På senare år har intresset för indränkt makadam (IM) ökat markant. Mer än 2 miljoner kvadratmeter läggs årligen, oftast som ett kombinerat slit- och bärlager eller slit- och justeringslager, på låg- till medeltrafikerade vägar. Erfarenheterna är hittills mycket positiva enligt uppföljningar som pågått mellan 2007 och 2014 och utförts av VTI. Ett flertal prov- och kontrollsträckor med placering i Småland och Östergötland, ingår i uppföljningen. 

Dåvarande Vägverket startade år 2007 ett projekt i syfte att lyfta fram och vidareutveckla IM-tekniken. Frågor som belyses i projektet är:

• relevanta provningsmetoder för indränkt makadam
• vilken effekt åtgärden får på bärigheten
• faktorer som påverkar stabiliteten
• relevanta krav på stenmaterialet
• makadamfraktioner/ kornstorleksfördelning
• alternativa bindemedel till bitumenlösning
• typ och mängd av bindemedel

Vid tillverkning av stål tillsätts kalk och dolomit som slaggbildare. Det innebär att slagg erhålls som biprodukt. Stålslagg används i många länder till bundna och/eller obundna lager i vägkonstruktioner. Denna rapport behandlar slagg från stålverket i Smedjebacken, EAF-slagg (Electric Arc Furnace), som ballast i asfaltbeläggning. Goda erfarenheter finns från Halmstad och Laholm där EAF-slagg använts till slitlager på högtrafikerade gator/vägar sedan början av 1990-talet. I Danmark har EAF-slagg från Smedjebacken använts frekvent i cirkulationsplatser och vägar/gator med intensiv trafik. Slaggen från Smedjebacken har goda mekaniska egenskaper. Kornen blir efter krossning i flera steg kubiska men behåller samtidigt sin skrovliga yta genom porositeten, vilket innebär att asfaltbeläggningen får en mycket god stabilitet. Genom att slaggen innehåller fri kalk i lämplig mängd (<0,5 %) blir beständigheten mot vatten mycket bra. För att eliminera risken för svällning lagras den utomhus i cirka ett år. Slaggen från Smedjebacken har god volymbeständighet. Metallinnehållet avskiljs innan slaggen krossas och siktas till lämpliga sorteringar. Sorteringar större än 4 mm används normalt till asfaltbeläggning. Slaggen har hög densitet (hög halt av järnoxid), vilket tillsammans med ytporerna noga måste beaktas vid proportioneringen av asfaltmassan. Bindemedelshalten är lägre i slaggasfalt än konventionell asfalt. Ett antal provsträckor med stålslagg i slitlager, ABS11, utfördes i Dalarna under åren 2005–2008. Vid Smedjebacken (2005) och Borlänge (2006) lades slaggasfalt i cirkulationsplatser. På väg 68 norr om Horndal (2007) utfördes en 300 meter lång provsträcka. Ett större objekt med stålslagg, ABS11, lades på väg 50 mellan Grängesberg och Ludvika (2008). I det objektet inblandades 20 procent porfyr i asfaltmassan. För att reducera bulleremissioner har stålslagg använts på Skälbyvägen i Järfälla kommun, Swedrain8 (2010) samt i en provsträcka med dränerande asfalt, ABD11 (övre lagret i en dubbeldrän) på E4, Husqvarna (2010). Ytterligare en sträcka med ABT16, innehållande slagg i samtliga fraktioner, har testats på en gruvväg i Garpenberg (2011) med hög andel tung trafik. Flera av objekten har stor trafikvolym eller hög andel av tunga fordon. Provsträckorna har årligen okulärt följts upp med skador i fokus. Vid några tillfällen har makrotextur, spårdjup och jämnhet undersökts. Tillgängliga laboratorieundersökningar för respektive objekt samt data om trafik och vägtyp redovisas också i rapporten. Sammanfattningsvis visar uppföljningarna att slaggasfalten fungerat mycket bra. Undersökningarna av asfaltmassa och asfaltbeläggning visar på mycket goda egenskaper ifråga om stabilitet, styvhet och beständighet, vilket gör den särskilt lämplig för utsatta ytor. Även slitstyrkan har visat sig vara acceptabel för svenska förhållanden med dubbdäckstrafik vintertid. Inga beläggningsrelaterade skador såsom stensläpp, sprickor eller andra defekter har observerats på i undersökningen ingående objekt. Slaggasfalten har som förväntat god friktion. Bullerreduktion ligger för täta eller halvtäta asfaltbeläggningar cirka 1 decibel lägre än för jämförbara sträckor med konventionell asfalt.

During the manufacturing process of steel, lime and dolomite are added as fluxes. These then combine with some of the melted impurities and form a slag byproduct. In many countries steel slag is used in both bound and unbound road construction layers. This report discusses the use of the byproduct from the steel mill in Smedjebacken, EAF (Electric Arc Furnace) slag, as an asphalt aggregate. Good experiences with such a material can be found in Halmstad and Laholm, where EAF slag has been used in surface courses on high traffic volume roads since the beginning of the 1990s. In Denmark, EAF slag from Smedjebacken is frequently used in roundabout construction and on roads with intensive traffic. The slag from Smedjebacken has good mechanical properties. The aggregate, after crushing in several steps, has a cubic form but still retains a rough surface texture due to its porous nature. This results in a very stable asphalt road surface. The slag contains a suitable amount of free lime (<0.5%), so resistance against water permeability is very good. To help eliminate any risk of swelling, aggregate is stored outdoors for about a year. The slag from Smedjebacken has good volumetric stability. Metal content is separated off before the slag is crushed and graded into appropriate aggregate fractions. Aggregate size greater than 4 mm is normally used for asphalt surfacing materials. The slags high density (high content of iron oxide) and surface porosity must be carefully considered during the design of the surfacing material. Slag asphalt binder content is lower than conventional asphalt. A number of test sections, where steel slag was used as a surface course, ABS11 (SMA) aggregate, were constructed in Dalarna between 2005 and 2008. At Smedjebacken (2005) and Borlänge (2006), slag asphalt was used in roundabout construction. On Road 68, north of Horndal (2007), a 300 metre long test section was constructed. A larger project using steel slag, ABS11, was carried out on Road 50 between Grängesberg and Ludvika (2008). In this project, the asphalt mix contained 20 per cent porphyry aggregate. To reduce traffic noise emissions, steel slag asphalt (Swedrain8) was used in Skälbyvägen, Järfälla (2010,) and in a test section with drainage asphalt (ABD11 - upper layer in a double drain construction) on the E4, Husqvarna (2010). Another section, constructed with an ABT16 (dense-graded asphalt concrete) containing slag in all fraction sizes, has been tested on a mine access road, with a high volume of heavy traffic, at Garpenberg (2011). Many of the test sections are subjected to high traffic volumes or have high proportions of heavy vehicles. Test sections have been visually inspected for defects each year. On a few occasions, macro texture, rut depth and evenness have also been investigated. Laboratory test results, traffic data, and road information are also presented in the report. In summary, the inspections have shown that the slag asphalt has performed very well. Investigations of the asphalt mix and road surface have shown very good results in terms of stability, stiffness and durability. This makes the material particularly suitable for vulnerable areas. Even durability is deemed acceptable for Swedish winter conditions which involve the use of studded tyres. No defects, such as stone loss, cracking or other surface type defects were observed during the inspection surveys. The slag asphalt, as expected, provided good friction values. Noise reduction levels, for dense or semi-dense asphalt were about 1 dB lower when compared with similar sections with conventional asphalt surfacing.

In connection with the construction of the highway on E4 between Strömsnäsbruk and the county border to Skåne in 2004-2006, about 100 000 tonnes of asphalt were recycled by new technologies according to Swedish standards. These asphalt materials came mainly from those parts of the old E4 with adjoining sections of road that were dug out in connection with the construction of the new road. In the northern part of the object, stage 1, the Swedish Road Administration (SRA) had a permission from the environmental authority to recover about 30 000 tonnes of tar contaminated asphalt by cold recycling with foamed bitumen (asphalt foam). In the southern part of the object, stage 2, about 70 000 tonnes of crushed asphalt pavement (asphalt granulate) were recycled without the addition of new binders. In both cases, the reclaimed asphalt was used as base course under the regular asphalt pavement. It replaced the conventional base course of crushed rock with the same thickness, 80 mm or 150 mm.

This report describes tests with recycling of crushed asphalt pavement (asphalt granules) as base course in stage 2. The road has been followed up during 2006-2010. During the construction phase compaction test was performed and the asphalt material was characterized by laboratory tests. The highway was opened to traffic in June 2006. Wearing course was laid in the summer of 2007.

I många länder där dubbdäck är förbjudna är trafikpoleringen ett stort problem och föreskrifter finns bland annat för stenmaterialets poleringsbenägenhet. I Sverige har dubbdäckstrafiken medfört att stenmaterialet på vintern ruggats upp varför låga friktionstal varit ovanliga på inslitna beläggningar. Val av allt slitstarkare stenmaterial, övergång till skelettasfalt samt skonsammare dubbar har dock markant reducerat dubbslitaget. På senare år har problem med låg våtfriktion konstaterats på slitstarka beläggningar under sommarhalvåret, framför allt i utsatta lägen och under eftersommaren och hösten. Mätningar har visat att friktionen snabbt kan reduceras om beläggningen är poleringsbenägen och halkrelaterade olyckor har rapporterats på polerade beläggningar.

Denna rapport är en kunskapsöversikt om polering, friktion och i viss mån textur och beläggningsslitage från dubbade fordon. Erfarenheter från friktionsmätningar främst i Stockholm och Göteborg har samlats in. En översyn ges över provningsmetoder och de krav som finns. Kompletterande friktionsmätningar har utförts med flera utrustningar (SAAB Friction Tester och BV12) där mäthastighet, tidpunkt på året, vattenmängd, typ av däck och ringtryck varierats. 

In many countries, where studded tyres are prohibited, the traffic polishing of the coarse aggregate in the wearing courses is a problem to a rather great extent. In those countries there are often regulations on the aggregate polishing value. In Sweden, where the use of studded tyres is extensive, the micro texture of the aggregate in the surface of the wearing courses increases during the winter season. Therefore, there have been few problems with low wet friction levels in Sweden. However, the increased use of wear resistant aggregates and stone mastic asphalt together with lightweight studs has led to a reduced amount of wear. During later years, a problem with low friction levels has been noticed in wear resistant surface courses during late summer and fall, especially at high trafficked roads with a complicated geometry. Measurements have shown that the friction level can be reduced rather quickly on surfaces with aggregates that are disposed for polishing and low wet friction related accidents have been reported. This report is a knowledge survey covering polishing, friction and to some extent surface texture and wear caused by studded tyres. Experiences from friction measurements mainly in Stockholm and Gothenburg have been compiled in this report. A review of testing methods and existing requirements is also presented in the report. Friction measurements have been carried out with two friction measurement equipments, SAAB Friction Tester and BV12, where the measuring speed, time of the year, the amount of water film thickness, the type of tyre and tyre pressure have been varied.

The report includes a literature study concerning steel slag as aggregate for asphalt mixtures. Environmental aspects and relevant test methods for use of steel slag have been highlighted in this work. A study tour has been made to south-west Götaland, Sweden, and to Denmark, where steel slag has been used for bituminous pavements for many years. Furthermore, test sections performed later at Dalarna are presented, too. In connection with steel production slag is produced as a by-product. Steel slag is used in many countries as bound or unbound layers in road construction. This report deals with slag from steel production in Smedjebacken, so called EAF slag (Electric Arc Furnace slag, sometimes called LB slag) used as aggregate in bituminous pavements. There are positive experiences from Halmstad and Laholm where EAF slag has been used as wear course on densely trafficked roads and streets since the beginning of 1990s. In Denmark, EAF slag from, for instance, steel production in Smedjebacken is frequently used in roundabouts and on densely trafficked roads and streets. The slag from Smedjebacken has good mechanical properties. The slag becomes, after crushing in several stages, cubical, but retains at the same time its rough surface by way of porosity. This gives the bituminous pavement very good stability. As the slag contains a suitable amount of unbound lime (<0,5 %) the durability against water is very good. In order to eliminate the risk of swelling, the slag is stored outdoors for about one year.

The interest in recycling of asphalt has increased a lot under the 1990s. In order to meet this interest a test of warm asphalt recycling in an asphalt plant was carried out in 1997. Recycled asphalt from Road 40 was mixed with newly-produced binder layer material of the type ABb 22. The test road was opened for traffic in the autumn of 1997. The test sections consist of both slow and high speed lanes (K1 and K2) on a motorway. The test road consists of totally six sections, four with pavement including granules (reclaimed asphalt pavement, RAP) and two reference sections with virgin asphalt mixture. The test sections contain 0, 20 and 40 per cent RAP, respectively. The binder is of bitumen, 70/100 in K1, and 160/220 in K2. In the base course (AG) layer, 40 per cent of RAP was mixed. The binder layer was trafficked the autumn of 1997 and the spring of 1998 till it was paved with a wearing course in the summer of 1998. The test road has been followed up in 1997, 1998, 1999, 2000 and 2007 by bore cores, rut depth, evenness and damages. The bore cores have been investigated by void content, indirect tensile strength, stiffness modulus, stability and durability (water sensitivity) as well as by ageing of extracted binder. In connection with the production of the materials both the asphalt material and the recycled asphalt were controlled. In connection with the paving it was observed that the mixes with RAP were more elastic and easier to pack than the reference sections where virgin asphalt material was used.

Coal tar was used in Sweden for the production of asphalt and for the drenching of stabilization gravel until 1973. The tar has high concentrations of polycyclic aromatic hydrocarbons (PAH), some of which may be strongly carcinogenic. Approximately 20 million tonnes of tar-containing asphalt is present in the public roads in Sweden. Used asphalt from rebuilding can be classified as hazardous waste according to the Swedish Waste Act. The cost of treating the material removed as hazardous waste can be very high due to the large amount that has to be treated, and the total environmental benefit is unclear. The transport of used asphalt to landfill or combustion will affect other environmental targets. The present project, based on three case studies of road projects in Sweden, evaluates the consequences of four scenarios for handling the material: reuse, landfill, biological treatment, and incineration. The results show that reuse of the coal tar-containing materials in new road construction is the most favorable alternative in terms of cost, material use, land use, energy consumption, and air emissions.

Olika varianter av indränkt makadam, IM, används till förstärknings-, bär- och slitlagerbeläggningar på låg-, medel- och högtrafikerade vägar. Beläggningstypen anses vara mycket kostnadseffektiv och är dessutom resurssnål. Stenmaterialet behöver inte värmas upp och tillverkningen sker på vägen med lokala material, vilket minimerar energiåtgång och materialtransporter. Beläggningstypen har också en mycket god flexibilitet, vilket gör den särskilt lämplig på vägar med sämre undergrundsförhållanden, dålig bärighet och ojämna tjällyftningar.

Ökat intresse för indränkt makadam (IM) har initierat en kunskapsöversikt inom detta område. Studien skall bl. a ligga till grund för ett FoU-program men även peka på brister och utvecklingsmöjligheter för tekniken.

VTI has during a considerable time of years monitored the wear from studded tyres through full-scale tests and control sections. During the winter 2006-2007, measurements of the wear were carried out at several control sections in the region of Stockholm. The aim of these measurements was to study: - the amount of wear caused by studded tyres on urban streets in Stockholm, - the amount of wear caused by studded tyres on express ways outside Stockholm, - the number of private cars using studded tyres, - the relevance of the wear prediction model when used for urban streets.The result of the study shows that the wear of the asphalt wearing courses on the express ways around Stockholm has increased during the last few years even after compensation with respect to the increased amount of traffic. This means that every vehicle equipped with studded tyres wears away more material from the surface of the asphalt wearing course. One reason for this is that less wearing resistant aggregates have been used in the wearing courses on the express ways around Stockholm the last few years. Together with an increased amount of traffic it results in deeper wearing ruts compared with the winters in the beginning of this century. The rut depth caused by the traffic with studded tyres was 2-3 mm in the winter 2006/2007.

Prediction models that describe changes in the condition of various portions of a road structure constitute valuable tools for evaluating service life and economics of a road structure or of a surfacing measure. Prediction models also constitute the core of planning systems - Pavement Management Systems - which are based on changes in the condition of various road structures and asphalt layers depending on traffic and time. The prediction model discussed in this report describes the magnitude of wear of pavement and of rut formation created by vehicles with studded tyres. The model is based on the results and experiences gathered during the last twenty years of work at VTI (the Swedish National Road and Transport Research Institute) with the objective of developing and evaluating the wear resistance of asphalt wearing courses. The objective was to develop a computer based prediction model for the rut formation that is caused by wear from studded tires. The model should both provide a prediction of the wear resistance of the wearing course based on data regarding the type of wearing course, the properties of component materials, and a model of the rut profile based on data for type of road, amount traffic, etc. In the first stage, the model was limited to include wearing courses of type ABT (dense-graded asphalt concrete) and ABS (stone matrix asphalt). However, these two types of wearing courses are by far the most common road surfaces on medium to high trafficked roads in Sweden. During the following years the wear model has been validated and calibrated a couple of times. A new updated version of the model was developed during year 2006. In this latest version a few new road types have been added to the model, 2+1 roads and roads with extremely narrow lanes. In the new version it is also possible to use Prall data as input to the model. Prall data is the output from a laboratory wear testing device.