Civil Engineering Reference
In-Depth Information
4
The chemical and physical
properties of building
materials
Materials are produced in different dimensions and forms. A block is usually
defined as a building stone that can be lifted with two hands, while a brick can
be lifted with one. Two people are needed to carry a sheet. During recent years a
new category has come into play: the building element, which can only be
moved and positioned by machines. Each group of materials creates its own par-
ticular form of working.
Properties of materials are divided into chemical and physical. Chemistry
gives a picture of a substance's elemental contents, while physics gives a picture
of its form and structure. As far as chemistry is concerned, it does not matter
whether limestone, for example, is powder or a whole stone - in both cases the
material's chemical composition is calcium carbonate. In the same way, physical
properties such as insulation value, strength etc. are regarded independently of
chemical composition.
In traditional building it is usually the physical properties that are considered,
and it is almost entirely these properties that decide what the material can and
should be used for - its potential. Exceptions where the chemical properties are
also an important factor happen in cases where the material will be exposed to
different chemicals. Determining the resistance of a material to exposure to mois-
ture, oxygen or gases will include chemical analysis. This is much more neces-
sary nowadays with increased air pollution, which contains various highly reac-
tive aggressive pollutants.
An ecological evaluation of the production of certain building materials
requires a knowledge of which substances have been part of the manufacturing
process, and how these react with each other. This gives a picture of the possible
pollutants within the material, and what the ecological risks are when the mate-
rial is dumped in the natural environment. Increased attention to the quality of
indoor climates creates a greater need for chemical analyses. In many cases prob-
lems are caused by emissions from materials in the building. How these react
