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| Practical information of aggregate |
· Optimum
grain shape, crushed/round
Cubic/spherical
shapes have proved more suitable than linear forms, which can affect the
consistence. Crushed aggregate has a slightly higher water requirement for the
same consistence because of its larger specific surface area, but higher
concrete compressive and particularly tensile strengths can be obtained due to
better interlocking.
· Predominantly
crushed aggregates
The surface
of crushed materials from rock, large blocks etc. consists only of broken
surfaces, while the surface of crushed round material also includes natural
rounded areas.
Crushed rock material is now mainly used in
tunneling, the motto being:
“Extraction
point = installation point”.
Quarry sands
These are
angular and also longish or flattish depending on the rock. They are not
conducive to a good consistence and their water requirement is generally
higher.
Harmful
contaminants
Loam, humus,
marl, clay, gypsum and aggregates containing sulphates, chlorides and alkalis
are all potentially harmful and their presence and possible consequences must
be clarified.
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