Civil Engineering Reference
In-Depth Information
Although these methods are not directly applied for recognition of amorphic
minerals, results have significant compatibility in case of amorphic minerals
in natural pozzolans. Therefore, measurement of insoluble residue according
to the EN196-2 procedure is recommended for evaluation of amorphic and
non-amorphic phases that are at play in pozzolanic activity (Pourkhorshidi
et al., 2010a, b).
6.3.3 Mineralogical analysis
Mineral components of pozzolans are identified semi-quantitatively by the
XRd method. The amount of non-crystalline (amorphous) silica having a
major role in pozzolanic activities is determined through identification of
the amount of crystalline minerals (Pourkhorshidi et al., 2010a, b). it should
be noted that there is a remarkable relation between iR and XRd; as the
insoluble residue content indicates the amount of soluble and insoluble
minerals detected in XRd.
Regarding the evaluation of major oxides, assessment of amorphic and
crystaline minerals for natural pozzolans is of prime importance. Results
of numerous antecedent studies have revealed that amorphic constituents
(such as cristopolite, zeolite and calcite) are the most significant active alkali
phases. There is no universal deterministic limit to the amount of amorphic
minerals in natural pozzolans considered for cement replacement. however,
investigations show that natural pozzolans, with less than 15% amorphic
minerals, would not have good performance as a cement replacement.
Another method being used for the identification of crystalline and non-
crystalline minerals in pozzolans is petrography which can be performed
using a petrography-microscope.
6.3.4 EN 196-5 and Frattini test
EN 196-5 (2005) evaluates pozzolanic activity of pozzolan cements designated
in EN 197-1 (2000). According to EN 197-1 (first published in 1995) pozzolanic
cements are classified in two groups, namely; CEM IV/A, and CEM IV/B.
The former type comprises 65-89% clinker plus a mixture of silica fume,
natural pozzolan and fly ash. The latter type has 45 to 64% clinker.
in EN 196-5, pozzolanicity is assessed based on the concentration of
calcium ion Ca
2+
(expressed as calcium oxide or Cao), present in the aqueous
solution in contact with hydrated blended cement after a fixed period. As
seen in Fig. 6.1, a unique predefined curve demarcates pozzolanic and non-
pozzolanic areas. The blended cement is satisfactory, if the concentration
of Cao in the solution falls below the curve.
in this method, test samples are prepared consisting of cement and natural
pozzolan and mixed with distilled water. After preparation, samples are
