Preserving The Great Mosque of Cordoba (Spain): Characterization of Natural Stone Based on Rebound Hammer and Ultrasonic Tests

The preservation of The Great Mosque of Cordoba (Spain) as a carrier of Andalusian collective memory requires innovative approaches to assess and maintain its structural health. Numerical models are commonly employed to accurately estimate the building's static and dynamic behavior, with the accuracy hinging on precise input data, including the mechanical properties of the building material. While The Great Mosque's materials have been examined archaeologically, no prior mechanical characterization has been conducted. Due to the impracticality of extracting specimens from the building, non-destructive testing emerges as a viable alternative for material characterization. However, the existing literature lacks the strong correlations necessary to interpret the non-destructive testing results for this specific material.

This research centers on two commonly used non-destructive methods: direct ultrasound testing and rebound hammer. The former assesses elastic ultrasonic wave propagation velocity, while the latter reflects the stone's superficial strength through a rebound index, both of which can be potentially correlated with the stone's compressive properties. Laboratory tests were performed on natural stone provided by the primary material supplier for the Mosque's restoration and rehabilitation works. Over 100 cubic and prismatic specimens were cut from the stone and subjected to non-destructive and destructive tests, including density, compression, tensile, and bending tests. Correlations were established between the non-destructive test results and key material properties like compressive strength.

To investigate the stone's anisotropy, tests were conducted in multiple directions. Destructive testing indicated isotropy for the studied properties, yet ultrasound test results did not corroborate this finding. Sensitivity analysis regarding specimen dimensions showed an impact on the results' dispersion but not on average property values.

While further studies are necessary to delve deeper into this matter, the proposed methodology and correlations display promise for in situ characterization of natural stone in heritage buildings, particularly The Great Mosque of Córdoba.