Construction Materials 4th Edition

Construction Materials 4th Edition

The structure of materials can be described on
dimensional scales varying from the smallest, atomic
or molecular, through materials structural to the
largest, engineering. Figure 0.1 shows that there is
considerable overlap between these for the different
materials that we consider in this book.
The molecular level
This considers the material at the smallest scale, in
terms of atoms or molecules or aggregations of
molecules. It is very much the realm of materials
science, and a general introduction for all materials
is given in Part 1 of the book. The sizes of the
particles range from less than 10-10 to 10-2
m, clearly
an enormous range. Examples occurring in this book
include the crystal structure of metals, cellulose
molecules in timber, calcium silicate hydrates in hardened cement paste and the variety of polymers,
such as polyvinyl chloride, included in fibre

We conventionally think of a material as being either

a solid or a fluid. These states of matter are con-
veniently based on the response of the material to

an applied force. A solid will maintain its shape
under its own weight, and resist applied forces with
little deformation.1

An unconfined fluid will flow under
its own weight or applied force. Fluids can be divided

into liquids and gases; liquids are essentially incom-
pressible and maintain a fixed volume when placed

in a container, whereas gases are greatly compressible
and will also expand to fill the volume available.

Although these divisions of materials are often con-
venient, we must recognise that they are not distinct,

and some materials display mixed behaviour, such
as gels, which can vary from near solids to near


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