Page 549 - Handbook of Thermal Analysis of Construction Materials

Section 4.0 - Durability of Clay Bricks 519

4.0 DURABILITY OF CLAY BRICKS

4.1 Dimensional Changes

Chemical, mineralogical, and physical characteristics of raw mate-
rials used for brick manufacture are important indicators of potential frost
durability. The following discussion pertains to raw materials containing
illites mixed with chlorites.
Thermal dilatometric curves obtained for six bricks extruded from
different raw materials are shown in Fig. 22. [31] Curves for those manufac-
tured from similar raw materials, but made by different forming meth-
ods, i.e., soft mud, dry press, and stiff extrusion, are shown in Fig. 23. From
room temperature up to 500°C, the dimensional change is approximately
linear and is due to thermal expansion. The abrupt increase in expansion
(500–800°C) is due to phenomena such as quartz inversion, exfoliation of
the illitic, and chloritic minerals due to dehydroxylation, and, possibly, the
escape of CO under pressure.
2

Figure 22. Thermal dilatometric curves of bricks extruded from different raw materials. [31]