The Use of FWD for Pavement Monitoring: Case Studies

1
The Use of FWD for Pavement Monitoring Case
Studies

• Impulsive Matters 2 Use of FWD for quality
  control
• Heriot-Watt University, Edinburgh, Scotland
• 19 November 2003

• Bachar Hakim and Martyn Jones
• Scott Wilson Pavement Engineering

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The Use of FWD for Pavement Monitoring Case
Studies

• Contents
• Unbound Foundation Performance Testing
• Lean Concrete and Pavement Quality Concrete
• Crack and Seat Projects
• Bond between Pavement Layers

3
Foundation Performance Testing

• Main Objectives
• QUALITY
• Ensure design assumption construction
• COST ENVIRONMENTAL SAVINGS
• Greater flexibility in use of marginal
  materials, stabilised, secondary recycled
  materials

4
Foundation PerformanceParameters and Tests-

• Strength (CBR)
• e.g. Dynamic Cone Penetrometer (DCP)
• Stiffness (MPa)
• Dynamic plate (FWD, GDP Prima)
• Density (Kg/m3)
• Nuclear Density Meter (NDM)
• Rutting (mm)
• Trafficking Trial

5
Foundation Performance Tests - Unbound
Stabilised Layers

• Implementation of Highway Agency (HA) Draft
  Performance Specification for Subgrade and
  Capping
• Prepared by Consortium, SWPE, Nottingham and
  Loughborough Universities
• Similar Performance Specification for
• Sub-base underway, by TRL

6
Implementation Phase Trials

• Jersey Airport (Taxiway Alpha)
• First Contractual Use of Specification
• A2 M2 (Kent)
• Various Cappings including Cement Stabilised
  Chalk, Ragstone (local sandstone) and Recycled
  Crushed Concrete
• A27 Polegate (Sussex)
• Lime/Cement Stabilised Weald Clay
• A43 Towcester to M40 (Northampton)
• Oolitic Limestone and Planings
• Doncaster North Bridge
• Urban Widening of Carriageway, granular capping
• A63 Selby Baypass
• Sand capping and sand/PFA sub-base
• Tilbury Docks Berths 41-43
• Crushed Concrete capping and sub-base

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FOUNDATION Design for Permanent Works - Long Term
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FOUNDATION Design for Construction - Short Term
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Long Term Capping Thickness Design - A
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Typical Capping Material Properties
Class Description Layer Stiffness (MPa)
6F1 Selected granular material (Fine grading) 60
6F2 Selected granular material (coarse grading) 60 (Sand Gravel)
6F2 Selected granular material (coarse grading) 80 (Chalk)
6F2 Selected granular material (coarse grading) 100 (Other crushed rock)
6F2 Selected granular material (coarse grading) 120 (Recycled crushed concrete)
6F3 Selected granular material 150
9A Cement stabilised well graded granular material 80
9B Cement stabilised silty cohesive material 80
9C Cement stabilised conditioned pulverised fuel ash cohesive material 80
9D Lime stabilised cohesive material 80
Type 1 Sub-base 150
The stiffness quoted is conservative.
Depending on the soil type and level of
stabilisation used much higher values can be
obtained.
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Correlation of German Dynamic Plate (GDP) with
FWD- Stiffness Testing
14
Prima Dynamic Plate- Stiffness Testing
15
Dynamic Plate TestsStiffness Performance
Requirements

• Finished surface of capping shall-
• gt40MPa 8 from 10 consecutive tests
• 25MPa absolute minimum
• Minimum 50 tests / trial area
• Representative trial areas
• Cut, Fill, Material Changes
• Routine testing at 10m intervals in each lane

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Rutting Tests - Requirements

• If capping used in a haul route, and subsequently
  included in the works, then rutting under
  construction traffic needs to satisfy-

Rut depth (mm) Capping Thickness (mm)
30 lt 250
40 gt 250 lt 500
50 gt 500
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Trafficking TrialRutting Tests
18
Trafficking TrialRutting Measurements
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A Performance Specification for Capping and
Subgrade - Summary

• Extensive testing and verification over 6 years
• Implementation phase has identified minor changes
  to 1999 Draft
• Successfully trialled at Jersey Airport, with
  significant savings
• Provides a path for greater use of secondary
  aggregates/marginal materials/stabilised ground
• Prediction of long-term performance remains an
  issue, especially with moisture susceptible
  materials

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Capping Trial Case Study
21
Capping Trials
Compaction of capping layer
Capping layer was trafficked 50 times
22
FWD and GDPT on Capping
Nuclear Density Testing
23
Capping Wetting
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Rutting and DCP testing
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Foundation Assessment of Existing Pavements
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A19 DBFO Foundation Assessment of Existing
Pavements

• Concrete slab failure/settlement in Lane 1
• Replacement with bituminous inlay is required
• Unbound foundation stiffness assessment is needed
  before laying the bituminous materials to ensure
  that the pavement design life is achieved

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Concrete Slab Failure
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Removal of PQC Slabs
29
Rolling the Unbound Materials
30
Performance Evaluation Using Dynamic Plate Tests
(GDP Prima)
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Jersey Airport Performance Specifications
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Jersey Airport ALPHA TAXIWAY PROJECT
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Alpha Taxiway Pavement

• Limited local aggregate performance (quarried
  granite aggregates with some fine quartz dune
  sand)
• Uneconomic to import aggregates due to high
  Harbour Dues Charges

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Pavement Development

• Site Investigation
• Materials Characterisation
• Capping Trials, CBM, PQC
• Design Parameters
• Performance Monitoring
• Top of Capping Stiffness (GDPBT), Damage to
  Subgrade (Rut Limit) and Compaction (Density)
• CBM and PQC strengths
• Additional FWD Tests
• CBM stiffness
• PQC slab stiffness, joints performance,
  corner/edge deflections

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FWD Test Results
Section Statistics Effective Stiffness (MPa) Effective Stiffness (MPa) Effective Stiffness (MPa)
PQC CBM Subgrade
CBM 50ile 15ile - - 8400 4700 100 80
PQC 50ile 15ile 34300 30200 5400 3800 130 120
Section Layer Thickness (mm) Layer Thickness (mm)
PQC CBM
CBM 0 150
PQC 320 150
Joint Type Statistics Joint Parameters Joint Parameters Joint Parameters Joint Parameters
d3-d4 (mm) d4/d3 () ?1 (deg x 10-3) ??1-?2? (deg x 10-3)
Transverse Joints 50ile 85 (or 15) ile 12 15 96 95 6.5 8.4 1.7 2.4
Longitudinal Joints 50ile 85 (or 15) ile 133 259 63 39 0.0 -5.0 5.9 10.3
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FWD Slab Edge and Corner Test Results
Location Statistics Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3)
d1 d2 d3 d4 d5 d6 d7 d1 - d3 d3 - d4
Slab Centres 50ile 85ile 318 364 290 340 265 314 254 302 202 242 153 185 101 124 48 56 12 13
Slab Edges 50ile 85ile 472 583 435 550 399 514 381 498 323 400 230 288 148 200 57 79 15 18
Slab Corners 50ile 85ile 422 527 379 487 349 451 334 432 273 353 194 265 129 190 56 83 15 17
Location Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3) Normalized FWD Deflections (mm x 10-3)
d1 d2 d3 d4 d5 d6 d7 d1 - d3 d3 - d4
Slab Edges 49 50 50 50 60 50 46 19 22
Slab Corners 33 31 32 32 35 26 28 16 25
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COST SAVINGS



39
COST SAVINGS


305

150
COST SAVING
HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED
GIVING 10 REDUCTION IN THICKNESS.   SECONDARY
AGGREGATES FOR BOUND BASE 30 COST SAVING.  
158,000 295,000
40
COST SAVINGS


305

150
300
COST SAVING
HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED
GIVING 10 REDUCTION IN THICKNESS.   SECONDARY
AGGREGATES FOR BOUND BASE 30 COST SAVING.   USE
OF MUDSTONE CAPPING FROM EXCAVATIONS IN LIEU OF
QUARRY SUPPLIED TYPE 1 SUB-BASE 90 COST SAVING
158,000 295,000 237,000
41
COST SAVINGS


305

150
300
COST SAVING
HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED
GIVING 10 REDUCTION IN THICKNESS.   SECONDARY
AGGREGATES FOR BOUND BASE 30 COST SAVING.   USE
OF MUDSTONE CAPPING FROM EXCAVATIONS IN LIEU OF
QUARRY SUPPLIED TYPE 1 SUB-BASE 90 COST SAVING
158,000 295,000 237,000 TOTAL 690,000
Materials development costs 30,000
42
FWD Testing on Cracked and Seated Concrete
Pavement
43
Crack and Seat of Concrete Pavement
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Joints improvement after CS
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Stiffness Improvement after CS
Ch. (m) Layer Stifness (MN/m2) before CS Layer Stifness (MN/m2) before CS Layer Stifness (MN/m2) after CS Layer Stifness (MN/m2) after CS Comment
Ch. (m) PQC EFM PQC EFM Comment
0 6900 330 17820 280 Joint
1 14580 370 5990 280  
2 21410 420 12640 310  
3 29020 420 10930 370  
4 32480 270 11860 320  
5 17500 280 13520 320  
6 4320 700 9460 380 Joint
7 19360 380 11540 330  
8 - 590 16230 330  
9 3720 530 9560 210 Transverse Crack
10 16460 350 12290 390  
11 59580 250 15030 360  
12 5410 350 12720 750 Joint
13 15250 380 11960 390  
14 28700 380 16110 310  
15 30400 380 15030 290  
16 50130 340 16290 420  
17 7820 330 16170 310  
18 3850 390 12110 340 Joint
19 23410 470 17400 350  
20 gt70000 490 24660 390  
21 3490 450 12760 350 Transverse Crack
22 8540 470 14120 380  
23 13460 330 25970 220  
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Assessment of Bond Between Pavement Layers
47
Bond between Pavement Layers

• Complicated phenomenon and its effect on pavement
  behaviour not very well understood
• Function of temperature and material type
• Can develop with time under traffic loading
• Full bond is commonly assumed in design

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Bond between Pavement Layers (Contd)

• In practice, difficult to achieve full bond as
  specified in SHW
• Deflection testing (FWD, Deflectograph?)
• show higher deflections under loading
• Layers are acting independently
• Lower effective stiffnesses
• Lower bearing capacity and hence life

49
Methods of Bond Assessment
Falling Weight Deflectometer
Coring Survey
De-bonded Cores
Hammer Test
Leutner Test
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SWPE Experience with Bond Analysis

• Over 10 Technical Papers 1994 2003
• Practical application on more than 10 projects
  (UK Overseas)
• EPSRC Research Project ( with Nott. University)
  1999-2002
• HA Research Project (SWPE) 2003-2004