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Interim Guidelines: The Design and Use of Foamed Bitumen Treated Bases Fenella Long Road Pavements Forum 13-14 November 2001

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  • Slide 1
  • Interim Guidelines: The Design and Use of Foamed Bitumen Treated Bases Fenella Long Road Pavements Forum 13-14 November 2001
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  • Outline u Objectives u Projects u Interim guideline document u Timelines and deliverables u Structural design procedure
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  • Objectives u Synthesise Available information Best practice Latest research results u Provide Interim Guidelines while further information and experience is gathered u Develop a structural design procedure for incorporation into the South African Mechanistic- Empirical Design Procedure u Similar work with bituminous emulsion treated bases
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  • Projects and Funding u Laboratory Testing: Gautrans, C&CI, SANRAL u HVS Testing:Gautrans u Interim Guideline document Phase 1: Gautrans Phase 2: SABITA, managed by the Asphalt Academy u Foamed Asphalt Working Group
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  • Interim Guideline Document Chapter 1. Introduction Chapter 2. Selection Criteria (Transportek) Chapters 3-5. Mix Design Considerations (Prof. Jenkins) Chapter 6. Structural Design (Transportek) Chapter 7. Construction Aspects (Transportek) Chapter 8. Conclusions Phase 1 Phase 2 Phase 1
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  • Timelines and Deliverables u Phase 1 Draft completed June 2001 Currently incorporating comments u Phase 2 October 2001 March 2002 u Seminars run by the Asphalt Academy May 2002
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  • Structural Design u Design philosophy u Mechanistic-empirical design procedure u Based on HVS and laboratory tests u Distress mechanisms, transfer functions
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  • Design Philosophy u Adequate support u Prevent overloading Materials very sensitive to overloading u Optimize design for distress mechanisms u Prevent moisture ingress
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  • HVS Tests u Road P243/1, between Vereeniging and Heidelberg u Deep In Situ Recycled Base 2% cement 1.8% foamed bitumen or bituminous emulsion u 2 HVS test sections per material u 3 Wheel loads
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  • Laboratory Tests u Unconfined compressive strength (UCS) u Indirect tensile strength (ITS) u CBR u Static triaxial u Dynamic triaxial u Flexural fatigue beam u Permeability u Erodibility
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  • Distress Mechanisms u Fatigue u Permanent deformation
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  • Fatigue Transfer Function u HVS Tests Reduction in stiffness
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  • Fatigue Transfer Function u HVS Tests Reduction in stiffness
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  • Fatigue Transfer Function u Effective fatigue life Repetitions to 400 MPa stiffness
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  • Fatigue Transfer Function u Laboratory test Four-point beam fatigue test Strain-at-break, b
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  • Fatigue Transfer Function u Pavement structure u Tensile strain at the bottom of the base, Foamed bitumen base bb Strain ratio = from laboratory test
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  • Fatigue Transfer Function u Effective fatigue as a function of strain ratio
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  • Fatigue Transfer Function u Effective fatigue as a function of strain ratio
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  • Permanent Deformation Transfer Function u HVS Data Permanent deformation of base layer from MDD data N F,PD = f (wheel load, plastic strain)
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  • Permanent Deformation Transfer Function u Laboratory tests Static and dynamic triaxial tests N F,PD =f (stress ratio, plastic strain, relative density, saturation, foamed bitumen and cement contents) Wider range of material conditions
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  • Permanent Deformation Transfer Function u Pavement structure u Stress ratio in the base layer, SR Foamed bitumen base 1 1 allowable Stress ratio = from laboratory test
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  • Permanent Deformation Transfer Function u Combine field and laboratory models u Work in progress Repetitions Stress Ratio Relative density Saturation Foamed bitumen content Cement content Plastic strain
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  • Damage Factors u Effect of overloading u Load equivalency u Fatigue n 5.6 u Permanent deformation n 2.4 N = P P 80kN n
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  • Limitations u One material, ferricrete u HVS tests 2.0% cement 1.8% foamed bitumen u Laboratory specimen preparation
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  • Conclusions u Interim Guidelines for Foamed Bitumen Treated Bases available March 2002 u Includes structural design procedure for SA Mechanistic-Empirical Design Procedure u Industry feedback to gather experience and refine guidelines