Influence of surface temperature changes on Maltese limestone

Abstract

Once quarried, limestone commences to deteriorate and weather. The Maltese building trade has been utilising locally quarried stone for thousands of years. A number of megalithic structures and complexes still exist today. Weathering processes affecting these and other structures is resulting in irreparable damage and loss of irreplaceable world heritage. A number of studies in order to establish how the weathering process affects Maltese Limestone have already been carried out. The effects of pollutants and salt crystallization were looked into in detail. Such research also established a number of stone properties including aggregation and mechanical performance. Nevertheless, little is known regarding thermal properties of Maltese Limestone. To date only one study concerning thermal conductivity of Globigerina limestone has been carried out. This study attempts to shed more light on the subject. The current study concentrates on the main stone types used for building purposes within the Maltese Islands. The behaviour of Globigerina Limestone, Upper Coralline Limestone and Lower Coralline Limestone with respect to the maximum surface and subsurface temperatures that such stones experience when subjected to comparable temperature changes are looked into. Using 70mm cubes embedded in a jacket of polystyrene stone, temperatures were recorded for each of the three rock types subjected to three different surface ranges. Surface and subsurface temperatures were measured to determine differences in stone response to temperature changes with reference to thermal properties and thermal strains. Globigerina and Lower Coralline Limestone proved to provide more insulation than Upper Coralline Limestone while the latter experienced a greater time lag between surface and subsurface. Suggestions for future studies include direct heating, measurements of expansions and contractions at different points.