Consolidation of globigerina limestone (Malta) by means of inorganic treatments: preliminary results

Soft limestones used as building materials in marine environment undergo fast and peculiar deterioration processes that seriously damage the historical and architectural cultural heritage of Mediterranean cities. The aim of the present work was to evaluate the effectiveness of inorganic compatible treatments on Globigerina Limestone (the local limestone of the Maltese islands) to assess their suitability for the conservation of stone. Barium hydroxide, Ba(OH)2.8H2O, ammonium oxalate, (NH4)2.(COO)2.H2O, and dispersion of calcium hydroxide, Ca(OH)2, in alcoholic medium were tested in the laboratory on two different qualities of limestone, the easily perishable Globigerina Soll and on the more durable Globigerina Franka. Changes in water-interaction properties were investigated through water absorption by capillarity and water vapour permeability tests. Colorimetric analyses were performed before and after the application of products. Morphology and distribution in the porous substrate of deposited phases were investigated by SEM-EDX and analysis of surface area (BET). Re-aggregating properties were evaluated by means of a microdrilling system.