Conservation and materials compatibility in the archaeological site of Viale Trieste 105 (CA)– Sardinia

Despite the deleterious outcomes resulting from the use of modern materials in the restoration, the problem of matter’s compatibility is still very much debated. An example is the archaeological area of Viale Trieste 105 in Cagliari (Sardinia), composed by a complex multilayered structures dating from IV-III century BC to VII century AD. In the 80s, to allow the construction of a parking, a reinforced concrete structure with side openings was built over the site. The absolute lack of planned preventive maintenance allowed the different agents of decay to perform their action against the emerging structures, as the contamination of reinforced concrete’s products of decay (alkaline sulfates). The design of recent restoration has required an accurate diagnosis and microclimatic monitoring of the site. The XRD revealed that the salts which contaminate structures are the alkaline sulfates, supporting the hypothesis that their origin can be derived from the degradation of the cement. The most diffused lithotype is the so-called “pietra cantone”, a biomicritic limestone whose microstructure favors the phenomenon of salt crystallization. The microclimatic monitoring has detected intense energy exchanges with the outside as regard the structures closest to the openings, suggesting greater risk of stresses and permitting the entrance of air pollutants. The results reveal a dramatic situation for the conservation of these archaeological structures, requiring imminent interventions.