Ultrasonic test on natural stone elements

Ultrasonic testing is a non-destructive technique used to determine the velocity of longitudinal mechanical waves propagating through stone elements (e.g., columns, lintels, and other structural components). The instrument measures the time required for an ultrasonic pulse to travel between one or more pairs of measurement points, in order to obtain information on the homogeneity of the medium along the tested path. Wave velocity is influenced by the presence of internal discontinuities, such as fractures or cracks, as well as by other factors, including moisture content and the distance traveled. Additionally, the propagation velocity can provide a qualitative indication of the stone’s strength, as it is closely related to its density and Young’s modulus, both of which correlate with compressive strength.
The testing equipment consists of a pulse generator, a pair of transducers, an amplifier, and an electronic timing device that records the time interval between pulse generation at the transmitter and its reception at the receiver. As in sonic testing, ultrasonic measurements can be conducted by placing the two transducers on opposite faces (direct transmission), on adjacent faces (semi-direct transmission) or on the same face (indirect or surface transmission) of a stone element.

Reference standard: UNI EN 14579:2005.