sustainability
Article
Effect of Warm Mix Asphalt (WMA) Antistripping Agent on
Performance of Waste Engine Oil-Rejuvenated Asphalt Binders
and Mixtures
Ahmed Eltwati 1, * , Ramadhansyah Putra Jaya 2, * , Azman Mohamed 3 , Euniza Jusli 4 , Zaid Al-Saffar 5,6 ,
Mohd Rosli Hainin 3 and Mahmoud Enieb 7
1
2
3
4
5
6
7
*
Citation: Eltwati, A.; Putra Jaya, R.;
Mohamed, A.; Jusli, E.; Al-Saffar, Z.;
Hainin, M.R.; Enieb, M. Effect of
Warm Mix Asphalt (WMA)
Antistripping Agent on Performance
of Waste Engine Oil-Rejuvenated
Asphalt Binders and Mixtures.
Sustainability 2023, 15, 3807.
https://doi.org/10.3390/
su15043807
Received: 1 February 2023
Revised: 13 February 2023
Department of Civil Engineering, University of Benghazi, Benghazi 12345, Libya
Faculty of Civil Engineering Technology, Universiti Malaysia Pahang, Kuantan 26300, Malaysia
Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia
Faculty of Engineering & Quantity Surveying, INTI International University, Nilai 71800, Malaysia
Department of Construction Engineering and Projects Management, Al-Noor University College,
Nineveh 41012, Iraq
Building and Construction Engineering Department, Technical College of Mosul, Northern Technical
University, Mosul 41002, Iraq
Department of Civil Engineering, Assiut University, Assiut 71511, Egypt
Correspondence: ahmed.eltwati@bsu.edu.ly (A.E.); ramadhansyah@ump.edu.my (R.P.J.)
Abstract: Evaluating the performance of rejuvenated asphalt mixes is crucial for pavement design
and construction, as using a rejuvenator not only boosts recycling and contributes to positive effects
on the environment but also increases the sensitivity to rutting and moisture. This study was executed
to evaluate the effect of a warm mix asphalt (WMA) antistripping agent, namely nano-ZycoTherm,
on the moisture-induced damage and rutting potential of asphalt mixtures containing 30% and
60% aged (RAP) binder and rejuvenated with 12% waste engine oil (WEO). For this purpose, the
rutting resistance of asphalt mixes in wet and dry conditions was examined utilizing a loaded wheel
tracker. In addition, the impacts of moisture on the performance of the mixtures were evaluated
using different experiments, such as modified Lottman (AASHTO T283), resilient modulus, dynamic
creep, aggregate coating and wheel tracking tests. Fourier transform infrared (FTIR) spectroscopy
and thermogravimetric (TG) analysis were performed to identify the functional groups, which would
be significant in terms of moisture damage, and to assess the thermal stability of binder samples,
respectively. The results revealed that the rejuvenation of aged binder with WEO increases the
moisture susceptibility of the mixtures; however, the addition of ZycoTherm was found to enhance
the moisture resistance of WEO-rejuvenated mixtures. Furthermore, the results indicated that the
WEO-rejuvenated mixtures modified with ZycoTherm exhibited a better rutting resistance in a
wet condition compared to that of WEO-rejuvenated and conventional HMA mixtures. However,
the rejuvenated mixtures modified with ZycoTherm showed poorer rutting performance in a dry
condition. In summary, the adoption of the WMA antistripping agent, RAP binder and WEO
rejuvenation techniques demonstrated satisfactory outcomes in terms of rutting resistance and
moisture susceptibility, and also, these techniques are much less expensive to implement.
Accepted: 17 February 2023
Published: 20 February 2023
Keywords: aged asphalt; antistripping additive; moisture susceptibility; RAP; warm mix asphalt;
ZycoTherm
Copyright: © 2023 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1. Introduction
Currently, the construction and maintenance of pavements adhere to the philosophy of
sustainable development, which helps reduce resource reliance and energy usage [1]. From
the sustainable perspective, the environmental impacts, economic benefits and performance
of the pavement must be critically considered. The combination of waste materials in
asphalt mixtures tackles three environmental issues, which are solid waste management,
Sustainability 2023, 15, 3807. https://doi.org/10.3390/su15043807
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Sustainability 2023, 15, 3807
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air pollution and global warming. Recycled asphalt pavement (RAP) has substantial
socio-economic advantages and may address the issues of environmental deterioration,
coarse aggregates, asphalt depletion, operating cost and maintenance effectiveness [2].
Currently, most US states only permit RAP to account for between 15 and 40 % of the
total mix design [3]. This is because using a huge amount of aged binder causes the mix
to age prematurely and crack at low temperatures. During the lifespan of the pavement,
oxidation alters the chemical configuration of the binder by loosening the maltenes and
raising the ratio of asphaltenes to maltenes, which results in a stiffening of the binder [4].
However, several studies have evaluated the inclusion of greater dosages of RAP with
recycling agents and found promising outcomes, i.e., improving resistance to cracking at
a lower temperature [5,6]. The efficiency of the recycling agent in reducing the viscosity
of an aged binder and restoring its rheological characteristics can be an indication of
its effectiveness [7]. Rejuvenators could be petroleum-based, bio-based, waste-cookingor industrial-oil-based, or based on specially created additives from various sources of
oil [8,9]. These rejuvenators can restore the asphaltenes/maltenes ratio in the asphalt binder,
reducing the hardening impact of the old binder [10].
Nonetheless, rejuvenators from distinct sources may have a variable degree of efficiency in increasing the performance of the mixes. For instance, waste engine oil (WEO),
which shares many molecular properties with asphalt, could be utilized as a rejuvenator
for aged asphalt. Engine oil’s characteristics degrade with continued usage over time,
and if it is not disposed of properly, it poses a threat to both the environment and human
health. Due to the demand from the economy and environment to properly manage waste,
the interest in reusing WEO has increased [11]. Several researchers have looked into the
idea of employing WEO to rejuvenate the characteristics of aged asphalt binders [12]. The
studies found that adding waste oil to RAP asphalt improved the workability and lowered
the mixing temperature. Moreover, the insertion of WEO enhanced the low-temperature
cracking resistance. According to Shoukat and Yoo [13], WEO improves asphalt’s resistance
to thermal cracking. However, Al-Saffar, et al. [14] revealed that WEO decreased the rutting
performance; this is due to the decreased cohesive and adhesive bond of the aggregate–
binder, especially at high temperatures. A study was conducted to estimate the potential of
WEO as a rejuvenator and suggested that WEO can be used to restore the characteristics of
aged asphalt binders; however, it was also observed that WEO had a negative impact on the
aggregate–binder bond, necessitating the application of antistripping agents [15]. Another
study [16] found that WEO harms asphalt characteristics, such as decreased adhesiveness to
aggregates, which contributed to stripping and raveling. Jia, et al. [17] also recommended
against using WEO in asphalt due to the detrimental impact on the fatigue properties of
the binder. Jahanbakhsh, et al. [18] found that the moisture susceptibility of RAP mixtures
increased after adding WEO into blended binders containing 60% RAP. Further, Eltwati,
et al. [19] developed asphalt mixtures containing 60%, 70% and 80% RAP binders with
different dosages of WEO (6%, 9%, 12%) and glass fibers. The results revealed that the application of WEO decreased the resistance of the rejuvenated mixtures to moisture damage
compared to virgin mixtures, and it was also shown that increasing the WEO content in
the RAP binder made the mixture more susceptible to stripping. Despite the numerous
benefits provided by WEO rejuvenation processes, they may have a detrimental effect on
the resistance to moisture damage and rutting of asphalt mixtures due to wet aggregates
and the lack of electrical and chemical tendency between the aged binder and aggregate
exterior due to low production temperatures.
Even though the precise cause of moisture degradation is not entirely established, the
characteristics of the aggregate and binder, the degree of compaction and the dynamic
impacts of passing vehicles all have a substantial impact on moisture-induced damage [20].
One of the most frequent methods for preventing or delaying the development of moisture
damage is to improve the characteristics of the aggregates [21]. On the other hand, the
asphalt binder has a substantial impact on the mix’s moisture characteristics [22,23]. It is
known that the adhesion between aggregates and binders can be improved by using either
Sustainability 2023, 15, 3807
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solid or liquid antistripping additives, whereby liquid substances are more frequent. Liquid
antistripping additives have been used since the 1930s, but they have poor durability when
subjected to high temperatures. Mirzababaei [24] examined the influence of warm mix
asphalt (WMA) antistripping additive, i.e., ZycoTherm, on the moisture sensitivity of hot
mix asphalt (HMA) and WMA mixes. It was noted that the influence of ZycoTherm on
antistripping attributes is better in WMA mixes than in HMA mixes. In addition, WMA is
a well-known green pavement. Thus, if combined with RAP, it gives added value to the
overall production cost and environmental impact, as it reduces fuel consumption during
the production phase [25]. Ayazi, et al. [26] used ZycoTherm as a warm mix additive for an
asphalt mixture containing RAP material. The findings revealed that ZycoTherm can raise
the mixes’ resilient modulus ratio (MRR) and tensile strength ratio (TSR), indicating an
improvement in moisture resistance. Sukhija, et al. [27] found that the use of antistripping
additives can enhance the stripping resistance of rejuvenated binders. Further, Yousefi,
et al. [28] assessed the moisture resistance of asphalt mixtures containing the RAP binder,
ZycoTherm, and different types of rejuvenators (aromatic extract and tall oil). The study
found that the rejuvenators could decrease the moisture susceptibility and rutting resistance
of asphalt mixtures containing RAP; however, the addition of ZycoTherm enhanced their
resistance to rutting and moisture damage.
Although WMA mixes incorporating RAP have a desirable economic and environmental impact, designing such mixes presents some difficulties. Furthermore, there have been
few research works on the influence of using WEO, RAP and WMA antistripping additives
at the same time on the mechanical performance of asphalt mixes. Therefore, the current
study was conducted to examine the effects of an antistripping agent, i.e., nano-ZycoTherm,
on the properties of asphalt mixtures incorporating WEO-rejuvenated binders. Water
damage assessment test procedures, such as indirect tensile strength (modified Lottman),
resilient modulus, dynamic creep, Marshall stability and aggregate coating tests, have
been used. The post-compaction (PC), stripping inflection point (SIP) and rutting depth
in wet and dry conditions as a consequence of loading cycles and final cycles for 20 mm
rutting depth parameters obtained from the wheel track test were used to assess the performance of rutting resistance and moisture susceptibility of the WEO-rejuvenated samples
containing WMA additive, i.e., ZycoTherm, and WEO-rejuvenated HMA samples. FTIR
was performed on binders to further examine and assess the factors affecting the stripping
of the mixtures. It was also postulated that failure of the samples due to water damage was
simply a result of the cohesive and adhesive bonds formed between the binders (RAP and
virgin binder) and the aggregate.
2. Materials, Sample Preparation and Methods
2.1. Materials
2.1.1. Virgin Asphalt Binder and Aggregate
The binder utilized in this experiment had a penetration grade of 60/70, a widely used
binder for pavement construction in several countries. The asphalt binder was obtained
from a local supplier, and its attributes are revealed in Table 1. The virgin aggregate
employed in this investigation was limestone aggregate, with a nominal maximum size of
19 mm.
Table 1. Properties of RAP and virgin binders.
Property
◦ C,
Penetration (25
10 g, 5 s)
Softening point (R&B)
Ductility (25 ◦ C, 5 cm/mm)
Kinematic viscosity (135 ◦ C)
Specific gravity
Units
Base Binder
Aged Binder
Standard
0.1 mm
◦C
cm
Pa.s
-
67
50.5
117
0.51
1.02
20.1
66.80
9.30
3.52
1.10
ASTM-D5
ASTM-D36
ASTM-D113
ASTM-D4402
ASTM-D70
Property
Penetration (25 °C, 10 g, 5 s)
Softening point (R&B)
Ductility (25 °C, 5 cm/mm)
Sustainability
2023,
15, 3807 (135 °C)
Kinematic
viscosity
Specific gravity
Units
0.1 mm
°C
cm
Pa.s
-
Base Binder
67
50.5
117
0.51
1.02
Aged Binder
20.1
66.80
9.30
3.52
1.10
Standard
ASTM-D5
ASTM-D36
ASTM-D113
4 of 27
ASTM-D4402
ASTM-D70
2.1.2. Waste
WasteEngine
EngineOil
Oil(WEO)
(WEO)and
andAntistripping
AntistrippingAdditive
Additive
2.1.2.
The WEO
WEO used
used isis aa4000
4000km
kmuse
use10W40
10W40synthetic
syntheticoil.
oil. The
The WEO
WEO has
has aa flash
flash point
point of
of
The
265◦°C
(ASTM-D92)and
andkinematic
kinematicviscosity
viscosityof
of41.0
41.0cSt
cSt(ASTM-D4402)
(ASTM-D4402)at
at135
135◦°C.
265
C (ASTM-D92)
C.
ZycoTherm
asas
a warming
blend,
antistripping
additive
ZycoThermhas
hasbeen
beenapproved
approvedworldwide
worldwide
a warming
blend,
antistripping
additechnology,
and itand
reduces
moisture
damage
by creating
permanent
chemical
bonds.
Zytive technology,
it reduces
moisture
damage
by creating
permanent
chemical
bonds.
coTherm,
a nano-organosilane
produced
byby
Zydex
Commerce,
ZycoTherm,
a nano-organosilane
produced
Zydex
Commerce,was
waschosen
chosenas
asaawetting
wetting
agent.
agent. ItIt has
has been
been established
established that
that ZycoTherm
ZycoTherm is
is safe
safe at
at standard
standard pressures
pressures and
and temperatemperatures
[29].
The
ZycoTherm
additive
has
a
viscosity
of
400
centipoises
and
a
flash
tures [29]. The ZycoTherm additive has a viscosity of 400 centipoises and a flash point
point of
of
◦
90
C. Figure
90 °C.
Figure 11shows
showsthe
theZycoTherm
ZycoThermused
usedin
inthis
thisstudy.
study.
Figure1.1.ZycoTherm
ZycoThermadditive.
additive.
Figure
2.1.3.
2.1.3. Recycled
Recycled Asphalt
Asphalt Pavement
Pavement(RAP)
(RAP)
The
The RAP
RAP material
material was
was collected
collected from
from aa milled
milled 12-year-old
12-year-old roadway.
roadway. To
Torecover
recover the
the
aged
binder
from
RAP
materials,
a
centrifugal
extraction
technique
with
methylene
chloride
aged binder from RAP materials, a centrifugal extraction technique with methylene chloas
a flush
was performed
as stated
in ASTM
D2172.
Subsequently,
the aged
binder
was
ride
as a flush
was performed
as stated
in ASTM
D2172.
Subsequently,
the aged
binder
recovered
usingusing
a rotary
evaporator
in accordance
with
ASTM
D5404
was recovered
a rotary
evaporator
in accordance
with
ASTM
D5404totoeliminate
eliminatethe
the
methylene
methylene chloride.
chloride. The
The original
original asphalt
asphalt mixture
mixture used
used to
to produce
produce this
this asphalt
asphalt includes
includes
siliceous
siliceous aggregates
aggregates and
and 60/70
60/70 penetration
penetration grade
grade binder.
binder. The
The binder
binder percentage
percentage of
of the
the
RAP
material
was
estimated
to
be
4.85%
based
on
the
ignition
experiment
(ASTM
D6307).
RAP material was estimated to be 4.85% based on the ignition experiment (ASTM D6307).
Table
Table11displays
displaysthe
thephysical
physicalproperties
propertiesofofthe
theRAP
RAPbinder.
binder.
2.2. Sample Preparation
2.2. Sample Preparation
The RAP (aged binder) with varying proportions, specifically 30% and 60%, was
The RAP (aged binder) with varying proportions, specifically 30% and 60%, was
heated up to 145 ◦ C before being combined with the virgin binder (70% and 40%). Then,
heated up to 145 °C before being combined with the virgin binder (70% and 40%). Then,
the WEO was immediately admixed with the blended binders for 60 ± 5 s. Afterward,
the WEO was immediately admixed with the blended binders for 60 ± 5 s. Afterward,
ZycoTherm with a content of 0.1% (by weight of total binder) was added to the rejuvenated
ZycoTherm with a content of 0.1% (by weight of total binder) was added to the rejuvebinders [30]. The penetration (ASTM-D5-20) [31] and softening point (ASTM-D36-14) [32]
nated binders [30]. The penetration (ASTM-D5-20) [31] and softening point (ASTM-D36tests were carried out to ascertain the appropriate WEO percentage, which recovers the
characteristics of the aged asphalt binder.
The reference asphalt mixture and mixtures containing 30% and 60% RAP binders
were produced using coarse aggregates of crushed dolomite, fine aggregates of siliceous
sand and a mineral filler of limestone dust. Table 2 lists the various asphalt mixtures tested
in this study and their designations. The aggregate of a nominal maximum size of 19 mm
was used in this study, and Figure 2 shows the gradation and the specified limitations of
the aggregates. The reference and RAP mixtures (30R and 60R) were prepared according
to Table 3. The mixture was thereafter given time to cool to the compaction temperature,
which was fixed at 280 ± 30 cSt. The mixture was then placed into a steel mold and
compacted using 75 blows per side to form Marshall samples, which met the standard’s
Sustainability 2023, 15, 3807
Sustainability 2023, 15, x FOR PEER REVIEW
5 of 27
5 of 27
requirements for height and radius of 63.50 mm and 50.80 mm, respectively. Based on the
14)
[32] tests
were carried
out
to ascertain
the
WEO percentage,
which
recov-of
Marshall
method,
a design
asphalt
content
ofappropriate
5.0% was selected
with an air void
content
ers
theFigure
characteristics
of the
aged asphalt
binder.followed in this study.
4%.
3 shows the
experimental
flowchart
The reference asphalt mixture and mixtures containing 30% and 60% RAP binders
Tableproduced
2. Asphaltusing
mixtures
tested
in the study.
were
coarse
aggregates
of crushed dolomite, fine aggregates of siliceous
sand and a mineral filler of limestone dust. Table 2 lists the various asphalt mixtures tested
Mixture ID
Type of Binder
in this study and their designations. The aggregate of a nominal maximum size of 19 mm
HMA
Hot
mix asphalt
mixture
containingand
virgin
(VA) and
aggregate
was
used in this study, and
Figure
2 shows
the gradation
thebinder
specified
limitations
of
30R
HMA containing 30% RAP
the aggregates. The reference and RAP mixtures (30R and 60R) were prepared according
30R+WEO
12%WEO Rejuvenated HMA containing 30% RAP
to Table 3. The mixture was
thereafter given time to cool to the compaction temperature,
12%WEO Rejuvenated HMA containing 30% RAP and 0.1%
WMA-30R-WEO
which
was fixed at 280 ± 30
cSt.
The mixture was then placed into a steel mold and comZycoTherm
pacted
using
75
blows
per
side
to
form Marshall
60R
HMA containing
30% RAP samples, which met the standard’s re60R+WEO
12%WEO
Rejuvenated
containing
RAP
quirements for height and radius of 63.50 mm HMA
and 50.80
mm, 60%
respectively.
Based on the
12%WEO
Rejuvenated
HMA
containing
60%
RAPan
and
Marshall
method, a design asphalt content of 5.0% was selected with
air0.1%
void content
WMA-60R-WEO
of 4%. Figure 3 shows the ZycoTherm
experimental flowchart followed in this study.
100
90
Passing %
80
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
Sieve Size (mm)
Upper limit
Lower limit
Aggregate grading
Figure2.2.Gradation
Gradationofofthe
theaggregate
aggregateand
andspecification.
specification.
Figure
Table2.3.Asphalt
Mixturemixtures
content for
Marshall
Table
tested
in the sample.
study.
Mixture ID
HMA
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
WMA-60R-WEO
Weight of Different Mixes’ Content (grams)
Type of Binder
Mixture ID
Hot mix asphalt mixture containing
binder
and aggregate
RAP virgin
Fresh
Agg. (VA) Fresh
Bit.
WEO
ZycoTherm
HMA containing
30% RAP
HMA
–
1140
60
–
–
12%WEO
30%
RAP
30RRejuvenated HMA containing
360
798
42
–
–
30R+WEO
360
798
–
12%WEO
Rejuvenated HMA containing
30%
RAP and 0.1%42ZycoTherm 2.16
WMA-30R-WEO
360
798
42
2.16
0.06
HMA containing 30% RAP
60R
720
456
24
–
–
12%WEO
Rejuvenated HMA containing
60%
RAP
60R+WEO
720
456
24
4.32
–
12%WEO
Rejuvenated HMA containing
60%
RAP and 0.1%24ZycoTherm 4.32
WMA-60R-WEO
720
456
0.06
Table 3. Mixture content for Marshall sample.
Mixture ID
HMA
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
RAP
-360
360
360
720
720
Weight of Different Mixes’ Content (grams)
Fresh Agg.
Fresh Bit.
WEO
ZycoTherm
1140
60
--798
42
--798
42
2.16
-798
42
2.16
0.06
456
24
--456
24
4.32
--
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Sustainability 2023, 15, 3807
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WMA-60R-WEO
720
456
24
4.32
0.06
Figure
Figure 3.
3. Flowchart
Flowchart of
of the
the study.
study.
2.3.
2.3. Testing
TestingMethods
Methods
2.3.1. Fourier Transform Infrared (FTIR) Spectroscopy
2.3.1. Fourier Transform Infrared (FTIR) Spectroscopy
FTIR spectroscopy was employed to examine and provide a comprehensive grasp of
FTIR spectroscopy was employed to examine and provide a comprehensive grasp of
the functional categorizations of binders. A total of 32 scans were performed on virgin and
the functional categorizations of binders. A total of 32 scans
were performed on virgin
rejuvenated binders, with 5% iris and a resolution of 4 cm−1 −1at wave numbers varying
and rejuvenated binders,
with
5%
iris
and
a
resolution
of
4
cm
at wave numbers varying
from 4000 to 400 cm−−11 . The carboxylic acids in the binder have a significant influence on
from 4000 to 400 cm . The carboxylic acids in the binder have a significant influence on
stripping, particularly when combined with siliceous particles, resulting in absorbance
stripping, particularly when combined with siliceous
particles, resulting in absorbance
−1 . This
peaks of interest spanning from 1710 to 1690 cm
area is commonly utilized to
peaks of interest spanning from 1710 to 1690 cm−1. This area is commonly utilized to charcharacterize asphalt binders, and the findings of functional groups, i.e., carboxylic acids,
acterize asphalt binders, and the findings of functional groups, i.e., carboxylic acids, 22-quinolones, anhydrides and ketones, may be important in terms of moisture damage [26].
quinolones, anhydrides and ketones, may be important in terms of moisture damage [26].
2.3.2. Thermogravimetric (TG) Analysis
2.3.2. Thermogravimetric (TG) Analysis
TG analysis is a technique, which ascertains the mass loss of material as a function
TG analysis is
a technique,
which ascertains
the mass
loss ofE1131
material
of
of temperature.
The
test was performed
according
to ASTM
[33]asina function
a nitrogen
temperature. with
The test
was performed
according
E1131 [33] of
in 10
a nitrogen
environment
a sample
mass of about
5 mg to
at ASTM
a flow frequency
mL/min;envithe
◦ C at a heating
ronment withwas
a sample
mass increased
of about 5from
mg at40
a flow
frequency
of 10 mL/min;
the◦tempertemperature
constantly
to 800
rate of 10
C/min.
aturetest
wassample
constantly
from
40 to 800 °C
at a heating rate of 10 °C/min. Each test
Each
was increased
enclosed in
an aluminum
pan.
sample was enclosed in an aluminum pan.
2.3.3. Marshall Stability and Flow Test
2.3.3.The
Marshall
Stability
Test
maximum
load and
that Flow
asphalt
mixes can sustain before failure is determined by the
stability
flow test.
wascan
conducted
according
toisASTM
D6927.byThe
Theand
maximum
loadThe
thatexperiment
asphalt mixes
sustain before
failure
determined
the
◦ C. The
Marshall
samples
underwent
a
30
min
conditioning
period
in
a
water
bath
set
at
60
stability and flow test. The experiment was conducted according to ASTM D6927. The
Marshall
then subjected
loading at a constant
of 50bath
mm/min,
while
Marshall samples
sampleswere
underwent
a 30 mintoconditioning
period inpace
a water
set at 60
°C.
the deformation patterns were measured until the entire failure occurred.
Sustainability 2023, 15, 3807
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2.3.4. Indirect Tensile Strength (ITS) Test
The tensile strength of mixtures is an essential property, which illustrates the adhesion
and cohesion characteristics of the aggregate–binder interaction, resulting in improved
resistance to tensile strength in the pavement. The resistance of the mixes to moisture
damage was investigated using the AASHTO T283 standard [34]. A tensile force with a
continuous deformation pace of 5.1 cm/min at 25 ◦ C was applied according to AASHTO
T322 [35] to attain the ITS.
The tensile strength ratio (TSR) denotes a decrease in mixture integrity caused by
moisture degradation and is computed by dividing the tensile strength of the conditioned
sample by the unconditioned sample. A minimum ratio of 80% has often been employed
as a failure criterion for the TSR.
2.3.5. Resilient Modulus (MR ) Test
The resilient modulus test was carried out as specified in ASTM D7369 [36]. Five
conditioned and five unconditioned specimens with repetition for each kind of specimen
were tested at 25 ◦ C. This test evaluates the mixture’s resistance to irreversible deformation
as well as its capacity to recover to its original state after being subjected to a 1000 kN load.
An estimation of the mix’s reaction to the impact of moisture is given by the proportion of
the resilient modulus of the conditioned samples to the unconditioned samples. Since the
resilient modulus test is non-destructive, it is appropriate for assessing the damage caused
by moisture in the mix.
The resilient modulus ratio (RMR) is a parameter used to determine the moisture
resistance of the mixture using the resilient modulus test. A mixture with a higher RMR is
more resistant to moisture damage. An RMR of 70% is commonly used as the lowest value
required for HMA mixes [37]. The mixes’ RMR values are calculated as follows:
RMR =
MR (wet)
MR (dry)
(1)
2.3.6. Dynamic Creep Test
Rutting has become a major challenge in the development of WMA technology as a
result of the WMA’s reduced stiffness. When the pavement is exposed to moisture, the
problem worsens. The rutting resistance of the WMA mixes comprising RAP was examined
using a dynamic creep test for unconditioned and conditioned samples at 50 ◦ C. The testing
was carried out using the universal testing machine (UTM) in line with NCHRP 9-19 [38].
The cumulative permanent vertical stresses were measured under haversine compressive
loading with a deviator stress level of 450 kPa. After a certain number of cycles, the slope
tangent of the permanent strain versus loading cycle curve, which is known as the flow
number (FN), intensified substantially. The FN was determined for both conditioned and
unconditioned samples, and the creep ratio (CR) value (see Equation (2)) was utilized as an
indicator to assess the influence of moisture on the rutting. Mixtures with higher values of
CR are less susceptible to moisture.
CR =
Flow number (wet)
Flow number (dry)
(2)
2.3.7. Aggregate Coating Test
The aggregate coating test was carried out according to AASHTO T195 [39]. The
coating was only determined for particles that remained on the 9.5 mm sieve. As a result,
the aggregates were filtrated on a 3/8” sieve, and roughly 500 gm of the sieved specimen
was obtained and analyzed. According to the design requirement, at least 95% of the coarse
aggregate particles must be completely coated.
obtained and analyzed. According to the design requirement, at least 95% of the coarse
aggregate particles must be completely coated.
Sustainability 2023, 15, 3807
8 of 27
2.3.8. Rutting Resistance Test
The rutting resistance of the asphalt mixtures was determined using a double-wheel
2.3.8.
Rutting
tracker
(EN Resistance
12697-22 ).Test
The mixtures were submersed in hot water for 30 min at 50 °C.
Subsequently,
the
samples
exposed
to numerous
loadings passes
705.0 N at 53.0
The rutting resistance of were
the asphalt
mixtures
was determined
using of
a double-wheel
◦ C. a
passes/min.
The
test
is
run
until
the
loaded
wheel
has
completed
20,000
passes,
tracker (EN 12697-22). The mixtures were submersed in hot water for 30 min ator50until
20 mm rut depth
developed,
whichever
first. loadings passes of 705.0 N at
Subsequently,
the has
samples
were exposed
to comes
numerous
53.0 passes/min. The test is run until the loaded wheel has completed 20,000 passes,
Results
or3.until
a 20 and
mm Discussion
rut depth has developed, whichever comes first.
3.1. Physical and Chemical Evaluations of Asphalt Binder Samples
3. Results and Discussion
3.1.1. Penetration and Softening Point
3.1. Physical and Chemical Evaluations of Asphalt Binder Samples
Figures 4 and
depict thePoint
influence of different contents of WEO on the penetration
3.1.1. Penetration
and5 Softening
and softening point of RAP binders incorporating ZycoTherm. The addition of a RAP
Figures 4 and 5 depict the influence of different contents of WEO on the penetration
binder, as predicted, greatly lowered the penetration and raised the softening point of the
and softening point of RAP binders incorporating ZycoTherm. The addition of a RAP
virgin binder. The findings also showed that the increase in WEO content led to an inbinder, as predicted, greatly lowered the penetration and raised the softening point of the
crease
in penetration
andalso
a decrease
in the
the RAP
It was
virgin
binder.
The findings
showed that
thesoftening
increase inpoint
WEOofcontent
led binders.
to an increase
noted
that
blending
12%
of
WEO
(by
weight
of
aged
binder)
with
30%
and
60%
RAP
bindin penetration and a decrease in the softening point of the RAP binders. It was noted
ers
restored
the
penetration
and
softening
point
of
blended
binders
to
the
value
of
the
that blending 12% of WEO (by weight of aged binder) with 30% and 60% RAP binders
virgin
asphalt
(VA).
The
recovery
tendency
was
relatively
similar
under
various
dosages
restored the penetration and softening point of blended binders to the value of the virgin
of WEO,
implying
that asphalt
efficiency
was restored
accordingly.
indicates
that
asphalt
(VA).
The recovery
tendency
was relatively
similar under
various This
dosages
of WEO,
adding WEO
boosted
the aromatic
percentage
of aged asphalt
[40]. Previous
studies
recimplying
that asphalt
efficiency
was restored
accordingly.
This indicates
that adding
WEO
ommended
that
9
to
12%
WEO
content
could
recover
the
physical
properties
of
asphalt
boosted the aromatic percentage of aged asphalt [40]. Previous studies recommended that
binders
containing
high content
RAP
[19,41].
Wang, etofal.asphalt
[15] indicated
the mix9 to
12% WEO
contenta could
recoverofthe
physical
properties
binders that
containing
ing
of
WEO
has
both
positive
and
negative
impacts.
The
optimal
dosage
of
WEO
depends
a high content of RAP [19,41]. Wang, et al. [15] indicated that the mixing of WEO has
on positive
the stiffness
of agedThe
binders.
It is
known
WEO
is used
to restore
the
both
and properties
negative impacts.
optimal
dosage
of that
WEO
depends
on the
stiffness
RAP binder
to itsbinders.
original state
by reducing
its viscosity
increasing
its ductility.
properties
of aged
It is known
that WEO
is used and
to restore
the RAP
binder toHowits
ever, astate
higher
dosage of
may
not
be moreits
suitable
forHowever,
high-temperature
perfororiginal
by reducing
its WEO
viscosity
and
increasing
ductility.
a higher dosage
asphalt
than that
low temperatureperformance
due to the reduction
in adhesion
ofmance
WEO may
notpavement
be more suitable
forfor
high-temperature
asphalt pavement
between
the
binder
and
the
aggregate.
Thus,
a
moderate
amount
of
antistripping
additive
than that for low temperature due to the reduction in adhesion between the binder and
the
is
required
to
control
the
required
properties
and
to
improve
the
adhesion
between
the
aggregate. Thus, a moderate amount of antistripping additive is required to control the
binder and
the aggregate.
required
properties
and to improve the adhesion between the binder and the aggregate.
70
80
a
65.6
64
60
60
53
50
40
30
20
36.3
Penetration (0.1 mm)
Penetration (0.1 mm)
80
70
b
65.6
63.5
60
52
50
41.3
40
32
30
20
Figure
4. 4.Penetration
asphalt mixtures
mixturescontaining
containing(a)
(a)30%
30%RAP
RAP
binder
Figure
Penetration values
values of asphalt
binder
andand
(b) (b)
60%60%
RAP
RAP
binder.
binder.
Sustainability
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15,
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PEERPEER
REVIEW
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15,x3807
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2023,
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REVIEW
52 51
50
50
48
48
46
46
44
44
a
52.5 52.5
51
50.5 50.5
48.5 48.5
48
48
56
56
54
54
53.5 53.5
52
52 51
50
50
48
48
46
46
44
44
b
b
51.5 51.5
51
49.5 49.5
48.75 48.75
Figure
5.5.Softening
point
values
ofofasphalt
mixtures
containing
(a)
RAP
binder
and
(b)
Figure
Softening
point
values
asphalt
mixtures
containing
(a)30%
30%30%
RAP
binder
andand
(b)60%
60%60%
Figure
5. Softening
point
values
of asphalt
mixtures
containing
(a)
RAP
binder
(b)
RAP
binder.
RAP
binder.
RAP binder.
3.1.2.
FTIR
Results
3.1.2.
FTIR
Results
3.1.2.
FTIR
Results
Figures
6
and
7 show
thethe
master
curves
of infrared
spectroscopy
examination
of ZyFigures
6
7 show
curves
of
spectroscopy
examination
Figuresand
6 and
7 show
themaster
master
curves
of infrared
infrared
spectroscopy
examination
ofofZycoTherm-modified
and
WEO-rejuvenated
binders
containing
30%
and
60%
RAP
binders,
ZycoTherm-modified
and
WEO-rejuvenated
binders
containing
30%
and
60%
RAP
binders,
coTherm-modified and WEO-rejuvenated binders containing 30% and 60% RAP binders,
respectively.
The
RAP
binder
underwent
physical
andand
chemical
transformations
over
respectively.
The
RAP
binder
underwent
physical
and
chemical
transformations
over
respectively.
The
RAP
binder
underwent
physical
chemical
transformations
over
time
when
it
was
exposed
to
a
thermal-oxidative
procedure,
as
evidenced
by
the
different
time
when
it
was
exposed
to
a
thermal-oxidative
procedure,
as
evidenced
by
the
different
time when it was exposed to a thermal-oxidative procedure, as evidenced by the different
increases
oxidative
functional
groups.
could
becaused
caused
the
elimination
of
increases
ininoxidative
functional
groups.
ThisThis
could
be caused
by the
elimination
of volaincreases
in
oxidative
functional
groups.
This
could
be
byby
the
elimination
of volavolatile
components
low-molecular-mass
materials,
or
could
be due
due
to
the
tile
components
or low-molecular-mass
materials,
or itor
could
be due
to the
of of
tile components
ororlow-molecular-mass
materials,
itit could
be
to formation
the formation
formation
of hydrogen
atoms
[42].
The
production
of
sulfoxide
groups
was
also
observed,
as
shown
hydrogen
atoms
[42].
The
production
of
sulfoxide
groups
was
also
observed,
as
shown
by
hydrogen atoms [42].−The
production of sulfoxide groups was also observed, as shown
by
1 frequency (S=O stretching). The absorption at 1160
−1 can
by band
the band
band
at 1030
1030
cm
cm
the
at 1030
cm−1cm
frequency
(S=O(S=O
stretching).
The The
absorption
at 1160
cm−1cm
can
be due
−1 frequency
−1
the
at
stretching).
absorption
at 1160
can
be due
due to the anhydride
groups generated
following
oxidation.
Carbonyl
groups
were
tobethe
groups
generated
following
oxidation.
Carbonyl
groups
were
alsoalso
de- deto anhydride
the anhydride
groups
generated
following
oxidation.
Carbonyl
groups
were
−1 . However,
−1
also
detected
in
the
RAP
at
a
frequency
of
1700
cm
the
addition
of
WEO
to
tected
in the
at a at
frequency
of 1700
cm cm
. However,
the addition
of WEO
to the
−1. However,
tected
in RAP
the RAP
a frequency
of 1700
the addition
of WEO
to RAP
the RAP
the
RAP
binder
decreased
these
oxidative
peaks;
it
is
hypothesized
that
the
WEO
might
binder
decreased
these
oxidative
peaks;
it is ithypothesized
that that
the WEO
might
decrease
binder
decreased
these
oxidative
peaks;
is hypothesized
the WEO
might
decrease
decrease
the
aging[43].
of asphalt
[43].also
Theindicated
results also
indicated
that adding
ZycoTherm
the
aging
of
asphalt
The
results
that
adding
ZycoTherm
into
the
the aging of asphalt [43]. The results also indicated that adding ZycoTherm into WEOthe WEOinto the WEO-rejuvenated
binders
hadeffect
no obvious
effect
on thepeaks
oxidative
peaks groups),
(carbonyl
rejuvenated
binders
had had
no
obvious
on the
oxidative
(carbonyl
rejuvenated
binders
no obvious
effect
on the
oxidative
peaks
(carbonyl
groups),
groups),identical
showingperformance
identical performance
to the WEO-rejuvenated
binders.
showing
to
the
WEO-rejuvenated
binders.
showing identical performance to the WEO-rejuvenated binders.
1700 1700
VA
Transmittance (au)
52
54
Transmittance (au)
54
Softening Point (°C)
a
Softening Point (°C)
56
Softening Point (°C)
Softening Point (°C)
56
9 of
9 of92727
of 27
60R
1030 1030
VA
60R
60R+WEO
60R+WEO
OH
OH
WMA-60R-WEO
WMA-60R-WEO
C-H
C=O
C=O
carbonyl
carbonyl
S=O
S=O
sulfoxide
sulfoxide
C-H
4000 4000 3600 3600 3200 3200 2800 2800 2400 2400 2000 2000 1600 1600 1200 1200 800 800 400 400
−1
Wavenumber(cm
) −1)
Wavenumber(cm
Figure6.6.Infrared
Infraredspectra
spectraofofasphalt
asphaltbinder
bindersamples
samplescontaining
containing60%
60%RAP
RAPbinder.
binder.
Figure
Figure 6. Infrared
spectra of asphalt
binder samples
containing 60%
RAP binder.
Sustainability2023,
2023,15,
15,x3807
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FOR PEER REVIEW
10 10
ofof2727
1700
1030
Transmittance (au)
VA
30R
30R+WEO
OH
WMA-30R-WEO
C=O
carbonyl
S=O
sulfoxide
C-H
4000
3600
3200
2800
2400
2000
1600
1200
800
400
−1
Wavenumber(cm )
Figure7.7.Infrared
Infraredspectra
spectraofofasphalt
asphaltbinder
bindersamples
samplescontaining
containing30%
30%RAP
RAPbinder.
binder.
Figure
FTIRspectroscopy
spectroscopyisisalso
alsoapplied
appliedtotoestimate
estimatethe
thechemical
chemicalvariations
variationsininthe
thebinder
binder
FTIR
caused
by
moisture
conditioning.
The
acidic
components
are
important
in
determining
caused by moisture conditioning. The acidic components are important in determining
themoisture
moisturedamage
damageofofanan
asphalt
mixture.
Carboxylic
acids,
ketones,
anhydrides
the
asphalt
mixture.
Carboxylic
acids,
ketones,
anhydrides
andand
22-quinolone
groups
are
largely
prevalent
in
the
adsorbed
portion
of
the
asphalt
binder
quinolone groups are largely prevalent in the adsorbed portion of −
the asphalt binder on
onaggregate
the aggregate
exterior.
The wide
of about
to 3500
cm 1 indicates
carboxylic
the
exterior.
The wide
peakpeak
of about
3000 3000
to 3500
cm−1 indicates
carboxylic
acid,
acid,
with
extremely
strong
and
extensive
O-H
stretching
absorption.
Carboxylic
acid is
with extremely strong and extensive O-H stretching absorption. Carboxylic acid is easily
easily absorbed by aggregates in the binder–aggregate mixing. At the binder–aggregate
absorbed by aggregates in the binder–aggregate mixing. At the binder–aggregate contact,
contact, the connections of carboxylic acids and Si-OH molecules on the aggregate exterior
the connections of carboxylic acids and Si-OH molecules on the aggregate exterior are
are weak. According to Mannan, et al. [44], if the asphalt binder is immersed in water for
weak. According to Mannan, et al. [44], if the asphalt binder is immersed in water for nunumerous days, the absorbed water in the binder can be seen in the FTIR spectrum at the
merous days, the
absorbed water in the binder can be seen in the FTIR spectrum at the
3100–3700 cm−1 wavenumber section.
3100–3700 cm−1 wavenumber section.
It can be seen in Figures 6 and 7 that the moisture-conditioned samples of WEOIt can be seen in Figures 6 and 7 that −
the
moisture-conditioned samples of WEO1 , demonstrating
rejuvenated binders had a peak at 3400 cm−1
that the WEO-rejuvenated
rejuvenated binders had a peak at 3400 cm , demonstrating that the WEO-rejuvenated
binders were exposed to moisture damage. However, this functional group vanished
binders were exposed to moisture damage. However, this functional group vanished
when the WEO-rejuvenated binders were modified with ZycoTherm, indicating that the
when the WEO-rejuvenated binders were modified with ZycoTherm, indicating that the
ZycoTherm additive works adequately as an antistripping agent to remove this waterZycoTherm additive works adequately as an antistripping agent to remove this watersensitive group.
sensitive group.
3.1.3. TG Analysis
3.1.3. TG Analysis
TG analysis of binder samples is presented in Figure 8. The curves were divided into
analysis
of binder
samples
is presented
in Figure
Thelost
curves
divided
into
fourTG
major
regions.
All binder
specimens
in the first
region8.had
only were
a minimal
quantity
four
major regions.
All binder
specimens
in the first region
had
a minimal
of weight.
The initial
decomposition
temperature,
defined
aslost
the only
temperature
atquanwhich
◦ C)
tity
of weight.
The initial
decomposition
temperature,
defined
as the temperature
at which
mass
loss exceeds
2%, denotes
the ending
of this region.
The following
region (200–400
mass
loss an
exceeds
2%, denotes
ending
ofdemonstrating
this region. Thethat
following
region
(200 °C–400
exhibits
increased
rate of the
weight
loss,
the binder
fractions
were
°C)
exhibitsdecomposing.
an increased rate
loss,
demonstrating
that no
thesignificant
binder fractions
were
thermally
The of
TGweight
analysis
reveals
that there was
mass loss
up
◦
thermally
decomposing.
The
TG
analysis
reveals
that
there
was
no
significant
mass
loss
to 285 C, demonstrating that the specimen was thermally stable up to that temperature and
up
tobreakdown
285 °C, demonstrating
thatthis
thetemperature,
specimen was
thermally
stable
to that
that
occurred above
causing
weight
loss.up
Mass
loss temperadecreased
◦ C). The
ture
and
that breakdown
this
temperature,
causing
weight
loss.weight
Mass loss
even
further
in the thirdoccurred
region ofabove
the TG
analysis
(400–600
greatest
loss
◦ C. In the
◦ C), the
was observed
temperatures
between
385
480analysis
last°C–600
region°C).
(600–800
decreased
evenatfurther
in the third
region
of and
the TG
(400
The greatest
specimens
showed
a virtually
flat peak, indicating
weight
residues
weight
loss was
observed
at temperatures
between no
385additional
and 480 °C.
In theloss.
last The
region
(600
remaining
decomposition
were
determined
be 18%
of the original
weight.weight
°C–800
°C), after
the specimens
showed
a virtually
flattopeak,
indicating
no additional
loss. The residues remaining after decomposition were determined to be 18% of the original weight.
Sustainability 2023, 15, 3807
appear not to affect the thermal stability of the blended binders, since the decomposition
temperature (flash point) is not significantly altered. The TG curves of the WEO-rejuvenated binders (with and without ZycoTherm) and virgin binder were nearly similar. It is
also noted that no thermal breakdown of the rejuvenator was seen at the typical temperatures for mixing and compacting asphalt, which are 140 °C and 163 °C, respectively. The
11 of 27
findings of this test are similar to earlier research [46,47], demonstrating that regenerated
binders are unsusceptible to regenerating agent loss through mixing.
100
VA
30R
30R+WEO
60R
60R+WEO
WMA-30R-WEO
WMA-60R-WEO
Mass Loss (%)
80
60
Region 2
Region 1
Region 3
Region 4
40
20
0
0
200
400
600
800
Temperature (°C)
Figure
Figure 8.
8. TG
TGanalysis
analysis of
ofasphalt
asphalt binder
binder samples.
samples.
3.2. Asphalt
Evaluations
The TGMixtures’
analysis also
revealed that the samples containing RAP binders had the highest
thermostability
of the binders
tested.
3.2.1.
Marshall Stability
and Flow
TestThese data lend credence to the hypothesis that the
RAP binder contains a considerable amount of asphaltene, which maintains its thermal
Table 4 depicts the findings of the Marshall test on asphalt mixture samples with
stability at elevated temperatures [45]. However, the ZycoTherm and WEO addition
virgin materials and rejuvenated samples with varying concentrations of RAP and conappear not to affect the thermal stability of the blended binders, since the decomposition
taining the ZycoTherm additive. Marshall stability quantifies the ultimate load that the
temperature (flash point) is not significantly altered. The TG curves of the WEO-rejuvenated
mixture can resist and corresponds well with in-service pavement rutting data. Marshall
binders (with and without ZycoTherm) and virgin binder were nearly similar. It is also
stability increases, whereas the flow decreases with the incorporation of RAP. This
noted that no thermal breakdown of the rejuvenator was seen at the typical temperatures
demonstrates that the addition of RAP raises the ◦rutting resistance.
The highest stability
for mixing and compacting asphalt, which are 140 C and 163 ◦ C, respectively. The findings
was achieved at 26.37 kN for an asphalt mix made with 60% RAP, while the stability of
of this test are similar to earlier research [46,47], demonstrating that regenerated binders
HMA
was 15.49 kN.
is due to agent
the stiff
aged
binder
increasing the strength of the mix.
are unsusceptible
to This
regenerating
loss
through
mixing.
The findings are consistent with those of earlier researchers, Taherkhani and Noorian [48],
as
well
as Katla,
et al. [49].
3.2.
Asphalt
Mixtures’
Evaluations
3.2.1. Marshall Stability and Flow Test
Table 4. Volumetric characteristics of mixtures.
Mixture ID
Reference Mix
30R
Table 4 depicts the findings of the Marshall test on asphalt mixture samples with virgin
materials and rejuvenated samples with varying
of RAP and containing
Mixes’ concentrations
Properties
the ZycoTherm
quantifies the ultimate load
that the
mixture
Optimal
Binder additive. Marshall stability
Stability
Marshall
Quotient
Air Voids in
Total
Flow
(mm)
can
resist
and
corresponds
well
with
in-service
pavement
rutting
data.
Marshall
stability
Content%
(kN)
(kN/mm)
Volume%
(2–4 mm)
increases, whereas the
flow decreases with
of RAP. This
demonstrates
Min the
8.83incorporation
kN
(2.95–4.91)
that the addition of RAP raises the rutting resistance. The highest stability was achieved at
5.0
4.00
15.49
3.50
4.43
26.37 kN for an asphalt mix made with 60% RAP, while the stability of HMA was 15.49 kN.
5.0
4.10
24.05
3.25
7.40
This is due to the stiff aged binder increasing the strength of the mix. The findings are
consistent with those of earlier researchers, Taherkhani and Noorian [48], as well as Katla,
et al. [49].
Sustainability 2023, 15, 3807
12 of 27
Table 4. Volumetric characteristics of mixtures.
Mixes’ Properties
Mixture ID
Reference Mix
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
WMA-60R-WEO
Optimal Binder
Content%
5.0
5.0
5.0
5.0
5.0
5.0
5.0
Air Voids in Total
Volume%
Stability
(kN)
Min 8.83 kN
Flow (mm)
(2–4 mm)
Marshall
Quotient
(kN/mm)
(2.95–4.91)
4.00
4.10
4.14
4.18
3.95
4.16
4.20
15.49
24.05
16.15
17.56
26.37
17.82
18.23
3.50
3.25
3.95
3.85
2.95
3.84
3.79
4.43
7.40
4.09
4.56
8.94
4.64
4.81
Table 4 also demonstrates that stability was reduced when WEO (12%) was added. The
oil’s softening action can be associated with the decrease in stability of the rejuvenated HMA
mixtures. The colloidal structure of the RAP binder is restored by the chemical reaction
between the polar group of the WEO and asphaltene molecules [50]. The rejuvenated
HMA mixtures containing 30% and 60% RAP binders had stability values of 16.15 kN
and 17.82 kN, respectively. The results indicated that the stability values of the WEOregenerated HMA mixtures exceeded those of the reference HMA (15.49 kN). The results
indicate that all samples exceeded the minimal stability criterion (8.83 kN). The results also
showed that the rejuvenated mixture had higher flow values than those of the HMA and
RAP mixtures. This may increase the rutting of WEO-rejuvenated asphalt. The flow values
recorded for rejuvenated mixtures containing 30% and 60% RAP are 3.95 mm and 3.84 mm,
respectively, and fall within the specification limit (2–4 mm). The findings are consistent
with earlier research [51].
Meanwhile, the addition of the antistripping additive to rejuvenated mixtures was
found to increase the stability and decrease the flow of mixtures. The results of this
test clearly show that rejuvenated mixtures containing antistripping additive function
better than the unmodified rejuvenated mixtures with respect to stability and flow. This
may be explained by the surplus of adhesion bonds created by siloxane groups between
the aggregate and the asphalt binder [52]. The ZycoTherm modification of rejuvenated
mixtures containing 30% and 60% RAP yielded stability values of 17.56 kN and 18.23 kN,
respectively. According to Wang, et al. [53], adding liquid antistripping additives to the mix
causes the aggregate to react with the binder instead of water. Furthermore, incorporating
antistripping additives into the mixture enhances the bond between the binder and the
aggregate particles [52].
3.2.2. Indirect Tensile Strength (ITS) Test
The result of the indirect tensile strength (ITS) of mixtures for two different conditions
is presented in Figure 9. Based on the results, the moisture significantly affects the ITS
values for all mixtures. This may be due to the mechanism of adhesion loss between the
asphalt binder and the aggregate surface or the cohesive failure of the asphalt mixtures due
to the interaction with moisture. Nonetheless, it needs to be underlined that the bonding
between the binder and the aggregate under wet circumstances is highly reliant on binder
modification type and conditioning duration [54].
Sustainability 2023, 15, 3807
x FOR PEER REVIEW
of 27
27
1313of
1800
Wet
Dry
1700
1550
1600
1428
ITS (kPa)
1400
1250
1216
1200
1095
1150
1120
1030
1000
1350
1320
1120
1000
885
800
600
400
Figure 9.
9. Indirect
Indirect tensile strength (ITS) values of different specimens for wet and dry conditions.
Figure
conditions.
The inclusion
inclusion of
from
2121
to to
36%
as
The
of RAP
RAP binders
bindersin
inHMA
HMAimproves
improvesthe
thetensile
tensilestrength
strength
from
36%
compared
to
control
HMA
for
both
wet
and
dry
conditions,
respectively.
This
indicates
as compared to control HMA for both wet and dry conditions, respectively. This indicates
that the
the mixture
mixture containing
containing 60R
60R has
has the
the highest
highest resistance
resistance to
to fatigue
fatigue as
as aa result
result of
of rising
rising
that
stiffness.
The
tensile
strength
of
the
mixture
was
seen
to
be
slightly
diminished
stiffness. The tensile strength of the mixture was seen to be slightly diminished duedue
to
to further
modification
WEO
addition
the WMA
antistripping
method.
further
modification
withwith
WEO
addition
and and
usingusing
the WMA
antistripping
method.
Both
Both modified mixtures can sustain relatively high tensile strength as compared to HMA.
modified mixtures can sustain relatively high tensile strength as compared to HMA. This
This clarifies that mixtures containing ZycoTherm developed a better adhesion and thus
clarifies that mixtures containing ZycoTherm developed a better adhesion and thus enenhanced the binder–aggregate mechanical interlocking. The adherence of the mixture
hanced the binder–aggregate mechanical interlocking. The adherence of the mixture concontaining ZycoTherm against fatigue and cracking damage was verified, as the tensile
taining ZycoTherm against fatigue and cracking damage was verified, as the tensile
strength increased up to 21% compared to HMA. Furthermore, decreasing the mixing
strength increased up to 21% compared to HMA. Furthermore, decreasing the mixing
temperatures of WMA mixes results in reduced cracking resistance under tensile loading.
temperatures of WMA mixes results in reduced cracking resistance under tensile loading.
Figure 10 presents the tensile strength ratio (TSR) of the asphalt mixtures. The results
Figure 10 presents the tensile strength ratio (TSR) of the asphalt mixtures. The results
reveal that asphalt mixes containing RAP have lower TSR values than the reference mixture,
reveal that asphalt mixes containing RAP have lower TSR values than the reference mixindicating a poorer resistance to moisture degradation. This can be attributed to the
ture, indicating a poorer resistance to moisture degradation. This can be attributed to the
decreased alkalinity and hydrophilic characteristics of the aggregates included in RAPdecreased alkalinity and hydrophilic characteristics of the aggregates included in RAPcontaining mixes. However, the WEO rejuvenation of RAP mixtures increased the TSR of
containing
mixes. However,
the WEO
rejuvenation
of RAP
mixtures
increased
TSR of
mixtures, demonstrating
a better
resistance
to moisture
damage.
In terms
of thethe
influence
mixtures,
demonstrating
a
better
resistance
to
moisture
damage.
In
terms
of
the
influence
of antistripping agent additions on TSR values, mixtures containing ZycoTherm have the
of
antistripping
agent
additions
on TSRthat
values,
mixtures
containing ZycoTherm
have the
uppermost
values
of TSR.
This proves
the use
of an antistripping
agent enhanced
the
uppermost
values
of
TSR.
This
proves
that
the
use
of
an
antistripping
agent
enhanced
the
resistance of the mixture against stripping. This is due to the additives forming a strong
resistance
of the
mixture against
This is due
to theand
additives
forming
a strong
link between
the negative
electricalstripping.
ions on aggregate
surfaces
the binder
[55]. Goli
and
link
between
the
negative
electrical
ions
on
aggregate
surfaces
and
the
binder
[55].
Goli
Latifi [56] acquired similar results, whereby the lower production and mixing temperature
and
Latifiaffected
[56] acquired
whereby the
lower production and mixing temof WMA
the ITSsimilar
values results,
of the WMA–RAP
specimen.
perature of WMA affected the ITS values of the WMA–RAP specimen.
Sustainability 2023, 15, x FOR PEER REVIEW
Sustainability 2023, 15, 3807
14 of 27
14 of 27
90
TSR (%)
80
70
60
50
Figure 10.
10. Tensile
Tensile strength
strength ratio
ratio (TSR)
(TSR) of
of different
different asphalt
asphalt mixtures.
mixtures.
Figure
Thelowest
lowestTSR
TSRofof
80%
is often
provided
to determine
the mixes
with adequate
The
80%
is often
provided
to determine
the mixes
with adequate
moismoisture
resistance
[57].
It
can
be
perceived
from
Figure
10
that
the
TSR
values
of
all
mixes
ture resistance [57]. It can be perceived from Figure 10 that the TSR values of all mixes
are
are greater than 80%, indicating the mixtures have a good resistance to moisture damage.
greater than 80%, indicating the mixtures have a good resistance to moisture damage.
However, mixtures containing RAP binders had TSR values of less than 80%, which might
However, mixtures containing RAP binders had TSR values of less than 80%, which might
indicate moisture-sensitive mixtures. According to Abed, et al. [58], antistripping additives
indicate moisture-sensitive mixtures. According to Abed, et al. [58], antistripping addiare utilized when the mixture fails the TSR test’s required standards, exhibiting moisture
tives are utilized when the mixture fails the TSR test’s required standards, exhibiting
degradation. The antistripping additives function in the mix, causing the aggregate exterior
moisture degradation. The antistripping additives function in the mix, causing the aggreto interact with bitumen instead of water.
gate exterior to interact with bitumen instead of water.
3.2.3. Resilient Modulus (MR ) Test
3.2.3. Resilient Modulus (MR) Test
The resilient modulus (MR ) values for wet and dry conditions of asphalt mixtures
The resilient
modulus
R) values for wet and dry conditions of asphalt mixtures are
are revealed
in Figure
11. (M
Based
on the presented results, the mixtures incorporating
revealed
in
Figure
11.
Based
on
the modulus
presentedthan
results,
mixtures
RAP binders had a greater resilient
thatthe
of HMA.
Thisincorporating
is due to the RAP
high
binders
had
a
greater
resilient
modulus
than
that
of
HMA.
This
is
due
to theresulting
high RAP
RAP content, which ultimately increases the stiffness of the mixture, thus
in
content,
ultimately
increases
the stiffness
of the mixture,
greater
a greaterwhich
resilient
modulus.
The stiffness
increases
owing tothus
the resulting
increase in
in aviscosity
resilient
modulus.
The stiffness
increases
owing [59].
to the
increase in the
viscosity
functional
functional
groups, such
as ketones
and aromatics
Furthermore,
addition
of WEO
groups,
suchMas
ketones
and
aromatics
[59].
Furthermore,
the
addition
of
WEO
affects
affects the
values
of
mixtures.
The
WEO,
as
specified
by
Fernandes,
et
al.
[60],the
is
R
M
R
values
of
mixtures.
The
WEO,
as
specified
by
Fernandes,
et
al.
[60],
is
primarily
used
primarily used as a softening additive for the asphalt binder, lowering the viscosity and
as
a softening
additive
for the asphalt
binder, lowering
the viscosity
and increasing
rutting
increasing
rutting
tendency.
The combinations
of WMA,
RAP binders
and WEO
show
tendency.
combinations
of WMA,
RAP binders
WEO
show
behavior,
interestingThe
behavior,
where the
RAP stiffens
the mix,and
while
WEO
actsinteresting
as a softening
agent,
where
the RAPresulting
stiffens the
while WEO
acts as
a softening
agent, consequently
resultconsequently
in mix,
a balanced
mix with
optimum
properties.
Lower mixing
and
ing
in a balanced
mix with
optimum
Lower
mixingviscosity,
and production
temperaproduction
temperature
of the
WMA properties.
method leads
to a higher
thus reducing
the
ture
ofand
the ability
WMA of
method
leads to aflow.
higher
thus
reducing
the strain and
strain
the mixture
As aviscosity,
result, the
mixtures
incorporating
RAP,ability
WEO
of
theZycoTherm
mixture to flow.
Ashave
a result,
the mixtures
WEO
andAs
ZycoTherm
and
agents
a greater
resilientincorporating
modulus thanRAP,
that of
HMA.
in the ITS
values have
presented
in Figure
9, amodulus
similar pattern
was
as thepresented
moisture
agents
a greater
resilient
than that
of recorded
HMA. AsininFigure
the ITS11,
values
effect
was9,significant
relativewas
to the
MR values
for all
mixtures.
Thewas
MR signifvalues
in
Figure
a similar pattern
recorded
in Figure
11,types
as theofmoisture
effect
were relative
reducedto
bythe
approximately
6.4%
11.2%
for WMA-60R-WEO
andwere
WMA-30R-WEO,
icant
MR values for
all and
types
of mixtures.
The MR values
reduced by
respectively, as6.4%
the samples
werefor
exposed
to moisture.and WMA-30R-WEO, respectively,
approximately
and 11.2%
WMA-60R-WEO
as the samples were exposed to moisture.
Sustainability
FOR PEER REVIEW
Sustainability2023,
2023,15,
15,x3807
1515ofof27
27
8000
Resilient Modulus (MPa)
Wet
Dry
6000
4000
2000
0
Figure11.
11.Resilient
Resilientmodulus
modulus(M
(MRR
differentasphalt
asphaltmixtures
mixturesunder
underdry
dryand
andwet
wetconditions.
conditions.
Figure
) )ofofdifferent
RMR (%)
The resilient modulus (M ) values for wet and dry conditions of asphalt mixtures
The resilient modulus ratioR(RMR) for the mixtures is presented in Figure 12, and the
are revealed in Figure 11. Based on the presented results, the mixtures incorporating
findings reveal that WMA mixtures had greater RMR values than the reference and other
RAP binders had a greater resilient modulus than that of HMA. This is due to the high
mixes, indicating a better resistance to moisture and cracks. The decreased viscosity of the
RAP content, which ultimately increases the stiffness of the mixture, thus resulting in
rejuvenated binders modified with ZycoTherm allows the binder to penetrate the porous
a greater resilient modulus. The stiffness increases owing to the increase in viscosity
structure in the aggregate exterior morphology. Furthermore, lower mixing temperatures
functional groups, such as ketones and aromatics [59]. Furthermore, the addition of WEO
in
WMAthe
mixtures
can lead
to less aging
therefore
lower by
possibility
of cracking
andis
affects
MR values
of mixtures.
The and
WEO,
as specified
Fernandes,
et al. [60],
moisture
intrusion
to
the
binder–aggregate
interface
during
the
conditioning
phase
[61].
primarily used as a softening additive for the asphalt binder, lowering the viscosity and
According
Goli and
Latifi [56],
mixing temperatures
in the
WMA and
mixture
lead
to
increasingtorutting
tendency.
Thelower
combinations
of WMA, RAP
binders
WEO
show
delayed
aging,
which
in
turn
slows
down
moisture
intrusion
to
the
binder–aggregate
ininteresting behavior, where the RAP stiffens the mix, while WEO acts as a softening agent,
terface
during the
conditioning
phase. mix with optimum properties. Lower mixing and
consequently
resulting
in a balanced
production temperature of the WMA method leads to a higher viscosity, thus reducing the
100and ability of the mixture to flow. As a result, the mixtures incorporating RAP, WEO
strain
and ZycoTherm agents have a greater resilient modulus than that of HMA. As in the ITS
90 presented in Figure 9, a similar pattern was recorded in Figure 11, as the moisture
values
effect was significant relative to the MR values for all types of mixtures. The MR values
were80
reduced by approximately 6.4% and 11.2% for WMA-60R-WEO and WMA-30R-WEO,
respectively, as the samples were exposed to moisture.
70
The resilient modulus ratio (RMR) for the mixtures is presented in Figure 12, and the
findings reveal that WMA mixtures had greater RMR values than the reference and other
60 indicating a better resistance to moisture and cracks. The decreased viscosity of the
mixes,
rejuvenated binders modified with ZycoTherm allows the binder to penetrate the porous
50
structure
in the aggregate exterior morphology. Furthermore, lower mixing temperatures
in WMA mixtures can lead to less aging and therefore lower possibility of cracking and
moisture intrusion to the binder–aggregate interface during the conditioning phase [61].
According to Goli and Latifi [56], lower mixing temperatures in the WMA mixture lead
to delayed aging, which in turn slows down moisture intrusion to the binder–aggregate
interface
during the
conditioning
phase.
Figure
12. Resilient
modulus
ratio (RMR)
for different asphalt mixtures.
3.2.4. Dynamic Creep Test
Figures 13 and 14 illustrate the dynamic creep test findings for different types of mixtures. Dynamic creep is known as the response relationship between the load and deformation. By examining the plot in Figure 13, the incorporation of the RAP binder into asphalt mixes raises the FN value of all mixes. The 30R and 60R increase the FN value of the
reference HMA mixture by 144% and 357%, respectively. The binder adhering to the aggregate during the recycling process is tougher than the newly added binder. This is
Sustainability 2023, 15, 3807
structure in the aggregate exterior morphology. Furthermore, lower mixing temperatures
in WMA mixtures can lead to less aging and therefore lower possibility of cracking and
moisture intrusion to the binder–aggregate interface during the conditioning phase [61].
According to Goli and Latifi [56], lower mixing temperatures in the WMA mixture lead to
delayed aging, which in turn slows down moisture intrusion to the binder–aggregate
in16 of
27
terface during the conditioning phase.
100
RMR (%)
90
80
70
60
50
Figure 12. Resilient modulus ratio (RMR) for different asphalt mixtures.
Figure 12. Resilient modulus ratio (RMR) for different asphalt mixtures.
3.2.4. Dynamic Creep Test
3.2.4. Dynamic Creep Test
Figures 13 and 14 illustrate the dynamic creep test findings for different types of
FiguresDynamic
13 and 14creep
illustrate
the dynamic
creep testrelationship
findings for different
of mixmixtures.
is known
as the response
between types
the load
and
tures.
DynamicBy
creep
is known
the response
between the
and binder
defordeformation.
examining
theasplot
in Figure relationship
13, the incorporation
of load
the RAP
Sustainability 2023, 15, x FOR PEER REVIEW
16
mation.
By examining
the plot
in Figure
13,all
themixes.
incorporation
the 60R
RAPincrease
binder into
into asphalt
mixes raises
the FN
value of
The 30Rofand
the asFN
phalt
the FN
value
of all by
mixes.
andrespectively.
60R increaseThe
the binder
FN value
of the
valuemixes
of the raises
reference
HMA
mixture
144%The
and30R
357%,
adhering
reference
HMA mixture
and 357%,
respectively.
binder
adhering
to the
agto the aggregate
duringby
the144%
recycling
process
is tougherThe
than
the newly
added
binder.
gregate
duringmostly
the recycling
process
isbeing
tougher
than
theoxidation
newly
added
Thisand
is and w
caused
the pavement
being
exposed
to oxidation
while used
being
used
This is mostly
caused
by the by
pavement
exposed
to
while binder.
being
ered. Overall,
lower temperatures
in less oxidative
activity,
thus reducing
th
weathered. Overall,
lower temperatures
result in result
less oxidative
activity, thus
reducing
the
ting resistance.
Meanwhile,
theof
addition
of WEO contributed
to decreasing
rutting resistance.
Meanwhile,
the addition
WEO contributed
to decreasing
the FN ofthe FN of
thistowas
the oil’s impact
softening
onbinder.
the RAP
binder. Nevertheless,
th
mixtures; this tures;
was due
thedue
oil’sto
softening
on impact
the RAP
Nevertheless,
the
rejuvenated mixture
hadmixture
a relatively
FNhigher
value FN
thanvalue
the reference
HMA. Several
juvenated
had ahigher
relatively
than the reference
HMA. Several
studies made ies
a similar
[1]. Li, [1].
et al.
that aged
binders’
made aobservation
similar observation
Li,[62]
et al.also
[62]disclosed
also disclosed
that aged
binders’ ph
physical features
may be
improved
by applying
a suitable
amount
of WEO,
which
would
features
may
be improved
by applying
a suitable
amount
of WEO,
which
would also
also raise theirtheir
lightlight
constituents
(saturates
and aromatics).
Furthermore,
the results
constituents
(saturates
and aromatics).
Furthermore,
theshow
results show
that mixes incorporating
RAP andRAP
WEO
have
a relatively
higher resistance
to moisture
mixes incorporating
and
WEO
have a relatively
higher resistance
to moisture d
degradation indation
respect
of
a
decline
in
FN
value.
in respect of a decline in FN value.
6000
Wet
Dry
FN
5000
4000
3000
2000
1000
0
Figure 13. FlowFigure
number
fornumber
asphalt(FN)
mixtures.
13.(FN)
Flow
for asphalt mixtures.
100
R (%)
90
80
0
Sustainability 2023, 15, 3807
17 of 27
Figure 13. Flow number (FN) for asphalt mixtures.
100
CR (%)
90
80
70
60
50
Figure 14. Dynamic
creep
ratio (CR)creep
results
for (CR)
different
mixtures.
Figure
14. Dynamic
ratio
results
for different mixtures.
The results from
andFigures
14 also13
showed
themodifying
rejuvenated
TheFigures
results 13
from
and 14that
alsomodifying
showed that
themixrejuvenated
tures with ZycoTherm
increased
the
FN
of
mixtures,
thus
improving
the
rutting
resistance
tures with ZycoTherm increased the FN of mixtures, thus improving the rutting resis
of mixtures inof
wet
and dryinconditions.
Furthermore,
the findings from
Figure 14from
indicate
mixtures
wet and dry
conditions. Furthermore,
the findings
Figure 14 ind
that the rejuvenated mixtures modified with the antistripping agent acquired the highest
that the rejuvenated mixtures modified with the antistripping agent acquired the hi
rutting resistance toward moisture under repeated load. The WMA-60R-WEO mixture
rutting resistance toward moisture under repeated load. The WMA-60R-WEO mi
records a greater number of flow cycles compared to HMA, and the mixture contains 30%
records a greater number of flow cycles compared to HMA, and the mixture contain
RAP binder. This is due to ZycoTherm, which increased the adherence of bitumen to the
RAP binder. This is due to ZycoTherm, which increased the adherence of bitumen t
aggregates, and the FN was also affected by the content of stiff RAP used in the mixture [29].
Khani Sanij, et al. [63] demonstrated that the FN of WMA samples increased with the use
of ZycoTherm as an antistripping additive; this demonstrates that ZycoTherm lessens the
asphalt sample’s tendency to rut.
ZycoTherm is an organosilane additive, meaning it contains silanol groups. Silanol
groups are functional siloxane chains (Si-O-Si film structure) formed by mineral material
surface silanol groups. These groups are resistant to moisture (hydrophobic film) and limit
water infiltration and the development of H-bonds at the aggregate–binder bond, hence
enhancing the resistance of the aggregate and binder adhesion to moisture degradation.
However, this chemical theory appears to be closely aligned with experimental observations
from this study. Yet, the additive is disseminated in the binder, and no definite remark on
this chemical diffusion and response at the binder–aggregate interface has been made [52].
Although various conditioning procedures and moisture resistance criteria were utilized in this laboratory investigation, the findings show a similar pattern. The differences
might be ascribed to diverse conditioning methods and load operations utilized in water
sensitivity assessment methodologies, as well as the experimental methodologies’ limitations in assessing moisture damage.
3.2.5. Aggregate Coating Test
The percentage of coating for the aggregates of different mixtures is presented in
Figure 15. In general, asphalt binder is an adhesive material employed to uniformly coat
the aggregate interface. The coating percentage in Figure 15 demonstrated a significant
drop once the RAP binder started to be incorporated into the HMA. This is because the
RAP binder is an oxidatively aged binder, resulting in higher viscosity compared to the
virgin asphalt binder [42].
Sustainability 2023, 15, 3807
The percentage of coating for the aggregates of different mixtures is presented in Figure 15. In general, asphalt binder is an adhesive material employed to uniformly coat the
aggregate interface. The coating percentage in Figure 15 demonstrated a significant drop
once the RAP binder started to be incorporated into the HMA. This is because the RAP
18 of 27
binder is an oxidatively aged binder, resulting in higher viscosity compared to the virgin
asphalt binder [42].
100
Coating (%)
96
92
88
84
80
Figure15.
15.Aggregate
Aggregatecoating
coatingof
ofdifferent
differentmixtures.
mixtures.
Figure
However,the
thecoating
coatingpercentage
percentageincreased
increasedconsistently
consistentlyas
asthe
theWEO
WEOand
andWMA
WMAmethmethHowever,
ods were adopted. The coating percentage increased by 8.2% and 8.7% for WMA-30R-WEO
ods were adopted. The coating percentage increased by 8.2% and 8.7% for WMA-30Rand WMA-60R-WEO, respectively. The nature of WEO, which acts as a softening agent
WEO and WMA-60R-WEO, respectively. The nature of WEO, which acts as a softening
in the mixture, is reducing the viscosity, thus improving the binder distribution. A study
agent in the mixture, is reducing the viscosity, thus improving the binder distribution. A
conducted by Eltwati, et al. [64] explained that the aromatic compounds in WEO softened
study conducted by Eltwati, et al. [64] explained that the aromatic compounds in WEO
the RAP binder, causing an increase in the coating of aggregates.
softened the RAP binder, causing an increase in the coating of aggregates.
In general, moisture damage in asphalt mixtures can be attributed to adhesive and/or
In general, moisture damage in asphalt mixtures can be attributed to adhesive and/or
cohesive failure. This is understandable, since the chemical interaction between the binder
cohesive failure. This is understandable, since the chemical interaction between the binder
and the aggregate is extremely complex. Adhesive failure occurs when the binder and the
aggregate are detached from each other. Thus, the coating ability of the binder to coat the
aggregate is of the utmost importance for good adhesion [65]. Suitable coating properties
ensure that the binder can penetrate the surface structure and lead to better mechanical
interlocking at the interface [66]. Han, et al. [67] describe cohesive failure as the loss of
cohesion force in the binder due to moisture. The failure is typically attributed to two
causes: the degradation of the binder caused by permeation into the binder and the passage
of water through the binder–aggregate contact.
According to AASHTO T195 (2011) [39], 95% coating is the lowest degree allowed
in the HMA design. Inadequate coating may raise the susceptibility to moisture damage.
When water permeates the asphalt films and directly interacts with the surface of the
aggregate, it is noted that insufficient coating may accelerate the break of the connection
between the binder and the aggregate. The WEO-rejuvenated mixtures modified with
ZycoTherm recorded 98.2% and 97.2% coating values, which is only a 0.2% and 1.2%
difference from the coating value of the HMA (98.4%). This may be characterized by WEO’s
efficiency in encircling the aggregates’ interface by reducing the aged binder’s viscosity
and increasing its fluidity, hence increasing the interaction between the aged and virgin
asphalts [64]. Furthermore, it is also known that ZycoTherm, a type of chemical additive,
helps reduce the frictional force of the microscopic interface between the binder and the
aggregate, typically between 85 and 140 ◦ C [25]. ZycoTherm improves the ability of WEOrejuvenated mixtures to coat by overcoming or reducing friction forces. The frictional forces
between the binder and the aggregate are mainly van der Waals forces, which include
hydrogen bonding, dispersion forces and dipole–dipole interactions. Caputo, et al. [25]
highlighted that the reduction in frictional force improves the mixing and compaction stage;
thus, higher adhesion is obtained. Based on the results, the combination of ZycoTherm
with WEO-rejuvenated binder proved to have a positive impact on binder coating abilities.
Sustainability 2023, 15, 3807
19 of 27
3.2.6. Wheel Tracking Test
Post-Compaction (PC)
PC consolidation is the deformation described in millimeters at 500 cycles or 1000
wheel passes in the sample. Post-compaction takes place rapidly due to the mixture
densification during the first few minutes of the test [68]. The rut depth of different
mixtures in wet and dry conditions due to the PC effect is shown in Figure 16. The results
reveal that the inclusion of the RAP binder into HMA reduced the PC resistance in dry and
wet conditions, as predicted, owing to asphalt stiffening. This indicates that the samples
incorporating RAP have a greater resistance to rutting in the PC area. The results also
exhibited that raising the dosage of the RAP binder in HMA samples in both wet and dry
conditions reduced the PC values; this is because the virgin binder was replaced with a
stiffer binder. Meanwhile, the rejuvenation of the RAP binder with WEO led to an increase
in the PC rut depth for both conditions; however, the PC rut depth for rejuvenated mixtures
containing ZycoTherm was much lower. This shows that rejuvenated mixtures modified
with ZycoTherm were more consistent and readily well compacted even before the wheel
tracking loadings started to be applied. The PC rut depth of WMA-60R-WEO is relatively
lower (for both conditions) compared to WMA-30R-WEO due to a higher percentage of
RAP, which is believed to yield a stiffer binder within the mix. A similar observation
was obtained by Fakhri and Hosseini [69]. In addition, the lower production and mixing
temperature of the WMA method also influenced the stiffness of the mix. According to
the results, the moisture effect on all mixtures was relatively significant. A drastic increase
Sustainability 2023, 15, x FOR PEER REVIEW
19 of 27
was observed in PC rut depth as a result of the presence of moisture, which affects the
binder–aggregate adhesion and/or binder cohesion.
Rut depth (mm) after 500 cycles
5.00
4.53
Dry
4.21
Wet
3.85
4.00
3.51
3.21
3.00
2.35
2.16
2.31
2.13
1.85
2.00
2.11
1.63
1.32
1.01
1.00
0.00
Figure 16. Post-compaction of different mixtures for wet and dry conditions.
Figure 16. Post-compaction of different mixtures for wet and dry conditions.
Rutting Depth Versus Load Cycle
Rutting
Depth
Cycle
Figures
17 versus
and 18 Load
illustrate
the rutting depth of samples per loading cycle under dry
Figures
17
and
18
illustrate
rutting
depthtoofassess
samples
loading
dry
and wet conditions. These resultsthe
were
projected
the per
influence
of cycle
waterunder
on rutting
and
wet
conditions.
These
results
were
projected
to
assess
the
influence
of
water
on
rutresistance. It is noted that the presence of moisture influences the rut depths. In comparison
ting
resistance.
It isthe
noted
that the
presence
of rut
moisture
thesuperior
rut depths.
In comto
both
conditions,
loading
cycles
of a wet
for all influences
mixtures are
to those
of a
parison
to
both
conditions,
the
loading
cycles
of
a
wet
rut
for
all
mixtures
are
superior
to
dry rut. This is due to the moisture affecting the aggregate coating and accelerating the loss
those
of
a
dry
rut.
This
is
due
to
the
moisture
affecting
the
aggregate
coating
and
accelerof contact between bitumen and the aggregates [70].
ating the loss of contact between bitumen and the aggregates [70].
0
(mm)
4
8
HMA
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
WMA-60R-WEO
Sustainability 2023, 15, 3807
Rutting Depth versus Load Cycle
Figures 17 and 18 illustrate the rutting depth of samples per loading cycle under dry
and wet conditions. These results were projected to assess the influence of water on rutting resistance. It is noted that the presence of moisture influences the rut depths. In comparison to both conditions, the loading cycles of a wet rut for all mixtures are superior to
20 of 27
those of a dry rut. This is due to the moisture affecting the aggregate coating and accelerating the loss of contact between bitumen and the aggregates [70].
0
HMA
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
WMA-60R-WEO
Rutting (mm)
4
8
12
16
20
0
2000
4000
6000
8000
10,000
10000
No. of Cycle
Sustainability 2023, 15, x FOR PEER REVIEW
20 of 27
Figure
Figure17.
17.Rutting
Ruttingdepth
depthversus
versusload
loadcycle
cycleininaadry
drycondition.
condition.
0
HMA
30R
30R+WEO
WMA-30R-WEO
60R
60R+WEO
WMA-60R-WEO
Rutting (mm)
4
8
12
16
20
0
2000
4000
6000
8000
10,000
10000
No. of Cycle
Figure
Figure 18.
18. Rutting
Rutting depth
depth versus
versus load
load cycle
cycle in
in aa wet
wet condition.
condition.
By
By examining
examining the
the plot
plot in
in Figure
Figure 17,
17, the
the mixtures
mixtures containing
containing RAP
RAP reduced
reduced the
the rutting
rutting
depth
at
the
same
loading
cycles.
The
60R
exhibits
the
highest
rutting
resistance,
depth at the same loading cycles. The 60R exhibits the highest rutting resistance, followed
followed
by
by 30R.
30R. Increasing
Increasing the
the RAP
RAP content
content in
in the
the mixture
mixture contributed
contributed to
to raising
raising the
the final
final loading
loading
cycles compared to HMA, as shown in Figure 19. This corresponds to the presence of
cycles compared to HMA, as shown in Figure 19. This corresponds to the presence of RAP,
RAP, which stiffens the composite binder, thus creating a more rigid structure. Meanwhile,
which stiffens the composite binder, thus creating a more rigid structure. Meanwhile, the
the addition of WEO into RAP mixtures slightly accelerated the rutting, regardless of the
addition of WEO into RAP mixtures slightly accelerated the rutting, regardless of the
amount of RAP, yet performed better than HMA. Higher rutting for mixtures containing
amount of RAP, yet performed better than HMA. Higher rutting for mixtures containing
WEO is due to the softening effect of the WEO aromatic molecules [71]. Fernandes, et al. [72]
WEO is due to the softening effect of the WEO aromatic molecules [71]. Fernandes, et al.
and Ren, et al. [73] shared a similar observation, whereby adding WEO to an asphalt mixture
[72] and Ren, et al. [73] shared a similar observation, whereby adding WEO to an asphalt
weakens the resistance of asphalt toward rutting.
mixture weakens the resistance of asphalt toward rutting.
o Failure
25,000
Wet
Dry
19,876
20,000
16,269
cycles compared to HMA, as shown in Figure 19. This corresponds to the presence of
which stiffens the composite binder, thus creating a more rigid structure. Meanwhil
addition of WEO into RAP mixtures slightly accelerated the rutting, regardless o
amount of RAP, yet performed better than HMA. Higher rutting for mixtures conta
WEO is due to the softening effect of the WEO aromatic molecules [71]. Fernandes
of 27 to an as
[72] and Ren, et al. [73] shared a similar observation, whereby adding21WEO
mixture weakens the resistance of asphalt toward rutting.
Sustainability 2023, 15, 3807
Number of Cycles to Failure
25,000
Wet
Dry
19,876
20,000
16,269
15,000
12,520
10,560
10,000
9345
9934
9736
8250
8876
8950 9126
6150
5000
5,000
4162
5062
0
Figure 19. No. of cycles to achieve the maximum rut depth of 20 mm.
Figure 19. No. of cycles to achieve the maximum rut depth of 20 mm.
The results illustrated in Figure 18 display the different rutting behaviors, especially
The
results modified
illustrated
in Figure
18 display
the different rutting
behaviors, espe
for WEO-rejuvenated
mixtures
with
ZycoTherm.
The performance
of rejuvenated
for
WEO-rejuvenated
mixtures
modified
with
ZycoTherm.
The
performance
of re
mixtures was improved once the WMA antistripping agent (ZycoTherm) was adopted. The
nated
mixtures wasagent
improved
once theimpact
WMAonantistripping
agentin(ZycoTherm
results reveal that
an antistripping
has a positive
rutting resistance
the
presence of moisture. This may be attributed to the fact that rejuvenated samples modified
with ZycoTherm exhibited a high coating percentage, as shown in Figure 15, which impedes
water infiltration to disrupt the binder–aggregate interface. This also denotes that, although
the HMA mixture has a significantly high PC value, it nevertheless loses its cohesive and
adhesive connections more quickly when subjected to recurrent loading in the presence
of moisture.
Moreover, the results shown in Figure 19 indicate that rejuvenated samples modified
with ZycoTherm accelerated the maximum rutting of 20 mm compared to other mixtures,
including the reference HMA. WMA-30R-WEO exhibited the lowest rutting resistance,
whereby it reached the maximum rutting value at 8250 and 8876 cycles for wet and dry
conditions, respectively. On the other hand, WMA-60R-WEO attained maximum rutting
at 8950 and 9126 cycles for wet and dry conditions, respectively. Increases in cycles of
approximately 7.8% and 2.7% over WMA-30R-WEO can be observed. Further observation in Figure 19 indicates that the cycle differences between dry and wet conditions for
rejuvenated samples modified with ZycoTherm are incredibly low. Based on the result,
reductions as low as 2% and 7% in load cycle numbers to failure for WMA-60R-WEO
and WMA-30R-WEO, respectively, were observed when the condition changed from dry
to wet. This shows that rejuvenated samples modified with ZycoTherm have the optimum performance because it is comparable to HMA with 9345 load cycles to failure as
a benchmark.
Stripping Inflection Point (SIP)
SIP is the number of wheel passes completed, where the creep slope and the stripping
slope intersect on the graph [74]. SIP indicates when the mixture begins to suffer moisture
degradation [75]. Figure 20 illustrates the example of rut depth against loading cycles to
identify the SIP for the WMA-30R-WEO sample. In general, three regions were observed
in the plot, which are the creep slope, SIP and the stripping slope. According to Zhang,
et al. [76], the first or the creep region denotes permanent deformation corresponding to a
mechanism, such as plastic flow, whereas the tertiary or stripping region indicates rapid
failure, which is mainly attributed to moisture damage. Walubita, et al. [77] also highlighted
that the tendency to lose the fine aggregate (adhesion failure) would start from the SIP
onwards. Moreover, higher creep slopes, stripping points and stripping slopes indicate
Sustainability 2023, 15, 3807
22 of 27
less damage. A study carried out to evaluate the performance of the Hamburg Wheel
Track Device (HWTD) on mixtures with known field performance found that the SIP for
pavements with excellent field performance was typically larger than 5000 cycles (10,000
passes), whereas pavements with reduced field function had a SIP lower than 1500 cycles
Sustainability 2023, 15, x FOR PEER REVIEW
22 of the
27
(3000 passes) [78]. The smaller quantity of SIP indicates a weaker contact between
asphalt and the aggregate when there is water present [69].
0
500
1000
2000
4000
6000
8000
10,000
10000
0
WMA-30R-WEO
2
Creep Slope
Rut depth (mm)
4
6
Stripping Slope
8
10
12
Stripping Inflection Point
14
16
18
20
SIP 5720
Figure20.
20.Stripping
Strippinginflection
inflectionpoint
point(SIP)
(SIP)for
forWMA-30R-WEO.
WMA-30R-WEO.
Figure
TheSIP
SIPvalues
valuesfor
foreach
eachmixture
mixtureare
are shown
shownin
in Figure
Figure 21.
21. Overall,
Overall,the
theSIP
SIPvalues
valuesof
of
The
RAP
mixtures
and
rejuvenated
mixtures
with
and
without
ZycoTherm
are
greater
than
that
RAP mixtures and rejuvenated mixtures with and without ZycoTherm are greater than
of HMA.
Steady
improvement
can be
observed
as theas
RAP
was added;
however,
the
that
of HMA.
Steady
improvement
can
be observed
thebinder
RAP binder
was added;
howincorporation
of WEO slightly
SIP values.
implementation
of the WMA
ever,
the incorporation
of WEOlowered
slightly the
lowered
the SIPThe
values.
The implementation
of
antistripping
agent
subsequently
improved
the
SIP
values
of
mixtures.
The
SIP
values
the WMA antistripping agent subsequently improved the SIP values of mixtures. The SIP
are incredibly
higher,higher,
with an
80 an
to 82%
compared
to HMA.
The SIP
values
are incredibly
with
80 toincrease
82% increase
compared
to HMA.
Therecorded
SIP recfor
WMA-30R-WEO
and
WMA-60R-WEO
was
5720
and
6150,
respectively,
whereas the
orded for WMA-30R-WEO and WMA-60R-WEO was 5720 and 6150, respectively,
SIP for the
others
from
1245from
to 2505
The
results
rejuvenated
whereas
the SIP
for ranged
the others
ranged
1245only.
to 2505
only.
The reveal
results that
reveal
that rejumixtures
modified
with
ZycoTherm
had
SIP
values
greater
than
5000
cycles,
indicating
venated mixtures modified with ZycoTherm had SIP values greater than 5000 cycles, that
inZycoTherm-modified
mixtures
have
a
good
resistance
to
stripping
in
the
field.
This
means
dicating that ZycoTherm-modified mixtures have a good resistance to stripping in the
that the antistripping agent improves the stripping resistance of the WEO-rejuvenated
field. This means that the antistripping agent improves the stripping resistance of the
mixture. According to Padhan, et al. [79], antistripping additives considerably enhance the
WEO-rejuvenated mixture. According to Padhan, et al. [79], antistripping additives constripping resistance of the mixes in the water stripping, stability and wheel tracking tests,
siderably enhance the stripping resistance of the mixes in the water stripping, stability
implying that this binder strengthened the contact area at the aggregate–binder contact.
and wheel tracking tests, implying that this binder strengthened the contact area at the
aggregate–binder contact.
7000
6150
5720
6000
SIP
5000
4000
3000
2505
2160
1645
2000
1120
1000
0
1245
Sustainability 2023, 15, 3807
dicating that ZycoTherm-modified mixtures have a good resistance to stripping in the
field. This means that the antistripping agent improves the stripping resistance of the
WEO-rejuvenated mixture. According to Padhan, et al. [79], antistripping additives considerably enhance the stripping resistance of the mixes in the water stripping, stability
23 of
27
and wheel tracking tests, implying that this binder strengthened the contact area at
the
aggregate–binder contact.
7000
6150
5720
6000
SIP
5000
4000
3000
2505
2160
1645
2000
1245
1120
1000
0
Figure 21. Stripping inflection point (SIP) for different mixtures.
Figure 21. Stripping inflection point (SIP) for different mixtures.
4. Conclusions
This study was carried out to investigate the effect of ZycoTherm as a WMA antistripping agent on the performance of WEO-rejuvenated asphalt mixtures. Seven asphalt
binders, including virgin asphalt, were tested. It is known that blending 12% of WEO
and 0.1% ZycoTherm with the RAP binder (30% and 60%) restores the penetration and
softening point to the value of the virgin binder due to the boosted aromatic percentage of
aged asphalt. The following conclusions are drawn:
•
•
•
•
FTIR showed that the water-sensitive functional group (carboxylic acids and Si-OH
compounds) vanished when the WEO-rejuvenated binders were modified with ZycoTherm, indicating that ZycoTherm works adequately as an antistripping agent. TG
analysis also revealed that the additions of ZycoTherm and WEO did not affect the
thermal stability of the blended binders.
The addition of ZycoTherm to rejuvenated mixtures was found to increase the stability
and decrease the flow of mixtures, which indicates a better adhesion and thus enhances
the binder–aggregate mechanical interlocking.
Mixtures containing ZycoTherm have relatively higher ITS, TSR, MR and RMR values.
The decrease in viscosity of the rejuvenated binders modified with ZycoTherm allows
the binder to penetrate the pore on the aggregate external morphology. Furthermore,
lower mixing temperatures in the WMA mixtures lead to less aging and therefore
lower possibility of cracking and moisture intrusion to the binder–aggregate bond
during the conditioning phase.
The results revealed that ZycoTherm has a positive impact on the rutting resistance in
the presence of moisture. This may be attributed to the fact that the modified samples
exhibited a high coating percentage, which impedes water infiltration to disrupt the
binder–aggregate interface.
In conclusion, the study reveals that ZycoTherm improves the physical and mechanical
characteristics of both binders and mixtures. However, the suggested procedure has a few
limitations, which will be addressed in future research. Compared to the benefits of WMA
mixtures incorporating RAP and the great impact of moisture on their performance, it could
be beneficial to examine the field efficiency of these mixtures against moisture damage
and relate it to laboratory findings. The study showed that ZycoTherm improved rutting
and moisture resistances; however, it would be useful to conduct additional research to
assess its low-temperature cracking resistance. Moreover, this study evaluated only one
type and source of asphalt binder; therefore, further research is needed to determine the
influence of RAP source and binder type on moisture susceptibility. In addition, future
Sustainability 2023, 15, 3807
24 of 27
investigation is also necessary to assess the impact of short-term aging and long-term aging
on the performances of the WMA antistripping additive examined in this study.
Author Contributions: Conceptualization, A.E. and M.E.; methodology, A.E., A.M., E.J., Z.A.-S. and
M.E.; software, E.J.; validation, R.P.J. and M.R.H.; formal analysis, A.E. and M.E.; investigation,
Z.A.-S.; resources, A.E. and A.M.; data curation, M.E.; writing—original draft preparation, A.E.;
writing—review and editing, A.E., A.M., E.J., M.R.H. and M.E.; visualization, A.E. and Z.A.-S.;
supervision, R.P.J. and M.R.H.; project administration, A.M. and M.E.; funding acquisition, A.M. and
R.P.J. All authors have read and agreed to the published version of the manuscript.
Funding: This research was funded by the Universiti Teknologi Malaysia (UTM), grant number:
R.J130000.7351.4B703.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: All data used in this research can be provided upon request.
Acknowledgments: The authors express their gratitude to Universiti Teknologi Malaysia for supporting this work. In addition, the support provided by Universiti Malaysia Pahang (PGRS210375)
for this study is highly appreciated.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
El-labbad, E.M.; Heneash, U.; El-Badawy, S.M. Investigation of Waste Electrical Power Plant Oil as a Rejuvenating Agent for
Reclaimed Asphalt Binders and Mixtures. Materials 2022, 15, 4811. [CrossRef] [PubMed]
Saberi, S.S.; Mohamed, A.; Eltwati, A.S. Mechanical and Physical Properties of Recycled Concrete Aggregates for Road Base
Materials. J. Phys. Conf. Ser. 2021, 1973, 012236. [CrossRef]
Maciejewski, K.; Ramiaczek,
˛
P.; Remisova, E. Effects of Short-Term Ageing Temperature on Conventional and High-Temperature
Properties of Paving-Grade Bitumen with Anti-Stripping and WMA Additives. Materials 2021, 14, 6229. [CrossRef] [PubMed]
Zhang, C.; Ren, Q.; Qian, Z.; Wang, X. Evaluating the effects of high RAP content and rejuvenating agents on fatigue performance
of fine aggregate matrix through DMA flexural bending test. Materials 2019, 12, 1508. [CrossRef] [PubMed]
Enieb, M.; Hasan Al-Jumaili, M.A.; Eedan Al-Jameel, H.A.; Eltwati, A.S. Sustainability of using reclaimed asphalt pavement:
Based-reviewed evidence. J. Phys. Conf. Ser. 2021, 1973, 012242. [CrossRef]
Eltwati, A.; Enieb, M.; Ahmeed, S.; Zaid, A.-S.; Mohamed, A. Effects of waste engine oil and crumb rubber rejuvenator on the
performance of 100% RAP binder. J. Innov. Transp. 2022, 3, 8–15. [CrossRef]
Al-Saffar, Z.H.; Yaacob, H.; Katman, H.Y.; Mohd Satar, M.K.; Bilema, M.; Putra Jaya, R.; Eltwati, A.S.; Radeef, H.R. A Review on
the Durability of Recycled Asphalt Mixtures Embraced with Rejuvenators. Sustainability 2021, 13, 8970. [CrossRef]
Al-Saffar, Z.H.; Yaacob, H.; Al Jawahery, M.S.; Yousif, S.T.; Satar, M.K.I.M.; Jaya, R.P.; Radeef, H.R.; Eltwati, A.S.; Shaffie, E.
Extraction and Characterisation of Maltene from Virgin Asphalt as a Potential Rejuvenating Agent. Sustainability 2023, 15, 909.
[CrossRef]
Brasileiro, L.; Moreno-Navarro, F.; Tauste-Martínez, R.; Matos, J.; Rubio-Gámez, M.D. Reclaimed Polymers as Asphalt Binder
Modifiers for More Sustainable Roads: A Review. Sustainability 2019, 11, 646. [CrossRef]
Joumblat, R.; Al Basiouni Al Masri, Z.; Al Khateeb, G.; Elkordi, A.; El Tallis, A.R.; Absi, J. State-of-the-Art Review on Permanent
Deformation Characterization of Asphalt Concrete Pavements. Sustainability 2023, 15, 1166. [CrossRef]
Pasandín, A.R.; Pérez, I.; Gómez-Meijide, B. Performance of High Rap Half-Warm Mix Asphalt. Sustainability 2020, 12, 10240.
[CrossRef]
Jing, F.; Wang, R.; Zhao, R.; Li, C.; Cai, J.; Ding, G.; Wang, Q.; Xie, H. Enhancement of Bonding and Mechanical Performance of
Epoxy Asphalt Bond Coats with Graphene Nanoplatelets. Polymers 2023, 15, 412. [CrossRef] [PubMed]
Shoukat, T.; Yoo, P.J. Rheology of Asphalt Binder Modified with 5W30 Viscosity Grade Waste Engine Oil. Appl. Sci. 2018, 8, 1194.
[CrossRef]
Al-Saffar, Z.H.; Yaacob, H.; Mohd Satar, M.K.I.; Saleem, M.K.; Jaya, R.P.; Lai, C.J.; Shaffie, E. Evaluating the Chemical and
Rheological Attributes of Aged Asphalt: Synergistic Effects of Maltene and Waste Engine Oil Rejuvenators. Arab. J. Sci. Eng. 2020,
45, 8685–8697. [CrossRef]
Wang, F.; Fang, Y.; Chen, Z.; Wei, H. Effect of waste engine oil on asphalt reclaimed properties. AIP Conf. Proc. 2018, 1973, 020012.
[CrossRef]
Su, N.; Xiao, F.; Wang, J.; Cong, L.; Amirkhanian, S. Productions and applications of bio-asphalts—A review. Constr. Build. Mater.
2018, 183, 578–591. [CrossRef]
Jia, X.; Huang, B.; Bowers, B.F.; Zhao, S. Infrared spectra and rheological properties of asphalt cement containing waste engine oil
residues. Constr. Build. Mater. 2014, 50, 683–691. [CrossRef]
Sustainability 2023, 15, 3807
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
25 of 27
Jahanbakhsh, H.; Karimi, M.M.; Naseri, H.; Nejad, F.M. Sustainable asphalt concrete containing high reclaimed asphalt pavements
and recycling agents: Performance assessment, cost analysis, and environmental impact. J. Clean. Prod. 2020, 244, 118837.
[CrossRef]
Eltwati, A.S.; Enieb, M.; Al-Saffar, Z.H.; Mohamed, A. Effect of glass fibers and waste engine oil on the properties of RAP asphalt
concretes. Int. J. Pavement Eng. 2022, 23, 5227–5238. [CrossRef]
Babangida Attahiru, Y.; Mohamed, A.; Eltwati, A.; Burga, A.A.; Ibrahim, A.; Nabade, A.M. Effect of waste cooking oil on warm
mix asphalt block pavement—A comprehensive review. Phys. Chem. Earth Parts A/B/C 2023, 129, 103310. [CrossRef]
Martinez-Soto, A.; Calabi-Floody, A.; Valdes-Vidal, G.; Hucke, A.; Martinez-Toledo, C. Life Cycle Assessment of Natural
Zeolite-Based Warm Mix Asphalt and Reclaimed Asphalt Pavement. Sustainability 2023, 15, 1003. [CrossRef]
Manfro, A.L.; Staub de Melo, J.V.; Villena Del Carpio, J.A.; Broering, W.B. Permanent deformation performance under moisture
effect of an asphalt mixture modified by calcium carbonate nanoparticles. Constr. Build. Mater. 2022, 342, 128087. [CrossRef]
Enieb, M.; Cengizhan, A.; Karahancer, S.; Eltwati, A. Evaluation of Physical-Rheological Properties of Nano Titanium Dioxide
Modified Asphalt Binder and Rutting Resistance of Modified Mixture. Int. J. Pavement Res. Technol. 2022. [CrossRef]
Mirzababaei, P. Effect of zycotherm on moisture susceptibility of Warm Mix Asphalt mixtures prepared with different aggregate
types and gradations. Constr. Build. Mater. 2016, 116, 403–412. [CrossRef]
Caputo, P.; Abe, A.A.; Loise, V.; Porto, M.; Calandra, P.; Angelico, R.; Oliviero Rossi, C. The Role of Additives in Warm Mix
Asphalt Technology: An Insight into Their Mechanisms of Improving an Emerging Technology. Nanomaterials 2020, 10, 1202.
[CrossRef] [PubMed]
Ayazi, M.J.; Moniri, A.; Barghabany, P. Moisture susceptibility of warm mixed-reclaimed asphalt pavement containing Sasobit
and Zycotherm additives. Pet. Sci. Technol. 2017, 35, 890–895. [CrossRef]
Sukhija, M.; Prasad, A.N.; Saboo, N.; Mashaan, N. Assessment of Virgin Binder-Blended Rejuvenators and Antistripping Agents
for Hot Recycled Asphalt Mixture. Int. J. Pavement Res. Technol. 2022. [CrossRef]
Yousefi, A.A.; Haghshenas, H.F.; Shane Underwood, B.; Harvey, J.; Blankenship, P. Performance of warm asphalt mixtures
containing reclaimed asphalt pavement, an anti-stripping agent, and recycling agents: A study using a balanced mix design
approach. Constr. Build. Mater. 2023, 363, 129633. [CrossRef]
Ameri, M.; Vamegh, M.; Chavoshian Naeni, S.F.; Molayem, M. Moisture susceptibility evaluation of asphalt mixtures containing
Evonik, Zycotherm and hydrated lime. Constr. Build. Mater. 2018, 165, 958–965. [CrossRef]
Sani, A.; Mohd Hasan, M.R.; Shariff, K.A.; Jamshidi, A.; Ibrahim, A.H.; Poovaneshvaran, S. Engineering and microscopic
characteristics of natural rubber latex modified binders incorporating silane additive. Int. J. Pavement Eng. 2020, 21, 1874–1883.
[CrossRef]
ASTM D5/D5M-20; Standard Test Method for Penetration of Bituminous Materials. ASTM International: West Conshohocken, PA,
USA, 2020.
ASTM D36/D36M-14; Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus). ASTM International:
West Conshohocken, PA, USA, 2020.
ASTM E1131-08; Standard Test Method for Compositional Analysis by Thermogravimetry. ASTM International: West Conshohocken, PA, USA, 2014.
AASHTO T283; Standard Method of Test for Resistance of Compacted Bituminous Mixture to Moisture Induced Damage.
AASHTO Standards: Washington, DC, USA, 2014.
AASHTO T322; Standard Method of Test for Determining the Creep Compliance and Strength of Hot-Mix Asphalt (HMA) Using
the Indirect Tensile Test Device. AASHTO Standards: Washington, DC, USA, 2011.
ASTM D7369-20; Standard Test Method for Determining the Resilient Modulus of Bituminous Mixtures by Indirect Tension Tes.
ASTM International: West Conshohocken, PA, USA, 2020.
Ameri, M.; Kouchaki, S.; Roshani, H. Laboratory evaluation of the effect of nano-organosilane anti-stripping additive on the
moisture susceptibility of HMA mixtures under freeze–thaw cycles. Constr. Build. Mater. 2013, 48, 1009–1016. [CrossRef]
Witczak, M.W. Specification Criteria for Simple Performance Tests for Rutting NCHRP Rep. 580, Project 9–19; Transportation Research
Board: Washington, DC, USA, 2007; Volume 580.
AASHTO T195; Standard Method of Test for Determining Degree of Particle Coating of Asphalt Mixtures. American Association
of State Highway and Transportation Officials: Washington, DC, USA, 2011.
Eltwati, A.S.; Enieb, M.; Mohamed, A.; Al-Saffar, Z.H.; Al-Jumaili, M.A. A laboratory study of the effect of fiberglass additive on
the behavioural properties of RAP asphalt mixtures. J. Phys. Conf. Ser. 2021, 1973, 012241. [CrossRef]
Mamun, A.; Al-Abdul Wahhab, H. Evaluation of waste engine oil-rejuvenated asphalt concrete mixtures with high RAP content.
Adv. Mater. Sci. Eng. 2018, 2018, 7386256. [CrossRef]
Leng, Z.; Sreeram, A.; Padhan, R.K.; Tan, Z. Value-added application of waste PET based additives in bituminous mixtures
containing high percentage of reclaimed asphalt pavement (RAP). J. Clean. Prod. 2018, 196, 615–625. [CrossRef]
Cong, P.; Chen, B.; Zhao, H. Coupling effects of wasted cooking oil and antioxidant on aging of asphalt binders. Int. J. Pavement
Res. Technol. 2020, 13, 64–74. [CrossRef]
Mannan, U.A.; Ahmad, M.; Tarefder, R.A. Influence of moisture conditioning on healing of asphalt binders. Constr. Build. Mater.
2017, 146, 360–369. [CrossRef]
Sustainability 2023, 15, 3807
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
26 of 27
Eltwati, A.; Al-Saffar, Z.; Mohamed, A.; Rosli Hainin, M.; Elnihum, A.; Enieb, M. Synergistic effect of SBS copolymers and
aromatic oil on the characteristics of asphalt binders and mixtures containing reclaimed asphalt pavement. Constr. Build. Mater.
2022, 327, 127026. [CrossRef]
Pradhan, S.K.; Sahoo, U.C. Influence of softer binder and rejuvenator on bituminous mixtures containing reclaimed asphalt
pavement (RAP) material. Int. J. Trans. Sci. Technol. 2022, 11, 46–59. [CrossRef]
Elkashef, M.; Williams, R.C.; Cochran, E. Thermal stability and evolved gas analysis of rejuvenated reclaimed asphalt pavement
(RAP) bitumen using thermogravimetric analysis–Fourier transform infrared (TG–FTIR). J. Therm. Anal. Calorim. 2018, 131,
865–871. [CrossRef]
Taherkhani, H.; Noorian, F. Comparing the effects of waste engine and cooking oil on the properties of asphalt concrete containing
reclaimed asphalt pavement (RAP). Road Mater. Pavement Des. 2020, 21, 1238–1257. [CrossRef]
Katla, B.; Raju, S.; Waim, A.R.; Danam, V.A. Utilization of Higher Percentages of RAP for Improved Mixture Performance by
Adopting the Process of Fractionation. Int. J. Pavement Res. Technol. 2022, 15, 349–366. [CrossRef]
Pradhan, S.K.; Sahoo, U.C. Evaluation of recycled asphalt mixtures rejuvenated with Madhuca longifolia (Mahua) oil. Int. J.
Pavement Res. Technol. 2021, 14, 43–53. [CrossRef]
El-Shorbagy, A.M.; El-Badawy, S.M.; Gabr, A.R. Investigation of waste oils as rejuvenators of aged bitumen for sustainable
pavement. Constr. Build. Mater. 2019, 220, 228–237. [CrossRef]
Mirzababaei, P.; Moghadas Nejad, F.; Naderi, K. Effect of liquid silane-based anti-stripping additives on rheological properties of
asphalt binder and hot mix asphalt moisture sensitivity. Road Mater. Pavement Des. 2020, 21, 570–585. [CrossRef]
Wang, W.; Shen, A.; Yang, X.; Guo, Y.; Zhao, T. Surface free energy method for evaluating the effects of anti-stripping agents on
the moisture damage to asphalt mixtures. J. Adhes. Sci. Technol. 2020, 34, 1947–1970. [CrossRef]
Chaturabong, P.; Bahia, H.U. Effect of moisture on the cohesion of asphalt mastics and bonding with surface of aggregates. Road
Mater. Pavement Des. 2018, 19, 741–753. [CrossRef]
Ameli, A.; Norouzi, N.; Khabbaz, E.H.; Babagoli, R. Influence of anti stripping agents on performance of binders and asphalt
mixtures containing Crumb Rubber and Styrene-Butadiene-Rubber. Constr. Build. Mater. 2020, 261, 119880. [CrossRef]
Goli, H.; Latifi, M. Evaluation of the effect of moisture on behavior of warm mix asphalt (WMA) mixtures containing recycled
asphalt pavement (RAP). Constr. Build. Mater. 2020, 247, 118526. [CrossRef]
Song, W.; Huang, B.; Shu, X. Influence of warm-mix asphalt technology and rejuvenator on performance of asphalt mixtures
containing 50% reclaimed asphalt pavement. J. Clean. Prod. 2018, 192, 191–198. [CrossRef]
Abed, A.H.; Qasim, Z.I.; Al-Mosawe, H.; Norri, H.H. The effect of hybrid anti-stripping agent with polymer on the moisture
resistance of hot-mix asphalt mixtures. Cogent Eng. 2019, 6, 1659125. [CrossRef]
Mullapudi, R.S.; Karanam, G.D.; Kusam, S.R. Influence of chemical characteristics of RAP binders on the mechanical properties
of binders and mixes. Int. J. Pavement Res. Technol. 2019, 12, 632–637. [CrossRef]
Fernandes, S.R.M.; Silva, H.M.R.D.; Oliveira, J.R.M. Developing enhanced modified bitumens with waste engine oil products
combined with polymers. Constr. Build. Mater. 2018, 160, 714–724. [CrossRef]
Guo, M.; Liu, H.; Jiao, Y.; Mo, L.; Tan, Y.; Wang, D.; Liang, M. Effect of WMA-RAP technology on pavement performance of
asphalt mixture: A state-of-the-art review. J. Clean. Prod. 2020, 266, 121704. [CrossRef]
Li, H.; Zhang, F.; Feng, Z.; Li, W.; Zou, X. Study on waste engine oil and waste cooking oil on performance improvement of aged
asphalt and application in reclaimed asphalt mixture. Constr. Build. Mater. 2021, 276, 122138. [CrossRef]
Khani Sanij, H.; Afkhamy Meybodi, P.; Amiri Hormozaky, M.; Hosseini, S.H.; Olazar, M. Evaluation of performance and moisture
sensitivity of glass-containing warm mix asphalt modified with zycothermTM as an anti-stripping additive. Constr. Build. Mater.
2019, 197, 185–194. [CrossRef]
Eltwati, A.; Mohamed, A.; Hainin, M.R.; Jusli, E.; Enieb, M. Rejuvenation of aged asphalt binders by waste engine oil and SBS
blend: Physical, chemical, and rheological properties of binders and mechanical evaluations of mixtures. Constr. Build. Mater.
2022, 346, 128441. [CrossRef]
Baldi-Sevilla, A.; Montero, M.L.; Aguiar-Moya, J.P.; Loria-Salazar, L.G.; Bhasin, A. Influence of bitumen and aggregate polarity on
interfacial adhesion. Road Mater. Pavement Des. 2017, 18, 304–317. [CrossRef]
Cong, P.; Guo, X.; Ge, W. Effects of moisture on the bonding performance of asphalt-aggregate system. Constr. Build. Mater. 2021,
295, 123667. [CrossRef]
Han, Y.; Jiang, J.; Ni, F.; Dong, Q.; Zhao, X. Effect of cohesive and adhesive parameters on the moisture resistance of thin friction
course (TFC) with varying mix design parameters. Constr. Build. Mater. 2020, 258, 119420. [CrossRef]
Syed, I.A.; Mannan, U.A.; Tarefder, R.A. Comparison of rut performance of asphalt concrete and binder containing warm mix
additives. Int. J. Pavement Res. Technol. 2019, 12, 162–169. [CrossRef]
Fakhri, M.; Hosseini, S.A. Laboratory evaluation of rutting and moisture damage resistance of glass fiber modified warm mix
asphalt incorporating high RAP proportion. Constr. Build. Mater. 2017, 134, 626–640. [CrossRef]
Omar, H.A.; Yusoff, N.I.M.; Mubaraki, M.; Ceylan, H. Effects of moisture damage on asphalt mixtures. J. Traffic Trans. Eng. (Engl.
Ed.) 2020, 7, 600–628. [CrossRef]
Chen, A.; Hu, Z.; Li, M.; Bai, T.; Xie, G.; Zhang, Y.; Li, Y.; Li, C. Investigation on the mechanism and performance of asphalt and
its mixture regenerated by waste engine oil. Constr. Build. Mater. 2021, 313, 125411. [CrossRef]
Sustainability 2023, 15, 3807
72.
73.
74.
75.
76.
77.
78.
79.
27 of 27
Fernandes, S.R.; Silva, H.M.; Oliveira, J.R. Recycled stone mastic asphalt mixtures incorporating high rates of waste materials.
Constr. Build. Mater. 2018, 187, 1–13. [CrossRef]
Ren, S.; Liu, X.; Fan, W.; Qian, C.; Nan, G.; Erkens, S. Investigating the effects of waste oil and styrene-butadiene rubber on
restoring and improving the viscoelastic, compatibility, and aging properties of aged asphalt. Constr. Build. Mater. 2021, 269,
121338. [CrossRef]
Zhang, Y.; Bahia, H.U. Effects of recycling agents (RAs) on rutting resistance and moisture susceptibility of mixtures with high
RAP/RAS content. Constr. Build. Mater. 2021, 270, 121369. [CrossRef]
Lv, Q.; Lu, J.; Tang, X.; Hu, Y.; Yan, C. Evaluation of the moisture resistance of rubberized asphalt using BBS/UTM bonding test,
TSR and HWT test. Constr. Build. Mater. 2022, 340, 127831. [CrossRef]
Zhang, J.; Huang, W.; Zhang, Y.; Yan, C.; Lv, Q.; Guan, W. Evaluation of the terminal blend crumb rubber/SBS composite modified
asphalt. Constr. Build. Mater. 2021, 278, 122377. [CrossRef]
Walubita, L.F.; Fuentes, L.; Prakoso, A.; Rico Pianeta, L.M.; Komba, J.J.; Naik, B. Correlating the HWTT laboratory test data to
field rutting performance of in-service highway sections. Constr. Build. Mater. 2020, 236, 117552. [CrossRef]
Doyle, J.D.; Howard, I.L. Rutting and moisture damage resistance of high reclaimed asphalt pavement warm mixed asphalt:
Loaded wheel tracking vs. conventional methods. Road Mater. Pavement Des. 2013, 14, 148–172. [CrossRef]
Padhan, R.K.; Mohanta, C.; Sreeram, A.; Gupta, A. Rheological evaluation of bitumen modified using antistripping additives
synthesised from waste polyethylene terephthalate (PET). Int. J. Pavement Eng. 2020, 21, 1083–1091. [CrossRef]
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Ahmed Eltwati