Determining static elastic modulus of weak sandstone in Andalusian historical constructions from non-destructive tests: San Cristobal's stone

This work presents a relationship between static and dynamic elastic moduli for San Cristobal's stone, which was used to build some of the most representative historical constructions in Andalusia (Spain) during 15th-18th centuries, including religious, military and civil buildings. Numerical models are able to provide useful information in structural health assessment of historical constructions, but static elastic modulus is necessary to perform them. This is why it is particularly interesting to count on an equation to predict this parameter from others, such as dynamic elastic modulus, which can be obtained in situ and through tests based on wave propagation. A new relationship is proposed after having shown that equations previously defined by other authors are not valid for San Cristobal's stone. The proposed relationship in this work is based on a set of physical and mechanical experimental tests carried out in lab on 17 specimens directly extracted from support elements of Santiago's (Jerez de la Frontera, Cadiz-Spain). Linear, polynomial and nonlinear multiple regressions were considered, as well as the inclusion of other parameters, such as bulk density and porosity. However, an equation with a coefficient of determination of 0.95 was achieved with a simple regression where only dynamic elastic modulus was involved. This simple equation allows to predict static modulus of San Cristobal's Stone with a high level of confidence and only from one parameter, that can be obtained in situ through nondestructive techniques and respectfully to built heritage. Finally, a first approximation to the application on an ancient construction is provided. Six columns of the Monastery of San Jeronimo de Buenavista, in Seville (Spain) underwent tests based on the propagation of wave to determine in situ their dynamic elastic modulus. The In situ results for the dynamic elastic modulus are consistent with those obtained in lab.