Micro Destructive Analysis for the Characterization of Ancient Mortars: A Case Study from the Little Roman Bath of Nora (Sardinia, Italy)

Fabio Sitzia,Massimo Beltrame,Carla Lisci,José Mirão

doi:10.3390/heritage4030144

Abstract

In this work, a protocol of a partially invasive sampling for the archaeometric characterization of ancient mortars from the little Roman Bath of Nora (Sardinia, Italy) is presented. Optical microscopy and different analytical techniques such as X-ray diffraction, X-ray fluorescence, thermo-gravimetric analysis, and physical/mechanical tests have been carried out on the mortars. These analyses were performed to investigate the chemical composition, alteration products, and binder pozzolanic activity. An innovative method of image analysis has been tested to obtain information about the size and shape of both the mortar aggregates and the binder/aggregate ratio. This new particle-size analysis has two different advantages: (i) it saves a huge volume of material compared to a classic granulometric classification through its use of a sieve and (ii) is eco-friendly in respect to the environment by saving a large volume of liquid waste derived from the acid attack for the separation of the insoluble aggregate from the soluble binder, as would be done for a common sieving. Results show a local provenance of the aggregates. The use of two different limestones for the mortars’ binder production was detected and probably this raw material belongs to the nearby Roman town of Karales (current day Cagliari).

Highlights

In heritage materials research, sampling is important to develop a specific analytical protocol to obtain different data sets
The authors undertook a series of micro-destructive analyses for the complete characterization of the ancient mortars from the little Roman Bath of Nora (Pula, Italy)
27 samples comprised of 12 mortars, 6 alteration layers, 5 stones, and 4 bricks were collected in the little thermal Bath of Nora to attain a better understanding of the construction materials employed in the site

Summary

Introduction

In heritage materials research, sampling is important to develop a specific analytical protocol to obtain different data sets. It is extremely important to balance the volumetric representativeness of the specimen to acquire the required information. In this manner, an analytical protocol can be developed and the artifacts or structures do not suffer any visible damage [4]. The authors undertook a series of micro-destructive analyses for the complete characterization of the ancient mortars from the little Roman Bath of Nora (Pula, Italy). The building is in the eastern sector of the Roman city of Nora

Methods

Results

Conclusion