Recycled Tyre Rubber Modified Bitumens for road asphalt mixtures_ A literature review

Review
RecycledTyreRubberModifiedBitumensforroadasphaltmixtures:A
literaturereview
q

DavideLoPresti
⇑
NottinghamTransportationEngineeringCentre,UniversityofNottingham,Nottingham,UK

highlights
󰀂
IntroducingtheRecycledTyreRubber(RTR)materialasenvironmentalproblemaswellasengineeringresource.
󰀂
Introducingthewetprocesstechnology.
󰀂
Describingindetailstheexistingproductsassociatedtothewetprocesshighviscositytechnology.
󰀂
DescribingindetailsthewetprocessNoAgitationtechnology.
󰀂
ComparingthedescribedtechnologiesandprovidingjustificationsandsuggestionstowardawidespreaduseofRTR-MBs.

articleinfo
Articlehistory:
Received24June2013
Receivedinrevisedform3September2013
Accepted6September2013
Availableonline29September2013

Keywords:
RecycledTyreRubber
AsphaltRubber
BitumenRubber
CrumbRubber
Terminalblend

abstract
Nowadays,onlyasmallpercentageofwastetyresarebeingland-filled.TheRecycledTyreRubberisbeing
usedinnewtyres,intyre-derivedfuel,incivilengineeringapplicationsandproducts,inmouldedrubber
products,inagriculturaluses,recreationalandsportsapplicationsandinrubbermodifiedasphaltappli-
cations.Thebenefitsofusingrubbermodifiedasphaltsarebeingmorewidelyexperiencedandrecog-
nized,andtheincorporationoftyresintoasphaltislikelytoincrease.Thetechnologywithmuch
differentevidenceofsuccessdemonstratedbyroadsbuiltinthelast40yearsistherubberisedasphalt
mixtureobtainedthroughtheso-called‘‘wetprocess’’whichinvolvestheutilisationoftheRecycledTyre
RubberModifiedBitumens(RTR-MBs).Since1960s,asphaltmixturesproducedwithRTR-MBshavebeen
usedindifferentpartsoftheworldassolutionsfordifferentqualityproblemsand,despitesomedown-
sides,inthemajorityofthecasestheyhavedemonstratedtoenhanceperformanceofroad’spavement.
Thisstudyreportstheresultsofaliteraturereviewupontheexistingtechnologiesandspecifications
relatedtotheproduction,handlingandstorageofRTR-MBsandontheircurrentapplicationswithinroad
asphaltmixtures.Furthermore,consideringthatRTR-MBstechnologiesarestillstrugglingtobefully
adoptedworldwide,mainlybecauseofpoorinformation,lackoftrainingofpersonnelandstakeholders
andraresupportoflocalpolicies,thepresentworkaimstobeanup-to-datereferencetoclarifybenefits
andissuesassociatedtothisfamilyoftechnologiesandtofinallyprovidesuggestionsfortheirwide-
spreaduse.
Ó2013TheAuthors.PublishedbyElsevierLtd.Allrightsreserved.

Contents
1.Tyrerubber:environmentalproblemorengineeringresource?................................................................864
1.1.RecycledTyreRubberasengineeringmaterial........................................................................865
1.2.FromELTstoCrumbRubberModifier...............................................................................865
1.2.1.Ambientgrinding........................................................................................866
1.2.2.Cryogenicgrinding.......................................................................................866
1.2.3.Otherprocesses.........................................................................................866

0950-0618/$-seefrontmatterÓ2013TheAuthors.PublishedbyElsevierLtd.Allrightsreserved.
http://dx.doi.org/10.1016/j.conbuildmat.2013.09.007

Abbreviations:CRM,CrumbRubberModifier;ELTs,endoflifetyres;RTR-MB,RecycledTyreRubberModifiedBitumen;RTR,RecycledTyreRubber.
q
Thisisanopen-accessarticledistributedunderthetermsoftheCreativeCommonsAttribution-NonCommercial-NoDerivativeWorksLicense,whichpermitsnon-

commercialuse,distribution,andreproductioninanymedium,providedtheoriginalauthorandsourcearecredited.
⇑
Tel.:+447587140422.

E-mailaddress:davide.lopresti@nottingham.ac.uk

ConstructionandBuildingMaterials49(2013)863–881
ContentslistsavailableatScienceDirect
ConstructionandBuildingMaterials

journalhomepage:www.elsevier.com/locate/conbuildmat
1.3.HistoryofRTRinroadasphaltmixtures.............................................................................867
2.RecycledTyreRubberModifiedBitumens(RTR-MBs)........................................................................868
2.1.GeographyofRTR-MBsinroadasphaltmixtures......................................................................868
2.2.Overviewofthebitumen–RTRinteractionprocess....................................................................868
2.3.TerminologyassociatedwithRTR-MBs..............................................................................869
2.3.1.McDonaldprocess........................................................................................869
2.3.2.Continuousblending-reactionsystems.......................................................................869
2.3.3.Fieldblends.............................................................................................869
2.3.4.Terminalblends.........................................................................................870
2.3.5.Caltransterminology.....................................................................................870
3.Wetprocess-highviscosity.............................................................................................870
3.1.Asphalt-Rubberbinder(USA)......................................................................................871
3.1.1.CRMrequirements.......................................................................................871
3.1.2.Basebinderrequirements.................................................................................871
3.1.3.Asphalt-Rubberplantproduction...........................................................................871
3.1.4.Asphalt-Rubberstorage...................................................................................872
3.2.BitumenRubberbinder(RSA)......................................................................................872
3.2.1.Rubberrequirements.....................................................................................872
3.2.2.Basebitumenrequirements................................................................................872
3.2.3.BitumenRubberproduction................................................................................872
3.2.4.BitumenRubberstorage...................................................................................873
3.3.CrumbRubberModifiedbinder(AUS&NZ)..........................................................................873
3.3.1.CRMrequirements.......................................................................................874
3.3.2.Basebitumenrequirements................................................................................874
3.3.3.CrumbRubberModifiedbinderproduction...................................................................874
3.3.4.CrumbRubberModifiedbinderstorage......................................................................875
3.4.Wetprocess-highviscosity:benefits,issuesandlimitation..............................................................875
3.4.1.Benefits................................................................................................875
3.4.2.Limitations.............................................................................................875
3.4.3.EnvironmentalIssues.....................................................................................877
4.Wetprocess-No-Agitation..............................................................................................877
4.1.Production.....................................................................................................878
4.2.Storagestability.................................................................................................878
4.3.Properties(LikeaPMB)...........................................................................................878
4.4.Applications....................................................................................................878
5.Discussionandconclusion..............................................................................................879
5.1.Conclusions....................................................................................................880
References..........................................................................................................880

1.Tyrerubber:environmentalproblemorengineeringresource?Theincreasingnumberofvehiclesontheroadsofindustrialisedanddevelopingnationsgeneratesmillionsofusedtyreseveryyear.About1.4billiontyresaresoldworldwideeachyearandsubse-quentlyasmanyeventuallyfallintothecategoryofendoflifetyres(ELTs)(Fig.1).Moreover,theamountofELTsinEurope,USandJa-panareabouttoincreasebecauseoftheprojectedgrowingnumberofvehiclesandincreasingtrafficworldwide.Thesetyresareamongthelargestandmostproblematicsourcesofwaste,duetothelargevolumeproducedandtheirdurability.TheUSEnvironmentalPro-tectionAgencyreportsthat290millionscraptyresweregeneratedin2003(EPA,2007).Ofthe290million,45millionofthesescraptyreswereusedtomakeautomotiveandtrucktyrere-treads.InEuropeeveryyear,355milliontyresareproducedin90plants,representingthe24%ofworldproduction[1].InadditiontheEUhasmillionsofusedtyresthathavebeenillegallydumpedorstockpiled.Theinadequatedisposaloftyresmay,insomecases,poseapotentialthreattohumanhealth(firerisk,havenforrodentsorotherpestssuchasmosquitoes)andpotentiallyincreaseenvi-ronmentalrisks.Mostcountries,inEuropeandworldwide,havere-liedonlandfillingtodisposeofusedtyresbutthelimitedspaceandtheirpotentialforreusehasledtomanycountriesimposingabanonthispractice.Thecurrentestimateforthesehistoricstock-pilesthroughouttheEUstandsat5.5milliontonnes(1.73timesthe2009annualusedtyresarising)andtheestimatedannualcostforthemanagementofELTsisestimatedat€600million[2].With
landfillsminimisingtheiracceptanceofwholetyresandthehealth
andenvironmentalrisksofstockpilingtyres,manynewmarkets
havebeencreatedforscraptyres.
Inordertofacethisproblem,inEuropein1989,ausedtyres
groupcomposedofexpertsfromthemaintyremanufacturers

Fig.1.EvolutionofELTsrecoveryratesinmajortyremarkets,adaptedfrom[2].

864D.LoPresti/ConstructionandBuildingMaterials49(2013)863–881