# Investigations on an Ancient Mortar from Ulpia Traiana Sarmizegetusa Archaeological Site, Romania
## 3 Results
### Radiocarbon Dating  
Considering all the interpretations of the previous analyses, a procedure for extracting small portions of lumps (a white material with the apparent consistency of calcite) under a microscope was followed. The total sample came from multiple sub-samples at several points in the material. After homogenization, we proceeded according to Section 2.2.  
The calibration of the radiocarbon date (histogram) using the CHS method is presented in Figure 16.  
Based on the results obtained using the CHS, the age period falls within calAD 662-822, with a confidence level of 95.4%. In the CHS, only CO\({}_{2}\) from inorganic materials is released.  
To verify the consistency of the radiocarbon date, a second round of dating was performed using the EA. In this case, without a prior pre-treatment of the samples, a radiocarbon date was obtained for all the forms in which carbon-14 is present (bio/organic and bio/inorganic). The second calibrated radiocarbon date is shown in Figure 17.  
Figure 16: Histogram for lumps extracted from Ulpia Traiana mortar (UT), using CHS [29].  
Figure 17: Histogram for dating lumps extracted from Ulpia Traiana mortar (UT), using EA [29].  
This time, the age period falls within calAD 652-775, with a confidence level of 95.4%.  
Both methods offered consistent results, reinforcing the reliability and accuracy of the dating outcome. Combining the CRA values by using the R_Combine function in OxCal [29] demonstrates the 'contemporaneity' of the samples. The most likely interval becomes narrower, namely between calAD 662 and 775 (Figure 18). The difference of approximately 100 years (within the limits of measurement errors) places it in the interval of 100-200 years, acceptable for the hardening of mortar in masonry.  
The radiocarbon results confirm that it is not a modern intervention/late repair. The position of the sampling point excludes lateral contact producing C-14 exchanges during the lifetime of the monument [49], sustained by previous analyses. So, it may represent a real age, but not one supported by the archaeological or historical information accepted until now, even if 100-150 years are added (see above). It is most likely an apparent age depending on the distance from the surface, denoted by S2 pyrogenic calcite and S3 C-S-H carbonation mechanisms, as explained in Section 1. CaCO\({}_{3}\) from carbonated C-S-H/C-S-A-H, which could take up an unknown number of years, may be taken into consideration, if the degree of carbonation of the material is controlled by the carbonation depth (mechanism S3) [12]. As presented in the literature, the phenomenon of delayed mortar hardening is common to these water-resistant materials, leading to apparent ages more recent than its application in masonry [50]. Nowadays, similar materials in the cement class also exhibit this phenomenon. To modify the hardening period, retarders or accelerators, such as calcium lignocellulosic or sodium gluconate, are added [50; 51].  
Support for an apparently rejuvenated age or apparently obsolete one is given by the interpretations of the results obtained with the other investigation methods. The absence of geogenic calcite excludes the S1 mechanism stated in Section 1. A mortar hardened in 100-200 years (given the sampling position, from inside the plinth) and rejuvenated (through surface exposure after the statue reached the ruin phase) cannot be taken into consideration (mechanism S4 Ca(OH)\({}_{2}\) recarbonation).