Civil Engineering Reference
In-Depth Information
Fired clay products are very durable. They are not susceptible to aggressive
gases and pollution in the same way as concrete and stone. Floor tiles, for
example, are more durable than the grout between the tiles, and this may cause
a problem. To take advantage of the material's durability it should be easy to
dismantle and re-use. Roof tiles are no problem to recycle, but it must be
remembered that stone from coastal climates has often been exposed to more
frequent changes of temperature between freezing and thawing, making it
more brittle.
A stone floor laid in sand is no problem to lift and re-use. The same can be said
for internal brick cladding that is laid in a lime mortar or clay. However, if tiles
or a brick veneer are laid on a cement-based mortar, it is almost impossible to
remove them for re-use.
Crushed fired clay and ceramic products can be recycled as aggregate for
smaller concrete structures, render and mortars.
Waste products from plastic-based mortars for jointing and colouring contain-
ing heavy metals are problematic. In cases where antimony, nickel, chrome and
cadmium compounds are included, disposal at special depots or tips is required.
No coding exists for coloured ceramic tiles, making it necessary to give all tiles
the same treatment as a dangerous waste product.
Roof tiling
Production of roof tiles requires clay that has a high clay content, no large parti-
cles and a low lime content. Fired lime particles can absorb moisture in damp
weather and destroy the tile.
Properties of different roof tiles
Type
Properties
Monk and nun
Moss grows on it in damp climate
Plain interlocking
Very good, fire resistant
Pantile, non-interlocking
Good, not so watertight at the joints
Pantile, interlocking
Very good, fire resistant
In addition some special tiles such as ridge tiles and hip-tiles. The weight of roof
tiles varies from 30-40 kg/m
2
. Tiles must be fired at a temperature approaching
sintering, about 1000°C, to reduce their porousness.
There is a widespread belief that glazing increases a tile's resistance to frost. This
is not necessarily true. A glazed tile can still absorb moisture. Apart from its visu-
al appearance, the main purpose of glazing is to prevent the growth of fungus.
