An Innovative Methodological Approach for the Study of Ancient Cistern Waterproofing Mortar of Sagunto Castle

In this work, we present the results of the chemical, mineralogical and colorimetric characterization of the waterproofing mortars from the ancient cisterns of the Sagunto Castle (Valencia, Spain). The fortress presents 2500 years of human occupation and, given the lack of natural water sources, collecting and storing rain water was mandatory ever since. Nowadays, several cisterns are found in the hill, and thus the application of analytical approaches can help in characterizing each layer within the cultural phases of the Castle’s history (Iberian, Punic, Roman, Islamic, Medieval, Modern or Contemporary). Mineralogical analyses were carried out employing X-ray diffractometry and mid-infrared attenuated total reflection spectroscopy, and, on the other hand, the portable energy dispersive X-ray fluorescence spectroscopy was employed to obtain the concentrations of major and minor chemical elements. Colour features of the samples were identified by smartphone photo processing to observe possible relation between colour and waterproofing mortar compounds. Last, Raman spectroscopy was employed to analyze the different phases present in the samples. Multivariate statistics were employed to identify different waterproofing mortar layers and develop hypotheses concerning different construction phases and compare their manufacturing processes. Analytical results allowed to find common patterns among different cisterns and mortar layers, and colorimetric analyses showed good potential as an additional fast, cheap and non-destructive source of information for studying these types of samples.