Svenska erfarenheter av rivning samt återvinning av vägmaterial i nya vägar www.vti.se/publikationer

Svenska erfarenheter av rivning samt återvinning av vägmaterial i nya vägar www.vti.se/publikationer
VTI notat 14-2011
Utgivningsår 2011
www.vti.se/publikationer
Svenska erfarenheter av rivning samt
återvinning av vägmaterial i nya vägar
Fredrik Hellman
Robert Karlsson
Maria Arm
Ebba Wadstein
Leif Viman
Ola Wiik
Helen Åhnberg
Gunilla Franzén
Förord
VTI och SGI deltar i EU-projektet Direct-Mat ”Dismantling and Recycling Techniques
for road Materials – Sharing knowledge and practices”. En del av projektet har varit att
sammanställa svensk kunskap avseende olika återvinningstekniker för vägmaterial.
Denna rapport består av en sammanslagning av de svenska bidragen till den gemensamma europeiska rapporten. Rapporten inleds med en kort svensk inledning som ger
en översikt över projektet, följt av de svenska bidragen avseende obundet material,
hydrauliskt bundet, asfalt och övriga material. Dessa bidrag har inkluderats i original
version, det vill säga på engelska.
I den svenska projektgruppen ingår följande personer:
Maria Arm, Ola Wiik, Ebba Wadstein, Helen Åhnberg, samtliga SGI.
Robert Karlsson, Leif Viman, Fredrik Hellman, Håkan Arvidsson och Gunilla Franzén,
samtliga VTI.
Linköping maj 2011
Gunilla Franzén
VTI notat 14-2011
Dnr: 2008/0102
Kvalitetsgranskning
Extern peer review har genomförts 15 april 2011 av två personer, Krister Ydrevik,
Trafikverket, och Henrik Bjurström, ÅF, i referensgruppen för Direct-Mat. Fredrik
Hellman har genomfört justeringar av slutligt rapportmanus. Forskningschefen Kent
Gustafson, VTI, har därefter granskat och godkänt publikationen för publicering 6 maj
2011.
Quality review
External peer review was performed on 15 April 2011 by Krister Ydrevik, the Swedish
Transport Administration, and Henrik Bjurström, ÅF, of Direct-Mat´s reference group.
Fredrik Hellman has made alterations to the final manuscript of the report. The research
director Kent Gustafson, VTI, examined and approved the report for publication on
6 May 2011.
VTI notat 14-2011
Innehållsförteckning
Sammanfattning ................................................................................................. 5
Summary ............................................................................................................ 7
1 1.1 1.2 1.3 1.4 Inledning .................................................................................................. 9 Obundet material ................................................................................... 10 Hydrauliskt bundet material ................................................................... 10 Asfalt ...................................................................................................... 10 Övriga material ...................................................................................... 11 2 2.1 2.2 2.3 2.4 General tendencies and political developments in Sweden
concerning environmental-friendly technology ....................................... 13 Environmental regulations ..................................................................... 13 Policies and environmental objectives ................................................... 14 Ordinance of Waste, Waste Tax and Ban on landfill of certain wastes .. 14 Tax on gravel from natural deposits ....................................................... 15 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 Unbound material .................................................................................. 16 Introduction ............................................................................................ 16 Dismantling Techniques......................................................................... 16 Recycling of road materials in new unbound layers ............................... 18 International literature review results ..................................................... 25 Conclusions ........................................................................................... 25 Definition of reviewed documents .......................................................... 26 References ............................................................................................ 26 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Hydraulically bound road materials ........................................................ 29 Introduction ............................................................................................ 29 Dismantling Techniques......................................................................... 29 Recycling of road materials in new hydraulically bound layers .............. 30 International literature review results ..................................................... 32 Conclusions ........................................................................................... 32 Definition of reviewed documents .......................................................... 32 References ............................................................................................ 32 5 5.1 5.2 5.3 5.4 5.5 Asphalt ................................................................................................... 34 Introduction ............................................................................................ 34 Dismantling Techniques......................................................................... 34 Recycling of road materials in plant mixed asphalt ................................ 35 In-Situ Recycling .................................................................................... 41 References ............................................................................................ 44 6 6.1 6.2 6.3 6.4 Other material ........................................................................................ 45 Introduction ............................................................................................ 45 Handling of excavated materials ............................................................ 45 Materials that complicate the dismantling and recycling ........................ 46 Unwanted materials, hazardous waste .................................................. 46 VTI notat 14-2011
6.5 6.6 6.7 6.8 6.9 Secondary aggregates ........................................................................... 50 Vehicle tyres .......................................................................................... 56 Polluted soils and sediments ................................................................. 61 Green waste .......................................................................................... 64 References ............................................................................................ 65 VTI notat 14-2011
Svenska erfarenheter av rivning samt återvinning av vägmaterial i nya vägar
av Fredrik Hellman, Robert Karlsson, Maria Arm*), Ebba Wadstein*), Leif Viman,
Ola Wiik*), Helen Åhnberg och Gunilla Franzén
VTI
581 95 Linköping
Sammanfattning
DIRECT-MAT (Dismantling and recycling techniques for road materials – Sharing
knowledge and practices) är ett europeiskt projekt i 7:e ramprogrammet
(http://cordis.europa.eu/fp7/home_en.html projekt nr 218656). Projektet består av
20 partners uppdelade på 15 länder.
Avsikten med projektet är att ur ett europeiskt perspektiv sprida kunskap och erfarenheter om återvinning av vägmaterial. Resultaten kommer att presenteras i en webbbaserad databas där handböcker, vägledningar, nationella dokument, referenser och
litteraturstudier är enkelt åtkomliga. Även fallstudier som exemplifierar praktiskt
användande av metoderna från de deltagande länderna kommer att finnas tillgängliga.
Projektet är indelat i fyra delområden som studerar återvinning av olika typer av
vägmaterial. Dessa delar är:




obundna vägmaterial
hydrauliskt bundna vägmaterial
asfaltbaserade material
övriga material (t.ex. askor, slagg, gummidäck, förorenade sediment och
vegetation från diken).
Den här VTI-rapporten summerar de svenska erfarenheterna av rivning samt återvinning
av vägmaterial för användning i nya vägar.

SGI, Linköping
VTI notat 14-2011
5
6
VTI notat 14-2011
Swedish experience of demolition and recycling of road materials for use in new
roads
by Fredrik Hellman, Robert Karlsson, Maria Arm*), Ebba Wadstein*), Leif Viman,
Ola Wiik*), Helen Åhnberg and Gunilla Franzén
VTI (Swedish National Road and Transport Research Institute)
SE-581 95 Linköping Sweden
Summary
DIRECT-MAT (Dismantling and Recycling Techniques for Road Materials – Sharing
knowledge and practices) is a European project in the Seventh Framework Programme
(http://cordis.europa.eu/fp7/home_en.html project no. 218 656). The project consists of
20 partners in 15 countries.
The purpose of this project is, in a European perspective, share knowledge and
experiences about recycling of road materials into new roads. The results will be
presented in a web-based database where manuals, guides, national documents,
references and literature studies are easily accessible. Case studies that exemplify the
practical use of methods from the participating countries will also be available.
The project is divided into four groups that concentrate on recycling of different types
of road materials. They are:




unbound road materials
hydraulically-bound road materials
asphalt-based materials
other materials (e.g. ash, slag, rubber tires, contaminated sediment and
vegetation from ditches).
This VTI report summarizes the Swedish experience of demolition, and recycling of
road materials for use in new roads.

SGI, Linköping
VTI notat 14-2011
7
8
VTI notat 14-2011
1
Inledning
DIRECT-MAT (Dismantling and recycling techniques for road materials – sharing
knowledge and practices) är ett europeiskt projekt i 7:e ramprogrammet (projekt nr.
218656). Projektet består av 20 partners, uppdelade på 15 länder.
Avsikten med projektet är att ur ett europeiskt perspektiv sprida kunskap och erfarenheter om återvinning av vägmaterial. Detta är viktigt för att snabbare implementera
metoder för miljömässigt och hållbart användande av naturresurser vid byggande av
vägar och infrastruktur. Tidigare har återvinning av vägmaterial studerats i olika
europiska och nationella projekt men resultaten och kunskapen har ofta stannat och
implementerats inom de enskilda länderna. Det här projektet syftar till att göra denna
information tillgänglig internationellt. Slutresultatet kommer att presenteras i en webbbaserad databas där handböcker, vägledningar, nationella dokument, referenser och
litteraturstudier är enkelt åtkomliga. Även fallstudier som exemplifierar praktiskt
användande av metoderna från de deltagande länderna kommer att finnas tillgänglig.
Projektet är indelat i fyra delområden som studerar återvinning av olika typer av vägmaterial. Dessa delar är:




obundna vägmaterial
hydrauliskt bundna vägmaterial
asfaltsbaserade material
övriga material (t.ex. askor, slagg, gummidäck, förorenade sediment och
vegetation från diken).
Den här VTI rapporten summerar resultaten från de svenska erfarenheterna av rivning
och återvinning av vägmaterial för användning i nya vägar (figur 1). Nedan ges en
summering på svenska av resultatet från de 4 olika arbetsgrupperna. Därefter följer en
mer detaljerad beskrivning på engelska av de svenska erfarenheterna.
Väg
Rivning
Återvinning
Figur 1 Vägens kretslopp.
VTI notat 14-2011
9
1.1
Obundet material
Studien beskriver rivning av obundna väglager och återvinning av vägmaterial som nya
obundna lager i vägar och vägkonstruktioner i Sverige. Den litteratur som studerats är
nationella regler (t.ex. trafikverksdokument), nationella forskningsrapporter och
praktisk erfarenhet från projekt där återvunna material använts.
Studien behandlar:




rivning av obundna lager för vägöverbyggnad
återvinning av obundna vägmaterial till nya obundna lager
återvinning av hydrauliskt bundna vägmaterial till obundna lager
återvinning av asfaltbundna vägmaterial till obundna lager.
Slutsatserna kan sammanfattas med att det är sällan en hel väg rivs. Ofta används den
gamla vägen som grund när en ny väg byggs eller en gammal renoveras. Återvinning
innebär även förstärkning och förbättring av befintliga konstruktioner. Befintligt
obundet material förstärks då genom tillsats av nya lager med krossad sten. Krossad
betong används sällan i obundna lager eftersom tillgången är liten, men i de fall det har
använts har resultaten varit bra. Asfaltgranulat används ibland som obundet bär- och
förstärkningslager med bra resultat, dock inte vid höga statiska laster. Det är uppenbart
att det finns ett stort behov av forskning i Sverige på obundna material inom områdena
stabilisering, packning, mekaniska och klimatrelaterade egenskaper (frys-tö och fukt).
Även kopplingen mellan funktion i väg och laboratoriemetoder behöver utredas mer.
1.2
Hydrauliskt bundet material
Studien beskriver rivning och återvinning av hydrauliskt bundet vägmaterial (betong)
som nya hydrauliskt bundna lager i vägar och vägkonstruktioner i Sverige. Den
litteratur som studerats är nationella regler (t.ex. trafikverksdokument), nationella
forskningsrapporter och praktisk erfarenhet från projekt där återvunna material använts.
Slutsatserna kan sammanfattas med att kunskapen om återanvändning av betongvägar i
nya hydrauliskt bundna lager är begränsad i Sverige. Anledningen är att det byggs
mycket lite nya betongvägar i Sverige. Det har därför inte funnits anledning att använda
återvunnet material i dessa. Juvenila material har använts för att säkerställa en hög och
jämn kvalité. Många äldre betongvägar från 1940-, 1950- och 1960-talet har belagts
med asfalt. I några fall har betongvägytan krossats ner av en giljotin och sedan använts
som bärlager för den nya asfaltsytan. Betongen har krossats för att undvika att skarvarna
mellan betongelementen inte ska generera sprickor i den nya asfaltsytan vilket annars
ofta blir ett problem. Resultaten från dessa vägar är generellt goda.
1.3
Asfalt
Studien beskriver rivning och återvinning av bitumenbundet vägmaterial (asfalt) i
Sverige. Den litteratur som studerats är nationella regler (t.ex. trafikverksdokument),
nationella forskningsrapporter och praktisk erfarenhet från projekt där återvunna
material använts.
Asfaltslager kan återvinnas i ett asfaltverk alternativt återvinning på plats. Lagren fräses
eller grävs upp. Svensk asfalt är ofta lämplig att återvinna då användning av tillsats-
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VTI notat 14-2011
medel som försvårar återvinningen är begränsad. Ofta krossas och siktas asfalten för att
säkerställa kvalitén.
Om återvinning i asfaltverk ska göras används asfaltgranulat med tillsats av nytt bindemedel. Vilken typ som används är beroende av vilken återvinningsmetod som används.
Tre olika återvinningsmetoder i asfaltverk är:



varm återvinning
halvvarm återvinning
kall återvinning.
Forskning visar att låg andel (20–30 %) återvunnen asfalt granulat inte påverkar asfaltegenskaperna i någon större omfattning. En liten förstyvning kan iakttas och hållbarheten förbättras. Vid högre inblandning (30–50 %) finns risk att de mekaniska egenskaperna påverkas negativt. Egenskaperna hos det återvunna materialet är en viktig
faktor. Är materialet åldrat eller uppvisar tendenser till dålig beständighet eller bristande
funktionell prestanda kan detta inverka menligt. Är det återvunna materialet inte åldrat
och av god kvalité är det möjligt att öka inblandningen återvunnet material. Vid för stor
inblandning ökar risken för sprickbildning då beläggningen blir för styv.
Flera tekniker för återvinning på plats finns (se 4.4.1). Trafikvolymen är en viktig faktor
att ta hänsyn vid val av teknik. Även avståndet till närmaste asfaltverk är en viktig
faktor. Tabell 5 (4.4.3) ger en sammanfattning av val av återvinningsmetod.
1.4
Övriga material
Studien beskriver erfarenheter av rivning och återvinning av material som inte så ofta
används i vägkonstruktioner i Sverige. Den litteratur som studerats är nationella regler
(t.ex. trafikverksdokument), nationella forskningsrapporter och praktisk erfarenhet från
projekt där återvunna material använts.
Materialen i denna grupp delas in i:
 material som försvårar återvinning (vägmarkeringar)
 farliga och oönskade material (tjärasfalt, asbest)
 sekundära ballastmaterial (slagg, askor)
 gummidäck
 förorenade jordar och sediment (dikesmassor, grus)
 vegetationsavfall (dikesklipp).
De svenska erfarenheterna rör främst återvinning av asfalt som innehåller tjära, användning av askor från förbränningsanläggningar och metallurgiskt avfall som använts i
vägkonstruktioner. Generellt är avfallsprodukter som konstruktionsmaterial i vägkonstruktioner relativt ovanliga i Sverige. Undantaget är metallurgiskt avfall från
metall- och gruvindustrin som är vanligt förekommande i kommunala vägar i närheten
av produktionsanläggningarna.
Material som försvårar återvinning är material som vägmarkeringsfärg, stålarmering och
geosyntetiska material. Vid varje rivningsprojekt bör en plan för hantering av dessa
material göras upp.
VTI notat 14-2011
11
Farliga och oönskade material i vägar är oftast förknippade med tjärasfalt i Sverige. Vid
varje rivnings- och återvinningsarbete ska förekomst av tjära och eventuellt andra
farliga ämnen identifieras. Strategin är sedan att konsultera miljömyndigheter och arbeta
fram en plan för återvinning och återanvändning. Förorenade material bör inte blandas
med nya material. Normalt bör tjärasfalt återanvändas på samma plats som obundet eller
bundet material.
Under de senaste 30–35 åren har forskning undersökt tekniska och miljömässiga egenskaper vid användning av sekundära ballastmaterial som stålslagg, bottenaskor från
avfallsförbränning (även kallade slagg) och flygaskor i vägkonstruktioner. De tekniska
erfarenheterna är ofta positiva. De miljömässiga egenskaperna ska kontrolleras i varje
enskilt fall då dessa material har mycket olika egenskaper beroende på ursprung.
Årligen genereras ca 70 000 ton utslitna gummidäck i Sverige. Hälften används i
förbränningsanläggningar och den andra hälften går till olika former av materialåtervinning. Nerklippta gummidäck (gummichip) används som lättviktsfyllning i ljuddämpningsbarriärer, frostisoleringslager, dränerade lager, elastiska lager på rid- och travbanor. Miljömässigt är det främst lakning av metaller som järn och zink som man måste
ta hänsyn till. I Sverige har det även byggts några teststräckor där återvunnet gummi
använts för att modifiera bitumen i asfaltsbeläggningar. Asfalten får då egenskaper som
förbättrad livslängd, ljuddämpande och minskad sprickbildning.
I Sverige gäller generellt att jord och material från rivningsarbeten ska återanvändas i
närheten. Jord från högtrafikerade vägar (>10 000 ÅDT) ska provtas och analyseras
innan återanvändning i vägområdet. Grus från halkbekämpning sopas upp efter vintern
och återanvänds.
Vegetationsavfall och gräsklipp från rensning av diken och vägrenar samlas sällan upp
utan lämnas kvar på plats.
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VTI notat 14-2011
2
General tendencies and political developments in Sweden
concerning environmental-friendly technology
Every year, about 95 million tonnes of aggregate material are used in Sweden. The road
construction industry is responsible for about half of this. Natural gravel and rock
material of good quality is in nature easily accessible in Sweden and therefore there is a
long tradition of road construction with unbound material, especially natural gravel.
Besides, unbound layers are less sensitive to settlements and frost heave than bound
layers and are therefore used to neutralize frost heave in pavement design.
However, as in other sectors, sustainable management of resources has commenced in
Swedish road construction. This has resulted in the introduction of alternative aggregate
materials, such as recycled aggregates or industrial residues of different kinds. The
background to this is a number of political objectives and control instruments together
with administrative and technical measures. The overall idea is that it should be a matter
of course to use alternatives when possible and thus decrease landfill and reduce
extraction from gravel pits and rock quarries. In this way, the use of alternative
materials prolongs the life of existing landfills and reduces the need for new pits and
quarries.
2.1
Environmental regulations
The Swedish Environmental Code contains 33 chapters comprising almost 500 sections.
More detailed provisions are laid down in ordinances made by the Government. The
fundamental backbone of the environmental code are the eight general rules of
consideration which concerns any activity or measure that may have environmentally
impact: The reverse burden of proof principle; The knowledge requirement; The
precautionary principle; The polluter pays principle; The BAT principle; The
appropriate location principle; The resource management and ecocycle principle and
The product choice principle.
Any recycling that is regarded as a waste handling activity requires either notification to
local authorities or licensing by court or county authority. This is also relevant in the
production of new road materials (e.g. asphalt plants, gravel pits or rock quarries).
Reuse of waste in constructions requires notification in case of a minor risk of pollution
of land or water and licensing in the case of more than a minor risk. The administrative
burden of notification and licensing often counteracts the recycling of road materials
classified as waste. Consequently, criteria for “minor risk” and “end of waste” have
been discussed extensively.
The Swedish EPA has developed “end of waste” guidelines with values on content and
leaching for reuse of waste in constructions (criteria for “ less than low risk”)
(DRF2.72). The guideline values are very strict (90% of natural background values for
some substances) and when the draft was circulated for consideration, it was overall
favourably received by environmental authorities but negatively received by research
organisations and the industry e.g. the Swedish Road Administration (SRA). The SRA
has published its own guidelines for promoting the recycling of road materials like
asphalt and excavated materials.
VTI notat 14-2011
13
2.2
Policies and environmental objectives
Sweden has set goals for the future state of its environment – Swedish Environmental
Objectives (DRF2.71). The Swedish Parliament (Riksdag) has adopted 16 environmental quality objectives, describing the state of the Swedish environment that would
be necessary to achieve sustainable development within our generation. For guidance,
interim targets for each objective have been adopted, indicating the directions and
timescale of the actions to be taken (Figure 2). Implementation of the objectives is
reviewed every year and new and revised targets and measures are evaluated every
fourth year.
Figure 2 Implementation, monitoring, evaluation and decision procedure of the
environmental objective of Swedish parlament.
Three action strategies have been drawn up to cover the activities in society that give
rise to the majority of today’s environmental problems:



more Efficient Energy Use and Transport
non-Toxic, Resource-Saving Environmental Life Cycles
management of Land, Water and the Built Environment.
Within the transport sector the SRA has been given a special responsibility for five of
the Environmental objectives: Reduced Climate impact; Clean Air (nitrogen dioxide
and particles); Good-Quality Groundwater (good-quality drinking water); Good Built
Environment (noise) and A Rich Diversity of Plant and Animal Life. Its environmental
policy includes promoting the use of environmentally-friendly materials and methods in
road construction and maintenance.
2.3
Ordinance of Waste, Waste Tax and Ban on landfill of certain
wastes
The European waste frame directive thematic strategy on the prevention and recycling
of waste is implemented in the Swedish Ordinance of Waste. Political control
instruments contributing to this trend are the Waste Tax and the Ban on landfill using
sorted combustible waste. The tax of waste deposited on landfill sites was introduced in
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VTI notat 14-2011
the year 2000. Since then it has gradually been increased, to ca € 46 per tonne as from
January 2006. For deposited material that is reused in some way, in road construction
for example, the waste tax is repaid. Some waste categories are exempted, such as waste
at landfill sites for excavated inert waste, mining waste, steel slag and blast furnace slag.
On the other hand, incinerator ash, reclaimed asphalt as well as construction and
demolition waste are affected by the tax.
Furthermore, one of the environmental objectives’ interim targets reads: “The total
quantity of waste generated will not increase and maximum use will be made of its
resource potential while minimizing health and environmental effects and associated
risk…”. This target is judged to be achievable if further vigorous measures are taken. So
far, the disposal of industrial and construction waste has decreased substantially,
partially due to the Waste Tax and the Ban on landfill using sorted combustible waste.
2.4
Tax on gravel from natural deposits
Swedish deposits of natural gravel that are of great value for the drinking water supply
and the natural and cultural landscape will be conserved. In 1996 a tax on natural gravel
was introduced. Since 2006 the tax is ca € 1.4 per tonne of gravel extracted. It is the
gravel producer that pays the tax. Over the years, natural gravel has more and more
been replaced by crushed rock in aggregate production. The reason is mainly increased
requirements on road aggregates and restrictions in new licenses for gravel pits. Further
reduction of the extraction of natural gravel is required and one of the environmental
objectives’ interim targets states “By 2010 the extraction of natural gravel in the country
will not exceed 12 million tonnes per year”. However, in 2007 the corresponding figure
was 20 million tonnes (SGU, 2008) and the 2010 target is still not reached.
VTI notat 14-2011
15
3
Unbound material
3.1
Introduction
This report describes Swedish experiences regarding dismantling of unbound road
materials and recycling of different road materials into new unbound road layers. The
description is based on relevant Swedish literature.
3.2
Dismantling Techniques
Swedish roads are not often demolished in the meaning that unbound layers are
excavated. Usually old roads are kept and used by the local traffic, only the maintenance
responsibility is transferred to another organisation.
3.2.1
National Regulations
Requirements for road constructions and dismantling are described in SRA (DRF2.77).
There are no specific requirements for dismantling unbound road layers except that
waste materials harmful to the environment shall be collected environmental friendly.
However, the Swedish Road Administration and the Swedish Railway Administration
have jointly written recommendations for handling excavated materials (DRF2.75). The
report contains answers to questions like When should excavated material be regarded
as “waste”? (Figure 3), What are the regulations for handling material classified as
waste? And if not classified as waste? It is noted that the handling itself plays a crucial
part in the classification process.
Excavated
material
Fulfils quality
demands for the use
and high probability that
the material will be used
Does not fulfil quality
demands for the use
Not high probability that
the material will be used
Waste
Raw material/
product
Figure 3 Administrative handling of excavated materials from Swedish roads. After
(DRF2.75).
3.2.2
Research results
No research reports dealing with dismantling of unbound layers have been found, but it
can be previewed that research is needed. It is for instance difficult, but important, to
properly assess the materials in an old road in advance to enable suitable recycling
actions. There is therefore a need for classification system and better methods for not
harmful and harmful testing.
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VTI notat 14-2011
3.2.3
Practical experiences
Techniques for dismantling unbound layers are partly described in (DRF2.74) published
by Swedish Road Administration. Normally, milling or excavation is performed layer
by layer, in order to separate different kinds of material.
The material can either be used directly on site or be temporary stored waiting for a
suitable application. It is important to keep in mind that the dismantling and later
processes can affect the grain shape and grain size distribution of the material and
influence the mechanical properties of the material.
Good knowledge of the pavement structure is a prerequisite for successful recycling. It
is necessary with accurate investigations in advance since detailed documentation is
rare, especially for old roads not built according to any standard.
3.2.3.1 Investigation methods
Measuring with falling weight deflectometer, FWD, is routine in Sweden for nondestructive testing, give information about the bearing capacity and stability. In addition
to FWD, and maybe complementary georadar measurement (mostly for asphalt
thickness), test pits and sampling is needed (Figure 4). The Swedish equipment
“Underlättaren” (Facilitator in English) is developed for sampling unbound road layers
in asphalt paved roads (Figure 5). The vehicle has remote-controlled equipment for
drilling, digging, filling and compaction. Normally, the sampling width is 0.35 m and
the maximum depth is 1.2 m. Alternative equipment is a cylinder that is pressed through
the unbound layers by means of hydraulic power (for example by an excavator).
Afterwards, the cylinder can be split up lengthwise and thus show the whole road
structure (Figure 5).
FWD
Georadar
Figure 4 Equipment for not harmful testing (SRA, 2008).
VTI notat 14-2011
17
“Underlättaren” (“Facilitator”)
Tryckrör (cylinder that is
pressed through the road
structure)
Figure 5 Equipment for sampling in unbound layers (SRA,2008).
3.3
Recycling of road materials in new unbound layers
When recycling road material in new unbound layers it is possible to use both unbound
rock material and asphalt layer. It is possible to recycle both so called virgin material
(rock material and bitumen separated) and asphalt. The dismantled asphalt is called
asphalt granulate. Dismantled concrete roads can also be recycled as new unbound road
layers.
Both temporary and stationary recycling plants are used in Sweden, in both cases
temporary storage is necessary. Stationary plants also handle demolishing waste from
other construction activities.
3.3.1
Recycled unbound materials in new unbound layers
Unbound material from an old road can be recycled in a new road if its virgin properties
have been measured. This is normally done according to specifications and methods
published by the Swedish Road Administration. Sometimes, the excavated road material
can be used directly on site as road base in cycle paths and footpaths along the new
road.
3.3.1.1 National Regulations
When unbound materials are recycled in new unbound layers they must fulfil the same
requirements as new unbound materials. These requirements are described in VVTBT
Unbound layers (DRF2.76) which is valid together with VV AMA Construction
(DRF2.77). The first document contains the Swedish Road Administration’s
requirements on properties of delivered unbound pavement materials as well as on test
of materials, levels and bearing capacity of final unbound road layers. The second
document is a reference document for preparation of tendering invitations for civil
engineering works.
18
VTI notat 14-2011
Property requirements on unbound materials delivered for road construction purposes
exist on the amount of crushed and broken surfaces, the resistance to wear and
fragmentation, the quality of fines, the petrography and the content of organic material
(Table 1). These requirements should also be fulfilled in the final pavement layers.
Table 1 Requirements on unbound materials for Swedish road construction. After
(DRF2.76) and (DRF2.77).
Asphalt paved roads
Property
Standard
Crushed & broken
surfaces of
aggregates
EN 933-5
Resistance to wear
(micro-Deval)
Resistance to
fragmentation
Road base Subbase
Prepared Wearing
Road base Sub-base
subgrade course
>50%crushed >50%crushed
CNR/50
CNR/50
MDE>25
MDE 30
(MDE 1430)
MDE 30
>30
10-50
≤30%rounded ≤30%rounded
1
EN 1097-1
MDE>20
2
MDE>25
EN 1097-2
LA40
EN 933-8
>35
EN 13286-2
Yes, shall
be done
Gravel roads
1
MDE>20
3
2
MDE 30
(Los Angeles)
Quality of fines
(Sand equivalent)
Compaction
properties
Petrography
(mica content)
Organic content
3
3
(10-50)
(10-50)
1
<30%
EN 932-3
2
EN 1744-1
4
SS 027102
< 40 %
<50%
<2%org
EN 933-1
4
<2%org
Special
curve
Grading
EN 13242
in SRA
2009a
EN 13285
1. Can be used for traffic during construction
2. No traffic allowed during construction
3. Recommended values
4. On fraction >2 mm
Curve
GO 0/31,5
4
<2%org
4
<2%org
0,063 mm
Curve
<9%
GA 0/16
(UF9)
4
4
<2%org
<2%org
Curve
GC 0/31,5
Curve
GC 0/45
If ADTtotal  2,000 or if the construction site area exceeds 5,000 m2 the bearing capacity
of the final pavement layers should be tested and fulfil the requirements in Tables 2
and 3.
VTI notat 14-2011
19
Table 2 Requirements on bearing capacity of Swedish road bases or top unbound layers.
Interval for acceptance of flexible construction, static tests according to
DIN 18134. After (DRF2.76) and (DRF2.77).
Number of
tested points
Reconstruction for
bearing capacity improvements
New construction
n=8
XEv2 ≥ 140 + 0,96·s MPa
n=5
XEv2 ≥ 140 + 0,83·s MPa
XEv2 ≥ 120 + 0,68·s MPa
In all tested points
In all tested points
If Ev2 ≤ 140 MPa; Ev2/Ev1≤2,8
If Ev2≤120: Ev2/Ev1 ≤ 2,8
If Ev2  140 MPa; Ev2/Ev1 ≤ 1+0,013·Ev2
At least 7 of 8 tested points or 4 of 5
points must be approved
If Ev2>120: Ev2/Ev1 ≤ 1+0,015⋅Ev2
Gf if xi<125 MPa
At least 4 of 5 tested points must be
approved
Gf if xi<105 MPa
Table 3 Requirements on bearing capacity of Swedish road bases or top unbound layers.
Interval for acceptance of flexible construction, surface compaction meter tests. After
(DRF2.76) and (DRF2.77).
New construction
Ev2 ≥ 125 MPa
Reconstruction for bearing capacity
improvements
Ev2 ≥ 105 MPa
Ev2/ Ev1 ≤ 1,5 + 0,019⋅ Ev2
In all tested points
Ev2/ Ev1 ≤ 1,5 + 0,0136⋅ Ev2
All test points must be approved
3.3.1.2 Research results
There are no real research reports dealing with recycling of unbound road materials in
unbound road layers, but there is a lot of experience that is referred to in section 3.1.3.
In the middle of the nineties it was stated that further research on deep stabilisation and
also on simple reproducible performance laboratory tests was needed (DRF2.67) and
this is still valid.
3.3.1.3 Practical experiences
The term recycling also includes measures for strengthening and thereby prolongation
of the design period of an existing road, for example by deep stabilisation of unbound
layers with binders or macadam. These measures are primarily used for low traffic
volume roads and at long transportation distances to the pit. They are suitable for
unbound materials that are unstable due to surplus of sand. In low traffic volume roads
also thin asphalt surface layers are mixed with the unbound base course by milling on
site.
20
VTI notat 14-2011
A recycled material can sometimes be used further down in a new pavement, but
sometimes a more high-quality material can be produced by crushing/sorting.
Where one or several materials from an old pavement are combined with new material it
is recommended to perform preparatory laboratory tests to achieve an end product that
is mechanical stabile enough.
Performance testing of the recycled material in the laboratory by means of cyclic load
triaxial tests is an alternative, but note that as in the case with FWD, only stiffness is not
enough as performance measure. This is due to the fact that materials with very
different grading and/or grain shape could show similar stiffness moduli, but their
resistance to permanent deformation can differ a lot. Furthermore, water sensitivity has
to be investigated since it is crucial for stiffness and permanent deformation behaviour
of unbound materials containing fines.
Count on deterioration
Reusing unbound road materials will always result in a loss of material due to
deterioration during handling and at the same time wear of sharp particle edges, but also
due to difficulties in excavating and separating material from different layers. This
means that new material has to be added, fines to be separated or binder to be added.
The recycled unbound material can have been mixed by penetrating fine grained
material (subgrade material) into the sub-base due to missing filter layer or by fine
grained sub-base entering into the base course. It is common with high sand content and
rounded particles in Swedish sub-bases – in old roads even in the base course. Scraping
during previous road strengthening work can have resulted in a degraded base course.
Wrong design leads to deterioration due to traffic, for example degrading of weak rock
material that produces plastic fines. Unbound materials are exposed to the largest stress
(and degrading) during construction, in connection with spreading and especially by
construction vehicles. In the final road no degrading of unbound layers occurs if the
road is properly designed.
To think of in the new road
− In addition to traffic, water has an impact on the unbound materials performance,
this means that very poor unbound materials can perform well in a dry location.
Damages arise first when water enters through a cracked asphalt surface layer.
− Rounded material is sensitive for permanent deformation, i.e. it is rutting during
loading.
− If the excavated material is weak it should be used in a well-graded form to allow
some degrading/crushing at mechanical stress in the new road.
− Drainage of the new road is always important for good performance.
Repeated recycling results in decreasing homogeneity of the material.
3.3.2
Recycled hydraulically bound materials in new unbound layers
There are very few concrete roads in Sweden. It is therefore not common that they are
dismantled. However, concrete for recycling can have other sources e.g. waste from
concrete plants and plants for pre-fabricated concrete elements and concrete from
dismantled constructions. The use of this type of concrete waste in road constructions
VTI notat 14-2011
21
has been studied for several years in Sweden and research results and practical
experiences have been implemented in national regulations and handbooks.
3.3.2.1 National Regulations
The Swedish requirements for use of crushed concrete in new unbound road layers are
published by the Swedish Road Administration in (DRF2.73). An English summary is
also available and published as a report within the European project SPENS. In the
specifications, crushed concrete is classified into quality classes depending on concrete
quality and amount of impurities and to these classes are assigned different design
moduli (Table 4). If stiffness increase properties can be proved, an even higher modulus
value may be used. The quality of the concrete should be determined either by
compressive strength or by micro-Deval. Methods to be used are EN 12390-31 and
EN 1097-12.
Table 4 Quality classes of crushed concrete for use in unbound road layers according to
Swedish specifications, (% by mass).
Design modulus
Constituent
Concrete
1
2
3
4
450 MP
450 MPa
250 MPa
150 MPa
450 MP
≥ 95
≥ 80
≥ 50
Masonry
≤5
≤ 20
≤ 50
Lightweight
≤1
≤5
≤ 50
≤ 0.5
≤2
≤ 10
Bituminous mixes
Other foreign
materials
100
Quality classes 1 and 2 meet the requirements of unbound base and sub-base of roads.
The lower quality class 3 can be used as sub-base in cycle ways and foot paths. Class 4
is usually only used in simpler tasks as filling. These quality classes are mainly based
on research described in (DRF2.80).
3.3.2.2 Research results
In the nineties, several research projects were performed in Sweden regarding the use of
crushed demolition concrete in road constructions. They included both laboratory tests
and field tests. In the laboratory, the following properties were determined: Grain size
distribution, optimal water content, maximum dry density, Los Angeles and microDeval values as well as stiffness and stability according to cyclic load triaxial tests. In
the field, strength was monitored by means of falling weight deflectometer
measurements. The results from this research are published in many reports, but
summarised and referred to in (DRF2.80) and (DRF2.66) and they have served as bases
for the present national requirements described in (DRF2.73).
1
EN 12390-3: Testing hardened concrete - Part 3: Compressive strength of test specimens.
EN 1097-1: Tests for mechanical and physical properties of aggregates - Part 1: Determination of the resistance to
wear (micro-Deval).
2
22
VTI notat 14-2011
The origin and handling of the concrete influence the mechanical properties of the
crushed material. Porous cement as well as foreign weak particles, such as lightweight
concrete and brick, but also wood, plaster and reinforcement, reduces quality. Particle
size distribution with a large maximum particle size as well as a well-graded curve is
positive, as is the case for natural aggregates. According to cyclic load triaxial tests and
FWD measurements, crushed concrete initially has the same resilient modulus as
crushed rock (granite, gneiss and limestone). The Mr is less stress-dependent than is the
case for crushed rock.
Stiffness increase in unbound layers of crushed concrete
Both laboratory and field results have shown an increase in stiffness for unbound layers
with crushed concrete, which is not present for unbound layers with natural aggregates.
This increase is considerably larger in the field tests than in the laboratory test. The
increase is greatest during the first months and then diminishes. This means that the
layer modulus two years after construction can be about twice as high as the level after
one month.
A low degree of carbonation in the original concrete yields faster carbonation and
subsequent stiffness increase in the final compacted layer of crushed concrete. A lot of
masonry and natural aggregate is limiting, since these materials are not subject to
carbonation themselves. It is favourable for the stiffness of the construction to have a
long contact period between water and concrete particles. A dense grading, rich in fines,
gives a large particle surface area and speeds up the carbonation process.
Crushed concrete has lower resistance than gravel and crushed granite when tested with
standardised mechanical laboratory methods like LA. The concrete material produces
greater proportion of fines and is subject to greater disintegration. The resistance to
mechanical impact depends on particle shape and indirectly on the way of crushing –
the flakier, the lower resistance. The resistance is also affected by the amount of foreign
material, for example a lot of masonry and lightweight concrete decreases the
resistance. High strength in the original concrete yields better resistance to wear. If the
concrete material is clean, the fines produced are not plastic as in natural aggregates, but
contribute to the stiffness increase due to carbonation as mentioned above.
3.3.2.3 Practical experiences
Recycled crushed concrete is manly used as base or sub-base in roads or parking spaces
or as fillings in other construction purposes. Test sections with unbound layers of
crushed concrete in road base and sub-base show good durability compared to reference
sections with unbound rock materials (DRF2.80); (DRF2.66). Experience from crushing
is described in (DRF2.79).
3.3.3
Recycled reclaimed asphalt in new unbound layers
The information in this section is summarized from (DRF2.68), (DRF2.69), (DRF2.70),
(DRF2.74) and (DRF2.78). Asphalt granulate that cannot be recycled in a new asphalt
layer can be recycled in an unbound road base or sub-base. It can also be used as surface
on gravel roads, as material in road shoulders, in temporary repair work and as surface
layer at construction sites.
VTI notat 14-2011
23
3.3.3.1 National Regulations
The Swedish Road Administration’s requirements on reclaimed asphalt are collected in
(DRF2.74). They are based on several years of research that is referred to here below.
3.3.3.2 Research results
Important Swedish research reports dealing with reclaimed asphalt are (DRF2.68),
(DRF2.69) and (DRF2.70).
Regardless of the dismantling method it is recommended that the asphalt material is
crushed and sorted in different size fractions before use in new unbound layers. The
quality of the asphalt granulate is improved by addition of new binder. However,
sometimes it can be favourable to use it without addition of new binder. This has to be
decided from case to case depending on how the material will be used and on the quality
of the asphalt granulate. A specific investigation should always be done. Quality
parameters, durability and material properties are still not fully understood even though
this material has been used for many years. More research is needed in this field of
application.
3.3.3.3 Practical experiences
Crushed asphalt granulate can be suitable in unbound base and sub-base layers,
especially when the granulate comprises a high portion of rock material. Practical
experience shows that this type of material can obtain a load bearing capacity that is as
good as or even better than that of crushed rock in a base or sub-base layer. Stability can
be problematic if bitumen content is too high or if the material is poorly compacted. It is
not recommended to use asphalt granulates were high static loads are expected, because
it increases the risk for deformation.
The size fraction, the grading curve and other material properties of the asphalt
granulate will affect the final quality of the construction. Another critical factor for a
good result is the construction workmanship, and particularly the compaction.
Compaction of asphalt granulate can be difficult. Best results are obtained if the
material is laid in thin layers of 8–15 cm thickness and then carefully compacted while
watering in warm weather conditions (Swedish summer). The compactor should be
heavy (15 ton). Compaction should be done at low frequencies and high amplitude to
obtain good compaction at depth. Traffic on these layers before the final asphalt layer is
laid will decrease later surface rutting. The traffic load will improve the compaction
with time and it is not uncommon that the material sticks together and creates a compact
asphalt layer on roads with high traffic intensity.
Asphalt granulates can be used as surface layer on low traffic volume gravel roads.
Granulates of sieve fraction 0–11 or 0–18 mm are used for this purpose. To obtain the
best result, the granulates are mixed with ordinary gravel for surfacing of gravel roads.
The mix is then levelled with a road grader. This procedure can be repeated when the
road surface is rutted after it has been subject to traffic for some time. Normally the
layer thickness is about 50 mm. One problem that can occur is that the asphalt
granulates lump together and create a brittle layer. This layer is sensitive to cracks and
potholes can develop. The problem can be solved by adding more gravel on the surface.
The use of asphalt granulates can reduce the amount of dust emitted from the road
surface.
24
VTI notat 14-2011
Another use of asphalt granulate is as road shoulder material. It is then crushed and
sieved to fraction 0–18 mm. Compaction can be done with the wheels of a truck.
Asphalt granulate has sticky behaviour and will therefore decrease the risk for erosion
when the ditch and road shoulders are subject to large water flows. A drawback is that
the roadside has similar colour to the road.
Asphalt granulate can also be used for temporary repair of potholes, water damages and
other damages on the asphalt surface. The advantage compared to gravel is that it sticks
better on place.
It is also possible to use asphalt granulate as a surface layer for heavy traffic at
construction sites. The advantage is that it emits little dust. It gives not a smooth surface
but can work temporary. After use the material can be removed and reused elsewhere.
3.4
International literature review results
The present report is based on relevant Swedish literature. Literature from international
conferences, seminars, meetings, results of European projects, and literature from other
countries which are not represented by WP2 members are not reviewed in this phase. A
synthesis of this important knowledge will be added in the next phase of finalizing the
Deliverable D3 Synthesis of national and international documents on existing
knowledge regarding unbound materials.
3.5
Conclusions
Swedish roads are seldom demolished, but kept and used by the local traffic when a
new road, a ring road or similar, is constructed. The term recycling also includes
measures for strengthening and thereby prolongation of the design period of an existing
road, for example by deep stabilisation of unbound layers with binders or macadam.
However, when roads are excavated there are national recommendations for handling
the excavated materials published by the Swedish Road Administration (SRA).
Recycling in Swedish road construction industry is promoted by the Waste Tax, the Tax
on natural Gravel, the ban on landfill of certain wastes and the national Environmental
Objectives with interim targets whose implementation are reviewed every year.
Recycled unbound road materials are mostly strengthened by addition of coarse crushed
material but reclaimed asphalt in granulated form is being used more and more. Crushed
concrete from roads is seldom used in new unbound layers due to the scarceness of
concrete roads. On the other hand, crushed concrete from other demolished constructions, mainly buildings, are more and more utilised.
Technical guidelines for recycling of asphalt, crushed concrete and unbound industrial
by-products into new roads have been published by the Swedish Road Administration.
These guidelines are based on several years of laboratory and field research,
documented in a row of research reports. The use of “old” unbound road materials in
new unbound layers is not regulated specifically, but the material should fulfil the same
requirements as new unbound materials.
Environmental guidelines are at the moment given on site specific bases, but general
guidelines from the Swedish Environmental Protection Agency has been circulated and
will be published next year.
VTI notat 14-2011
25
It is recommended to investigate the road carefully and then excavate layer by layer in
order to separate different kinds of material. The handling of excavated material has to
be planned, because of the classification as waste or not. Recycled unbound material is
often deteriorated during handling and construction.
Crushed concrete for use in unbound road layers is classified into quality classes (with
different design moduli) depending on concrete quality and amount of impurities. If
stiffness increase properties can be proved, an even higher modulus value may be used.
It is not recommended to use asphalt granulates were high static loads are expected,
because it increases the risk for deformation. Compaction of asphalt granulate is very
important and should be performed in thin layers at low frequencies and high amplitude
with a heavy compactor.
More research is needed on the classification of recycled unbound materials, on not
harmful and harmful testing, on deep stabilisation of unbound road layers, on simple
reproducible performance laboratory tests as well as on quality parameters, durability
and material properties of asphalt granulate.
3.6
Definition of reviewed documents
National regulations:
 standards; standardised technical & environmental terms of contract
 governmental guidelines
 governmental recommendations
Research results
 published project reports
 national and international papers
Practical experiences
 Nationally and internationally published state-of-the-art reports
 National common practice – not published, found in other papers like tender
specifications, articles in technical journals etc.
3.7
References
(DRF2.66)
Arm M. (2007). ”Strength development in road layers of crushed concrete – Results
from field tests”. In: Jacobsen, Jahren och Kjellsen (Ed.), Int Conf on Sustainability in
the Cement and Concrete industry. Lillehammer, Norway. pp 290–298.
(DRF2.67)
Höbeda P. (1995). ”Återvinning av obundna och hydrauliskt bundna material i vägbyggnad” (“Recycling of unbound and hydraulically bound materials in road
construction”). VTI notat 19-1996. Swedish Road and Transport Research Institute,
Linköping.
26
VTI notat 14-2011
(DRF2.68)
Jacobsson T. (2002a). ”Återvinning av krossad asfalt som bär och förstärkningslager
Del 1 – Karaktärisering och egenskaper genom laboratoriestudier” (”Recycling of
crushed asphalt in base course and sub-base Part 1 – Laboratory characterisation”).
VTI notat 31-2002. Swedish Road and Transport Research Institute, Linköping.
(DRF2.69)
Jacobsson T. (2002b). ”Återvinning av krossad asfalt som bär och förstärkningslager
Del 2 – Erfarenheter genom fältstudier” (”Recycling of crushed asphalt in base course
and sub-base Part 2 – Field experiences”). VTI notat 32-2002. Swedish Road and
Transport Research Institute, Linköping.
(DRF2.70)
Jacobsson T. (2003). ”Fräst asfaltgranulat som bärlager i gångbanor” (”Milled asphalt
granulate for use as base course in footpaths”). VTI notat 20-2003. Swedish Road and
Transport Research Institute, Linköping.
(DRF2.71)
SEPA. (2009). “Miljömålsportalen” (“Environmental Objectives Portal”)
www.miljomal.nu/Environmental-Objectives-Portal. Swedish Environmental Protection
Agency, Stockholm.
(DRF2.72)
SEPA, (2010). ”Återvinning av avfall i anläggningsarbeten” (”Recycling of waste in
construction works”) Handbok 2010:1. Swedish Environmental Protection Agency,
Stockholm.
SGU. (2008). “Aggregates – Production and resources 2007”. Per. Publ. 2008:3. The
Geological Survey of Sweden, Uppsala. www.sgu.se
(DRF2.73)
SRA. (2004a). “Allmän teknisk beskrivning. Krossad betong i vägkonstruktioner”
Publ 2004:11. Swedish Road Administration, Borlänge. An English summary;
“Crushed Concrete in Road Constructions” is published as a report within the SPENS
project (Sustainable Pavements for European New member States).
http://spens.fehrl.org/
(DRF2.74)
SRA. (2004b). ”Handbok för återvinning av asfalt” (”Handbook for recycling of
asphalt”). Publ 2004:91. Swedish Road Administration, Borlänge. 188p, Download at
http://www.vv.se Chapter 12.
(DRF2.75)
SRA. (2007). ”Hantering av uppgrävda massor – administrativa krav” (“Handling of
excavated materials – administrative regulations”). Publ. 2007:99. Swedish Road
Administration, Borlänge.
SRA. (2008). “Förstärkningsprojektering” (”Pavement strengthening design”). Publ.
2008:15. Swedish Road Administration, Borlänge.
(DRF2.76)
SRA. (2009a). ”VVTBT Obundna lager 09” (“VVTBT Unbound layers 09”). Publ.
2009:117. Swedish Road administration, Borlänge.
VTI notat 14-2011
27
(DRF2.77)
SRA. (2009b). “VVAMA Anläggning 09” (“VVAMA Construction 09”). Publ
2009:111. Swedish Road Administration, Borlänge.
(DRF2.78)
SVEKOM. (2004). ”På väg igen – vägen tillbaka för återvunnen asfalt” (”On the road
again – the road back for recycled asphalt”), Svenska kommunförbundet, Stockholm.
(DRF2.79)
SYSAV. (2000). “Krossad betong, ett återvinningsprojekt” (”Crushed concrete, a
recycling project”, SYSAV, Malmö.
(DRF2.80)
Ydrevik K. (1999). ”Återvägen – Råd och vägledning för krossad betong som ballast i
gator och vägar” (”The way back – Guidelines for use of crushed concrete as aggregates
in roads and streets”). VTI-notat 67-1999. Swedish Road and Transport Research
Institute, Linköping.
28
VTI notat 14-2011
4
Hydraulically bound road materials
4.1
Introduction
This report describes Swedish experiences regarding dismantling of hydraulically bound
road layers and recycling of various road materials into new hydraulically bound layers.
Since no relevant literature has been found, the description is based on interviews.
In Sweden, few concrete roads have been built since the seventies. The total length of
all Swedish concrete roads is currently 87 km (Table 5).
Table 5 Concrete roads in Sweden, in use 2008.
Road number
Built
year
Length
(km)
Maintenance and Repair
E6 Vellinge
1972
13
Diamond grinded in 1991. New wearing course
2009 (40 mm rubber asphalt)
E4 Helsingborg
1978
7
Diamond grinded in 1992
E4, E65 Arlanda
1990
1,6
No maintenance
E6/E20 Falkenberg
(phase 1)
1993
15
No maintenance
E6/E20 Falkenberg
(phase 2)
1996
13
No maintenance
E20 Eskilstuna
1999
14
Diamond grinded in 2000
E4 Uppsala
2006
23
No maintenance
Total
87
Most of the roads constructed before 1970 have been overlaid with an asphalt surface
layer and only a few have been dismantled. Information about dismantling techniques is
therefore limited. In fact, this study has not found any research reports or regulations
dealing with dismantling and recycling of concrete roads. Some practical experience
and knowledge exists among contractors and within the Swedish Road Administration
(SRA).
4.2
Dismantling Techniques
A worn out concrete pavement can be repaired through an overlay with a new concrete
layer or, more commonly in Sweden, overlaid with asphalt. If the concrete layer is
removed it is done by crushing the concrete with a falling weight (guillotine). After
crushing it is possible to excavate the material. The crushed concrete is then transported
to a storing place for further treatment. Normally it is crushed and used as an unbound
material.
VTI notat 14-2011
29
4.2.1
National Regulations
No specific regulations for dismantling concrete roads are available in Sweden.
However, the Swedish Road Administration and the Swedish Railway Administration
have jointly written recommendations for handling excavated materials (SRA, 2007).
The recommendations are relevant also for hydraulically bound materials and contain
answers to questions like When should excavated material be regarded as “waste”?
(Figure 6) What are the regulations for handling material classified as waste? And if not
classified as waste? It is noted that the handling itself plays a crucial part in the
classification process.
Excavated
material
Fulfils quality
demands for the use
Does not fulfil quality
demands for the use
and high probability that
the material will be used
Not high probability that
the material will be used
Waste
Raw material/
product
Figure 6 Administrative handling of excavated materials. After (SRA, 2007).
4.2.2
Research results
No research in this field.
4.2.3
Practical experiences
Practical experience about dismantling techniques can to some extent be found among
contractors and within the Swedish Road Administration.
4.3
Recycling of road materials in new hydraulically bound layers
4.3.1
Recycled unbound materials in new hydraulically bound layers
Reclaimed unbound road materials have not been used as aggregate in new concrete
layers. They are usually re-used in unbound layers.
4.3.1.1 National Regulations
No regulations.
4.3.1.2 Research results
No research in this field.
4.3.1.3 Practical experiences
No information.
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VTI notat 14-2011
4.3.2
Recycled hydraulically bound materials in new hydraulically bound
layers
Reclaimed concrete is not used as aggregate in new concrete layers for roads. It is
possible to use the concrete waste from a dismantled concrete road as unbound layer in
a new road. To be able to use the material its properties needs to be measured. This is
described more in detail in the Swedish WP2 report of DIRECT-MAT. Sometimes the
concrete layer is re-used as base layer under an asphalt surface layer (see section 3.2.3).
4.3.2.1 National Regulations
No specific regulations.
4.3.2.2 Research results
No research in this field.
4.3.2.3 Practical experiences
Swedish concrete roads are usually not dismantled. Normally, when a concrete road is
worn out the top layer is covered by a flexible asphalt layer. Thus, the concrete surface
layer is reused as a new base layer. Recently it has been popular to use rubber asphalt
surface layer which is claimed to better conceal the joints in the concrete.
A number of old concrete roads built in the 1940s are still in use. They have a
reinforced concrete layer of 150 mm. About ten years after they were built, they were
overlaid with approximately 50–100 mm asphalt. During the years this action has
resulted in reflexion cracks in the asphalt surface layer due to shrinkage in the concrete.
In recent years a new maintenance technique has been tested to prevent the occurrence
of such reflexion cracks. The concrete has been crushed by the use of a special falling
weight/ guillotine at every metre of the road in connection with ordinary maintenance of
the asphalt layer. The method has worked out well giving a substantial decrease in
cracks caused by shrinkage. It has been used on the following roads in Östergötland
county: Väg 796 Beatelund–Linghem–Gistad, Väg 636 Sjögestad motel–Vikingstad,
Väg 1037 Vikingstad–Hasselbacken.
4.3.3
Recycled reclaimed asphalt in new hydraulically bound layers
Asphalt granulate is not used as aggregate in new concrete layers.
4.3.3.1 National Regulations
No specific regulation.
4.3.3.2 Research results
No research in this field.
4.3.3.3 Practical experiences
No information.
VTI notat 14-2011
31
4.4
International literature review results
This report is based on interviews. Literature from international conferences, seminars,
meetings, results of European projects, and literature from other countries which are not
represented by WP3 members are not reviewed in this phase. A synthesis of this
important knowledge will be added in the next phase.
4.5
Conclusions
Swedish information about dismantling techniques for hydraulically bound layers is
limited. No research reports or regulations dealing with dismantling and recycling of
concrete roads have been found. Some practical experience and knowledge exists
among contractors and within the Swedish Road Administration.
Only a few concrete roads have been dismantled. It has been done by crushing the
concrete with a falling weight (guillotine) and then excavating. Worn out concrete
pavements are most commonly overlaid with an asphalt surface layer, which actually
means that it is reused as a concrete base layer.
Reclaimed unbound road materials have not been used as aggregate in new concrete
layers. Reclaimed concrete has not been used as aggregate in new concrete layers for
roads. It is, however, possible to use the concrete waste as an unbound material in new
roads. Asphalt granulate is not used as aggregate in new concrete layers.
4.6
Definition of reviewed documents
National regulations:
 standards; standardised technical & environmental terms of contract
 governmental guidelines
 governmental recommendations
Research results:
 published project reports
 national and international papers
Practical experiences:
 Nationally and internationally published state-of-the-art reports
 National common practice – not published, found in other papers like tender
specifications, articles in technical journals etc.
4.7
References
Personal communication 2009 with:
– Mr Christer Hagert, Swedish Road Administration
– Mr Bengt-Åke Hultqvist, VTI
– Mr Torbjörn Jakobson, Swedish Road Administration
– Mr Krister Ydrevik, Swedish Road Administration.
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VTI notat 14-2011
SEPA. (2009) “Miljömålsportalen” (“Environmental Objectives Portal”)
www.miljomal.nu/Environmental-Objectives-Portal. Swedish Environmental Protection
Agency, Stockholm.
SGU. (2008) “Aggregates – Production and resources 2007”. Per. Publ. 2008:3. The
Geological Survey of Sweden, Uppsala. www.sgu.se
SRA. (2007) ”Hantering av uppgrävda massor – administrativa krav” (“Handling of
excavated materials – administrative regulations”). Swedish Road Administration
Publication 2007:99.
VTI notat 14-2011
33
5
Asphalt
5.1
Introduction
This report describes Swedish experiences regarding dismantling and recycling of
asphalt pavements. The description is based on relevant Swedish literature. Most of the
issues are already covered in a handbook for asphalt recycling comprising 184 pages of
the current state of the practice in Sweden (DRF4.217). Therefore chapters 2 to 4 are
mainly based on the handbook where meta-analysis is done based on a large number of
references, but in the case of other original sources, these are referenced instead.
5.2
Dismantling Techniques
5.2.1
Dismantling Techniques
Main reasons for reclamation of asphalt concrete are:
 complete removal of pavement or road works such as pipe works
 removal of asphalt layers, i.e. deep milling in wheel paths or removal of inferior
materials
 planning and levelling before new layers are placed, either to get an even
foundation for subsequent layer or to adjust levels for adjacent pavement, curbs,
manhole covers etc.
In the process of removal, either planning/milling or in the case of complete removal or
road works excavation is used. Excavated material is cleaned from non-asphalt
materials or sources of contamination in a general context. It is recommended that road
markings are removed by milling prior to removal of asphalt layers. Recycling of tar
asphalt is described separately in WP 5.
Handling of RA after the reclamation stage is considered as being important. RA should
be sorted separate groups according to different quality aspects:




surface layers from different pavement types
mixed layers
mixed pavements types
contaminated pavements.
Milled pavements can exceptionally be reused without further treatment but normally
crushing and sieving is performed to ensure quality and homogenization requirements.
It is recommended that a delicate crushing is performed and that oversized aggregates
are crushed separately (DRF4.214).
Dug up RA can be stored without restrictions of the height but after milling or crushing
the height should be kept less than 3 m. Binding can occur during summer time but is
usually constrained to the surface and easy to handle.
5.2.2
National Specifications/Regulation
Storage facilities are either temporary (on site) or permanent and are regulated by
Ordinance on waste and Tax on waste. Notification (local authorities) is obligatory and
34
VTI notat 14-2011
if the stored amount exceeds 30 000 tonnes licensing (regional authorities) required.
Storage for longer periods than 3 years are prohibited.
Guidelines on sampling has been published by SRA (DRF4.220). Pavements or stored
RA:s should be delineated in homogenous populations (areas or quantities) based on
available documentation or inspection. Sampling of dug up uncrushed material should
be avoided. Pavements are sampled by boring and stored RA by the aid of an excavator
in order to get representative and homogenous samples. Stratified random sampling is
recommended. Some guidance is given on how to calculate the required number of
samples as a function of acceptable error and estimated variance. Generic recommended
sampling frequency based on practical experience is given in the table below.
Table 6 Sampling frequency for extracting samples from pavements and RA.
Increments per
composite sample
Object
Pavements < 40 mm
Pavements ≥ 40 mm
Object
Stored RA
Stored
uncrushed
dug up RA
4
4
4
4
Number of samples
Composite samples
for small
populations
at ≤ 20,000 m2
2
3
at ≤ 3,000 tons
3
4
Composite samples
for larger
populations
at n x 20,000 m2
1+n
2+n
at n x 3,000 tons
2+n
3+n
Tabulated guideline values for identification of outliers and acceptable coefficient of
variation are given. If these values are not met further sampling and a modified
delineation of homogenous areas are recommended.
5.2.3
Research results
No research
5.2.4
Practical experiences
The dismantling and storage of uncontaminated asphalt pavement are not associated
with significant environmental or health issues except those associated with transport or
noise. Prolonged storage initiates biological processes that can be a cause of annoying
odours and smell during recycling.
Adding virgin aggregates to RA during crushing gives a material that is easier to handle.
The amount and quality of added aggregates should correspond with the requirements in
subsequent recycling.
5.3
Recycling of road materials in plant mixed asphalt
Traditionally Swedish asphalt pavements have been suitable for low temperature (warm
or cold) recycling. The use of additives like anti-stripping agents and PMB has been
limited. Swedish experiences on additives from working environment perspective have
been summarized in (DRF4.20504). Blue smoke and associated emissions to air can be
an important working environment issue. From a general point of view the use of
additives that requires hot recycling or additives that may increase the release of blue
VTI notat 14-2011
35
smoke (rubber or plastics) requires attention. The use of amine based anti-stripping
agents has been causing irritating adverse effects on sensitive individuals even well
below occupational guideline values. Modern more environmentally friendly release
agents based on vegetable oils or refined petroleum oils have been introduced as
alternatives to diesel.
5.3.1
Recycling Techniques
The reclaimed asphalt in granular form is mixed with new material. An overview of
used techniques can be seen in the table below.
Table 7 In-plant asphalt recycling methods.
Method
Application
Added binder
Normal amount of
reclaimed asphalt
Hot Recycling
For wear-, bind- and
base layer for all
traffic volumes and
road categories
Bitumen
Between 5 and 30%
depending on
reclaimed asphalt, the
process, kind of plant
and kind of layer
Warm recycling
For wear- and base
layer, mostly for lower
volumes of traffic
Soft bitumen or
foamed bitumen
More than 80%
Cold recycling
For wear- and base
layer, mostly for lower
volumes of traffic
Bitumen emulsion,
soft bitumen or
foamed bitumen
More than 80%
Guidance schemes on how to perform simplified environmental and cost assessment in
a life cycle perspective are available. Input (generic) data are not supported but should
be audited on case by case premises.
5.3.2
Recycling of reclaimed asphalt in plant mixed asphalt
 Hot recycling
Hot recycling can be carried out in two kind of plants, batch plants or continuous plants.
In continuous plant the asphalt is cold mixed and the amount of reclaimed asphalt that
can be added varies between 5 and 80 % depending of the used equipment. In batch
plants the amount of reclaimed asphalt often is lower. Batch plants with separate
warming up possibility give the highest amount of added reclaimed asphalt. The
possible amount to be added is also depended of the properties of the reclaimed asphalt
and the requirements on the end product.
In batch plants the reclaimed asphalt are added in the following different ways:
1. Directly in the mixer (the reclaimed asphalt are heated by the mix).
2. Added to dry and warm aggregate.
3. Added to the main drier barrel
4. Added to a separate drier barrel parallel to the main drier barrel.
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VTI notat 14-2011
When using method 1–3 the amount of reclaimed asphalt can be up to 20 %. Method 4
makes it possibly to increase the amount of reclaimed asphalt.
In continuous plants drying, warming and mixing are all together carried out in a
rotating barrel. The reclaimed asphalt is normally added after drying and warming of the
new aggregate. It is most common to add the reclaimed asphalt directly to the barrel but
sometimes some pre-warming takes place by using a ”double barrel”.
 Warm recycling
Typical for warm recycling is a temperature between 50°C and 120°C (most common
50–80°C) and soft bitumen as binder. The granular reclaimed asphalt is added in the
same way as new material and the warming is done mostly by steam at high pressure.
The plants are relatively easy to move which means that they can be used to low
volumes of material. Soft binders are used which makes the method suitable on roads
where flexibility properties are desirable. The method is recommended in colder climate
and low heavy traffic volumes.
 Cold recycling
Cold recycling is a rather simple procedure mostly performed in continuous plants with
capacities up to 120 metric ton/h. The plants are easy to move and are suitable for low
volumes of reclaimed asphalt. This method is used on roads with low volume of heavy
traffic (<AADT 1,500). Aggregates and/or granular reclaimed asphalt are mixed
without warming and at natural water content in continuous plants where the binder is
added. Batch plants are also used to produce cold mixes. In this case only the binder are
warmed up (emulsion, soft bitumen or foamed bitumen). There are different ways to
add binder, granular reclaimed asphalt and new aggregate with respect to where it is
inserted, temperature etc.
From an energy saving point of view, this technique is considered favourable since
transport distances are kept at a minimum and heating is unnecessary. Especially
transport distance is a problem in less populated areas of Sweden, but is also a major
cost issue.
5.3.2.1 National Specifications/Regulation
In brief, the most important requirements for cold and warm recycled mixes are grain
size distributions and the requirements presented in the table below (DRF4.216).
VTI notat 14-2011
37
Table 8 Requirements in brief for cold recycled mixes in Sweden.
Requirement
Wearing course
Base course
2,2–4,2 (3,6)
1,2–2,7 (2,4)
2,0–4,0
3,0–5,0
4–12
6–14
>5
>7
-
> 2,000
Indirect tensile strength [kPa]
> 300
–
ITSR, mean 3 samples
> 60
> 50
Added bitumen emulsion (target) [%-weight]
Water ratio in granules [%-weight]
Air voids [%-vol]
Marshall stability @ 25ºC [kN]
Stiffness modulus [MPa]
Table 9 Requirements in brief for warm recycled mixes in Sweden.
Requirement
Wearing course
Base course
1,2–3,0 (2,3)
0,6–2,4 (1,6)
2,0–4,0
3,0–5,0
Air voids [%-vol]
3–8
5–10
Marshall stability @ 25ºC [kN]
>8
> 10
–
2,000– 5,000
Indirect tensile strength [kPa]
> 500
–
ITSR, mean 3 samples
> 70
> 60
Added soft bitumen (target) [%-weight]
Water ratio in granules [%-weight]
Stiffness modulus [MPa]
Addition of reclaimed asphalt in hot mixes is limited to 20%-weight to wearing courses
and 30 %-weight to binder and base layers. For polymer modified layers, the
corresponding figures are 10 and 15%-weight, respectively. For asphalt layers with
entirely new material, the current limit for increase in softening point R&B after laying
is 6 degrees, while this limit is raised to 8 degrees for layers containing reclaimed
asphalt. All hot recycled asphalt layers must be tested with regard to abrasive resistance
according to EN 12697-16 (Prall) and fulfil the same requirements as for asphalt
without RA. Softer binders are not allowed to account for aged binders in additions of
10%-w RA in wearing courses and 20%-w RA in binder and base courses. In these
cases, the specified grade must be used, in order to avoid excessive permanent
deformations.
It should be noted that a considerable share of procurements in Sweden are based on
performance and no requirements on material composition is made in these contracts.
5.3.2.2 Research results and practical experiences
 Hot recycling
Investigations show that a moderate adding of granular reclaimed asphalt (20–30%)
does not influence the composition or properties of the mixes too much. The granular
reclaimed asphalt can have some stiffening effect and the durability seems to increase a
bit. This increase in durability can be explained by the fact that the surfaces of the
granular particles are covered with bitumen.
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VTI notat 14-2011
At higher amount of added reclaimed asphalt (30–50%) the mechanical properties can
be influenced and it can be hard to fulfil the requirements in the Swedish specifications
(DRF4.216) related to particle size distribution and increase of softening point
(DRF4.206). The degree of ageing of the binder in the reclaimed asphalt is an important
factor. Moderate ageing makes it possible to increase the amount of reclaimed asphalt.
Increased stiffness may increase the sensitivity to cracking especially at low
temperatures or if the pavement bearing capacity is low. Ways to neutralize the
stiffening effect is to use softer binder or increase the amount of new binder which
improves the fatigue properties.
 Warm recycling
Based on the results and experiences from test roads, control sections and investigations
of damaged sections the following remarks have been made with respect to type of
damage:
Type of damage
Remarks
Plastic deformation
Can be the case if the relation between binder content and binder
viscosity is too high
Traffic compaction
Some mm/layer (layer thickness 50 mm)
Rutting
Moderate in most cases
Eveness
Sometimes uneven surfaces, normal IRI-values are 1,5–2,0 mm/m.
Maybe related to stiffer mixes.
Milling prior to laying result in more even surfaces.
Bleeding
At high binder content bleedings can occur after periods of high
temperature (higher binder content sometimes needed to fulfil mix
design criteria).
Friction
Generally not affected, with some rare exceptions related to excess
of binder.
Macro texture
Generally not affected
Separation
Sometimes large, especially when the content of course aggregate
is high.
Bearing capacity
Moderately better or the same as new cold or warm mixes.
Flexibility
Depends on the binder used and the degree of ageing of the
reclaimed asphalt. Often better when soft bitumen is used.
Ravelling
Can be a problem at areas with separation
Pot hole
No problem in normal case
Surface properties
Softer when new, gets harder after initial traffic compaction
Surface appearance
Same as with new mix
Joints
Careful work is recommended (spraying)
 Cold recycling
Based on the results and experiences from test roads, control sections and investigations
of damaged sections the following remarks have been made with respect to type of
damage:
VTI notat 14-2011
39
Property
Explanation/comment
Plastic deformation
Can be the case if the binder content is too high
Traffic compaction
Some mm/layer (layer thickness 50 mm)
Rutting
Moderate in most cases
Eveness
Sometimes uneven surfaces, normal IRI-values are 1,5–2,0 mm/m
Bleeding
No problem in normal case
Friction
Mostly good
Macro texture
As for dense asphalt (ABT).
Separation
Sometimes large, especially when the content of course aggregate
is high.
Bearing capacity
The same as new cold or warm mixes or better.
Flexibility
Not as good as new cold and warm mixes
Ravelling
Can be a problem at areas with separation especially when salt is
used as de-icing agent
Pot hole
No problem in normal case
Surface properties
Soft when new, gets harder due to traffic compaction and water
evaporation,
Joints
Careful work is recommended (spraying)
For cold recycled pavements the compaction and initial maturation of the recycled layer
is important for its performance. Both steel wheel rollers and rubber tyre rollers should
be used. After compaction it is desirable that the layer can dry out for a few days in
preferably warm and dry weather in order to gain in strength. The total curing period
extends for several weeks up to half a year, if the treatment is performed during the
autumn. Traffic and temperature is of importance to the curing process.
Tar containing asphalt is often recycled cold in Sweden. From an investigation on a
layer recycled using foamed bitumen in a movable plant, it was concluded that the
recycled layer contributed significantly to the structural strength so that the thickness of
the bound base layer could be reduced (DRF4.207). Investigations have also been
performed to evaluate the use of reclaimed asphalt as base course, without added binder
and only water to make the material compactable. The results indicate that reclaimed
asphalt cure and develop structural strength and stability, sometimes reaching properties
close to ordinary new bound base course asphalt concrete (DRF4.209). Allowing traffic
on the recycled base layer for some shorter period of time is favourable since much of
the initial rutting (compaction by traffic) can be taken out when a new overlay is placed.
Research and practical tests have been performed during many years to develop rape
seed oil derivatives as alternative binders in cold recycling (DRF4.221).
40
VTI notat 14-2011
5.4
In-Situ Recycling
5.4.1
In-Situ Recycling techniques
The most frequently used techniques for in-situ recycling in Sweden are as follows:
 Repaving means warming up, scarifying and levelling of the existing asphalt
and applying new asphalt mix layer (normally 40–50 kg/m2). This new mix is
applied at the end of the repaving machine. New binder can be added to the
existing mix. The method of repaving was established during the seventies in
Sweden and is a further development of the Heating method as it is spreading
out the existing mix before overlaying.
 Hot remixing means warming up and scarifying of the existing asphalt and
mixing with new asphalt mix (about 15–30 kg/m2). After mixing the asphalt is
spread out with a screed in one layer (thickness about 30–40 mm). This is done
in an integrated process with the same machine or two machines milling in two
steps with intermediate heating. The old mix need to have a temperature that
gives correct temperature to the final mix. The remixer machines are usually
preceded by an ordinary heater. New binder and softening agent can be added.
The amount of new material typically corresponds to the ruts in the existing
pavement and allows adjacent levels to be maintained, for example adjacent
lanes, shoulders and connecting roads.
 Remixing Plus is a combination of remixing and repaving. The existing asphalt
is heated, scarified, mixed with new material and placed on the pavement again.
On this recycled layer a new asphalt layer is applied (>30 kg/m2). All is done in
an integrated process with the same machine which means that the machine
needs to have two screeds.
 Warm remixing is when the pavement is moderately heated with a heater and
then a machine is milling and adding new mix or soft bitumen before laying.
 Stabilisation is when old asphalt bound layers are milled and incorporated in
the lower base and subbase layers and new binder is added in the form of
bitumen emulsion or foamed bitumen. Down to 20 cm depth.
 Cold Remixing is when one or more asphalt layers are milled and mixed with
bitumen emulsion, aggregate or mixture before laying. Down to 10 cm depth.
 Deep milling means that asphalt layers are milled down to 0.5 meter into the
unbound layers and no extra binder is added.
5.4.2
National Specifications/Regulation
The aim is that in-situ recycled materials should fulfil the same requirements in-plant
recycled or new materials, but one exception is found in the Swedish regulations. The
tolerance for air voids is larger, between 1.5 and 6.0% (DRF4.216).
5.4.3
Research results and practical experiences
In the treatment selection phase, in-situ recycling techniques are assessed relative to
other maintenance treatments. As previously mentioned, traffic flow are one important
factor when selecting between hot, warm or cold techniques. In-situ techniques are
favoured by long distances to nearest stationary plant. In table 10 some figures are given
on when to select different in-situ techniques or to use movable asphalt plants with
regard to object size. Quality and homogeneity of existing pavement and material is also
an important factor. Type of damage on existing pavement is often used as a basis for
VTI notat 14-2011
41
judging quality of existing materials. Pavements which exhibit plastic deformations in
the asphalt layers or water sensitivity should not be subject to remixing or repaving
since the problem is likely re-occurring.
Table 10 Selection guide for in-situ techniques or movable plants with regard to object
size.
Method
Tonnes of
mix
Hot
Plant
Remix
m
2
Warm
Repave
m
2
Plant
Cold
Remix
m
2
Plant
Remix
Stabilisation
m2
< 500
< 5,000
< 5,000
< 5,000
< 5,000
500–1,500
< 15,000
< 15,000
<
15,000
< 15,000
1,500–
2,500
> 15,000
< 25,000
>
15,000
> 15,000
2,500–
5,000
Milling
> 25,000
5,000–
10,000
> 10,000
Green
= Suitable
Yellow
= To investigate
Red
= Not suitable
 Repaving (hot) has been used as wearing course treatment since the middle of
the seventies. Large areas have been executed, mostly on the national road
network and in cities. The wear and texture properties after repaving is believed
to be as good as paving with new material if the composition and execution
fulfils the requirements in the national specifications.
 Remixing (hot) has been used as wearing course treatment since the eighties.
The method has been used mostly on the national road network and in cities but
also on airfields. During the period 1993 to 1995 investigations were carried out
at nine test sites on the road network. A summary of the results are given below
(DRF4.205):
- The quality was generally good and uniform. Requires fairly good and
homogeneous existing material as well as acceptable weather conditions.
- The environment for the workers was satisfying if catalytic converter where
used.
- It was not possible to change the composition in a radical way on the existing
asphalt with additions normally in the range of 10 to 25% new material.
- The effect of added binder is not clarified. Recycled layers appear softer than
expected if complete mixing is anticipated.
- The binder gets harder, 3–5 °C in softening point (first instance of recycling).
- The milling of the warm asphalt does not lead to more crushing.
- Existing asphalt gets more homogeneous.
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VTI notat 14-2011
 Following the above study, Karlsson (DRF4.212) investigated the process of
mixing old and new binders during asphalt recycling. It was concluded that
complete mixing is possible but the degree of mixing is a result of the intensity
and time of mechanical mixing, degree of ageing (viscosity of old binder),
temperature (viscosity of old and new binders, rate of diffusion), and geometries
in mixture on scales from binder layer thickness to aggregate size allowing for
diffusion of binder components. These factors occur at a rate that may explain
occurrence of incomplete mixing during hot remixing, and certainly in colder
applications or if the difference in viscosities between old and new binders are
very large. Consequently, it was concluded that the old binder may act partly as
“Black rock” but always mix to some extent with the new binder.
From investigations on airfields during 1996 to1998 it was concluded that
remixing has a high potential to be an integrated part of the maintenance
treatments at airfields
 Remixing Plus has been used as wearing course treatment since the middle of
the nineties. The method has been used mostly on the national road network and
in cities but in last years also on airfields.
 Warm remixing has mainly been used in the northern part of Sweden where
comparably softer mixtures are used, especially on stretches with lower AADT.
These layers are relatively easy to remove and mix when heated to moderate
temperatures.
 Stabilisation was tested and evaluated by VTI on a number of stretches during
eight years of service (DRF4.208). These stretches experienced serious damages.
The roads had AADT:s of 500-2000 and the depth of treatment was 10 cm,
which meant that some unbound material was also included. A wearing course
was placed on top of the recycled layer. The treatment was considered a success
and especially useful if it is important to maintain road surface levels. The
initially developed rutting was substantial but the subsequent rut development
was relatively low. During the first year it was difficult to extract cores to test in
the laboratory due to the low added binder content, down to 1,0 %-weight. After
eight years the layer had cured and samples could be removed in one piece.
 Cold Remixing was evaluated by VTI during construction in 2000 and the
following year (DRF4.211). Nominally 11 cm was treated and a new asphalt
layer was subsequently placed on top. No damages were observed and the
structural strength measured using FWD/surface curvature was 50% larger
compared to stretches with unbound base layers.
VTI notat 14-2011
43
5.5
References
Document Review Form (DRF)
file name
title
DRF4.204
Andersson, A., Jacobson, T., Persson, B-O., 2006. Tillsatsmedel i
asfalt – påverkan på arbetsmiljö och omgivning. The Development
Fund of the Swedish Construction Industry, Sweden
DRF4.205
Isacsson, U., Ekblad, U., Johansson, S. & Krigsman, B., 1997. Varm
återanvändning av asfaltbeläggningar på vägen – Sammanfattning av
erfarenheter från försök utförda 1993-95. KTH, Stockholm, Sweden.
DRF4.206
Jacobson, T. & Waldemarsson, A., 2008. Varm återvinning i
asfaltverk – Försök med bindlager på väg 40, delen Rya-Grandalen.
VTI, Linköping, Sweden.
DRF4.207
Jacobson, T., 2007. Återvinning av tjärasfalt och krossad asfaltbeläggning vid motorvägsbygget på E4, via Markaryd. VTI, Linköping,
Sweden.
DRF4.208
Jacobson, T., 2004. Kall återvinning på plats (stabilisering) av
asfaltbeläggningar genom inblandning av bitumenemulsion. VTI,
Linköping, Sweden.
DRF4.209
Jacobson, T., 2002a. Återvinning av krossad asfalt som bär- och
förstärkningslager, Del 1 och 2. VTI, Linköping, Sweden.
DRF4.211
Jacobson, T., 2002c. Remixerstabilisering på väg 90, delen Junsele–
länsgränsen. VTI, Linköping, Sweden.
DRF4.212
Karlsson, R., 2002. Investigations of binder rejuvenation related to
asphalt recycling, Doctoral thesis. KTH, Stockholm, Sweden.
DRF4.214
Swedish Association of Local Authorities and Regions. 2004. På väg
igen – vägen tillbaka för återvunnen asfalt. Swedish Association of
Local Authorities and Regions, Sweden
DRF4.216
SRA. 2008. VVTBT Bitumenbundna lager. Swedish Road
Administration, Sweden.
DRF4.217
SRA. 2004. Handbok för återvinning av asfalt. Swedish Road
Administration, Sweden.
DRF4.218
SEPA. 2010. Återvinning av avfall i anläggningsarbeten. Swedish
Environmental Protection Agency
DRF4.219
SEPA. 2009. MILJÖMÅL. Swedish Environmental Protection
Agency
DRF4.220
SRA. 1999 Provtagning av asfaltmaterial för återvinning.” Publication
Nr 1999:162 (VVMB 620). Swedish Road Administration, Sweden
DRF4.221
Tyllgren, P., 2004. Asfalt med rapsoljederivat (rod). The
Development Fund of the Swedish Construction Industry /Skanska,
Sweden.
44
VTI notat 14-2011
6
Other material
6.1
Introduction
This report describes Swedish experiences regarding dismantling and recycling of not
commonly recycled road materials. The description is based on relevant Swedish
literature.
Swedish experience exists primarily within the management of tar contaminated asphalt
layers and the recycling of different types of incinerator ash and metallurgical slag in
unbound road layers. However, waste is still not commonly used in Swedish road
construction, except for metallurgical residues that are frequently used in municipalities
where metal producing plants are located.
6.2
Handling of excavated materials
The Swedish Road Administration and the Swedish Railway Administration have
jointly written recommendations for handling excavated materials (SRA, 2007a). The
report contains answers to questions like When should excavated material be regarded
as “waste”? (Figure 7), What are the regulations for handling material classified as
waste? And if not classified as waste? It is noted that the handling itself plays a crucial
part in the classification process.
Excavated
material
Fulfils quality
demands for the use
and high probability that
the material will be used
Does not fulfil quality
demands for the use
Not high probability that
the material will be used
Waste
Raw material/
product
Figure 7 Administrative handling of excavated materials. After (SRA, 2007a).
The main criteria for classifying are the cleanliness of materials and the probability that
they will be utilised. If not classified as waste generally no further notification or
licence is required for the use. However, the place for use can require certain
precautions, e.g. for filling in water.
If the materials are classified as waste they should not be transferred to any private
person even if there is a need for the materials. However, if the materials are clean and
will be used by the private person, the transfer can be done before the excavation (they
are then not classified as waste).
The recommendations also contain contract forms to be used when transferring
materials from the SRA to a contractor or other company.
VTI notat 14-2011
45
6.3
Materials that complicate the dismantling and recycling
Materials that can complicate the dismantling and recycling of roads are road markings,
steel reinforcement materials and geosynthetics.
Road markings have to be removed separately if the recovered asphalt material shall be
recycled in new hot mixes (SRA, 2009).
A Swedish experience when using steel net in asphalt layers to prevent crack propagation is that the vertical position of the steel net in reinforced flexible structures is
important. A position below a thin wearing course (40 mm) cannot be recommended
according to this study (Wiman et al., 2009).
Steel material from culverts and road barriers is reused. Geosynthetics have only been
used in road construction in recent years and therefore there is no experience in
dismantling such materials. In each road demolition project, a control programme
should be drawn up, where complicating materials are alerted in order to obtain a
management that is economically and environmentally successful (Andersson, 2009).
6.4
Unwanted materials, hazardous waste
Examples of hazardous waste and other materials that are unwanted in road recycling
activities are tar and asbestos. Here is described how tar asphalt is handled in Sweden.
6.4.1
Tar
Old Swedish asphalt pavements, from 1940 to the middle of the seventies, often contain
coal tar (Figure 8). It is estimated that about 0,7–1,1 million tonnes of asphalt from
these pavements are excavated every year. Supposing that 25% of these materials
contain tar, about 170,000–250,000 tonnes of tar containing recovered asphalt arise
every year (Wik et al., 2005).
Figure 8 Examples of road constructions containing tar in the lower layers.
6.4.1.1 Legal regulations (national implications)
Dismantled and excavated asphalt pavements containing tar asphalt are considered
hazardous waste according to the Swedish waste regulation and European Waste Code.
Generally, waste is regarded as hazardous if the content of carcinogenic compounds is
46
VTI notat 14-2011
larger than 0.1%. However, the Swedish Road Administration does not regard tar
containing asphalt that is recycled on-site (in the same road) as waste.
If the road area will be used for other purposes after the dismantling, the soil has to be
cleaned from tar containing asphalt to an acceptable extent. The Swedish Environmental
Protection Agency has set up general target values for the residual content of various
types of PAHs, depending on their molecule weight. For example, the target value for
cleaned areas for future housing estates is 1 mg/kg TS for PAHs with high molecule
weight, while the corresponding value for cleaned areas for future industrial estates is
10 mg/kg TS.
6.4.1.2 Identification techniques
There are various techniques to identify tar in an asphalt layers. A relatively simple
method, which also can be used in field, is to use spray paint and UV lamp on cored
specimens or excavated samples (Figures 9–11). The result indicates if the sample
contains tar and in which layer, but the amount cannot be calculated. Odour is also a
god indicator of tar.
Figure 9 Equipment for the spray test
(UV lamp and spray paint).
Figure 10 Sprayed samples in daylight with
visible colour changes.
Figure 11 Specimens illuminated in the dark with UV light. The left specimen contains
tar, the right specimen does not.
Recommendations for sampling and analyse of tar containing asphalt material are given
in (SRA, 2004).
VTI notat 14-2011
47
Sampling
Sampling is carried out after a positive result of field analysis. Methodology for
sampling of asphalt material from roads or from heaps for asphalt recycling is described
in (SRA, 2000). This methodology can also be used for tar containing asphalt, but then
it is very important that cored samples from the tar containing road include all layers to
be removed. Frequency of sampling (number of samples per tonne) etc. is described in
the SRA report but can also be determined in dialogue with the road owner.
Sample preparation
If tar presence has been confirmed, the sample (cored from the road or sampled from
intermediate storage) has to be crushed down to a maximum grain size of 20 mm. The
sample weight should be 3–5 kg crushed reclaimed asphalt material. Sampling and
sample preparation should follow SS-EN 932-13. The granules are extracted thereafter
according to SS-EN 12697-14. The extract is stored in glass bottles supplied by an
analytical laboratory. Unless otherwise stated, a simple test can be performed. The
extraction can be made by an asphalt laboratory.
Analysis
The extract is usually analyzed by gas chromatographic mass spectrometry, GC-MS,
with respect of 16 PAHs. PAH content converted from the entire mass of the sample is
expressed in mg/kg dw (dry weight). The unit mg/kg is the same as ppm (parts per
million).
There is no analysis showing how much coal tar a material contains. However, it is
known that coal tar contains high levels of polycyclic aromatic hydrocarbons, PAHs,
and PAH content is therefore used as an indicator of tar. Some individual PAHs are
classified as carcinogens. The group of “16-PAHs” has been identified by the Swedish
Environmental Protection Agency and includes seven PAHs classified as carcinogenic
(Table 11).
Table 11 The group “16-PAHs”. After (SEPA, 1996).
Carcinogenic PAH
Other PAH
Benso(a)antracen
Naftalen
Chrysen
Acenaftylen
Benso(b)fluoranten
Acenaften
Benso(k)fluoranten
Fluoren
Benso(a)pyren
Fenantren
Indeno(l,2,3-cd)pyren
Antracen
Dibenso(a,h)antracen
Fluoranten
Pyren
Benso(g,h,i)perylen
3
4
Tests for general properties of aggregates – Methods for sampling.
Bituminous mixtures – Test methods for hot mix asphalt – Part 1: Soluble binder content.
48
VTI notat 14-2011
6.4.1.3 Separation techniques
If it is possible, pure asphalt layer should be separated from tar contaminated asphalt by
cold milling. On older streets and roads it can be difficult in practice to effectively
separate the asphalt, unless control is very accurate, because the layer thickness can
vary greatly. However, wearing course should in most cases be possible to separate
from other asphalt layers. For milling, a margin of safety compliance due to tar may
have penetrated a few cm of the adjacent (above and below) asphalt layer. At
excavation of asphalt, it is difficult to separate tar contaminated layers from pure asphalt
layers but the amount of unbound material in the masses should be limited. Left-over
layers of tar asphalt should be excavated and removed not be milled. It is for example
difficult to mill in grouted macadam (IM) and milling gives a stronger odour than
excavation. The material is also significantly more granulated when milling instead of
excavating, which can complicate the retention of the masses.
Recommendations for the dismantling of old asphalt layers:
 determine whether the asphalt pavement contains tar
 consult responsible environmental authorities if tar containing materials will be
reused
 try to keep contaminated materials separated from pure bituminous mixtures
 inform the staff about the tar content in the asphalt material.
6.4.1.4 Recycling solution
According to SRA, excavated asphalt pavements containing less than 70 mg/kg of
16-PAH” are regarded free from tar and can be reused without restrictions as surface
layer or base course. Asphalt pavements containing tar, i.e. containing at least 70 mg/kg
16-PAH, must be handled as follows:
For all tar containing asphalt materials:
 The asphalt material is primarily reused within the same site.
 The asphalt material is used as bound or unbound road base.
 Cold or semi-hot recovery method used.
 Base layer is covered with dense wearing course.
 The asphalt material can be used in such sound barriers if they are covered by
plastic sheet or other water diversion protection layer.
 The asphalt material must be above the groundwater table.
 Staff dealing with the material should be informed.
At concentrations between 300 and 1,000 mg/kg of 16-PAH:
 Intermediate storage is done only if the asphalt material cannot be used directly. The
storage should be limited in time.
 Stored material has to be covered to prevent leaching.
 Storage of uncovered material should be performed at close support and combined
with device for disposing of leachate water.
 Storage should not be made at sensitive sites, such as water protection area.
 Reuse is not made within sensitive land areas.
At concentrations above 1,000 mg/kg of 16-PAH: See section 6.4.1.5.
VTI notat 14-2011
49
6.4.1.5 Non- road end-of-life treatments (incineration or disposal)
A special investigation has to be made on how to handle the material in the best
environmental and technical way (recycling, destruction or disposal).
6.4.2
Asbestos
Asbestos is normally not used in Swedish road construction. However, there are special
rules in the occupational safety and health act for handling of asbestos.
6.5
Secondary aggregates
During the last 30–35 years, much research has been performed in Sweden on the
mechanical and environmental properties of various secondary aggregates. Several
laboratory studies have been reported and a number of test roads and test areas with
secondary aggregates like steel slag, incinerator bottom ash and fly ash has been built.
Some of the roads have been monitored, for example with respect to long-term strength
and environmental impact and a few has been excavated within research projects in
order to study the long-term properties of the aggregates used.
Since the late 90ies, Swedish waste producers and industry associations, such as
Värmeforsk (combustion residues), Avfall Sverige and Jernkontoret (metallurgical
residues), have funded research and development projects with the purpose to increase
the possibility of using waste, for example in road construction.
Furthermore, in recent years the Swedish Road Administration, SRA, and the Swedish
Rail Administration have developed guidelines for use of alternative materials in
construction (SRA, 2007c). The guidelines describe the legal, technical and
environmental considerations to be made in the use of alternative materials. They also
give examples of materials currently used or tested as construction materials: processed
MSWI bottom ashes and other bottom ashes, Fly ashes (from coal and solid biofuel),
Foam glass, Blast furnace slag, Crushed concrete, Ferrochrome slag, Shredded tyres and
Iron sand (Table 12). The report also presents examples of technical properties of these
materials (Table 13). The publication is based on many years of research.
Table 12 Alternative materials in a road construction – examples of use, properties and
reference to technical quality. After (SRA 2007c).
Part of the road
structure
Function
Alternative materials
(examples)
Useful properties*
Bound base
course
Base course
Blast furnace slag, fly
ash with or without
crushed rock materials
Stiffness increase
(hardening) with time frost
heave
Unbound base
course
Base course
Fly ash, crushed
asphalt, crushed
concrete
Stiffness increase
(hardening) with time
Sub-base
Base course
Fly ash, iron sand,
ferrochrome slag
crushed asphalt, blast
furnace slag, crushed
concrete or MSWI
bottom ash with or
Frost heave,
capillary break, draining,
50
VTI notat 14-2011
without crushed rock
materials
Lower sub-base
Frost
insulation,
material
separation
Ash materials, some
slag types, iron sand,
foam glass, tyre shreds
Frost heave, draining, low
density
Subgrade
Fill
Ash materials,
metallurgical slag, foam
glass, tyre shreds
Frost heave, low density
Subgrade
Light-weight
fill
Some ash materials
and slag types, foam
glass, tyre shreds
Frost heave, low density
Stabilization of
all unbound
layers
Base course
Metallurgical slag, ash
material
Stiffness increase
(hardening) with time.
*Valid for all structural components, but not always relevant in pavement design and use of the components.
Table 13 Example of technical properties for some secondary material. After (SRA
2007c).
Maximum
dry density
(t/m3)
Bulk density
(t/m3)
Density for
design purposes
(t/m3)
Optimum
water
content
Permeability
Friction
angel
Stiffness
modulus
()
(MPa)
(m/s)
(%)
Crushed
concrete
1,8–2,0
8-12
Blast furnace
slag
1,8–2,1
1,5-2.0
Iron sand
careful
compaction is
necessary
2,0-2,3
Ferrochrome
slag
2,4–2,6
1,75-2,55
Fly ash
0,8–1,7
0.7-2,0
(loose
compaction)
2,4
careful
compaction is
necessary
Thermal
conductivity
(W/(m* C)
(m)
10-6-10-5
200-480
5-7
2,0 loose
(compaction)
Water
suction
height
200-600
2*10-6-5*10-5
34-43
0,3-0,7
100-200
0,1-0,15
0,26-0,47
0,12-0,18
0,36-1,8
2,5-3,0
7*10-5-1*10-3
200-230
30-60
10-9-10-7
50-150
0,5-0,9
45–140
0,2–0,5
-7
-5
MSWI bottom
ash
1,4–1,8
1,2–1,8
14–20
10 –10
Bottom ash
apart from
MSWI
0,8–1,7
0,7–1,7
13–33
10-8–10-4
Foam glass
0,2–0,3
0,18–0,35
Tyre shreds
0,67
0,5–0,7
Natural gravel
1,7–1,9
35–38
15–30
0,3–>0,8
0,1–0,6
10-3–10-1
36–45
75–150
<0,12–0,17
0,10–0,15
Does not
matter
> 10-2
21–38
0,2–0,5
Capillarity
breaking
layer
0,2
6–10
> 10-2
30–37
0,35–0,40
0,6–01,8
(one
sample)
In parallel with the SRA guidelines, the industry funded a broad project in order to
produce manuals for the use of “their” alternative materials in road and construction
works. The manuals have been developed by the Swedish Geotechnical Institute in
collaboration with Luleå Technology University and industry representatives. So far,
the series of manual includes: Fly ash (Munde et al., 2006), MSWI bottom ash (Arm,
2006), Foam glass (Eriksson & Hägglund, 2008) and Tyre shreds (Edeskär, 2008).
VTI notat 14-2011
51
6.5.1
Metallurgical slag
The mechanical and environmental properties of steel slag from electric arc furnace
(EAF), blast furnace slag (both air-cooled and granulated), ferrochrome slag and “iron
sand” (granulated slag from copper production) have been studied in several Swedish
research projects. The SRA has published guidelines for using air-cooled blast-furnace
slag in road construction (SRA, 2005).
A ten year old road with EAF steel slag in the subbase was excavated and sampled in
order to study the ageing reactions occurred since the construction (Figure 12). Among
the conclusions were mentioned that fresh EAF steel slag age with time due to carbonation and other processes leading to pH decrease and subsequent change in leaching
properties (Figure 13). Road edges with uncovered shoulders allow exposure to these
processes. If fresh material has been used in an old road, excavation will show that the
road edge material has aged much more than the road centre material, which means that
leaching characteristics for the material differs across the road section (Arm et al.,
2008b).
Figure 12 Sampling of EAF steel slag subbase in Smedjebacken Sweden in 2006. After
(Arm et al., 2008b).
52
VTI notat 14-2011
Figure 13 Results from laboratory and field study of an old excavated road with EAF
steel slag in the subbase. Percolation tests, SEM photo of particle surface and pH profile
of the road. Smedjebacken, Sweden in 2006. After (Arm et al., 2008b).
Within the European ALT-MAT project a Swedish road with blast furnace slag in the
subbase was excavated and the results reported (ALT-MAT, 2000).
EAF slag has also been tested as aggregate in asphalt wearing courses, especially in
roundabouts. Good resistance to wear by abrasion from studded tyres and good
durability properties made it also interesting in porous asphalt, a bituminous mix type
commonly used for better drainage and to reduce noise. (SALAR, 2008).
6.5.2
Incinerator ash
The properties of various incinerator ash materials have been studied in several Swedish
research projects. Since the end of the 90ties, the research program “Environmentally
correct utilisation of non-coal ashes”, funded by Värmeforsk Sweden AB, has produced
much knowledge. All research reports have an English summary and can be downloaded from www.varmeforsk.se. Examples of reports in this programme are (Arm et
al., 2008a) and (Arm et al., 2008b). Furthermore, all laboratory and field data arising
within the research program is collected in a free access database called ALLASKA
(= “all ash” in Swedish). The database can be reached at
http://www.askprogrammet.com/BakgrundALLASKA.shtm.
Test sections with processed municipal solid waste incinerator (MSWI) bottom ash in
the sub-base retain its strength after several years, about 70% of that of reference
sections with crushed rock in the sub-base (Figure 14 and 15). Comparison between the
leachates from the whole test section and results from previous laboratory leaching of
the MSWI bottom ash alone showed significantly different patterns. This should be
taken into account in the assessment of potential use. (Arm et al., 2008a).
VTI notat 14-2011
53
Lagermodul (BL+FL)
(MPa)
250
200
150
100
50
0
1999-06-09
2000-06-27 provsträcka
2004-06-09
2006-06-08
2008-06-12
Figure 14 Törringevägen test road, stiffness change of the test structure. Layer moduli
for the combined layer of base of crushed granite and sub-base of MSWI bottom ash,
evaluated from FWD measurements. Mean value of ten points. The test structure is
designed according to Figure 9b. (Arm et al., 2008a).
(mm)
130
Slitlager + AG
130
80
Krossat berg 0-40 mm
150
Krossat
berg
465
0-100 mm
Slaggrus 465
0-45 mm
Lermorän
Figure 15 Törringevägen test road, reference structure (left) and test structure (right).
Test structure from top to bottom: surface course + asphalt bound base course, unbound
base course of crushed rock, MSWI bottom ash and clay moraine. (Arm et al., 2008a).
A nine year old test section with processed municipal solid waste incinerator (MSWI)
bottom ash in the sub-base was excavated and sampled in order to study the ageing
reactions occurred since the construction (Figure 16). Among the conclusions were
mentioned that the bottom ash from the pavement edge was more aged than the bottom
ash from the road centre, which could be seen in the leaching properties. However, no
difference in pH was found, instead the differences were said to be caused by
differences in water exposure (Figure 17). Road edges with uncovered shoulders allow
this to happen which means that when excavating an old road with bottom ash, various
leaching characteristics for the material across the road section can be expected (Arm et
al., 2008b).
54
VTI notat 14-2011
Figure 16 Sampling of MSWI bottom ash subbase in Malmö Sweden in 2006. After (Arm
et al., 2008b).
Figure 17 Results from laboratory and field study of an old excavated road with MSWI
bottom ash in the subbase. Percolation tests, SEM photo of particle surface and pH
profile of the road. Malmö Sweden in 2006. After (Arm et al., 2008b).
A 16 year old road partly constructed with MSWI bottom ash in the subbase was
excavated in the year 2003. Before excavation FWD measurements were performed. All
layers were sampled and from the ash layer specimens for cyclic load triaxial tests were
cored. Comprehensive environmental tests were performed. It was concluded that it was
easy to excavate the different layers in the road construction separately which is
favourable for future reuse (Bendz et al., 2006).
VTI notat 14-2011
55
6.5.3
Recycling in unbound road layers
According to the present manuals for various secondary aggregates, the materials can be
excavated and reused again in a similar design or stored for later use. However, there is
only little experience of putting this into practice.
6.5.4
Recycling in hydraulically bound road layers
There is only little knowledge in Sweden about how to recycle secondary aggregates in
hydraulically bound road layers.
6.5.5
Recycling in bituminous bound road layers
There is only little knowledge in Sweden about how to recycle secondary aggregates in
bituminous bound road layers. Test sections with steel slag as aggregate in asphalt
surface layer are currently monitored, but no research reports are available so far.
6.6
Vehicle tyres
Every year, approximately 70,000 tonnes of used tyres are generated in Sweden. All
returned tyres are reused or recycled in one way or another, either as a material or in
energy recovery. Today, half of all collected tyres go to energy recovery in heating
plants and to the cement industry and half to material reuse or recycling. Examples on
reuse are in retreads and in blasting mats. An example of recycling is when the rubber
raw materials is utilized or replace other materials in constructions. The trend is towards
increased material reuse and reduced energy recovery. This has taken place thanks to
research and practice providing a more profound knowledge of utilisation and the
environmental impact.
6.6.1
Identification
Tyre shreds are fragmented end-of-life tyres, mainly from passenger cars but also from
heavy vehicles. The size of the individual shreds is controlled by sieving and reshredding of coarse shreds. The first pass results in 100–300 mm large tyre shreds, the
second pass results in 100–150 mm and finer tyre shreds are re-processed until the
material passes the desired sieve size. The result is disc shaped tyre shreds with
protruding steel cord. Smaller tyre shreds have relatively more protruding steel cord
compared to coarser fractions (Figure 18). (Edeskär, 2006).
56
VTI notat 14-2011
Figure 18 Different sizes of tyre shreds (Edeskär, 2006).
In USA there is an established standard5 for nomenclature and determination of some of
the technical properties, and in Europe the work with establishing a common standard6
is now in progress. These two standards will to some extent differ in nomenclature and
procedures to determine properties. (Edeskär, 2006)
6.6.2
Handling and preparation
6.6.2.1 Collection and transport
The recycling of tyres follows the Swedish regulation7 on producer responsibility for
tyres. This liability means that whichever company places tyres on the market must also
accept liability for how they are dealt with at the end of their service lives. Regulator is
the Swedish Environmental Protection Agency (SEPA) in cooperation with local
environmental agencies.
Tyre importing companies can join the tyre industry’s recycling system (Figure 19),
which is organized by the Swedish Tyre Recycling Ltd, (SDAB). SDAB is a trade
association owned by Tyre, Rims & Accessories suppliers Association (DFTF) and
Tyre Specialist Association (DRF) and it is responsible for members’ obligations under
the Regulation including the reporting to SEPA. SDAB has in turn hired a contractor for
all tyre collection and recycling throughout Sweden.
Recycling is funded by the consumers that pay a recycling fee when purchasing new
tyres.
5
ASTM D 6270-98 Standard Practice for Use of Scrap Tires in Civil Engineering Applications. American.
Society for Testing and Materials. 1998.
6
prEN 14243:2004 Post-consumer tyre. Materials and applications.
7
SFS 1994:1236.
VTI notat 14-2011
57
Figure 19 The path of the tyre through the Swedish recycling system (SDAB, 2009).
Tyres are collected in local garages and tyre companies and transported to a depot
where they are fragmented. Private persons can leave their tires without rims to the tire shop
free of charge. Only clean tyres are accepted.
6.6.2.2 Technologies for product preparation
The tyres are fragmented by a shredder, normally in mobile processes. The fragmentation is mainly due to transportation reasons in order to reduce the volume and takes
place regardless of the future use. The shredding is executed on hard surfaces to avoid
mixing soil into the material. The tyre shreds are stored at the shredding plant separate
from other materials and it is delivered free from foreign objects and pollutants. The
size of the shreds depends on how many times the tyres have been fragmented and
whether the material has been sieved.
Presently, there is no production of tyre shreds in Sweden and all shreds have to be
bought abroad. However, a factory will be built in the south western part of Sweden.
The plan is to produce two fractions, 1–4 mm and powder, from about 30,000 tonnes of
tyres (SDAB, 2009).
6.6.3
Recycling whole tyres as lightweight / massive material in
embankments
No Swedish experience.
58
VTI notat 14-2011
6.6.4
Recycling as aggregate in rubber-based pavements (sport fields,..)
The tyres can be recycled in the form of tyre shreds as lightweight filling material in
noise barriers, as frost insulating material in roads, as drainage in landfills and as elastic
bed in riding and trotting tracks. The Swedish Geotechnical Institute (SGI) has
published a handbook that describes both technological and environmental perspectives
(Edeskär, 2008).
Lightweight fills are used to reduce stress on the underlying soil in order to reduce
consolidation settlements or to increase global stability of constructions by reducing
load. The low bulk density of tyre shreds, compared to soil materials, makes the
material suitable as lightweight fill material. The high porosity and drainage capability
limits the presence of water in the fill and the low maximum water content in individual
tyre shreds preserves the low bulk density over time.
In design, the initial compression, creep, maximum in-situ density and thickness must
be considered. The initial compression depends on the stress from overlaying layers. If
the fill is subjected to load, creep will occur under a long period. The creep in a Swedish
test road was at average 5% during two years. It will result in slightly increased density
and should be encountered for in design of lightweight fill applications.
To limit the potential leaching effects, the fills should be placed above the ground- or
surface water table and ensure the surface run-off beneath the tyre shred fill (Figure 20).
In large fills the fire risks should be considered. ASTM8 recommends a maximum
height of tyre shreds fills of 3 m. (Edeskär, 2006).
Figure 20 Tyre shreds used as lightweight fill in a noise barrier (Edeskär, 2006).
Frost penetration combined with accessibility of water causes frost heave, especially in
fine grained soils. Thawing and corresponding bearing capacity loss due to low draining
capacity in the partly frozen soils is also common. Thermal insulation materials are used
to reduce frost penetration. The low thermal conductivity in tyre shreds makes the
material suitable for thermal insulation material (Figure 21). Combined with the high
permeability, the material could decrease the frost heave by acting as a capillarity
breaking layer and increase bearing capacity at thawing by drainage of excessive water
(Edeskär, 2006).
8
ASTM D 6270-98
VTI notat 14-2011
59
Figure 21 Tyre shreds used as thermal insulation in road construction (Edeskär, 2006).
In landfill construction, tyre shreds can be used as drainage layers in the bottom
construction and in the top cover to protect the sealing layers to have water pressures
being built up (Figure 22). The bottom drainage layer is a part of the leachate collection
system used for transportation of leachate for treatment or release. Normally a gas
drainage system is installed in landfills. The gas drainage system collects landfill gas,
which has a high greenhouse effect potential due the high content of methane. The gas
also increases the risk for landfill fires (Edeskär, 2006).
Figure 22 Tyre shreds used as drainage layer in top cover, as gas drainage layer and as
bottom drainage layer (Edeskär, 2006).
6.6.4.1 Environmental properties
Among the metals it is primarily iron and zinc that is of concern due to the high
concentrations found in leaching studies. Iron hydroxides could be an aesthetic problem
if precipitated outside a construction and will affect the release of other charged ions
which may be accumulated absorbed on iron hydroxides or released if the hydroxides
are dissolved. For zinc to be toxic, high concentrations are needed. If the recipient is
sensitive to additional zinc sources the use of tyre shreds from large constructions to
small recipients should be considered. In most cases the zinc release are acceptable in
60
VTI notat 14-2011
terms of ecological effect levels in a potential recipient. Leaching of PAH compounds is
insignificant. This is supported by the conclusions of for example Scientific committee
on toxicity, ecotoxicity and the environment (CSTEE)9. Tyre shreds leaches phenols. In
evaluation of the effects, natural sources and sinks, i.e. biological degradation, must be
considered. Aerobic conditions in the recipient should be sufficient to biodegrade the
obtained phenol concentrations in the leachate. The other studied elements are not
considered to be of environmental concern (Edeskär, 2006).
6.6.5
Recycling as modified binder in asphalt pavements
Since 2007 the Swedish Road Administration has built some test roads with rubber
bitumen in the asphalt surface layer. The technical aim for this mix type is primary to
increase the layer’s service life, reduce noise level or prevent crack propagation.
A dense mix has been used with good results regarding the crack propagation
prevention. However, the increased temperature of the mix increases the smoke
generation during laying. The smoke is not dangerous to health but it might be
troublesome to the workers. To reduce the smoke generation, tests with blower
equipped asphalters will be made (SDAB, 2009).
The rubber bitumen consists of rubber crumbs with particles less than 50 mm mixed
with bitumen and the roads are constructed according to experience and specifications
from Arizona Department of Transportation (ADOT).
6.6.6
Non-road end-of-life treatments (incineration or co-processing)
In 2008, just over 50% of the collected tyres were used as fuel, either in the cement
industry or in municipal district heating plants.
6.7
Polluted soils and sediments
In general, SRA promotes recycling as much as possible in road demolition projects. In
each project, a control programme should be drawn up, where complicating materials
are alerted in order to obtain a management that is economically and environmentally
successful (Andersson, 2009). In the first place, excavated soils are recovered in
construction of new roads in the neighbourhood.
SRA has written an administrative guide in cooperation with legal expertise (SRA,
2007a) which describes how to categorize excavated soil, when it should be regarded as
waste and when it should be considered hazardous waste, see section 1.2 in this report.
SRA has also developed a manual for handling sediment and soil from road ditches,
which describes among others when and how the soil should be sampled and also
environmental criteria for different uses (SRA, 2007b). Soils and sediments from roads
with high traffic volume (> 10,000 vehicles/day) must be sampled and analysed before
use in the “road area”. If not classified as waste, generally no further notification or
license is required for the use. However, the place for use can require certain
precautions, e.g. for use in water protection area, national park and cultural reserves.
9
Questions to the CSTEE relating to scientific evidence of risk to health and the environment from polycyclic
aromatic hydrocarbons in extender oils and tyres, Document C7/GF/csteeop/PAHs/12-131103 D(03), European
Commission, Brussels.
VTI notat 14-2011
61
The coming Swedish regulations for use of waste in construction, mentioned in section
1.1.1, will imply some changes in the management of recycled soil.
6.7.1
Excess soil from excavation works
In some cases, excess soil from road works is transferred to landowners in the vicinity.
Only non-contaminated soil may be transferred. SRA will then contract with the
landowner, which means that the landowner takes over operations responsibility over
the masses. If the soil is contaminated or of poor quality, it must be deposited at a
municipal landfill for non-hazardous waste. If the soil contains high concentrations of
pollutants it must be disposed of at a landfill for hazardous waste. For disposed soil
there are special testing requirements, including leaching tests.
6.7.1.1
In-situ recycling and soil improvement technologies
SRA tries to recover all soil of sufficient quality in each road project. Primarily soils are
used as embankment filling. They can also be used for construction of road side area to
improve the road environment. This means, for example, use for filling around culverts
and crossings, to cover the slopes of hills or large rocks for facilitated vegetation
mowing or in order to stabilize steep road side area to improve road safety. Many low
quality materials, eg vegetation layers or soil containing silt and clay, can be used for
construction of noise barriers.
6.7.2
Sediment from road ditches and rainwater basins
There is a Swedish manual for handling sediment and soil from road ditches (SRA,
2007b). It gives guidance for sampling and analysis of sediment quality as well as
environmental criteria with benchmarks for assessing whether the sediment is suitable
for reuse. The environmental criterion is outlined in Table 4. The manual also describes
current environmental legislation relating to natural and cultural environment.
Furthermore, the manual contains analytical data for sediment samples taken from the
ditches of roads with different traffic volume (Figures 23 and 24).
Table 14 Environmental criterion for reuse of sediment from road ditches (SRA, 2007b).
Element
Pb
Cu
Zn
Cd
Canc PAH
Other PAH
Oil
Electric conductivity at
L/S 2
62
mg/kg TS
mS/m
Criteria for use in road construction
250
200
700
12
2
15
500
<70
VTI notat 14-2011
mg/kg TS
Zinkhalt 1998 - 2004
800
700
600
500
400
300
200
100
0
VV 1998:008
VV 2003
SGI 2004
VV-kriteri
väg/extern
0
20 000 40 000
60 000 80 000 100 000
ÅDT
Figure 23 Sampling of sediment
from road ditches (SRA, 2007b).
Figure 24 Total content of Zn in sediment from
road ditches of roads with different traffic
volume. Content is given in mg/kg dry soil and
traffic voume in number of vehicles per day
(SRA, 2007b).
About 400 wet ponds and similar treatment facilities for removal of pollutants from
highway runoff have been constructed in Sweden since the nineties. They prevent the
pollutants to be discharged to ground or receiving watercourses and they also provide
environmental protection in case of road accidents. In most ponds removing of
accumulated sediment will be needed to prevent clogging or remobilisation of polluted
sediment. The frequency of removing depends on traffic volume and the performance of
sediment chambers upstream of the treatment facility as well as on the vegetation and
the size and design of the ponds.
SRA has published a maintenance manual for runoff treatment facilities (SRA, 2008).
In addition to maintenance schedules and inspection checklist it includes advice and
techniques for sediment sampling, analysis, removal, disposal or reuse at the site. The
manual states that it is important to sample and analyse the sediment before removing it.
The reason is that that the degree of pollution determines which sediment handling is
suitable. Preferably the sediment should be reused within the treatment facility area. If
this is not possible, it should be treated at an approved treatment plant or landfilled. In
all cases dewatering could be necessary. The manual also reports results from previous
studies of sediment composition which give information on how the content of
pollutants and the leaching characteristics of sediment may vary.
6.7.3
Road cleaning waste
6.7.3.1 Anti-skid materials (gravel and sand)
Each year, nearly 750,000 tonnes of anti-skid material is swept up from Swedish roads,
streets and squares. The material can often be reused or recycled, but the solutions and
techniques vary among municipalities. To help, the Swedish Association of Local
Authorities and Regions has published a guide that presents solutions meeting high
standards for health and environment (Johansson, 2008). Possible solutions are: reuse as
anti-skid material, recycling as fill material, recycling in asphalt production or final
disposal. The report also takes up environmental risks and the national regulations for
handling the material. Several examples of how Swedish municipalities handle the
material are also provided.
VTI notat 14-2011
63
6.8
Green waste
6.8.1
From road shoulder maintenance
6.8.1.1 Grass
Haymaking on road shoulders is common in Sweden (Figure 25). However, the
vegetation is seldom collected and recycled by means of composting or anaerobic
digestion (Eriksson, 2009) During the early 2000s, there was a lot of advanced
experimental studies (SRA, 2000). Various haymaking techniques, logistics, costs and
possible contents of pollutants in the vegetation were investigated. One of the
conclusions was that collection of vegetation is optimal from biological point of view,
yet this is not performed in practice.
Figure 25 Haymaking on Swedish road shoulders.
6.8.1.2 Trees and bushes
Cutting of trees and bushes from the road shoulder is made regularly in Sweden.
Chipping of the cut vegetation occurs, but often the vegetation is left on the road
shoulder.
6.8.1.3 Natural vegetation layer
The design of roadside and vegetation is important for the road alignment in the
landscape. By taking advantage of the natural surface soil at the excavation work, you
can maintain a sustainable, climate-friendly and natural flora on the roadside. The SRA
has performed experiments with the return of surface soil, both in the forest environment and the re-establishment of roadside with species-rich meadows environment. The
experience is very good and has resulted in general recommendations in a pamphlet
which is also available in English (SRA, 1999).
6.8.2
On-site treatment
Not common in Sweden.
64
VTI notat 14-2011
6.8.3
Off-site treatment
Composting of grass and chipping for energy recovery in heating plants are common in
the management of municipal parks in Sweden but is rare in the maintenance of roads.
6.8.4
Biomass utilization
6.8.4.1 Compost
See section 7.3.
6.8.4.2 Biogas to energy
Wood chips from forest and park management is used as energy recovery in heating
plants in Sweden, not for biogas production. However, it is unusual in the maintenance
of roads.
6.9
References
ALT-MAT, (2000). Alternative materials in road construction, European, 4th RTD
Framework Programme, 1998-01–1999-12. European project financed by the European
commission.
Andersson, G. 2009-09-29, Swedish Road Administration, Region Mälardalen in
Eskilstuna, Road construction, verbal reference.
Arm, M. (2006). ”Slaggrus i väg och anläggningsarbete. Handbok.” (“MSWI bottom
ash in roads and construction works. Manual”) SGI Information 18:5, Swedish
Geotechnical Institute, Linköping.
Arm, M., Larsson, L., Tiberg, C., Lind, B. and Arvidslund, O. (2008a). ”Uppföljning av
slaggrusprovvägar – fallviktsmätning på provsträckor på Törringevägen i Malmö och
Dåvamyran i Umeå. Grundvatten- och lakvattenanalyser på provsträckor vid
Dåvamyran i Umeå” (“Monitoring of test roads with MSWI bottom ash in the sub-base
– FWD measurements and analyses of ground water and leachates”) Värmeforsk report
1081, Värmeforsk Service AB, Stockholm.
Arm, M., Suer, P., Arvidsson, H., Lindqvist, J-E., Frogner-Kockum, P., Larsson, L. and
Toomväli, C. (2008b). “Förutsägelse av långtidsegenskaper hos restprodukter – Teknik
och miljö i vägar” (“Prediction of long-term properties of by-products – Technical and
environmental properties in roads”) Värmeforsk report 1083, Värmeforsk Service AB,
Stockholm.
Bendz, D., Arm, M., Flyhammar, P., Westberg, G., Sjöstrand, K., Lyth, M. and Wik, O.
(2006). ”Projekt Vändöra – En studie av långtidsegenskaper hos vägar anlagda med
bottenaska från avfallsförbränning” (“The Vändöra test road, Sweden: A case study of
long-term properties of roads constructed with MSWI bottom ash”). Värmeforsk report
964, Värmeforsk Service AB, Stockholm.
Edeskär, T. (2006) “Use of tyre in civil engineering, Technical and Environmental
properties”. Doctoral thesis, Luleå University of Technology.
Edeskär, T. (2008). ”Gummiklipp. Handbok” (”Tyre shreds. Manual.”) SGI information
18:7. Swedish Geotechnical Institute, Linköping.
VTI notat 14-2011
65
Eriksson, L. and Hägglund, J. (2008). ”Skumglas i mark- och vägbyggnad” (”Foam
glass in ground and road construction”) SGI Information 18:1. Swedish Geotechnical
Institute, Linköping.
Eriksson, O. 2009-09-29, Swedish Road Administration, Borlänge, verbal reference.
Johansson, C. (2008). “Sopsand – Avfall eller resurs?: Hållbar hantering av halkbekämpningsmedel” (”Waste sand – Waste or resource?: Sustainable Management of
anti-skid material”). Swedish Association of Local Authorities and Regions, Stockholm.
Munde, H., Svedberg, B., Mácsik, J., Maijala, A., Lahtinen, P., Ekdahl, P. and Nerén, J.
(2006). ”Flygaska i mark- och vägbyggnad. Grusvägar.” (“Fly ash in ground and road
construction. Gravel roads”) SGI Information18:4, Swedish Geotechnical Institute,
Linköping.
SDAB 2009-09-29, “Svensk Däckåtervinning AB” (“the Swedish Tyre Recycling
Organisation”). http://www.svdab.se/
SEPA. (1996). ”Generella riktvärden för förorenad mark”. (”Generic values for
contaminated ground”). Report 4638. Swedish Environmental Protection Agency,
Stockholm.
SEPA. (2009). “Miljömålsportalen” (“Environmental Objectives Portal”)
www.miljomal.nu/Environmental-Objectives-Portal. Swedish Environmental Protection
Agency, Stockholm.
SGU. (2008). “Aggregates – Production and resources 2007”. Per. Publ. 2008:3. The
Geological Survey of Sweden, Uppsala. www.sgu.se
SALAR. (2008). “Slitage i circulation” (“Wear in roundabouts”). ISBN 978-91-7164360-5. Swedish Association of Local Authorities and Regions, Stockholm.
SRA. (1999). “Etablering av naturlig vegetation” (”Establishment of natural vegetation”). Vägverkets dokumentation 88865. Swedish Road Administration, Borlänge.
SRA. (2000). “Haymaking and collection of vegetation from road zone”. Swedish Road
Administration, Borlänge.
SRA. (2000). ”Provtagning, provning och bedömning av provningsresultat av asfaltmaterial för återvinning” (”Sampling, testing and evaluation of test results of asphalt
materials for recycling”). VVMB 620, Publ. 2000:109. Swedish Road Administration,
Borlänge.
SRA. (2004). ”Hantering av tjärhaltiga beläggningar” (”Management of bituminous
pavements containing tar”). Publ. 2004:90. Swedish Road Administration, Borlänge.
SRA. (2005). ”Luftkyld masugnsslagg – hyttsten – i vägkonstruktioner” (”Air-cooled
blast furnace slag in road constructions”). Publ. 2005:39. Swedish Road Administration,
Borlänge.
SRA. (2007a). ”Hantering av uppgrävda massor – administrativa krav” (“Handling of
excavated materials – administrative regulations”). Publ. 2007:99. Swedish Road
Administration, Borlänge.
SRA. (2007b). ”Hantering av vägdikesmassor – råd och rekommendationer” (”Handling
of highway ditch masses”) Publ. 2007:101. Swedish Road Administration, Borlänge.
66
VTI notat 14-2011
SRA. (2007c). ”Alternativa material i väg- och järnvägsbyggnad” (”Alternative
materials in road and railway construction”). Publ. 2007:110. Swedish Road
Administration, Borlänge.
SRA. (2008). ”Skötsel av öppna vägdagvattenanläggningar” (”Maintenance of open
facilities for storm water from roads”) Publ. 2008:30. Swedish Road Administration,
Borlänge.
SRA. (2009). “VVAMA Anläggning 09” (“VVAMA Construction 09”). Publ.
2009:111. Swedish Road Administration, Borlänge.
SVEKOM. (2004). ”På väg igen – vägen tillbaka för återvunnen asfalt” (”On the road
again – the road back for recycled asphalt”), Swedish Association of Local Authorities,
Stockholm.
Wik, O., Larsson, L., Andersson-Sköld, Y. & Jacobson, T. (2005). ”Sammanställning
av underlag till vägledning om hantering av tjärasfalt” (”Preparatory work for manual
on handling of tar containing asphalt”). Report dated 2005-12-05. Swedish
Geotechnical Institute, Linköping.
Wiman, L., Carlsson, H., Viman, L. & Hultqvist, B-Å. (2009). ”Prov med olika överbyggnadstyper” (”Long-term performance study of different pavement structures”). VTI
Report 632:2009. Swedish Road and Transport Research Institute, Linköping.
VTI notat 14-2011
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VTI notat 14-2011
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