Investigation of Test Specimen Size and Shape on Absorption Measurements of Granite Dimension Stone

Abstract

Absorption is an important property of rocks, as it is indicative of the capacity for assimilation or incorporation of water by the stone material, which in turn may influence the durability of dimension stone in the built environment. It is strongly associated to the rock type and thus to the related petrographic characteristics. Regarding igneous and metamorphic rocks, the lack of pores is responsible for typically low absorption values. Laboratory determination of absorption normally involves specimens with dimensions greater than 50 mm. However, when used effectively as flooring or cladding, dimension stones are cut into slabs or tiles with thicknesses ranging from 20 to 30 mm. Thus, to investigate a possible influence of the thickness on the absorption of granitic dimension stone, laboratory determinations were conducted on test specimens of two different sizes and shapes (cubic and flat). The differences in test results between cubic and flat specimens show slightly higher absorption in flat specimens than cubic ones, indicating that the stone processing can modify its absorption characteristics. Regarding the stone type tested, granites, usually sound, present a tendency to greater absorption than gneisses, generally weathered, an indication of their relative brittleness to stress conditions. Moreover, these rocks would present increased and modified microcracking patterns in response to the procedures for quarrying or processing dimension stone, or both.