Porosimetric changes and consequences for damage phenomena induced by organic and inorganic consolidation treatments on highly porous limestone

Abstract

Surface consolidation treatments on stone materials induce relevant modifications in the porous substrates that can potentially trigger deterioration phenomena not active in the same untreated materials. Unlike most protective products that form films on stone surfaces, consolidants must penetrate the first layers of the substrate in order to function, partially filling the voids of the porous network. Meso- and macro-porosities of Globigerina Limestone (Malta’s highly porous sedimentary stone), before and after treatments with several organic and inorganic consolidants were investigated by means of N2-BET (Brunauer–Emmett–Teller) analysis. BET total inner superficial area together with pore size distribution data gave interesting information on preferential distribution of different products inside the open porosity network. The treatment can produce in some cases small changes in total superficial area (inorganic treatment), in some others cases a dramatic reduction (organic) and also an unexpected relevant increase (ethylsilicate). Pore size distribution shows shifts towards lower pore diameters turning a predominantly macroporous system into a meso-porous one. These porosimetric changes have a direct relationship with the physical properties of porous building materials. In relation to the environmental context and the direct exposure to deterioration agents, the consolidation treatment can also have a negative impact for the conservation of works of art.