Dynamic modulus of elasticity measurements: an instrument for the factory production control of marble slabs

The recent Standards on natural stone require the execution of the Factory Production Control on finished products. This could be possible by means of a non-destructive technique that measures mechanical properties of rock materials if a correlation to a reference test prescribed for the Initial Type Testing is available. In this work, measurements of Ultrasonic Pulse Velocity and Fundamental Resonance Frequency have been executed on two different stones (Carrara marble and Vicoforte sandstone) in order to determine the dynamic modulus of elasticity and compared the results obtained. The accuracy of the FRF measurements in relation to the dimensions and the shape of the specimens and the test configuration have been studied, adding a several series of tests on different kind of specimens. The achieved results show that the FRF measurements are influenced by the effect of the surface dimensions towards the thickness, the length of specimen, the geometry of the test and the position of the transmitter on the slab. Repeated FRF measurements on the same specimens are requested to obtain more reliable results. The UPV measurements instead are accurate and give a dynamic modulus well correlated to the mechanical properties of the stone tested even with flexural strength measurements. For this reason could be a useful instrument for the FPC control