1. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
Evaluation of Rutting Performances of Hot Mix
Asphalt Containing Recycled Asphalt Mixes using
Flow Time Test
Darshita Tiwari1, Anoop Patel2
1Department of Civil Engineering, Shri G.S. Institute of Technology & Science Indore (M.P.) India, 452003
2Department of Civil Engineering, Shri G.S. Institute of Technology & Science Indore (M.P.) India, 452003
Abstract: Utilization of recycled asphalt pavement (RAP) has gained worldwide popularity in highway industry recently. Use of RAP in
asphalt mixes can reduce cost of materials (aggregates and bitumen), conserve aggregates and asphalt, save environment, and help solve
the problem of solid waste disposal. However, construction of highways with RAP is not as popular in India as it expected to be due to lack
of laboratory facilities and field performance data. In this study, the objective was to conduct a laboratory investigation of rutting
resistance of hot mix asphalt containing RAP. Two mixes, one without RAP and the other with up to 40% RAP (10%, 20%, 30% and 40%)
were designed in the laboratory using Marshall mix design method. It can be comprehended that using RAP not only reduce the cost of
construction but also increases the characteristics of mixes as it was seen that inclusion of RAP increases rutting performance of a mix.
Overall, the present study would be helpful to characterize mixes containing RAP.
Keyword: recycled asphalt pavement, hot mix asphalt, flow time, rutting resistance.
1. Introduction
methodology is presented in Figure 1. The project started
with materials collection, mix design, and performance
Reclaimed asphalt pavement (RAP) is a material collected
evaluation of mixes in laboratory. The detail discussion on
from deteriorated and structurally deficient flexible
each of the task is presented below.
pavements. The RAP contains aggregates coated with
bitumen. Use of RAP in asphalt mixes can reduce cost of
materials (aggregates and bitumen), conserve aggregates and
asphalt which can help save the environment, and also help
solve the problem of solid waste disposal. 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. However, due to the lack of laboratory facilities
and field performance data, agencies and contractors are not
trained enough to judge the quality of RAP materials and to
design a mix containing RAP. Moreover, non-availability of
standards and specification and variability of RAP, and past
bitter experience with RAP have demotivated many industry
and highway engineers to promote utilization of RAP. It is
expected that aged binder in RAP may produce stiffer mixes,
resulting in lower fatigue and brittle mixes. Many researchers
have reported that addition of RAP results in better rutting
resistance of mixes (Kanishak et al.,). However, limited
Figure 1: Flow Chart of Methodology
studies have been done on evaluation of rutting performances
of mixes containing RAP.
4. Materials Collection
2. Objectives
The aggregates of different sizes: 20 mm and 10 mm down
and stone dust were collected from J.M. Mhatre Infra Private
Study rutting performance of asphalt mixes with and without
Limited. The aggregate was a basaltic rock with dark grey
RAP (up to 40% RAP) using flow time test
colour. The asphalt binder sample of viscosity grade (VG)
was collected from Hindustan Colas Limited. The VG30
3. Methodology
binder is generally used for construction of flexible
pavements in India as per Indian Road Congress
specification. RAP was collected from Indore. This road
In this study, a bituminous concrete (BC) Grade-1 was
needed resurfacing due to potholes and other distresses, and
designed as per MoRTH specification with (0% RAP) and
hence top 40 mm of the pavement was removed by milling.
without (0 to 40%) RAP content. The flow chart of the
Volume 3 Issue 10, October 2014
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Paper ID: OCT14463 1660
Licensed Under Creative Commons Attribution CC BY

2. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
4.1 Mix Design
The Marshall mix design procedure was employed to design
mixture. Materials meet the gradation specification of
MoRTH and all the mixtures were adjusted to keep the
similar aggregate structures after RAP was added, gradation
curves of aggregates is shown in Figure 1and gradation
curves of filler and stone dust is shown in Figure 2 . Table 3
presents the different asphalt contribution from RAP and
virgin asphalt.
Table 1: Asphalt contribution from RAP and virgin
Volume 3 Issue 10, October 2014
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asphalt
RAP
(%)
OBC (%) Virgin Binder
to be added (%)
Binder from
RAP (%)
Binder
Saving (%)
0 5.41 5.41 - -
10 4.89 4.89 0.49 9
20 4.25 4.25 1.12 20.7
30 3.92 3.92 1.61 29.76
40 2.83 2.83 2.26 41.77
OBC= Optimum Bitumen Content, RAP= Reclaimed
Asphalt Pavement
5. Laboratory Performance Tests
Rutting Performance Using Flow Time
Rutting is one of the major distresses in a flexible pavement
which can lead to early failure. The rutting is caused due to
application of repeated loads which results in densification
and lateral plastic flow under the wheel path. The flow time
has been recognized as one of the important tests to evaluate
rutting performance of asphalt mixes. In this test, a static
load of selected magnitude is applied for 10,000 s to a
cylindrical sample of 100 mm diameter and 150 mm height.
The test is generally conducted a higher temperature to
simulate rutting behavior of a pavement. The permanent
deformation is measured with time. The plot of permanent
deformation versus time has three different zones: primary
zone (reflecting initial densification stage), secondary zone
(indicate long time densification), and tertiary zone (shear
failure) which is shown in Figure 2. A flow time is defined
as a time where zone shifts from secondary to tertiary. A
flow time is an indication of rutting performance of a mix. A
higher flow time value indicates stronger mix and vice versa.
The rutting performance of asphalt mixes containing
different percentages of RAP (i.e., 0%, 10%, 20%, 30%, and
40%) were evaluated in the laboratory.
Figure 2: Different Zones of Rutting in Flow Time Test
The samples of 100 mm diameter and 150 mm in height
were prepared in the laboratory using Marshall sample
compactor with target air void in range of 5±1%. The
number of blows was changed accordingly to achieve the
target air voids in the compacted samples. This test was
performed as uniaxial static creep test. Cylindrical samples
were subjected to a constant compressive load of 500 kPa at
a test temperature of 550C for 10,000 seconds. The samples
were kept in water for 2 hours to achieve test temperature
which is shown in Figure 3. The resulting axial strain was
measured as a function of time and numerically
differentiated to calculate the flow time which is defined as
the time corresponding to the minimum rate of change of
axial strain.
Figure 3: Flow time specimen testing
Paper ID: OCT14463 1661

3. International Journal of Science and Research (IJSR)
ISSN (Online): 2319-7064
Impact Factor (2012): 3.358
6. Results and Discussion
The rutting performance of different types of HMA-RAP
mixes is presented in Figure 4. A high value of flow time
indicates a stronger mix, and better rut resistance. The
results show the addition of RAP increases flow time. For
example, addition of 10%, and 20% RAP resulted in an
increase in flow time from 1925 seconds (0% RAP) to
approximately 2250 seconds and 8750 seconds flow time,
respectively. The addition to 30% and 40% RAP resulted in
flow time greater than 10,000 seconds, indicating no sign of
failure of a sample. The increase in rut resistance of a mix
with addition of RAP can be due to the addition of aged and
stiffer binders.
Figure 4: Comparison of Flow Time
7. Summary and Conclusions
The construction of highways with RAP materials is not as
popular in India as it expected to be, due to lack of
laboratory and field performance data. The present study
was undertaken to design and evaluate performance of
bituminous mixes containing 0%, 10%, 20%, 30% and 30%
RAP. The results show that RAP mix is better rut resistance
than a mix without RAP. The results show the addition of
RAP increases flow time. For example, addition of 10%, and
20% RAP resulted in increase in flow time from 1925
seconds (0% RAP) to approximately 2250 seconds and 8750
seconds flow time, respectively. The addition to 30% and
40% RAP resulted in flow time greater than 10,000 seconds,
indicating no sign of failure of a sample. The increase in rut
resistance of a mix with addition of RAP can be due to the
addition of aged and stiffer binders.
8. Recommendations
1. The rutting performance of HMA and WMA mixes
should be evaluated based on the accelerated rutting test
methods, such as Hamburg wheel tracking test
2. The effects of RAP on other laboratory performance
parameters namely, dynamic modulus, creep compliance
should be evaluated.
3. The effects of rejuvenators should be evaluated to use
higher percentages of RAP in the laboratory
4. Overall, a field demonstration project should be carried
out to validate laboratory performance of mixes
containing RAP
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