1070-4272/04/7703-0515C2004 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 77, No. 3, 2004, pp. 515!516. Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 3,
2004, pp. 521!522.
Original Russian Text Copyright + 2004 by Levchenko, Rozental’, Zalishchevskii.
Asphaltic Dispersion and Its Evolution in Manufacturing
E. S. Levchenko, D. A. Rozental’, and G. D. Zalishchevskii
St. Petersburg State Technological Institute, St. Petersburg, Russia
Received June 25, 2003
Abstract-Evolution of properties of cold asphalt is investigated. The time required for establishment of
adsorption equilibrium in preparation of asphaltic concrete is determined.
The asphaltic dispersion differs from the classical
colloidal systems in that its dispersed phase is formed
from molecules similar to those of the dispersion
medium. The molecules with a polynuclear condensed
structure consisting of 334 aromatic and 233 naph-
thene rings represent planes with alkyl substituents
bound around. Four to six molecules are arranged in
parallel to each other to form a quasispherical stack
Thanks to p-electron systems of the aromatic and
heteroaromatic rings, the intermolecular bonds in the
associate appear to be rather strong, and their dissocia-
tion starts only above 300oC. It was demonstrated by
X-ray diffraction that, in supramolecular structures of
this kind, the stack thickness is well comparable with
the diameter of the molecules (~0.831.7 nm), that
including the solvate shell being about 2.032.3 nm
[1, 2]. These structures are known as asphaltenes,
even though it is not absolutely correct.
In practice, by asphaltenes is meant a mixture of
compounds precipitated from a toluene solution of
asphalt under the action of n-pentane or n-hexane.
Along with high-molecular-weight aromatic mole-
cules, this mixture can contain low-molecular-weight
polar molecules insoluble in the indicated solvents.
Therefore, asphaltenes thus isolated can differ sig-
nificantly from those forming the dispersed phase of
asphalt. Furthermore, asphalt contains a great amount
of molecules also tending to association, but with a
lower energy of intermolecular interaction. In all
cases, association proceeds by random diffusion of
molecules in the asphalt bulk, until molecules of
the appropriate structure come into collision. This
requires a time increasing with decreasing tempera-
ture, because of increasing viscosity of the system and
decreasing energy of the molecules.
Therefore, it takes a long time to form a thermo-
dynamically stable asphalt structure. The lower the
temperature of asphalt, the longer this time. This may
be clearly demonstrated by measuring the penetration
of asphalt without intermediate softening in eight days
under oxygen-free conditions in the dark. The results
of such experiments are given in the table.
As seen, the penetration of asphalt decreased with
time, which is due to solely structural transformations.
Such an aging effect was attributed to oxidation in
the course of storage. However, in fact, it is a result
of high-temperature oxidation of asphalt. Structural
transformations accompanying establishment of ther-
modynamically stable state are very typical of oxi-
dized asphalts. In the course of asphalt oxidation,
naphtheno3aromatic oils undergo oxidative dehydro-
genation to form asphaltenes. At 2203280oC, this is
a kinetically controlled process, while association is
controlled by diffusion, proceeding at a considerably
Another consequence of aging, but of asphaltic
concrete pavements, which has not been taken into
consideration until now, is structural transformation of
Variation in the penetration of asphalt in aging at room
,* 0.1-mm units, in aging for indicated
³ time, days
³ 0 ³ 2 ³ 4 ³ 6 ³ 8
BND 40/60 ³ 59 ³ 57 ³ 56 ³ 53 ³ 50
BND 60/90 ³ 88 ³ 83 ³ 77 ³ 74 ³ 70
BND 90/130 ³ 120 ³ 115 ³ 110 ³ 102 ³ 98
) Penetration of asphalt at 25oC.