Bitumen / Filler Interactions

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Chemo-Mechanics of Bituminous Materials – Washington DC – Jan. 10th, 2010

Bitumen / Filler Interactions

  1. 1. Bitumen / filler interactions Current understanding and perspectives Didier Lesueur - [email_address] Chemo-Mechanics of Bituminous Materials – Washington DC – Jan. 10th, 2010
  2. 2. Content <ul><li>Some Properties of Mineral Fillers </li></ul><ul><li>Bitumen / Filler interactions: A mechanical approach </li></ul><ul><li>Bitumen / Filler interactions: A physico-chemical approach </li></ul><ul><li>Research Needs </li></ul>
  3. 3. Content <ul><li>Some Properties of Mineral Fillers </li></ul><ul><li>Bitumen / Filler interactions: A mechanical approach </li></ul><ul><li>Bitumen / Filler interactions: A physico-chemical approach </li></ul><ul><li>Research Needs </li></ul>
  4. 4. Definitions <ul><li>Mineral Filler </li></ul><ul><ul><li>Defined in EN 13043: Aggregates for bituminous mixtures </li></ul></ul><ul><ul><li>Particle size <63  m </li></ul></ul><ul><li>Relevant properties </li></ul><ul><ul><li>Density </li></ul></ul><ul><ul><li>Particle </li></ul></ul><ul><ul><li>Dry Porosity </li></ul></ul>
  5. 5. Particle sizes of typical mineral fillers W: Limestone D: Dolomite M: Melaphyre B: Basalt CAL: Hydrated Lime from Grabowski et al., Proc. Mairepav6, 2009 CAL M D B W
  6. 6. Dry compacted porosity of mineral fillers (Rigden air voids - EN 1097-4) L: Limestone D: Dolomite M: Melaphyre B: Basalt CAL: Hydrated Lime from Grabowski et al., Proc. Mairepav6, 2009
  7. 7. Content <ul><li>Some Properties of Mineral Fillers </li></ul><ul><li>Bitumen / Filler interactions: A mechanical approach </li></ul><ul><li>Bitumen / Filler interactions: A physico-chemical approach </li></ul><ul><li>Research Needs </li></ul>
  8. 8. Stiffening effect measured by delta Ring&Ball (EN 13179-1) L: Limestone D: Dolomite M: Melaphyre B: Basalt CAL: Hydrated Lime from Grabowski et al., Proc. Mairepav6, 2009 CAL: too stiff to measure!!
  9. 9. Stiffening effect correlated with Rigden air voids from Vansteenkiste + Vanelstraete, AAPT, 2008 L D M B
  10. 10. The stiffening effect of mineral filler: A volume fraction effect <ul><li>Recognized in asphalt science by Rigden (J. Soc. Chem. Ind. 66, 1947) </li></ul><ul><li>Known in colloid science for decades </li></ul><ul><ul><li>Einstein (Ann. Physik 19, 1906 - Ann. Physik 24, 1911) </li></ul></ul><ul><ul><li>... </li></ul></ul><ul><ul><li>Metzner (J. Rheol. 29, 1985) </li></ul></ul><ul><ul><li>... </li></ul></ul><ul><ul><li>Coussot, Rheometry of paste, suspensions and granular materials, 2005 </li></ul></ul><ul><ul><li>Ovarlez (J. Rheol. 50, 2006) </li></ul></ul><ul><ul><li>... </li></ul></ul>
  11. 11. The stiffening effect of mineral filler: The Einstein equation <ul><li>Hypothesis behind Einstein’s calculations </li></ul><ul><ul><li>Spherical particles </li></ul></ul><ul><ul><li>Not deformable (= hard spheres) </li></ul></ul><ul><ul><li>Newtonian liquid </li></ul></ul><ul><ul><li>No hydrodynamic interactions (large particle – particle distance) </li></ul></ul><ul><li>Applicability to bituminous mastics </li></ul><ul><ul><li>Not exactly spherical </li></ul></ul><ul><ul><li>Rocks = 20-100GPa vs bitumen <3 GPa </li></ul></ul><ul><ul><li>Viscoelastic (but not a problem - Palierne, Rheol. Acta 30, 1990 ) </li></ul></ul><ul><ul><li>Low concentrations (below 5-10vol.%) </li></ul></ul>
  12. 12. The stiffening effect of mineral filler <ul><li>Low volume fraction (Einstein):  =  0 (1 + [  ]  </li></ul><ul><ul><li> : mastic viscosity </li></ul></ul><ul><ul><li> 0 : suspending liquid viscosity </li></ul></ul><ul><ul><li>[  ]: intrinsic viscosity of the particles = 2.5 for hard spheres </li></ul></ul><ul><ul><li> : volume fraction of particles </li></ul></ul><ul><li>High volume fraction (Maron-Pierce, J. Colloid Sci. 11 1956): </li></ul><ul><ul><li> =  0 ( 1 -  m   </li></ul></ul><ul><ul><li>[  ] = 2/  m </li></ul></ul>
  13. 13. The stiffening effect of mineral filler from Quemada, Rheol. Acta 16, 1977 linear (Einstein) maximum packing
  14. 14. The stiffening effect of mineral filler from Heukelom + Wijga, AAPT, 1971 <ul><li>Maron-Pierce equation shown to apply to bituminous mastics (Heukelom + Wijga, AAPT, 1971): </li></ul><ul><ul><li>limestone </li></ul></ul><ul><ul><li>slate dust </li></ul></ul><ul><ul><li>kaolin </li></ul></ul>
  15. 15. The stiffening effect of various fillers from Lesueur, Adv. Colloid Interface Sci. 145, 2009 [  ] above the usual 2.5-5 value
  16. 16. Content <ul><li>Some Properties of Mineral Fillers </li></ul><ul><li>Bitumen / Filler interactions: A mechanical approach </li></ul><ul><li>Bitumen / Filler interactions: A physico-chemical approach </li></ul><ul><li>Research Needs </li></ul>
  17. 17. Why do fillers have these intrinsic viscosities? Table data from Landau + Lifschitz, Fluid Mechanics, 1958 <ul><li>Fibers </li></ul><ul><ul><li>[  ] = 16.5-35 </li></ul></ul><ul><ul><li>elongated </li></ul></ul><ul><li>Mineral filler </li></ul><ul><ul><li>[  ] = 2.5-5.0 </li></ul></ul><ul><ul><li>not exactly spherical </li></ul></ul><ul><li>Kaolin </li></ul><ul><ul><li>[  ] = 6.7 </li></ul></ul><ul><ul><li>platelets </li></ul></ul>a b
  18. 18. Why do hydrated lime stiffen more than mineral fillers? <ul><li>Hydrated lime </li></ul><ul><ul><li>[  ] ~ 7-10 ( T > 15°C ) </li></ul></ul><ul><ul><li>[  ] ~ 2.5-5 ( T < 15°C ) </li></ul></ul><ul><ul><li>Shape similar to that of mineral fillers </li></ul></ul><ul><ul><li>HL particle shape can’t explain the stiffening </li></ul></ul>
  19. 19. <ul><li>HL has high dry porosity as measured by high Rigden air voids (and fly ash also) </li></ul><ul><li>But only explains part of the stiffening: </li></ul><ul><ul><li>expected  m ~35% when observed is  m ~20% (Lesueur + Little, TRR 1661, 1999) </li></ul></ul>Why do hydrated lime behave differently than usual mineral fillers? mineral filler hydrated lime 35% air voids 65% air voids
  20. 20. What is the effect of particle size? <ul><li>Einstein </li></ul><ul><ul><li>Particle size not relevant </li></ul></ul><ul><li>Colloid science (1) </li></ul><ul><ul><li>Particle size relevant if Brownian – non-Brownian transition (Krieger, Adv. Colloid Interface Sci. 3, 1972) </li></ul></ul><ul><ul><li>Brownian particles occupy a higher apparent volume fraction </li></ul></ul><ul><ul><li>For a 50/70 bitumen at 100°C (5kPa.s), it takes a particle diameter of order 10nm to observe such a transition (Stokes-Einstein law) </li></ul></ul><ul><ul><li>Not relevant for common mineral fillers </li></ul></ul>
  21. 21. What is the effect of particle size? <ul><li>Colloid science (2) </li></ul><ul><ul><li>Possible adsorption of asphaltenes micelles </li></ul></ul><ul><ul><li>Subsequent increase in particle apparent volume fraction </li></ul></ul><ul><ul><ul><li>Mineral filler particle radius 1  m: </li></ul></ul></ul><ul><ul><ul><ul><li>Layer of thickness 200nm </li></ul></ul></ul></ul><ul><ul><ul><ul><li> m decreases from 35% to 20% </li></ul></ul></ul></ul><ul><ul><ul><li>Mineral filler particle size ~10  m: </li></ul></ul></ul><ul><ul><ul><ul><li>Layer of thickness 2,000nm </li></ul></ul></ul></ul><ul><ul><ul><ul><li> m decreases from 35% to 20% </li></ul></ul></ul></ul><ul><ul><ul><li>Note: Asphaltenes micelle radius ~2-8nm (Lesueur, ACIS 145, 2009) </li></ul></ul></ul><ul><ul><ul><li>Possible effect for micron size particles </li></ul></ul></ul>
  22. 22. Content <ul><li>Relevant Properties of Mineral Fillers </li></ul><ul><li>Bitumen / Filler interactions: A mechanical approach </li></ul><ul><li>Bitumen / Filler interactions: A physico-chemical approach </li></ul><ul><li>Research Needs </li></ul>
  23. 23. Conclusions and perspectives: Summary <ul><li>The stiffening of bitumen by mineral fillers is explained by suspension rheology </li></ul><ul><ul><li>Filler volume fraction key parameter </li></ul></ul><ul><ul><li>Particle shape explains the higher stiffening observed for some classes of fillers (kaolin, fibers) </li></ul></ul><ul><li>The higher stiffening of hydrated lime </li></ul><ul><ul><li>Mostly explained by higher packing fraction (~ Rigden air voids) </li></ul></ul><ul><ul><li>... But other mechanisms are needed to explain the full extent of stiffening </li></ul></ul><ul><ul><ul><li>Asphaltenes adsorption layer? </li></ul></ul></ul>
  24. 24. Conclusions and perspectives: Research needs <ul><li>In-situ validation of the adsorption layer </li></ul><ul><li>Maximum packing + adsorption layer enough to explain the behaviour of all fillers? </li></ul><ul><ul><li>~200nm silica fume stiffening? (Delaporte, E&E, 2008) </li></ul></ul><ul><li>Effect of temperature </li></ul><ul><ul><li>HL “normal” mineral filler at low temperature but a high stiffening one at high temperature (Little + Petersen, J. Materials Civ. Eng. 17, 2005) </li></ul></ul><ul><ul><ul><li>Mechanical contrast between matrix and particle? (i.e. hard sphere hypothesis) </li></ul></ul></ul><ul><ul><li>Continuous evolution of stiffening ratio observed with fillers (Delaporte, E&E, 2008) </li></ul></ul><ul><ul><ul><li>Volume fraction evolution due to mismatch of dilation coefficients? </li></ul></ul></ul>
  25. 25. Thank you for your attention

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