Angela Calia

Ultrasonic pulse velocity for the evaluation of physical and mechanical properties of a highly porous building limestone

UPV as non-destructive technique can effectively contribute to the low invasive in situ analysis and diagnosis of masonry elements related to the conservation, rehabilitation and strengthening of the built heritage. The use of non-destructive and non-invasive techniques brings all the times many advantages in diagnostic activities on pre-existing buildings in terms of sustainability; moreover, it is a strong necessity with respect to the conservation constraints when dealing with the historical-architectural heritage. In this work laboratory experiments were carried out to investigate the effectiveness of ultrasonic pulse velocity (UPV) in evaluating physical and mechanical properties of Lecce stone, a soft and porous building limestone. UPV and selected physical-mechanical parameters such as density and uniaxial compressive strength (UCS) were determined. Factors such as anisotropy and water presence that induce variations on the ultrasonic velocity were also assessed. Correlations between the analysed parameters are presented and discussed. The presence of water greatly affected the values of the analysed parameters, leading to a decrease of UPV and to a strong reduction of the compressive strength. A discussion of the role of the water on these results is provided. Regression analysis showed a reliable linear correlation between UPV and compressive strength, which allows a reasonable estimation of the strength of Lecce stone by means of non-destructive testing methods such as the ultrasonic wave velocity. Low correlation between UPV and density was found, suggesting that other factors than density, related to the fabric and composition, also influence the response of the selected stone to the UPV. They have no influence on the UCS, that instead showed to be highly correlated with the packing density.

Integrated prospecting in the crypt of the Basilica of Saint Nicholas in Bari, Italy

In this paper, we present the results of non-destructive integrated geophysical surveys (ground penetrating radar (GPR) and seismic sonic) performed in the crypt of the Basilica of St Nicholas in Bari, Italy. The aim was twofold, namely to investigate the consistency of restoration work performed in 1950 and the presence of features of archaeological interest. The GPR technique has also been exploited to characterize the subsurface water content under the crypt. In particular, the existence of buried anomalies, probably due to the restoration work, has been identified. Moreover, by means of an electromagnetic-wave velocity analysis, an estimation of the volumetric water content under the floor has been achieved. The results indicate the main causes of the deterioration and have provided significant information for the safeguard of this historical building. Furthermore, the GPR survey allowed us to identify some anomalies buried under the crypt that are probably of archaeological interest. Finally, both sonic tomography and a GPR survey have been performed on an important mosaic, and have enabled us to identify probable ?internal? reasons for its decay.

Non-destructive and laboratory diagnostic study on the mosaic of the crypt of St. Nicholas (Bari, Italy)

The crypt of St. Nicholas in Bari, Southern Italy, is a building of cultural worldwide importance. Inside the crypt a mosaic develops on the apsidal floor and along a parietal seat placed along the apsidal masonry, in the form of cladding. A surviving portion of the mosaic pavement is also preserved in the right lateral chapel. Integrated non-destructive survey and laboratory analyses were undertaken for the diagnostic study of the mosaic. GPR prospection was successfully applied to the study of its conservation state, that is strictly related to the condition of the subsoil, in particular to the presence and distribution of water. The presence of water, whose rise interests also some portions of the masonry and water content distribution were identified by the results of electromagnetic wave velocity analysis in GPR data. The decay visible on the tesserae evidenced widespread spalling and crumbling as typical forms that selectively affect the different materials of the tesserae of the mosaic. Samples taken from them were investigated by optical microscopy, X-ray diffraction, ion chromatography, infrared spectroscopy and thermogravimetric analyses, in order to identify the constituent materials and the products of their decay. The application of the integrated methodologies showed its effectiveness in order to acquire a quite complete knowledge for diagnostic purpose. Decay appeared to be due to the combined presence of water and soluble salts and it has different effects depending on the materials characteristics.

Mechanical Characterization of Building Stones through DT and NDT Tests: Research of Correlations for the In Situ Analysis of Ancient Masonry

In this paper, the use of ultrasonic pulse velocity (UPV) testing as a reliable technique to determine the compressive strength of a calcarenitic stone typical of Salento (South of Italy), known as Lecce Stone (LS) has been investigated. The scope of the experimental research is to establish correlations between the results obtained by non-destructive and destructive tests, in order to reduce the use of destructive methods within the diagnostic procedures for the mechanical analysis and qualification of ancient masonries. Furthermore, the presence of water as a variable affecting the test was investigated. The results of the tests show that the UPV values are well correlated with the compressive strengths and this method showed to be efficient in predicting the strength of LS.