theory and analysis of rigid pavement

1. PRESENTATION
ON
RIGID PAVEMENT
Dept. of Civil Engineering
NATIONAL INSTITUTE OF TECHNOLOGY , HAMIRPUR
SUBMITTED TO :- PRESENTED BY:-
ASST. PROF. SHASHI KANT
SHARMA RAHUL JAIN (16M141)

2. Transportation EngineeringTransportation Engineering
THE RIGID PAVEMENTTHE RIGID PAVEMENT
2

3. INTRODUCTIONINTRODUCTION
 Development of a country depends on the connectivity
of various places with adequate road network.
 Roads constitute the most important mode of
communication in areas where railways have not
developed much.
3

4.  India has one of the largest road networks in the world
(over 3 million km at present).For the purpose of
management and administration, roads in India are
divided into the following five categories:
• National Highways (NH)
• State Highways (SH)
• Major District Roads (MDR)
• Other District Roads (ODR)
• Village Roads (VR)
4

5. WHAT IS ROAD ?WHAT IS ROAD ?
 Road is an open, generally public way for the passage
of vehicles, people, and animals.
 Finish with a hard smooth surface (pavement) helped
make them durable and able to withstand traffic and
the environment.
 Roads have a life expectancy of between 20 - 30 years.
5

6. What is a Pavement?What is a Pavement?
• A multi layer system that distributes the vehicular
loads over a larger area
6

7. What is a Pavement?What is a Pavement?
OR
• Highway pavement is a structure consisting of
superimposed layers of selected and processed
materials whose primary function is to distribute
the applied vehicle load to the sub grade.
OR
• It can also be defined as “structure which
separates the tyres of vehicles from the under
lying foundation.”
• Pavement is the upper part of roadway, airport or
parking area structure
• It includes all layers resting on the original ground
7

8. Functions of the PavementFunctions of the Pavement
• Reduce and distribute the traffic loading so as not to
damage the subgrade.
• Provide vehicle access between two points under all-
weather conditions.
• Provide safe, smooth and comfortable ride to road
users without undue delays and excessive wear & tear.
• Meet environmental and aesthetics requirement.
• Limited noise and air pollution.
• Reasonable economy.
8

9. RequirementRequirementss of pavement structureof pavement structure
• Sufficient thickness to spread loading to a pressure
intensity tolerable by subgade.
• Sufficiently strong to carry imposed stress due to
traffic load.
• Sufficient thickness to prevent the effect of frost
susceptible subgrade.
• Pavement material should be impervious to
penetration of surface water which could weaken
subgrade and subsequently pavement.
• Pavement surface should be skid resistant.
9

10. History of Road DevelopmentHistory of Road Development
10

11. Classification of PavementsClassification of Pavements
11

12. Types of PavementTypes of Pavement
12
Flexible Pavements
PAVEMENTS
Rigid Pavements

13. ComparisonComparison
13
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.

14. 14
Pavements ComparisonPavements Comparison
Flexible pavements:
• Deep foundations / multi layer construction
• Energy consumption due to transportation of materials
• Increasing cost of asphalt due to high oil prices
Rigid pavements
• Single layer
• Generally last longer
• May require asphalt topping due to noise / comfort
issues

15. 15
Pavements ComparisonPavements Comparison
• Heavy vehicles consume less fuel on rigid pavements
• Rigid pavements more economic when considering
environmental / life-cycle costing

16. Types Of PavementsTypes Of Pavements
16

17. Flexible Rigid

18. 18

19. RIGID PAVEMENTRIGID PAVEMENT
19
Rigid pavements are those, which contain sufficient
beam strength to be able to bridge over the localized
sub-grade failures and areas of in adequate support.
OR
Load is transmitted through beam action of slab in rigid
pavements.
OR
Rigid pavements are those, which reduces the stress
concentration and distributes the reduced stresses
uniformly to the area under the slab.

20. RIGID PAVEMENTRIGID PAVEMENT
20
Deflection is very small hence the name rigid
pavement.
The high flexural strength is predominant and the
subgrade strength does not have much importance as
in case of flexible pavement.
 usually finite slab with joints.
 continously slab can be provided without jointed.

21. RIGID PAVEMENTRIGID PAVEMENT
21
Rigid pavements, though costly in initial investment, are
cheap in long run because of low maintenance costs, The cost
of construction of single lane rigid pavement varies from 35
to 50 lakhs per km in plain area,
•Rigid pavement have deformation in the sub grade is not
transferred to subsequent layers.
•Design is based on flexural strength or slab action,Have high
flexural strength.
•No such phenomenon of grain to grain load transfer exists
•Have low repairing cost but completion cost is high
•Life span is more as compare to flexible (Low Maintenance
Cost)

22. Basic Components of Concrete PavementBasic Components of Concrete Pavement
22

23. 23
Rigid PavementsRigid Pavements

24. Types of Concrete PavementsTypes of Concrete Pavements
24

25. Un Reinforced Concrete PavementsUn Reinforced Concrete Pavements
25
•These are plain cement concrete pavements (PCCP)
constructed with closely spaced.
•In almost all jointed pavements , load transfer
mechanism is implemented using dowel bars placed in
transverse joints. Such pavements are called
JDCP/JPCP.
•When The traffic intensity is very low in that case dowel
bars are not provided such pavements are termed as
JUDCP.

26. JPCPJPCP
26

27. Jointed Plain Concrete Pavement (JCPC)Jointed Plain Concrete Pavement (JCPC)

28. Reinforced Concrete PavementReinforced Concrete Pavement
28
•Occurrence of cracks in concrete slabs is inevitable
due to repeated applications of axle loads and
weathering action in different seasons.
• Steel reinforcement in slab is provided to inhibit
widening of cracks and known as RCP.
•In JRCP steel mesh or mat is placed at the middle of
each slab . It is not meant for structural strength but
to provide control the crack width.

29. JRCPJRCP
29

30. Continuous Reinforced Concrete Pavement:Continuous Reinforced Concrete Pavement:
30
•Complete elimination of joints are achieved by
reinforcement.
•Bars are distributed continuously in the longitudinal
direction so that the construction of transverse joints can be
eliminated.
• CRCP preferred in (i) main heavy traffic corridors
(expressways) (ii) Adverse climatic conditions (iii) Weak
sub grades.

31. CRCPCRCP
31

32. Precast Prestressed PavementPrecast Prestressed Pavement
32

33. Factors Governing Design of PavementsFactors Governing Design of Pavements
• Design wheel load
Static load on wheels.
Contact Pressure.
Load Repetition.
• Subgrade soil
Thickness of pavement required.
Stress- strain behaviour under load.
Moisture variation.
• Design Period .
• Design commercial traffic volume.
33

34. • Composition of commercial traffic in terms of single ,
tridem , tandem.
• Axle load spectrum.
• Tyre pressure.
• Lateral placement characteristics.
• Pavement component materials.
• Climatic factors.
• Required Cross sectional elements of the alignment.
34

35. Axle load
• The total weight of the vehicle is carried by its axles.
The load on the axles is transfers to the wheels and this
load is ultimately transferred to the surface of the
pavement in contact with the tyres . therefore more
number of axles more load is to be transferred on wider
area.
Wheel load
• The next important factor is the wheel load which
determines the depth of the pavement required to
ensure that the subgrade soil is not failed. Wheel
configuration affect the stress distribution and
deflection within a pavement. Many commercial
vehicles have dual rear wheels which ensure that the
contact pressure is within the limits.
35

36. Contact Pressure
• For most of the commercial vehicles the commonly
used tyre inflation pressures range about .7 Mpa to1.0
Mpa it is found that stress in concrete pavements
having thickness of 200 mm or higher are not affected
significantly by the variation of tyre pressure . a tyre
pressure of 0.8 Mpa is adopted .The imprint area is
generally taken as circular area for design purpose.
Load Repletion
• This factor govern the that the type of axles repeated
throughout the design life that is how much repletion
of single , tandem and tridem axles are taking place ,
and this factor considered for TDC and BUC.
36

37. Static Load On WheelsStatic Load On Wheels
• This factor is used to design the thickness of slab
because the load of the axle is ultimately transfers to
wheel.
• Axle Load Characteristics
Though the legal limits in India are 10.2 tonnes , 19.0
tonnes, 24.0 tonnes for single , tandem , tridem axle
respectively but a large number of axles operating on
national highways carry much heavier loads than the
legal limits. Data on load spectrum of the commercial
vehicles is required to estimate the repetitions of single
,tandem , tridem axles in each direction expected
during the design period
37

38. • Minimum percentage of vehicle to be weighed should
be 10 percent if Commercial vehicles per day (cvpd)
exceeding 6000 , 15 percent for cpvd for 3000 to 6000
and 20 percent for cpvd for less than 3000 . Axle load
survey may be conducted at least for 48 hrs and data
on axle load spectrum of the commercial vehicles is
required to estimate the repletion of single , tandem ,
tridem axles . If the spacing of consecutive vehicle is
greater than 2.4 meters then the each vehicle may be
considered as single axle.The interval at which axle
load group should be classified :
• Single axle-10 kN
• Tandem axle -20 kN
• Tridem axle -30 kN
38

39. Wheel Base Characteristics
• Information on typical spacing between successive
axles of commercial vehicle is necessary to identify the
proportion of axles that should be considered for
estimating Top- Down fatigue cracking caused by axle
load during night period when the slab has tendency of
curling up due to negative temperature differential. The
axles spacing of more than 4.5 m are not expected to
contribute Top-Down fatigue cracking.
39

40. 2 Axle Truck
3 Axle Truck
Truck ConfigurationTruck Configuration
4 Axle Semi Articulated
5 Axle Truck
LCV

41. Axle ConfigurationsAxle Configurations
Single Axle With
Single Wheel
Single Axle With Dual
Wheel
Tandem Axle
Tridem Axle
An axle is a central shaft for a
rotating wheel or gear

42. Standard AxleStandard Axle
Single axle with dual wheels carrying a load of 10.2
tonnes is defined as standard axle.
10.2 Tonnes
Standard Axle

43. DESIGN LIFEDESIGN LIFE
• To achieve a design of low life cycle cost and in
respect of the high social cost for full depth
reconstruction,
• The design life for rigid pavement is generally
recommended as 30 years.
• Within this life span, it is expected that no extensive
rehabilitation is required under normal circumstances .
• The service life of the pavement structure can be
sustained by minor repairs.
• It is anticipated that the service life can be further
extended upon ‘expiry’ of the original ‘design life’ by
timely maintenance and localized bay replacement.
43

44. Commercial Vehicle ForecastCommercial Vehicle Forecast
The definition of commercial vehicle follows the one
given in the Annual Traffic Census published by
Transport Department, which includes medium /heavy
goods vehicle and bus, other light vehicles, for
examples, motor cycle ,private car and public light bus,
are normally ignored as their induced structural damage
on pavements is minimal. The annual flow of
commercial vehicles at the time of road opening is
obtained by multiplying the daily flow by 365
days/year. The cumulative number of commercial
vehicles using a road during its design life is obtained
by summing up the annual traffic of each year taking
into consideration the predicted growth rate.
44

45. The forecast can be done with reference to on-site traffic
count data, traffic census or other available traffic
studies and planning data .
C=(365*A{(1+r) n -1})/r˄
45

46. Traffic considerationTraffic consideration
Design lane
The lane carrying the maximum number of heavy
commercial vehicle is termed as design lane . each lane of
the two way lane highways are the outer lane of multi
lane highways can be considered as design lane .
• Lateral placement characteristics.
It is recommended that 25 percent of the total two –way
commercial traffic may be considered as design traffic for
two- lane two – way roads for the analysis of BUC. In
case four lanes and other multi lane divided highways 25
percent of the total traffic in the direction of predominant
traffic may be considered for design of pavement for
bottom up cracking. For TDC those vehicles with the
spacing between transverse joint.
46

47. Temperature Consideration
• Temperature differential between the top and the
bottom fibers of concrete pavements causes the
concrete slab to curl giving rise to the stress and this is
a function of solar radiation received by the pavements
surface , wind velocity , latitude etc . As far as possible
actual temperature differential should be considered. In
the absence of data code has given the maximum
temperature differential.
47

48. Concrete strengthConcrete strength
Flexural strength of the concrete is required for the
purpose of design of concrete slab and this flexural
strength is taken for 90 days insist of 28 days because
initial repletion a are very low and it can be obtained
by multiplying factor 1.1
fcr= 1.1 * 0.7√fck
48

49. Modulus of elasticity and poission ratio ofModulus of elasticity and poission ratio of
concreteconcrete
• The modulus of elasticity and poisson ratio are known
to vary with the concrete materials and strength.
• The elastic modulus increase with the increase in
strength and poisson ratio decrease with increase in
modulus of elasticity
• E=30000Mpa
• µ=0.15
• Coefficient of Thermal Expansion
• The coefficient of thermal expansion of concrete is
dependent to a great extent on the types of aggregate
used in concrete. However for design purpose a value
of α=10*10-6˚C is adopted. 49

50. Fatigue behavior of cement concreteFatigue behavior of cement concrete
• Due to repeated application of flexural streesse by the
traffic load , progressive fatigue damage takes place in
the cement concrete slab in the form of gradual
devlopement of micro cracks especially when the ratio
between the flexure stress and flexure strength of
concrete is high this ratio is termed as stress ratio (SR)
and following relation is given.
50

51. Environmental factorsEnvironmental factors
• Environmental factors affect the performance of the
pavement materials and cause various damages.
Temperature:
• In rigid pavements, due to difference in temperatures
of top and bottom of slab, temperature stresses or
frictional stresses are developed. When there is
variation in temperature due to which curling of slab
with different temperature will be different and hence
TDC and BUC factors has to be considered .
51

52. Precipitation :
The precipitation from rain and snow affects the quantity
of surface water infiltrating into the subgrade and the
depth of ground water table. Poor drainage may bring
lack of shear strength, pumping, loss of support, etc.
•Material characteristics
Pavement material consists of different types of sub
grade soil , fine aggregates, granular materials , binders, ,
etc . physical and engineering properties of different
material used for constructing any kind of pavement plays
an important role in thickness design of pavement.
52

53. • COMPONENTS AND ALSOCOMPONENTS AND ALSO
GOVERNING FACTORS OFGOVERNING FACTORS OF
PAVEMENT DESIGNPAVEMENT DESIGN
53

54. SubgradeSubgrade
• In winkler model it is assumed that the foundation is
made up of springs supporting the concrete slabs the
strength of subgrade is expressed in terms of modulus
of subgrade reaction K .
• Which is defined as the pressure per unit deflection of
the foundations as determined by plate load test The
modulus of subgrade reaction (k) is used as a primary
input for rigid pavement design. It estimates the
support of the layers below a rigid pavement surface
course (the PCC slab). The k value can be determined
by field tests or by correlation with other tests. There is
no direct laboratory procedure for determining k value.
54

55. • Westergaard considered the rigid pavement slab as a thin
elastic plate resting on soil subgrade,which is assumed as
a dense liquid. The upward reaction is assumed to be
proportional to the deflection. Base on this assumption,
Westergaard defined a modulus of subgrade reaction in
kg/cm given by where is the displacement level taken as
0.125 cm and is the pressure sustained by the rigid plate
of 75 cm diameter at a deflection of 0.125 cm.
• If the diameter of plate is not 75 cm then even then we
can find the value of k by using the following equations
K750=kΦ(1.21Φ+.078)
55

56. • In case the plate bearing test could not be conducted,
the approximate k- value corresponding to CBR values
can be obtained from its soaked CBR value using
Table 2 (IRC:58-2011 )
56

57. 57

58. Sub Base
The main purpose of the sub base is to provide the
uniform ,stable,and the permanent support to the
concrete slab laid over it .It should have sufficient
strength so that it is not subjected to disintegration and
erosion under heavy traffic and adverse environment
conditions. For these sub base of Dry lean concrete
having 7 day strength of 10 Mpa determined is
recommended. The effective k value of different
combinations of subgrade and sub base can be
estimated from table 3.
58

59. Drainage layer /Filtration layerDrainage layer /Filtration layer
• Entrapped water in the subgrade and granular sub base
may cause erosion of the foundation material since
pore water pressure generated by the tandem and
tridem is substantially high.
• To facilitate quick disposal of water that is likely to
enter subgarde, a drainage layer together with filter/
separation layer may be provided beneath the subbase
throughout the road width. The filtration layer also
prevents fines from pumping up from the subgrade to
the drainage layer.
59

60. Debonding layerDebonding layer
• To reduce the friction between concrete slab and
DLC.
• Generally 125 micron thin sheet .(polythene).
60

61. • RIGID PAVEMENTRIGID PAVEMENT
DESIGNDESIGN
61

62. Modulus of sub-grade reactionModulus of sub-grade reaction
Westergaard considered the rigid pavement slab as a thin
elastic plate resting on soil sub-grade, which is assumed
as a dense liquid. The upward reaction is assumed to be
proportional to the deflection. Base on this assumption,
Westergaard defined a modulus of sub-grade reaction K
in kg/cm3 given by ΔK = p
where Δ is the displacement level taken as 0.125 cm
and p is the pressure sustained by the rigid plate of 75 cm
diameter at a deflection of 0.125 cm.
62

63. Relative stiffness of slab to sub-gradeRelative stiffness of slab to sub-grade
A certain degree of resistance to slab deflection is offered
by the sub-grade. The sub-grade deformation is
same as the slab deflection. Hence the slab deflection is
direct measurement of the magnitude of the sub-grade
pressure. This pressure deformation characteristics of
rigid pavement lead Westergaard to the define the term
radius of relative stiffness l in cm is given by the below
equation
63

64. Equivalent radius of resisting sectionEquivalent radius of resisting section
When the interior point is loaded, only a small area of the
pavement is resisting the bending moment of the
plate. Westergaard's gives a relation for equivalent radius
of the resisting section in cm in the below equation
where a is the radius of the wheel load distribution in cm
and h is the slab thickness in cm.
64

65. Critical load positionsCritical load positions
Since the pavement slab has finite length and width,
either the character or the intensity of maximum stress
induced by the application of a given traffic load is
dependent on the location of the load on the pavement
surface. There are three typical locations namely the
interior, edge and corner, where differing conditions of
slab continuity exist. These locations are termed as
critical load positions.
65

66. where h is the slab thickness in cm, P is the wheel load in
kg, a is the radius of the wheel load distribution in
cm, l the radius of the relative stffiness in cm and b is the
radius of the resisting section in cm
66

67. Wheel load stresses - Westergaard's stressWheel load stresses - Westergaard's stress
equationequation
• The cement concrete slab is assumed to be
homogeneous and to have uniform elastic properties
with verticalsub-grade reaction being proportional to
the deflection.
• Westergaard (1926) developed equations for solution
of load stresses at three critical regions of the slab
– interior, corner and edge
• Interior -Load in the interior and away from all the
edges
• Edge – Load applied on the edge away from the
corners
67

68. 68
Corner – Load located on the bisector of the corner
angle Westergaard developed relationships for the stress at
interior, edge and corner regions, in kg/cm2

69. Temperature stressesTemperature stresses
Temperature stresses are developed in cement concrete
pavement due to variation in slab temperature.
This iscaused by (i) daily variation resulting in a
temperature gradient across the thickness of the slab and
(ii) seasonalvariation resulting in overall change in the
slab temperature.
The former results in warping stresses and the
later in frictional stresses.
69

70. 70

71. Warping stressWarping stress
•Temperature differential between the top and the bottom
surfaces of a cement concrete slab is a common
phenomenon whether its day or night. Expansion and
contraction of the slab as a result of temperature
difference causing geometric deformation – either curling
up or down. Warping or temperature stresses will
produced in the slab when geometric deformations are
completely restrained by its self weight. Two critical
conditions of warping stresses in a cement concrete slab
are presented in figure (next slide). Due to curling of the
slab , tensile and compressive stresses are produced in its
bottom fibers during the day and night respectively .
maximum warping stress is observed at the interior of
the slab than towards its edges since the interior part of
the slab is more restrained against curling than the edges.
71

72. Warping stress in concrete slab when curlingWarping stress in concrete slab when curling
is restrained at different timesis restrained at different times
72

73. • Based on the plate theory, westergaard (1926)
developed formula for calculating the warping stresses
in the concrete slab . In 1938 , Bradbury modifies his
formulae and developed the following equations for
calculating the maximum warping stress at the interior
and edge of the slab having finite dimensions
73

74. Frictional stressesFrictional stresses
Slab movement are restrained by its self weight caused by
the inter surface frictional forces between the slab and the
supporting layer ( sub – base layer ). For example
when the slab contracts its movement are restrained by
frictional forces and tensile stresses are developed
74

75. Critical Combination of StressesCritical Combination of Stresses
The cumulative effect of the different stress give rise to
the following three critical cases.
• Summer, mid-day: The critical stress is for edge
region given by σcritical =σe + σte -σ f.
• Winter, mid-day: The critical combination of stress is
for the edge region given by σcritical = σe+σte +σf.
• Mid-nights: The critical combination of stress is for
the corner region given by σcritical = σc + σtc.
75

76. Design of slab thicknessDesign of slab thickness
Critical stress condition
The severest combination that induce the maximum
stress in the pavement will give the critical combinations .
The flexural stress due to the combined action of traffic
loads and temperature differential between the top and
the bottom fibers of the concrete slab is considered for
the design of pavement thickness
The flexural stress at the bottom layer of the concrete
slab is maximum during the day hours when the axle
load act mid ways on the pavement slab while there is
positive temperature gradient . as shown .
This condition is likely to produce Bottom- Up
cracking(BUC). 76

77. 77
•Location of the points of maximum flexureal stresses
at the bottom of the pavement slab without tied
concrete shoulder for single , tandem , tridem axle as
shown . the tyre imprints the longitudinal to the
edges. For tied shoulder same stress will be produced
at same location. Single axle cause highest stress
followed by tandem and tridem axles respectively.

78. 78

79. During the night hours the top surface is cooler than the
bottom surface and the ends of the slab curl up
resulting in loss of support for the slab as shown . Due
to the restrained provide by the self weight of concrete
and by the dowel connections, temperature tensile.
stresses are caused at top
79

80. • Figure shows the placement of axles load close to
transverse joint when there is negative temperature
gradient during night period causing high flexural
stress at the top of the slab leading to the Top – down
cracking (TDC)
80

81. Calculation of flexural stressCalculation of flexural stress
• For bottom up cracking case the combination of load
and positive non linear temperature differential has
been considered . for BUC single /tandem has been
placed on the slab in the position . in BUC single axle
load causes the largest edge stress followed by tandem
and tridem axles . since the stress due to tridem axles
are small they were not considered for stresses analysis
For BUC.
• For TDC only one axle of single/ tandem / tridem axles
units has been considered for analysis in combination
with front front axle . front axle weight has been
assumed to be 50 percent of the rear axle unit. 81

82. Analysis has been done for the following casesAnalysis has been done for the following cases
BOTTOM – UP CRACKING
• Pavement with tied concrete shoulder for single rear
axle
• Pavement without tied concrete shoulder for single rear
axle
• Pavement with tied concrete shoulder for tandem axle
• Pavement without tied concrete shoulder for tandem
axle
TOP – DOWN CRACKING
• Paving with and without dowel bars having front
steering axles with the single tyres and the first axles of
the rear unit placed on the same panel. 82

83. CUMULATIVE FATIGUE DAMAGECUMULATIVE FATIGUE DAMAGE
ANALYSISANALYSIS
• For a given slab thickness and other parameter the
pavement will be checked for cumulative bottom up
and top down fatigue damage. For bottom up cracking
the flexural stress at the edge due to combined action
of single or tandem rear axle load and positive
temperature differential cycles are considered.
• The stress can be either selected from the stress charts
( as shown some sample figures) or by using the
equation ( shown some sample equations.. chart
explain clearly the interplay of thickness , modulus of
subgrade reaction, axle load and temperature
differential
83

84. • Similarly for assessing the TDC fatigue damagef
caused by repeated cycles of axle load and negative
temperature , flexural stress can be estimated in same
manner.
• The flexural stress is divided by the design flexural
strength of the cement to obtain the stress ratio ( SR)
84

85. 85

86. Recommended procedure for slab designRecommended procedure for slab design
The following steps may be followed for design.
• Step-1: Stipulate design values for the various
parameters.
• Step-2: select a trial design thickness of pavement
slab .
• Step-3: Compute the repetitions of axles load of
different magnitude and different categories during the
design life .
• Step-4: Find the proportions of axle load repetitions
operating during the day and night periods
86

87. • Step-5: Estimate the axle load repetitions in the
specified six hours period during the day time . the
maximum temperature differential is assumed to be
remain constant during the 6 hrs for analysis of bottom
Up cracking.
• Step-6: Estimate the axle load repetitions in the
specified six hours period during the night time .
• The maximum negative temperature differential during
night is taken as half of day time maximum
temperature differential. Built in negative temperature
differential of 50 ˚c developed during the setting of the
concrete to be added to the temperature differential for
the analysis of top – down cracking . only those
vehicle whose front and first rear axle come between
transverse joints are considered.
87

88. • Step-7: compute the flexural stresses at the edge due to
single and tandem axle load for the combined effect of
axle load and positive temperature differential during
ay time determine the stress ratio and evaluate the CFD
for single and tandem axle loads. Sum of the two CFD
should be less than 1.0 for the slab to be safe against
bottom up cracking.
• Step-8: compute the flexural stresses at the centre area
of transverse joint and the rear axle close to the
following joint in the same panel under negative
temperature differential. determine the stress ratio and
evaluate the CFD for single and tandem axle loads.
Sum of the two CFD should be less than 1.0 for the
slab to be safe against bottom up cracking . 88

89. JOINTS IN RIGIDJOINTS IN RIGID
PAVEMENTPAVEMENT
89

90. Load Transfer At The JointsLoad Transfer At The Joints
90
•It is important that the load applied on the slab is shared by
adjacent slab also for better performance of pavement.
•If load transfer across the slab is poor, distress such as
faulting pumping, and corner break occur.
•Load transfer occurs through different mechanism.
•The ability of the pavement to transfer load at joint is called
“load transfer efficiency”.
•Granular interlocking is expected along the cracks that form
at transverse joints.
•For low volume road the load transfer is expected to be
provided by interlocking.
•For higher traffic volume thicker higher dowel bars are
provided.

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92. Types Of JointsTypes Of Joints

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94. Expansion JointsExpansion Joints
• Joints are provided to allow for expansion of the slabs
due to rise in slab temperature above the construction
temperature . It also permits the contraction of slabs it
is provided in India in the interval of 50 to 60 cm for
smooth interface in winter and 90-120 cm for smooth
interface in summer .
• Maximum spacing is 140 m
• Expansion joint dowels are specially fabricated with a
cap on one end of each dowel that creates a void in the
slab to accommodate the dowel as the adjacent slab
closes the expansion joint.

95. Contraction jointsContraction joints
• These are provided to permit the contraction of slabs.
These joints are spaced closer than the expansion
joints.
• Load tranfer at this joint is by aggregate interlocking at
the joint face.
• The maximum spacing of contraction joints is 4.5 m.

96. Warping jointsWarping joints
• These are provide to relieve stresses induced due to
warping known as hinged joints.
• These joints are rarely provided

97. Construction JointsConstruction Joints
• A construction joint is defined as “a joint between
slabs that results when concrete is placed at different
times. A header and dowel basket for a transverse
construction joint are shown . After paving up to the
header, the header will be removed. The next paving
day will start with new concrete butted up against the
old concrete..
97

98. Longitudinal jointsLongitudinal joints
• A longitudinal joint is defined as a joint between two
slabs which allows slab warping without appreciable
separation or cracking of the slabs .
• Longitudinal joints are used to relieve warping stresses
and are generally needed when slab widths exceed
[4.5m] .
• To aid load transfer, tie bars are often used across
longitudinal joints. Tie bars are thinner than dowels,
and use deformed reinforcing bars rather than smooth
dowel bars.
• On soil subgrade of clay , such joints are provided to
allow differential shrinkage and swelling due to rapid
changes in subgrade moisture under the edges than the
under the centre of road.

99. • In these joints tie bars are provided to hold the
adjacent slab .
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100. Distress In Rigid PavementDistress In Rigid Pavement
• Distress Types For JPCP And JRCP:
• Cracking – divided into corner breaks, durability
(“D”) cracking, longitudinal cracking, and transverse
cracking.
• Joint Deficiencies – joint seal damage (transverse or
longitudinal), and joint spalling (transverse or
longitudinal).
• Surface Defects – divided into map cracking, scaling,
polished aggregates, and popouts.
• Miscellaneous Distresses – classified as blowups,
faulting of transverse joints and cracks, lane-to-
shoulder drop off, lane-to-shoulder separation, patch
deterioration, and water bleeding and pumping.

101. Distress Types For CRCP:
• Cracking – as described, except CRCP cannot have
corner breaks.
• Surface defects – as described.
• Miscellaneous Distresses – as above, with the
addition of punchouts, transverse construction joint
deterioration, and longitudinal joint seal damage. Also,
CRCP does not have joints, so joint faulting does not
occur.
101

102. cracking Transverse cracking

103. Longitudinal cracking

105. Advantages of Concrete PavementAdvantages of Concrete Pavement
• Longer lasting – 40 year Design Life .
• Heavy duty Pavements have generally the lowest cost.
• Pavement maintenance costs are up to 10 times
cheaper than the same for flexible pavements.
• Minimum maintenance requirements result in less
traffic disruption, minimum congestion time and as a
result Work zone safety.
• Lowest Life Cycle Cost of all Heavy Duty pavements
and highest salvage value.
105

106. • Can be constructed over poor subgrades.
• Thinner overall pavement thickness = lower
consumption of raw materials.
• Resistant to abrasion from turning actions.
• No affected by weather, inert to spills and fire.
• High abrasion durability.
• Profile durability.
• Use of waste products like flyash and slag.
• Riding quality does not deteriorate.
• Saving of fuel costs of at least 1.1% over asphalt .
• Light colour enhances night visibility 106

107. Disadvantages of Rigid PavementDisadvantages of Rigid Pavement
• To provide economics and quality, it requires larger
projects.
• Set-up costs are significant.
• On-site batch plant is essential for slip forming.
• Slip forming requires minimum 200 m runs.
• Concrete must achieve a certain strength before it can
be placed under traffic
• Repairs take longer = traffic disruption and work site
safety.
• Unless longitudinal grooving is used, tyre/road noise
can become a nuisance

108. • Issue in urban areas after 80/90 km/h speeds.
• May lose non-skid surface with time.
• Needs even sub-grade with uniform settling.
• May fault at transverse joints.
• Requires frequent joint maintenance.
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109. REFRENCESREFRENCES
109
[1] IRC-58-2011 Guidelines for the design of plain
jointed rigid pavements for highways .
[2] IRC-9-1972 Traffic census on Non- urban road.
[3] S.K. Khanna –C.E.G Justo , book of highway
engineering .
[4] R Srinivas Kumar , Book of Highway engineering .
[5] Chakroborty Book Of highway engineering.

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