International Journal of Current Engineering and Technology E-ISSN 2277 – 4106, P-ISSN 2347 – 5161

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Research Article

Longer Fatigue Life for Asphalt Pavement Using (SBS@Clay)

Nanocomposite
Farag Khodary†*
†Civil Engineering Department, Qena Faculty of Engineering, South Valley University, Qena, Egypt

Accepted 22 March 2015, Available online 02 April 2015, Vol.5, No.2 (April 2015)

Abstract

The conventional bitumen has a limited capacity under wide range of loads and temperature which occur over the
life of a pavement. Therefore, conventional bitumen needs to be modified to face the heavy loads and weather change.
Number of materials used to improve the properties of bitumen and asphalt properties such as polymers and rubber.
And with the considerable increase demand to get better properties of asphalt concrete mixtures nano scale material
ware used as asphalt modifier. One of the most important properties of nano scale material is surface to volume
ratio. The conventional bitumen used in this research was AC (60/70) penetration grade, modified with 5% styrene–
butadiene–styrene as well as nanoclay (nCL) at four different modification levels namely 2%, 4%, 6% and 8% by
weight of the bitumen. Morphology and structural of the prepared materials were investigated using spectroscopic
techniques such as Transmission electron microscope (TEM) and Scan electron microscope (SEM). Penetration and
softening point were used to evaluate the modified bitumen as well indirect tensile strength test and fatigue test were
carried out to characterize the properties modified and unmodified asphalt concrete mixtures. Based on the results, it
was found that using (SBS@Clay) nanocomposite improves both penetration and softening point of all modified
bitumen. Tensile strength for modified mixtures with 5% SBS and 6% nanoclay is higher than unmodified mixtures by
nearly three times. Fatigue life of (SBS@Clay) modified mixtures equals to 3.4 times higher than unmodified bitumen.
Keywords: Modified bitumen, Tensile strength, nano-clay, styrene–butadiene–styrene , fatigue , asphalt concrete
mixtures.

1. Introduction The right material amounts and compatibility for a

1 The question still exists: why do we need to improve suitable polymer-bitumen mix depend on several
the properties of Bitumen? Increased traffic loads and factors, of which the most important are the chemical
climate change is still a big challenge for researchers in compositions of the bitumen and polymer, and the
the asphalt road industry. Researches are trying to find manufacturing process. Most likely polymer used to
a new addition to improve the properties of bitumen modify bitumen is polyethylene, polypropylene and
and to have a clear impact in the performance of styrene-butadiene-styrene (SBS). Traditional test is not
asphalt roads. Physical and mechanical properties of enough to evaluate the properties of the modified
unmodified bitumen make it unable to withstand the produced bitumen. The engineering properties of
loads of traffic as well as climate change, so the modified bitumen are directly affected by the mixing
researchers tried to search for materials are added to proses polymer into bitumen. During the mixing proses
the bitumen to improve these properties. Last decade the structural and chemical compositions of both
using polymers to modify bitumen in asphalt concrete materials are changed. The mixing time affect the
pavement applications has been growing rapidly. Many compatibility between polymer and bitumen and it
types of polymer are used to improve the properties of should be determine carefully (Pérez-Lepe, et al,
the bitumen such as rubber, SBR and SBS. The
2003), (Burak, and Isikyakar, 2008), (Yetkin, 2007),
rheological properties of (SBS) modified bitumen were
studied and the result shows that at high temperature (Ronald, 1998).
real increase in the binder elasticity. On the other hand Three (SBS) polymer contents was added to base
addition of styrene-butadiene-styrene (SBS) to base bitumen and the properties of the resulting modified
bitumen improves the flexibility at low temperatures bitumen was evaluated by conventional as well as
(Morales, et al, 2006), (Xiaohu and Isacsson, 1997), dynamic shear rheometer (DSR). The resulting
(Bernard, 1996). modified bitumen is function of different factors
bitumen source, bitumen–polymer compatibility and
*Corresponding author: Farag Khodary polymer concentration. High aromatic bitumen plus
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Farag Khodary Longer Fatigue life for Asphalt Pavement Using (SBS@Clay) Nanocomposite

high polymer modification level lead to highly elastic aggregates. Crashed lime stone aggregate were used in
network for the modified bitumen. The highly elastic this study and the lime is used as filler. The properties
network increases the viscosity, complex modulus and of the used aggregates are shown in Table (1).
elastic response of the modified bitumen (Goh, et al,
2011), (Ghaffarpour, and Khodaii, 2009), (Gordon, Table 1 Aggregate properties
2003).
On the other hand, scientists found that the
addition of polymers to improve the properties of the
asphalt is enough to get satisfactory results in terms of
the performance of the road. These days, the use of
nanoscale materials has become a new addition to the
asphalt road industry. Clay can be modified using
nanotechnology to produce clay in nano scale which
will be compatible with organic monomers and 2.2 Bitumen
polymers. Using nanoclay as bitumen modifier improve
the tensile strength of the resulting modified asphalt A petroleum substance that has a high viscosity is
concrete mixtures (Jianying,, et al, 2007), (Shaopeng,, extracted by crude oil distillation process under
et al, 2009), (Zhanping,, et al, 2011). pressure and high temperatures up to 300 degrees
Clay/styrene–butadiene–styrene (SBS) modified Celsius. It has many types differ by liquidity and
concentration as well as the different degree of melting
bitumen composites have higher higher complex
modulus, lower phase angle than unmodified bitumen and freezing temperatures. Bitumen type affects the
properties of the produced asphalt concrete mixtures
(Mikula,, et al, 2003), (Shell Bitumen, 1991), In this work bitumen (60/70) penetration grade was
(Khodary, 2010). Nanoclay modified bitumen show used. The physical properties of the used bitumen are
better rheological properties compared to unmodified presented in table (2).
bitumen. The addition of 2% nanoclay to the
unmodified bitumen increase the dynamic shear
complex modulus (G*) value by 66%. CaO/Bitumen Table 2 Bitumen properties
and Ca(OH)2 Nanopaticles was found that can
improve stiffness properties of bitumen and asphalt
concrete mixtures (Mahdi,, et al, 2009), (Khodary,, et
al, 2014),
Pavement distress is considered complex topics as
several factors contribute to the pavement failure. At
high temperatures under traffic loading the asphalt is
not able to maintain the original shape of the
pavement, which leads to permanent deformation,
known as rutting at low temperatures the asphalt, gets 2.3 Styrene butadiene styrene (SBS)
brittle and tends to crack because the stiffer structure
is unable to relax the internal stresses (Finn,, et al, Styrene butadiene styrene (SBS) is assumed to be one
1997), (Yi-Chang,, et al, 2009).In this work 5% (SBS) of the most important asphalt additives. SBS polymer
modified bitumen was mixed with 4 modification level gives the modified binder the desired properties such
of Nanoclay namely 2%, 4%, 6% and 8%. The as elasticity, plasticity and elongation. Therefore using
rheological and mechanical properties of the resulting SBS-modified asphalt improves the adhesive property
blend were evaluated in terms of penetration, of the mixtures, fatigue resistance and rutting
softening point, static creep test and fatigue test. resistance. The physical properties of styrene
butadiene styrene (SBS) are presented in table (3).
2. Materials
Table 3 Physical properties of styrene butadiene
Different types of materials were used in this work to
styrene (SBS)
design asphalt concrete mixtures aggregate, bitumen,
styrene–butadiene–styrene and Nano- clay. The
mixture proportions determined in accordance with
the design limitation of the Egyptian specifications.

2.1 Aggregate

Aggregate generally accounts for 92 to 95 percent of

asphalt concrete mixtures. Aggregates are divided into
two types; coarse and fine aggregates. Coarse 2.4 Clay Nanoparticles
aggregates are portions that are retrained on a sieve of
2.36 mm while aggregates that are retrained on The X-ray fluorescence (XRF) technique is a proven
between 2.36mm and 75μm are considered as fine technique for material analysis in a broad range of
950| International Journal of Current Engineering and Technology, Vol.5, No.1 (Feb 2015)
Farag Khodary Longer Fatigue life for Asphalt Pavement Using (SBS@Clay) Nanocomposite

industries. In this work XRF is used to kV) with EDX detector unit attached to the system.
determine chemical composition of the used nano-caly. From figure (2) it is appear that the dimension of
Using this techniques help to understand the chemical nanoclay ranges between 1 nm and 200 nm. Smaller
reaction between the materials used in this study. Clay particle of nanoclay decrease the void ratio in asphalt
consists of Al2O3, SiO2, CaO, TiO2 and Fe2O3 in concrete mixtures which directly increase the
different proportions. SiO2 represents the highest resistance to permanent deformation.
chemical composition of clay. Table (4) and Figure (1)
presented the chemical composition of nano-caly. 3. Preparation of modified sample and asphalt
mixtures

To prepare the modified bitumen, firstly the bitumen is

heated alone to a 175oC. 5% of styrene butadiene
styrene (SBS) (by weight of the total bitumen content
in asphalt concrete mixtures) is added to the heated
bitumen to produce the required modified blend. The
modified blend is thoroughly mixed at 170 oC for 25
minute with a low shear mixer at a blending speed of
700 rpm.
Four modification level of nanoclay is added after
heating the bitumen with (SBS). The percentages of
nanoclay added to the modified bitumen are 2%, 4%, 6,
and 8% by weight of the total bitumen content in
asphalt concrete mixtures). After this step the modified
bitumen with (SBS@Clay) is ready to use in asphalt
mixtures.
Fig.1 Results of X-ray fluorescence test on used The aggregates were placed in an oven at 175 oC for
nanocaly 1 hour. After mixing aggregate and binder the mixture
was placed in the heated mold and the mixture was
Table 4 Chemical composition of nanoclay compacted with standard Marshall compaction
hammer on each side. Marshall-sized specimen of (2.5
in. height by 4 in. diameter) is fabricated. Marshall
specimen used for indirect tensile strength test as well
as fatigue test. The percentage of each asphalt concrete
mixtures component was present in table (5) according
to the Egyptian specification (4c).

Table 5 Gradation of aggregates and Filler for asphalt

concrete mixtures

4. Characterization of Bitumen and Asphalt

Concrete Mixtures
Different laboratory tests were conducted in this
research including Penetration Test, Softening Point,
indirect tensile test, fatigue test
Fig.2 Morphology and structural of the nanocaly
4.1 Penetration test
Morphology and structural of the nanocaly materials
were investigated by transmission electron microscopy Penetration that measure the strength of asphalt
(TEM, JEOL JEM-1230 with accelerating voltage of 120 expressed in the distance that standard needle pierced
951| International Journal of Current Engineering and Technology, Vol.5, No.1 (Feb 2015)
Farag Khodary Longer Fatigue life for Asphalt Pavement Using (SBS@Clay) Nanocomposite

vertically in the sample under certain conditions of 4.4 Fatigue test

loading, time and temperature (100 gram load time is 5
seconds and 25 ° C) to be unity (0.01 cm). A cylindrical specimen is subjected to a constant
The sample is heated to become liquid and then repetitive compressive load which acts parallel to and
placed in a template (template penetration) and then along the vertical diametric plane. Damage occurs in a
the sample placed in a water bath to completely specimen from dynamic repetitive loading that leads to
submerge the sample 25 degree Celsius The dish is fatigue failure of the specimen. The phenomenological
placed on the base device penetration is then adjust the approach was used to calculate fatigue life.
The fatigue life of a specimen is defined as the
needle and above fixed weight on the surface of the
number of load repetitions at which specimen fracture
sample Is accessing the necessary adjustment
occurs. Controlled stress at stress level of 50% of the
congruent needle penetration with image on the
static indirect tensile strength and at a frequency of 10
surface of the asphalt material, the spectrum using
HZ. Number of load cycles to the specimen failure is
flashlight Damocles of convenient place The index is
defined as fatigue life of asphalt concrete mixtures
set to zero Launches the needle to penetrate the
(Richard,, et al, 1997), (Tayebali,, et al, 1992),(Zhiming
asphalt material is measured by the distance
and Lytton, 2002).
penetrated the needle in the specified time (Akbar,
2003).
b
 1 
4.2 Softening point test N f  a   (2)
 t 
The softening point is useful in the classification of
bitumens and is indicative of the tendency of the Nf = Fatigue life (number of cycles to failure),
material to flow at elevated temperatures. usually  t = initial stress

soften of the Bitumen at not occur at any time or in a , b = Material coefficients, derived of fitting the data.
any temperature, if the higher temperature state of
matter asphalt changed gradually from a solid to a 5. Test result
softer and less viscous and most case smoother, and it
must make a softening test by way termed Set which 5.1 Penetration test result
can be compared to the results of the asphalt materials
among them (ASTM, 1998). Penetration test results illustrate the impact of using
(SBS@Clay) nanocomposite of the bituminous
4.3 Indirect tensile test resistance to penetration. The results show that adding
(SBS@Clay) nanocomposite clearly influences
Indirect tensile test is used to evaluate tensile strength penetration of the modified bitumen. By increasing the
of asphalt concrete mixtures. It is known that indirect penetration of modifier the resistance to penetration
tensile test is one of the most popular tests used to increased. The decrease in the value of the penetration
evaluate the tensile resistance of asphalt concrete assumed to be clear evidence of asphalt concrete
mixtures. The test performed by applying compressive pavement resistance to traffic loads as well as the
load on Marshall specimen acting parallel to and along permanent deformation. Improvement in penetration
the vertical diametric (Kennedy, 1977), (Christensen properties improve the directly the pavement
and Bonaquist, 2004) This loading configuration performance and this is one on the main goals of this
developed a relatively uniform tensile stress research looking for stronger asphalt concrete
perpendicular to the direction of the applied load and pavement. Good correlation was found between
along the vertical diametral plane. The horizontal penetration test rest and modification level. This result
tensile stress at the center of the test specimen was is promising result that can to be used in the future for
calculated from Equation (1). finding the optimum modifier content at the needed
penetration. Table (6) and Figure (3) present the result
2Pmax of penetration test.
t 
DH (1)
Table 6 Penetration test results
Where

t = Indirect Tensile Strength

Pmax = Maximum Load
H = Thickness of Specimen
D = Diameter of Specimen
952| International Journal of Current Engineering and Technology, Vol.5, No.1 (Feb 2015)
Farag Khodary Longer Fatigue life for Asphalt Pavement Using (SBS@Clay) Nanocomposite

Fig.5 Indirect tensile test results

Fig.3 Penetration test results
5.4 Fatigue test
5.2 Softening Point
Promising results have emerged after a fatigue test.
Figure (2) present the result of Softening Point. Using polymer with nano materialos improve extent
Improvement in the temperature required to soften the fatigue life of all modified mixtures. But the modified
modified bitumen is a clear proof of how the modified mixtures with 5% SBS and 6% nanoclay have the
asphalt concrete pavement can resist climate change. highest fatigue life. This result indirect tensile test
This is a positive impact on the behavior of asphalt coincided together with fatigue test results. The
interpretation of these results is the ability of polymer
roads, especially at high temperature.
materials to form strong network between aggregate
and bitumen. The polymer is characterized by its
ability to form with Bitumen high elastic materials
which can resist tension in asphalt concrete pavement.
If the produced mixtures can resist tension that means
this mixtures can resist cracks.

Fig.4 Softening point test results Fig.6 Deformation and number of cycles

5.3 indirect tensile test results

The use of (SBS@Clay) nanocomposite leads to a

significant improvement in tensile resistance of asphalt
mixtures. Improved tensile strength has direct effects
on resistance of asphalt pavement to cracks. With the
increase in resistance to cracks roads that means
longer life of the pavement. One of the most important
goals of the research to obtain improved asphalt mixes
using nanotechnology and has a high tensile strength.
It is clear from the results that this goal has been
achieved. Figure (5) presents the indirect tensile test Fig.6 Fatigue life for modified and unmodified asphalt
results. concrete mixtures
953| International Journal of Current Engineering and Technology, Vol.5, No.1 (Feb 2015)
Farag Khodary Longer Fatigue life for Asphalt Pavement Using (SBS@Clay) Nanocomposite

Conclusion The Shell bitumen handbook (1991). Shell Bitumen,

Mikula, R. J., et al. (2003 Characterization of bitumen properties
using microscopy and near infrared spectroscopy: processability
In this paper different tests were present to evaluate of oxidized or degraded ores.Journal of Canadian Petroleum
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asphalt concrete mixtures based on dissipated energy concept.
discussions the following conclusions are presented: Diss. TU Darmstadt.
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954| International Journal of Current Engineering and Technology, Vol.5, No.1 (Feb 2015)