Use of Industrial Waste as Aggregate: Properties of Concrete - Recycled Aggregate in Concrete - page 152

Fig. 4.30 Surface water
absorption of HSC due to
addition of copper slag as
sand replacement (Al-Jabri
et al. 2011 )
aggregates were replaced, which indicates that the densest microstructure was
observed at this replacement level. The drying shrinkage of concrete with copper
slag as fine aggregates is similar or even less than that of specimens without
copper slag (Ayano and Sakata 2000 ). Al-Jabri et al. ( 2011 ) observed a decreasing
trend of water permeable voids in HSC with increasing replacement of sand by
copper slag fine aggregates up to a 50 % replacement level; the voids increased
again as the content of copper slag continued to rise. The same authors observed a
decreasing trend of surface water absorption by HSC with increasing replacement
of sand by copper slag aggregates up to a 40 % replacement level; however, after
this substitution level, the surface absorption increased abruptly due to the pres-
ence of pores created by excessive free water (Fig. 4.30 ).
The freeze-thaw resistance of concrete with copper slag aggregates is lower
than that of conventional concrete due to the internal defects originated by the
upflow of bleeding water. However, the addition of an admixture and limestone
powder improves this property (Shoya et al. 1997 ). Birindha et al. ( 2010 ) observed
higher chloride corrosion rate of uncoated rebar in concrete with copper slag as
partial replacement of fine aggregates than in control concrete. The corrosion rate
increased with the slag content. But when the rebar was coated with zinc phos-
phate paint, no corrosion was observed in the corrosion period. The authors also
observed higher penetration rate of chloride ions at 40 and 60 % replacement rates
of fine aggregates by copper slag aggregates even though the amounts for all types
of concrete were very low according to the ASTM C1202 specification. The
sulphuric acid resistance capacity of concrete with copper slag aggregates was also
observed to be low in comparison to control concrete and decreased as the content
of copper slag in concrete increased (Fig. 4.31 ) (Birindha et al. 2010 ). The
resistance to sulphate attack and the rate of carbonation of concrete with copper
slag aggregates are similar to (or even better than) the ones of concrete with
conventional aggregates (Ayano and Sakata 2000 , Hwang and Laiw 1989 ).