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The Use of FWD for Pavement Monitoring: Case Studies

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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 The Use of FWD for Pavement Monitoring: Case Studies Bachar Hakim and Martyn Jones Scott Wilson Pavement Engineering

2 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 Performance Parameters 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

7 Design for Permanent Works - Long Term
FOUNDATION: Design for Permanent Works - Long Term Upper Pavement Sub-base Capping Subgrade Limit rutting in Upper Pavement Limit flexure of Upper Pavement Limit deformation of subgrade (Structural rutting) (Fatigue cracking)

8 Design for Construction - Short Term
FOUNDATION: Design for Construction - Short Term Capping Subgrade Adequate Stiffness Limit rutting in subgrade to Compact Upper Pavement

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10 Long Term Capping Thickness Design - A
600 500 400 300 200 100 1 10 2 3 4 5 6 7 8 9 Subgrade CBR (%) For thickness requirements less than 150mm see paragraph 5.20 For very soft subgrades see paragraph 5.19

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12 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) 80 (Chalk) 100 (Other crushed rock) 120 (Recycled crushed concrete) 6F3 Selected granular material 150 9A Cement stabilised well graded granular material 80* 9B Cement stabilised silty cohesive material 9C Cement stabilised conditioned pulverised fuel ash cohesive material 9D Lime stabilised cohesive material Type 1 Sub-base * The stiffness quoted is conservative. Depending on the soil type and level of stabilisation used much higher values can be obtained.

13 Correlation of German Dynamic Plate (GDP) with FWD:- Stiffness Testing

14 Prima Dynamic Plate:- Stiffness Testing

15 Dynamic Plate Tests: Stiffness Performance Requirements
Finished surface of capping shall:- >40MPa 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

16 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 < 250 40 > 250 < 500 50 > 500

17 Trafficking Trial: Rutting Tests

18 Trafficking Trial: Rutting Measurements

19 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

20 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

24 Rutting and DCP testing

25 Foundation Assessment of Existing Pavements

26 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

27 Concrete Slab Failure

28 Removal of PQC Slabs

29 Rolling the Unbound Materials

30 Performance Evaluation Using Dynamic Plate Tests (GDP & Prima)

31 Jersey Airport: Performance Specifications

32 Jersey Airport: ALPHA TAXIWAY PROJECT

33 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

34 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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36 Effective Stiffness (MPa)
FWD Test Results Section Layer Thickness (mm) PQC CBM 150 320 Section Statistics Effective Stiffness (MPa) PQC CBM Subgrade 50%ile 15%ile - 8400 4700 100 80 34300 30200 5400 3800 130 120 Joint Type Statistics Joint Parameters d3-d4 (mm) d4/d3 (%)* 1 (deg x 10-3)* 1-2 (deg x 10-3) Transverse Joints 50%ile 85 (or 15*) %ile 12 15 96 95 6.5 8.4 1.7 2.4 Longitudinal Joints 133 259 63 39 0.0 -5.0 5.9 10.3

37 FWD Slab Edge and Corner Test Results
Location Statistics Normalized FWD Deflections (mm x 10-3) d1 d2 d3 d4 d5 d6 d7 d1 - d3 d3 - d4 Slab Centres 50%ile 85%ile 318 364 290 340 265 314 254 302 202 242 153 185 101 124 48 56 12 13 Slab Edges 472 583 435 550 399 514 381 498 323 400 230 288 148 200 57 79 15 18 Slab Corners 422 527 379 487 349 451 334 432 273 353 194 129 190 83 17 Location Normalized FWD Deflections (mm x 10-3) d1 d2 d3 d4 d5 d6 d7 d1 - d3 d3 - d4 Slab Edges 49% 50% 60% 46% 19% 22% Slab Corners 33% 31% 32% 35% 26% 28% 16% 25%

38 COST SAVINGS COST SAVING A
305 COST SAVING HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS. A £158,000

39 COST SAVINGS A B COST SAVING A B
305 B 150 COST SAVING A HIGHER FLEXURAL STRENGTH CONCRETE DEVELOPED GIVING 10% REDUCTION IN THICKNESS. SECONDARY AGGREGATES FOR BOUND BASE 30% COST SAVING. £158,000 £295,000 B

40 COST SAVINGS A B C COST SAVING A B C
305 B 150 C 300 COST SAVING A 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 B C

41 COST SAVINGS A B C COST SAVING A B TOTAL £690,000 C
305 B 150 C 300 COST SAVING A 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 B C Materials development costs £30,000

42 FWD Testing on Cracked and Seated Concrete Pavement

43 Crack and Seat of Concrete Pavement

44 Joints improvement after C+S

45 Stiffness Improvement after C+S
Ch. (m) Layer Stifness (MN/m2) before C&S Layer Stifness (MN/m2) after C&S Comment PQC * EFM 6900 330 17820 280 Joint 1 14580 370 5990 2 21410 420 12640 310 3 29020 10930 4 32480 270 11860 320 5 17500 13520 6 4320 700 9460 380 7 19360 11540 8 - 590 16230 9 3720 530 9560 210 Transverse Crack 10 16460 350 12290 390 11 59580 250 15030 360 12 5410 12720 750 13 15250 11960 14 28700 16110 15 30400 290 16 50130 340 16290 17 7820 16170 18 3850 12110 19 23410 470 17400 20 >70000 490 24660 21 3490 450 12760 22 8540 14120 23 13460 25970 220

46 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

48 ‘Bond’ between Pavement Layers (Cont’d)
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

50 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) HA Research Project (SWPE)


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