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PHILIP JOUBERT STEWART SCOTT

ASPHALT REINFORCEMENT. DESIGN GUIDELINES FOR. SOUTHERN AFRICA?. PHILIP JOUBERT STEWART SCOTT. BACKGROUND. Based on SAT Seminar (Pretoria) Presentations by: Products: Cobus Venter – Geotrac Garth James – Kaytech Nicholas Reck – African Gabions Application:

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PHILIP JOUBERT STEWART SCOTT

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  1. ASPHALT REINFORCEMENT DESIGN GUIDELINES FOR SOUTHERN AFRICA? PHILIP JOUBERT STEWART SCOTT

  2. BACKGROUND • Based on SAT Seminar (Pretoria) • Presentations by: • Products: • Cobus Venter – Geotrac • Garth James – Kaytech • Nicholas Reck – African Gabions • Application: • Mynhardt Augustyn – VKE • Philip Joubert – Stewart Scott • Analytical Techniques: • Dr Fritz Jooste – Modelling & Analysis Systems • Innovation Planning: • Joop van Wamelen – Agrément SA

  3. WHY GUIDELINES? • Products and Purpose • Applications • Theory (Modeling) • The Road Forward

  4. WHY REINFORCE ASPHALT? • Normally during rehabilitation action • Grids/fabrics laid between old (distressed) and new asphalt overlay • To Provide Increased Resistance to: • Reflective Cracking • Fatigue Cracking (strengthen pavement) • Deformation (Rutting) • Moisture/Fines Movement

  5. PRODUCTS • Paving Fabrics: Geotextiles (Sealmac) • Glass Fibre Grids: Glassgrid / Glasstex • Polymer Grids: Polypropolene (AR - Grid) • Steel Grids: Wiremesh (Road Mesh) • Composites: Grid plus Fabric

  6. PAVING FABRIC

  7. GLASS FIBRE GRID

  8. STEEL GRID

  9. COMPOSITE : GRID / FABRIC

  10. PURPOSE

  11. WHY GUIDELINES? • Products and Purpose • Applications • Theory (Modeling) • The Road Forward

  12. RIGHT APPLICATION

  13. TYPICAL APPLICATIONS

  14. GLASS GRID FULL WIDTH

  15. GLASS GRID FULL WIDTH

  16. GLASS GRID FULL WIDTH Percent Crack Reflection by length

  17. GLASS GRID STRIPS

  18. USE OF INTERLAYERS

  19. GRID AND FABRIC INTERLAYER

  20. GRID AND FABRIC INTERLAYER

  21. GRID AND FABRIC INTERLAYER

  22. GRID AND FABRIC INTERLAYER

  23. CONCRETE SLABS OVERLAY

  24. CONCRETE SLABS OVERLAY

  25. CONCRETE SLABS OVERLAY

  26. GLASSGRID - SETTLEMENT CRACKS

  27. GLASSGRID - SETTLEMENT CRACKS

  28. PAVING FABRIC

  29. PAVING FABRIC

  30. POTENTIAL PROBLEMS

  31. POTENTIAL PROBLEMS

  32. POTENTIAL PROBLEMS

  33. WHY GUIDELINES? • Products and Purpose • Applications • Theory (Modeling) • The Road Forward

  34. WHY MODEL? • To investigate effects of • changing pavement parameters on pavement response • Given Effect X, • what is Strain-Y in Asphalt? • How will asphalt perform at Strain-Y?

  35. MICRO EFFECTS: UNCRACKED

  36. MICRO EFFECTS: UNCRACKED • Thickness and anisotropic effects distort calculated strains • Strain unlikely to be reduced by Reinforcement • UNLESS • Reinforcement considerably stiffer than Asphalt, and • there is zero slip

  37. Micro Effects: Cracked-Behaviour

  38. WAY AHEAD? • Expert Panel / National Interest Group, • develop code of practice for Southern Africa, • follow approach Euro committee/ TRB Group, • formalise sound network management approach • Product Performance Guarantee? • Vast potential matrix of operating conditions, • Difficult to follow this line of approach • Agrément Certification? • Standard conformance testing • Rutting, Beam Tests, Fatigue Testing (MMLS) • product approval / application type, within boundary conditions

  39. MICRO EFFECTS: CRACKED • Some modelling is possible using FE • Layered Elastic modelling not feasible • Benefits of reinforcement are more obvious for cracked scenario BUT Anisotropic effects still important and likely to underestimate benefits of reinforcement

  40. MODELLING POSSIBILITIES: SUMMARY • Routine modelling is likely to underestimate benefits of reinforcement • Routine modelling does not appear feasible at this stage Key Problem: Impact on damage inhibiting and crack retardation not evaluated at all

  41. WHY GUIDELINES? • Products and Purpose • Case Studies • Theory (Modeling) • The Road Forward

  42. WAY AHEAD • Build Confidence: Focus on field performance and validation (80 %) • Advanced modelling used mainly to identify key variables (5%) • Improve routine models to be able to accommodate transfer functions (15%)

  43. PRODUCT X: OVERLAYS > 50 MM Case Studies BLI Y-Max < 300 < 95 A,B,C 300 - 600 95 - 130 D,E F,G,H > 600 > 130

  44. CASE STUDY INFORMATION • Crack Type, Degree and Extent • Maximum Deflection, Base Layer Index, Test Details • Support Type and Thickness • Traffic Volumes, Daily E80s • Overlay and Construction Details

  45. PRODUCT X: OVERLAYS > 50 MM Not Yet Cracked Already Cracked MESA Base Layer Index

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