Civil Engineering Reference
In-Depth Information
replaced by concrete as the main structural material, and since then it has often
been used to clad concrete structures. In addition to being more durable than
concrete, brick is easier to repair by replacement with new bricks.
Brick has a low tensile strength, which means that it is best used struc-
turally in columns, walls and vaults of a smaller scale. Reinforcement and
working with steel, concrete or timber, can expand its areas of use. Spans and
the size of building units can increase and brick can be used in beams and
floor slabs.
In normal brickwork, brick represents approximately 70 per cent of the volume
- the rest is mortar. Brick is a heavy material completely manufactured at one fac-
tory, in contrast with concrete which has two components. Brick is normally used
in large quantities, meaning that transport over large distances can have an envi-
ronmental impact.
The production of brick seriously pollutes the environment and is very
energy consuming, but bricks have a low maintenance level and are very
durable, in the majority of cases outlasting all other materials in a building.
Dieter Hoffmann-Athelm expresses this fact in his paradoxical critique of civ-
ilization: 'Brick is almost too durable to have any chance nowadays'. Bricks
can withstand most chemical attacks except for the strongest acids. Drains
made of the same material as bricks - fired clay - withstand acidic ground
conditions; concrete pipes do not. It is therefore important that the design of
brick structures considers the thorough planning of recycling. This would
make brick a much more competitive and relevant ecological building mate-
rial.
The polluted effluent from the brick industry can be relatively simply separat-
ed out or reduced by adding lime to the clay. The total energy consumption can
be greatly reduced by differentiating the use of bricks in well-fired and low-fired
products. Today only well-fired bricks are produced while low-fired alternatives
could be used for most purposes in less weather-exposed parts of brick struc-
tures. This was common practice until around 1950.
Bricks fired at 200-400°C have kept for at least 4000 years without serious
damage, mainly in warmer climates. In northern Europe the absorption of water
would be so high that the bricks would run the risk of being split by frost during
the winter if placed in exposed positions. A well-rendered brick wall, however,
can cope with this problem, as demonstrated by northern Europe's rendered-
brick buildings, many of which are built of low-fired bricks.
In a completed building, brick is considered a healthy material. The potential
for problems can arise when radioactive by-products are used in the manufac-
ture of the bricks, e.g. slag from blast furnaces. Otherwise brick has a positive
effect on the indoor climate, especially bricks with many pores, which will regu-
late humidity. Conventional washing down brick walls with hydrochloric acid
can cause problems in indoor climates.
