Valutazione dei parametri petrofisici del Tufo giallo napoletano e della Pietra di Vicenza: indagini sperimentali finalizzate al recupero ed alla conservazione di materiali macroporosi

In the recent years the awareness of having an architectural heritage, rich but "fragile", produced a greater effort in order to preserve the building stones and/or improve their resistance to weathering. Aim of this research is the testing of two commercial product: an anti-hygro, a protective product which reduces the swelling ability of clay and zeolitic minerals and a polymeric consolidant (ethyl silicate) applied to Neapolitan Yellow Tuff (TGN), the oldest building material in the Naples area. Moreover, in order to better evaluate the mechanisms of stone consolidation, it was selected, for comparison, a porous sedimentary rock, Pietra di Vicenza, with a pore radii distribution similar to TGN. The two stones were saturated by immersion under laboratory conditions. Specimens were divided into test group: untreated, treated with consolidant and treated with antihygro and consolidant. Investigations were conducted before and after each treatment and included mineralogical and petrographic analyses (XRD, XRF, SEM), physical and mechanical determinations (porosity, pore radii distribution, capillarity absorption, water absorption (by immersion), ultrasonic wave velocity measurements, compressive strength, colorimetric measurements). Furthermore consolidated samples were subjected to ageing tests such as freeze-thaw cycles, salt crystallization tests and salt spray; in order to evaluate and measure the effectiveness of consolidation and to study changes in stone properties.