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This study presents the preliminary results of investigation of the lime mortars and plasters from archaeological excavations in Hippos (Israel), using Electron Paramagnetic Resonance (EPR) spectroscopy. The research was conducted in order to characterize the building material and its reaction to ionizing radiation. The ancient settlement Hippos, situated on the east shore of the Sea of Galilee, functioned from the 3 cent. BC until it was destroyed by the earthquake in 749 AD. Lime mortars and plasters show carbonate and locally gypsum character of binder and different kind of aggregate. Samples were γ-irradiated and measured using X-band EPR spectrometer. Computer Resolution Enhancement Method was applied to the complex spectra. Some of the γ-induced EPR signals were attributed to CO and CO paramagnetic centres. Exponential growth of the dose response curve above 1 kGy and saturation for doses above 20 kGy was observed. For doses lower than 1 kGy the dose response curve has a linear character. The presence of γ-sensitive carbonate paramagnetic centres could indicate that, after further studies, well-chosen samples of mortars and plasters might be suitable for EPR dating, assuming the centres have been sufficiently bleached during the manufacturing process. [ABSTRACT FROM AUTHOR]

The presented work shows the methodological problems of mortar radiocarbon dating. Dating of lime mortars is based on setting the present 14C concentration of atmospheric CO2 by mortar carbonates in the hardening process. The big difficulty is the presence of aggregate, especially carbonatious one. The application of limestone fragments as aggregate in mortar, is connected with the presence of carbon partially or completely devoid of the radioactive isotope 14C. To carry out radiocarbon dating of the mortars reliably, it was necessary to remove the limestone aggregates. In this context, the application of petrographic studies that enable determination of mineral composition and the percentage of aggregate turns out to be particularly important. Such an identification allows to reconstruct mortar technology and, in combination with geological studies on the investigated terrain, helps to identify the provenance of the applied raw material. To make possible the comparison of the analysed mortar results and the verification of the applied methods, in year 2001 control mortars (mortars with established age) were used. The analyses were performed on mortars from a Romanesque castle built in the years 1177-1230 AD (Wleń, SW part of Poland) and from roman buildings with an approximate age of 140BC-68 AD (west coast of the Dead Sea,). We present the complex study of the mortar including both petrographical analyses and radiocarbon dating. The gas proportional counting technique (GPC) was applied for radiocarbon dating. Thin sections of roman mortars showed the carbonatious character of the binder and a large part of the aggregate; this was the source of the apparent age in radiocarbon dating. In spite of efforts to eliminate the lime aggregate from the mortar (by freezing, warming up, and separating under the binocular), and taking into consideration the amount of old carbon admixture derived from the carbon stable isotopes composition, there is still a great disproportion between historical and radiocarbon dating of these mortars. The results of the 14C dating show, that improvement of the binderaggregate separation process is necessary. The mortar aggregate from the Polish castle samples does not contain limestone grits, only scarce quartz grains. These Romanesque mortars were tested successfully and the existing architectural and historical data confirm the results obtained by GPC. [ABSTRACT FROM AUTHOR]

The presented work discusses results of radiocarbon dating of lime mortars sampled from walls of a Romanesque chapel at the Wleń castle. Considering a homogeneous structure of the mortars, an attempt to determine the chronology was made. Radiocarbon dating was carried out both on carbonate binders and laboratory-selected charcoals from the mortars. According to obtained data, charcoal ages are older than the age of the binders. Assuming the 12th century chronology of the chapel's erection to be correct, it was found that the applied method did not provide the result which is consistent with archaeological estimations. [ABSTRACT FROM AUTHOR]