WEATHERING E VULNERABILITÀ DI MATERIALI LAPIDEI IN CONTESTI URBANI: IL CIMITERO STORICO DI CAGLIARI

P. Meloni1,2, D. Isola3, G. Carcangiu4, A. Bonazza5, L. Selbmann3, L. Zucconi3, F. Manca1,2, R. Faedda1,2, O. Cocco1,2, G. Toreno2, A. Murru1,2

1 Dipartimento di Ingegneria Meccanica, Chimica e dei Materiali, Università degli Studi di Cagliari, Piazza d’Armi, 09123 Cagliari, Italy, meloni@dicm.unica.it

2 Università degli Studi di Cagliari, Laboratorio Colle di Bonaria, Via Ravenna snc, 09125, Cagliari, Italy, meloni@dicm.unica.it

3 Dipartimento di Scienze Ecologiche e Biologiche , Università degli Studi della Tuscia, Largo dell’Università snc, 01100 Viterbo, Italy, isola@unitus.it; selbmann@unitus.it; zucconi@unitus.it

4 IGAG–CNR - Istituto di Geologia Ambientale e Geoingegneria, Sezione di Cagliari Piazza d’Armi, 09123 Cagliari, Italy, gianfranco.carcangiu@cnr.it

5 ISAC-CNR - Istituto di Scienze dell’Atmosfera e del Clima, Via Gobetti 101, 40129, Bologna, Italy, a.bonazza@isac.cnr.it

ABSTRACT

Outdoor architectural heritage is constantly exposed to weathering processes and to irreparable damages caused by pollutants and biological agents. The long time analysis carried out at the historic cemetery of Bonaria in Cagliari, characterized by its numerous chapels and sculptures of great artistic value, documented these complex degrading processes. In addition, the sea salt aerosol due to the closeness to the sea worsens the deterioration of the cemetery area. In this research marbles and other ornamental stones were studied as well as decorative elements of aristocratic chapels and some important outdoor monuments. In particular, IR thermographic analyses were carried out in order to show the thermal stress of the structures, microbiological ones to isolate the biodeteriogen agents involved and chemical and minero-petrographic analyses were performed to study the products of alteration. The obtained results allowed us to outline a sufficiently clear picture of the ongoing degradation process. Besides in situ analysis, various laboratory studies were carried out to verify the effect of surface strengthening and marble protection through remineralizing treatments aimed to improve the cohesion of the materials. Microbiological analyses revealed a strong presence of black microfungi on marble surfaces both treated and untreated with biocides. It highlighted the need to find alternative and more effective methods for the restoration and preservation of the monuments.

Key-words: black fungi, weathering, marble, salts, pollution