Salt crystallisation in porous materials: physicochemical aspects and effects of anti-scaling additives

The aim of this study was to investigate the mechanisms of crystallisation of some inorganic salts within porous substrates in order to explain the processes of alteration of the porous material surfaces in architectural/artistic conservation. In particular, attention was focused on the salts crystallization in the presence of some organo-aza phosphonates compounds, additives known as anti scaling agents, able to prevent and/or inhibit nucleation and growth of solid phases from saturated and supersaturated salty solutions. The applicative goal was to understand how the action of these additives could represent an innovative methodology in the field of preventive conservation, in order to reduce and limit the damages on monuments, historical buildings and mural paintings deriving on the presence of crystallization/solubilization cycles. The experimental study was carried out investigating the physico structural properties, namely porosity, and the changes in morphology (by SEM and ESEM) due to salt crystallization (KNO4 and Na.SO4) within porous materials of artistìc/architectonic interest (stones, and mortars) and the effect on the anti-scaling additives in minimizing the damage effects on the porous materials