Civil Engineering Reference
In-Depth Information
80
Unmodiied binder
Nanoill-15
Cloisite-15A
60
40
20
0
2%
4%
7%
Nanoclay content
65
150
Unmodiied binder
Nanoill-15
Cloisite-15A
Unmodiied binder
Nanoill-15
Cloisite-15A
120
60
90
60
55
50
30
0
45
2%
4%
7%
2%
4%
7%
Nanoclay content
Nanoclay content
6.4
Rheological results test and nanoclay content.
Cloisite-15A content caused a decrease in penetration. Nanofi ll-15 has little
effect on softening point; by adding 7% nanofi ll, softening point increased
by only 3%. In contrast, Cloisite-15A has a relatively higher impact on
penetration and softening point of bitumen. By increasing Cloisite-15A
content, penetration decreases from 63 to 45 and softening point increases
from 54 to 61. Also both nanoclays reduce ductility of binder but Cloisite-
15A has a more pronounced effect in reducing ductility. This behaviour may
be the result of chemical reaction and change in chemical structure, as
pointed out by Ghile (2005).
When bitumen gets aged it becomes harder. Retained penetration (RP)
and increase in softening point (ISP) values, as defi ned below, were used to
fi nd the ageing effect:
aged penetration
unaged penetration
()
=
RP
%
×
100
°
()
=
(
)
ISP
C
aged soft
ennig point
−
unaged softening point
[6.2]
A lower RP value and higher ISP refl ect more ageing of the binder. Long-
term ageing was performed for 20 hours at 90°C and atmospheric pressure.
The retained penetration and increase in softening point were computed
and are presented in Fig. 6.5. It can be observed that there are some
improvements in the resistance to ageing in the long term due to the
Nanofi ll-15 modifi cation and therefore it will probably suffer less when in
contact with hot air or hot oxygen.
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