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

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

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Bitumen / Filler Interactions Bitumen / Filler Interactions Presentation Transcript

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