Abstract
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 soll. Two types of fresh franka (bajda -white- and safra -yellow-), as well as fresh soll 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. Soll 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, as aqueous solutions at different concentrations. Both treated and untreated stones were then subject to salt crystallization tests, using sodium sulphate in different concentrations. For the untreated stones, even after only one salt cycle, faster and more pronounced deterioration was observed for the soll samples as opposed to the franka ones. In the case of the treated stones, less deterioration with almost no damage was observed as opposed to non-treated ones. The presence of even very low concentrations of the inhibitor thus helps crystallization to occur on the stone surface and not within the pores. These encouraging results led to the conclusion that salt inhibitors can be used to treat salt-infested stone. Further research in this respect, also using NaCl/NaHCO 3 , is continuing.
Highlights
The Maltese Islands consist of two main islands, Malta and Gozo, as well as a small number of islets
Most monuments and vernacular architecture, as well as modern buildings, are built of the local Globigerina Limestone, one of the few natural resources of the Islands. This stone can be described as a typical "soft limestone", very easy to carve and shape
The Globigerina Limestone Formation outcrops mainly in the central and southern parts of the main island of Malta, and in the western part of the smaller island of Gozo. This Formation is stratified into thick beds at outcrop
Summary
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 weathered soll. Two types of fresh franka (bajda (white) and safra (yellow)), as well as fresh soll stone blocks, were obtained, based on the identification by quarry owners. 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. (*) Universidad de Malta (Msida, Malta) (**) Universidad de Perusa (Perusa, Italia) (***) CISTeC, Universidad de Roma La Sapienza (Roma, Italia)
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