Civil Engineering Reference
In-Depth Information
Fig. 5.21 Reduction in CS
of concrete due to the
incorporation of fine recycled
aggregate (Yaprak et al.
2011
)
particles of FCRA. Yaprak et al. (
2011
) also observed a gradual drop in CS as the
replacement of FNA by FRCA increased (Fig.
5.21
).
Evangelista and de Brito (
2007
) conducted a comprehensive study on the use of
pre-saturated FRCA (\2.36 mm) as a partial or complete replacement of same size
FNA in the preparation of structural concrete. The concrete mixing time was
maintained as 10 and 20 min for series I and series II concrete, respectively. The
results are presented in Table
5.10
. The 28-day CS of series I FRCAC was mar-
ginally higher (2-5 %) than the conventional concrete, due to the pozzolanic
reaction of un-hydrated cement present in FRCA. On the other hand, the CS
decreased by about 0.6-7.6 % with respect to the conventional concrete in series II
FRCAC since the increased soaking time of FRCA weakened the cement paste-
aggregate bond by increasing the w/c in that particular region. The development of
CS of conventional concrete almost stabilised after 28 days; however, the CS
development of FRCAC continued after 28 days due to the hydration of cement
present in FRCA. Zega and Di Miao (
2011
) also observed a slight decrease in 28-
and 84-day CS of concrete due to a 20 and 30 % by volume replacement of fine
NA by fine RCA.
Table 5.10
CS of concrete containing fine recycled concrete aggregate (Evangelista and de Brito
2007
)
Concrete type
Amount of substitution
of FNA by FRCA (%, v/v)
Compressive strength (MPa)
Series I
Series II
FNAC
0
59.4
59.3
FRCAC10
10
62.2
59.0
FRCAC20
20
58.4
57.3
FRCAC30
30
61.3
57.1
FRCAC50
50
60.8
58.8
FRCAC100
100
61.0
54.8
