thicknessof sub-base shall be provided for ultimate pavementsection for the full design life

Pavement Composition(Base course)

• The recommended minimum thickness of

granular 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 10msa, the thickness of WBM shall be increased from 250mm to 300 mm.

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 thickness

of surfacing should not be counted towards the

total thickness of the pavement

Criteria for selection of Grade of Bitumen for Bituminous courses

Pavement Thickness Design Chart for Traffic 1-10 msa

Pavement Composition

Pavement Thickness Design Chart for Traffic10-150 msa

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

• Flexible pavements are widely used despite some doubts regarding their economics under different conditions

• Two most important parameters that govern the pavement design are soil sub-grade and traffic loading

• The Indian guidelines for the design of flexible pavements use soil sub-grade strength in terms of California Bearing Ratio (CBR) and traffic loading in terms of million standard axles (msa).

Comparative Study of Rigid & flexible pavements

pavements ppt

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