Civil Engineering Reference
In-Depth Information
60
12
Nanoill-15
Cloisite-15A
Nanoill-15
Cloisite-15A
9
40
6
20
3
0
0
0
2%
4%
7%
0
2%
4%
7%
Nanoclay content
Nanoclay content
6.5
Retained penetration (RP) and increase in softening point
(ISP) results.
6.5
Mechanical testing of asphalt mixtures
6.5.1 Specimen preparation
The specimens prepared for the different tests were Marshall tablets with
an average height of 60-65 mm and 100-102 mm diameter (ASTM D1559-
89, 1994). Dense mixture specimens were compacted by 75 blows applied
on both sides. As mentioned before, Cloisite-15A reduces the viscosity of
modifi ed binder so that it is not fl uid enough at the normal mixing tempera-
ture used for the standard binder (140°C). Hence, a high mixing tem-
perature was needed for the preparation of the modifi ed mixtures and so
the temperature was increased to 155°C. The Cloisite-15A content was
0.2%, 0.4% and 0.7% by weight of bitumen.
During the preparation of the specimen, the modifi ed binder had a dif-
ferent smell and became more viscous at 185°C. Modifi ed binder was rela-
tively less sticky to the mixing pan and to the moulds as compared to the
specimens of the standard mixes. All tests were performed in closed tem-
perature-controlled cabinets. In addition, all specimens selected for the
different tests were stored in a temperature-controlled cabinet to the target
temperature for a minimum of 3 h before commencing any test. The loading
control and input parameters used in testing are given in Table 6.4.
6.5.2 Marshal stability, fl ow and VTM
To compare the effects of different nanoclays in the mixes, Marshall stabil-
ity and VMA test results are shown in Figs 6.6 and 6.7. The results show
that, by adding nanoclay, Marshall stability and VMA increase.
Nanoclay is an active fi ller that improves strength properties of bitumen.
By adding 2% Cloisite-15A, stability increased by 15% but Nanofi ll-15
increased it by only 6%. Because of the large surface area, in the nanoclay
modifi ed mixture, the optimum binder increased. Even 1% nanoclay
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