Franzoni, E; Sassoni, E; Scherer, GW; Naidu, S
Since the effectiveness of stone consolidants significantly
depends on the weathering level of the stone samples on which they are tested, in this study the
suitability of heating stone to high temperature, as an artificial weathering method to induce
controllable microstructural, physical and mechanical alterations, was investigated. Three
lithotypes with different characteristics were used: Giallo Terra di Siena (GS, a highly porous
calcareous sandstone), Globigerina limestone (GL, a highly porous limestone) and Pietra Serena
(PS, a porous quartzitic sandstone with low porosity). The lithotypes were characterized in terms
of mineralogical composition, pore size distribution and water absorption, as well as dynamic
modulus, static modulus, compressive and tensile strength. They were then heated for 1 hour, in
different conditions: (i) dry samples were heated to 100, 200, 300 and 400 degrees C; (ii)water-
saturated samples were heated to 200 degrees C; ( iii) water-saturated samples were heated to 200
degrees C and, after cooling to room temperature, re- heated to 400 degrees C. After heating, all
the lithotypes experienced an increase in open porosity and water absorption, as a consequence of
the anisotropic thermal deformation of calcite crystals. Correspondingly, GS and GL exhibited an
increasing reduction in mechanical properties for increasing heating temperature. PS, on the
contrary, exhibited an increase in compressive and tensile strength, which was attributed to
chemical-physical transformations undergone by secondary mineralogical fractions ( clay minerals,
etc.) at high temperature. All things considered, heating proved to be a fairly effective and
reproducible method to cause artificial weathering in stone samples for the testing of
consolidants. However, depending on the microstructural characteristics of the lithotypes, the
effectiveness of heating may vary significantly, which requires a case-by-case adjustment of the
most suitable heating procedure and the development of complementary methods for artificial
weathering. (C) 2013 Elsevier Masson SAS. All rights reserved.