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Petrographic description (UNI 9724)
Prof. ing. G. Perna, Trento
Porphyry (rhyolite) is a
volcanic rock, one of the last unity of the volcanic complex of Premian
Age (270 M.y.) (Adige Valley, North Italy). The structural fabric of the
rock is porphyritic with (35 - 40)% (in volume) well crystallized minerals
in a fine-grained or glassy groundmass. Minerals are, in volume and in
repetition rate, quartz, sandine, plogioclase, rare biotite. The rock is
not alterated and naturally divided in vertical slabs with a thickness by
3 cm up to a 20 cm.
Table
summariziong physical and mechanical characteristics of porphyry
Monte Gorsa; Veneri & Casagranda |
|
Chemical
composition
of the porphyry
(average of 17
determinations) |
| SiO2 |
|
|
|
74,14 |
| TiO2 |
|
|
|
0,16 |
| P2O2 |
|
|
|
0,08 |
| Al2O3 |
|
|
|
13,01 |
| Fe2O3 |
|
|
|
1,34 |
| FeO |
|
|
|
0,42 |
| MnO |
|
|
|
0,05 |
| MgO |
|
|
|
0,36 |
| CaO |
|
|
|
0,78 |
| Na2O |
|
|
|
2,70 |
| K2O |
|
|
|
4,69 |
| H2O |
|
|
|
0,62 |
| P.C. |
|
|
|
1.93 |
|
|
|
|
|
|
|
|
|
|
| Test
description |
|
Unit |
|
Value |
|
Notes |
|
|
|
|
|
|
|
|
|
| Specific
weight |
|
Kg/m³ |
|
2 584 |
|
|
|
|
|
|
|
|
|
|
|
| Compressive
strenght |
|
Mpa
kg/cm² |
|
175
1750 |
|
(2) |
|
|
|
|
|
|
|
|
|
Compressive
strenght after
freeze/thaw cycles |
|
Mpa
kg/cm² |
|
211
2110 |
|
(2) |
|
|
|
|
|
|
|
|
|
Water
absorbion coefficient
(by weight) |
|
°/00 |
|
4,0 |
|
|
|
|
|
|
|
|
|
|
|
| Flexural
strenght |
|
Mpa
kg/cm² |
|
28,2
282 |
|
|
|
|
|
|
|
|
|
|
|
| Impact
test |
|
kg cm |
|
57 |
|
|
|
|
|
|
|
|
|
|
|
Coefficient
of linear thermal
dilatation |
|
mm/(m
°C) x 10 |
|
6.9 |
|
|
|
|
|
|
|
|
|
|
|
| Grazing
wear rate |
|
mm |
|
0,84 |
|
|
|
|
|
|
|
|
|
|
|
Normal
modulus of elasticity:
average modulus Normal
modulus of elasticity:
secant modulus |
|
Gpa
Gpa
|
|
57,9
58,0
|
|
|
|
|
|
|
|
|
|
|
|
| Knoop
microhardness |
|
Mpa |
|
3240 |
|
|
|
|
|
|
|
|
|
|
|
Notes:
- All tests have been carried out in accordance to the following norms:
linear thermal dilatation: NORMAL; grazing wear rate: RD2234, 1939; all
other determinations: UNI 9724.
- Determinations have been performed perpendicular o the slab surface.
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