Multianalytical approach to evaluate deterioration products on cement used as consolidant on lithic material: The case of Tello Obelisk, Lima (Peru)

Abstract

Over years, numerous consolidation formulations and procedures have been developed and tested on lithic materials. It was clearly proven that some consolidation protocols applied on stone monuments years ago were not the best ones, jeopardizing the state of conservation of the intervened artwork. An example of this was the use of modern cement to fasten the Tello Obelisk (Lima, Peru) from its base and to repair a fracture visible in its upper part in the year 2010. The Tello Obelisk is a prismatic granite monolith (2.52m high and 0.32m width) belonging to the archaeological site of Chavin de Huantar in north-central Peru (actually in the National Museum of Archaeology, Anthropology and History of Peru, Lima). According to the historic knowledge, this sculpture is probably a Wanka or an object of religious cult and belongs to the Early Horizon period (900BCE to 200BCE). After some years since this consolidation, the used cement suffered from structural problems, since cracks and cement material loss were observable, compromising its strengthening. This work is focused in the characterization of the cement material used in the 2010 consolidation of the Tello Obelisk. For that purpose, different cement fragments used in its consolidation were analysed in the laboratory by micro-Raman spectroscopy, X-ray Diffraction (XRD), X-ray fluorescence spectroscopy (wavelength and energy dispersive) in order to determine the original composition and deterioration products present in the cement, which can be responsible of future problems in such kind of stone monoliths.