I. STAVRAKAS ET AL.
Copyright © 2012 SciRes. OJAppS
65
Figure 9. Representative plot of the behaviour of ac con-
Observing Figure 8 it can be stressed that for type-1
sp
ductivity of the specimens that were s
je
la
4. Conclusions
rimental results manifest that uniaxial
crack
ge
e marble specimens that were subjected to uni-
ax
ductivity for all type-2 specimens in both before (b) and
after (a) removing their natural moisture.
ecimens that was subjected to load up to approximately
3 kN, the ac conductivity decreases while the applied
load increases. This can be attributed to the pore-closing
process that takes place in this load range and the conse-
quent limitation of the conductive paths in the bulk of the
specimen.
The ac conub-
cted to load in the range between 3 kN and 7.5 kN,
increases significantly with increasing load. This increase
can be attributed to the crack propagation mechanisms
that create additional conductive paths at the crack edges.
The behaviour of the dehydrated specimens was simi-
r but exhibited lower conductivity magnitudes. The
lower magnitude of the changes of the ac conductivity
can be attributed to the absence of water in the bulk of
the specimen. It can be concluded that ac conductivity
measurements can provide information regarding the
mechanical status of marble specimens that have suffered
stress enough to create damages in their bulk. The same
behaviour holds for type 2 specimens and it is shown in
Figure 9 with slightly smaller variations.
The presented expe
compressional loading, causes significant variations to
the ac conductivity spectrum of marble specimens.
The applied uniaxial load when leading to micro
neration in the bulk of the specimens makes conduc-
tivity to increase due to hydration within the micro-
cracks.
For th
ial compressional load the ac conductivity was meas-
ured in the frequency range 1 kHz up to 1 MHz. The re-
sults presented here correspond to the frequency of 10
kHz since it is the most sensitive to show up ac conduc-
tivity variations for changes of load.
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