Civil Engineering Reference
In-Depth Information
10.4.5 Freeze-thaw durability
Lane and ozyildirim (1999) obtained perfect results in their study with the
samples of 60% GGBFS and opC. However, for all experiments, better
results are gained for the mixtures with GGBFS rather than for with opC.
The highest resistance factor was obtained in the sample with 50% GGBFS.
pigeon and Regourd (1983) compared the mixtures with opC and 66% slag.
For both groups of samples, the same values are obtained for length changes,
massive loss and changes in dynamic modulus of elasticity and compressive
strength, air-gap systems and air-gap conditions.
10.4.6 Acid resistance
In their study of the long- and short-term performance of concrete with
GGBS and FA, Li and Zhao (2003) prepared concretes with 40% FA
and opC. After 3 days of wet cure, among the samples left in 2% H
2
So
4
solution, under room temperature for times of 4, 8, 16 and 50 weeks, it was
observed that concretes with 15% GGBFS and 25% FA are have superior
protection against acid attack than concretes with opC and 40% FA. The
change in weight at the end of 50th week is approximately 8%. The weak
resistance of concrete with opC against H
2
So
4
attack is due to the presence
of large pores and free Ca(oH)
2
in the concrete. The concrete with 40%
FA is also poorly resistant to H
2
So
4
attack at an early age. The reason is
that there are numerous un-hydrated FA particles in the concrete, and the
matrix is significantly porous at an early age. Furthermore, the amount of
C-S-H gel in the concrete with 40% FA formed by cement hydration is
less than the amount of C-S-H in concretes with opC or with FA and slag
(Bilim, 2006).
10.4.7 Alkali-silica reaction
The replacement of GGBFS with some cement can reduce the amount of
alkali. There are several alternative solutions to reduce the destruction deriving
from the ASR risk such as constraining the alkali content of the concrete,
use of GGBFS or FA, use of low-alkali cement and use of non-reactive
aggregate. Kwon (2005), in his study with high-strength concrete (HSC) of
500 kg/m
3
cement, found that for ASR, the overdose alkali content in HSC
is a disadvantage and that harmful volume expansions are not observed
in concrete if aggregate is used which is non-reactive due to chemical
methods and mortars. on the other hand, it is reported that the use of low-
alkali cement or 30% GGBFS instead of opC will avoid the expansions
caused by ASR: an increase of approximately between 1.0 and 1.7 kg/m
3
is observed in the alkali content of the concrete with a replacement rate of
