Mineralogical, chemical and thermal characterisations of ancient mortars of the church of Santa María de Irache monastery (Navarra, Spain)

Abstract

Ancient mortars used in the construction of the church of Santa María de Irache monastery have been studied. With the aim to characterise their binder and aggregate fractions, a complete characterisation has been carried out including chemical (rapid analysis, soluble salts and trace elements), mineralogical (structural characterisation and X-ray diffraction, XRD) and thermal studies (simultaneous differential thermal and thermogravimetric analysis, TGA-DTA). Lime binder, lime with dolomite phases and mixed mortars (lime and gypsum) have been determined. The approximate original composition of these classes of mortars have been presented. Advice about the employment of repair materials in a restoration are given. RésuméOn a étudié les mortiers employés à l'église du monastère de Santa María de Irache. On a réalisé une caractérisation complète à l'object de connaître le liant et l'agrégat, en utilisant l'analyse chimique (analyse rapide, sels solubles et éléments trace), l'analyse minéralogique Material and methodsThe sampling procedure for mortars has been carried out taking a part of the mortars with a chisel and throwing away the external portion of the joints, with the aim of obtaining nonaltered material.A total of 51 mortar samples were studied, belonging to different areas (Gospel lateral nave:MA, MB and MC zones of sampling; dome area: zone C; Epistle lateral nave: E, EI, EE and 3 ED zones; portico area: zone P) (Fig. 1). At least three samples of each architectural zone were taken to assure representative results.X-ray diffraction analysis was undertaken using a Bruker D8 Advance diffractometer (Karlsruhe, Germany), according to the diffraction powder method, with a CuK 1 radiation and 0.02 increment and 1 s/step, sweep 2 to 90, 2.The complete sample (binder and aggregate) ground in an agate mortar is dried until constant weight in a heater at 105ºC and then 1g of sample is taken for its subsequent analysis. The rapid approximate chemical study was carried out after attack with hot HCl 1:5 volume ratio (2 M) [4], followed by a titration with ethylenediaminetetraacetic acid (EDTA) (using murexide and eBT (eriochrome black T) as indicators) in order to determine calcium and magnesium concentrations. To establish the CO 2 content, a calcimeter was used. The chemical analysis of the main components in the complete samples was carried out after an alkaline fusion followed by traditional chemical methods [6][7]: calcium and magnesium contents as previously mentioned; sodium and potassium levels were determined by flame

Comparisons of ancient mortars and hydraulic cements through in situ analyses by portable X‐ray fluorescence spectrometry

“…Percent levels of Fe and trace levels of Rb have been reported previously in ancient mortars. [12,19] Elevated Fe levels in mortar are associated with hydraulic effects and thus confirms the visual identification of the floor material type as a www.interscience.com/journal/xrs hydraulic cement. [19] The trace Rb is indicative of detritic materials acting as aggregates in the mortar.…”

“…Zn has been reported previously in ancient mortars [12,18,19] but only at a trace level. The elevated Zn could be the result of sphalerite (ZnS) or smithsonite (ZnCO 3 ) in the material.…”

“…Zn and Rb have been previously reported at trace levels in ancient mortars and are most likely in detritic minerals used as aggregates in the mortar. [12,19,22] The Pb may be present from water used in the hydraulic cement preparation; a water system utilizing lead pipes was found partially intact at the site.…”

“…Trace amounts of elements Mo, Zn, Rb, Pb, Cd, Mn, Co, Cr, Cu, Ni, and others in ancient mortars as determined by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry have been previously reported. [12,18] These studies were on a limited number of samples and required dissolution of samples in acid prior to analysis. Similar trace metal profiles were observed for mortars within the same site, however, thus demonstrating elemental homogeneity in some mortars.…”

“…Similar trace metal profiles were observed for mortars within the same site, however, thus demonstrating elemental homogeneity in some mortars. [12,18,19] Also, trace elements in mortars from differing historical periods have been reported as they relate to identification of provenance of the raw materials. [19] Use of a portable and nondestructive instrument such as an XRF spectrometer could provide both major and minor elemental composition information while leaving the excavation site intact.…”