International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 332-340, Article ID: IJCIET_10_04_035
Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=10&IType=04
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
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A STUDY ON FRACTIONAL REPLACEMENT
OF BITUMEN WITH CRUMB RUBBER
Shaurya Sharma
M.Tech. Transportation Engineering, Chandigarh University, Mohali-140413, Punjab, India.
Dr. Amit Goel
Professor, Department of Civil Engineering, Chandigarh University, Mohali 140413, Punjab,
India
ABSTRACT
The main aim of this study was to determine an alternative for bitumen which will
satisfy the physical and binding properties of bitumen in terms of strength, endurance,
and flexibility. The asphalt market is looking for alternative sustainable binders that
can (fractionally) replace the bitumen in terms of environmental sustainability and
which may also augment the availability of binders. In this research study, crumb
rubber has been consumed in bituminous mixes and its optimum content percentage is
found, the crumb rubber is used in powdered form and that amount has been replaced
from the quantity of bitumen. Standard Marshal Mix design and Penetration test and
Ductility test were performed. The various percentages of crumb rubber (from 2% to
10% by the weight of bitumen) were used to prepare the samples, with optimum value
of bitumen content (5%). It was observed that crumb rubber at 6% (by weight of
bitumen) and at 5% Optimum Bitumen Content came out to be optimum percentage of
crumb rubber. The test results shows that stability of the modified bitumen mix was
increased as compared to the plain bitumen mix. The physical properties of modified
bitumen were also improved, with the help of penetration test it was observed that the
modified bitumen was harder consistency and was less flexible as per ductility test.
Keywords: Bitumen, Crumb Rubber, Marshal Properties, Penetration test, Ductility
test
Cite this Article: Shaurya Sharma and Dr. Amit Goel, a Study on Fractional
Replacement of Bitumen with Crumb Rubber, International Journal of Civil
Engineering and Technology, 10(04), 2019, pp. 332-340
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Shaurya Sharma and Dr. Amit Goel
1. INTRODUCTION
The paving of flexible pavement comprises of a sizeable part of bitumen and mixing it with
aggregate. Crumb rubber is available in large quantities and is procured from recycled rubber
of waste automobiles tires. The generation of waste tire has become a major concern as they
not only create congestions in our landfills but also effects our health and environment
associated with their disposal. Therefore their use in the modification of bitumen will not only
augment the availability of bitumen but also helps in incrementing the properties of plain
bitumen and provides a better way of disposal of waste tires. By using crumb rubber in the
construction of road will be beneficial economically as well as environmentally. The use of
crumb rubber gives better strength and durability to the road. The size of crumb rubber used in
the sample preparation was taken to be 300µm-150µm.The gradation of aggregate was taken
according to the norms of IS: 107-2386 Part 1 (Wet gradation method) and specification of
Ministry of road transport and highway (MORTH, 2013) for a layer thickness of 50 mm and
nominal aggregate size of 19 mm. The calculation of the optimum value of bitumen and crumb
rubber are found with the help of Marshall Test, to determine the values of Marshal Parameters
(stability, flow value) and Volumetric Parameters (voids in mineral aggregates (VMA), voids
filled with bitumen (VFB) and air content (VA).
2. MATERIALS AND METHODS
The bituminous blend samples were formed using coarse and fine aggregates. The gradation of
aggregate was taken according to the norms of IS: 107-2386 Part 1 (Wet gradation method)
(Table 1). Moisture Content, Impact Value, Flakiness Index, Elongation Index were tasted
according to the Indian standards (Table 2). The specific gravities of coarse and fine aggregates
was found out to be 2.6 and 2.55, respectively. The specific gravity of stone dust was found
out to be 2.42.
Table 1. Gradation of aggregate as per MORTH specifications
Sieve size
Passing %
% Quantity of aggregate
26.5 mm
19 mm
13.2 mm
9.5 mm
4.75 mm
2.36 mm
1.18 mm
600 µm
300 µm
150 µm
75 µm
filler
100
90-100
59-79
52-72
35-55
28-44
20-34
15-27
10-20
5-13
2-8
5
9
12
15
10
10
11
9
10
5
4
5
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a Study on Fractional Replacement of Bitumen with Crumb Rubber
A
B
Figure 1. Materials used in the study (A) aggregates of specified quantity, (B) Crumb-Rubber
(300µm-150µm)
Table 2. Physical properties of aggregates
Property
Moisture content (%)
Aggregate Impact value
(%)
Flakiness Index (%)
Elongation Index (%)
Combined Elongation
and Flakiness Test (%)
Test result
0.20
MORTH specifications
Max 2%
Test method
IS:2386 Part-III
19.22
Max 24%
IS:2386 Part-IV
12.64
15.81
Max 30%
Max 30%
IS:2386 Part-I
IS:2386 Part-I
28.45
Max 35%
IS:2386 Part-I
2.2. Bitumen and Crumb Rubber
The samples were made using VG-30 grade bitumen and the physical properties of asphalt such
as penetration grade, softening point and ductility is shown in Table 3. The powdered form of
crumb rubber was used and in the size of 300µ-150µm. The specific gravity of crumb rubber
and bitumen was found out to be 1.1 and 1.052 respectively.
Table 3. Physical properties of bitumen (VG-30)
Property
Requirement as per IR IS 73 :
2013
Test result
Penetration at 25°C
0.1mm,100gm, 5sec
50-70
60 cm
40
38 cm
47
45°C
0.97-1.02
1.052
Ductility at 25°C, (cm)
Softening Point (R&B) (°C)
Specific gravity
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2.3. Methodology
Mix design is used to calculate that content of bitumen or any other material that will provide
maximum strength and durability as economical as possible. Marshal Mix design was used to
determine the optimum percentage of bitumen and crumb rubber. 1200 g of aggregate along
with 5% filler (stone dust) by weight of aggregate and various percentages of bitumen were
taken to determine the optimum value of bitumen.
2.4. Preparation of Blend Specimens
The preparation of bituminous mixes was done by mixing required quantities of coarse
aggregate, fine aggregate and stone dust as filler. The mix is heated at a temperature of 180°C
by keeping it in oven for 2 hour (IRC-MORTH). And bitumen is heated at temperature of
150°C. The required amount of crumb rubber is added and mixed in the bitumen while mixing
thoroughly to obtain a homogenies mix. Then the modified bitumen is added to the aggregates
and mixed properly at a temperature of 160°C (IRC-MORTH). Final mixture is poured into the
pre heated mold (100°C) and compacted by Marshall Hammer, 75 no. of blows were given on
each side of the specimen.
Figure 2. Mixing of crumb rubber in bitumen.
In this lab study the preparation of samples takes place in following steps:
I.
According to the objective of the study the first step was to determine the optimum
bitumen content (OBC) of the mix with the help of Marshal Test, this was achieved
by preparing the marshal sample at different bitumen percentages (4% to 6%
increment 0.5%).
II.
With the help of Marshal Stability parameters and volumetric parameters it was
observed that 5% bitumen content was fond out to be optimum.
III.
At this stage keeping the bitumen content constant (5%), crumb rubber (2% to 10%
increment 2%) was added by replacing the quantity of bitumen by weight (60g).
IV.
At the last stage Marshal Mix was prepared by adding modified bitumen into the
mix.
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a Study on Fractional Replacement of Bitumen with Crumb Rubber
3. TESTS AND RESULTS
3.1. Marshall Stability Test
Marshall Stability test is of vast importance and significant in the field of highway engineering.
This test is used to calculate stability value and flow value for various bitumen content. In this
study ASTM-D, 1559 has been used for testing of bituminous mixes.
In this study the criterion followed to calculate optimum content is to have maximum
corrected stability value, flow value under accepted range, percentage of air voids in accepted
range and values of VFB, VMA in accepted range and Marshall Quotient set according to ISMORTH. The Marshall properties for modified sample are present in table 4.
Table 4. Stability, flow value, %Air voids, %volume of bitumen, %VMA, %VFB, Volume of
specimen, Correction factor.
Percentage of
%Air
Crumb Rubber
voids(VA)
at 5% B.C
%VMA
%VFB
Volume of
Specimen
(cm3)
Correction
Factor
Corrected
Stability(KN)
Flow
Value(mm)
0%
3.75
14.24
73.66
550
0.89
16
3.54
2%
6.13
16.82
63.55
550
0.89
11.6
2.5
4%
5.29
16.08
67.10
552
0.89
12.6
2.33
6%
5.71
16.45
65.28
550
0.89
21.04
2.86
8%
6.17
16.82
63.31
554
0.89
16.7
2.27
10%
5.75
16.45
65.04
550
0.89
14.2
2.02
All the values stated above are mean of three samples.
In this laboratory study various percentages of crumb rubber was added to the optimum
bitumen content that was found out to be 5% to calculate the optimum rubber content on
bituminous mixes. All the graphs obtained from Marshall Tests are plotted on 2%, 4%, 6%,
8% and 10% of crumb rubber by replacing 5% Bitumen Content by weight respectively. As
shown in figure 3(A) stability decreases with increase in quantity of crumb rubber up to 2%,
but then starts increasing gradually with increase of crumb rubber at 4%, then stability increases
drastically up to 6% crumb rubber and then starts decreasing gradually with further addition of
crumb rubber. Figure 3(B) shows that flow value decreases drastically from 0% crumb rubber
to 4% crumb rubber but then increases at 6% crumb rubber and then decreases gradually with
further increase of crumb rubber. As it is observed from figure C the volume of air voids first
increases from 0% crumb rubber to 2% and then decreases up to 4% and followed by a gradual
increase up to 8% and then decreases with further inclusion of crumb rubber. From figure D it
is related that VMA increases with inclusion of crumb rubber and then remains constant. As
observed from figure E the VFB value first decreases with addition up to 2% crumb rubber and
then increases till 4% followed by a gradual decrease further.
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Fig A
20
FLOW VALUE(MM)
STABILITY (KN)
25
15
10
5
0
0% 2% 4% 6% 8% 10%
4
3.5
3
2.5
2
1.5
1
0.5
0
Fi
g
B
0% 2% 4% 6% 8% 10%
CRUMB RUBBER %
7
6
5
4
3
2
1
0
Fig D
18
Fig
17
C
VMA%
VA%
CRUMB RUBBER %
16
15
14
13
12
0%
2%
4%
6%
8% 10%
0% 2% 4% 6% 8% 10%
CRUMB RUBBER %
CRUMB RUBBER %
75
Fig E
VFB%
70
65
60
55
0%
2%
4%
6%
8%
10%
CRUMB RUBBER %
Figure 3. Variations of various Marshall Properties with varying percentages of Crumb rubber. (A)
Stability (B) flow value. (C) Air voids. (D) Variation in voids in mineral aggregate. (E) Variation in
VFB.
3.2. Penetration Test
The simplicity of this test makes it the most common and widely accepted test of asphalt to
obtain the grade of the material in terms of its hardness. In this experimental study penetration
value at different crumb rubber percentages is determined and it was observed that with
increase in the percentages of crumb rubber the penetration value is reduced. (Table 5). The
decrease in penetration value shows that consistency of bitumen changes and becomes harder
and hence making it better by addition of crumb rubber.
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a Study on Fractional Replacement of Bitumen with Crumb Rubber
Table 5. Penetration values
Penetration at 25°C 0.1mm,100gm, 5sec
Percentage of Crumb Rubber at 5% B.C
0%
2%
4%
6%
8%
10%
60
57
54
47
45
40
PENETRATION VALUE
70
Fig 4
60
50
40
30
20
10
0
0%
2%
4%
6%
8%
10%
CRUMB RUBBER %
Figure 4. Penetration value at different percentages of crumb rubber.
3.3. Ductility Test
During the construction of flexible pavement, it is desirable that bitumen is able form a thin
films around the aggregates. This test measures the tensile properties of bituminous materials.
In this lab study ductility value at different percentages of crumb rubber is determined and it
was found that with the increase in the quantity of crumb rubber in bitumen the ductility value
decreases. (Table 6). The reduction of ductility value shows the reduction of flexibility of
bitumen.
Table 6. Ductility values
Ductility at 25°C, (cm)
Percentage of Crumb Rubber at 5% B.C
0%
2%
4%
6%
8%
10%
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33.5
32.7
31
30
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40
Fig 5
DUCTILITY VALUE
35
30
25
20
15
10
5
0
0%
2%
4%
6%
8%
10%
CRUMB RUBBER %
Figure 5. Ductility values at various percentages.
4. CONCLUSION
In this laboratory study, the crumb rubber has been used as bitumen replacement by weight.
Marshall Tests are carried out on the bituminous samples to found out the optimum value of
crumb rubber. And tests such as Penetration test and Ductility tests were also accomplished to
evaluate the physical properties of modified bitumen.
 Through Marshall Properties it was observed that the use of crumb rubber in
bituminous mixes makes it more stable. According to the Marshall Properties the
use of 6% crumb rubber at 5% bitumen content was found out to be optimum
percentage. The use of crumb rubber also increases the percentage of air voids than
conventional mix.
 By the use of crumb rubber in road construction also solves the problem of waste
tire disposal and prevent environmental problems.
 The physical properties such as penetration and ductility of modified bitumen were
also improved, the modified bitumen was found out to be of harder consistency
making it more rutting resistant and less flexible.
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