Fired Clay Materials

Basic info is found in Chapter 8.

Fired clay in the form of bricks is mainly a structural material and has high thermal conductivity. However, it is possible to add substances to the clay that burn out during the firing and leave air pockets in the structure. The lighter product that results can be found in slab or block form.

Clay can also be expanded to light expanded clay pellets for use as loose fill or cast with cement to form blocks or slabs. By exposing light expanded clay to even higher temperatures, the light, airy granules cohere into a solid mass that can be used to form blocks known as Zytan. This type of block is not in production due to high energy use in manufacture.

All fired clay products are chemically inactive. In the indoor climate there are no problems with these products.

Certain types of brick products are good moisture regulators, the more developed the microporous structure, the better. Low-fired

Table 14.6 Climatizing qualities of fired clay products

Material

Areas of use

Vitrified and well-fired bricks1

Thermal buffering, sound insulation

Low and medium fired bricks1

Thermal buffering, moisture buffering, sound insulation

Bricks with high lime content (15-20% lime)1

Thermal buffering, moisture buffering, sound insulation

Porous bricks

Thermal insulation, thermal buffering, moisture buffering, sound insulation

Expanded clay pellets, loose

Thermal insulation, capillary barrier

Zytan block

Thermal insulation, sound insulation

1 Discussed in Chapter 13, Structural materials.

1 Discussed in Chapter 13, Structural materials.

14.10

Porous brick with lime rendering balancing humidity in a bathroom. Hydraulic lime mortar is used to improve the potential for re-use of bricks. Gaia Lista, 1996.

14.10

Porous brick with lime rendering balancing humidity in a bathroom. Hydraulic lime mortar is used to improve the potential for re-use of bricks. Gaia Lista, 1996.

brick and brick with a high proportion of lime give the best results (Figures 14.10 and 14.11). Because of the large amount of energy needed in manufacture, all fired clay products should be recycled, preferably by re-use in their original undamaged form. Coloured and glazed clay products may contain heavy metal pigments, and as a result can cause problems when they are finally disposed of.

Lightweight bricks and blocks are fired at temperatures of 1000 °C or more. The organic ingredients (sawdust, pieces of cork, etc.) are burnt away to leave an internal structure with isolated air holes. In one particular product, granules of polystyrene are used. During the firing the polystyrene granules vaporize as water, carbon dioxide and

14.11

Exterior of bathroom shown in Figure 14.1C. Both walls and floor consist of mineral materials only, to prevent moisture damage. Perlite is used as thermal insulation. Gaia Lista, 1996.

14.11

Exterior of bathroom shown in Figure 14.1C. Both walls and floor consist of mineral materials only, to prevent moisture damage. Perlite is used as thermal insulation. Gaia Lista, 1996.

styrene, the latter being regarded as a serious toxin. The completed product is probably free of polystyrene.

Insulating aggregate such as fossil meal can be added and once fired the blocks have a relatively high thermal insulation value.

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