Civil Engineering Reference
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Fig. 5.83 Relationship
between CS and carbonation
depth (Limbachiya et al.
2012
)
the higher water absorption capacity of RCA, which releases water throughout the
hydration period and increase the humidity level of concrete. They also observed a
linear inverse relationship between CS and carbonation depth of concrete
(Fig.
5.83
). Like Buyle-Bodin and Zaharieva (
2002
), they observed that the car-
bonation depth of RCAC can be predicted by a basic diffusion law.
5.4.4 Freeze-Thaw Durability
The freeze-thaw phenomenon is an important issue for cold region concrete. It
occurs due to development of stress in a closed space such as pores in cement paste
due to the expansion of water when it freezes. Some cracks may be formed if the
stress is higher than the cement paste's strength; the damage can further increase if
freezing and thaw cycles continue. The resistance of concrete containing CDW
aggregate against freeze-thaw cycle is reported in several references.
Nagataki and Iida (
2001
) observed decreasing freeze-thaw resistance of con-
crete due to the incorporation of coarse RCA as a replacement of NA. However,
the freeze-thaw resistance was satisfactory as the freezing-thawing factor for
RCAC after 300 cycles was [70. Gokce et al. (
2004
) observed poor freeze-thaw
durability of air-entrained concrete with coarse RCA produced from non-air-
entrained concrete as the relative modulus of elasticity RCAC was below 60 %
after 30 cycles of freeze-thaw. According to them, the presence of a small amount
of non-air-entrained RCA can drastically deteriorate the freeze-thaw resistance of
air-entrained concrete. The poor freeze-thaw resistance was due to the conversion
of overall pore system of concrete containing coarse RCA with adhered mortar and
air voids into a partial non-air-entrained void system. On the other hand, regardless
of the adhered mortar content in RCA, the freeze-thaw resistance of concrete with
coarse RCA originated from air-entrained concrete was even better than that of the
conventional concrete after 500 cycles of freeze-thaw cycles even though the RCA
has higher permeable voids and water absorption capacity.
