Civil Engineering Reference
In-Depth Information
Fig. 5.55 Relationship
between the UPV (V) and CS
(S) of concrete (Khatib
2005
)
RCA and CBA (Fig.
5.55
). However, Kwan et al. (
2012
) commented that the
polynomial or exponential relationships were not appropriate to relate UPV with
CS of concrete containing RCA as there was a certain UPV value after which an
increase in UPV would not necessarily mean an increase in CS. Tu et al. (
2006
)
observed a lower UPV for high-performance (high-strength concrete (hpc/hs) with
RCA as replacement of both fine and coarse NA than that observed for hpc/hs with
RCA as the only coarse aggregate. The UPV increased with the w/c ratio.
Regardless of the type of mineral addition used as binder, Kou et al. (
2011b
)
observed a decrease in the UPV of 28-day concrete as the replacement of coarse
NA by RCA increased. However, the UPV of RCAC at all replacement levels of
coarse NA by RCA and with SF and MK as mineral additions was significantly
higher than that of conventional concrete with OPC as single binder or RCAC with
or without FA and ggbfs. The UPV of RCAC with FA and ggbfs was slightly
lower than that of conventional concrete. The gain in UPV between 28 and
90 days of curing for RCAC with mineral additions was higher than that for
concrete with OPC as single binder owing to the formation of more hydration
products and consequent improvement of the microstructure of RCAC due to a
pozzolanic reaction. However, contrary to these results, Topçu (
1997
) observed a
gradual increase of UPV in concrete due to the replacement of all NA by RCA,
linked to wider air-voids because of RCA incorporation. The UPV in conventional
concrete and concrete with 100 % RCA was around 70 and 93 ls, respectively.
5.4 Durability Performance
The durability of concrete is defined as the ability of concrete to withstand
chemical attack and external environmental and physical actions. A concrete with
a long service life must have a good durability performance. The durability of
concrete depends on various factors such as the properties of concrete's constit-
uents and their proportioning, the curing conditions and external environmental
conditions. Several tests are performed to evaluate the durability of concrete. A
