Petrographic and Chemical–Mineralogical Characterization of Mortars from the Cistern at Amaiur Castle (Navarre, Spain)

Abstract

Mortars from the cistern in Amaiur Castle (Navarre, Spain) were analysed to assess the mortar manufacturing process and application techniques. To this end, optical microscopy, scanning electron microscopy (SEM), thermogravimetric analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Raman microspectroscopy, and Fourier transform infrared spectroscopy (FTIR) were performed. The study of both structural and plaster mortars from Amaiur Castle cistern show patterns/rules in the mortar manufacture according to the specific construction requirements. A multilayer application technique was used for the construction of the cistern tank. Deliberate selection of the aggregate nature and grading contributed to mortar impermeability. Ceramic and silico-aluminous rock fragments were used as aggregates in the cistern tank to confer hydraulicity to the mortars, instead of carbonated aggregates as used in the vault. Aluminosilicated phases present in the aggregates led to the formation of amesite, which is a magnesium aluminosilicate hydrate (M-A-S-H) phase conferring hydraulicity to the mortar. Two types of additives were identified in the outer pigmented layer of plaster. Beeswax was the identified organic additive used to improve the impermeability of mortar, while hematite was the identified inorganic additive giving rise to the reddish colour of the layer.

Compositional Characterization and Chronology of Roman Mortars from the Archaeological Site of Arroyo De La Dehesa De Velasco (Burgo De Osma- Ciudad De Osma, Soria, Spain)

“…The reaction rim surrounding the crushed ceramics suggests the occurrence of aluminosilicate hydrated products formed by the reaction aluminosilicate phases in the presence of water with the calcium hydroxide. Although, hydraulic newformed phases were not easy to identify by XRD due to their low crystallinity and low concentration in the binder [73][74][75]. However, in the binder of cocciopesto layers, reflections at 7.03 Å and 3.51 Å can be attributed to amesite (Mg 2 Al 2 SiO 5 (OH) 4 ), which is a magnesium aluminosilicate hydrate phase (M-A-S-H) (Figure 5a).…”

“…Cocciopesto mortars have often been used for waterproofing cisterns and waterways [6,66,75,76]. The composite mortar made by packing cocciopesto-bearing and cocciopesto-free layers not only confer resistance to the moisture but also improve the mechanical properties and stability of mortars [67,77].…”

Characterization of Historic Lime Mortars from the Arch of San Martin to Identify the Construction Phases of the City Wall of Burgos (Spain)

“…Saltwater or other alkaline media and/or the presence of certain aggregates and clay minerals, usually stable under normal conditions, can develop para-pozzolanic phases [48,49]. Amesite constitutes a hydraulic phase, contributing to a decrease in the porosity and favoring the waterproofing behavior of mortar [50][51][52][53][54][55][56].…”

The historical mortars of the castle of Cifuentes (Guadalajara, Spain)

“…Sobre la caracterización de morteros específicamente en castillos y fortalezas se han realizado diversos trabajos de interés aplicando distintas técnicas analíticas en base a técnicas petrográficas [24], siguiendo esta línea de investigación, en España se han publicado estudios similares sobre castillos medievales [25][26][27].…”