Civil Engineering Reference
In-Depth Information
RCAC after exposure for 1-year to artificial sea water due to the replacement of 50
and 70 % OPC by ggbfs. The chloride diffusion coefficient of NAC and RCAC
containing OPC and OPC-slag as binder was in the range of 2 9 10
-12
and
8 9 10
-13
m
2
/s, respectively. Ann et al. (
2008
) observed a significant increase in
chloride ion permeability of concrete due to the incorporation of RCA as complete
replacement of coarse NA when both types of concrete (conventional and RCAC)
were subjected to rapid chloride ion penetration test (Fig.
5.75
). However, at a
replacement of 30 or 60 % of OPC by pulverised fuel ash (PFA) and ggbfs,
respectively, the chloride ion permeability of RCAC decreased considerably and
was even lower than that of the conventional concrete. They also observed
improved resistance against chloride-induced corrosion of RCAC containing PFA
and ggbfs due to the refinement of the pore structure as well as the increased
chloride binding capacity of the cement paste.
Shayan and Xu (
2003
) reported that concrete with RCA had lesser chloride
resistivity and higher negative half-cell potential than conventional concrete
although both parameters for RCAC were within acceptable limits. The corrosion
current densities of conventional concrete and RCAC were also similar and very
low indicating that both types of concrete were resistant to chloride induced
corrosion. The chloride ion penetration depth of concrete containing RCA
aggregate was also higher than that of the conventional concrete. The depth of
penetration of RCAC containing coarse RCA as a full replacement of coarse NA
was slightly higher than that of RCAC containing fine RCA as a 50 % replacement
of fine NA. On the other hand, the depth of chloride penetration for RCAC con-
taining sodium silicate plus lime treated RCA was higher than that of the RCAC
containing untreated RCA. The RCAC had inferior performance than the con-
ventional concrete in the rapid chloride permeability test too; however, the cor-
rosion protection of all types of concrete can be categories as high. The authors did
not find any advantages of sodium chloride treatment of RCA on the corrosion
Fig. 5.75 Chloride ion
permeability of conventional
concrete containing OPC and
RCAC containing OPC and
PFA and ggbfs (Ann et al.
2008
)
