Relationships between the petrographical, physical and mechanical properties of some Italian sandstones

Sandstones quarried in the Firenzuola district (Florence, Italy) have been investigated in order to evaluate their outdoor durability. We have studied the relationships between mineralogical, petro- graphical, physical and mechanical properties. The sandstones from Firenzuola are characterized by a heterogeneity of mineralogical, petrographical characteristics that strongly affected the physical and mechanical properties. Simulation of different environmental conditions has been performed using accelerating ageing tests (freeze/thaw, salt crystallization, acid rains) and a comparison with the real cases of use of this stone in the urban, marine and mountain environments is proposed. This paper highlights how the mineralogical and petrographical characteristics affect the physical and mechanical properties: the presence of a high amount of carbonatic cement determines a low effective porosity; a prevalence of small pores and a high value of uniaxial compressive strength, while a high amount of clay matrix determines high effective porosity; a prevalence of larger pores and a low uniaxial compressive strength. These parameters, in turn, determine a different proneness of this material to decay. The most relevant cause of decay for these sandstones is salt crystallization, which determines a decrease in mechanical properties. This paper also stresses the need for new standard methodologies for evaluating the tendency to decay of superficial portions of material such as the analyzed pavements.