Influence of thermo-mechanical history on chemical and rheological
behavior of bitumen
M. Mouazen1, 2, A. Poulesquen1* and B. Vergnes2
1
CEA Marcoule, Direction de l’Energie Nucléaire, DTCD/SPDE/L2ED, BP17171,
30207 Bagnols sur Cèze (France)
2
MINES ParisTech, CEMEF, UMR 7635, BP 207,
06904 Sophia Antipolis Cedex (France)
1
Abstract
It is well known that asphaltene content plays an important role in determining the high
viscosity of bitumen. This paper presents an experimental study of the specific effects of
extrusion operating conditions on the physical and chemical properties of bitumen.
Five bitumen samples were prepared by twin screw extrusion with different operating
conditions (feed rate Q and screw speed N). Physical properties were studied by rheological
measurements. Viscosity values were measured by steady state flow tests. Chemical changes
in the bitumen structure were followed in the infrared region with Attenuated Total
Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) by measuring the
evolution of the bands areas at 1700 cm-1 (C=O), 1030 cm-1 (S=O), 1600 cm-1 (aromatics
C=C) and the bands between 900 and 730 cm-1 attributed to aromatics C-H. An increase of
feed rate Q induces a decrease of the Newtonian viscosity, due to a decrease of the asphaltene
volume fraction. The characterization by ATR confirms that the decrease of feed rate entails
the creation of C=O functional groups and the increase of sulfoxide (S=O) functional groups
and C=C bonds, accompanied by a decrease of the C-H aromatics bonds. These results
indicate a structure more oxidized and more aggregated at low feed rate, certainly due to an
increase of the residence time into the extruder. The increase of screw speed also induces a
decrease of the viscosity and of the volume fraction of asphaltenes, until a point after which
the situation reverses. This change may be explained by the appearance of new peaks between
1200 and 1050 cm-1, attributed to C=S bonds, and between 640 and 540 cm-1 for S-S bonds. A
competition between shear rate and residence time takes place. The thermomechanical history
has thus a great influence on the chemical and rheological behavior of pure bitumen and the
chemical changes observed show that the asphaltene volume fraction is not the unique
parameter which explains the variations of the viscosity.
Keywords: bitumen, extrusion, asphaltene, heteroatoms,
2
1. Introduction
Bitumen differ in their physical and chemical properties due to the nature of their crude oil
source and the operations involved in their production by fractional distillation [1]. They are
usually characterized by a large number of standards tests, which include penetration index,
softening point, asphaltene content and viscosity. Bitumen material can be considered as a
colloidal suspension in which the asphaltene particles (2–8 nm) are dispersed in a maltene
matrix [1]. The effect of asphaltene content on the heavy oil viscosity has been studied for a
long time. In order to estimate the effect of asphaltene content on viscosity, Dealy [2]
prepared a sample by adding 5 wt.% of asphaltenes to a bitumen with initial asphaltene
content of 16%. He observed that the viscosity was more than three times higher compared to
the initial bitumen. In the same way, Hénaut et al. [3] measured the rheological behaviour of a
heavy crude oil, which clearly shows an increase of viscosity with asphaltene content. The
viscosity of reconstituted oil with 18% of asphaltenes was 50 times higher than that of the
maltenes (0% asphaltenes) at 20°C. According to the studies of Hénaut et al. [3] and Pierre et
al. [4], a critical concentration in asphaltene was found and two domains were identified. The
first one concerns the dilute system in which the viscosity increases linearly with the weight
fraction m of asphaltenes and the second one is the semi-dilute domain, in which the relative
viscosity increases hardly with the asphaltene fraction. Altget and Harle [5] have given an
alternative explication of these two domains. For lower content, asphaltenes appear to consist
in single sheets of aromatics rings. These molecules can form aggregates, but these aggregates
have only a weak effect on the viscosity. For larger content, asphaltene molecules consist in
several sheets (higher than four) of condensed ring systems, connected by short bridging
branches. This has a strong effect on the viscosity. Luo and Gu [6] suggested the same
explanation but with three domains. The first one (v ≤ 5 vol.%) is the diluted region, where
the asphaltene particles are sufficiently far and the interactions among them can be considered
3
as negligible. In the second region, named concentrated region, the asphaltene particles
become closer and the interactions are more efficient, leading to the deviation of the relative
viscosity with the asphaltene volume fraction. Finally, in a third region called tangled region,
the relative viscosity diverges because of the existence of strong inter-particle interactions
among the dispersed asphaltene particles. Two domains can also be distinguished by plotting
the Newtonian viscosity of bitumen versus the inverse of absolute temperature, according to
an Arrhenius law. The calculation of the activation energy Ea confirms these two regions.
Mouazen et al. [7] and Hénaut et al. [3] reported a critical temperature around 50°C above
which a significant difference of activation energy was found. The increase of Ea for
temperatures lower than 50°C means that the structure of the heavy oil becomes more rigid. It
might be attributed to the appearance of interactions between asphaltenes which become
stronger below 50°C (the structure of bitumen becomes more rigid) whereas, above this
temperature, the Brownian motion is predominant and asphaltenes may move “more freely” in
the maltene matrix [7]. These two domains have also been identified by X-ray scattering but
most of the X-ray studies have been performed after dispersion of the asphaltene molecules
within an organic solvent, what is quite different from the real system (crude oil). However,
Barré et al. [8] and Pierre et al. [4] suggested the presence of two different domains
corresponding to Q-values larger and smaller than 2.5 10-3 A-1. They mentioned that the
region for large Q-values (higher than 2.5 10-3 A-1) is used for the determination of the form
and the size of asphaltene molecules. For smaller Q-values, a strong increase of scattered
intensity is observed, which corresponds to the presence of very large particles of asphaltenes
forming complex aggregates by Van der Waals and/or hydrogen bonds, which can be created
by polar molecules. The amount of heteroatoms (sulphur S, oxygen O and nitrogen N) and
polar molecules of the crude oil plays an important role in the association of the asphaltene
molecules. Moreover, the heteroatoms and their amount seem to have also a strong influence
4
on the chemical and physical properties of bitumen. Michalica et al. [9] suppose that a higher
content of heteroatoms leads to a higher degree of self-assembling and association of
molecules, which will result in an increase of the binder stiffness. On the other side, a lower
heteroatom content could be responsible for insufficient intermolecular associations, resulting
on a weak viscosity. Michalica et al. [9] was found out that the oxidative aging was
responsible for a further increase in the content of heteroatoms, mainly oxygen, which can
again result in an increase of the binder viscosity. Generally, the oxidation of bitumen results
in an increase of the asphaltene content and a decrease of the saturates and aromatics
contributions. Moschopedis and Speight [10], by exposing the bitumen to oxygen, have found
that the oxygen acts as a catalyst in the production of additional asphaltenes. Bitumen ageing,
thermo-oxidation process, UV radiation [11], and storage mode conditions lead also to
significant variations in bitumen properties. Two types of mechanisms are generally involved;
the first one is irreversible and is characterized by chemical changes, including oxidation and
loss of volatile components. The second mechanism is a reversible process, called physical
hardening; it may be attributed to a molecular structuring to approach an optimum
thermodynamic state [12]. The principal condition for the first mechanism is the presence of
oxygen and its insertion into the carbon chains, leading to the formation of oxygen-containing
groups. The aromatization (increase of the carbon-to-hydrogen ratio and formation of C=C
bonds) and finally the crosslinking process produced by the formation of inter- and intramolecular bonds also take place. At room temperature, the oxidation process is only possible
at the bitumen surface because the oxygen diffusion is limited [13]. However, the increase of
temperature leads to the acceleration of O2 diffusion process and an oxidation process is then
favoured. Several methods have been used to replicate the effect of ageing. Three major tests
are used: TFOT (Thin Film Oven Test), RTFOT (Rolling Thin Film Oven Test) [12, 14] and
5
PAV (Pressure Ageing Vessel) [15]. Recently, a new method was developed through thermooxidation in a rheo-reactor [16].
In the present work, we investigate the influence of extrusion conditions (screw speed N and
feed rate Q) on the pure bitumen behaviour. Indeed, in nuclear industry, twin screw extrusion
is used to embed radioactive elements into a bitumen matrix. This thermomechanical history
has a great influence on the chemical and physical behavior of pure bitumen. The chemical
changes, mainly due to oxidation and mechanical stresses, will be assessed by infrared
spectroscopic techniques. On the other hand, the physical modifications will be analysed by
rheological characterisations.
2. Experimental
2.1. Preparation of the extruded bitumen
Pure bitumen (Azalt 70/100, provided by Total) was introduced at a temperature of 140°C in
the feeding zone of a laboratory scale co-rotating twin screw extruder (Werner ZSK25WLE:
length L = 1000 mm, screw diameter D = 25 mm, L/D = 40). The barrel temperatures were set
between 140 and 180°C.
The used bitumen mainly consists in carbon (typically 84.71 wt.%) and hydrogen atoms
(10.23 wt. %). In addition, heteroatoms such as sulphur (4.35 wt.%), nitrogen (1.33 wt.%) and
oxygen (0.53 wt. %) are generally present. Traces of metals are also found, the most
numerous being typically vanadium (116 ppm) and nickel (37 ppm). The ratio C/H for the
used bitumen is nearly 0.69.
Five extruded samples have been prepared using three different screw speeds N (rpm) and
three different feed rates Q (g/h). Extrusion conditions are given in Table 1.
6
2.2. Rheological study
The rheological properties were analyzed using a controlled stress rheometer (MCR 301,
Anton Paar) in parallel plate geometry, with 25 mm diameter and 1 mm gap. The rheometer
has been used in strain mode. For dynamic tests, the strain sweeps were conducted with a
frequency of 100 rad/s by varying the strain from 10-6 to 100 to determine the linear
viscoelastic region of the samples. The frequency sweeps were then performed from 100 to
0.01 rad/s at a strain value within the linear viscoelastic domain. The flow curves were
obtained by starting from 10-6 up to 100 Pa (5 stress levels per decade) and measuring the
corresponding viscosity once steady state flow was observed.
2.3. Asphaltene/maltene separation
The experimental procedure for the separation of asphaltenes from the bitumen consists in
mixing 1g of bitumen with 40 mL n-pentane, which was used as a precipitant. The mixture
was agitated for 4 h and then filtered through a 3 µm filter paper. The precipitated asphaltenes
were kept rinsing with n-pentane until having a light brown colour. The precipitated and the
remaining maltenes were slowly dried under the fume for 12h and then for 12 h in oven at
50°C.
2.4. Infrared spectra
Chemical changes in the bitumen structure were followed by Fourier Transform Infrared
Spectroscopy (ATR-FTIR) (ThermoScientific) by measuring the evolution of the band areas
at 1700 cm-1 (C=O), 1030 cm-1 (S=O), 1600 cm-1 (C=C double bonds) and three bands
included between 900 and 730 cm-1 attributed to the C-H aromatics. Several indices were
calculated from the areas of IR bands shown in figure 1 [17]. They are characteristic of
oxidation (A1700/∑A), aromaticity (A1600/∑A), aliphaticity ((A1452 + A1373)/∑A), ramification
7
(A1373/A1452 + A1373), presence of sulfoxyde group (A1030/∑A), presence of aromatic H
((A874+A809+A747+A720)/∑A) : 747 cm-1 (4 or 5 adjacent C-H), 809 cm-1 (2 adjacent C-H) and
874 cm-1 (one isolated C-H) [17, 18]. The sum of the areas is calculated from:
∑ A = A1700cm-1 + A1600 cm-1 + A1452 cm-1 + A1373 cm-1 + A1030 cm-1 + A874 cm-1 + A809 cm-1 + A747 cm-1 + A720 cm-1
3. Results
3.1. Rheological characterizations
3.1.1. Effect of feed rate
Figure 2 presents the evolution of the dynamic storage modulus G’ with strain amplitude, at
100 rad/s and 50°C for the three samples A, B and C. It is observed that the storage modulus
clearly decreases with the feed rate. In the same time, the critical strain slightly γc increases,
from 0.16 to 0.25. Similar results were observed for the loss modulus (G”) and the complex
viscosity (η*). Figure 3 shows the evolution of the shear viscosity obtained from steady state
flow tests for the three samples. The behaviour is globally Newtonian, with a yield stress
appearing at very low shear rate (less than 10-4 s-1). The decrease above 10 s-1 is due to sample
fracturation [7]. We observe a decrease of the Newtonian viscosity η when increasing the feed
rate Q. The values of η are 540, 640 and 950 Pa.s for the three samples A, B and C,
respectively.
To further investigate the microstructure, dynamic frequency sweep tests have been
performed. Figure 4 presents the plot of storage modulus G’ versus angular frequency ω in
the linear region (γ = 0.001) for the three samples, measured at 50°C. At high pulsation, we
observe an increase of G’ when Q decreases, which is consistent with the previous results
obtained in strain sweeps. On the other side, at low pulsation, a plateau appears which is
characteristic of a solid-like behaviour. This effect is more pronounced for the lowest feed
rates with a larger plateau. On the other hand, the loss modulus G” (not represented here)
8
scales as  at low pulsations. These results globally indicate an increase in the interactions
between asphaltene particles (v of asphaltenes is more) when the feed rate is decreased.
In the literature, this phenomenon is often related to a secondary relaxation process, related to
the existence of a structure resulting from the interactions between the asphaltene aggregates
[7, 19]. In other words, at low angular frequency, the particles of asphaltene have the time to
restructure and to approach an optimum thermodynamic state under a specific set of
conditions (formation of aggregates).
3.1.2. Effect of screw speed
Figure 5 presents the evolution of the dynamic storage modulus G’ with strain amplitude,
measured at 50°C for the three samples C, D and E, produced at different screw speeds N. We
observe first that the changes of G’ values with N are more pronounced than with Q. The
increase of N from 70 to 150 rpm leads to a decrease of the storage modulus G’ (from 1.66
104 to 2.6 103 Pa) and an increase of the critical strain (from 0.16 to 0.25), but the situation
reverses for the sample E extruded at 300 rpm (G’ = 5.2 103 Pa, c = 0.20). On Figure 6 we
present the frequency sweep tests for these three samples. On the whole pulsation range, the
same ranking as in strain sweep tests is obtained. Once again, we observe the development of
a plateau for G’ at low pulsations.
3.2. Asphaltene/maltene separation
In order to explain the differences in the rheological behaviour, the asphaltene content for the
five samples has been evaluated by separating asphaltenes and maltenes using n-pentane as
solvent. The volume fraction is calculated from:

bitumen
wt.%
asphaltene
(1)
9
where ρbitumen = 1.02 g/cm3 is the density of bitumen, ρashaltene = 1.165 g/cm3 is the density of
asphaltenes and wt% is the weight percentage of asphaltenes.
The Newtonian viscosity of the bitumen with zero asphaltene content (i.e. maltenes) was also
measured. Its value is 14 Pa.s at 50°C. All the data resulting from these analyses are listed in
Table 2.
4. Discussion
4.1 Effect of feed rate
According to the Table 2, it is observed that, at constant screw speed (70 rpm), the decrease of
feed rate from 1150 to 395 g/h leads to an increase of asphaltene volume fraction from 17.6 to
24%, accompanied with an increase in viscosity (from 540 to 980 Pa.s at 50°C). A variation
of 5.5 wt.% of asphaltene content leads to a viscosity two times higher. The loss and storage
modulus are also higher and, at low pulsation, the formation of asphaltene aggregates is more
pronounced when the volume fraction of asphaltenes increases. In order to deeper interpret
these results from a microstructural point of view, a series of infrared measurements have
been conducted. Figure 7 shows the changes in infrared spectra for the three samples A, B and
C. The decrease of feed rate induces an increase in the carbonyl (C=O) absorption band at
1700 cm-1. Other absorption bands, such as C-O single bond stretching ( 910-1300 cm-1) and
sulfoxide S-O (1030 cm-1), are also increased with the decrease of feed rate. The area values
for each peak are listed in Table 3. In addition, Figure 7 also shows that the C=C aromatic
bonds at 1600 cm-1 grow, and the area of the 3 bands between 900 and 730 cm-1,
characterizing the C-H aromatics bonds, decreases with the decrease of feed rate. This
indicates that the ratio C/H increases, which means that the aromatics rings fused to produce
some sheets of asphaltenes. Consequently, the structure becomes more compact. Therefore, an
increase of the asphaltenes content is observed both from macro- and microscopic points of
10
view. The residence time of the bitumen in the extruder could be the main cause of this
variation. Indeed, in a twin screw extruder, the residence time increases when the feed rate
decreases [20]. In our conditions, we can estimate the average residence time at 162, 202, and
368 s, for the feed rates of 1150, 840 and 395 g/h, respectively. Consequently, a long
residence time allows the material to “restructure” and therefore to promote the diffusion of
oxygen, leading to a more oxidized matrix. The high temperature of the extruder barrels (140180°C) facilitates the oxygen diffusion and leads also to accelerate the aging process,
entailing an increase of the asphaltene content and size [16].
4.2 Effect of screw speed
At constant feed rate, according to the Table 2, an increase of screw speed leads to a decrease
of the viscosity and asphaltene volume fraction until a value above which these two
parameters increase again. An observation of the microstructure by infrared spectroscopy
clarifies the situation and explains why this change is observed. Figure 8 shows the effect of
the screw speed on infrared spectra for the three samples C, D and E. By comparing the
samples C and D, we see that an increase of screw speed leads to a decrease of the area of the
bands C=C, C=O, S=O and an increase of the C-H bands. All the values are listed in Table 4.
Thus, for the sample at 150rpm, it seems that the oxidation is reduced, but it cannot be
explained by the residence time, which is similar: 368 s at 70 rpm and 370 s at 150 rpm.
However, the infrared spectrum for the sample E at 300 rpm is very different. Indeed, a high
asphaltene content is observed, concomitant with a decrease of oxidation peaks (C=O) and
aromatics C=C bands, indicating a lower oxidation. It does not seem very coherent with the
previous results where an increase in asphaltene content was accompanied by an increase of
the oxidation and aromatization peaks. But some new peaks appear in the region 1200–500
cm-1: an intense C=S band at 1200-1050 cm-1 and a S-S band around 640-540 cm-1 are clearly
identified. These two sets of peaks could be the principal cause of the increase of viscosity
11
and asphaltene content. Unlike to the other operating conditions, where the residence time in
the extruder dominates, for the high screw speeds, the generated shear rate (which is
proportional to the rotation speed) probably becomes the dominant parameter. Consequently,
the specific mechanical energy supplied by the extruder is sufficient to modify the
microstructure by the creation of inter- or intra-molecular bonds, leading to an increase of
asphaltene content. In fact, the high content of heteroatoms, especially sulphur (4.35%),
facilitates the achievement of self-assembling and association of molecules (C=S and S-S),
proofed by FTIR, which will result in a higher stiffness of the bitumen.
4.3 Discussion
A paradoxical result is obtained for the two samples B and D. Indeed, they have
approximately the same asphaltene volume fraction (16.5 for B and 17.1 for D) but the
Newtonian viscosity of B in more than two times higher than the one of D (640 versus 295
Pa.s). If we compare the FTIR data for B and D samples, we notice that the carbonyl peak
C=O is higher for D, what is completely coherent with the residence time in extruder. Indeed,
the estimation of the residence time leads to 202 s for B compared to 370 s for D. On the other
hand, the aromatic (C=C) and sulfoxyde (S=O) peaks are higher for B sample, what is
coherent with the viscosity evolution. Consequently, we can assume that the increase of screw
speed from 70 to 150 rpm induces a separation of heteroatoms or polar molecules, which
leads to smaller asphaltene aggregates (the number of sheets of asphaltene into the aggregates
decreases). Therefore, a competition between screw speed (shear rate, strain and specific
energy) and feed rate (residence time) takes place, and the viscosity of bitumen is given by a
compromise between the asphaltene content and the quantity of heteroatoms existing and/or
inserted into the bitumen.
12
In twin screw extrusion, the variations of screw speed N and feed rate Q are currently
accounted for by considering the ratio N/Q, to which the specific energy is proportional. In
order to better interpret the previous results, we have plotted in Figure 9 the different area
ratios determined by ATR-FTIR as function of this ratio. It clearly evidences the existence of
two domains defining the evolution of the bitumen structure and composition. For N/Q
smaller than approximately 18 r/g (low speed region), we observe an increase of oxidation
and simultaneously a decrease of C-H bonds to the benefit of C=C bonds. Above 18 r/g (high
speed region), oxidation decreases and C-H bonds increase to the detriment of C=C bonds.
The viscosity of the bitumen is directly affected by these structural evolutions.
5. Comparison between experimental results and rheological models
In the literature, there are a lot of theoretical models and empirical correlations for predicting
the crude oil viscosity. However, most of these models are based on a simplified system
where asphaltenes are dispersed in an organic solvent, due to the rather complex structure and
composition of the crude oil [4, 8, 21]. According to the literature, the suitable structure of
bitumen is a colloidal suspension in which the asphaltene particles (2 – 8 nm) are dispersed in
a maltene matrix [1]. It is well know that the relative viscosity of a colloidal dispersion can be
expressed by a Krieger-Dougherty type equation, as the ratio of the viscosity η of the colloidal
dispersion to the viscosity of the dispersing liquid η0 [22, 23]:
r 


 (1  eff )
0
max
(2)
where η0 is the viscosity of the dispersing liquid, ν is the shape factor of the dispersed
particles, max is the maximum packing volume fraction and eff is the effective volume
fraction of the dispersed phase. In a colloidal dispersion, eff can also be expressed as a
function of a salvation constant K and the real volume fraction :
13
eff = K
(3)
The shape factor ν of the asphaltene particles is variable. 2.5 is often proposed for rigid
spherical particles but, for ellipsoidal and disk-like forms, it is more than 2.5. Luo and Gu [6]
have found that the asphaltene particles have a non-spherical shape (ν in the range 5-6) and
probably different sizes, i.e. a polydisperse size distribution. The maximum packing volume
fraction of asphaltenes of the crude oil is also very difficult to apprehend since it is structure
and origin dependent. Storm et al. [24] found that the maximum volume fraction max of
asphaltene particles was close to 0.35. Luo and Gu [6] estimated this value to be in the range
0.6 – 0.7. Figure 9 presents the evolution of the relative viscosity of extruded samples as a
function of the volume fraction of asphaltenes. First of all, we see that we do not obtain a
mastercurve, what indicates that the volume fraction is not the unique parameter which
controls the viscosity. As shown previously, it seems that we can select two families of data,
each one being more or less described by a Krieger-Dougherty relationship (Eqs. (2) and (3)):
the samples made in low speed conditions (70 rpm) provides a maximum packing fraction
max of 0.37 and a shape factor ν of 5.5. The samples made at high speed (150 and 300 rpm)
give a max of 0.36 and a ν of 4.5. These values are close to those reported in the literature but
this distinction as function of screw speed would remain to be confirmed. These results are
related to a modification of the composition or the structure of asphaltene particles. More
specifically, the oxidation process favored at low speed, by creating new picks observed by IR
spectroscopy (C=O and S=O), could explain these differences, by a change in the amount or
the proportion of heteroatoms.
14
6. Conclusions
Extrusion operating conditions significantly influence bitumen chemistry and rheology, by
ageing or mechanical processes. Ageing produces fundamental modifications in the
asphaltene content of bitumen and in their chemical properties. Chemical changes include the
formation of carbonyl and sulfoxide bonds and an increase of C=C bands. The chemical and
rheological changes are generally consistent. Actually, the ageing effect is strongly dependant
on extrusion operating conditions. The decrease of the feed rate leads to an increase in sample
viscosity due to an increase of the asphaltene volume fraction. This is certainly due to an
increase of the residence time into the extruder, where the structure becomes more oxidized
and more compact due to the great oxygen diffusion process. Similar results were obtained
with the increase of screw speed, until a point where the situation reverses. This change has
been related by ATR-FTIR to the apparition of news peaks (C=S, S-S) and is probably due to
the high shear rates supplied by the extruder. A competition between shear rate and residence
time takes then place. The thermomechanical history has thus a great influence on the
chemical and rheological behaviour of pure bitumen and the chemical changes observed show
that the asphaltene volume fraction is not the unique parameter which explains the variations
of the viscosity. Besides, the heteroatoms and their content play also a role in the chemical
and physical properties of bitumen. A higher content of heteroatoms leads to higher degree of
self-assembling (intra-molecular bonds) and association of molecules (inter-molecular bonds),
which will result in a higher viscosity.
The use of a Krieger-Dougherty equation to describe the relationship between the viscosity of
the crude oil and the asphaltene content is not evident, due to the complexity of the crude oil
and its sensibility to the oxidation process. A simple variation of the amount of heteroatoms
leads to a major modification of the structure and of the shape of asphaltenes particles. To
summarize, we can conclude that, at low screw speed, oxidation is the major mechanism
15
which controls the increase of asphaltene content and the viscosity. At high screw speed,
oxidation is balanced by the shear induced reduction of asphaltene aggregates.
16
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investigation of oxidation and phase evolution in bitumen modified with polymers. Fuel
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toluene/heptane solvents. Langmuir 1998; 14:1013-1020.
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18
[23] Quemada D. Rheology of concentrated disperse systems and minimum energy
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72:233-7.
19
Table 1 - Extrusion conditions
Sample
Screw speed
Feed rate
Residence time
N (rpm)
Q (g/h)
(s)
A
70
1150
162
B
70
840
202
C
70
395
368
D
150
360
370
E
300
372
347
20
Table 2 - Asphaltene mass and volume fractions and Newtonian viscosity at 50°C
for each sample.
Sample
A
B
C
D
E
F
Screw
speed
N (rpm)
70
70
70
150
300
-
Feed rate
Q (g/h)
1150
840
395
360
372
-
Asphaltene Asphaltene
Viscosity
content
content
(Pa.s)
(% wt)
(% vol)
17.6
15.5
540
18.75
16.5
640
24
21.1
980
19.5
17.1
295
21.9
19.2
430
0
0
14
21
Table 3 - Area values for some peaks of the samples A, B and C,
where A is the total area between 2000 and 400 cm-1.
Samples
A
B
C
A (C=O)/A
(1700 cm-1)
0
1.6 10-3
6.73 10-3
A (C=C)/A
(1600 cm-1)
0.027
0.032
0.037
A (S=O)/A
(1030 cm-1)
0.005
0.010
0.012
A (C-H)/A
(900-730 cm-1)
0.153
0.148
0.108
22
Table 4- Area values for some peaks of the samples C, D and E,
where A is the total area between 2000 and 400 cm-1.
Samples
C
D
E
A (C=O)/A
(1700 cm-1)
6.73 10-3
3.12 10-3
1.72 10-3
A (C=C)/A
(1600 cm-1)
0.037
0.023
0.013
A (S=O)/A
(1030 cm-1)
0.012
7.39 10-3
0.001
A (C-H)/A
(900-730 cm-1)
0.108
0.076
0.088
23
Figure Captions
Figure 1 - Typical ATR-FTIR transmission spectrum of bitumen.
Figure 2 - Storage modulus G’ vs. strain for bitumen prepared at constant speed (70 rpm) and
different feed rates (100 rad/s, 50°C).
Figure 3 - Viscosity vs. shear rate for bitumen prepared at constant speed (70 rpm) and
different feed rates (100 rad/s, 50°C).
Figure 4 - Storage modulus G’ vs. pulsation for bitumen prepared at constant speed (70 rpm)
and different feed rates (100 rad/s, 50°C).
Figure 5 - Storage modulus G’ vs. strain for bitumen prepared at constant feed rate ( 375
g/h) and different screw speeds (100 rad/s, 50°C).
Figure 6 - Storage modulus G’ vs. pulsation for bitumen prepared at constant feed rate ( 375
g/h) and different screw speeds (100 rad/s, 50°C).
Figure 7 - ATR-FTIR spectra of the three samples at different feed rates.
Figure 8 - ATR-FTIR spectra of the three samples at different screw speeds
Figure 9 – Area ratios obtained by ATR-FTIR as function of N/Q ratio; a) for S-O and C-O
bonds (oxidation), b) for C-H and C=C bonds (aromatization)
Figure 10 - Measured relative viscosity of the bitumen samples versus the asphaltene volume
fraction at 50°C (symbols) and theoretical fit by Krieger-Dougherty equations (full lines)
24
*bitume pur 10-02-2010
2916
0, 50
0, 45
2845
0, 40
0, 30
0, 10
747
809
1699
3057
0, 15
1030
1591
1373
0, 20
874
0, 25
720
1452
Absorbance
0, 35
0, 05
0, 00
35 00
30 00
25 00
20 00
18 00
16 00
14 00
12 00
10 00
80 0
60 0
Wavenumbers (cm-1)
Fig. 1 Mouazen et al.
25
Storage modulus (Pa)
10
5
Q = 395 g/h
10
4
Q = 840 g/h
Q = 1150 g/h
3
10
-4
10
10
-3
-2
10
10
Strain (-)
-1
10
0
1
10
Fig. 2 Mouazen et al.
26
Viscosity (Pa.s)
10
4
10
3
Q = 395 g/h
Q = 840 g/h
Q = 1150 g/h
2
10
-5
10
10
-4
10
-3
10
-2
10
-1
10
0
1
10
-1
Shear rate (s )
Fig. 3 Mouazen et al.
27
Storage modulus G' (Pa)
10
5
10
4
10
3
10
2
10
1
10
0
10
Q = 395 g/h
Q = 840 g/h
Q = 1150 g/h
-1
10
-2
10
-1
0
10
10
Pulsation (rad/s)
1
2
10
Fig. 4 Mouazen et al.
28
Storage modulus G' (Pa)
10
5
70 rpm
10
4
10
3
300 rpm
150 rpm
2
10
-4
10
10
-3
-2
10
Strain (-)
10
-1
0
10
Fig. 5 Mouazen et al.
29
Storage modulus G' (Pa)
10
5
10
4
10
3
10
2
10
1
10
0
70 rpm
10
-1
10
-2
300 rpm
10
150 rpm
-2
10
-1
0
10
10
Pulsation (rad/s)
1
2
10
Fig. 6 Mouazen et al.
30
W 0 9-0 06 l e 10 -0 2 -2 01 0
0,45
W 0 9-0 07 0 8 -0 2-2 01 0
1 – C=O
2 – Aromatics C=C
3 – Aromatics C-H
4 – S=O
W 0 9-0 12 l e 10 -0 2 -2 01 0
0,40
Absorbance
Absorbance
0,35
A
B
C
4
2
3
0,30
0,25
0,20
1
0,15
0,10
4000
3000
2000
Waved'onde
number
(cm
Nombre
(cm-1)
1000
-1)
Fig. 7 Mouazen et al.
31
0,45
W 0 9-0 12 l e 10 -0 2 -2 01 0
w 0 9-0 21 le 10 -02 -10
W 0 9-0 18 l e 10 -0 2 -2 01 0
1 – C=O
2 – Aromatics C=C
3 – Aromatics C-H
4 – Thiocarbonyle C=S
5 – Disulfur S-S
2
0,40
Absorbance
Absorbance
0,35
0,30
C
D
E
4
5
3
0,25
0,20
1
0,15
0,10
4000
3000
2000
Nombre
(cm-1)
Waved'onde
number
(cm-1)
1000
Fig. 8 Mouazen et al.
32
0,014
a)
C
Area value (-)
0,012
0,010 B
Low speed
0,008
0,006
A
E
D
B
E
A
0,000
0
10
20
30
N/Q ratio (r/g)
40
50
b)
A B
High speed
0,120
Area value (-)
D
C-O
0,002
0,140
High speed
C
0,004
0,160
S-O
C
0,100
E
0,080
C-H
0,060
Low speed
0,040
D
C=C
B C
0,020
A
D
E
0,000
0
10
20
30
N/Q ratio (r/g)
40
50
Fig 9. Mouazen et al.
33
Relative viscosity (-)
100
80
60
Low speed: 70 rpm
40
20
High speed: 150-300 rpm
0
0
5
10
15
20
Asphaltene volume fraction (%)
25
Fig. 10 Mouazen et al.
34