61 Figure 4.35. Correlation VMA and AC with 10 CR toward asphalt content
Through the review of the VMA results in Table 4.8. and Figure 4.35. the following observations were obtained that VMA value of asphalt concrete with crumb rubber 10
is highest with the 7.0 by 25.34 and smallest with asphalt content 5.0 by 22.26. Thus it can be concluded that the 10 CR with bitumen increases void mine
aggregate.
4.15. Comparison of Marshall Test
Table.4.9. Comparison of Stability of AC modified with and without crumb rubber
Asphalt Content
Stability 0 CR
Stability 2.5 CR
Stability 5.0 CR
Stability 7.5 CR
Stability 10 CR
5.00
1035.33 896.78
784.31 747.51
731.87
5.50
1336.90 1056.50
883.42 884.20
769.38
6.00
1412.80 1181.26
962.00 901.33
774.43
6.50
1328.01 1172.59
921.08 900.28
718.15
7.00
1166.02 1029.50
846.48 809.21
649.58
y = 1,3761x + 15,043 R² = 0,7485
5,00 10,00
15,00 20,00
25,00 30,00
35,00
4,5 5,0
5,5 6,0
6,5 7,0
7,5 8,0
VM A
Asphalt Content
VMA Series4
Linear VMA
62 Figure 4.36. Comparison of Stability test for AC with and without CR
A. Stability Test
Through the comparison of the stability test results in Table 4.9 and Figure 4.36 it was obtained that the asphalt concrete without crumb rubber with asphalt content 6 has
optimum stability value of 1412.80 kg. On the other hand, AC modified with 2.5 CR has optimum stability value of 1181.26 kg at 6.0 asphalt content; AC modified with 5
CR has optimum stability value of 962.0 kg at 6.5 asphalt content. AC modified with 7.5 CR has optimum stability value of 901.33 kg at 6.0 asphalt content. AC modified
with 10 CR has optimum stability value of 769.38 kg at 5.5 asphalt content. Thus it can be concluded that the higher crumb rubber percent decreases stability. Further
injection of crumb rubber into the mixture led to a decrease in the value of stability because application of excessive crumb rubber decreases the coarse aggregate contact
point within the mixture. The addition of crumb rubber will give higher penetration or softer asphalt. As a result, the mixture becomes more flaccid so as to contribute to the
decrease in the value of stability. Low stability suggests low quality of aggregates. The stability of aggregates decreases with an increase in crumb rubber content Mashaan et al.
2013. It was found that increasing the crumb rubber reduces the stability of AC, with higher percent of crumb rubber yielding in lowest stability value. However, Al-Qadi et al.
0,00 200,00
400,00 600,00
800,00 1000,00
1200,00 1400,00
1600,00
1 2
3 4
5
S tabi
li ty
K g
Asphalt Content
2.5 5
7.5 10
__ min 800
63 2009 reported that crumb rubber has more effect on performance of asphalt mixture by
increasing the Marshal Stability and Flow. Table.4.10. Comparison of Flow of AC modified with and without crumb rubber
Asphalt Content
Flow 0CR
Flow 2.5CR
Flow5.0 CR
Flow 7.5 CR
Flow 10 CR
5.00 2.80
3.00 4.00
4.37 5.03
5.50 3.22
3.53 4.13
4.80 5.03
6.00 3.40
3.80 3.97
5.17 5.35
6.50 3.17
3.47 3.60
4.61 5.13
7.00 2.67
2.80 2.80
3.73 6.13
Figure 4.37. Comparison of flow test for AC with 0, 2.5, 5.0, 7.5 and 10 CR
B. Flow
Through the comparison of the Flows test results in Table 4.10 Figure 4.37 it was found that flow test value of asphalt concrete increased as the crumb rubber content
increased from 0 to 7. Higher flow values may be related to the increase of air voids more compaction required by using more CRM in the mixture, which leads to a more
flexible mixture.
0,00 1,00
2,00 3,00
4,00 5,00
6,00 7,00
1 2
3 4
5
fl ow
Asphalt content
flow 0CR flow 2.5CR
flow5.0CR flow 7.5 CR
flow 10 CR
Mix 4 Min 2
64 Thus it can be concluded that the higher the crumb rubber content increased flow
but higher asphalt content decreases flow. With the addition of the asphalt content the mixes become more flexible and the resistance to deformation decreases resulting in a
high flow value. Mashaan et al. 2013 similarly reported that the addition of crumb rubber modifier to asphalt concrete increases the flow of the mixture until optimum
crumb rubber content is reached.
C. Void Filled With Asphalt VFWA
The analysis of the VFWA test results in Figure 4.38 showed that modified with 0, 2.5, 5.0, 7.5 and 10 CR have maximum VFWA values of 80.60, 82.82,
73.37, 93.10, and 56.94, respectively. Thus it can be concluded that increase in percent of crumb rubber content increases the VFWA. The reason is that voids provide spaces for
the movement of the asphalt cement or asphalt rubber binder within the compacted mix. Mix design of asphalt and rubberized AC asphalt paving mixes is a trade-off between
high binder content to enhance long term durability and performance, and sufficient in- place void space to avoid rutting, instability, flushing and bleeding, as it is clearly shown
in Table 4.11 the VFWA. Table 4.11. Comparison of VFWA of AC modified with and without crumb rubber
Asphalt Content
VFWA 0CR
VFWA 2.5CR
VFWA 5.0CR
VFWA 7.5 CR
VFWA 10 CR
5.00 61.44
59.96 54.60
58.44 46.82
5.50 66.89
67.97 59.63
64.05 49.94
6.00 70.31
71.41 65.84
70.79 56.41
6.50 75.92
74.99 70.68
79.92 57.26
7.00 80.60
82.82 73.37
93.10 56.94
65 Figure 4.38. Comparison of VFWE test for AC with and without CR
D.
Voids In Mix VIM Test
Through the comparison of the Voids In Mix test results in Table 4.12. Figure 4.39. it was found that the Voids in Mix value of asphalt concrete without crumb rubbers
is 6.91. at asphalt content of 5, while AC modified with 2.5, 5.0, 7.5, and 10 CR have maximum Voids In Mix value of 7.37, 8.96, 7.78 and 11.84, respectively
asphalt content 5. Thus it can be concluded that higher crumb rubber and asphalt content increase Voids in Mix. This is supported by Ibrahim et al. 2014 which found
that crumb rubber particle size can affect the optimum binder content for open graded friction course. The durability of HMA is a function of the VIM or porosity. In general,
the higher the porosity, the less permeable will be the mixture and vice versa. Too much voids in the mix high porosity will provide passageways through the mix for the
entrance of damaging air and water. Too low porosity could lead to flushing where the excess bitumen squeezes out of the mix to the surface. However, Al-Qadi et al., 2009
5,00 15,00
25,00 35,00
45,00 55,00
65,00 75,00
85,00 95,00
1 2
3 4
5
VF M
A VFWA 0CR
VFWA 2.5CR VFWA5.0CR
VFWA 7.5 CR VFWA 10 CR
66 Table.4.12. Comparison of VIM of AC modified with and without crumb rubber
Asphalt Content
VIM 0CR
VIM 2.5CR
VIM 5.0CR
VIM 7.5 CR
VIM 10 CR
5.00 6.91
7.37 8.96
7.78 11.84
5.50 6.14
5.77 8.04
6.79 11.46
6.00 5.59
5.32 6.82
5.46 9.77
6.50 4.65
4.79 5.98
3.64 10.10
7.00 3.73
3.23 5.53
1.18 11.02
This relationship between VIM of the asphalt concrete AC and asphalt concrete modified with crumb rubber is shown in figure 4.39.
Figure 4.39. Comparison of VIM test for AC with and without CR
4.16. Indirect Tensile Strength Test ITS
