Irf ts 3.5.1 ramesh cv_0259-000307_pavement with csus_21.10.2013_09_nov(r1)

17th IRF World Meeting & Exhibition
Riyadh, November 10 - 14, 2013
Better Roads. Better World.
Ramesh Chand Vishwakarma
Senior Pavement Specialist
Parsons
IMPROVING PERFORMANCE OF
FLEXIBLE PAVEMENTS WITH USE OF
SEMI RIGID MATERIALS IN
BASES AND SUBBASES

CONTENTS
2
1. Background and Introduction
2. Objectives
3. Proposed Solutions
4. Evaluation of Options
5. Implementation of Solutions
6. Functional Performance (Ride Quality)
7. Conclusions and Recommendations

1. BACKGROUND AND INTRODUCTION
3
Most perceivable component of a road:
Ride Quality: for the road user
Pavement Life: for the road agency
Improvement in structural and functional performance and longevity can be
achieved with use of semi rigid materials (cement stabilized).
Because, Semi Rigid Materials in base/ subbase provides…
a bottom supported and horizontally confined layers system above it,
changes the stress state in granular layers and
reduces subgrade strains.
improves vertical sectional integrity individually as well as a layer group.
prevents effects of variability in subgrade support,
reduces the compressibility of layers above it and
gives better ride quality.
Use of stabilized base/ subbase in heavy duty pavement is cost effective and
sustainable way of reducing total thickness and carbon foot print.

4
Sustainable pavement design, successfully implemented for the first time in UAE.
Pavement design was done as per AASHTO guidelines and checked with
KENLAYER software for structural performance.
Sustainable Pavement
Project: Strengthening and widening of 9.5 km long stretch of Sheikh Mohammad
Bin Zayed Road (Emirates Road, E-311) in Sharjah, United Arab Emirates (UAE).
It was designed as INVERTED PAVEMENT by using semi rigid materials i.e.
cement stabilized upper subbase (CSUS) with 4% cement, which improved
pavement performance, life and the ride quality.

5
Project Location

6
Highway After Widening -5X5 Lanes
Highway Before Widening -3X3 Lanes

7
Highway Before Widening
Photo Photo
Pavement Condition

8
Highway After Widening
Photo Photo
New Pavement

9
NTS
Detail A Detail B
Carriageway After Widening

2. OBJECTIVES
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Quite high cumulative ESALs 223 Million Standard Axles
Stabilised Subbase, But Why?
Constraints/ Challenges Opted Solution
Widened to 5x5 lanes from 3x3 lanes Outer Truck lanes & CD roads with CSUS
Existing truck lane is dilapidated Existing pavement in truck lanes reconstructed
Change in alignment and profile Design/construction covered full lane width
No wheel path on pavement joint Wheel path-free joint for fast construction
Heavy axle loads from Hamriya port Accounted in vehicle damage factor
Variability in subgrade support CSUS interface between WMM and GSB
High ground water / poor drainage CSUS-moisture barrier & GSB-drainage layer
Fund constraint Substantial Saving with design & specification
Sustainable pavement Reduced carbon foot print

3. PROPOSED SOLUTION
11
Asphalt Layers =11 cm
Wet Mix Macadam =16 cm
Granular Subbase = 15 cm
Existing Pavement- Overlaid
(Used for 3-car lanes with strengthening)
Total Thickness = 42cm
Cement Stabilized Upper Subbase = 15 cm
Proposed Pavement- New Construction
(With CSUS- for 2-outer truck lanes)
Total Thickness = 79cm
Existing and Proposed Pavement
Heavy Axle Load Interface: High tire pressure
(> 120 psi) and high axle load
Medium Axle Load Interface: Medium tire pressure
(60-120 psi) and average to high axle load
Heavy Axle- High Volume: Airport Taxiways
Heavy Axle- Medium Volume: Ports
Medium Axle- High/ Medium Volume: Routes
connecting Port, Interstate Highways
Stabilization : In upper and/or middle layers Stabilization: In middle or lower layers
Layer Stabilization Requirement

12
Stabilization
Semi rigid materials: generally chemically stabilized, designed, plant produced, paved,
compacted and cured to meet strength and other requirements specified.
Stabilization is generally undertaken…
 To correct any deficiencies in granular materials and subgrades,
 To increase strength or bearing capacity of materials or making provision for
construction traffic,
 To reduce the permeability and/or moisture sensitivity, and loss of strength,
 To provide cost-effective pavement configurations with use of stabilized layers,
 To improve the wearing characteristics of unsealed pavements.
If stabilized layer is in upper or middle of pavement, more quality of stabilization is
required and specification should be framed accordingly.
3. PROPOSED SOLUTION

4. EVALUATION OF OPTIONS
13
Type -1
Thickness = 84cm
Cement Stabilized Upper Subbase = 15 cm
Type -2 (with CSUS)
Thickness = 79cm
Type -3 (CSUS replaced by GSB)
Thickness = 79cm
Comparison of Pavement Types
Materials Elastic Modulus (MPa)
Asphalt (At reference temperature=200 Celsius) 2760
Wet Mix Macadam (Standard mix) 195
Cement Stabilized Upper Subbase (CSUS) with 4% OPC, Specified UCS =5 MPa
Considered fully cracked after 15 years
1840
Granular Subbase (Standard mix) 110
Subgrade, under high GWT and poor drainage with CBR value ~12% 53
Tire pressure for Axle Load (80,000 kN), Normal range ~ 551-896 kPa 758.4 kPa
Analysis and Design Parameters
(Visco-elastic layer system)
Same
ESALS
Same
thickness

14
Options with same Traffic Loading
Analysis Results Pavement Type -1 Pavement Type -2 (with CSUS)
Load Carrying Capacity (MSA) 223 223
Compressive Strain (µε) at Subgrade 369.9 282.8
Allowable Repetition of Standard Axle 6,350,242,653 41,593,436,521
Increase in Number of Repetition (%) 555%
Stress State at Mid Depth of WMM
 Major Principal Stress (kPa) 97.2 138.3
 Minor Principal Stress (kPa) -0.1 12.9
 Intermediate Principal Stress (kPa) 7.1 23.0
 Deviator Stress (kPa) 97.3 125.4
Improvement in stress state Deviator stress +28.1 kPa, (+28.94%)
Vertical Stress at Subgrade (kPa) 21.8 18.3 (-16.15%)
Improvement in stress on subgrade Reduced stress on subgrade
Pavement Cost Per Square Metre
410.85 AED (111.8
USD)
386.88 AED (105.27 USD)
Cost Reduction (%) -5.84 % {-23.98 AED (6.52 USD)}
Pavement Type-2 is cost effective with efficient utilization of WMM with reduction in
subgrade stress than Pavement Type-1 with same design traffic and SN.same design traffic and SN.

15
Advantage of Part Stabilization of GSB
Analysis Results Pavement Type -2 (with CSUS)
Pavement Type -3 (with
CSUS replaced by GSB)
Load Carrying Capacity (MSA) 223 (+126.8% More ESALs) 98.3
Compressive Strain (µε) at Subgrade 282.8 401.3 (More strain)
Allowable Repetition of Standard Axle 41,593,436,521 3,590,017,137
Decrease in Number of Repetition (%) -91.4% (Less repetition)
Stress State at Mid Depth of WMM
 Major Principal Stress (kPa) 138.3 131.3
 Minor Principal Stress (kPa) 12.9 1.4
 Intermediate Principal Stress (kPa) 23.0 11.5
 Deviator Stress (kPa) 125.4 129.9
Qualitative improvement in stress state
of granular layer
Comparable deviator stress
-4.5 kPa, (~3.45 %)
Vertical Stress at Subgrade (kPa) 18.3 (-22.7 %) 23.6
Qualitative improvement in stress state Reduced stress on subgrade
Pavement Cost Per Square Metre 386.88 AED (105.27 USD) 352.45 AED (95.9 USD)
Cost Increase (%) +9.77 % {+34.43 AED (9.37USD)}
With same total thickness (Pavement Type-3), stabilization of upper subbase in Pavement Type-
2, increases traffic loading capacity, reduce subgrade stress with very little additional cost.
same total thickness

5. IMPLEMENTATION OF SOLUTIONS
16
Construction Specifications

17
Internal Curing: CSUS was roller compacted and covered with first layer of WMM.

18
Exposed CSUS layer Texture of CSUS
Advantages with Internal Curing (no wet curing).
 It minimized shrinkage block cracks,
 It resulted in increase in-situ strength,
 It saved water for curing and project construction time,
 It enhanced interface bond with granular layers,
 It delayed cracking potential due to post construction traffic.

19
Mix Design and Quality Assurance
Performance of stabilized layers is very sensitive to variation in quality of its
ingredients, production, laying & compaction and curing, therefore a proper
inspection and testing plan (ITP) must be developed to assure quality of end product.
 Compressive Strength – mix must develop unconfined compressive strength as
per design.
 Durability –mix should resist the deteriorating effects of environmental variation.
 Compacted Density –mix should be designed to achieve maximum unit weight in-
situ.
 Volumetric Stability –mix must maintain its volumetric dimensions and resist
potentially expansive chemical reactions after placement and compaction.
 Modulus – conformity test must be conducted initially on the design mix and
intermittently on plant produced mix to ensure there is no significant deviation in
presumptive design modulus.

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Design Precautions with Cement Stabilised Layers
Rate of deterioration depends mainly on the level of stabilization, thickness of
stabilised layer and on the stiffness of the subgrade support.
Cement stabilized materials initially act as a stiff bottom supporting material, but it
deteriorates into blocks (if good stabilization) and loose clumps or separated smaller
blocks (if average stabilization).
It is not the only structural requirement which governs the use of stabilized layer for
load transfer but also other specific requirements for the project.
Even a properly designed pavement (thickness) may lose its performance life to
half; in case of poorly designed mix of stabilized materials. Therefore, the materials
specifications is equally important while designing a pavement with stabilized layer.
Cement stabilized bases should not be directly overlaid by dense graded HMA,
rather a thin open graded asphalt interface layer (normally asphalt macadam) should
be provided to avoid reflective cracking.
Same specification should not be applied in all projects. Fine tuning of it, is a must!

6. FUNCTIONAL PERFORMANCE (RIDE QUALITY)
21
Improvement in Ride Quality
Left Carriageway Right Carriageway
It was noticed that there is a significant improvement in ride quality of pavement with
cement stabilized subbase layer on both direction of carriageway of Emirates Road.
Completed sections of Emirates Road, E-311 with CSUS layer

22
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
0 0.2 0.4 0.6 0.8 1 1.2 1.4
IRIValue
Chainage (km)
IRI Value on Lane 1, 2 and 3 from Dubai towards Ajman (From km 25+400 To km 26+780)
Lane-1 Lane-2 Lane-3 Average for Lane-1 (0.65)
Average for Lane-2 (0.65) Average for Lane-3 (0.66) Max. IRI Allowed (0.90)
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
0.000 0.200 0.400 0.600 0.800 1.000 1.200 1.400
IRIValue
Chainage (km)
IRI Value on Lane 1, 2 and 3 from Ajman towards Dubai (From km 24+110 To km 22+440)
Lane-1 Lane-2 Lane-3 Average for Lane-1 (0.75)
Average for Lane-2 (0.75) Average for Lane-3 (0.73) Max. IRI Allowed (0.90)
6. FUNCTIONAL PERFORMANCE (RIDE QUALITY)
Ride quality test shows IRI value achieved is much less than 0.9 m/km

7. CONCLUSION AND RECOMMENDATION
23
Conclusion and Recommendation
Stabilized subbase layer enhances performance of load bearing base above it by
increasing it’s stress state uniformly with bottom support & horizontal confinement.
Decision to stabilization of a layer should be in line with the requirement of tire
pressure, axle load, number of repetition and achievable mix properties with
proper specification and workmanship.
Stabilized layers between subgrade and asphalt layers reduces variability in
subgrade support from bottom, which in turn reduces the compressibility of layers
above it. This gives better ride quality & maintains vertical integrity for longer life.
The use of stabilized base/ subbase is a cost effective with lower life cycle cost.
It is a sustainable way of reducing total thickness of the pavement due to heavy
axle loads on truck routes and reducing the carbon foot print to the environmental.

24
Thank You!
Ramesh Chand Vishwakarma
Senior Pavement Specialist
Parsons

… Video of Completed Section
25

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Use stabilised base/subbase with confidence, because it gives better life cycle
cost and performance.
Do not reject a technology!
 Design stabilised interlayer materials and thickness for loading interfaces.
 Produce a quality mix.
 Write/review a proper specification for construction for specific project.
 Produce a pavement performance criteria with quality mix.
Way Forward
… FURTHER MESSAGE ???
The case study shows, cost saving due to adoption of Cement Stabilized Upper
Subbase (CSUS) was approx. AED 9.00 (~USD 2.45) million for project (9.5km)
just for adding two truck lanes and CD roads and better ride quality.
More experience of materials engineering & of practical construction issues, will
reduce fear of unknown from the minds of designers in using semi rigid materials
which will lead to construction of cost effective and sustainable pavements.

Irf ts 3.5.1 ramesh cv_0259-000307_pavement with csus_21.10.2013_09_nov(r1)

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