Study of Low Temperature Performance of Different Asphalt Types
in Qinghai-Tibet Region
Xueyan Zhou
1a
, Xiao qing Wang
1b
and Yue Xiao
1c
1 Chang’an University, Xi’an , Shannxi, China
Keywords: Road engineering, low temperature bending strength, low temperature bending strain
Abstract: The climate conditions in Tibet are special, and the performance requirement of asphalt pavement is
different from that of general area. The study of asphalt pavement in this area is aimed at the secondary
roads. There is no experience for high grade asphalt pavement design .Based on the study of asphalt binder
and mixing materials in high altitude area，used low-temperature bend test, analysis the influence of
asphalt type on the low temperature performance of asphalt mixture. The results show that low temperature
anti-cracking performance of SBS/SBR composite modified asphalt mixture is optimal. It is suggested to
choose composite modified asphalt with high grade.
1 INTRODUCTION
The low temperature cracking of asphalt pavement is
a worldwide problem that has long been concerned
at home and abroad (Ma, 2011). Previous research
has shown that there are many factors influencing
low temperature cracking of asphalt pavement. It
mainly includes the properties of asphalt and asphalt
mixture, the properties of basic materials, climatic
conditions, traffic loads, design factors and
construction factors (Underwood, 2013).According
to the mechanism or main inducement of pavement
cracking, the crack in asphalt pavement is generally
divided into load crack and non-load crack. For
semi-rigid base asphalt pavement cracking and low
temperature cracking of asphalt pavement, non-load
crack is the main form (Sha, 2012).Non-load is
commonly transverse cracks, mainly is the low
temperature, cooling and temperature cycle
repeatedly on the asphalt pavement temperature
shrinkage crack and shrinkage cracking semi-rigid
base and the reflective crack (Li, 2008).
The Tibetan has high altitude, low annual
average temperature, big temperature difference,
frequent freeze-thaw cycle, strong solar radiation
and a variety of adverse conditions, which affects
the mechanical properties and durability of the
asphalt mixture significantly (Ma, 2015). Low
temperature crack seriously affects the service life of
road. However, in the Qinghai-Tibet plateau, the low
temperature crack has a more significant impact on
road life and pavement performance. The low
temperature performance evaluation index of asphalt
mixture is studied systematically by domestic and
foreign researchers. The American highway strategic
research program (SHRP) has proposed a
temperature stress test and J - integral test as the
main method to evaluate the low temperature
cracking of asphalt pavement (Iliuta, 2004).China
"five-year" project with 0 °C bending creep test of
asphalt mixture creep rate as the evaluation index of
asphalt mixture low temperature crack resistance
(Zhao, 2011). In the past, many researchers have
used low temperature bending strength or low
temperature bending strain as the evaluation index in
the study of low temperature crack resistance of
asphalt mixture (Wang, 2016).For the evaluation
method proposed by China "five-year" project,
because its experimental temperature is far from the
actual temperature in the Qinghai-Tibet plateau, it
should not be used to evaluate the low temperature
performance of asphalt mixture in this area.
However, the low temperature bending strength or
low temperature bending strain used by most
researchers can only reflect the characteristics of
asphalt mixture at low temperature, and cannot
comprehensively reflect its low temperature
performance (Chazono, 1989; Ho, 2002).Therefore,

there are many evaluation indexes for the low
temperature crack resistance of asphalt mixture, and
there is no uniform standard at home and abroad.
In this paper, according to the low temperature
bending test results of asphalt mixture in Qinghai-
Tibet alpine region, the effect of asphalt variety on
the crack resistance of asphalt materials was
analysed.
2 TEST MATERIALS
2.1 Materials
The asphalt used in this study was SBS90#modified
asphalt, SBS/SBR90#co-modified asphalt,SBR90#
modified asphalt, SBS110# modified asphalt,
SBS/SBR110# co-modified asphalt and SBR110#
modified asphalt, the corresponding serial number is
1#~6#. The specific technical indicators and test
results are shown in Table1.
Table1: Technical indicators of modified asphalt
Technical index
Experimental value
1# 2# 3# 4# 5# 6#
Penetration
(0.1mm)
96 96 93 107 102 109
Ductility (cm) 56 84 148 62 120 150
Softening point
(
℃
)
61.5 62.3 60.2 59.7 59.5 57.9
Kinematic
viscosity
(135
℃
)
1.49 2.73 2.94 1.23 2.53 2.87
Penetration index 3.04 4.29 3.46 2.25 3.33 2.77
Flash point (
℃
)
247 231 243 243 234 246
Solubility (%) 99.7 99.6 99.6 99.5 99.6 99. 6
RT
FO
T
Quality change
(%)
0.34 0.34 0.27 0.5 0.45 0.48
Residual
penetration
(%)
74.9 74.9 71.6 74.6 87.8 77.6
Residual
ductility
(cm)
65 65 98 48 88 113
The coarse aggregate was granite, fine aggregate
was artifical sand, mineral powder was limestone
mineral powder.
2.2 Test Methods
The bending test (T 0715-2011) of 《Standard Test
Methods of Bitumen and Bituminous Mixtures for
Highway Engineering》(JTG E20-2011) was used
to test the low-temperature performance of asphalt
mixture.
3 RESULTS AND DISCUSSIONS
3.1 Analysis of the Low Temperature
Bending Strength
The low temperature bending strengths of different
asphalt are shown in Figure 1.
1# 2# 3# 4# 5# 6#
0
1
2
3
12
13
14
15
Low temperature bending strength (MPa)
Aaphalt mixture
Figure 1Low temperature bending strength of asphalt
mixture .
As can be seen in Figure 1, all kinds of asphalt
mixture low temperature bending strength are high,
and the low temperature bending strength of
different asphalt types differs slightly. More
specifically, the low temperature bending strength of
SBS/SBR110# co-modified asphalt mixture is the
maximum, the corresponding value is 14.3 MPa, and
that of SBR90# modified asphalt mixture is the
minimum, the corresponding value is 12.1 MPa.
As for the asphalt mixture with the same
aggregate gradation and penetration grade, the low
temperature bending strength of composite modified
asphalt mixture is higher than that of the two other
asphaltmixtures, the low temperature bending
strength of SBS modified asphalt mixture and SBR
modified asphalt mixture are almost the same, and
the low temperature bending strength of SBR
modified asphalt mixture is a little bigger thanthat of
SBS modified asphalt mixture.
As for the same modified asphalt, with the
increasing of the penetration degree, the low
temperature bending strength of asphalt mixture
decreased.
From the low temperature bending strength index
of asphalt mixture, the composite modified asphalt
has the advantages of SBS modified asphalt and
SBR modified asphalt, and the low temperature

resistance of composite modified asphalt mixture is
the best.
3.2 Analysis of the Low Temperature
Bending Strain
The low temperature bending strains of different
asphalt are shown in Figure 2.
1# 2# 3# 4# 5# 6#
0
2500
3000
3500
4000
4500
Low temperature bending strain(10
-6
)
Asphalt mixture
Figure 2Low temperature bending strain of asphalt
mixture
In Figure 2, the low temperature bending strain
of all asphalt mixtures is greater than 3000, which
meet the specifications. It is different from low
temperature bending strength, there is a significant
difference between different asphalt mixture the low
temperature bending strain. Specifically speaking,
the low temperature bending strain of SBS/SBR110#
co-modified asphalt mixture is the maximum, the
corresponding value is 4017, and that of SBR90#
modified asphalt mixture is the minimum, the
corresponding value is 2751.
As for the asphalt mixture with the same
aggregate gradation and penetration grade, the low
temperature bending strain of SBR modified asphalt
mixture is the minimum, the low temperature
bending strain of SBS/SBR co-composited modified
asphalt mixture is the maximum, and the low
temperature bending strain of SBS modified asphalt
mixture is middle. The difference between low
temperature bending strain of SBS/SBR co-
composited modified asphalt mixture and SBR
modified asphalt mixture is significant, while the
difference between SBS/SBR co-composited
modified asphalt mixture and SBS modified asphalt
mixture is small.
As for the same modified asphalt, with the
increasing of the penetration degree, the low
temperature bending strength of asphalt mixture
increased, and the influence of penetration degree on
the low temperature bending strain of asphalt
mixture is significant.
From the low temperature bending strain index
of asphalt mixture, the low temperature resistance to
deformation of SBS/SBR co-composited modified
asphalt mixture is the best, the SBS modified asphalt
mixture is the second, and the SBR modified asphalt
mixture is the worst. Combined low temperature
bending tensile strength and bending strain of
asphalt mixture, the low temperature performance of
SBS/SBR co-composited modified asphalt mixture
is the optimum.
3.3 Analysis of the Low Temperature
Stiffness Modulus
1# 2# 3# 4# 5# 6#
0
3500
4000
4500
Low temperature stiffness modulus(MPa)
Asphalt mixture
Figure 3Low temperature stiffness modulus of asphalt
mixture
As can be seen from Figure 3, the low temperature
bending stiffness modulus of different asphalt
mixture is small. The low temperature bending
stiffness modulus of SBR90# is the maximum, the
corresponding value is 4398MPa, and that of the
SBS/SBR110# is the minimum, the corresponding
value is 3560MPa.
As for the asphalt mixture with the same
aggregate gradation and penetration grade, the low
temperature bending stiffness modulus of SBR
modified asphalt mixture is the maximum; the low
temperature bending stiffness modulus of SBS/SBR
co-composited modified asphalt mixture is the
minimum, and the low temperature bending stiffness
modulus of SBS modified asphalt mixture is middle.
As for the same modified asphalt, with the
increasing of the penetration degree, the low
temperature bending stiffness modulus of asphalt
mixture decreased.
The low temperature bending stiffness modulus
is a comprehensive performance of low temperature
strength and deformation resistance of asphalt

mixture, which reflect the flexibility of asphalt
mixture to some extent. Generally speaking, the
smaller the bending stiffness, flexible of asphalt
mixture under cold condition, the better.
In conclusion, the low temperature bending
strength and bending strain of SBS/SBR co-
composited modified asphalt mixture are both larger,
the low temperature stiffness modulus of SBS/SBR
co-composited modified asphalt mixture is smaller.
4 CONCLUSIONS
As for the low temperature bending strength of
asphalt mixture, the composite modified asphalt has
the advantages of SBS modified asphalt and SBR
modified asphalt, and the low temperature resistance
of composite modified asphalt mixture is the best;As
for the low temperature bending strain index of
asphalt mixture, the low temperature resistance to
deformation of SBS/SBR co-composited modified
asphalt mixture is the best, the SBS modified asphalt
mixture is the second, and the SBR modified asphalt
mixture is the worst; As for the low temperature
bending stiffness modulus of asphalt mixture, SBR
modified asphalt mixture is the worst; the low
temperature bending stiffness modulus of SBS/SBR
co-composited modified asphalt mixture is the
best.In a word, the low temperature performance of
SBS/SBR co-composited modified asphalt mixture
is optimum. In addition, high grade asphalt is
selected to improve the low temperature
performance of asphalt mixture.
ACKNOWLEDGEMENTS
This research was financially supported by the
Excellent Doctoral Dissertation Project of Chang’an
University (No. 310821175012).
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