Subject matter

The proposed RILEM technical committee will follow the previous TC 264-RAP to continue scholarly research and knowledge dissemination on the asphalt material recycling. Need for incorporating and developing performance-based tools (laboratory tests, pavement performance prediction models, life cycle assessment tools) have been recognized in the activities of previous RILEM TCs as well as by both academic and industrial stakeholders. The focus of the proposed committee will be on recycling of asphalt materials. Materials studied will include cold, hot, and warm bituminous mixtures for applications in pavement construction.  The main contribution of the committee activity will be in terms of developing laboratory methods, analysis methods and life-cycle assessment tools that incorporate performance measures and predictions to support recycling decisions. TC activities will enhance of the fundamental understanding on the interactions between recycled asphalt (RA) materials and new virgin materials in asphalt paving mixtures in context of the impacts of RA use on performance of pavements. Performance in for the proposed TC activities will be considered in terms of design service life, capacity to resist primary load related (such as fatigue cracking and rutting) and non-load related (such as moisture damage) distresses, maintenance costs and global warming potentials.

At present, there are significant efforts underway to develop and implement balanced mix design tools for bituminous mixtures that adopt performance related laboratory tests to support proportioning of mixture. There is a lack of consensus on the selection of laboratory tests as well as their thresholds. Further, use preliminary versions of balanced mix designs (BMD) have been developed for bituminous mixtures with lower RA contents and often without consideration of rejuvenating agents that are often used for mixtures with higher RA contents. The outcomes of the technical committee will have balance between fundamental developments and knowledge disseminations to aid in improved mixture design methods and use of life-cycle analysis tools.

The proposed TC will undertake four interlaboratory studies on topics of performance based cold recycled asphalt mixture design procedures, selection and dosage recommendations for asphalt recycling agents (binder additives), quantification of the degree of binder activation and blending between RA binder and new virgin asphalt binder added to mixes, and finally on optimizing the warm mix asphalt designs with RA on the basis of long-term performance. Further, TC will also undertake a comparative analysis of different product category rules (PCR) and environmental product declaration (EPD) development procedures on the basis of life cycle assessment. The outcome of these activities will be to develop a series of RILEM recommendations on new or improved lab procedures and on PCR and EPD development.

Terms of reference

The activities of the proposed TC will be conducted over the period of five years. In order to achieve the intended goals, the new TC will perform its activities within five task groups (TG): TG1 – Performance-based Evaluation of Cold Recycled Asphalt Mixtures; TG2 – Long Term Performance Evaluation of Warm Mixes with Recycling; TG3 – Degree of Binder Availability, TG4 – Mixture Performance-based Dosage Optimization of Asphalt Recycling Agents; and, TG5 – EPD and PCR for Asphalt Mixtures with RA and Recycling Agents. These topics have been chosen as extension of the activities that were initiated in the previous RILEM TC 264-RAP. Please note that while the TG structure is on the basis of the previous TC activity, the scope, aim and objectives of the proposed TC are significantly different than the current TCs in the field of asphalt materials (i.e. TC 272-PIM, 278-CHA, 279-WMR, 280-CBE and TC FBB).

TG1, TG2, TG3 and TG4 will each undertake an interlaboratory study. Materials for these will be overlapping, in other words, multiple labs will be able to use same set of materials for ILS of multiple TGs. This approach was successfully implemented in previous TC 264-RAP by the TC leaders.

A conservative estimate for the active participation in ILS by 15-20 labs is expected, once again on the basis of previous experience with TC 264-RAP. Geographically the participant labs are expected to be coming from all continents of the world (the distribution of proposed TG leaders indicates such geographical diversity).

Proposed timeline of TC activites is presented below:

• December 2021: Pre-launch meeting to solicit active members and to present the work plan to industrial partners for feedback was already held at the Université Gustave Eiffel in Marné la Vallée. Industrial members were invited to make presentations on research needs from practice perspective. The inputs of this meeting was used to refine the TC proposal workplan.
• March – April 2022: Official launch (kick-off) of TC (if TC is approved by TAC at RILEM Spring Convention in 2021): Plans for TC objectives and outcomes will be presented along with preliminary version of work plans for each TG. Active members for each TG will be identified and call will be made regarding common materials that will be evaluated by the TC.
• June 2022: Official Kick-off meeting and industry workshop will be held at the University of New Hampshire in United States
• September 2022: Workshop will be held in Costa Rica in conjunction with the International Society of Asphalt Pavements (ISAP) Conference. The objective here will be to increase participation from central and South America in TC and RILEM activities.
• October 2022: TC Annual Meeting in conjunction with the cluster F joint TC meetings. The TC meeting will be scheduled either before or after cluster F meetings that will take place in Palermo, Italy. At this meeting TG workplans will be finalized and materials for ILS will be identified.
• March or June 2023: Either In conjunction with RILEM spring convention or the European Asphalt Technology Association conference (in Warsaw, Poland), TC meeting will be organized. By this time all ILS materials should be shipped to participating labs.
• September/October 2023: TC Annual Meeting in conjunction with the cluster F joint TC meetings. Main purpose of this meeting will be getting updates from TGs on testing and analysis. It is expected that 50% of data collection is completed by this time.
• Summer 2024: TC Annual meeting and an industry workshop on asphalt recycling will be held in conjunction with the 2^nd RILEM International Symposium on Bituminous Materials (ISBM) will be held. At this point in time, 75% of the testing activities for the ILS are expected to be completed and the initial analysis on EPD and PCR development methods for TG5 is expected to be completed.
• September/October 2024: TC Annual Meeting in conjunction with the cluster F joint TC meetings. Main purpose of this meeting will be getting updates from TGs on testing and analysis. It is expected that 90% of data collection is completed by this time.
• March or June 2025: Either In conjunction with RILEM spring convention or the European Asphalt Technology Association conference (in Ancona, Italy), TC meeting will be organized. All TGs will be requested to present the findings from ILS and plans for developing RILEM recommendations and other TC outcomes.
• September/October 2025: TC Annual Meeting in conjunction with the cluster F joint TC meetings. Main purpose of this meeting will be to finalize the topics for RILEM recommendation development. An industry workshop will also be organized to present the recommendations from TC activities and to obtain feedback on their practicality.
• Summer 2026: TC meeting will be held to finalize and vote on various RILEM recommendations developed by various TGs. Also, a workshop will be held on presentation of the EPD and PCR development framework generated by TG5 activities.
• September/October 2026: Close-out meeting of TC for final approval of all TC outcomes (RILEM recommendations, M&S thematic issue). TC will also propose to make presentations at the 2026 RILEM week.
• March 2027: Official closure of TC at TAC meeting during RILEM spring convention.

In general, all TC meetings will be held in hybrid (in-person and online) formats to maximize attendance and participation. Further, in addition to above planned work plan, TC leaders will also actively disseminate TC activities and updates at other venues (Transportation Research Board meetings in United States, European Asphalt Technology Association, Eurobitume, Conference on Pavements in Southern Africa, Ibero Latin American Asphalt Congress, and Australian Flexible Pavement Association events).

Detailed working programme

Brief descriptions of each task group and their corresponding activity are provided next.

• Task Group 1 Performance based evaluation of cold recycled asphalt mixtures (TG leader: Prof. Alan Carter, ETS Montreal; TG Co-Leader: Dr. Andrea Grilli, Polytechnic University of Marche, Ancona, Italy): This TG will undertake interlaboratory studies to explore various laboratory performance test methods that can be used to assess in-service performances of cold recycled asphalt mixtures. The main objective of this effort will be to identify laboratory performance tests that are most suited for: (1) materials selection, (2) mix proportioning, and (3) used as input in mechanistic pavement design procedures.
• Task Group 2 Long Term Performance Evaluation of Warm Mixes with Recycling (TG leader: Prof. Maria Carmen Rubio, University of Granada; TG Co-Leader: Dr. Fernando Moreno, University of Granada): This task group will undertake interlaboratory studies to explore suitable laboratory aging protocols and laboratory testing methods to reliably predict in-service performances of warm-mixed asphalt mixtures with high amount of RA (>35%). Significant thrust for the activity will be assessing cracking performance of the pavements.
• Task Group 3 Degree of Binder Availability (TG Leader: Dr. Kamilla Vasconcelos, University of Sao Paulo; TG Co-Leader: Dr. Davide Lo Presti, University of Palermo): The main objective of this task group will be to identify or develop a method to quantify or account for binder availability from recycled asphalt materials that can be used to improve mix design procedures and specifications. There is still a need for assessing this property as an additional parameter within improved characterization of the RAP (Degree of Activity - DoA). However, since in any mix design processes, RA materials are blended with additive and/or admixtures, there is also the need to assess the available binder in the presence of recycling agents.
• Task Group 4 Mixture Performance-based Dosage Optimization of Asphalt Recycling Agents (TG Leader: Dr. Martin Hugener, EMPA; TG Co-Leader: Dr. Augusto Cannone-Falchetto, Aalto University): This TG will undertake interlaboratory-study with focus on identifying practical and reliable asphalt mixture performance testing procedures, preferably those that can be conducting during mix design process, that can be used to optimize the dosage of recycling agents in asphalt mixtures to maximize RA amounts with minimal performance penalties.
• Task Group 5 EPD and PCR for Asphalt Mixtures with RA and Recycling Agents (TG Leader: Prof. Amlan Mukherjee, Michigan Tech University; TG Co-Leader: Dr. Elisabeth Keijzer, TNO): This TG will involve owners, contractors, producers and researchers to make a direct connection between what information producers and contractors can provide to help owners support meaningful decisions that aid long-term sustainability based on "first cost" environmental impacts as well as long-term performance. Specifically, detailed literature reviews and surveys will be conducted to develop a work plan. Comparative evaluations will be conducted of various current systems for EPD and PCR development in context of asphalt mixtures with RA and recommendations will be developed to fulfil missing links and knowledge gaps in current LCA approaches that are used for PCR and EPD development.