# Investigations on an Ancient Mortar from Ulpia Traiana Sarmizegetusa Archaeological Site, Romania
## 3 Results
### Thermal Analysis Results  
DSC-TGA analyses were performed on two samples, extracted from a white area (presumably with a higher concentration of calcite, denoted as N)--Figure 14--and from a grey area, denoted as G, Figure 15. Both samples performed similarly at heating; however, the amplitude of mass changes and recorded enthalpies are different.  
As can be seen in Figure 14 for the white area (N sample, lumps), a first mass change occurs up to 250 \({}^{\circ}\)C (solid line for TGA) with a peak at 96.6 \({}^{\circ}\)C (dashed line for DSC). It corresponds to the elimination of adsorbed water, with the samples not being previously heated to 110 \({}^{\circ}\)C [37]. The second mass change occurs up to 600 \({}^{\circ}\)C. It corresponds to dehydroxylation of clay minerals or C-S-H/C-S-A-H, which is related in the DSC diagram to the peak at 446 \({}^{\circ}\)C [38]. No quartz transformation was identified at 573 \({}^{\circ}\)C, giving a sign of its absence in the lumps [39].  
The most important loss in weight of 28.28% was recorded in the range of 600-830 \({}^{\circ}\)C, with a peak at 773.6 \({}^{\circ}\)C. This could be attributed to the decarbonation of the calcite from lumps [38]. Compared to the theoretical value of 43.97%, we found a percentage of around 64% calcium carbonate. A secondary peak was not identified at approx. 875 \({}^{\circ}\)C, generally associated with pure geogenic calcite or the polymorphic transformation of micaceous minerals, which is a sign of their absence [38; 40]. An exothermic peak appears at around 904 \({}^{\circ}\)C and can be attributed to the final burning of organic wastes [41].  
Figure 14: DSC-TGA results of the specimen extracted from a white area, presumably a lump.  
Figure 15: DSC-TGA results of a sample extracted from a grey area, presumably mortar binder.  
Concerning the grey area (Figure 15, G sample, mortar), the same losses at 94 \({}^{\circ}\)C, and up to 250 \({}^{\circ}\)C, can be found. Instead, the signal from approx. 446 \({}^{\circ}\)C disappeared. No quartz transformation was identified at 573 \({}^{\circ}\)C.  
As for the decomposition of carbonates in the range of 600-830 \({}^{\circ}\)C, it is observed that this occurs at 769.9 \({}^{\circ}\)C. The dissociation temperature will depend primarily on their mineralogical structure, and also on the type and amount of impurities. Increasing the total content of aluminum, silicon, and iron oxides will lead to a decrease in the decomposition temperature, as a result of the formation of solid, unsaturated solutions in CaCO\({}_{3}\)[38]. Compared to the theoretical value of 43.97%, we found a percentage of around 30% calcium carbonate, with possible different origins. A secondary peak was not identified at approx. 875 \({}^{\circ}\)C. An exothermic peak appeared at around 909 \({}^{\circ}\)C [40].  
As presented above, from the values recorded in Figures 14 and 15 (13% for G sample and 28% in N sample), the CaCO\({}_{3}\) concentration can be obtained: -29% for G sample (grey area) and 64% for N sample, i.e., in white areas, confirming the XRD (Figure 4) and EA results.  
A phase transformation can also be connected with lumps, at 446 \({}^{\circ}\)C, corresponding to the dehydroxylation of clay minerals or C-S-H/C-S-A-H. It does not show a phase transformation for quartz. The most important transformation is given in the range of 600-830 \({}^{\circ}\)C and is characteristic of calcium carbonate decomposition. Decomposition at a lower temperature in the mortar in comparison with lumps shows a greater 'flux' contribution of some mineral compounds. Geogenic calcite was not identified in this way either.