The conventional pavement design approach considers various parameters for the optimization of pavements for the prevailing traffic and environmental conditions. Demands related to technological developments, climate adaptation and infrastructure resilience are expected to influence the way pavements are designed and constructed. For this, better and improved flexible pavement design tools are required. ERAPave performance prediction (PP) which is a mechanistic-empirical (M-E) pavement design tool is currently under development with the goal of addressing the several challenges facing the pavement industry. This paper calibrates the permanent deformation prediction approach in ERAPave PP using pavement performance data from actual field pavements. As traffic volume is observed to have a significant influence on predicted results, separate calibration was performed for medium-to-high-volume and low-volume traffic categories. A global calibration factor is used for this purpose, significantly improving the accuracy of the prediction for both categories. Prediction accuracy can be improved further through the consideration of observed rut depth variability.  

The article investigates the chemical and rheological properties of bituminous binders extended with tall oil pitch (TOP), a bio-oil by-product from the pulp and paper industry. Bio-extended binders were formulated to incorporate different percentages of TOP, reaching the target penetration grades. Comprehensive chemical analyses, including Fourier-transform infrared FTIR spectroscopy and SARA (saturates, aromatics, resins, and asphaltenes) analysis by thin-layer chromatography with flame ionisation detection (TLC-FID), were conducted to investigate the compositional changes induced by TOP addition. Laboratory ageing of the binders was carried out. Rheological characterisation was performed using dynamic shear rheometer (DSR) to assess the impact on viscoelastic behaviour. The results indicate that TOP-extended bituminous binders exhibit distinct chemical signatures from bitumen, with notable differences in functional groups and SARA fractions. Furthermore, the incorporation of TOP changes the viscoelastic behaviour of binder. The specific impact and its extent seem to depend on the temperature and frequency range as well as the content of TOP in the binder. These findings are expected to contribute to the development of more sustainable asphalt pavements, highlighting the potential of TOP as a viable extender for bituminous binders. 

Design or failure criteria are an integral part of any pavement design procedure. They represent the allowable thresholds beyond which a pavement is no longer expected to effectively perform its intended functions. It is crucial to establish appropriate design criteria for pavement failure modes, as these criteria govern long-term technical, functional, economic and safety performance.

This report aims to establish design criteria for the failure modes incorporated in ERAPave PP (Elastic Response Analysis of PAVEments – Performance Prediction). This is achieved by combining a qualitative literature survey with a quantitative methodology that systematically assesses the performance, maintenance and rehabilitation (M&R) intervention histories of Swedish sections. The literature survey, which aimed to identify existing challenges and experiences, was conducted with a focus on pavement design methods, distresses and design criteria. In the quantitative study, annual distress measurements and M&R intervention timings were evaluated and modelled using various mathematical functions to establish representative average accumulation rates. 

The findings have shown that the selection of pavement design criteria requires the consideration of multiple factors, including technical, economic, safety and user expectations. In addition, the subjective nature of these criteria and the use of multiple thresholds for the same distress have limited their application and impact. The quantitative study showed inconsistency in M&R interventions and high variability in measured distresses. Nevertheless, it is possible to establish design criteria for the rutting and fatigue cracking failure modes in ERAPave PP, as well as for surface roughness, by modelling distress accumulation with a directly proportional linear function. It is important to further enhance estimated values using a multi-objective optimization function that considers all relevant factors and performance data from a wide range of pavements.  

Dimensionerings- eller felkriterier är en viktig del av varje verktyg för beläggningsdimensionering. De anger nivåer för skador, bortom vilka vägen inte längre förväntas fungera som den ska. Det är därför viktigt att fastställa lämpliga dimensioneringskriterier, eftersom dessa styr vägens tekniska, funktionella, ekonomiska och trafiksäkerhetsmässiga prestanda över tid.

Den här rapporten syftar till att ta fram dimensioneringskriterier för de skadetyper som ingår i ERAPave PP (Elastic Response Analysis of PAVEments – Performance Prediction). Arbetet bygger på en kombination av en kvalitativ litteraturstudie och en kvantitativ analys av prestanda och underhållsinsatser på svenska vägar. Litteraturstudien, som syftade till att fastställa aktuella utmaningar och erfarenheter, fokuserade på dimensioneringsmetoder, vanliga skador och tillhörande kriterier. I den kvantitativa delen analyserades årliga mätdata för skador samt tidpunkter för underhållsinsatser. Dessa data modellerades med olika matematiska funktioner för att ta fram representativa medelvärden för skadornas utveckling.  

Resultaten visar att valet av dimensioneringskriterier kräver hänsyn till flera faktorer, såsom tekniska, ekonomiska, säkerhetsmässiga och användarrelaterade behov. Kriteriernas subjektiva karaktär och användningen av flera gränsvärden för samma typ av skada har dock begränsat deras praktiska tillämpning. Studien visade också att underhållsinsatserna varit inkonsekventa och att skademätningarna uppvisat stor variation. Trots detta är det möjligt att fastställa kriterier för spårbildning och utmattningssprickor i ERAPave PP, samt för jämnhet, genom att modellera skadeutvecklingen med en direkt proportionell linjär funktion. Det är också viktigt att ytterligare förbättra de uppskattade värdena med hjälp av en multiobjektiv optimeringsfunktion som tar hänsyn till alla relevanta faktorer och prestandadata från många olika vägavsnitt.

This paper investigates the use of a plant-based bio-oil in bituminous binders as a partial replacement of petroleum-based bitumen for asphalt mixtures. Its effects on the ageing behaviour of bituminous binders and asphalt mixtures are studied. A total of six bituminous binders and their asphalt mixtures were prepared and analysed in laboratory, including three different binder formulations with varying percentages of bio-oil and their respective reference binders. Both the bituminous binders and asphalt mixtures were subjected to ageing protocols in laboratory. Softening point test, rheological and dynamic mechanical analyses were conducted to evaluate the changes in properties of the materials before and after ageing. The results indicate that the mechanical properties of aged binders and mixtures show very similar relationships as between the fresh materials, but the relationships after ageing are at changed levels due to the laboratory conditioning. This supports further studies to verify their functional performance in asphalt pavements.

here have been efforts in Sweden to convert and transform single carriageway roads into collision-free roads. The structural design and cost-effectiveness of these roads have mainly been performed using empirically derived pavement design methods. Currently, the Swedish Transport Administration (STA) is financing a project aimed at developing and implementing a mechanistic-empirical (M-E) pavement design approach for Swedish conditions. This is expected to impact long-term pavement performance and subsequently, the total life cycle cost (LCC) of projects. This paper examines, through design alternatives, the impact of a pavement design method on the total LCC of a road project. This is achieved by designing and analyzing an actual flexible pavement structure using two empirical pavement design methods and one M-E pavement design method. A life cycle cost analysis (LCCA) was employed to estimate future maintenance and rehabilitation (M&R) and road user costs, as well as initial construction and end-of-life costs. The cost estimation was conducted considering various combinations of interest and inflation rates that are expected to reflect current and future cost trends. The analyses have shown that the M-E pavement design approach delivered the least LCC, but this LCC is observed to vary considerably depending on the inflation and interest rates employed.

The probabilistic nature of pavement performance has led to the incorporation of reliability into pavement design procedures. A robust and comprehensive reliability analysis methodology that is coupled with accurately characterized inputs variability is necessary to derive the full benefit from a reliability analysis. This article evaluates pavement input variability impact on the design reliability and variability of rutting performance. It further studies systematically the variability of inputs such as layer modulus and thickness. This was achieved using inputs and performance data from several accelerated pavement testing (APT) structures and actual field sections. The variability of inputs such as layer modulus and thickness was established using measured structural and material properties. The ERAPave performance prediction tool was used to predict the rutting performance of the APT structures, whereas Monte Carlo simulation (MCS) was employed to generate the associated dispersion of predicted rut depth. A two-component reliability analysis methodology that uses the first-order reliability method (FORM) was used to estimate the reliability of the studied sections. A discrepancy in input variability is observed between the APT and field sections, whereas the MCS generated rut depth variability exhibits a wide variation. The FORM-based two component reliability analysis methodology has delivered reliability estimates that are reasonable and acceptable.

The carbon footprint of bio-extended bituminous binders aiming for pavement decarbonisation was quantified using a “cradle-to-pavement” life cycle assessment. The binders were extended with a plant-based bio-oil. By biogenic carbon accounting, the impact of biogenic carbon flow was analysed through different approaches. The results indicated that using the bio-oil as a bitumen extender slightly increases the fossil global warming potential (GWP) of asphalt pavements, by about 1%. Both the absolute GWP levels and the effect of polymer modification on average annual GWP are variable, depending on the input data. When the “−1/+1” approach is adopted, two of the three analysed cases showed a lower average annual GWP of asphalt pavements with polymer-modified bitumen while one analysed case showed almost unchanged average annual GWP. All analysed cases confirmed that the biogenic carbon accounting by the “−1/+X” approach reduces the total and average annual GWP significantly for the cases with biogenic components.

Bio-extended bituminous binders were formulated with tall oil pitch (TOP). Their corresponding asphalt mixtures were prepared. Various laboratory tests and full-scale accelerated pavement testing (APT) were conducted to evaluate their long-term performance. It is indicated that, at 25°C, the aged bio-extended 70/100 binder with 5% TOP had similar fatigue resistance to its reference. At 10°C, the aged bio-extended 160/220 binder with 21% TOP was marginally less resistant to fatigue at small strains. The asphalt mixture with bio-extended 160/220 binder had higher stiffness at 10°C and similar water sensitivity to its reference. Although the aged mixture with bio-extended binder showed higher strength to resist cracks at 5°C, it was more brittle, leading to faster crack propagation. After further moisture conditioning, the mixture became weaker but less brittle. The full-scale APT indicated that the section with bio-extended binders was more resistant to permanent deformation. Overall, the results suggest potential for larger-scale testing.  

Livscykelkostnadsanalys (LCCA) är en av metoderna som används för beslutsfattande inom beläggningsindustrin i Sverige. Metoden har implementerats på nätverks-, projekt- och komponentnivåför att utvärdera den totala livscykelkostnaden (LCC) för väginfrastruktur. Flera verktyg finns förnärvarande tillgängliga för att utvärdera de olika aspekterna av vägprojekt. Dessa verktyg är utvecklade för att analysera antingen hela livscykeln eller enskilda faser eller processer. Dessa verktyg använder flera förenklingar och antaganden för utvärdering av kostnadsposter, framtidabeläggningsprestanda och diskonteringsräntor.

Denna studie syftar till att fastställa den nuvarande kompetensen och praxisen gällande LCCA inom beläggningsindustrin i Sverige genom en litteraturöversikt. Undersökningen fokuserar på LCCA på projektnivå och omfattar de stora faserna och kostnadsposterna.

Av undersökningen framgår att det finns tillräcklig kompetens inom ämnesområdet, men den praktiska tillämpningen är begränsad. Metodikens flexibilitet, de långa analysperioderna och osäkerheten om framtida beläggningsprestanda och ekonomiska parametrar har identifierats som faktorer som begränsar implementeringen. Dessutom har faktorer som organisationsstruktur, avtalsarrangemang och brist på korrekta metoder för att uppskatta användarkostnader, samhällsnytta och restvärden observerats för att begränsa en bredare användning.

Studier som integrerar LCCA i Pavement Management Systems (PMS) krävs för att få bättre insikt om effekterna av viktiga beslut. Vidare behövs förbättrade metoder för att uppskatta trafikantkostnader, samhällsnytta, restvärde och diskonteringsräntor. Dessutom måste effekterna av riskanalys, datakvalitet, avtalsmekanismer och organisationsstruktur bedömas ordentligt.

Life cycle cost analysis (LCCA) is one of the methods used for decision-making in the paving industry in Sweden. The method has been implemented at network, project and component levels to evaluate the total life cycle cost (LCC) of road infrastructure. Several tools are currently available for evaluating the different aspects of road projects. These tools are developed with a certain scope and intention and can be applied to analyze either the whole life cycle or individual phases or processes. Furthermore, these tools employ several simplifications and assumptions for the evaluation of cost items, future pavement performance and discount rates.

This study aims, through a literature review, to establish the current competence and practices regarding road LCCA in Sweden. The survey focuses on project-level LCCA and encompasses the major phases and cost items.

It is evident from the survey that there is sufficient competence in the subject area, but practical application is limited. The flexibility of the methodology, the long-analysis period, and the uncertainty of future pavement performance and economic parameters have been identified as factors that limit its implementation. Furthermore, factors such as organizational structure, contractual arrangements and a lack of proper approaches to estimate user costs, societal benefits and residual values have been observed to limit wider adoption.

Studies that integrate LCCA into Pavement Management System (PMS) are required to gain better insight on the impacts of key decisions. Furthermore, improved methods are needed to estimate road user costs, societal benefits, residual value, and discount rates. Moreover, the impacts of risk analysis, data quality, contractual mechanisms and organization structure need to be properly assessed.

För att minska utsläppen av växthusgaser samt beroendet av fossila resurser har asfaltbranschen, inklusive olika företag, forskningsorganisationer och Trafikverket, undersökt användningen av bioasfalt i vägbeläggningar. Bioasfaltbeläggningar använder biobaserade bindemedel för att delvis ersätta traditionella fossilbaserade bitumen. Deras klimateffekter ska redovisas genom livscykelanalys (LCA), men det finns fortfarande utmaningar i LCA av bioasfaltbeläggningar. Vårt konferensbidrag diskuterar två aktuella utmaningar, nämligen redovisning av biogen koldioxid och osäkerhet i LCA.

För redovisning av biogen koldioxid använder EN 15804:2012+A2:2019/AC:2021 den så kallade ”-1/+1”- metoden. Med denna metod karakteriseras inkommande biogen koldioxid från de tidigare produktsystemen till det analyserade produktsystemet som -1 g CO2e/g CO2 medan utsläpp av biogen koldioxid samt utgående biogen koldioxid från det analyserade produktsystemet till de efterföljande produktsystemen karakteriseras som +1 g CO2e/g CO2. Metoden ger alltså en överblick över det hela biogena koldioxidflödet och leder till ett nettonollsaldo av biogen koldioxid.

Resultaten visar att olika metoder för redovisning av biogen koldioxid leder till olika värden på GWP (Global Warming Potential) av bioasfaltbeläggningar. Genom att använda ”-1/+1”-metoden för beläggningen med två asfaltlager som innehåller biobitumen, återgår det totala GWP-värdet till den samma nivån som det initiala fossil-GWP, vilket uppnår ett nettonollsaldo av biogen koldioxid. Användningen av den så kallade ”-1/+X”- metoden resulterade dock i en betydande minskning av GWP, där den totala GWP låg på cirka 50 % av det initiala fossil-GWP. Denna minskning beror på det biogena kol som beläggningen innehåller.

Vårt konferensbidrag visar att både metodval för redovisning av biogen koldioxid och osäkerhet i LCA kan påverka resultaten och slutsatsen av LCA för bioasfaltbeläggningar. Därför är det viktigt att standardisera metoden för redovisning av biogen koldioxid för bioasfaltbeläggningar. Dessutom är transparensen av indata också avgörande för att säkerställa tillförlitligheten av LCA-resultaten och slutsatsen. Att på bra sätt hantera dessa två utmaningar är betydelsefullt för beslutsfattande om implementering av bioasfaltbeläggningar.