Issue 4

In our experimental work the opportunities of improving of mechanical properties of rubbers and their
composites have been investigated. On the one hand the reuse of milling product of recycled
rubbers (recycled crumb rubbers) has been studied and the effects of the filler and compatibilizers
applicable in rubber composites on the mechanical properties either. The rubber composites were
exposed to different mechanical stresses (tensile, fatigue tensile) and Shore A hardness and density
of the specimens have also been determined. Morphology of the composites and the interaction
between the fillers and the rubber has been studied on SEM graphs. Recycled crumb rubber was
added in different concentrations to the basic mixture of rubber. Significant improvement of
mechanical properties could be achieved by mixing 22m/m% used crumb rubber to the basic
mixture. Tensile strength at break of composites containing recycled crumb rubber increased with
nearly 20% compared to the original basic mixture containing no crumb rubber. Density decreased
with 2-3% and Shore A hardness with 6% comparing the aforementioned composites. Different
types of compatibilizing additives have also been applied in the system containing crumb rubber
which showed different effectiveness in case of the properties, e.g. tensile strength at break. Adding
compatibilizing additives to the basic mixture of rubber did not make the density changed while
Shore A hardness changed similarly to the trend observed in case of tensile strength at break.

Electric Arc Furnace Dust (EAFD) generated through the production of carbon and alloy steel products
is classified as environmentally hazardous waste mainly because of its relatively high levels of Pb, Cd
and Cr. The aim of the present work was to investigate the effect of the EAFD addition on the properties
of concrete building products (e.g concrete bricks) and to stabilize the toxic elements contained in
EAFD in order to get environmentally accepted products. Concrete specimens were prepared by vibration
and press-forming of mixtures containing cement, sand, dolomite, calcium stearate with water and the
addition of different percentages of EAFD. For the immobilization of the toxic elements of EAFD within the
matrix of the specimens, different percentages of each one of NaH2PO4, H3PO4 and of a mixture of H3PO4
- FeSO4.7H2O were added successively to each one of the mixtures as stabilizing materials. Modulus of
rupture (MOR) and water absorption (WA) tests showed that the specimens produced had specifications
within accepted limits for relevant products. Leaching tests applied on the specimens proved the compliance
with imposed leachate Maximum Acceptable Limits (MAL), since the practiced stabilizing materials
effectively immobilize toxic elements within the prepared specimens.

An artificial neural network (ANN) model-based approach was developed and applied to estimate
values of air temperature and relative humidity in remote mountainous areas. The application site
was the mountainous area of the Samaria National Forest canyon (Greece). Seven meteorological
stations were established in the area and ANNs were developed to predict air temperature and
relative humidity for the five most remote stations of the area using data only from two stations
located in the two more easily accessed sites. Measured and model-estimated data were compared
in terms of the determination coefficient (R2), the mean absolute error (MAE) and residuals
normality. Results showed that R2 values range from 0.7 to 0.9 for air temperature and from 0.7 to
0.8 for relative humidity whereas MAE values range from 0.9 to 1.8 oC and 5 to 9%, for air
temperature and relative humidity, respectively. In conclusion, the study demonstrated that ANNs,
when adequately trained, could have a high applicability in estimating meteorological data values in
remote mountainous areas with sparse network of meteorological stations, based on a series of
relatively limited number of data values from nearby and easily accessed meteorological stations.

Human thermal comfort conditions were determined in two mountainous regions of Greece, Gerania
mountains (MG) in east continental Greece, and mountainous Nafpaktia (MN) in west continental
Greece. Both regions are unexploited with considerable tourist potential. Four sites in each study
region were selected on the basis of different altitude. Air temperature and humidity, 1.5 m above
ground surface, were recorded simultaneously every 15 minutes by sensors with dataloggers in
selected sites between 23 June and 28 August 2007. Data of the above parameters were used for
the calculation of the thermohygrometric index from which thermal comfort conditions were
evaluated. Also, an artificial neural network model, was applied for the THI values evaluation at the
highest examined altitudes based on the respective values of the lowest examined altitudes in both
MG and MN. Results showed that from 09:00 to 20:00 h, MN was found to be more suitable, in
relation to MG, for tourist and recreation activities at altitudes of 1338 m. At lower altitudes, both
study regions could be proposed in an equal basis for the above activities during summer. Also, for
the same period, thermal comfort conditions at the highest examined altitudes of MN and MG can
accurately be predicted using artificial neural network models on the basis of those at lowest
examined altitudes. From 21:00 to 08:00 h, MN can be considered clearly as a better tourist
destination than MG.