Characterisation of the State of compression of Pietra D'Istria elements by Non Destructive Ultrasonic Technique

摘要

About the 80% of the Venetian monuments and edifices have been built up, decoratedrnor covered by limestone coming from quarries located in the Istria peninsula.rnNowadays, these pits are still exploited for the extraction of Pietra d'Istriarnstone, and their veins have maintained the main characteristics unchanged.rnThis means that through the studying of the properties of limestone produced byrnthese quarries in our days it could be possible to gain some new insight also intornthe material widely used in the Venetian architecture during past centuries.rnStarting from these assumptions, the purpose of this work was to characterise thernmaterial extracted from the above mentioned limestone quarries so to obtain arncomplete understanding of its properties and therefore to achieve a betterrncomprehension of the issue concerning the anamnesis, diagnostic, monitoring,rnconservation and restoration of numerous edifices in Venice.rnIn order to organise the working program, the collaboration with the Kamen Pazinrnquarries has been essential for the supply of Pietra d'Istria samples.rnAfter an initial evaluation of material main physical characteristics, therndependence of ultrasonic velocity on the compression state has been verified usingrndifferent waves frequencies (55 and 120 kHz).rnVelocity and the correspondent oscillogram have been recorded every 10 MPa duringrncompression tests till fracture.rnVariations in ultrasonic waves velocity and shape have been analysed and studied sornto identify any possible correlation with the load borne by the samples.rnThanks to the results obtained, it has been possible to achieve the purpose of thisrnlaboratory study, i. e. to gain some insight into main characteristics of thernOrsera Pietra d'Istria and, in particular, how its ultrasonic properties vary overrna range of effective pressure.