Civil Engineering Reference
In-Depth Information
Fig. 5.73 Relationship
between replacement ratio of
fine NA by fine RCA and
chloride migration coefficient
(Evangelista and de Brito
2010
)
(Table
5.23
). The values for the concrete containing CBMRA were significantly
higher than those observed for the RCA concrete due to the higher porosity of
CBMRA than that of RCA. They also observed an increase in the chloride pen-
etration depth with the water absorption capacity of concrete. The chloride per-
meability coefficient of concrete mixes containing 50 % RCA and 25 % CBMRA
was respectively 5.6 and 18.8 % higher than that of the conventional concrete.
Limbachiya et al. (
2000
) did not observe any negative effect on the chloride
diffusion performance of concrete due to the incorporation of coarse RCA as
partial or full replacement of NA in three classes of high-strength concrete with
design strength of 50, 60 and 70 MPa; the difference in chloride diffusion coef-
ficients between the conventional and the RCA concrete mixes was below
1 9 10
-11
m
2
/s. Limbachiya et al. (
2000
) observed similar chloride-induced
corrosion of conventional concrete and RCAC with design strength of 50 MPa
except for RCAC containing RCA as the only coarse aggregate when the con-
ventional concrete and RCAC cubes were exposed to a 2.5 M NaCl solution at 20
8C. However, the corrosion current of steel in RCAC with RCA as the only coarse
aggregate and the corrosion initiation time were slightly higher and slightly shorter
than for the conventional concrete and the RCAC with 50 % RCA, respectively.
Tu et al. (
2006
) observed higher chloride penetration (CP) for high-perfor-
mance concrete (hpc) with RCA as replacement of both fine and coarse NA than
that observed for hpc with RCA as the only coarse aggregate and NA as the only
Table 5.23
Chloride ion penetration depth of conventional concrete and RCAC's (Gomes and de
Brito
2009
)
Concrete
mix
Permeability
coefficient (m
2
/s)
(910
-12
)
Conventional 2.29 *13.0 12.50 6.31
RCAC1 8.49 *17.0 13.21 6.66
RCAC2 16.34 *15.5 24.30 7.50
RCAC3 - *17.0 14.39 7.26
RCAC1, RCAC2, RCAC3: concrete prepared by replacing 50, 25 and 37.5 % by volume of
coarse NA by RCA, CBMRA and a 2:1 mixture of RCA and CBMRA, respectively
Porosity of
aggregate (%)
Water absorption
capacity of concrete
(%)
Chloride
penetration depth
(mm)
