Environmental Engineering Reference
In-Depth Information
rocks showing ligth gray colour; they show por-
phyritic texture and numerous pores; within the
phenocrysts, k-feldspar, na-ca feldspar and
pyroxene have been identified; both rocks could
be classified as trachytes.
iii. The so-called Basalto do Bacharel (R4), in the
island of são Miguel, is an extrusive volcanic
rock of dark gray colour and pores of medium
size; it shows porphyritic texture, and within
their phenocrysts na-ca feldspar, pyroxene and
olivine have been identified; this rock could be
classified as basalt.
iv. Pedra da Vila do Porto (6) and Pedra do anal
(R7), both from the island of santa Maria, are
pyroclastic rocks of reddish brown and greenish
gray colour, respectively; they show porous and
vesicular texture, and the clasts have dimensions
within the range 2-64 mm; na-ca feldspar,
ca-Mg pyroxene, olivine and analcite were the
main minerals which have been identified; they
were classified as picrite basalts.
i. Pedra do Porto Formoso (R1) and Pedra da
Povoação (R2) from the island of são Miguel
could be classified as trachytes.
ii. Basalto do chão das Gatas (R3) and Pedra do
Dâmaso (R5) from the island of são Miguel
could be classified as trachybasalts.
iii. Basalto do Bacharel (R4) from the island of são
Miguel could be classified as hawaiite.
iv. Pedra do anal (R7) from the island of santa
Maria and Pedra da Vila do Porto (R6) from
the island of são Miguel could be classified as
picrite basalt.
also, taking into account the data contained
in Table 3 and the chemical classification of le
Bas
et al
., (1986), the studied ornamental natural
stones from the azores archipelago, in terms of
sio
2
content, range from basic (45% > sio
2
<52%)
to intermediate (52% > sio
2
< 63%).
5
PhYsical anD Mechanical TesTs
The properties that were determined on studied
volcanic stone samples are listed bellow, as well as
the european standards (en) used to perform the
tests. Properties were grouped according to their
purpose and a short procedure description was
also included.
4.3
Chemical analysis
Table 2 shows the results of the chemical analyses
carried out on the studied natural stones.
The most comprehensive classification of vol-
canic materials being used as ornamental natural
stone in the archipelago of the azores had been
established using the Francis´classification (1993)
that is based on the relationship (na
2
o + k
2
o)
content
versus
(sio
2
) content, expressed weight %.
The representation of the data shown in Table 2
allowed the classification into seven typologies of
the studied natural stones:
5.1
Identification properties
5.1.1
Uniaxial compressive strength (EN 1926)
six cubic specimens were laid and centred on the
plate of an ele international aDR 200 com-
pressive testing machine. it was applied a uni-
formly distributed and continuously increased
load until specimen failure occurred. compres-
sive strength was calculated as the ratio between
the failure load and the surface area submitted to
compression.
Table 2. Results obtained FRX the studied volcanic
stone samples.
References of the natural stones
5.1.2
Flexural strength under concentrated load
(EN 12372)
Ten parallelepiped specimens were placed on two
supporting rollers of an ele international Tritest
50 Digital flexural testing machine. The distance
between these rollers (span) was calculated accord-
ing to the specimen thickness and previously
adjusted. a force was applied by a third roller
placed on the middle of the specimen. The load
was progressively increased until failure occurred.
Flexural strength was calculated by the following
equation 1 below:
% oxides
R1
R2
R3
R4
R5
R6
R7
sio
2
60.11 61.41
55.92
45.26
56.10
44.75
45.08
Tio
2
1.01 1.03
1.81
3.78
1.83
3.18
3.14
al
2
o
3
18.24 17.92
17.66
14.34
17.68
16.99
16.75
Fe
2
o
3
T
4.48 3.99
6.32
12,87
6.34
12.74
12.56
Mno
0.17 0.15
0.12
0.18
0.12
0.26
0.19
Mgo
0.96 0.84
2.35
7.61
2.34
3.62
3.99
cao
2.57 1.94
4.68
9.14
4.69
7.26
7.92
na
2
o
6.91 6.03
5.38
4.20
5.16
4.98
5.52
k
2
o
4.93 6.36
5.25
1.92
5.25
0.99
0.75
P
2
o
5
0.21 0.14
0.35
0.64
0.35
0.63
0.59
3
2
×
failure load span
width hickness
2
×
Flexuralstrength
=
(1)
P.R.
0.40 0.20
0.17
0.05
0.14
4.60
3.50
×
×
