Civil Engineering Reference
In-Depth Information
100
90
80
70
60
50
40
30
20
10
0
MK2
EM3
CP3
0
5
10
15
20
25
30
Time (days)
6.2
Calcium hydroxide reaction vs curing time for metakaolin (MK2),
earth of Milos (EM3) and ceramic powder (CP3) (Moropoulou et al.,
2004).
recommended by Brazilian, American and British standards to evaluate
three types of pozzolan: fly ash, silica fume and rice-husk ash. They
assert that different standards may sometimes generate conflicting results.
Pourkhorshidi et al. (2010a, b) mention that strength activity index in AsTM
C618 sometimes classifies as high reactive pozzolans, some supplementary
material that led to concrete with unsatisfactory performance, and that EN
196-5 had superior compatibility with real concrete performance. donatello
et al. (2010) stipulate that strength activity index of AsTM C618 and of
EN 196-5 are not suitable for evaluating pozzolanic activity of incinerator
sewage sludge ash. Accordingly sludge ash is a low reactive pozzolan, hence
the 28-day curing period is not sufficient, thus suggesting the Frattini test to
evaluate its pozzolanic activity. donatello et al. (2010) compared pozzolanic
activity of metakaolin, silica fume, coal fly ash, incinerated sewage sludge ash
using the Frattini test, the saturated lime test and the strength activity index
test. it was observed that saturated lime test is not a reliable test because it
does not correlate with other tests that could be explained by the different
activator to pozzolan ratio. They recommend application of the Frattini and
sAi methods in combination with an independent determination of Ca(oh)
2
content (thermal or diffraction methods) for the assessment of the pozzolanic
activity.
Although the electrical conductivity test correlates with other standard
methods it is not valid for high calcium fly ashes. Villar-Cocina et al. (2003),
Frías et al. (2005), Rosell-Lam et al. (2011) and dalinaidu et al. (2007)
have suggested a mathematical model predicated on electrical conductivity
measurements to describe the process in a kinetic-diffusive or kinetic regimes.
