Impact of Bitumen Wax on Asphalt Performance: Good or Bad?

1. Bitumen Wax & Impact on Asphalt Performance Good or bad? Per Redelius and Xiaohu Lu Nynas Bitumen NaBin Seminar October 26 2004 Nynas Bitumen R&D

2. Definition of wax in bitumen? • All materials in bitumen, which crystallise on cooling • Paraffin wax (or macrocrystalline wax): n-paraffins with few or no branches • Microcrystalline wax: aliphatic hydrocarbons with considerable amount of iso- and cycloparaffins • Aromatic molecules or molecules with polar functional groups showing ability to crystallise upon cooling Nynas Bitumen R&D

3. Definition of wax in bitumen Wax in bitumen could be: • Natural wax which is present in the crude oil (Bitumen produced from waxy crudes) • Wax unintentionally produced through refining procedures like visbreaking or hydrocracking • Synthetic wax added to bitumen to change certain properties. This presentation is limited to “natural wax”. Nynas Bitumen R&D

4. Impacts of Waxy Bitumen on asphalt performance? • Melting of wax at high temperatures (60oC) • - decrease in viscosity  more sensitive to rutting • Crystallisation of wax at low temperatures • - increase in stiffness, physical hardening  more sensitive to low temperature cracking • Poor adhesion to aggregates (stripping) • Wax crystals  reduced cohesion (effect on fatigue?) • … ... Nynas Bitumen R&D

5. Project Overview • Determination of wax content of bitumen (I) • Isolation and chemical characterisation of wax (II) • Wax morphology (III) • Rheological study (IV) • Impact of wax on asphalt performance (V) Nynas Bitumen R&D

6. Determination of Wax Content of Bitumen • Differential scanning calorimetry (DSC) • EN 12606-1 (DIN 52015) • Wax from IEC neutral fraction • Wax from SEC II Nynas Bitumen R&D

7. Differential scanning calorimetry (DSC) Nynas Bitumen R&D

8. Size Exclusion Chromatography (SEC) SEC-I: the most polar and associating components (“dispersed phases” or “asphaltenes”) SEC-II: non-associating components (“bitumen solvent moieties”) Precipitation of wax at -20°C from SEC-II (toluene/methyl ethyl ketone) Nynas Bitumen R&D Toluene

9. Comparison of Wax Contents Determined by Different Methods Nynas Bitumen R&D

10. 6 y = 0.23x + 0.61 4 2 R = 0.55 Paraffin by EN12606-1 (%) 2 0 0 2 4 6 8 Wax by DSC (%) Correlation between DSC and EN12606-1 Method Nynas Bitumen R&D

11. Test Methods Crystal. Temp. Test methods SEC EN higher lower • Paraffin wax (macrocrystalline wax) • Microcrystalline wax (iso- and cycloparaffins) • Waxes with aromatic or polar groups DSC Nynas Bitumen R&D

12. Chemical Characterisation of Wax Isolated from Bitumens • Differential scanning calorimetry (DSC) • Gas chromatography and mass spectrometry (GC-MS) • High temperature gas chromatography (HTGC) • Wide angle X-ray scattering (WAXD) • Gel permeation chromatography (GPC) • Thin layer chromatography with flame ionisation detection (TLC-FID) • Fourier transform infrared spectroscopy (FTIR) • Ultraviolet and visible spectroscopy (UV-Vis) Nynas Bitumen R&D

13. Differential Scanning Calorimetry (DSC) of wax isolated from bitumen through the SEC procedure- 38ºC & 63ºC, 101J/g 61ºC, 64J/g Nynas Bitumen R&D

14. n-C23 GC-MS: Wax from G40-96 Nynas Bitumen R&D

15. Isolated Waxes n-Paraffins WG36 C18-C54, 10% WG37 C21-C52, 40% WG38 C18-C53, 18% WG40 C18-C58, 47% WG67 C18-C54, 23% Nynas Bitumen R&D

16. Conclusions (I) • Wax (content) determination is method dependent; • Waxes differ in crystallisation/melting process, and in enthalpy; • Waxes differ in the content and distribution of n-paraffins; • Waxes also contain other materials, such as iso-paraffins, mono-, and di-naphthenes, and aromatics. Nynas Bitumen R&D

17. Wax Morphology • Development of methodology • Classification of wax crystals • Effects of time and temperature • Temperature cycling • Freezing and melting experiments Nynas Bitumen R&D

18. Techniques for Studying Wax Morphology • Polarised Light Microscopy (PLM) • Confocal Laser Scanning Microscopy (CLSM) • Freeze Fracture - Transmission Electron Microscopy (FF-TEM) Nynas Bitumen R&D

19. Polarised Light Microscopy (PLM) 1h heat at 120°C & homogenise Slides at room temp. for 1h • Wax crystals in bitumen are anisotropic, which appear bright in PLM • Using transmitted light, sample has to be thin enough to let light pass through (10 m) • Crystals have to be large enough to be detectable (1 m) Nynas Bitumen R&D

20. Confocal Laser Scanning Microscope (CLSM) Slides Metal cup • Scan the specimen with an illuminating spot (laser) • A small pinhole in front of detector • Controllable depth of field • Applicable to thin and thick specimen • Reflective light used to record images Nynas Bitumen R&D

21. PLM CLSM FF-TEM U1393-02 10 m 10 m 100 nm T8-00 10 m 10 m 100 nm Nynas Bitumen R&D

22. 2% wax G40-96 T63-02 T76-02 4% wax G36-96 G38-96 T9-00 Nynas Bitumen R&D

23. Elongated Spots: G40-96 Crescents: T63-02 Flakes: T9-00 T8-00 Nynas Bitumen R&D

24. Effect of Crystallisation Time and Temperature • Temperatures: -19°C, 0°C, 22°C, 40°C • Time: 1h, 4h, 24h • New sample for each temperature-time combination • Same temperatures for taking micro-photos and • for crystallisation Nynas Bitumen R&D

25. 0ºC 22ºC 40°C 1 h 24 h Nynas Bitumen R&D

26. After 1h crystallisation at 22°C, heat the sample to 60°C at 10°C/min 60°C after 15 min Heating to 80°C for 15 min 60°C after 30 min Nynas Bitumen R&D

27. Conclusions (II) • Waxy bitumens may differ in waxy morphology; • The size and shape of wax crystals are not related to wax content; • The time and temperature show great effects on wax morphology; • At low temperatures, the time for visible wax crystals is longer and the • crystals are smaller as compared with crystallisation at room temperature. • At high temperatures, few crystals with large size are detected. • With increasing time, the wax crystals become more distinct. • For the bitumens studied, the temperatures for complete melting of wax • crystals are found between 40 and 80°C. Nynas Bitumen R&D

28. Impact of Wax on Asphalt Performance • - Rutting • - Low temperature cracking • - Water sensitivity Nynas Bitumen R&D

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30. T8-00 Nynas Bitumen R&D

31. f = 0.05 Hz Nynas Bitumen R&D

32. Correlation between ZSV and SHRP rutting parameter Nynas Bitumen R&D

33. 3000 50/70 grade 2500 70/100 grade 160/220 grade 2000 1500 G*/sin(delta) at 60°C and 10 rad/s (Pa) 1000 500 0 0 2 4 6 8 Wax Content (%) Nynas Bitumen R&D

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36. Wax (%) 2.3 0 4.1 6.2 0 2.4 2.9 4.1 4.2 Pen 65 83 101 86 196 214 181 180 180 Nynas Bitumen R&D

37. Wax (%) 2.3 0 4.1 6.2 0 2.4 2.9 4.1 4.2 Pen 65 83 101 86 196 214 181 180 180 Nynas Bitumen R&D

38. Mixture rutting (after 1500 wheel passes) versus bitumen softening point Nynas Bitumen R&D

39. Mixture rutting (after 1500 wheel passes) versus bitumen dynamic viscosity Nynas Bitumen R&D

40. Mixture rutting (after 1500 wheel passes) versus bitumen G*/sin (delta) and ZSV Nynas Bitumen R&D

41. Low Temperature Properties • Binders • Glass transition temperature by DSC • Creep test by bending beam rheometer (BBR) • Isothermal physical hardening • Asphalt mixtures • Thermal stress restrained specimen test (TSRST) Nynas Bitumen R&D

42. Binder creep test with BBR Physical hardening Nynas Bitumen R&D

43. LST for 160/220 bitumens Nynas Bitumen R&D

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45. Thermal Stress Restrained Specimen Test (TSRST) Nynas Bitumen R&D

46. Mixture test (TSRST): fracture temperature vs wax content Nynas Bitumen R&D

47. Mixture test (TSRST): fracture strength vs wax content Nynas Bitumen R&D

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50. Comparison of Water Sensitivity of Asphalt Mixtures Wax in bitumen 2.3 0 4.1 6.2 0 2.4 2.9 4.1 4.2 (%, by DSC) Penetration 65 83 101 86 196 214 181 180 180 Nynas Bitumen R&D