Rigid Pavement_1.docx

Two lanes with paved shoulders from Ane-Ghat to Start of Ahmednagar bypass of NH-222 in the State of Maharashtra under Rigid pavement ReportNHDP-IV on EPC Basis

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Table of Contents

Chapter 1..........................................................................................................................................3

Introduction......................................................................................................................................3

1.1 General...................................................................................................................................3

1.2 Rigid pavements....................................................................................................................3

Chapter 2..........................................................................................................................................5

Design Methodology and Analysis..................................................................................................5

2.1 General...................................................................................................................................5

2.2 Factors governing design.......................................................................................................5

2.3 Design period.........................................................................................................................5

2.4 Traffic consideration..............................................................................................................5

2.4.1 Design lane.....................................................................................................................5

2.4.2 Design Traffic.................................................................................................................5

2.5 Composition of traffic in terms of axles................................................................................9

2.6 Temperature Differential.......................................................................................................9

Composition and strength of foundation.....................................................................................9

2.7 Embankment Soil...................................................................................................................9

2.7.1 Subgrade.........................................................................................................................9

2.7.2 Subbase.........................................................................................................................11

2.8 Concrete strength.................................................................................................................11

2.9 Fatigue behaviour of cement concrete.................................................................................11

2.10 Design of Slab Thickness..................................................................................................12

2.11 Design of rigid pavement as per IRC: 58-2011.................................................................13

2.11.1 Design for pavement bonded option...........................................................................14

Chapter 3........................................................................................................................................15

Conclusion.....................................................................................................................................15

3.1 Conclusion...........................................................................................................................15

ASC Infratech Pvt. Ltd. Page | 1


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LIST OF TABLES

Table No Page No

2.1 Diverted Traffic on Segment-III & Segment-IV 6

2.2 Estimation of traffic growth 7

3.1 Pavement Thickness at Location 1 15

LIST OF FIGURES

Figure No Page No

1.1 Typical Cross Section of Rigid Pavement 4

1.2 Elastic plate resting on viscous foundation 4

2.1 Chart Determining Effective CBR of Subgrade 10



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Chapter 1

Introduction

1.1 General

A highway pavement is a structure consisting of superimposed layers of processed materials

above the natural soil sub-grade, whose primary function is to distribute the applied vehicle loads

to the sub-grade. The pavement structure should be able to provide a surface of acceptable riding

quality, adequate skid resistance, favourable light reflecting characteristics, and low noise

pollution. The ultimate aim is to ensure that the transmitted stresses due to wheel load are

sufficiently reduced, so that they will not exceed bearing capacity of the subgrade. Two types of

pavements are generally recognized as serving this purpose, namely flexible pavements and rigid

pavements. This report gives an overview about rigid pavement design.

1.2 Rigid pavements

Rigid pavements have sufficient flexural strength to transmit the wheel load stresses to a wider

area below. A typical cross section of the rigid pavement is shown in Figure 1.1 rigid pavements

are placed either directly on the prepared sub-grade or on a single layer of granular material.

Since there is only one layer of material between the concrete and the sub-grade, this layer can

be called as base or sub-base course.

In rigid pavement, load is distributed by the slab action, and the pavement behaves like an elastic

plate resting on a viscous medium as shown in Figure 1.2. Rigid pavements are constructed by

Portland cement concrete (PCC) and had analyzed by plate theory instead of layer theory,

assuming an elastic plate resting on viscous foundation. Plate theory is a simplified version of

layer theory that assumes the concrete slab as a medium thick plate which is plane before loading

and to remain plane after loading Bending of the slab due to wheel load and temperature

variation and the resulting tensile and flexural stress.



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Fig 1.1 Typical Cross Section of Rigid Pavement

Fig 1.2 Elastic plate resting on viscous foundation



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Chapter 2

Design Methodology and Analysis

2.1 General

For the present project Rigid pavement design has been considered at Toll Plaza locations.Rigid

pavement design methodology is based on the guidelines of IRC: 58-2011which has been used.

2.2 Factors governing design

Following are the main factors governing design of concrete pavements:

1. Design period.

2. Design commercial traffic volume.

3. Composition of traffic in terms of single, tandem, tridem and multi-axles.

4. Climatic conditions.

5. Composition and strength of foundation.

6. Lateral placement characteristics of commercial vehicles.

7. Directional distribution of commercial vehicles.

8. Axle load spectrum.

2.3 Design period

For rigid pavements, the initial pavement structure is designed and analyzed for a performance

period of 30 years.

2.4 Traffic consideration

2.4.1 Design lane

It is the lane which carrying the maximum number of commercial vehicles. Each lane of two-

lane two-way and the outer lane of multi-lane highways are to be considered as design lane.

2.4.2 Design Traffic

Seven day 24-hour count had made for estimating average daily traffic. Generally a minimum of

5percent annual growth rate of commercial vehicles shall be taken. The collected data consists of

both day and night traffic trends, so that bottom-up cracking (BUC) formed due to day time

traffic and top-down traffic (TDC) cracking caused due to night time traffic is analysed.



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2.4.2.1 Traffic analysis

The traffic at toll plaza locations is given in Table 2.1. (Refer table 1.21 in traffic report)

Table 2.1 Total Tollable Traffic at TVC-1 at CH-4 km

Total Tollable Traffic volumeTVC-1 at Ch:184 km

SL.No Type of vehicles PCU FactorNo of

VehiclesNo of Vehicles

PCU

1

Car/ Jeep / Van+ Taxi-car/ jeep/ van/Utility

1 1486 1486

2 Mini Buses 1.5 11 173 Bus 3 185 556

4

LCV+ LVG(Mini LCV/ Pick Up /Utility)

1.5 224 336

5 2 Axle Truck 3 214 643

6 3 Axle Truck 3 97 291

7MAV+ Heavy Mach+ Oversize. 4.5 19 86

TOTAL 2237 3415

For the current project the Total Two-way Commercial Traffic (cvpd) in the year of completion

of construction is 364cvpd (2Axle & 3Axle = 343, MAV = 21).

The average annual growth of commercial vehicles is taken as 5%.

The cumulative number of commercial vehicles during the design period may be

estimated from the following expression as shown in Equation 2.1

C=365× A {(1+r )n−1}

r(2.1)

Where

C = Cumulative number of commercial vehicles during the design period

A = Initial number of commercial vehicles per day in the year when the road is opened to traffic

r = Annual rate of growth of commercial traffic volume (expressed as decimal)

n = Design period in years.



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Table 2.2 Estimation of traffic growth

Year AADT Total Traffic (No.) Cumulative Traffic

2Axle & 3 Axle MAV CV* 2Axle & 3 Axle MAV CV*

2014 311 19 330 113515

2015 327 20 347 119191

2016 343 21 364 125150 7646 132796 132796

2017 360 22 382 131408 8028 139436 272232

2018 378 23 401 137978 8430 146408 418640

2019 397 24 421 144877 8851 153728 572368

2020 417 25 442 152121 9294 161415 733782

2021 438 27 464 159727 9758 169485 903268

2022 459 28 488 167713 10246 177960 1081227

2023 482 29 512 176099 10758 186857 1268085

2024 507 31 538 184904 11296 196200 1464285

2025 532 32 564 194149 11861 206010 1670295

2026 559 34 593 203857 12454 216311 1886606

2027 586 36 622 214049 13077 227126 2113733

2028 616 38 653 224752 13731 238483 2352215

2029 647 39 686 235990 14417 250407 2602622

2030 679 41 720 247789 15138 262927 2865550

2031 713 44 756 260178 15895 276074 3141623

2032 748 46 794 273187 16690 289877 3431501

2033 786 48 834 286847 17524 304371 3735872

2034 825 50 876 301189 18401 319590 4055461

2035 866 53 919 316249 19321 335569 4391031

2036 910 56 965 332061 20287 352348 4743378

2037 955 58 1014 348664 21301 369965 5113343

2038 1003 61 1064 366097 22366 388463 5501807

2039 1053 64 1117 384402 23484 407886 5909693

2040 1106 68 1173 403622 24659 428281 6337974

2041 1161 71 1232 423803 25892 449695 6787669

2042 1219 74 1294 444993 27186 472180 7259848

2043 1280 78 1358 467243 28545 495789 7755637

2044 1344 82 1426 490605 29973 520578 8276215

2045 1411 86 1498 515136 31471 546607 8822821

C = 8822821



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Average No of axles per commercial vehicle, (each tandem axle set is counted as one

axle unit. Similarly, each tridem axle set is counted as one axle) is 2.35

Cumulative number of standard axles during design period is C * 2.35 = 20743603

Proportion of traffic in predominant direction is 0.5

Design traffic factor (0.25 for 2-lane 2-way. For multilane highways the value is 0.25 X

0.5) is 0.125

The edge flexural stress caused by axle loads for bottom-up cracking is the maximum when outer

tyre imprint touches the longitudinal edge. Stress in the edge region is low when the tyre imprint

is 150mm away from longitudinal edge. The edge flexural stress is small when the wheels are

close to the transverse joints.

Traffic factors for BUC and TDC are given below:

Traffic factor for BUC analysis (for six-hour period during day) is 0.2

Traffic factor for TDC analysis (for six-hour period during night) is 0.3

It is recommended that 25 percent of the total traffic in the direction of predominant traffic may

be considered for design of pavement for bottom-up cracking.

Design axle repetitions for BUC analysis (for 6 hour day time traffic) is 0.2*0.25*

20743603 = 1037180

The design traffic for top-down cracking analysis will be a portion of the design traffic considered for bottom-up cracking analysis.

Proportion of vehicles with spacing between front and the first rear axle less than the

spacing of transverse joints is 0.55

Design axle repetitions for TDC analysis (for 6-hour night time traffic) is

0.55*0.3*0.25*20743603 =855674

Expected number of applications of different axle load groups during the design period can be

estimated using the details of commercial traffic volume expected rate of growth of commercial

traffic and the information about axle load spectrum and the number of single, tandem and

tridem axles obtained from axle load survey. Since front axles (steering axle) with single wheels



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on either side cause only negligible bottom-up fatigue damage, it is only the rear axles that may

be included in the axle load spectrum.

2.5 Composition of traffic in terms of axles

Proportion of Front single (steering) Axles = 40.4%

Proportion of Rear single Axles = 38.6%

Proportion of tandem Axles =17.5%

Proportion of Tridem Axles =3.4%

2.6 Temperature Differential

Temperature differential between the top and bottom fibres of concrete pavements causes the

concrete to curl, giving rise to stresses. Recommended temperature differentials for concrete

slabs for different states of India are given in IRC: 58-2011.

As the project is in Maharashtra state, Maximum day-time Temperature Differential in

slab, °C (for bottom-up cracking) is 20.3°C

Night-time Temperature Differential in slab, °C (for top-down cracking) is 20.3/2 + 5

=15.15°C

It is suggested that the maximum positive and negative temperature differentials are assumed to

be constant for the six hour period during the day between 10 AM and 4 PM and for the six hour

period between 0 AM to 6 AM during night hours respectively.

Composition and strength of foundation

2.7 Embankment Soil

Behaviour of the embankment soils had to be studied before so that if it contains soils like

expansive clays, marine clays, soft clays, black cotton soil etc. are harmful to the subgrade soil.

2.7.1 Subgrade

Smaller diameter plate can be used in case of homogeneous foundation from practical

consideration and the test values obtained with plates of smaller diameter may be converted to

the standard 750 mm plate value using Equation

k 750=k ∅ (1.21∅+0.078) (2.2)



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where

(I) = plate diameter, meter

k ∅ = modulus of subgrade reaction (MPa/m) with plate diameter ∅

k 750 = modulus of subgrade reaction (MPa/m) with plate diameter of 750 mm

For estimating the effective CBR value of subgrade, the CBR and ‘k’ value of embankment soil

below 500mm subgrade should be determined. From the figure 2.1, effective CBR of subgrade

can be determined.

Fig 2.1 Chart Determining Effective CBR of Subgrade

If there is a significant difference between the CBRs of the select subgrade and embankment

soils, the design should base on effective CBR as per IRC 58-2011. The embankment CBR is

considered as 7% and subgrade CBR as 15% for the entire stretch, so the effective CBR of the

subgrade is determined as 12.5% all along the stretch by using the graph as shown in Figure 2.1



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Effective modulus of subgrade reaction of foundation is 300 MPa/m

Modulus of subgrade reaction of subgrade is 62 MPa/m

2.7.2 Subbase

The main purpose of the subbase is to provide a uniform, stable and permanent support to the

concrete slab laid over it. In the light of these requirements, subbase of Dry Lean Concrete

(DLC) having a 7-day compressive strength of 10MPa as per IRC-SP: 49 is recommended.

Thickness of Granular Subbase is 150mm

Thickness of Dry Lean Concrete subbase is 150mm

2.8 Concrete strength

Flexural strength of concrete is required for the purpose of design of concrete slab. Flexural

strength can be obtained after testing the concrete beam as per procedure given in IS 516.

M40 grade is considered for Pavement Quality Concrete (PQC)

Unit weight of Concrete is 24 KN/m3

Usually, concrete design is based on 28 days strength.

Modulus of elasticity and poison’s ratio of concrete E and µ values are taken as 30000

MPa and 0.15 respectively for the concrete with 28 day flexural strength of 4.5 MPa.

Radius of relative stiffness m= 0.622

2.9 Fatigue behaviour of cement concrete

The ratio between the applied flexural stress and the flexural strength of concrete is known as

stress ratio (SR).

If the SR is less than 0.45 implies concrete can sustain infinite number of repetitions and more

than 0.45, number of load repetitions required to cause cracking decreases. Relation between

fatigue life (N) and SR is given below

N = unlimited for SR<0.45



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N=[ 4.2577SR−0.4325 ]

3.268

When0.45≤SR≤0.55 (2.3)

log10 N=¿ 0.9718−SR0.0828

For SR>0.55¿ (2.4)

These equations are used for the analysis of bottom-up and top-down cracking.

2.10 Design of Slab Thickness

Type of pavement considered

Carriageway Two lane two way

Shoulders :- Tied concrete shoulders ? (yes/no) yes

Transverse joint spacing (m) 4.5

Lane width (m) 3.5

Transverse Joints have dowel bars? (yes/no) yes

The flexural stress due to the combined action of traffic loads and temperature differential

between the top and bottom fibres of concrete slab is considered for design of pavement

thickness.

The trial thickness of concrete slab is taken as 260mm.

Load Transfer Efficiency Factor for TDC analysis β =0.66 for joints with dowels.

The flexural stress at the bottom layer of the concrete slab is the maximum during the day time

and when the excess axle loads act midway on the pavement slab produces ‘bottom-up cracking’.

In this type of cracking, Single axles cause highest stress followed by tandem and tridem

respectively.

During the night hours, the top surface is cooler than the bottom surface and the slab curl up

resulting in loss of support.

For BUC analysis:

Front single (steering) Axles = Proportion of Front single* Design axle repetitions for

BUC analysis = 0.404%* 1037180= 419365



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Rear single Axles = Proportion of Rear single Axles* Design axle repetitions for BUC

analysis = 0.386%* 1037180 = 400644

Tandem Axles = Proportion of Tandem Axles* Design axle repetitions for BUC analysis

= 0.175%* 1037180 = 181600

Tridem Axles = Proportion of Tridem Axles* Design axle repetitions for BUC analysis =

0.034%* 1037180 = 35571

For TDC analysis:

For location 1:

Front single (steering) Axles = Proportion of Front single* Design axle repetitions for TDC

analysis = 0.404%* 855674= 345976

Rear single Axles = Proportion of Rear single Axles* Design axle repetitions for TDC

analysis = 0.386* 855674= 330531

Tandem Axles = Proportion of Tandem Axles* Design axle repetitions for TDC analysis =

0.175* 855674= 149820

Tridem Axles = Proportion of Tridem Axles* Design axle repetitions for TDC analysis =

0.034* 855674= 29346

The cumulative fatigue damage expressions for Bottom-up cracking and Top-down cracking are

given below

CFD (BUC )=∑i

j n iN i

(10 AM ¿4 PM ) (2.5)

CFD (BUC )=∑i

j n iN i

(0 AM ¿6 AM ) (2.6)

Where Ni = allowable number of wheel load and temperature differential cycles for ith load group.

ni = Predicted number of wheel load and temperature differential cycles for ith load group.

2.11 Design of rigid pavement as per IRC: 58-2011

The axle load spectrum data, Bottom-up Cracking fatigue analysis for day-time (6 hour) traffic

and positive temperature differential, Top-Down Cracking fatigue analysis for night-time (6



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hour) traffic and negative temperature differential, Design of dowel bars and tie bars of two

locations are shown in Annexure 1a, 1b, 1c, respectively.

2.11.1 Design for pavement bonded option

Subgrade CBR (%) = 15

Granular Subbase Thickness (mm) = 150

Effective k-value from Tables 2 and 3 (MPa/m) = 69.2For k of 75.9 MPa/m and for

Doweled Joint and Tied Concrete Shoulders,Slab Thickness

(m) =0.26

Trial Slab thickness (m) over DLC, h1 0.235

Provide DLC thickness (m), h2 0.15

Elastic Modulus of Pavement Concrete (MPa), E1 30000

Elastic Modulus of DLC (MPa), E2 13600

Poisson's Ratio of Paving Concrete, m1 0.15

Poisson's Ratio of DLC, m2 0.2

Depth to Neutral axis, m (See Fig.6) 0.16

Flex Stiffness of design Slab 44.95

Flex Stiffness of Partial Slab Provided 32.56

Flex Stiffness of DLC 18.24

Total Flexural Stiffness Provided = 32.56 + 18.24 = 50.80

which is more than the Flexural Stiffness of the Design Slab = 44.95

Hence, Provide a Slab of thickness (m) 0.2 over DLC of thickness (m) 0.15



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Chapter 3

Conclusion

3.1 Conclusion

The following gives the thickness of different layers of rigid pavement in without pavement bonded option and with paved bonded option.

Table 3.1 Pavement Thickness at Location 1

Description Without pavement bonded option

With pavement bonded option

Pavement Quality Concrete (mm)

260 200

Dry Lean Concrete (mm) 150 150

Granular Subbase (mm) 150 200

Subgrade (mm) 500 500

Length, Diameter and spacing of Dowel bars (mm)

500, 25 & 300

Length, Diameter and spacing of tie bars (mm)

650, 12 & 700


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