along the straight line [16]. It is clear from the Fig 2 that
bitumen content is not a potential outlier; thus it can be
concluded that the effect of bitumen content studied in this
work is not significant compared to the test temperature
which is a potential outlier. This may be attributed to the fact
that the range of bitumen content (4 – 5%) evaluated in
this study was very small.
Fig 3 is the plot of main factors effects. It can be
easily seen from the figure that all the factors have negative
slope. The Temperature plot has a very steep negative slope
whereas; the bitumen content has mild negative slope. This
may be due to the fact that with increase in temperature,
softening of bitumen takes place. The softening of bitumen
in the mix results in the permanent strains with application
of loads and thus decrease in resilient modulus takes place.
Specimen diameter plot has also shown the negative slopes.
This may be due to the presence of more micro cracks in
large diameter specimen compared to small diameter
specimen. Similarly load duration plot has also shown the
negative slope which indicate that higher strain result for a
longer period of time and reduce the resilient modulus