Page 532 - Handbook of Thermal Analysis of Construction Materials

Section 2.0 - Clays and Accessory Minerals 503

Figure 8. TMA of a clay containing 10% limestone. [18]

Dimensional changes occurring on firing kaolinite and illite are
illustrated in Fig. 9. Kaolinite and holloysite exhibit a slight expansion up
to about 500°C followed by a small amount of shrinkage accompanying the
loss of hydroxyl water, up to about 900°C. At higher temperatures, larger
shrinkage accompanies the formation of the high temperature crystalline
phases. Shrinkage at about 1000°C has been attributed to the formation of
mullite. Shrinkage at higher temperatures, to about 1200°C, is associated
with the formation of cristobalite.