Controlling crystallization damage by the use of salt inhibitors on Malta’s limestone

The main building stone in the Maltese Islands is the Globigerina Limestone, of which the Lower member is commonly used. This occurs in two types, the durable franka and the more easily weathered soil. Two types of fresh franka (bajda (white) and safra (yellow)), as well as fresh soli stone blocks, were obtained, based on the identification by quarry owners. Their designation was confirmed by geochemistry. Physical and mechanical properties of the three were investigated, including uniaxial compressive strength, water absorption by capillarity, permeability and porosimetry. Porosimetry results confirmed outcomes of previous research work. Soli was found to have a lower overall porosity, but a high percentage of small pores with practically no large pores. Some of the tested stones were then treated with a non-toxic phospho-organic compound containing carboxylic moieties as a salt inhibitor and the corresponding non-phosphorylated compound.