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.