Civil Engineering Reference
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were exposed to cycles of freeze-thaw (-20 C for 8 h and then 20 C for 16 h)
for 8 days. Ajdukiewicz and Kliszczzewicz (
2002
) observed similar or even better
freeze-thaw resistivity in high-performance concrete with RCA than in conven-
tional hpc.
Razaqpur et al. (
2010
) observed similar freeze-thaw resistance of conventional
concrete and concrete with RCA as full replacement of coarse NA and prepared by
the conventional and EMV methods. The RCAC prepared by the EMV method on
the other hand exhibited better freeze-thaw resistance than the RCAC prepared by
the conventional method due to the lower mortar content in the former RCAC
(Abbas et al.
2009
).
5.4.5 Alkali-Aggregate Reactivity and Resistance to Harsh
Chemical Substances
A few references are available on the evaluation of the resistance of RCAC to
several harmful chemical reactions or chemical environment such as alkali-
aggregate reaction and sulphate resistance. Shayan and Xu (
2003
) observed
marginally higher expansion of concrete prisms with replacement of coarse or fine
NA by untreated or sodium silicate plus lime treated coarse or fine RCA than of
conventional concrete when the specimens of all the types of concrete were
subjected to the alkali-aggregate reactivity test for 1 year; however, the expansion
of all types of concrete was below 0.024 % and well within the limit, 0.04 %,
considered to be indicative of deleterious alkali-aggregate reaction.
Shayan and Xu (
2003
) observed satisfactory sulphate resistance of concrete
with untreated or sodium silicate plus lime treated coarse or fine RCA concrete
along with conventional concrete when concrete specimens were stored in a 5 %
sodium sulphate solution for 1 year. Limbachiya (
2010
) observed a comparable
expansion of two classes of conventional concrete and concrete with a 30 %
replacement of coarse NA by RCA and design strength of 10 and 20 MPa, when
both were immersed in a 3 % sodium sulphate solution for 6 months. However,
the sulphate-induced expansion of RCAC increased as the replacement level of
NA by RCA increased to 50 and 100 %. Limbachiya et al. (
2012
) observed lower
sulphate resistance potential of RCAC than of conventional concrete when both
were exposed to a 3 % sodium sulphate solution for 60 days. They observed
gradually higher expansion of concrete as the replacement ratio of coarse NA by
RCA increased (Fig.
5.85
a). However, the addition of FA as a 30 % replacement
of OPC slightly improved the sulphate resistance of RCAC due to the reduction in
mono-sulphoaluminate and Portlandite contents in the cement paste and the pre-
vention of reaction between free lime and sodium sulphate because of the poz-
zolanic property of FA (Fig.
5.85
b).
Berndt (
2009
) observed lower dynamic elastic modulus of concrete with RCA
as the only coarse aggregate after 12 months exposure into a 5 % sodium sulphate
