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Use of Public Roads New perspectives in mixture designing Role of the state in Technological Developments

Use of Public Roads New perspectives in mixture designing Role of the state in Technological Developments. Chantal de La ROCHE LCPC - France Head of Road and binders materials section. Performance-based Road Construction Technology Terms of Reference, Contract, Conditions

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Use of Public Roads New perspectives in mixture designing Role of the state in Technological Developments

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  1. Use of Public Roads New perspectives in mixture designingRole of the state in Technological Developments Chantal de La ROCHE LCPC - France Head of Road and binders materials section Performance-based Road Construction Technology Terms of Reference, Contract, Conditions Conference of Hungarian Road Society - 16-17 Nov 2005

  2. Outlines • French road networks : some figures • An example of performance based mix design methodology • Trends in bituminous mixture evolution • Role of the state in technological development • Conclusion and future prospects.

  3. Overview of the French Road Natwork Superficies 550 000 km² Population : 63 Millions 1 million kms of roads Notional Roads 20 000 km Toll Motorways 8 000 km Free motorways 3 000 km Routes de liaisons 8 800 km Departments 380 000 km Cities 600 000 km

  4. French Roads : some figures Transfer to local authorities 1/1/2006 : RN 12 000 kms Average traffic: 20 à 60 000 v/j Temperate climate  θ surface -15°C, + 60°C, average 15°C

  5. French Roads : some figures Remark: legal axle load 130 kN

  6. An example of performance based methodologyFrench Bituminous Mix Design Methodology

  7. Principle One material type for each needOptimized with performance based criteriaIn relation with its use on the road

  8. Mix design and Composition • Standard Performances Lab study • Gradation & Binder content designer’s choice 100 Formulation tool: Gyratory Compactor (PCG) 90 ECF 80 BBSG 70 60 BBM Paasing [%] 50 BBTM 40 BBUM 30 BBDr 20 10 Sieve [mm] 0 0.1 1 10 Typical grading curves

  9. Mix design Formulation method • Components selection(aggregates, filler, binder, additives) • Check of their properties • performance class • Minimum binder content defined by standard • K Richness modulus (linked to the binder film thickness) • Level of mix design study • defined in contract • Check of the performance versus the selected class of the product standard

  10. Performances tested One test per property • Gyratory compactor (PCG) • workability and compactability assessment • Immersion compression (Duriez) test • Water sensitivity • Wheel tracking test • Rutting resistance • Direct tensile or 2 point bending test • Stiffness • 2 points bending test • Fatigue resistance

  11. Design steps Selection and identification of components Choice: gradation & binder content Compactability test (gyratory) Compaction Water sensitivity Level 1 Duriez test Rutting test Level 2 Rutting Level 3 Stiffness Modulus test Fatigue test Level 4 Fatigue Formulation selected

  12. Marshall test Level 1 and 2 tests • Components selection(aggregates, filler, binder, additives) • Check of their properties • performance class • Manufacturing and control of samples • Gyratory compaction test • Water sensitivity • Wheel tracking rutting test • Marshall

  13. Preparation of samples in laboratory Good control quality of mix: composition, voids,.. Homogeneity Accurate and Relevant Tests Relevant comparison with in situ materials

  14. Plate compactor: 400*600*150 or 180*500*25 à 100 Manufactoring % voids EN 12697-33 ex NFP 98-250-2 Mixer BBMAX 80 Vertical gamma Bench EN 12697-35 ex NFP 98-250-1) (EN 12697-7 ex NFP 98-250-5)

  15. Gyratory compactor Standard (NF 12697-31 ex NFP 98-252) Characterisation of void % reduction under axial force + gyratory shear Mix design by adjustment of void content according to product standards Estimation of site void content Vsite = V(Ne) Ne nbr of cycle as thickness [mm] r = 0,95 R = 1,38 (% voids 60 g) Compactability characterisation MLPC Gyratory shear compactor

  16. Typical result Void content (%) Repetability 0,95 Reproducibility 1,34

  17. Interpretationof gyratory compaction test • Conformity study of a mix in relation to product standard specification for each material type ( NFP 98-130 to 141) Void content Pass Failed Failed

  18. Void content versus layer thicknessIn site compaction process % voids 12 cm 5 8 6 10 4 20 16 26 2 8 Number of passes

  19. 14 12 Voids % 10 8 6 On spec 4 Out of spec 2 0 GB 2 GB 3 BBAC BBAC BBME EME 1 EME 2 (binder) BBAGG Gyratory compactor test: specifications

  20. Water sensitivity : Duriez test • Standard NFP 98-251-1 • Two compaction efforts: • D< 14 mm H 190 mm, 60 kN, 5 min • D>14 mm H 270 mm, 180 kN, 5 min • Stored at 18 °C, 7 days • in air (50 % moisture) • in water • Vertical compression (1 mm/s ) • Ratio r/R (and % voids) • Repeatability and reproducibility • r = 0,08 • R =0,13 (ratio of 0,73) Decision to use of an adhesion agent  European standard indirect tensile test (EN 12697-12)

  21. Level 2 : rutting resistance test

  22. LPC Wheel tracking test

  23. Rut depth measurement Wheel LPC Wheel tracking test • Standard (EN 12697-22 ex NFP 98-253-1 • Influence of heavy, slow, channelled traffic under high temperature • relevant correlation with site, repeatability (r = 1,2 et R =1,3) • Test conditions: • Smooth tire, pressure 0.6 MPa • Load 5 kN, speed 1 cycle/s • Controlled temperature 60°C

  24. Typical results with the LCPC wheel tracking Rutting Average Regression Number of cycles

  25. Influence of binder content

  26. Influence of binder type

  27. Influence of sand nature

  28. Influence of aggregates shape

  29. Influence of void content

  30. Rutting resistance -specifications • Test @ 60 °C Base Surface 20 Out of spec 16 12 Rut depth [%] 8 On spec 4 0 BBA BBA BBA BBME BBME BBME GB 2 EME 1 2 3 1 2 3 to 4 1-2 Number of cycles 10 000 30 000 10 000 30 000

  31. Level 3 and 4 Mechanical tests: stiffness measurement (direct tensile test or 2 points bending on trapezoidal samples) Fatigue resistance test

  32. Traffic direction e, s Bituminous Layers Thickness t Stiffness E Wearing course Base (tension) e, s Sub-base Non treated Natural soil Determination of bituminous mixes mechanical characteristics for pavement structural design Need for stiffness characteristics and fatigue resistance : admissible strain for 1 million cycles

  33. Direct tensile test • EN 12697-26 ex NFP 98 260-1 • Direct tension on cylindrical specimen • Master curve (rheological behavior) • Modulus for pavement design (specification) 15°C, 0,02s

  34. Complex modulus test • EN 12697-26 ex NFP 98 260-2 • 2 points bending on trapezoidal samples,4 repetitions • E pavement design15°C, 10 Hz • Master curve (rheological behavior) r = 335 MPa , R = 2750 MPa (E = 15300 MPa)

  35. Stiffness • Modulus @ 15°C: complex (10 Hz) or tensile (0,02 s) 20000 18000 16000 On spec 14000 12000 Modulus [MPa] 10000 8000 6000 4000 Out of spec 2000 0 BBA BBA BBME BBME GB 2- GB 4 EME 1-2 3 1 2-3 3 1-2

  36. Fatigue test • Standard EN 12697-24 ex NF P 98-261-1 • 2 points Bending beam on trapezoidal samples • B=56, b=25, t=2, h=250 mm • 3 strain levels with 6 specimens each, 10°C and 25 Hz • Strain calculated for 1 million of cycles 6 • (better behavior for high 6) • r = 4,2 µstrain R= 8,3 µstrain 6

  37. Fatigue test • Admissible strain @ 10 °C and 25 Hz [µstrain] 150 140 130 On spec e6[µstrain] 120 110 100 90 Out of spec 80 70 BBA 1 BBA 2 BBA 3 BBME BBME GB 2 GB 3 GB 4 EME EME 1 2-3 1 2

  38. Summary of the French mix design methodology Level 4 Fatigue Level 3 Stiffness Level 2 Permanent deformation level1 Giratory, water sensitivity

  39. Trends in bituminous mixtures evolutionsDissociation of layer functions : base = structure wearing course = surface caracteristics.

  40. Base materials evolution • Higher and higher binder contents • Smaller aggregate maximum size : • 31  20  14  10 mm • Increase of bitumen hardness: • 50  35  20  10 pen • Additives to increase hardness • Performances improvement • GB 3 then GB 4 • EME 2 • Reduction of thicknesses

  41. Base and foundation materials evolution

  42. Base Hot Mix Asphalt : main performances

  43. surface materials evolution • Thinner and thinner layers  1 to 2cm • Gap graded curves  Increase of porosity  Need for water proofing tack coat • More and more use of modified and special binders • Standardized products  performance characteristics

  44. Role of the state in Technological Developments

  45. Existing tools • Common researches between French administration and road contractors •  development of products, methodologies, laboratory devices, techniques, technical guides • Standardization French since 1992  10 product standards European with typical French products such as BBTM taken into account • Innovation policy of the French administration example : innovation protocol (charte de l’innovation)

  46. Innovation policy • For more than 25 years • Strong input of French administration: • Innovative Techniques Concourse • Technical advices (avis techniques) • Innovation protocol (charte de l’innovation)

  47. Innovation policy - examples Innovation protocols (chartes de l’innovation) French Road administration/road contractors French Road administration/toll motorway companies Technical conventions SETRA / Departments

  48. Innovation protocol : mean features • Focus on some priority subjects • Partnership • Sharing of observation data • Financial risk acceptation : French Road administration pays for over cost and possible repairs • Common conclusion • Leading committee • Technical validation : Certificate

  49. Innovation protocol : Organisation SUBJECTS PROPOSALS SELECTION AGREMENT PROTOCOL EXPERIMENTATIONS SURVEYS CONCLUSIONS - DECISION CERTIFICATE

  50. Some studied subjects among the various innovation protocols • Preventing permanent deformation • Preventing reflective cracking • Bituminous mixtures recycling • Improvement of surface characteristics • Recycling porous asphalts • Cleanliness of tack coats …..

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