=

OOUU=

SWrucWural Analysis of HisWorical ConsWrucWions – Jerzy Jasieńko (ed) © 2012 DPNH ProcławH PolandH ISSN 0860-2395H ISBN 978-83-7125-216-7

nr^kqfq^qfsb Mlkfqlofkd lc prmbocfCf^i abC^v bslirqflk fk mi^pqboba ^ka rkmi^pqboba lrqallop M^plkov Bitelli dabrieleNI Colla CamillaOI dabrielli blenaPI dirardi cabrizio4I rbertini crancescoR fn= masonry= materialsI= the= superficial= decay= is= a= widespread= problemI= both= when= the= masonry= is=unplastered=and=with=plasterK=Aggressive=environmental=agents=such=as=moisture=and=salts=trigger= the=damage=by=propagating= through=the=material=capillary=poresK= Although=studies= have=been=carried=out=on=salt= crystallization=and= their= damaging=effectsI= for= the=preservation= of= masonry=buildingsI=due= to=their=high=number=and=to=their=cultural=importanceI=it= is=required=to=better= investigate=the=phenomena=on =real =cases =in =their =specific =microclimaticK =cor =these =purposesI =it =would =be =important =to =have =at =disposal= testing=and=monitoring=tools=capable=of=following=the=evolution=of=these=processes=since=the=beginningK=oepeated=visual=inspections=are=commonly=used=to=monitor=the=superficial=decay=but=this=is=a= subjective= and= qualitative= techniqueK= ft= would= be= important= to= apply= image= based= diagnostic=techniques= capable= of= providing= quantitative= informationK= eighJresolution= laser= scanning= by=triangulation=technique=of=the=masonry=surface=has=the=advantage=of=being=contactless=and=rapidK=fn=an=experimental=set=up=in=BolognaI=ftalyI=largeJsize=brick=masonry=walls=were=builtI=stored=outdoors=and=exposed=to=weathering=over=O=summersK=fn=a=OJheader=brick=wallI=one=main=face=is=unplastered=and=one= plasteredK= Before= the= start= of= the= second= ageing= seasonI= moisture= and= salt= capillary= rise= was=simulated=by=lowJconcentrated=sodium=chloride=solution=EMKNB=JwtFK=qhe=aim=was= to=favour=solution=evaporation= and= salt= crystallization= and= provoke= material= damageK= Pa= data= acquisition= by=a=triangulation=laser=scanning=system=was=repeated=at=the=end=of=both=seasons=and=meshes=derived=from=point=clouds=data=comparedK=qhe= proposed= procedure= successfully= extracted= quantitative= information= about= areas= of= material=spalling=and=detachment=even=in=the=initial=phases=of=decayK===heywords: MonitoringI aecayI MasonryI iaser scannerI mlaster NK fkqolarCqflk ^ka obpb^oCe obnrfobMbkqp =qhe=material= decay=caused=by=aggressive=environmental=agents= is=a=widespread=problem=in=masonry=surfaces= both= when= they= are= unplastered= and= with= plasterK= qhese= degradation= processes= are= mainly=caused=by=water=which=may=penetrates=into=the=material=pores=in=different=ways=such=as=by=capillarityI=percolation= or= vapourK= qhe= water= is= also= responsible= of= the= transport= of= dissolved= salts= Eeventually=presentF=which=during=brine=evaporation=may=precipitate=as=crystals=on=the=external=material=surfaces=or=beneath=themK=ft=is=the=increase=in=size=of=the=salt=crystals=inside=the=pores=to=cause=tensions=eventually=to=overpass= the=material= resistance=threshold= xNI=OzK= qhis=phenomenaI= although=common= in=masonry=materials=is=rather=complex=as=the=resulting=damage=is=due=to=the=interaction=of=salts=with=the=specific=environmental=conditionK=peveral= studies= have= been= carried= out= on= salt= crystallization= and= their= damaging= effects= in= porous=materials=but=they=are=mainly=aimed=at=investigating=the=behaviour=of=single=material=units=by=means=of=laboratory= analysis= xPI= 4zK= fn= additionI= open= questions= are= still= remaining= iKeK= about= the= correlation=between=results=from=accelerated=aging=test=and=the=real=natural=damage=in=structures=or=about=proper=================================================N=mrofKI=afCAj=aeptKI=bngineering=cacultyI=rniversity=of=BolognaI=gabrieleKbitelli]uniboKit=O=arKI=CfofJbC=and=afCAj=aeptKI=bngineering=cacultyI=rniversity=of=BolognaI=camillaKcolla]uniboKit=P=mhKaK=studentKI=afCAj=aeptKI=bngineering=cacultyI=rniversity=of=BolognaI=elenaKgabrielli4]uniboKit==4=arKI=afCAj=aeptKI=bngineering=cacultyI=rniversity=of=BolognaI=fabrizioKgirardi]uniboKit==R=mrofKI=afCAj=aeptKI=bngineering=cacultyI=rniversity=of=BolognaI=francescoKubertini]uniboKit=

=

OOUV=

techniques= to=be=used= in=masonry= structures= for= successfully=monitoring= the= time=evolution=of= these=environmental=effectsK=joreoverI=for= the=preservation=of=masonry=buildingsI=due=to=their=high=number=and=to=their =cultural =importanceI =it =is =required=to=better =investigate =these=phenomena=directly=on=real =cases=in=their=specific=microclimatic=environmentK=oepeated=visual=inspections=are=commonly=used=to=monitor=such=superficial=decay=but=this=is=a=subjective=and=qualitative=techniqueK=qhusI= for= these= purposesI= it= would= be= important= to= have= at= disposal= nonJdestructive= testing= and=monitoring= tools= capable= of= quantitatively= detecting= and= following= the= evolution= of= these=processes=since=the=beginningK==Among=the=available=surface=imaging=methodsI=there=is=a=wide=range=of=tools=able=to=create=Pa=models=of= the=objects;= these=have=been=used=in= the= last= several=years= in=various=application= fields= Ecivil= and=mechanical= engineeringI= cultural= heritageI= medicineI= forensicsI= etcF= by=considering= various= range=of=object= sizes= at= different= scales= xRzK= konethelessI= two= basic=approaches= can=be= distinguishedW= imageJbased=systemsI=where=Pa=models=are=generated=using=digital=imagesI=and=rangeJbased=systems=that=use=scanning=systems=with=different=technologies=xSzK==qhe=acquisition=of=Pa=models=by=means=of= laser=scannersI= thanks=to=the=technical=development= in=the=last= few=years=coupled=with=the=decrease=in=the=cost=of=scanning=equipmentI=as=well=as=the=spreading=use=of=hardware=with=high=computational=and=graphic=capabilityI=have=made=this=technique=accessible=to= a= much= larger= audienceK= fn= additionI= as= the= technique= is= contactlessI= rapid= and= able= to= provide=quantitative= informationI= it= may= be= used= for= monitoring= the= superficial= environmental= decay= in=outdoors=masonryK==OK ^fM lc qeb tloh =qhe= research= work= herein= presented= was= aimed= at= finding= proper= methodologies= for= following= the=evolution=of=degradation=processes=connected=to=moisture=and=salt=movements=in=masonry=since=their=initial=stageK=tith= this=purposeI=a= large=brick=masonry=wallI=with=one=main=side=unplastered=and=one=plasteredI= subjected= to= natural= weathering= and= brine= damp= rise= was= studied= by= means= of= an= image=based=diagnostic=techniqueW=highJresolution=laser=scanning=by=triangulation=techniqueK=fn=this=paper=the=methodology=followed=for=the=diagnosis=was=presented=together=with=some=preliminary=results=of=this=onJgoing= experimental= campaign= in= order= to= evaluate= the= reliability= of= the= technique= in= monitoring=quantitatively=the=superficial=decay=evolution=in=masonry=surfacesK==PK bumbofMbkq^i tloh

PKNK aescription of the specimen A=OJheader=masonry=wall=Especimen=mkaAF=of=nominal=dimensions=NPM=×=OR=×=NPM=cmP=Eb=×=s=×=hFI=made=of=solid=brick=units=and=natural=hydraulic= lime=mortar= jointsI=N=cm=thickI=was=consideredK=qhe=specimen= presents= one= main= face=unplastered= Efront= sideF= and= one=plastered= Erear= sideFK= qhe=plaster=layerI= N= cm= thickI= was= made=by=using= the=same= mortar= mix= of= the= vertical= and= horizontal= masonry=joints= EcigK= NFK= fn= additionI= in= the= front= sideI= some= inclusions= of= different= stones= Elimestone= and=sandstoneF=have=been=inserted=at=different=heights=in=the=wallK==

=aF====== =bF====== =cF=

cigK N=jasonry=wall=mkaA=with=basins=for=brineI=at=the=baseW=aF=front=sideI=bF=rightJhand=sideI==cF=rear=sideI=plastered=EP=jay=OMNNF=

=

OOVM=

qhe=wall=was=exposed=to=natural=weathering=Ein=the=microclimate=of=BolognaI=korthern=ftalyF=over=O=summers;=furtherI=before=the=start=of=the=second=ageing=seasonI=moisture=and=salt=capillary=rise=from=the=wall=base=was=simulated=by=lowJconcentrated=sodium=chloride=solution=EMKNB=JwtFK=qhis=natural=ageing=process= provokes= material= damage= by= favouring= solution= evaporation= and= salt= crystallization= on= the=masonry=surface=or=beneath=itK==PKOK Pa laser scanner survey fn=this=experimental=workI=a=triangulating=desktop=laser=scanner=has=been=usedI=which=is=proven=to=be=a=reliable= technology= for= nonJcontact= surface= measurementsK= qhe= technique= is= called= triangulation=because=the=laser=spotI=the=camera=and=the=laser=emitter=form=a=triangleI=and=exploiting=the=principle=of=the=topographic=forward=intersection=it=is=possible=to=determine=the=position=of=a=point=in=the=Pa=space=defined=by=the=instrumental=reference=system=EcigK=OFK=qhe=distance=between=the=laser=emitter=and=the=camera=sensor=Erepresenting=one=side=of=the=triangleF=is=known=by=the=constructor=specificationI=and=it=is= called= ±baseline”= EbFK= qhe= outJcoming= angle= EαF= of= the= laser= beam= is= also= known= by= a= prior=calibration=of=the=rotating=mirrorK=qhen=the=laser=beam=undergoes=a=reflection=on=the=targeted=surfaceI=and=its=footprint=on=the=receiving=sensor=Eusually=a=CCa=or=CjlpFI=makes=it=possible=to=calculate=the=angle=EβFK=qhese=three=informations=EαI=βI=bF=combined=with=the=trigonometric=formulas=ENFI=EOFI=fully=determine=the=coordinates=of=the=points=cloud=in=which=the=surface=can=be=discretizedK=collowing= a= process= of= triangulationI= the= points= cloud= can= be= converted= into= a= mesh= of= trianglesI=which= constitute= the=Pa= surface=of= the=objectK= ff= the=device= is= able= to= capture=also= the= color=odB=informationI= it= is= possible= to= texturize= the= surfaceK= lne= acquisition= is= generally= not= sufficient= to=recover=the=entire=surface=for=objects=greater=than=the=instrument’s=field=of=viewK=cor=this=reasonI=in=order=to=describe=the=entire=surface=in=the=best=wayI=additional=scan=positions=from=different=points=of=view=are=adoptedK==

= =cigK O iayout=of=a=triangulation=laser=scanner

=

cm

cm yx == gb tan;tan = ENF==

= =

bagb

ga

ab tantan

;

tantan

tantan

;

tantanN +

=+

=+

=bzbybx AAA =

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PKPK qest equipments qhe=laser=scanner=used=in=this=work=is=produced=by=kextbngine=fncK=and=is=based=on=jultiJstripe=iaser=qriangulation= EjiqF= technologyK= qhe= laser= scanner= acquires= the= data= in= two= different= modes=corresponding= to= two= different= baselinesW= jacro= mode= and= tide= modeK= pome= constraints= on= the=distance=between=the=object=and=the=scanner=are=given=for=each=mode=Eqable=NFK==

=

OOVN=

qable N=kextbngine=laser=scanner=specifications==

aimensions OO4=×=VN=×=OTT=mm=

Macro Mode tide Mode

cield of siew NPxNM=cm= PRxOR=cm=

torking distance NU=cm= 4M=cm=

^ccuracy –NOT=µm= –PUN=µm=

oesolution OMM=amf= TR=amf=

qexture density 4MM=amf= NRM=amf=

mointsLsec RMMMM= RMMMM=

=qhe=choice=of=the=scan=mode=depends=on=the=object’s=size=and=the=desired=output=accuracyK=qhe=scanner=mounts =a =couple =of =twin =arrays =of =Class =four =Nj =NMJmt =solidJstate =lasers =with =custom =optics =at =a=SRMJnm=wavelengthK=qhe=scanner=also=features=twin=P=jm=Cjlp=odB=image=sensorsI=and=builtJin=white=light= texture= illuminators=xTI=Uz=qhis= technique=was=chosen=because=it= is=contactlessI= rapid=and=capable= of= providing= quantitative= informationI= thus= it= could= be= helpful= in= order= to= monitor= the=degradation=processes=caused=by=moisture=and=salt=movements=since=the=beginningK==QK a^q^ ^Cnrfpfqflk =qhe= evolution= of= the=superficial= decay= caused=by=aggressive= environment= on=both= main= surfaces= of=wall=mkaA=was=monitored=by=means=of=the=above=described=laser=scanner=instrumentK==qhe=first=acquisition=campaign=was=carried=out=at=the=end=of=the=Nst=weathering=season=Elctober=OMNMF=and=the=Ond=campaign=was=repeated=after=one=year=Ekovember=OMNNF=at=the=end=of=the=Ond=ageing=seasonK==aue=to=the=small=field=of=view=of=the= instrument=usedI=a=single=scan=acquisition=was=not=sufficient=to=capture=the=entire=surfaceI=although=considering=the=±wide=mode=configuration”=EOR=×=PR=cmF=which=is=the=more=suitable=field=of=view=in=this=caseI=and=a=number=of=scanJpositions=was=necessary=for=covering=one=stripe=of=the=wall=surfaceK=qhusI=in=both=measurement=campaignsI=multiple=scans=have=been=recordedI=overlapping=a=certain=area=between=two=contiguous=scansI=and=then=combining=them=togetherK==aespite=thisI=due=to=the=large=dimensions=of=the=wall=compared=with=the=instrument=field=of=viewI=only=two=vertical=sections=of=the=specimen=have=been=scanned=Eone=on=the=front=side=and=one=on=the=rear=side=of=the=wallFK=qhis=choice=was=made=in=order=neither=to=not=dilate=excessively=the=data=acquisition=time=nor=the=subsequent=data=analysis=timeK=fn=detailI=on=the=front=side=of=the=wallI=the=vertical=section=AJA=was =surveyed =by =S =scanJpositions =while =on =the =rearI =plastered =sideI =the =central =section =EBJBF =was =considered=by=means=of=U=scanJpositions=EcigK=PFK==

=

cigK P tall=mkaAW=monitored=surfaces=in=the=frontJside=EleftF=and=back=plastered=side=ErightF

=

OOVO=

About=one=hour=was=required=to=scan=each=testing=positionK=kote=that=every=scanned=area=was=recorded=with=its=own=particular=reference=system=as=it=was=not=possible=to=establish=and=maintain=in=time=a=rigid=reference=system=on=the=object =framework=due=to=logistical =constraints =of =the=laboratory=setup=EiKeK =it =was =not =feasible =to =cover =the =wall =surfaces =or =a =portion =of =them =for =a =long =periodFK =All =the =measurements=have=been=performed=keeping=the=laser=scanner=perpendicular= to=the=wall=surface=to=be=monitoredI= about= 4M= cm= away= from= it= and= a= tripod= was= used= to= vary= the= relative= height= of= the=instrumentK==fn=this=phase=of=the=workI=another=problem=encountered=was=the=position=of=the=brick=wall=because=of=its= outdoors= storage= and= of= no= protection= against= the= sunK= Critical= environmental= illuminationI= eKgK=excessive=brightness=may=badly=affect=the=data=acquisition=as=the=used=laser=scanner=is=very=sensitive=to=this=parameterK=qhis=results=in=poor=odB=coloursI=and=in=poor=separation=between=the=laser=line=and=the=background= colour= of= the= surfaceI= hence= making= detection= difficultK= qo= avoid= these= problemsI= the=survey= is= better= performed=during= the=nightI= or= after= darkening= the=work=environment= with=panels=or=curtainsK =fn =this =experimental =caseI =the =Ond= option= was= followed= and= the= masonry= wall= and= the=equipment=were=covered=with=a=large=plastic=sheet=creating=a=dark=testing=area=below=EcigK=4FK=

=

== =

cigK Q jasonry=wall=and=surrounding=testing=area=covered=with=a=plastic=sheet=EleftFI==example=of=laser=scanner=survey=ErightF==

=RK a^q^ sfpr^ifw^qflk ^ka ^k^ivpfp

RKNK sisualization of the data As= already= mentionedI= multiple= scans= have=been= collected=at= each= measurement= position= in=order= to=capture=at=least=a=section=of=the=masonry=surface;=thenI=to=visualize=and=analyze=the=whole=set=of=data=collected=in=each=positionI=the=scan=images=have=to=be=combined=togetherK=cirst=of=allI=as=each=mesh=is=oriented= with= its= own= scanner= reference= systemI= a= relative= repositioning= was= performedI= aimed= at=reconstructing=the=original=object=geometry=and=thus=at=visualizing=correctly=the=dataK==fn=the=preliminary=phase=of=this=processI=the=approximate=Pa=rototranslation=matrix=has=been=calculated=by=measuring=at= least=P= tieJpoints= in=O=contiguous=scans=which=are=manually=selectedK=qhe=procedure=has= then= continued= involving= an= algorithm= able= to= minimize= the= difference= between= two= clouds= of=pointsW=the=fterative=Closest=moint=EfCmFK=qhis=algorithm=is=conceptually=simple;=it=iteratively=estimates=the=transformation=parameters=necessary=to=minimize=the=distance=between=the=points=of=two=raw=scans=and=then= it= transforms= the=coordinates=using=such=valuesK=qhusI=a= fine=alignment=of=each=scan=can=be=obtainedK= lnce= all= the= meshes= are= aligned= in= the= same= reference= systemI= they= have= been= merged=together=in=order=to=create=an=only=surfaceK==qhis= process= has=been= followed=for= each=of= the= two=measurement= campaigns= thus=obtaining=surfaces=consisting=of=Pa=merged=models=that=can=be=compared=between=each=other=EcigK=RI=cigK=SFK==

=

OOVP=

cigK R mkaA=crontI=footprints=of=the=scanJpositions=and=Pa=merged=models=of=OMNM=EleftF=and=OMNN=EcenterFI=texturized=subJarea=ErightF

=

cigK S mkaA=BackW=footprints=of=the=scanJpositions=and=Pa=merged=models=of=OMNM=EleftF=and=OMNN=EcenterFI=texturized=subJarea=ErightF

=auring=this=±merging”=procedureI=problems=that=may=occur=in=this=kind=of=test=have=been=encounteredK=ft=is=knownI=that=with=elongated=and=plane=objects=where=the=scans=are=essentially=positioned=along=one=directionI=problems=may=arise=with=their=alignmentK=ff=the=central=scans=are=strongly=connected=to=each=otherI=the=scans=at=the=extremes=present=only=one=side=constrained=and=the=residuals=are=usually=larger=in=this=areaK=qhis=occurs=in=our=caseI=and=thusI=not=to=affect=the=data=quality=a=subJarea=has=been=chosen=for=each=monitored=positionK===RKOK aata analysis and discussion of results qhe=meshes=derived=from=the=point=clouds=measured=at=the=end=of=each=ageing=period=have=been=used=separatelyI=first=of=allI=to=perform=a=visual=inspectionK=qhis=is=possibleI=with=Pa=modelI=especially=when=a=photographic=texture=is=superimposed=to=the=meshK=fn=detailI=some=detachment=areas=and=areas=with=material=losses=have=been=identified=in=both=measuring=campaignsK=qhusI=it=was=possible=to=detect=the=appearance=of=superficial=decay=also=at=the=very=beginning=phases=of=natural=weatheringK==fn=order=to=make=considerations=over=the=variations=over=time=in=the=Pa=geometry=of=the=object=caused=by=material=spallingI=or=to=salt=crystallization=cyclesI=the=surface=±OMNM”=was=subtracted=to=the=±OMNN”=oneI=generating=a=displacement=mapK=fn=cigK=TI=the=OMNNJOMNM=difference=displacements=maps=for=both=sides=of=the=wall=are=presentedK==qhe= highest= and= lowest= values= correspond= to= a= major= change= of= the= surface= occurred= in= time= are=reported=in=cigK=TK=fn=the=front=sideI=not=plasteredI=the=greater=area=of=negative=displacements=is=visible=at=masonry=course=S=Efrom=the=baseF=in=the=natural=stone=inclusionK=qhusI=it=seems=that=this=material=was=more=sensitive=to=the=natural=environmental=ageing=than=the=bricks=or=the=mortar=layersK=

=

OOV4=

=

cigK T aisplacement=map=in=xmmzW=mkaJA=cront=and=Back==

fn=the=rear= sideI= the=greater=negative=displacements= are=concentrated=along=a= straight=horizontal= line=that=is=located=at=about=the=same=height=from=the=wall=base=that=in=the=front=sideI=which=approximately=corresponds=to=the=level=of=moisture=riseK=fn=additionI=some=sparse=pitting=phenomena=can=be=identified=in=the=entire=plastered=surfaceK===cor=a=more=thorough=study=of=the=surface=it=is=possible=to=split=the=changes=affecting=each=constituent=materialK=qhusI=in=this=case=two=classes=have=been=createdW=one=concerning=the=bricks=and=one=for=the=mortar=layersI=considering=the=stones=as=part=of=the=±brick”=classK=fn=additionI=it=has=been=created=a=third=class= concerning= the=outliersW= outliers= are=errors= that= have=been=easily=recognized=by= the=operatorK= fn=detailI= in= this= specific=case=some=displacements= were= caused=by= the=presence=of= labels= sparse=in= the=surfaceK=qhese=labels=were=present=only=in=one=of=the=two=yearsI=and=their=presenceI=when=the=surface=comparison=is=performedI=could=be=incorrectly=interpreted=as=a=material=variationK=By= examining= the= three= classesI= called= respectively= BricksI= jortar= and= lutliersI= the= percentage= of=material= that= can= be= considered= acquired= Epositive= valuesF= or= lost= Enegative= valuesF= are=represented=with=cake=diagrams=EcigK =UFK =qhe=material =belongs=to=one=class =instead=of =the=other =according=to=the=threshold=usedK=qhe=threshold=value=correspond=to=the=instrumental=accuracy=in=the=tide=mode=Eσ=Z=–=MKPUN= mmFK= qhusI= the= areas= with= displacements= contained= in= this= range= can= be= considered= without=surface=variationsK==

=

cigK U mkaJA=diagrams

=

OOVR=

qable O=Analysis=of=the=comparison=between=the=OMNN=and=OMNM=Pa=model==

mka-^ cront Class mositive w=[=HMKPUN kegative w=<=−MKPUN fn tolerance

^rea Emm^OF

Mortar NNNRKVT= OUNVKPM= =

Brick ROMKNP= NU4TKMT= =

lutliers MKMM= UTKOS= =

qot NSPSKNM= 4TRPKSP= NS4PUNKPR=

solume Emm^PF

Mortar NNPKSM= 4SPKTN= =

Brick 4NK4U= SMVK4M= =

qot NRRKMU= NMTPKNO= =

mka-^ Back mositive w=[=HMKPUN kegative w=<=−MKPUN fn tolerance

^rea Emm^OF qot PSMPKM4= ROONKNO= NVVU4UK4T=

solume Emm^PF qot UP4KSR= PNMRKOM= ==crom =these =dataI =it =is =possible =to =note =that =both =surfaces =of =the =wall =have =suffered =some =damagesI =despite=of=the=different=orientation=and=the=presence=of=plasterK=fn=both=surfacesI=the=negative=areas=are=almost =two =times =greater =than =the =positiveI =acquired =areas =Ein =percentageFK =eoweverI =the =rear =sideI =although=it=is=exposed=to=the=korthI=presents=more=changes=than=the=surface=without=plasterK==fn=the=latterI= it=seems=that=the=moisture=and=salt=movements=have=affected=greater=the=mortar=than=the=brick =surfacesK =qhe =decay =of =the =mortar =appears =almost =in =the =same =percentage =as =swelling =or =salt =crystallizations=Epositive=areasF=and=material=losses=Enegative=areasFK= fn=the=bricksI= the=negative=areas=are= also= due= to= material= losses;= insteadI= the= positive= areas= are= only= apparent= because= the= volume=increase=is=mainly=due=to=some=flakes=that=are=separating=at=this=time=point=Ematerial=lossesFK==SK ClkCirpflk =fn=an=experimental=set=up=in=BolognaI=ftalyI=a=OJheader=brick=wall=with=one=main=face=unplastered=and=one=plastered= has=been=consideredK= qhis= masonry=specimen=has=been=subjected= to=moisture=and= lowJconcentrated=sodium=chloride=solution=EMKNB=JwtF=rise=from=the=baseK=qhe= resulting= superficial= decay= has= been= monitored=by= means= of= a= Pa= toolK= fn=particularI= laser= data=acquisitions= were= performed= on= selected= area= of= the= wall= and= repeated= at= the= end= of= two= ageing=seasonsK= jultiple= scans= have= been= recorded= and= then= combined= togetherK= fn= order= to= make=considerations= among=the=variations=over= time= in= the=Pa=geometry=of= the=object= caused=by=material=spalling=that=are=coming=outI=or=to=some=salt=crystallization=cyclesI=the=surface=collected=in=±OMNM”=was=subtracted= to= the=±OMNN”= onesI= generating=a= difference= displacements= mapK= fn=additionI= the= changes=affecting= the=surfaces= have=been= split= among=the=construction=materials= Ebricks=and= mortarF=and=the=percentage=of=material= that=can=be=considered=acquired= Epositive=valuesF= or= lost= Enegative=valuesF=are=represented=with=cake=diagramsK=crom= this= preliminary= result= it= is= possible= to= conclude= that= the= proposed= procedure= was= able= to=successfully= extract= quantitative= information= about= areas= of= material= spelling= and= detachment= in=unplastered=and=plastered=masonry=even=in=the=initial=phases=of=decayK===^ChkltibadbMbkqp =qhe= authors= would= like= to= thank= the= buropean= Commission= for= founding= the= cmTJbksJOMMTJN=pjooep=–=mrojectJkumberW=ONOVPV=EwwwKsmoohsKeuF=and=the=project=officer=jK=ChapuisK===obcbobkCbp xNz Binda= iKI= Baronio= dK= ENVUTF= jechanisms= of= jasonry= aecay= aue= to= palt= CrystallizationK=

aurability of Building MaterialsI=nK4I=blsevierI=AmsterdamI=OOTJO4MK=

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xOz pcherer= dKtK= EOMM4F= ptress= from= crystallization= of= saltK= Cement and Concrete oesearchI= P4W=NSNPJNSO4K=

xPz tendler= bK= EOMMOF= iaboratory= measurement= on= saltJloaded= brick= samples= in= periodically=changing= climate= conditionsK= The study of palt aeterioration MechanismsI= bdK= qK= von=honowI=eelsinkiI=cinlandI=UNJUTK=

x4z iubelli=BK=EOMMSF=podium chloride damage to porous building materialsK=mha=qhesisK=xRz BlaisI=cK=EOMM4F=A=review=of=OM=years=of=range=sensors=developmentK=gK blectronic fmagingI=NPW=

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pensors=in=fndustryI=Cultural=eeritageI=jedicine=and=Criminal=fnvestigationK=pensorsI=VW=RSUJSMNK=xTz Bitelli=dKI=pimone=AKI=dirardi=cKI=iantieri=CK=EOMMVF=Caratterizzazione=di=superficie=e=tessitura=del=

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merformances=evaluation=of=a=low=cost=active=sensor=for=cultural=heritage=documentationI=fnW=Uth lptical PaI=wurichI=VJNO=gulyI=RVJSVK=