DIGEST 2006 - Sabita

operations, as well as to
advance an understanding of
the relationship between
monotonic versus dynamic
properties of cold mixtures;
• Develop more realistic and
reliable specimen preparation
and conditioning protocols,
especially with respect to
compaction and curing.
Cognisance needs to be taken
of, for example, binder type,
aggregate type and active
filler content;
• Identify a durability test for
incorporation into the mix
design procedure. In the
broad sense, durability covers
binder durability as well as
mix durability (especially
moisture damage). Current
Tensile Strength Retained
(TSR) tests in the ITS mode
do not provide sufficiently
reliable simulation of
moisture damage;
• Identify a reliable and robust
classification system for
emulsion and foamed
bitumen treated materials
that could be used for
pavement design purposes.
Although a unified system
that would be generic for all
cold mixes would be
preferred, key differentiators
may need to be incorporated
to distinguish between the
materials if this is not
possible.
Given the scope of these
objectives, data on a wide range
of mixes has already been
gathered and synthesised in a
database under several different
headings, including mechanical
testing (shear properties, resilient
properties and permanent
deformation), flexural testing
(strain-at-break, flexural stiffness
and fatigue), curing, durability
(moisture susceptibility and binder
ageing) and compaction.
Laboratory and field research
(using trial sections) will continue
in 2007 to develop and calibrate
revised and new procedures for
the mix design of emulsion and
foamed bitumen treated mixtures.
Although some of the monitoring
of field trials will continue through
2008, by early in that year it is
planned that sufficient findings will
be available to incorporate into the
new guideline.
Structural design
developments
The aim of the structural design
component of the project is to
provide a practical, reliable and
validated methodology for
determining the structural capacity
of pavements that incorporate
bituminous stabilised layers. At
the outset, it was recognised that
such a method would require a
significant knowledge base related
to the construction and
performance of pavements that
incorporate BSM. A comprehensive
search and analysis task is
therefore being conducted to
obtain and document data relating
to the performance of BSM
pavements under long term field
loading conditions, as well as
under Heavy Vehicle Simulator
(HVS) testing.
To date, the available construction
and long term field performance
information for 17 BSM pavement
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