DIGEST 2006 - Sabita

• International specifications/
trends etc. and their
appropriateness for South
Africa.
From this initial process it became
evident that the revision process
could not just be confined to a
limited updating exercise. Over
and above identifying some of the
existing criteria that required
amendment, major additions to
the document were required to
provide additional guidance to
practitioners, especially the newer
entrants into the industry.
Amendments
Some of the more significant
proposed changes to the existing
document are detailed below:
• Applicability of current
classes: Even with the benefit
of hindsight, the original
decision to limit the number
of modified binder classes
was a good one. With the
acceptance that the binder is
but one component of the
final product, the current
trend internationally is to
reduce the existing number
of classes to a more
manageable and pragmatic
one. Notwithstanding the
above however, it has to be
accepted that, while
elastomers (SBR, SBS & B-R)
are still the most commonly
used modifiers, other
products such as plastomers
(EVA), natural hydrocarbons
and Fischer-Tropsch (FT)
waxes are currently being
more widely utilised. As such,
the present binder
classification matrix will be
expanded where possible to
include these products;
• Specialised applications: With
the increased use of modified
binders in a variety of road
applications, the guidelines
will be expanded to
incorporate these specialised
binders, such as modified
emulsions used in
microsurfacing and bond
coats for UTFC’s, and high
modulus and fuel resistant
binders used in hot mix
asphalt;
• Appropriateness of current
test protocols: While the
existing test protocols and
associated property limits are
not fundamentally
performance based, they
have been derived from
practical experience gained
over some considerable time.
It is envisaged that, while
some of the current tests
classified as “Report Only”
will be removed, the test
regime for the different
classes will be consolidated.
This is to ensure that we use
the most appropriate
measures, in which the
binder is expected to perform
in-service and during
handling, to control the
binder’s performance;
• Appropriateness of current
product property limits: A
number of amendments to
the existing product property
requirements have been
identified, some of which are:
º “tightening up” the
allowable limits on some
properties;
144