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

SandstonesquarriedintheFirenzuoladistrict(Florence,Italy)havebeeninvestigatedinorderto evaluatetheiroutdoordurability.Wehavestudiedtherelationshipsbetweenmineralogical,petro- graphical,physicalandmechanicalproperties.ThesandstonesfromFirenzuolaarecharacterizedbya heterogeneityofmineralogical,petrographicalcharacteristicsthatstronglyaffectedthephysicaland mechanicalproperties.Simulationofdifferentenvironmentalconditionshasbeenperformedusing acceleratingageingtests(freeze/thaw,saltcrystallization,acidrains)andacomparisonwiththereal cases ofuseofthisstoneintheurban,marineandmountainenvironmentsisproposed.Thispaper highlightshowthemineralogicalandpetrographicalcharacteristicsaffectthephysicalandmechanical properties:thepresenceofahighamountofcarbonaticcementdeterminesaloweffectiveporosity; a prevalenceofsmallporesandahighvalueofuniaxialcompressivestrength,whileahighamountof clay matrixdetermineshigheffectiveporosity;aprevalenceoflargerporesandalowuniaxial compressivestrength.Theseparameters,inturn,determineadifferentpronenessofthismaterialto decay.Themostrelevantcauseofdecayforthesesandstonesissaltcrystallization,whichdeterminesa decreaseinmechanicalproperties.Thispaperalsostressestheneedfornewstandardmethodologies for evaluatingthetendencytodecayofsuperficialportionsofmaterialsuchastheanalyzedpavements.