Reclaimed asphalt binders and mortars fatigue behaviour

Fatigue cracking is one of the most important failure mechanisms occurring in asphalt pavements, especially when mixtures incorporate considerable amount of rReclaimed asphalt pavement (RAP). In fact, aged binders contained in RAP generally make asphalt more brittle and specifically reduce fatigue resistance of the resulting asphalt mixtures. Binders and mortars play a key role in this phenomenon, considering fatigue cracking usually starts within these asphalt components. However, performance-related tests and specifications commonly regard binders and there are no sound methodologies allowing the use of mortars to predicting fatigue performance of asphalts containing RAP. For this reason, in this paper, fatigue resistance of extracted binders from high-RAP content mixtures and of RAP mortars (passing sieve with an opening size of 0.15 mm) were assessed and compared. Binders were extracted from asphalt mixtures manufactured with 30%, 60% RAP and rejuvenators. Mixtures recipes were then reproduced to manufacture mortars accordingly. Time sweep tests in stress-controlled mode were carried out on both materials (binders and mortars) and the resulting fatigue laws were compared. As a result, a strict correlation was obtained, leading to affirm fatigue-related properties of RAP mixture could be assessed by directly testing RAP mortars. This makes the recovery of RAP binders unnecessary. Moreover, a relationship between the two fatigue laws versus the percentage of fine particles in the mortar was found. This latter relationship allows determining the fatigue law of mortars corresponding to any percentage of fine particles and therefore corresponding to any percentage of RAP

European National Road Authorities and Circular Economy: An Insight into Their Approaches

The pavement engineering industry, having realized the significance of the impacts that it imposes on the environment through the production, construction and management of its products and assets, has been driven towards a more sustainable and circular way of operating. This has partly been through asphalt recycling, which is an area that many road authorities have prioritized. However, not all the National Road Authorities (NRAs) and/or sector stakeholders seem to be adequately familiar with the Circular Economy (CE) concept. This paper attempts to assist the transition of NRAs to a more circular way of doing business, by analyzing the current situation of CE within national/regional authorities and NRAs. To do so, a questionnaire was sent to di erent NRAs and an online search was conducted to identify the ways that NRAs communicate their CE practices. Findings indicate that, although the majority of the NRAs are familiar with CE as a concept, not many actions have been taken so far towards its holistic implementation. Finally, there is a significant lack of CE expertise and communication within these bodies.European Union's Horizon 2020 Program under the Marie Curie-Sklodowska actions for research, technological development, and demonstration 721493CEDR Transnational Research Programm

Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation

Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these simulations. The overall prediction accuracy, when all the signals are considered, is between 4% and 8% for all materials. It can be concluded that material characterisation in lab as well as the selected models are well adapted to simulate actual loading state under a moving load, even for these non-conventional mixes. For temperatures lower than 25°C, elastic modelling appears to be sufficient for pavement structural design with the innovative materials tested here

Pavement life cycle management: Towards a sustainability assessment framework in Europe

Pavement Life Cycle Management is a 2-year international project aiming at supporting European National Road Authorities (NRAs) to introduce sustainability in their practices by providing training on Life Cycle techniques and a user-friendly package to support their widespread implementation. The first task in Pavement Life Cycle Management (PavementLCM) project is the creation of a Sustainability Assessment (SA) framework that complies with EN15643-5 and consequently include the three pillars of sustainability, use a life cycle approach and use quantifiable sustainability performance indicators. This paper presents the first steps towards the creation of the framework which includes the following steps: 1) review of the available Product Category Rules (PCRs) related to asphalt mixtures and pavement activities; 2) definition of the object of the assessment; 3) review and survey of NRAs practices of the main research efforts in Europe towards the definition of sustainability performance indicators

Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation

Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these simulations. The overall prediction accuracy, when all the signals are considered, is between 4% and 8% for all materials. It can be concluded that material characterisation in lab as well as the selected models are well adapted to simulate actual loading state under a moving load, even for these non-conventional mixes. For temperatures lower than 25°C, elastic modelling appears to be sufficient for pavement structural design with the innovative materials tested her

Effect of two novel bio-based rejuvenators on the performance of 50% RAP mixes - a statistical study on the complex modulus of asphalt binders and asphalt mixtures

An experimental study was conducted to evaluate the effectiveness of two bio-additives as rejuvenators on the properties of asphalt mixtures containing 50% RAP and their binder constituents containing 37% RAP binder. Before mixing, the rejuvenators were blended with fresh bitumen and the extracted and recovered RAP bitumen, and changes in the rheological properties of the binders were assessed using performance grading (PG) criteria. The results showed that both rejuvenators could improve the low-temperature performance of the aged RAP binder and restore its low-temperature properties. Master curves for the unaged, RTFO-aged, and PAV aged blends were constructed using both the Christensen-Anderson-Marasteanu (CAM) model and the Sigmoidal models. A comparative statistical analysis conducted on the models indicated no significant difference between the measured and predicted complex modulus values at any aging conditions. The pairwise statistical comparison between the two models showed that at unaged conditions, they can perfectly overlap as the p-values were greater than the level of significance. However, for the PAV-aged binders, this behaviour appears to weaken due to the brittle behaviour of the binders. Further statistical analyses revealed no significant differences between the two models at unaged conditions, however, as the binders where subjected to aging, significant differences between the two models began to appear. Mixing was performed in two locations: lab and plant, while compaction was performed only in the lab. After mixing and compaction, mixtures were evaluated for their stiffness characteristics through dynamic modulus testing. Compared to the control mixture, rejuvenated mixtures showed lower dynamic modulus values specially at high temperatures. A statistical comparison between the lab-produced, lab-compacted mixtures and plant-produced, lab compacted mixtures showed that both the rejuvenation and the location of mixing were significant factors in the stiffness measurements

Uncertainty analysis of life cycle assessment of asphalt surfacings

The Life Cycle Assessment (LCA) of asphalt pavements are associated with significant uncertainty resulting from variability in the quantity and impact of individual components, the quality of data for each component, and variability of asphalt durability. This study presents a framework to quantify and incorporate the uncertainty of LCA and asphalt durability data into LCA of asphalt surfacings. The suggested framework includes: estimating the uncertainty of asphalt production processes by the pedigree matrix method, conducting a deterministic LCA, applying Monte Carlo Simulation (MCS) to estimate the probability density functions (PDFs) of the considered impacts using the uncertainty data, deterministic solution, and asphalt durability. This framework was applied to six asphalt mixtures; the results show that there is significant uncertainty in the processes that contribute to the environmental impacts. They also showed that considering asphalt durability and its uncertainty is critical and can significantly change the results and interpretation of LCA