Thermal behaviour of weathered and consolidated marbles

Abstract

Abstract To optimize stone consolidation it is necessary to understand the mechanisms of weathering in marbles, and its control by the mineralogical composition and the rock fabric. A knowledge of how the stone consolidants affect the weathering mechanisms and if they are compatible with the stone is also an important consideration. The weathering of marble can begin with thermal stress whereby cracks are generated. To verify whether consolidation influences the thermal behaviour of marbles, we compared the behaviour of weathered and consolidated marbles. For the investigations four marbles were selected with various fabrics (e.g. texture, grain size, grain boundary geometry, etc.) and different weathering conditions. Three consolidation approaches were adopted: a solved polymethyl-methacrylate (PMMA sol ) dissolved in xylenes, a polysilicic acid ester (PSAE) and a total impregnation with a monomer methyl-methacrylate (PMMA poly ). Measurements of the porosity and effective pore size distribution evidenced a strong modification of the pore space by consolidation. Both PMMA approaches show a re-establishment of cohesion which can be determined by ultrasonic velocity measurements. By reaching the respective glass transition temperatures of PMMA sol and PMMA poly , a strong modification of thermal behaviour occurs. The PSAE consolidated marbles show only minor changes of dilatation, but due to its low bonding effect no significant cohesion between the crystals occurs.