Civil Engineering Reference
In-Depth Information
Fig. 5.56
Drying shrinkage of conventional and RCA concrete (CC) versus time (Khatib
2005
)
at constant w/c ratio and near constant slump due to the replacement of fine NA by
fine RCA. Ajdukiewicz and Kliszczzewicz (
2002
) observed a significant influence
of RCA on the shrinkage performance of the resulting high-performance/high-
strength concrete. The shrinkage of concrete with RCA generated from two types
of concrete with granite and basalt as the coarse aggregates as complete
replacement of NA (fine and coarse) was 35-45 % higher than that of conventional
concrete. Kou et al. (
2011b
) reported that the incorporation of RCA as partial or
full replacement of coarse natural aggregate in concrete increased the 112-day
drying shrinkage of the resulting concrete due to the presence of old cement paste
and the low stiffness of RCA.
Domingo-Cabo et al. (
2010
) measured the drying shrinkage strain of NAC and
RCAC with coarse RCA as 20, 50 and 100 % replacement of coarse NA. After
180 days they observed 20 and 70 % higher shrinkage strain of the concrete mixes
with 50 and 100 % incorporation of RCA, respectively. The increase in volume of
the cement paste and of the porosity of concrete due to the incorporation of RCA
was the reason for the higher drying shrinkage of the RCAC. These results are
presented in Fig.
5.57
.
Zega and Di Miao (
2011
) observed similar drying shrinkage strains in con-
ventional concrete and RCAC containing fine RCA as 20 % replacement of fine
NA when both types of concrete after 180 days of drying shrinkage testing. On the
other hand, the shrinkage strain of RCAC containing 30 % fine RCA was slightly
lower than that of the NAC due to a lower effective w/c ratio. Regardless of the
type of aggregate in concrete, Yang et al. (
2008
) observed a higher rate of
shrinkage strain within the first 10 days of testing and then it gradually slowed
down. The shrinkage strain of concrete containing coarse or fine RCA as a 100 %
replacement of coarse or fine NA respectively was also lower than that of con-
ventional concrete in the first 10 days due to higher water absorption capacity;
however, at a later stage, shrinkage was higher for RCAC due to lower stiffness of
