Rigid & Flexible Pavements

1. 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 cement
concrete mix design for pavements
IRC:SP 62 – 2004, Guidelines for design of CC
roads for Rural Roads

2. Types of Pavements

3. HIGHWAY CONSTRUCTIONS
Pavement Design
• Pavement means surfacing layer only.
• In terms of highway design, it means
the total thickness of road including
surfacing , base & subbase, if any.
• Thus pavement includes all the
structural layers of road structure lying on
subgrade of the road

4. Parameters for Design of Pavements
Design of pavements mainly consists of two
aspects
1. Design mix of materials
2. pavement thickness

5. 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 climatic
conditions ,durability, maintenance.
5. Subgrade Soil : decides thickness of pavement
6. Traffic : Repetitions, Speed, Wheel Loads , contact
pressure, volume of traffic , no of vehicles/day .

6. 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

7. Flexible Rigid

9. 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.

10. Components of CC pavement

11. 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 India – very costly
4. Prestressed Concrete Pavement (PCP)
• – Not popular

12. Design Approach for rigid Pavements
• 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 a
sufficient area of subbase so that the pressure on
unit area remains with the permissible SBC of the
soil.

13. Design Approach for rigid Pavements
• 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.

14. 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

15. 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 .

16. 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

17. CONTRACTION JOINTS
• These are purposely made weakened planes
which 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 to
restraint in free contraction of concrete .
• They are also provided to
1) )Relieve stresses due to warping
2) To permit the contraction of the slab

18. 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 slab
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 slab
thicknesses. 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.

19. 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

20. 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-up
and 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 .

23. Construction joints
The need for such joint arises when construction work is
required to be stopped at a place other than the location of
contraction 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

26. 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

27. 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 of
maximum bending stress in the dowel bar & max
bearing stress in concrete .
• High bearing stress on the concrete surrounding the
dowel bar can fracture the same, leading to the
looseness of the dowel bar and the deterioration of the
transfer system leading to faulting of the slab.
• The dowel bars are installed at a suitable spacing across
the joints and the system is assumed to transfer 40% of
the wheel load.

28. TYPES OF SEALANTS
• Hot poured rubberized Asphalts
(Thermoplastic type)
• Cold applied poly sulphide sealants
• Cold silicone Sealants

29. Cleaning of Longitudinal Joint

30. Fixing of Back up Rod after Initial Cut

31. Widened Groove after 14 days

32. Finished PQC surface with Sealed Joints

33. 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

34. Cements that can be used as per IRC: 44-2008
Any of the following types of cements capable of
achieving the design strength and durability may
be used with the prior approval of the Engineer.
1. Ordinary Portland Cement, 33 grade, IS: 269
2. Ordinary Portland Cement, 43 grade, IS: 8112
3. Ordinary Portland Cement, 53 grade, IS: 12269
4. Portland Pozzalona Cement (fly ash based, IS:
1489, part1
5. Portland Slag Cement, IS: 455

38. 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

40. 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 AshCSH (cementing gel)

41. 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

42. Design Approach for Flexible Pavements
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

43. Design Approach for Flexible Pavements
Mix Design Methods
1. Marshall method of Mix Design
2. Hveem method of Mix design

44. Design Approach for Flexible Pavements
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 amount
in units of 0.25 mm between no of load & maximum
during the stability test expressed as 0.10 mm

45. Design Approach for Flexible Pavements
• 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

46. Design Approach for Flexible Pavements
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 are
available to find out the optimum bitumen
content from C.K.E value

47. Design Approach for Flexible Pavements
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 & 67
respectively
• Cohesive meter value should not be more than 50
• Air voids % should have minimum value of 4%

48. Design Approach for Flexible Pavements
Methods of Design
Group Index Method ( G I )
California Bearing ratio ( C B R ) Method

49. Design Approach for Flexible Pavements
Group Index Method
• GI is a arbitrary index given to the type of
soil and is based on % of fines ,liquid limit, and
plasticity index of the soils
• GI values range from 0 to 20
• Greater GI value, poorer the soil

50. Design Approach for Flexible Pavements
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

51. Design Approach for Flexible Pavements
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

52. Design Approach for Flexible Pavements

53. Design Approach for Flexible Pavements
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

54. 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 by
California State highways USA. It has been standardized by IS also.
• It is made on the sample of subgrade soil in a standard loading device which
measures the load required to cause 2.5 mm penetration of the plunger having
cross 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/cm2
5 mm 105 kg/cm2

55. CBR Test

56. Load Penetration Curve ( CBR Test )

57. 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)

58. Typical pavement section

59. Steps in design of flexible pavements
• The following steps are used in design of flexible
pavements for stage construction.
i) Provide design thicknesses of subbase and base courses
for 20 years.
ii) Provide bituminous surfacing course for traffic of msa.
iii) Provide a shoulder of thickness equal to that of the sum
of 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

60. Modulus values for Bituminous materials

61. 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 different
climatic conditions and various types of construction.
This test is used for evaluating consistency of bitumen.

62. Penetration value
• Penetration test is a commonly adopted test on bitumen to
grade the material in terms of its hardness.
• A 80/100 grade 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 like
180/200 are used in colder regions to prevent the occurrence
of excessive brittleness. High penetration grade is used in
spray application works.

63. SPECIFICATION OF PENETRATION GRADE BITUMEN

64. 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

65. 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)

66. Computation of design traffic

67. Computation of design traffic
• D = Lane distribution factor
• F = Vehicle damage factor
• n= Design life in years
• R= Annual growth rate of commercial vehicles

68. 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

69. 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.

70. 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 on
remoulded 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

71. Pavement Composition (Sub-base course)
• Granular Sub-base (GSB) materials
conforming to clause 401 of MORT&H
specifications for road and bridge works is
recommended
• The sub-base material should have minimum
CBR of 20% for cumulative traffic up to 2 msa
and 30% for traffic exceeding 2 msa.
• The thickness of sub-base should not be less
than 150 mm for design traffic less than 10
msa and 200 mm for design traffic of 10 msa
and above.

72. Pavement Composition (Sub-base course)
• Preferably the subgrade soil should have a CBR of
2%
• If the CBR<2%, the design should be based on
a CBR of 2% and a capping layer of 150 mm
thickness of material with a minimum CBR of 10%
shall be provided in addition to the subbase
• Where stage construction is adopted, the thickness
of sub-base shall be provided for ultimate pavement
section for the full design life

73. 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 10
msa, the thickness of WBM shall be increased from 250
mm to 300 mm.

74. 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 bitumen
to be used for bituminous courses are given in
the 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

75. Criteria for selection of Grade of Bitumen for Bituminous courses

76. Pavement Thickness Design Chart for Traffic 1-10 msa

77. Pavement Composition

78. Pavement Thickness Design Chart for Traffic
10-150 msa

80. 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 %

81. 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).

82. Comparative Study of Rigid & flexible pavements