Civil Engineering Reference
In-Depth Information
segregation index of sCC with a water-to-binder ratio of 0.45 decreases as
the FA replacement ratios increase. However, the segregation index increases
with an increase in the dosage of superplasticiser, accompanied by a decrease
in water-to-binder ratio for the sCC containing FA replacement around 40%
(Bouzoubaa and lachemi, 2001). Generally, the segregation resistance is
improved by the use of high-volume FA replacements (80-100%) in sCC
mixes (liu, 2010).
The setting times for sCC with high-volume FA are generally longer than
sCC containing only ordinary Portland cement (oPC), owing to the low
cement content. The maximum temperature rise in sCC with high-volume
FA replacement ratios is usually low due to its low cement content and the
slow FA reaction process. This behaviour could enable sCC with high-
volume FA to be used in large structural concrete members (Bouzoubaa
and lachemi, 2001). The binary use of FA or GGBFs significantly delays
the initial and final setting times, which can be prolonged even further by
increasing the FA or GGBFs replacement level. When ternary blends of
sF, FA or GGBFs are used, the inclusion of sF reduces the setting time
delay of sCC compared with the binary use of FA or GGBFs replacement
values. The combined use of FA and GGBFs in sCC slightly reduces both
the initial and final setting times compared to the binary blends of FA or
GGBFs (Gesoğlu and Özbay, 2007).
since some binary and ternary uses of blended sCMs (such as 40-60%
GGBFs and 45% FA-15% sF) do not comply with the l-box test requirements
of EFnARC (2005), ternary and quaternary blends of sCMs can be used (such
as 30%FA-30%GGBFs, 22.5%FA-22.5%GGBFs-15%sF, 45%GGBFs-
15%sF, etc.) to improve filling and passing. using GGBFs in the binary
blends causes high viscosity, whereas using FA around 40-60% replacement
levels, or using ternary or quaternary blended high volume sCMs, reduces
the viscosity and subsequently results in much lower V-funnel flow times
(Gesoğlu et al., 2009). The increase in GGBFs content from 15 to 45%
results in higher slump flow and passing ability, and lowers T
50
slump flow
and V-funnel flow time results (Güneyisi and Gesoğlu, 2011).
sCC containing 40% MK exhibits smaller slump flow diameter and
longer T
50
flow time values, as well as providing higher yield stress values
compared to sCC containing 56% GGBFs. The loss of flowability over time
is much faster for sCC containing MK than sCC with GGBFs. This could
be related to higher reactivity due to the higher specific surface value of MK.
The measured plastic viscosity of sCC with MK is around 100-136 Pa s.
This could imply that this mixture composition is thixotropic and has non-
newtonian fluid properties. A non-linear relationship exists between shear
stress and strain rate, and the apparent viscosity decreases with the duration
of stress. sCC with GGBFs mixture exhibits newtonian fluid properties with
zero yield stress and significant plastic viscosity around 175-233 Pa s. sCC
