Civil Engineering Reference
In-Depth Information
Fig. 5.81 Depth of carbonation versus square root of time of conventional concrete as well as
RCAC's during accelerated carbonation test (Sagoe-Crentsil et al.
2001
)
Fig. 5.82 a Depth of carbonation and b relationship between depth of carbonation and time
(Buyle-Bodin and Zaharieva
2002
)
conventional concrete, due to the difference in composition of cement of residual
and fresh mortars. On the other hand, the carbonation coefficient of RCAC pre-
pared by the conventional method was lower than that prepared by the EMV
method due to lower fresh cement content in the later mix. Abbas et al. (
2009
)
reported that the addition of FA and slag increases the carbonation depth due to the
consumption of calcium hydroxide because of the pozzolanic reaction. The depth
of carbonation of RCAC with or without FA and slag prepared by the conventional
method as well as the EMV method and with 140 days of exposure fell in the
range of structural grade concrete, i.e. about 0-7 for conventional concrete and 7-
15 mm for concrete containing FA and slag.
Limbachiya et al. (
2012
) did not observe significant differences in the car-
bonation of conventional concrete and RCAC with various RCA contents when the
design strength was 20 MPa. However, the depth of carbonation increased with the
replacement ratio of coarse NA by RCA for the 30 and 35 MPa concrete classes
and this was more prominent for concrete prepared with 80 % OPC and 20 % FA
due to the pozzolanic reaction of FA, which lowered the Portlandite content and
thus the pH of the pore solution. The increase in carbonation in RCAC was due to
