1. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
Evaluation of Moisture Damage Potential of HMA
and WMA Mixes Containing RAP using Indirect
Tensile Strength Ratio (TSR) Test
DarshitaTiwari1, Anoop Patel2
1SGSITS Indore,
B-412 Shekhar Planet Vijaynagar Indore (M.P.) India 452001
2SGSITS Indore,
10/21 Patel House Y.N. Road Indore (M.P.) India 452003
Abstract: Reclaimed asphalt pavement (RAP) is a material collected from deteriorated and structurally deficient flexible pavements.
The RAP contains aggregates coated with bitumen. Recently, utilization of RAP in asphalt mixes has been gaining worldwide popularity.
Use of RAP in asphalt mixes can reduce cost of materials (aggregates and bitumen), conserve aggregates and asphalt, save environment,
and can solve problems of solid waste disposal. RAP can also increase the resistance of the pavement against the moisture damage
which is proved by this study. This paper evaluated moisture susceptibility hot mix asphalt (HMA) and warm-mix asphalt (WMA)
mixtures containing high percentages (0, 10, 20, 30 & 40%) of reclaimed asphalt pavement (RAP) through laboratory performance test
(Indirect Tensile Strength Test).The laboratory test results indicated that moisture resistance of the pavement increases with the increase
in the RAP percentage and it is also observed that WMA with high percentage of RAP exhibited more moisture susceptibility and better
performance under moisture damage than HMA.
Keywords: Moisture susceptibility; Reclaimed asphalt pavement; Warm mix asphalt; Hot mix asphalt; Tensile strength ratio (TSR).
1. Introduction
Recycling is one of the cost effective and proven
rehabilitation processes for flexible pavements. According to
a survey conducted by National Asphalt Association
(NAPA) in partnership with Federal highway Association
(FHWA), about 86.7 million tons of recycled asphalt
pavement (RAP) was utilized in construction of flexible
pavements in US during 2012. It resulted in a substantial
cost saving due to reuse of aggregates and bitumen. The
primary reason that makes recycling viable is the cost of
bitumen and non-availability of quality aggregates. Thus,
recycling can help in reducing the cost, conserve material,
and reduce the amount of energy required, preservation of
environment and repair existing poor pavement.
RAP was originally added in hot-mix and, sometimes, cold-mix
before WMA technology was introduced in asphalt
industry. Plenty of research was conducted to characterize
the performance of asphalt mixtures containing RAP.
NCHRP Report 452, “Recommended use of reclaimed
asphalt pavement in the Superpave mix design method:
Technician's Manual” [1] showed how RAP could be used in
Superpave System. Performance tests were conducted on the
mixtures containing different RAP contents (0%, 10%, 20%
and 40%). A stiffening effect seemed to happen on high-
RAP mixtures, while the performance behavior of mixtures
containing less RAP was not significantly different from
virgin mixtures [1]. The moisture damage potential of
recycled mixes can be done by indirect tensile strength. Ali
et al. (2012) evaluated performance of asphalt mixes with
different percentage of RAP (0%, 30%, 40%, and 50%)
using ITS test for samples prepared at 7±0.5% air void. It
was reported that TSR remains similar to that of 0% RAP up
to 40%, and minimal TSR value was found with addition of
50% RAP, indicating that higher percentage of RAP may
lead to moisture damage.
Rodriguez et al. (2008) evaluated the performance of 0%,
10%, 15%, 20%, 25% and 40% RAP mixes using ITS test
for two different binders (PG58-34 and PG58-34) at -10ºC
and -24ºC. They reported that for PG58-34 binder, TSR
increased for 20% RAP but decreases for 40% RAP,
however, for PG58-28 binder, TSR increased linearly with
increase in RAP content.
Zhao et al. (2012) evaluated moisture susceptibility test on
both HMA and WMA mixes containing RAP (HMA 0% &
30% and WMA 0%, 30%, 40% & 50%) by compacting the
specimens at 7±0.5% air void. The TSR values of WMA
mixes containing RAP (30%, 40% and 50%) were higher
than that of virgin WMA mix, which indicated that WMA
containing high percentages of RAP would exhibit a good
resistance to moisture damage. HMA containing 30% RAP
had a higher TSR value than the HMA mixture without
RAP.
2. Objectives and Scope
The objective of the study is to evaluate and compare the
performance of HMA and WMA containing high
percentages of RAP through Indirect tensile strength test.
HMA and WMA mixtures contained up to 40% RAP.
3. Laboratory Experiments
3.1 Materials
Viscosity grade (VG) 30 bitumen was selected in the study.
The virgin aggregates of different size of aggregates: 20 mm
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2. International Journal of Science and Research (IJSR)
and 10 mm down and stone dust were used
RAP material was collected from Indore
mm of the pavement. The mix used in
pavement was bituminous concrete (BC)
2 years back with VG-30 grade bitumen.
as filler in asphalt mixes. In addition, lime
stripping agent and enhances moisture damage
asphalt mixes. Table 1 and Table 2 show
bitumen VG 30 and gradation of aggregate
in this study. The
by milling top 40
top layer of the
constructed almost
Lime is preferred
works as an anti-damage
the test results of
aggregates respectively.
Table 1: Test Results of Bitumen
Test Test Result Limiting Value
Penetration at 25°C,
100 gm, 5 sec. 64.5 60 to 70
Softening Point, °C 45.2 45 to 55
Ductility at 27 °C,
cm 88 Min 70
ISSN (Online): 2319-7064
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potential of
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Absolute viscosity at
60°C, Poises 2943 32400 - 3600
Kinematic viscosity
at 135°C, cst 492 Min 300
Table 2 Gradation of Aggregates
Sieve
size (mm)
Passing (%)
20
mm
10
mm
Stone
Dust
Filler
Lime
RAP Limit
MoRTH
limit
26.5 100 100 100
19 88.3 100 94.3
13.2 34.9 100 100 100 72.5
9.5 8.0 71.4 100 100 55.7
4.75 5.3 13.3 91.7 100 45.5
2.36 3.1 6.7 77.1 100 32.7
1.18 2.5 4.7 57.9 100 22.1
0.6 1.9 2.9 42.8 99.1 18.3
0.3 1.5 2.2 29.9 98.3 13.8
0.15 0.7 1.1 19.5 97.7 8.3
0.075 0.2 0.1 6.8 91.8 3.5
Figure 1: Gradation Curves of Aggregates
Volume 3 Issue 10, October 2014
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VG 30
Test Method
IS 1203 : 1978
IS 1205 : 1978
IS 1208 :1978
IS 1206 (Part
2):1978
IS 1206 (Part
3):1978
Specified by
(Upper
limit-Lower limit)
100-100
90-95
59-69
52-62
35-45
28-36
20-27
15-21
10-15
5-9
2-5
Figure 2: Gradation Curves
3.2 Mix Design
The Marshall mix design procedure
mixture. Materials meet the
MoRTH and all the mixtures
similar aggregate structures after
curves of aggregates is shown
curves of filler and stone dust
presents the different asphalt
virgin asphalt.
Table 3: Asphalt contribution
RAP
(%)
OBC
(%)
of Lime filler and Stone dust
Virgin Binder
be added (%)
0 5.41 5.41
10 4.89 4.89
20 4.25 4.25
30 3.92 3.92
40 2.83 2.83
OBC= Optimum Bitumen
Asphalt Pavement
3.3 Sample preparation for HMA
The specimen of thickness 63.5
mm were prepared using
Approximately 1200 gm aggregates
temperature in range of 170-190°C.
at 150°C, and then mixed with
Thereafter, the mix was compacte
both sides to target air voids in
rammer is 457.2 mm, weight
mm.
3.4 Sample Preparation for WMA
The specimen of thickness 63.5
mm were prepared using
Approximately 1200 gm aggregates
temperature in range of 130-
with additive was heated at
aggregates at 120° to 140°C.
compacted by applying 100 to
target air voids in range of 5±1%.
was employed to design
gradation specification of
were adjusted to keep the
RAP was added, gradation
in Figure 1and gradation
is shown in Figure 2 . Table 3
contribution from RAP and
from RAP and virgin asphalt
to
Binder from
RAP (%)
Binder
Saving (%)
- -
0.49 9
1.12 20.7
1.61 29.76
2.26 41.77
Content, RAP= Reclaimed
± 3 mm and diameter of 100
Marshall sample compactor.
and filler were heated at
The bitumen was heated
aggregates at 160° to 170°C.
compacted by applying 75 blows on
range of 5±1%.Height of the
is 4.5 kg and diameter is 98.5
± 3mm and diameter of 100
Marshall sample compactor.
and filler were heated at
-150°C.The modified bitumen
140°C and then mixed with
Thereafter, the mix was
130 blows on both sides to
Paper ID: OCT14462 1657

3. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
3.5 Tests for Moisture Susceptibility
This test is conducted by applying a compressive load at a
rate of 50.8 mm/min on a cylindrical sample as shown in
Figure 3. Two different types of samples (i) conditioned (ii)
unconditioned, were prepared. The conditioned samples
were placed in water bath maintained at a temperature of
60°C for 24 hour prior to testing. Similarly, unconditioned
sample were kept in water at 60°C for 30-40 min prior to
testing. Figure 1 shows testing of specimen. The ratio of
failure load of conditioned and unconditioned samples is
reported as a TSR value. A high TSR value indicates a good
water resistance mix and vice versa. The MORTH
recommends a minimum TSR value of 0.80 for a mix to
ensure moisture resistant mix. However, this limit might not
work for HMA-RAP and WMA-RAP mixes, hence, a
comparison of TSR value for WMA and HMA mixes were
carried out in this study. The indirect tensile strength (S) is
determined by Eq. (1). The TSR is calculated by Eq. (2).
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S ൌ
2000 P
πDt
ሺ1ሻ
Where,
S= indirect tensile strength, kPa
P = Peak load at failure, N
t = thickness of sample, mm
D = diameter of sample, mm
TSR ൌ
N
P
x100 ሺ2ሻ
Where,
N is the average indirect tensile strength of conditioned
specimens, N
P is the average indirect tensile strength of unconditioned
specimens, N
4. Results and Discussion
The indirect tensile strength test was conducted on both
types of samples and their failure load was recorded as
tensile strength. The ratio of failure load for conditioned and
unconditioned samples are reported at TSR. TSR Value for
Conditioned and Unconditioned Samples are shown in
Figure 4.
Figure 4: TSR results of HMA and WMA mixes
4.1 Performance of HMA-RAP Mixes
The TSR value of virgin mix without RAP was found to be
86.1% which is higher than the minimum required value of
80%, and hence, the mix passes moisture resistance test.
This can be because of addition of lime as filler which acts
as an anti-stripping agent and hence, resulting in higher TSR
value. The TSR value increases with an increase in RAP for
up to 30%, and then it starts decreasing. The addition of
40% RAP shows TSR value of 84.2% compared to 86.1%
for a virgin mix, indicating that addition of higher
percentage of RAP results in decrease in moisture damage
potential. While comparing TSR value for different
percentage of RAP, it was found that it increases with up to
20% RAP and then, it decreases, indicating that higher RAP
content may result in a poor mix as far as moisture damage
potential is concerned. Therefore, a careful attention should
be given for designing mix with higher percentage of RAP.
4.2 Performance of WMA-RAP Mixes
Compared with 0% RAP, the TSR value increases with an
increase in RAP for up to 30%, and on further RAP addition
the TSR value decreases. For example, addition of 10%,
20%, and 30% RAP resulted in 88.2%, 90.1%, and 92.2%
TSR values respectively, compared to 84.1%, TSR value for
0% RAP. The addition of 40% RAP showed similar TSR
value as a virgin mix. It should be noted that addition of
different percentages of RAP satisfies the minimum
requirement of 80% as per MORTH specification. While
comparing TSR value for different percentage of RAP, it
was found that it increases with up to 30% RAP and then it
starts decreasing, indicating that a higher percentage of RAP
results in decrease in moisture damage potential.
4.3 Comparison of HMA-RAP and WMA-RAP Mixes
TSR value for both the mixes was higher than the minimum
required value of 80%, and hence, the mix passes moisture
resistance test. The TSR value of HMA-RAP mixes were
found to be higher compared to WMA-RAP mixes up to
20% RAP. The addition of higher percentage of RAP (i.e.,
30% and 40%) resulted in a similar value of TSR for HMA
and WMA mixes. The results show that addition of RAP to
HMA is significantly effective compared to addition of RAP
to WMA mixes as shown in equality line plot Figure5.
Paper ID: OCT14462 1658

4. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
Figure 5: TSR Value for Different Percentage of RAP with
HMA and WMA Mixes
5. Conclusions
The following conclusions can be drawn from the results
and discussions presented in this study:
a. The TSR value of virgin mix without RAP was found to
be higher than the minimum required value of 80%, and
hence, the mix passes moisture resistance test.
b. The TSR value increases with an increase in RAP for up
to 20%, and it decreases on further addition of RAP.
c. For WMA-RAP mix, comparison with 0% RAP, the TSR
value increases with an increase in RAP for up to 30%,
and it decreases on further addition of RAP. The addition
of 40% RAP showed similar TSR value as a virgin mix. It
should be noted that addition of different percentages of
RAP satisfies the minimum requirement of 80% as per
MORTH specification.
d. The TSR value of HMA-RAP mixes were found to be
higher compared to WMA-RAP mixes up to 20% RAP.
The addition of higher percentage of RAP (i.e., 30% and
40%) resulted in a similar value of TSR for HMA and
WMA mixes. The results show that addition of RAP to
HMA is significantly effective compared to addition of
RAP to WMA mixes.
e. Incorporation of RAP (Up to certain limit i.e. 30% in this
study) in the mix not only saves natural resources
(Aggregate and Bitumen) but also provides greater tensile
strength than virgin mixes.
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