Civil Engineering Reference
In-Depth Information
Fig. 4.27 Compressive
strength of concrete with
copper slag fine aggregates
(Al-Jabri et al.
2011
)
(Ayano and Sakata
2000
; Caliskan and Behnood
2004
; Hwang and Laiw
1989
;
Li
1999
; Shoya et al.
1997
; Zong
2003
). Wu et al. (
2010
) observed slightly higher
dynamic compressive strength of concrete with copper slag replacing 20 % of fine
aggregates, which at 40 % replacement level became similar to that of the control
concrete. The dynamic compressive strength continuously decreased when the
replacement amount exceeded 40 %. According to the authors, the observed
improvement at lower substitution level was due to the presence of angular sharp
edged particles in copper slag as well as the improvement of cohesion between the
cement paste and the aggregates. However, at higher copper slag contents the
amount of free water increased due to the low water absorption capacity of copper
slag, which increased bleeding, internal voids and capillary pores in concrete.
The 7- and 28-day compressive strength of HSC with copper slag up to 50 %
replacement ratio (of natural sand) as fine aggregates were similar (or slightly
better) than those of HSC with natural sand. The compressive strength was reduced
significantly beyond that level of substitution, due to the separation of particles of
the constituents and the formation of pores in concrete by excess free water present
in concrete with copper slag aggregates (Fig.
4.28
) (Al-Jabri et al.
2009a
,
b
).
The compressive and splitting tensile strengths of HSC with copper slag as
coarse aggregates prepared at constant w/c ratio are higher than those of HSC with
limestone aggregates, due to the higher strength of copper slag aggregates com-
pared to limestone aggregates and also the porous and rough surface texture of
copper slag. This surface texture may produce a superior bond and transition zone
in comparison with that of the limestone aggregates (Khanzadi and Behnood
2009
). The incorporation of silica fume with cement can produce a stronger
transition zone between the copper slag aggregates and the cement paste due to its
pozzolanic reaction, and therefore increase the compressive strength (Khanzadi
and Behnood
2009
).
The tensile splitting strength and flexural strengths of HSC with copper slag
behave similarly to compressive strength. However, by comparison with com-
pressive strength a higher rate of development of splitting tensile strength was
observed
for
HSC
with
copper
slag
coarse
aggregates
than
for
limestone
