Page 91 - Handbook of Thermal Analysis of Construction Materials

74 Chapter 3 - Formation and Hydration

The siliceous clay raw material is a source of both aluminum and
silica. It may contain one or more types of clay minerals. Other sources of
silica are quartz, chalcedony, opal, feldspar, etc. Table 1 shows the types of
clay minerals and their suitability as raw mixes for cement manufacture. [5]

Table 1. Clay Minerals, Mineralogy, and Their Suitability for Cement
Manufacture

Group Minerals Suitability

Kaolinite Allophane Suitable if they do not
Kaolinite contain alkalis and chloride.
Halloysite
Dickite

Montmorillonite Montmorillonite Usually not suitable because
Beidellite of swelling characteristics
Nontronite and presence of Na or Mg.
Glauconite Glauconite can be used if
it has a low K content.

Illite Illite Suitable if it does not contain
excessive amounts of alkalis.

Chlorites Ferrogenous Chlorite Suitable if free of alkalis.
Low Iron Chlorite

Mica Muscovite Both not used because they
Biotite have high alkali contents.

Amphiboles Sepiolite Both not advocated because
Attapulgite of higher Mg contents.

DTA can be applied to identify and estimate various types of clays
[6]
and calcareous minerals (Fig. 1). These minerals can be differentiated by
determining the temperature at which the endothermic and exothermic
peaks occur. For example, kaolinites exhibit an endothermic peak at