Use of Industrial Waste as Aggregate: Properties of Concrete - Recycled Aggregate in Concrete - page 132

significantly reduces slump (Etxeberria et al. 2010 ). Manso et al. ( 2004 ) reported
that concrete mixes with EAF-slag as the only fine and coarse aggregates lacked
cohesion, and therefore collapsed during mixing. The complete substitution of
coarse aggregate EAF aggregates of similar size and the substitution of the
0-4 mm fraction of NA by a 1:1 mixture of EAF-slag and limestone filler with
particle size \1 lm in the concrete mix can eliminate this problem. Qasrawi et al.
( 2009 ) also observed marginal reduction in slump for concrete mixes with steel
slag replacing up to 50 % by weight of fine NA and concrete can be classified as
having moderate slump. However, concrete with 100 % slag was sticky with
slump almost nil. The increase in the fine content and angular particle content of
the concrete mix due to the addition of slag as well as the slightly higher water
absorption capacity of slag by comparison with that of natural sand were the
causes of the observed slump loss. On the contrary, Al-Negheimish et al. ( 1997 )
did not observe any significant difference between the slump of concrete with steel
slag as coarse aggregates and conventional concrete at equal w/c value.
The bulk density of the majority of steel slags is significantly higher than that of
NA, and therefore the dry density of concrete with steel slag is generally higher
than that of conventional concrete. According to Papayianni and Anastasiou
( 2010 ), heavyweight concrete with a density of 2750 kg/m 3 could be produced by
using EAF-slag. Masleduddin et al. ( 2003 ) reported that the density of a fresh
concrete mix with EAF-slag with a 3.51 specific gravity replacing 45-65 % by
weight of crushed limestone aggregates were in the range of 2436-2769 kg/m 3 ,
whereas the density of concrete with crushed limestone aggregates with a 2.54
specific gravity was 2330 kg/m 3 . Al-Negheimish et al. ( 1997 ) observed a similar
increase in density due to the replacement of natural coarse aggregate by steel slag.
However, Qasrawi et al. ( 2009 ) observed a very slight increase (\5 %) in the
density of concrete with steel slag, used to replace up to 50 % by weight of fine
NA, and the resulting concrete was reported to be normal weight according to
ASTM specifications.
4.3.2 Hardened Concrete Properties
4.3.2.1 Compressive Strength
In several references, it was reported that the compressive strength of concrete
with EAF-slag as coarse and fine aggregates replacement was similar to or even
higher than that of conventional aggregate. However, contrasting results are also
available on compressive strength behaviour due to use of EAF-slag as aggregates
in concrete.
Al-Negheimish et al. ( 1997 ) observed similar compressive strength behaviours
in concrete with coarse conventional and with coarse EAF-slag aggregates as
curing time increased and for three different curing conditions, namely moist
curing at 21 C, curing at 28 C with 45 % humidity and curing at 55 C and 10 %