DIGEST 2006 - Sabita

compared to the pure bitumen for
the dolerite mix, falls below the
recommended range of 12 – 16°C.
This would imply that the mix is
tender, soft and relative easy to
place and compact, while
resistance to permanent
deformation during the service life
might be reduced. The fatigue
resistance, however, should be
good.
Quartzite aggregate evaluation
results
In general the estimated VIM and
VMA values, as predicted with
PRADO, are slightly higher than
the actual values obtained.
The increase in the ring and ball
soft point temp (T R&B ) of the
quartzite mix at the design binder
content of 4.7% is 16.8ºC, which
is above the upper recommended
limit. This indicates that difficulties
may arise with the compactability
and workability of the mix.
However, it may also have a
positive effect on the deformation
resistance of the mix provided
durability is adequate and fatigue
resistance within specifications.
(ii) Bailey Method
The Bailey Method of gradation
evaluation focuses on the
aggregate properties that affect
the way aggregates fit together
(or pack) in a confined space or
volume (See Figure 1). To analyse
the packing factors, the method
defines four key principles that
break down the overall combined
aggregate blend into four distinct
Figure 1: Bailey Method Mix Composition Principals
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