# Investigations on an Ancient Mortar from Ulpia Traiana Sarmizegetusa Archaeological Site, Romania
## 5 Conclusions  
A set of analyses were applied on an ancient lime-based, porous concrete (denoted as mortar) extracted from the central part of [PERSON]'s statue, Ulpia Traiana archaeological site, Romania. This sample underwent complex characterization and we can offer the following conclusions, very useful in defining this ancient construction material:  
Mainly albite, quartz, and calcium carbonate, along with kaolinite, were identified in XRD/SEM-EDAX performed on the binder matrix. Visible biotite grains of 1-2 mm in size were also observed, along with other aggregates (of various sizes and natures), all of them well-embedded in the binder matrix. The'specimen' surfaces and also fracture or fresh-cut surfaces contained white, up to millimeter-sized lumps made of more than 60% CaCO\({}_{3}\). This carbonate may appear due to carbonation of Ca(OH)\({}_{2}\) over time, generally within 100-200 years. In addition, all surfaces, old or newly made by fracturing/cutting, were covered with a white, thin layer of carbonate, which appeared in SEM images as submicronic, spherical, and uniformly sized CaCO\({}_{3}\) grains. The origin of this carbonate may be the carbonation of the possible C-S-H hydrates formed within the binder matrix; this process, depending on depth, may have taken place in over 400 years. The pozzolanic reaction is suspected, as very small grains of silica (less than 150 um in size) were detected. FTIR analysis confirmed the presence of all previously identified minerals and suggested, based on the values for the ratio of the infrared absorption peaks, \(\frac{v_{2}}{v_{4}}\cong 8\) for lumps and \(\cong 5.7\) for binder, that the origin of the calcite in the examined specimens is pyrogenic (for reference, geogenic, natural calcite has a low ratio: \(\frac{v_{2}}{v_{4}}\cong 3\)). No calcium hydroxide was found, proving the lack of secondary calcite, much younger, in the formation. Gamma spectrometry offers a new option for investigating a monument's dynamics, using \({}^{137}\)Cs as a radiotracer for over the last 75 years. Naturally occurring radionuclides such as \({}^{40}\)K, \({}^{232}\)Th (\({}^{228}\)Ac), and \({}^{226}\)Ra strengthen the hypothesis of using local materials and not of bringing volcanic ash or pozzolanic materials from Italy. Certain information was useful for the selection of datable material, namely, the so-called lumps. The history of this statue is well-documented, with its construction being placed in the 2 nd century AD, so the radiocarbon date was surprising. Radiocarbon dating placed the material within the calAD 662-775 interval, with a confidence level of 95.4%, although questions arise as to whether this is a real age or an apparent one. What should have been a routine analysis, supported by other investigations, has become a case study that shows the limitations of radiocarbon dating. The analyses demonstrated that there is no geogenic calcite, that the mortar has reached maturity, and that there are no phenomena of decarbonation with recarbonation to secondary calcite (within the limits of detection of the methods used). The fragment taken from the center of the exposed surface, the calcite to be dated, comes from the carbonation of excess slaked lime interconnected with the carbonation of C-S-H hydrates. The latter process is time-dependent and governed by the distance from the outer surface, with the equilibrium being reached within hundreds of years. No organic remains were detected, which could lead to rejuvenation phenomena. In this case, the archaeological context and the evolution over time of the statue, which are well-known, could provide a starting point for better quantifying the phenomenon of delayed hardening of mortar over time. Further laboratory investigations, such as analysis in thin sections, CL, or OSL, could provide additional arguments to validate the findings, especially serving to disprove the existence of secondary and geogenic calcite. Conceptualization, Z.D.G. and C.A.S.