The Use of FWD for Pavement Monitoring: Case Studies

1. 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 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

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

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

10. 600 For very soft subgrades see paragraph 5.19 500 400 300 For thickness requirements less than 150mm see paragraph 5.20 200 100 0 1 2 3 4 5 6 7 8 9 10 Subgrade CBR (%) Long Term Capping Thickness Design - A

12. Typical Capping Material Properties * 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:-

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

36. FWD Test Results

37. FWD Slab Edge and Corner Test Results

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

39. A B B A 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. A B C B C A 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. A B C B C A 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

44. Joints improvement after C+S

45. Stiffness Improvement after C+S

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) 1999-2002 • HA Research Project (SWPE) 2003-2004