Mechanical Behaviour and Properties

Abstract

The indentation technique is tailored here to the needs of a portable tool for in situ diagnosis of mechanical properties and damage of natural building stones. Indentation tests were performed in twelve natural building stones (calcarenites, limestones, sandstones, marbles) and mortars used for restoration. A wide range of mechanical and petrophysical properties with different failure mechanisms in indentation is thus represented. Indicatively, the Unconfined Compressive Strength (UCS) ranges between 3.1 MPa and 116 MPa and the tangent Young’s modulus E ₅₀ at 50% of the maximum stress in uniaxial compression ranges between 0.9 GPa and 50 GPa. The tests were performed with three indenter diameters, 1-, 2- and 3-mm, to analyze scale effects in the results, and at five different depths, as the technique will be used not only for surface measurements but also for measurements in the interior, at the bottom of a small drilled hole. Such measurements can provide information on stone damage with depth. The results are used to build correlation functions and databases between indentation parameters and stone stiffness and strength. The technique is applied to two marbles that had been artificially weathered with exposure to moisture and temperature cycles, and to a consolidated mortar, i.e. a mortar treated with a consolidant for improving its weathering characteristics.