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

17th IRF World Meeting & ExhibitionRiyadh, November 10 - 14, 2013

Better Roads. Better World.

Ramesh Chand VishwakarmaSenior Pavement SpecialistParsons

IMPROVING PERFORMANCE OF FLEXIBLE PAVEMENTS WITH USE OF

SEMI RIGID MATERIALS IN BASES AND SUBBASES


Better Roads. Better World.2

CONTENTS

1. Background and Introduction2. Objectives3. Proposed Solutions4. Evaluation of Options5. Implementation of Solutions6. Functional Performance (Ride Quality)7. Conclusions and Recommendations



1. BACKGROUND AND INTRODUCTION

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.



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.



Project Location




Highway After Widening -5X5 Lanes


Highway Before Widening -3X3 Lanes



Highway Before Widening

Photo 13

Photo 14

Pavement Condition




Highway After Widening

Photo 13

Photo 14

New Pavement





NTS

Detail A Detail B

Carriageway After Widening



2. OBJECTIVES

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

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 TaxiwaysHeavy 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



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




Type -1Thickness = 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) 195Cement Stabilized Upper Subbase (CSUS) with 4% OPC, Specified UCS =5 MPa

Considered fully cracked after 15 years1840

Granular Subbase (Standard mix) 110Subgrade, under high GWT and poor drainage with CBR value ~12% 53Tire 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



Options with same Traffic Loading

Analysis Results Pavement Type -1 Pavement Type -2 (with CSUS)Load Carrying Capacity (MSA) 223 223Compressive Strain (µε) at Subgrade 369.9 282.8Allowable Repetition of Standard Axle 6,350,242,653 41,593,436,521Increase 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.

Saving in Pavement Cost:~ AED 9.0 million (USD 2.45

million) for the project (9.5km) by use of Cement Stabilized Upper

Subbase (CSUS) in two truck lanes and CD roads on either side of

existing pavement.



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 3,590,017,137Decrease 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) 125.4 129.9Qualitative improvement in stress state of granular layer

Comparable deviator stress -4.5 kPa, (~3.45 %)

Vertical Stress at Subgrade (kPa) 18.3 (-22.7 %) 23.6Qualitative improvement in stress state Reduced stress on subgradePavement 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

Double the Pavement Life byPart Stabilization of Upper

Subbase!



5. IMPLEMENTATION OF SOLUTIONS

Construction Specifications





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





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.



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.



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)

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



-0.1 0.4 0.9 1.40.30

0.50

0.70

0.90

1.10

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-3Average for Lane-1 (0.65) Average for Lane-2 (0.65) Average for Lane-3 (0.66)

Chainage (km)

IRI V

alue

-0.200 0.000 0.200 0.400 0.600 0.800 1.000 1.200 1.4000.30

0.50

0.70

0.90

1.10

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-3Average for Lane-1 (0.75) Average for Lane-2 (0.75) Average for Lane-3 (0.73)Max. IRI Allowed (0.90)

Chainage (km)

IRI V

alue

6. FUNCTIONAL PERFORMANCE (RIDE QUALITY)

Ride quality test shows IRI value achieved is much less than 0.9 m/km



7. CONCLUSION AND RECOMMENDATION

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.



Thank You!

Ramesh Chand VishwakarmaSenior Pavement Specialist

Parsons



… Video of Completed Section



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.