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Aggregates
| The
common types of aggregate met in practice are :
- Natural sands and gravels
- Crushed rocks (igneous, sedimentary,
metamorphic)
- Manufactured aggregates (iron
blastfurnace slag, expanded clay and shales, sintered
pulverised fuel ash, polystyrene beads)
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The availability of aggregates for concrete in New Zealand
is summarised in the table below:
| Area |
Igneous |
Sedimentary |
Metamorphic |
| Northland |
Basalt
throughout but poorest in the west |
Greywacke-argillite
in the east |
|
| Auckland,
Waikato, King Country |
Basalt
in Auckland, andesite |
Widespread
greywacke-argillite quarries. Chert used for decorative
purposes |
|
| Taranaki |
Andesites
predominent |
|
|
| Coromandel,
Bay of Plenty, Central Volcanic Region |
Predominatly volcanic
with andesites common Greywacke-argillite in east
but often of poor quality
| |
|
| East
Coast |
|
Greywacke-argillite
both quarried and as gravel. Limestone used in Gisbourne
area |
|
| Wellington |
|
Greywacke-argillite
both quarried and as river gravel |
|
| Marlborough,
Canterbury |
|
Principally
greywacke-argillite gravels |
|
| Nelson,
Westland |
Granite |
Greywacke
and limestone |
Quartzite |
| Otago,
Southland |
Basalt
and phonolite |
Greywacke
and schist gravels |
Schist |
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Table 1: Availability of aggregates for
concrete in New Zealand
Download
TR
11 - Properties of New Zealand Concrete Aggregates.
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