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Bitumen / Filler Interactions
 

Bitumen / Filler Interactions

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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