Development of polymer modified asphalt using filler

Abstract

The modified asphalt is used to improve the performance of pavement when traffic loads are applied with changing environmental conditions. In this study, the bitumen was modified by adding Low Density Polyethylene as such as 2%, 4%, 6% and 8% of total bitumen content. The modification of bitumen was analysed under Fourier Transform Infrared Spectroscopy. These physical properties of modified bitumen samples were also investigated through conventional laboratories tests as such penetration test, softening point test and ductility test. The burning limestone, paddy husk ash and rubber dust were used as trial material to modify the asphalt with 1%, 2%, 3%, 4% and 5% of total aggregate content and Marshall Tests of asphalt samples were conducted with 4.6% bitumen content. The 3.2% of burning limestone was preferred to prepare for the asphalt mixture with optimum 6% Low Density Polyethylene content of modified bitumen. The Marshall Test was conducted to obtain the physical properties of modified asphalt mixture. The adhesion between aggregates and bitumen was analysed with bond mechanism which was confirmed that modified asphalt with burning limestone filler would be to increase the durability of pavements.

Full text

Development of polymer modified asphalt using filler
S.Kajugaran, V.S.C Weragoda
Department of Materials Science & Engineering
University of Moratuwa
Colombo, Sri Lanka
Abstract— The modified asphalt is used to improve the
performance of pavement when traffic loads are applied with
changing environmental conditions. In this study, the bitumen
was modified by adding Low Density Polyethylene as such as
2%, 4%, 6% and 8% of total bitumen content. The
modification of bitumen was analysed under Fourier
Transform Infrared Spectroscopy. These physical properties of
modified bitumen samples were also investigated through
conventional laboratories tests as such penetration test,
softening point test and ductility test. The burning limestone,
paddy husk ash and rubber dust were used as trial material to
modify the asphalt with 1%, 2%, 3%, 4% and 5% of total
aggregate content and Marshall Tests of asphalt samples were
conducted with 4.6% bitumen content. The 3.2% of burning
limestone was preferred to prepare for the asphalt mixture
with optimum 6% Low Density Polyethylene content of
modified bitumen. The Marshall Test was conducted to obtain
the physical properties of modified asphalt mixture. The
adhesion between aggregates and bitumen was analysed with
bond mechanism which was confirmed that modified asphalt
with burning limestone filler would be to increase the
durability of pavements.
Keywords—polymer, modification, asphalt, filler
I.I
NTRODUCTION
The asphalt materials are mainly considered in designing
the pavements of which the quality is expected to reduce the
maintenance cost and increase the durability. The bitumen
and asphalt were modified by various types of modifiers
from nineteenth century to reduce undesirable properties or
to improve the performance of pavement. This study
analyses on two types of modifiers and identify their
behaviour in performance of pavement. Those modifiers are
fillers and polymer materials which are added with asphalt
mixture and bitumen. The bitumen has multiphase systems,
which are phase rich in polymer and phase rich in
asphaltenes. It is not absorbed by polymer, so easily it can
be blended with polymers and they can show good
mechanical/rheological properties of viscoelastic materials.
At most of times, the failures of asphalt pavements can be
investigated through adhesive properties of bitumen and
aggregates. The filler materials are used to improve the
physical and chemical characteristics of asphalt
[1]. The
basic test results indicated that the addition of polyethylene
to bitumen reduces the penetration and ductility, whereas
increase in softening point and specific gravity and 5% of
polyethylene is recommended for good performance [2].
Sensitivity of bitumen changes with temperature which
causes most frequent problems of road pavement such as
rutting, fatigue cracking and thermal cracking. The
properties of bitumen can be improved by adding different
modifiers as such as mineral and polymeric materials
[3]
[4]. The results of laboratory tests have shown that filler
modifiers use to improve the mechanical properties of
paving mixture in reduction of distress factors and
increasing expected pavement life
[5].
II.
M
ECHANISM OF ADHESIVE BOND
The bitumen and aggregate adhesion can be explained by
using boundary layers theory, mechanical theory, chemical
theory, electrostatic theory and thermodynamic theory.
Many researches investigate about bitumen-aggregate
adhesion based on presence of water. The applications of
adhesion mechanisms were simply explained by controlling
properties of bitumen and aggregates surface forces
[6]. The
weak boundary layers theory is used to explain the failure of
adhesion bonds due to creation of low cohesive strength in
interphase region
[6]. The mechanical theory most involves
gripping of adhesive into pores and cavities of surface in
macroscopic scale
[7]. Mostly, the carboxylic acids play as
main role in strongly absorption
[8]
.
The carboxylic acids of
bitumen react with siliceous aggregate, but it is easily
displaced by water. When bonds achieve maximum strength
the aggregate surface groups act as strong base and organic
groups act as strong acid
[9]. The thermodynamic studies
involve on intermolecular forces and surface free energies
which are minimized from orientation of polar molecules of
bitumen [10]/[12]. The point of zero charge (PZC) also use
in electrophoreses to measure the charge of particles
[13],[14]. The lime stone aggregates provided good
adhesive properties with bitumen
[14].
III.C
OST EFFECTIVENESS OF POLYMER MODIFIED BITUMEN
Modified bitumen can play on cost component of hot
asphalt mix production. Mostly, the cost per ton of polymer
modified asphalt would be 50% to 80% higher than neat
asphalt concrete [15]. When modified bitumen is used for
road construction the performance of pavement can be
increased and durability would be improved with lower
maintenance cost. Generally, type of the modification will
affect the cost of modified asphalt production. The Low
978-1-5090-0645-8/16/$31.00 ©2016 IEEE

Density Polyethylene investigated in this research can be
sourced from waste with significant cost is reduction.
IV.E
XPERIMENTAL
A. Materials & methods
The 60/70 grade bitumen was modified by Low Density
Polyethylene (LDPE) such as 2%, 4%, 6% and 8% of
bitumen content which samples were experimented by
softening point test (ASTM D-36), penetration test (ASTM
D-5), ductility test (ASTM D-113) and specific gravity test.
The optimum LDPE % was preferred to bitumen
modification which bitumen was investigated with suitable
filler materials. Burning limestone, paddy husk ash and
wastage rubber dust were used as filler materials for trail
Marshall Test of asphalt.
B. Mechanical sieve analysis of fillers
The sizes of aggregates and fillers were measured by
using mechanical sieve analysis in dry condition and results
of size distribution of total aggregates were corrected to
according specification by matching mix proportions.
Finally, well-graded aggregates grading was obtained for
each set of mix design samples.
C. Fourier Transform Infrared Spectroscopy
The samples of 2%, 4%, 6% and 8% low density
polyethylene modified bitumen were analysed under Fourier
Transform Infrared Spectroscopy (FTIR). The chemical
characteristics of modified bitumen were analysed by
spectrum of FTIR. It was used to confirm the modification
of bitumen also.
D. Marshall Test
The Marshall design is used to find the optimum binder
content in a mix where the aggregate grading and type of
bituminous binder is predetermined. Firstly, aggregates size
distribution and type of binder was chosen according to type
of bituminous mix was being designed. The series of 2 test
specimens were prepared with vary binder content for other
series in 0.5% intervals from 3.5% to 5.5%. Then, Marshall
Test was carried out on each test specimen by using neat
bitumen and polymer modified bitumen as a binder of
mixture. The physical properties of asphalt was analysed
from obtaining results. After initial process, the optimum
binder content was selected and it was used as constant
binder content for another Marshall Mix design with
changing filler content. The burning limestone, paddy husk
ash and rubber dust were used as trail filler materials with
replacing 1%,2%,3%,4% and 5% of aggregates content for
each set of Marshall design. The void mineral aggregates,
air voids, stability, flow and unit weight were analysed
based on results of Marshall Test. Then, the optimum filler
material percentage was mixed with aggregates which were
used for Marshall Mix design of polymer modified bitumen.
Finally, the physical properties of asphalt concrete as such
stability, air voids, voids in mineral aggregates and flow
were analysed by using results of Marshall Tests.
V.R
ESULTS AND
D
ISCUSSION
A. Results conventional tests and Mechanical sieve analysis
for fillers
The results of conventional bitumen tests such as
penetration, softening point, ductility and specific gravity
were shown for modified bitumen samples in
TABLE 1
. The
softening point of bitumen was increased and penetration of
bitumen was reduced by using low density polyethylene.
The better properties were shown in 6% of modifier sample
which is recommended for bitumen modification. When the
polyethylene was added with bitumen phase at high
temperature the lighter parts of bitumen as such oils were
absorbed and asphalt particles were expanded in polymer
network. The hardness and elasticity of bitumen was
confirmed by this manner, but ductility of modified bitumen
was reduced by adding polyethylene. The reason is for that
tough and stiff behaviour of plastomer materials.
The mechanical sieve analysis was done for aggregates and
filler materials to determine the grading line for production
of asphalt mixture. The results of mechanical sieve analysis
for fillers are shown by Fig .1. The mechanical sieve
analysis was done for aggregates and filler materials to
determine the grading line for production of asphalt mixture.
The results of mechanical sieve analysis for fillers are
shown by Fig .1. The paddy husk ash was very fine
materials which could be passed 39.8% of total weight
through 75µm sieve. The burning lime stone also was fine
materials, but the size of rubber dust was not fines because
it was got as directly wastage materials from rubber
production industry.
TABLE I.
Results on conventional bitumen tests
LDPE % Softening point (⁰C) Penetration (mm) Ductility (cm) Specific gravity
0 50 66 121 1.010
2 53 54 85 0.998
4 55 49 76 0.992
6 60 43 60 0.990
8 76 31 39 0.989

0
10
20
30
40
50
60
70
80
90
100
0.01 0.1 1 10 100
Percentage Passing
Sieve Size (mm)
Burning lime Paddy husk ash Rubber dust
Fig. 1.
Percentage passing value of fillers Vs Sieve size
B. Fourier Transform of Infra Spectroscopy test results
Fig. 2 shows that chemical properties of modified
bitumen could be changed through increasing number of C-
H bonds and hydro carbons structures. The modification of
bitumen was confirmed by FTIR analysis which was used to
identify the wave number of molecular bonds as such C-H
stretch, bend and rock of alkanes and aromatics. Mainly, the
increasing content of polyethylene involved in 2950cm-1-
2800cm-1 and 1450cm-1-1400cm-1 wave number range.
100015002000250030003500
Wavenumber cm-1
20 30 40 50 60 70 80 90 100
Transmit tance [%]
Fig. 2. FTIR results on modified bitumen
8% LDPE
6% LDPE
4% LDPE
2% LDPE 0% LDPE

C. Marshall Test results
Firstly, the Marshall Tests were done by using neat
bitumen and polymer modified bitumen as a binder of each
samples set. When neat bitumen was used for asphalt
production they were considered as reference specimen.
Fig 3. Voids in mineral aggregates% Vs Binder%
Fig. 4. Air voids% Vs Binder%
Fig. 5. Stability Vs Binder%
Fig. 6. Flow Vs Binder%
The voids in mineral aggregates and air voids were
increased when polymer modified bitumen was used as a
binder. Those results are shown by Fig. 3 and Fig. 4. These
undesired properties can be reduced by using filler materials.
Fig. 5 and Fig. 6 show the results of stability and flow of
Marshall Test for polymer modified asphalt and normal
asphalt. Those properties were enhanced in polymer modified
asphalt.
The optimum binder content as such 4.6 percentage was
chosen from above results of Marshall Test which satisfied
requirements of Institute for Construction Training And
Development (ICTAD) specifications. After this process, the
Marshall Mix design was carried out with changing filler
content. The burning limestone, paddy husk ash and wastage
rubber dust were used as trail filler materials.
14
15
16
17
18
19
20
21
22
012345
Voids in Mineral
Aggregates%
Filler%
Burning
lime
Paddy ash
Rubber
dust
Fig. 7. Voids in mineral aggregates Vs Filler %
1.8
2.8
3.8
4.8
5.8
6.8
7.8
8.8
9.8
10 .8
11 .8
12 .8
13 .8
012345
Sta bility kN
Filler%
Burnin g
lime
Paddy ash
Rubber
dust
Fig. 8. Stability Vs Filler%
3
4
5
6
7
8
9
10
11
12
13
012345
Air voids%
Filler%
Burning lime
Paddy ash
Rubber dust
Fig. 9. Air voids Vs Filler%
2
3
4
5
6
7
8
9
10
3.5 4 4. 5 5 5. 5
Air vo ids%
Bit umen %
Polyme r
asphalt mix
Referen ce
8.6
9.4
10 .2
11
11 .8
12 .6
13 .4
14 .2
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Sta bility kN
Bit umen%
Polyme r
asphalt mix
Refe rence
15. 2
15. 4
15. 6
15. 8
16
16. 2
16. 4
16. 6
16. 8
17
17. 2
17. 4
17. 6
17. 8
3.5 4 4. 5 5 5.5
Voids in mineral
aggregates%
Bit umen%
Polyme r
asphalt mix
Referen ce
6.8
7.3
7.8
8.3
8.8
9.3
9.8
10. 3
10. 8
11. 3
11. 8
12. 3
3.5 4 4. 5 5 5. 5
Flow (mm)
Bit umen%
Polyme r
asphalt mix
Referen ce

6
8
10
12
14
16
18
20
22
24
012345
Flow (mm)
Filler%
Burning
lime
Paddy ash
Rubber
dust
Fig. 9. Flow Vs Filler%
2.1
2.13
2.16
2.19
2.22
2.25
2.28
2.31
2.34
2.37
2.4
2.43
2.46
2.49
012345
Unit specific weight(g/cc)
Filler%
Burning
lime
Paddy ash
Rubber dust
Fig. 10. Unit specific weight Vs Filler%
Fig. 8 and Fig. 9 illustrate air voids in mixture and the
voids in mineral aggregates. The voids percentage of asphalt
mixture was increased by adding paddy husk ash and rubber
dust which nature was not participated to improve the better
properties of asphalt concrete. But burning limestone showed
better properties in voids in mineral aggregates and air voids
in mixture. Fig. 10 shows that stability was enhanced in
burning lime stone filler asphalt mixture. Figure 11 and Fig.
12 show the flow characteristic and unit weight of asphalt
mixture with changing filler content. The unit weight of
asphalt mixture was reduced in rubber dust asphalt, because
specific gravity of filler materials can play with unit weight of
asphalt concrete. The 3.2% burning limestone was selected as
good filler material of asphalt concrete based on results of
high stability, low air voids and low voids in mineral
aggregates.
Generally, the burning lime induces basis nature and paddy
husk ash induces small acidic nature. But bitumen show little
range of acidic characteristic. That’s why; the burning
limestone establishes good bond properties between bitumen
and aggregates [9],[12]. The mechanical sieve analysis can
play in this manner. But, the grading line of combined
aggregates was kept as same for all samples of asphalt
mixture.
Finally, the selected filler material was used for asphalt
production with polymer modified bitumen. The neat bitumen
also was investigated through Marshall Test with using 3.2%
burning limestone filler. The physical characteristics of all
asphalt samples were analysed under Marshall Test.
15.2
15.4
15.6
15.8
16
16.2
16.4
16.6
16.8
17
17.2
17.4
17.6
17.8
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Voids in mineral aggregates%
Bitumen%
Burning lime
filler asphalt
mix
Polymer
asphalt mix
(Burning
lime+Polymer)
asphalt mix
Reference
Fig. 11. Voids in mineral aggregates% Vs Bitumen%
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
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Air voids%
Bitumen%
Burning lime
filler asphalt
mix
Polymer
asphalt mix
(Burning
lime+Polymer)
asphalt mix
Reference
Fig. 12. Air voids% Vs Bitumen%
Fig. 13. Stability Vs Bitumen%
6.8
7.3
7.8
8.3
8.8
9.3
9.8
10.3
10.8
11.3
11.8
12.3
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Flow (mm)
Bitumen%
Burning lime
filler asphalt
mix
Polymer
asphalt mix
(Burning
lime+Polymer
) asphalt mix
Reference
Fig. 14. Flow Vs Bitumen%
8.6
9.4
10. 2
11
11. 8
12. 6
13. 4
14. 2
15
15. 8
16. 6
17. 4
18. 2
3.5 4 4. 5 5 5. 5
Sta bility kN
Bit umen %
Burning lime
filler a sphalt
mix
Polyme r
asphalt mix
(Burning
lime+Polymer)
asphalt mix
Refe rence

Fig. 15. Unit specific weight Vs Bitumen%
Generally, low voids in mineral aggregates should be
chosen for better design criteria, but it should be satisfied
minimum range. The air voids and voids in mineral aggregates
are shown in Fig. 13 and Fig. 14. The voids for burning
limestone filler asphalt was lower than polymer modified
asphalt which could be enhanced by adding filler materials.
Fig. 15 shows that stability was also very much improved in
polymer modified asphalt by using burning limestone filler
and Fig. 16 illustrates the flow which also shows small
variations with reference sample. Fig. 17 shows that unit
weight was increased through addition of filler in polymer
modified asphalt which could not significantly affect the
properties of asphalt.
When aggregates were mixed with bitumen, the chemical
and physical properties of aggregates were enhanced through
adding burning limestone filler. The effectiveness of
mechanism for adhesive bond between aggregates and
bitumen was improved by increasing surface texture and
roughness, positive charge density, chemical reactivity and
surface energy of aggregates. The strong basis nature and
better surface texture of burning limestone and small acidic
nature of bitumen can play with adhesion of aggregates and
bitumen. The strength of bitumen at elevated temperature was
increased by using polyethylene. Above criteria was
confirmed by high stability, low voids mineral aggregates and
low air voids of polymer modified asphalt. Generally, the
crack initiation and propagation can induce at intersection
between two adhesive surfaces in composites materials. This
phenomenon is same for asphalt composites. The adhesive of
bitumen-aggregates intersection was improved by burning
limestone filler in polymer modified asphalt.
VI.
C
ONCLUSIONS AND RECOMMENDATIONS
Based on the results from experimental studies, the
following conclusions and recommendations can be drawn.
 The plastomer is recommended for improving strength of
bitumen at high temperature, but elastic and adhesive
properties drop from their default stage.
 The Stability and air voids would be enhanced in polymer
modified asphalt by adding burning limestone.
 The failure due to crack propagation of pavement would be
minimized through improving adhesive properties of
aggregates-bitumen interface.
 The usage of waste LDPE helps clean environment
through removing garbage of polymer waste products.
A
CKNOWLEDGMENT
We gratefully acknowledge to Dr.HLDMA.Judith, the
Director of Research & Development Division of RDA for
their kind guidance.
R
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2.3 5
2.3 6
2.3 7
2.3 8
2.3 9
2.4
2.4 1
2.4 2
2.4 3
2.4 4
2.4 5
2.4 6
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Unit specific weight
Bit umen %
Burn ing
lime filler
asphalt mix
Polyme r
asphalt mix
(Burning
lime+Poly
mer)
asphalt mix
Refe rence