Civil Engineering Reference
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Fig. 5.74 Chloride ion resistivity of RCAC (DR Concrete with RCA as fine and coarse
aggregate; DN Concrete with coarse RCA and fine NA) (Tu et al.
2006
)
fine aggregate due to the lowering of residual mortar content (Fig.
5.74
). At fixed
water content, the CP increased with the water to binder ratio. On the other hand,
at fixed water to binder ratio, the lower CP was observed for RCAC containing
lower water content. The CP of concrete with RCA as coarse NA replacement or
as a replacement of fine and coarse NA after 91-day of curing was below 2000
Coulombs, the specified amount according to ASTM C 1202.
Kou et al. (
2008
) observed a decrease in resistance to chloride ion penetration
with the coarse RCA content due to the porous nature of RCA. In the Kou and
Poon (
2010
) study, the chloride permeability of concrete containing RCA as
complete replacement of coarse NA was significantly higher than that of the
conventional concrete, especially after 28 days of curing. However, the resistance
to chloride permeability of concrete with oven dry and air-dried polyvinyl alcohol
treated RCA was respectively 32 and 35 % higher than that of concrete with
untreated RCA and comparable to that of conventional concrete. The chloride ion
permeability of 90-day cured of both types of concrete (conventional and RCAC)
was lower than that of 28-day cured concrete and was more significant for concrete
with untreated RCA. Kou et al. (
2007
,
2008
) also observed an increase in resis-
tance to chloride ion penetration of normal water cured or steam cured RCAC with
decreasing water to binder ratio and increasing curing time.
Like in conventional concrete, the resistance to chloride permeability of con-
crete with RCA can be improved by using mineral additions (Kou and Poon
2006
;
Kou et al.
2011b
; Poon et al.
2007
; Ann et al.
2008
; Berndt
2009
). This is due to
the improvement of the watertightness of concrete (due to a microstructure
improvement) and of the chloride binding capacity of cement paste because of the
formation of high amounts of calcium silicate hydrate and calcium alumina sili-
cates (Kou et al.
2011b
). Kou et al. (
2011b
) observed a significant improvement of
chloride permeability resistance in conventional concrete as well as in RCAC due
to the replacement of 10, 15, 35 or 55 % of OPC by SF, MK, FA or ground
granulated blast furnace slag (ggbfs), respectively and the ranking of improvement
was: ggbfs [ FA [ MK [ SF. The measurement was done for concrete speci-
mens obtained after 28 and 90 days of conventional curing. Berndt (
2009
) also
observed a significant decrease in the chloride diffusion coefficient of NAC and
