Premium Asphalt Bases - the role of the binder. AAPA Masterclass November 2012

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1 Premium Asphalt Bases - the role of the binder AAPA Masterclass November 2012 Copyright of Royal Dutch Shell plc Date 06/12/2012 1

2 Pavement Engineering Classical theory of stress generation and failure criteria in flexible pavements Applied loading Asphalt strain criterion Subgrade strain criterion ɛr ɛv Wearing course Intermediate course / roadbase Sub-base Subgrade Copyright of Royal Dutch Shell plc The theory dates back to the AASHO Road Test and the Alconbury Hill experiment

3 Pavement Engineering Load spreading effect of different pavement layers is related to the stiffness of the pavement materials w/c roadbase sub-base ɛv subgrade Copyright of Royal Dutch Shell plc Date 06/12/2012 Enter document title in Footer (Insert > Header & Footer > Apply to All) 3

4 Beam theory A simplified model assumes the road structure acts as a beam and will be subjected to the same engineering principles An applied force F to the beam will cause a deflection d to result. The resulting deflection will be influenced by the magnitude of the applied force, the length of the beam (L) and the modulus of the beam E. Beam Modulus E d Copyright of Royal Dutch Shell plc Date 06/12/2012 Enter document title in Footer (Insert > Header & Footer > Apply to All) 4

5 Modulus and Stiffness The stress / strain relationship of engineering materials is a fundamental property. For elastic materials Hookes Law is valid where: E= σ/ɛ where the elastic modulus E is the quotient of the stress σ divided by the tensile strain ɛ For visco-elastic materials such as bitumen where the strain is dependent on the time of loading and the temperature, the modulus is called stiffness and loading times and temperature must be referenced: S t,t = σ/ɛ T Bitumen stiffness strongly influences asphalt stiffness, hence using harder grades of binder will create stiffer asphalt with improved load spreading qualities. Copyright of Royal Dutch Shell plc Date 06/12/2012 Enter document title in Footer (Insert > Header & Footer > Apply to All) 5

6 History - Evolution of Base course mixes in France GB EME 2 EME / Very hot summer /70 or 35/50 10/ /50 20/ /50 or 20/30 10/20 or 20/30 or 25/35

7 EN 13924:2006 Specification for hard paving grade bitumens Essential Requirement Surrogate Characteristic Test Methods Unit Classes Consistency at Intermediate Service Temparature Penetration at 25 C EN mm NPD TBR 15 to to 20 Consistency at Elevated Service Temperature Durabilty (Resistance to hardening at 163 EN ) Other Properties Softening Point EN 1427 Dynamic Viscosity at 60 C WN Change of Mass EN or 3 Retained Penetration EN 1426 Softening Point after hardening Increase in Softening Point Increase in Softening Point & Penetration Index before test (on original bitumen Kinematic Viscosity at 135 C EN1427 EN 1427 EN 1427 EN C NPD TBR 55 to to to 76 Pa.s NR TBR % NPD TBR 0.5 % NPD TBR 55 Orig. Min+2 C NPD TBR C NPD TBR 8 10 C NR TBR 10 from -1.5 to NR TBR Fraass Breaking Point EN C NR TBR 0 3 Flash Point EN ISO 2592 C /12/2012 % mass Solubility EN fraction NR TBR 99 7

8 EN 13924:2006 Annex B (Informative) Table B.1 Informative properties Property Unit Test Method Data T S=300Mpa, by BBR C EN TBR T m=0.3, by BBR C EN TBR G* at 15 C and 10 Hz, by DSR Mpa T G*/sind = 1 kpa at 1.6Hz, by DSR C EN EN TBR TBR 06/12/2012 8

9 EN Paving Grade Bitumens 06/12/2012 9

10 EN Paving Grade Bitumens 06/12/

11 Base course mixes - Main properties According to NF EN EB 14 Assise 35/50 (GB) and EB 14 Assise 10/20 (EME) Type of mix Giratory. (Voids %) C80 (D 10mm) C100 (D 14mm) C120 (D 20 mm) Water sensitivity r/r ratio Rut depth (60 C-100 mm) * cycles (%) ** cycles (%) Stiffness modulus (15 C-10Hz) in MPa Fatigue admissible strain (@ 1 million de cycles) G.B Class 2 GB Class 3 GB Class 4 EME Class 1 EME class * 9, * 9, ** 11, ** 14, ** 14,

12 Base course Asphalt Mixes According to NF EN EB 14 Assise 35/50 (GB) and EB 14 Assise 10/20 (EME) Type Max Aggr size Binder Binder Content (%) Void content % Thickness (cm) GB 14 et 20 35/50 20/30 4 to 5 6 to 8 8 to 16 EME / to to 6 6 to 15

13 Do we need thicker pavements to reach a longer life? Or is there a minimum strength above which structural damage by traffic doesn t occur 06/12/

14 UK Long Life Pavement Design TRL /12/

15 Do we have Hard Paving Grade Bitumens in Australia? Pinkenba Bitumen Plant 06/12/

16 Availability of Hard Grades in Australia Following a de-bottlenecking program and productivity improvements at the Pinkenba plant in Brisbane 15/25 bitumen is now being manufactured. It is expected to become available in NSW at the end of 2013 At present EME binders are not being considered for inclusion in AS2008 so they will be speciality bitumens based on EN Shell has made a 20 pen bitumen that complies with the EN /25 grade. 06/12/

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