Distinguishing Binder to Aggregate Ratio in Historic Lime Mortars from Cyprus through FTIR Analysis: Is it Really Possible?

This paper was presented at the YRA Workshop 2025 in Budapest.

This paper offers new perspectives on the use of Fourier-transform infrared spectroscopy (FTIR) analysis for the identification of calcite types in lime mortars. Calcite (CaCO3) is the predominant component of lime binders, which is obtained by burning limestone rocks or other calcareous materials. The resulting pyrogenic product is often mixed with geogenic and biogenic components during the production of the mortar. FTIR has proved to be an effective analytical tool in the distinction between pure geogenic, pure biogenic, and pure pyrogenic calcites; thus, this paper aims at demonstrating the potential of this technique in distinguishing also mixtures’ proportions. The methodology is based on previously published studies proving how the shape, height, and area of the main calcite peaks – in particular v2 and v4 – in FTIR spectra change according to the formation process of the calcitic material. The present paper reveals how the calculation of the v2/v4 area ratios, can indicate the presence of mixed types of calcites, and aid in estimating the percentages. The results obtained show how – in the presence of a valuable reference database – it is possible to distinguish ranges of limestone:lime mixtures. This methodological study was applied on a set of samples collected in the district of Paphos, in South Western Cyprus. The geogenic and biogenic samples are representative of the main geological formations and faunal species of the region, while the archaeological samples were collected at the site of Nea Paphos. The pyrogenic calcite specimens were produced in controlled laboratory setting.

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