Environmental Engineering Reference
In-Depth Information
after correction according to the value obtained
for cRM.
analyzing the results of the test
resistance to
impact
, only Pedra da Povoação presents a value of
2 Joules, which is considered very low, and Pedra
da Vila do Porto is the only one that presents a
value which is considered low (3 Joules).
in terms of
resistance to abrasion
, Pedra da
Povoação presents the highest value (42.5 mm),
and is the only stone that should not be used for
paving. The two volcanic natural stones from santa
Maria island should only be used for paving on low
traffic conditions (for private applications). The
remaining volcanic natural stones can be used for
collective applications. Pedra do Porto Formoso
and Basalto do chão das Gatas only could be
used for moderate traffic conditions. on the other
hand, Basalto do Bacharel and Pedra do Dâmaso
could be used for both moderate and strong traffic
conditions.
5.4
Physical and mechanical properties
The average results of
uniaxial compressive strength
(cs) and
flexural strength under concentrated load
(Fs) obtained for the studied volcanic natural
stones are listed in Table 3.
The average results obtained for
apparent density
(aD),
open porosity
(oP) and
water absorption at
atmospheric pressure
(Wa) are listed in Table 4.
Rupture energy
, also known as impact resistance
(iR) and abrasion resistance (aR) average results
obtained for the studied volcanic stone samples are
listed in Table 5.
6
DiscUssion oF The ResUlTs oF The
PhYsical-Mechanical TesTs
7
conclUsions
analyzing the results obtained for
compressive
strength
on the studied volcanic natural stones,
three of them from s. Miguel island (Pedra do
Porto Formoso, Basalto do Bacharel and Pedra do
Dâmaso) present values above 40 MPa. any values
below the referred to value usually are considered
low. stones
Flexural strength
commonly has identi-
cal behaviour to the
compressive strength
. stones
that present low values of compressive strength
also present low values of flexural strength and
vice-versa. on the studied volcanic natural stones,
the only exception to this statement is Pedra do
Dâmaso that presents the highest value of
com-
pressive strength
(86 MPa), but does not has the
highest value for
flexural strength
that belongs to
Pedra do Porto Formoso (13.6 MPa). all
flexural
strength
values under 4 MPa usually are considered
low; only two stones present values below this limit
(Pedra da Povoação and Pedra da Vila do Porto).
The results obtained for the physical proper-
types of natural stone being tested. Their open
porosity is high, and consequently their
apparent
density
is low. concerning
open porosity
, values
above 10% are considered very high and three of
the studied volcanic natural stones exceed this limit
(Pedra da Povoação and the two stones from sta.
Maria island). These three stones are also the only
ones which present
water absorption
values above
6%, value above which water absorption is consid-
ered high. as expected, physical properties have
great influence on the mechanical behavior. That
is why stones having higher apparent density and
both lower open porosity and water absorption
generally present higher values of compressive and
flexural strength.
The research being carried out on volcanic natu-
ral stones of different typology from the azores
archipelago clearly has shown how much the
physical-mechanical properties are dependent
upon rock lithology and texture. such has been also
found on similar studies carried out by Gomes &
silva (1997), silva
et al
., 2002, and silva & Gomes
(2004), on volcanic natural stones from the Madeira
archipelago.
compiling the information obtained for the
physical and mechanical properties of the studied
volcanic natural stones from the azores, it can be
concluded that all stones are more suited for inter-
nal applications, due to the fact that the required
water absorption value for external applications is
usually ≤0.5%.
Pedra da Povoação from s. Miguel island is
not suitable for paving, not only because of its
high abrasion resistance value (42.5 mm), but also
because of its low impact resistance (2 Joules). in
fact, for most of the applications, the selection of
this stone and also of the two stones from sta.
Maria island has to be deeply considered to avoid
unsuccessful results.
in Portugal and in many european countries
there are not national specifications which regulate
property values that stones should satisfy to be
used as construction materials. as a consequence,
the selection of an adequate stone for a specific
application depends mainly upon the prescriber
expertise.
This study, in addition to the characterization
of several volcanic natural stones exploited in
the azores archipelago, also put forward some
considerations about stone applications.
