An Integrated Petrographic, Geomatic and Geophysical Approach for the Characterization of the Carbonate Rocks of the Calcari di Cagliari Formation

Abstract: Non-invasive techniques, such as close-range photogrammetry (CRP) and 3D ultrasonic
tomography complemented with optical and scanning electron microscopy and mercury porosimetry,
were applied to characterize the carbonate rock samples of the Calcari di Cagliari formation. The integrated
approach started with the computation of high-resolution 3D models of the carbonate samples
using the CRP technique to produce 3D high-resolution models texturized both with natural colors
and intensity. Starting from the 3D models from previous techniques, a 3D ultrasonic tomography on
each rock sample was accurately planned and carried out in order to detect the elastic properties of
such rocks and relate them to textural heterogeneity or internal defects. The results indicate that the
relationship between longitudinal velocity and rock properties is complex even in the same carbonate
formation. Understanding the relationship between the geomatic and geophysical responses in the
investigated rock properties, such as textural characteristics and especially structure and geometry of
pores, type of pores, tortuosity and cementing material, is important for many practical applications
and especially in the diagnostic process of the conservation state of monumental structures. The
integration of the above non-invasive techniques complemented by petrographical–petrophysical
data proved to be a powerful method to associate each lithotype with a different susceptibility to
degradation. The results presented in this paper demonstrate that the proposed integrated use of
complementary methodologies would guarantee the reproducibility of the measurements both at
the laboratory and field scale for the monitoring in time of the rock condition while giving a useful
contribution in making decisions on an appropriate remedial strategy.