Analyses of the physical parameters correlated to bending phenomena in marble slabs

Publisher Summary This chapter analyzes the mechanical decay processes in stone materials, which are represented mainly by Carrara marble used in architecture, historical buildings, and monuments. These processes are related to the bending of marble slabs and architectural elements, which are affected by creep processes. Mechanical and physical parameter analyses were carried out on some of the representative slabs and significant variations were found in the mechanical resistance, density, and porosity values. The systematic analysis was carried out on over 80 slabs from some cemeteries in Florence. Other slabs and bars were prepared from quarry material; and they were subsequently bent with long term flexure load tests. The study then focused on the microscopic analysis of thin sections and on the analysis of SEM images of various points of the slabs. These analyses allowed to identify the various structures of the blasts; the evolution of the deformations and discontinuities; and the presence of cracks and the microfractures caused by pressure or disconnections, etc. The mechanical analysis of creep phenomena and the related numerical simulations show a very complex behavior. Long term tests carried out on slabs taken from quarries show noticeable reductions in the creep fracture stress values after quite short testing periods. The experimental tests have highlighted a viscous-plastic behavior, which finds a good correspondence in the analytical simulation adopted for the phenomenological reproduction of creep response. This is also well-suited to the time-delayed response of the ancient slabs. Finally the damage analysis developed with reference to the degradation tertiary phase showed clear non-linear accumulation effects. The strength decay creep model defined in this way can easily be applied to more general analyses of the long-term behavior of marble slabs. The chapter illustrates the results and discussions with the help of tables and graphs.