Rock Porosity and Durability: the Contribution of the Image Analysis

Rock weathering is strictly connected with the increasing of the porosity. There are different techniques to measure the porosity: the increase of voids accessible to water is therefore correlate with the increase of the decay. At the moment two methods have been widely used to evaluate the water absorption of a stone . The first method, described in EN 13755 Determination of water absorption in atmospheric pressure, measures how much water can get into the prismatic specimen from its 6 faces during the period of immersion in water until a constant while the second, named water absorption by means of a contact sponge, measures how much water can be absorbed by a flat surface in a defined time. Generally rock porosity increases with the increasing of artificial ageing but not always there is correspondence with the decrease of mechanical strength. The explanation is in the kind of the evolution of the porosity: so a reliable method to evaluate the kind of porosity is needed. In this work image analysis has been used used to investigated six kind of rock in the natural state and after natural weathering. This kind of technique, together with other more frequent test methods , add important information on the decay evolution of the stone.