Civil Engineering Reference
In-Depth Information
Fig. 5.27 STS of control concrete and RCAC containing various types of mineral admixtures
(Kou et al. (
2011b
)
prepared with OPC at the curing ages of 7, 28 and 90 days (Kou et al. (
2011b
)
(Fig.
5.27
). On the other hand, the RCAC prepared by replacing 35 or 55 % of
OPC by FA or ground granulated blast furnace slag (ggbfs) respectively had lower
STS than the control concrete and the RCAC containing OPC at all the curing
periods. The formation of more hydration products due to the SF and MK
hydration and the consequent improvement of the microstructure of ITZ increased
the binding of RCA and cement paste and hence improved the STS. The increase
in STS between 7 and 90 days was higher for RCAC using blended cement than
for the control concrete and the RCAC using OPC. The increase in tensile strength
was higher for FA and ggbfs than for SF and MK too.
Ann et al. (
2008
) observed that the 28-day STS for RCAC was lower than for
conventional concrete. The strength for RCAC using OPC-30 % pulverized fuel
ash and OPC-65 % ground blast furnace slag as binder was similar but lower than
that of the RCAC concrete. However, the ratios of STS to CS were comparable for
all types of concrete (Fig.
5.28
). In the Berndt's (
2009
) study, though the 28-day
STS of RCAC using 50 and 70 % ggbfs as replacement of OPC and RCA as sole
coarse aggregate was lower than that of concrete using slag cements and natural
aggregate as sole coarse aggregate, the STS of mixes having former composition
was higher than that of concrete using 100 % OPC and natural coarse aggregate as
well as of concrete using 100 % OPC and 100 % coarse RCA.
The STS of concrete with coarse RCA obtained after treatment by polyvinyl
alcohol followed by air-drying (PI-R(A) in Fig.
5.29
) was higher than that of
concrete with untreated RCA at the curing ages of 7-90 days. However, oven
