THE ASSESSMENT OF PROTECTION TREATMENTS ON HIGHLY POROUS STONES WITH RELATION TO THE SUSTAINABILTY OF THE INTERVENTIONS ON THE HISTORICAL BUILT HERITAGE

Angela Calia1, Mariateresa Lettieri2, Loredana Matera3, Maria Sileo4

CNR- IBAM (Institute for the Archaeological Heritage), via Monteroni, 73100 Lecce, Italy

1 a.calia@ibam.cnr.it; 2 mt.lettieri@ibam.cnr.it; 3 l.matera@ibam.cnr.it; 4 m.sileo@ibam.cnr.it

ABSTRACT

Porous stones as building materials need the surface protection, especially against the water penetration. Large scale treatments with chemical products on the built historical heritage and the intrinsic features of these materials draw the attention towards the sustainability of these interventions. Sustainability is undoubtedly in terms of human and environmental impact of the used products, but also in terms of costs, especially for very porous stones that can absorb noticeable amounts of products. Finally the problem is to ensure satisfactory performance and basic requirements in terms of harmfulness of the products that in the most of the cases have no reference to the highly porous stones application.

In this work, two commercial water-based products for stone protection, respectively an alcoxy-siloxane with low molecular weight and a modified organo-silane, have been tested in order to assess their performances on some stones with high porosity (between 30 and 45%) and different petro-physic characteristics. The evaluation of the treatments was based on the assessment of the physical properties of the treated stones, i.e. colour, waterproofness, water vapour permeability and capillary water absorption. The results showed that the high porosity, the presence of coarse pores and the roughness of the surface are critical aspects with relation to the superficial treatments concerned in this study.

Key-words: Stone protection, porous stone, physical properties.