DIGEST 2006 - Sabita

Water absorption: Steel slag is
typically more absorbent than
dolerite and quartzite, a property
arising from the nature of the steel
slag aggregate and the manner in
which it is produced. This has the
effect of higher binder absorption
than would be expected of dolerite
or quartzite. This is an important
factor that needs to be considered
in the evaluation of the mix
design, especially when
determining volumetric properties.
Flakiness index:
The flakiness index
of the steel slag
aggregate is
markedly lower
than that of dolerite
and quartzite
aggregates. The
more cubical shape
of the slag enables
the formation of
strong interlocking
structures within
the asphalt mixture,
which exhibits high
stiffness and
excellent resistance
to permanent
deformation.
Aggregate strength: The high
Ten Percent Fines and the low
Aggregate Crushing Value
indicates the high density and
crushing strength of the steel slag
aggregate, properties which
ensure substantial resistance to
degradation under traffic loading.
pH value: Steel slag, with a pH of
between 8 and 11, has a strong
affinity for bitumen and, therefore,
displays a greater degree of binder
retention. This is a very important
The more
cubical shape
of the slag
enables the
formation
of strong
interlocking
structures
within the
asphalt
characteristic in relation to
resistance to stripping and,
consequently, long-term
durability, and it makes steel slag
an ideal aggregate for enhancing
the life of asphalt mixtures.
Polished stone value: A polished
stone value of 63 for steel slag
aggregate indicates a high
resistance to the polishing of the
aggregate surfaces under the
action of traffic, which augurs well
for providing a texture that
promotes skid
resistance. It is
usual for an
aggregate having a
PSV in this range to
have a poor
abrasion value, as
the resistance to
polishing can be
attributable to loss
of particles or
grains from the
surface of the
stone. Steel slag,
however, also has
excellent resistance
to abrasion. This is
an unusual
combination of properties, making
steel slag a safe and durable
alternative to natural aggregates.
Free Lime: The application of
steel slag aggregates in road
construction is only practical if
there is sufficient volumetric
stability – a property indicated by
the presence of free lime. As
indicated in Table 1, the free lime
content of the steel slag aggregate
tested is 2,36%. A maximum limit
of 5% free lime is used as a
criterion to evaluate whether an
aggregate is suitable for use in
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