VOL. 2, NO.

5, June 2012 ISSN 2225-7217

ARPN Journal of Science and Technology

©2011-2012. All rights reserved.

http://www.ejournalofscience.org

Viscosity Characteristics of Modified Bitumen

*Suleiman Arafat Yero, and Mohd. Rosli Hainin
Department of Geotechnics/Transportation,
Fakulti Civil, Universiti Teknologi Malaysia, 81310 skudai, Johor Malaysia.
* arafatyero@yahoo.com

ABSTRACT
The effect of commercial additive Sasobit wax (S) on the viscosity characteristics of bitumen 60/70-penetration grade is
yet to be fully understood. The viscosity of bitumen is the measure of its resistance to flow which affects workability, and
resistance to deformation of the mixture. This study reviewed the bitumen modification process in relation to warm mix
asphalt (WMA) technology, using S as a modifier. The study investigated the viscosity measurements of modified
bitumen, using the Brookfield viscometer. The binders mixed with various percentage of the wax S 1%, 2%, 3%, 4%and
5% were investigated. The results from the study showed the viscosity of the binder decreasing at higher temperatures
while at midrange temperatures the viscosity increases with an increase in the additive. This study has provided a valuable
data on the effect of the additive S on increasing the dynamic viscosity of the binder at low temperature and decreasing the
kinematic viscosity at high temperature, been attributed to the presence of the S wax with high hydrocarbons molecular
content in the binder, which is expected to improve the viscosity properties of the modified binder and enhance its
resistance to deformation when used in warm asphalt concrete mixtures.

Keywords: Viscosity, Sasobit, Bitumen, Rheology, and Modification

1. INTRODUCTION
Bitumen is a thermo-visco-elastic material concern. This has prompted a strong interest in
where temperature and rate of load application have a developing alternative means of enhancing the
great influence on their behavior [1]. They are classified performance of the bitumen used in the production of
ass rheological materials since their viscosity stress and asphalt concrete; these include modification of the
strain response is both time and temperature dependent binder with either organic additives like S or polymers.
[2]. The binder consistency and hence ability to sustain
and hold its fundamental cementing mechanism changes Bitumen is a rheological, thermoplastic and
depending on its viscosity [3]y. In the study bitumen viscoelastic material. Its deformation characteristics vary
with penetration grade 60/70 were modified with sasobit not only with load, but also with time rate of load
wax (S), which is obtained from coal gasification using application and temperature. It is neither elastic nor
the Fischer-Tropics process, with long-chain viscous in behavior. At low temperature it exhibits
hydrocarbon [4]. elastic behavior while at high temperature it exhibits
viscous behavior [7]. The neat binders lack the proper
The viscosity of bitumen is its internal viscous-elastic balance that usually occurs due to an
resistance to flow or measure of it resistance to effective elastic network created by molecular
deformation by either shear stress or tensile stress and a association. It is hypothesized that proper visco-elastic
significant parameter in determining the bitumen balance can be formed by creating molecular
rheology and engineering properties of asphalt concrete; entanglement in a bitumen through the use of high
it influences the workability and resistance to mix [2]. molecular weight polymeric additives.
The viscosity of bitumen shows a complex response
under different conditions and it influences the mixing, The performance of asphalt pavement is
laying and compaction of asphalt mixtures as well as the mainly governed by the properties of the binder.
pavement performance [5]. In view of these reasons Bitumen exhibit’s a visco elastic behavior hence in
viscosity measurements have been used to classify pavement when exposed to high temperature permanent
bitumen, but due to the visco-elastic nature of bitumen’s deformation (Rutting) takes place along the wheel path
the results lack uniformity as the bitumen source and of the pavement. On the other hand, bitumen in
molecular content might differ [6] pavement at low temperature exhibits brittleness and
pavement cracking occurs.
Most of the roads in Malaysia are constructed
as asphalt concrete pavements, which mainly consist of This study investigated the viscosity at
bitumen, and aggregate. The bitumen though in smaller production and working temperature of neat and
quantity as compared to the aggregate serves as a binder modified bitumen’s. In this study the commercial
to the pavement materials. The recent increase in traffic additive S was used to lower viscosity of the binder at
volume, resulting too intense loading of the pavements high temperature, making it less susceptible to high
across the country with severe consequences leading to temperature damage, and flow improver at low
permanent deformation of the pavement is of great temperature. The additive S is introduced to warm mix

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 VOL. 2, NO. 5, June 2012 ISSN 2225-7217

ARPN Journal of Science and Technology

©2011-2012. All rights reserved.

http://www.ejournalofscience.org
asphalt (WMA) by blending with the binder at the influence of the additive on the viscosity of the binder at
terminal or contractor’s tank. The recommended addition midrange and high temperatures, which. The viscosity of
rate is 0.8% to 3% by mass of the binder according Sasol each bitumen sample with and without S was measured
report (2003). At high temperatures S lowers the at various test temperatures at a shear rate of 6.8/s. This
viscosity of the binder such that working temperatures shear rate was selected because it conforms to the
decrease by 45ºC [2]. rotational speed of 20rpm with the brooks field Spindle
27 recommended for Super pave (SHRP). The kinematic
The additive has a congealing temperature of viscosity was measured at 135oC while the dynamic
about 100ºC and is completely soluble in binders at viscosity was not measured at 60oC as required, this was
temperatures lower than 110ºC, at temperatures below its due to hardening of the modified binder hence it was
melting point, it forms a crystalline network structure in tested at 75oC
the binder that is reported to provide added stability as
the bitumen stiffens at low temperature [1]. Penetration and softening point
Viscosity is also termed to be a measure of The penetration grade of the neat bitumen with
deformation of fluid due to shear stress or tensile stress, and without S was investigated using the penetro meter
and is a fundamental parameter in the investigation of in accordance with ASTMD5-97 specification, while the
the rheological properties of bitumen. Previous softening point of the various test samples was
researches included studied the effect of wax on the determined using the ring and ball test in accordance to
basic and rheological properties of bitumen with similar ASTM D36-95 specifications.
penetration grades [8]. Results from the study indicated
good correlation between the wax content in bitumen 3. RESULTS
under a high temperature environment.
The primary objective of the study was to
Edwards studied the rheological properties of determine the viscosity and shear stress of the modified
commercial waxes and poly phosphoric acid in bitumen bitumen. The table 1 below shows the combination of
at high and medium temperature performance. Results bitumen and various % of S. From the study there is a
from the study showed adding polyethylene wax to decrease in the viscosity of the binder at high
bitumen effects its rheological properties at medium and temperature as the S was increased and this could be
higher temperatures. Also the influence of styrene- attributed to the presence of the additive.
butadiene- styrene (SBS) polymer modification on
bitumen viscosity. Results from the study showed SBS It can also be seen from Table 2 and Figure 1
modified bitumen’s to have increase degree of non- below that the addition of the S additive reduced the
Newtonian behavior. The linear SBS modified bitumen’s viscosities of the various binder mixes at 150oC.
demonstrated a high degree of shear thinning behavior
compared to base bitumen’s. Table 2: Bitumen 60/70 Viscosity at 150oC

2. EXPERIMENT AND MATERIAL Des. B+ B+ B+ B+ B+ B+

0% 1% 2% 3% 4% 5%
For this study neat bitumen PEN 60/70 from an S S S S S S
unknown source and pellets of sasobit wax (S) supplied CP 200 200 150 110 100 100
by sasol international was used for the study. Neat and SS 13.6 13.6 10.2 7.5 6.8 6.8
modified bitumen totally 30 samples, with various SR 6.8 6.8 6.8 6.8 6.8 6.8
content of S 0%, 1%, 2%, 3%, 4%, and 5% were T% 0.2 0.2 0.1 0.1 0.1 0.1
investigated in the study.
Where B is bitumen and S is sasobit
Some physical-chemical characteristics of the
bitumen used in this study can be seen in tables I below;

Table 1

s ASTM Bitumen
Penetration (dmm) D5-97 67
Softening point (oC) D36-95 49

Viscosity: The viscosity of the binder was

measured using the brooks field viscometer; the
equipment was used to measure the viscosity
characteristics of the neat and modified binder Fig. 1: Viscosity at high temperature
PEN60/70 (with and without S). This study determined

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ARPN Journal of Science and Technology

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It can also be seen from Table 3 below that the An ideal binder for road application should
addition of the S additive reduced the viscosities of the posses’ constant properties high temperature
various binder mixes at 135oC susceptibility to change to a viscous fluid for effective
mixing and compaction and low temperature
Table 3: Bitumen 60/70 Viscosity at 135oC susceptibility over the ambient temperature range.
However, bitumen’s do not behave in that manner but
Des B+ B+ B+ B+ B+ B+ exhibit a continues change in their viscosity over the
0%S 1%S 2%S 3%S 4%S 5%S whole operational temperature. The addition of S at high
CP 410 400 300 200 200 100 temperature resulted in the decrease in viscosity, which
SS 27.9 27.2 20.4 13.6 13.6 6.8 should show increase resistance to rutting and thermal
SR 6.8 6.8 6.8 6.8 6.8 6.8 cracking at high and low temperatures, respectively.
T% 0.3 0.3 0.2 0.2 0.1 0.1
The modified bitumen’s have indicated an
From the study the addition of S at 135oC improvement in their properties this could be attributed
temperature indicated a reduction in the viscosity of the to the additive networks and entanglements as well as
binder as can be seen in Figure 2 below; interactions of the S aliphatic hydrocarbons with
bitumen, that inhibits association or dissociation of
molecules as temperature changes. At low temperature
changes the bitumen shows an elastic behavior. From the
study the addition of S to the binder when investigated
using the Brookfield viscometer indicated an increase in
viscosity at 100oC as can be seen in table 4 below;

Table 5: Bitumen 60/70 Viscosity at 100oC

Des. B+ B+ B+ B+ B+ B+
0%S 1%S 2%S 3%S 4%S 5%S
CP 2550 2920 3700 3850 4110 4200
Fig 2: kinematic viscosity SS 173.5 198.6 251.7 261.9 278.9 285.7
SR 6.8 6.8 6.8 6.8 6.8 6.8
From the Table 4 below the study indicates that T% 2.5 2.5 2.7 2.7 3.0 3.1
the addition of S at 120oC resulted in a decrease in
viscosity of the binder as the additive content was The viscosity test at 100 oC indicated an
increased increase viscosity as the additive was increased in the
binder as could be seen in figure 4 below;
Table 4: Bitumen 60/70 Viscosity at 120oC

Des B+ B+ B+ B+ B+ B+
0%S 1%S 2%S 3%S 4%S 5%S
CP 950 950 700 600 500 400
SS 64.62 64.62 47.6 40.8 34.0 27.2
SR 6.8 6.8 6.8 6.8 6.8 6.8
T% 0.7 0.7 0.6 0.6 0.5 0.4

From the study the addition of S at 120oC

temperature indicated a reduction in the viscosity of the
binder as can be seen in Figure 3 below;

Fig 4: viscosity trends

From the study at lower temperature of 60oC

the Viscosity of the binder increases with an increase in
S as can be seen in Table 6 and Figure 5 below

Fig 3: viscosity trends Table 6: Bitumen 60/70 Viscosity at 60oC

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Des. B+ B+ B+ B+ B+ B+ ACKNOWLEDGMENT
0%S 1%S 2%S 3%S 4%S 5%S
CP 28100 28000 33100 34300 47100 49300 The study as described in this paper was carried
SS 1911. 1904. 2251. 2333. 3204. 3353.7 out in the department of highway and transportation,
6 8 7 3 0 faculty of Civil engineering University Technology
SR 6.8 6.8 6.8 6.8 6.8 6.8 Malaysia (UTM). The commercial additive sasobit wax
used in the study was supplied by sasol international of
T% 25.0 25.0 31.1 31.1 42.1 42.1
South Africa, all are acknowledged.
It can also be seen in Figure 5 below that the
addition of the additive increased the viscosity of the
REFERENCES
modified bitumen at the lower temperature of 60oC,it
[1] O. Kristjansdottir, “Warm Mix Asphalt for Cold
indicated that the viscosity of the binder increases with
Weather Paving” University of Washington
an increase in the % of S.
masters thesis 2006

[2] T.S. Gandhi, and S.N. Amirkhanian, “Laboratory

Evaluation of Warm Asphalt Binder Properties”
Clemson university PhD thesis 2008.

[3] G. Hurley, and B. Prowell, “Evaluation of

Potential Process for use in Warm Mix Asphalt”,
Journal of the Association of Asphalt Paving
Technologist” 2006, Volume 75, pp 41– 90.

[4] NCAT Evaluates Warm Mix Asphalt, Asphalt

Technology News, Volume 17, Number 2, fall
2005, pp 1-8.

Fig 5: Dynamic viscosity [5] C. Binard, et al. “Zero Shear Viscosity of

Modified and Unmodified Binders”, 3rd
Eurasphalt & Eurobitume Congress Vienna 2004,
Paper 236, pp 1721-1733
4. CONCLUSSION
[6] Y. Edwards, and P. Redelius, “Rheological
This study has indicated that the additive S
Effects of Waxes in Bitumen”,J of Ener and
increases the dynamic viscosity of the binder at low
Fuels, American Chemical Society, Volume 17,
temperature and decreases the kinematic viscosity at
Number 3, 2003.
high temperature. The addition of S significantly reduces
the viscosities of the binder at temperatures above
[7] X. Lu, and U. Isacsson, “Effect of aging on
100oC. The additive wax used in this study was to
bitumen chemistry and rheology,” J of
modify the binder, subsequently used to lower the
construction and building materials, 2001,
mixing and compaction temperatures in asphalt concrete.
16pp15-22.
Its effect on the viscosity of the binder guarantees an
efficient coating of the aggregate by the binder and a
[8] Y. Edwards, Y. Tasdemir, and U.Isacsson,
good workability of the asphalt mixture at lower
“Rheological Effects of Commercial Waxes and
temperatures compared to the conventional hot mix
Phosphoric Acid in Bitumen 160/220” High and
asphalt (HMA). Also the addition of S at low
Medium Tempera Performance” j Science and
temperature of 60 oC indicated an increase in viscosity as
Tech 2006, 45, 31-41.
the S% was increased. It is a wax, which recrystallizes in
the binder on cooling, thereby increasing the viscosity of
[9] X. Lu, and U. Isacsson, compatibility and storage
the binder at lower temperatures, this enhances the flow
stability of styrene-butadiene- Styrene copolymer
of the binder. Base on the penetration test conducted on
modified bitumen’s. J. of Materials and structures,
the 3% S modified binder could be categorized as PG76-
1997.
22.

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