Civil Engineering Reference
In-Depth Information
humidity. However, curing conditions had a significant effect on the compressive
strength of steel slag concrete. Standard moist curing of this type of concrete
exhibited the highest compressive strength, followed by moderate and high tem-
perature curing. Moreover, at the latter stages of curing, deterioration of com-
pressive
strength
was
observed in
moist-cured samples
possibly due
to
the
formation of expansive products.
Pellegrino and Gaddo (
2009
) observed higher compressive strength in concrete
with EAF-slag than in conventional concrete after 7, 28 and 74 days of curing.
However, in this study, significantly higher amounts of fluidifying agent and
slightly higher amounts of aerating agent were used during preparation of concrete
with EAF-slag aggregate than those used in conventional concrete preparation.
The compressive strength of conventional concrete stabilized after 28 days of
curing while the compressive strength of concrete with EAF-slag increased with
curing time up to 74 days.
The 28-day compressive strengths of conventional concrete and concrete with
unprocessed steel slag in the Maslehuddin et al. (
2003
) study were 39.7 and
41.6 MPa, respectively. These concrete mixes were prepared using a similar
composition with coarse aggregate to total aggregate ratio of 0.60. The 28-day
compressive strength of concrete with slag aggregates with coarse aggregate to
total aggregate ratios of 0.45, 0.50, 0.55 and 0.65 were, respectively, 31.4, 37.7,
37.6 and 42.7 MPa. The authors also concluded that a coarse aggregate to total
aggregate proportion of 50 % may be adopted to minimise the weight effect of
heavy steel slag aggregates.
Almusallam et al. (
2004
) and Beshr et al. (
2003
) compared the compressive
strength of concrete with steel slag coarse aggregates to that of concrete with three
types of limestone aggregates. Concrete was prepared with a w/c ratio of 0.35 and
slump of 50-75 mm using a superplasticizer so that the compressive strength
performance can be related with the mechanical properties of the aggregates. After
28 days of curing, the compressive strength of concrete specimens prepared with
calcareous, dolomitic, and quartzitic limestone and steel slag aggregates were 43,
45, 47 and 54 MPa, respectively. According to the authors, for HSC the bulk of the
compressive load is borne by the aggregate rather than the cement paste alone and
therefore failure occurs through the aggregate. Thus, the compressive strength of
HSC depends on the mechanical prosperities of the coarse aggregates. Since the
steel slag aggregate had better mechanical properties than the other aggregates, the
incorporation of steel slag in concrete improved its compressive strength.
Papayianni and Anastasiou (
2010
) determined a 28-day compressive strength of
64.2 and 70.3 MPa for HSC with crushed limestone aggregate (reference concrete)
and concrete with coarse EAF aggregates, respectively. The compressive strength
of concrete with EAF-slag as fine and coarse aggregates was 77.9 MPa and it was
about 21.3 % higher than that of the reference concrete. The authors also observed
a higher rate of strength gain for concrete with slag aggregates during the initial
periods (0-7 days) of curing (89.2-92.2 % of 28-day strength) than that observed
for the reference concrete (81.8 % of 28-day strength).
