Civil Engineering Reference
In-Depth Information
Fig. 5.22 STS of
conventional and RCA
concrete due to the variation
of cement type and cement
content (Sagoe-Crentsil et al.
2001
)
RAC containing RA as 25 and 50 % replacement of coarse natural aggregate than
in conventional concrete but not for the 100 % replacement. In this study, the CS
of RAC with 100 % coarse RA was also comparable to that of conventional
concrete. The authors point out that the absorption capacity of the adhered mortar
present in the partly saturated (humid) recycled aggregate and the effectiveness of
the new interfacial transition zone of the recycled aggregate concrete increased the
STS.
Sagoe-Crentsil et al. (
2001
) observed slightly low and significantly high 28-day
and 1-year STS, respectively, for RCAC containing OPC and slag cement than for
conventional concrete containing OPC (Fig.
5.22
). On the other hand, increasing
the cement content led to higher STS than for conventional concrete at the early
ages, but after 1-year the values became similar.
However, in some studies, a substantial reduction in STS in comparison to that
of CS due to the addition of CDW aggregate was also reported. Some typical
examples are presented in Table
5.13
. Evangelista and de Brito (
2007
) reported
that the un-hydrated cement content in fine recycled aggregate can affect the CS
Table 5.13 Reduction in 28-day CS and STS of concrete containing CDW aggregate in com-
parison to conventional concrete
Reference
Type of
aggregate
Reduction (%)
Replacement ratio of similar
size aggregate (%)
Compressive
strength
Tensile
strength
Yang et al. (
2011
)
RCA/coarse
5.7
13.8
100
2.7
a
Evangelista and de
Brito (
2007
)
RCA/fine
30.5
100
Rao et al. (
2011
)
RAC/coarse
7.48
13.9
25
14.1
18.0
50
17.5
23.2
100
Gonzales-Fonteboa
et al. (
2011
)
RCA/coarse
10.7
17.2
20, 50 and 100 %; w/c = 0.65
9.38
14.8
10.6
9.96
a
Increasing with respect to conventional concrete strength
