APD : Alternative Paving Materials - Design and Performance

Technical Committee APD

General Information

Deputy Chair: Dr Fan YIN
Activity starting in: 2023
Cluster F

Subject matter

The ideal implementation of a circular economy involves transforming products that have reached the end of their useful life into resources for the same or different applications [1]. As the awareness and focus on the sustainability of road infrastructure have grown over time, exploring the potential for utilizing recycled, marginal, and secondary materials in pavement has emerged as a crucial challenge in road engineering. This large amount of unused, un-recycled, and often disposed materials derived from a diverse spectrum of activities and industries and their valuable potential when incorporated into pavement materials was the basis for the RILEM technical committee TC 279-WMR on Valorisation of Waste and Secondary Materials for Roads. TC 279-WMR explored several aspects of marginal materials for pavement applications. These include the type of materials that could be used as additives, modifiers, and aggregates and their suitability for use by evaluating their rheological behavior, mechanical response, and environmental sustainability. Such a committee obtained remarkable participation with more than 100 members. It generated solid interest in relevant research topics, as demonstrated by five journal publications, such as Wang et al. [2], several conference presentations, and the recently published State-of-the-Art Report (STAR) [1].

Starting from this seminal work, the proposed technical committee Alternative Paving Materials - Design and Performance (APD), in parallel with the proposed TC Alternative Paving Materials – Sustainability (APS), will continue on the legacy of TC 279-WMR. Specifically, TC APD will work to advance research in design and performance aspects that were only initially explored in the former TC effort while shifting toward a more inclusive vision of waste and secondary materials to a broader concept of alternative paving materials (APMs) as originally part of the native design of road composites. While APMs might include diverse materials, the new TC will identify a limited number of targeted APMs with particular attention to bio-binders, recycled tire rubber, and recycled plastic as a replacement for conventional petroleum-based binders, natural aggregate, and polymeric additives. This choice is also strictly connected to the latter two materials investigated in the previous TC 279-WMR, leaving bio-binders as a new frontier within RILEM technical committees aside from the single effort of Task Group 3 of TC 264-RAP - Asphalt Pavement Recycling [3] that evaluated a bio-based asphalt recycling agent. While the former TC 279-WMR attempted to address the use of different materials globally, its nature was broad and exploratory, which could not provide recommendations on the design and performance at an advanced and robust level. Therefore, the new TC APD will concentrate on three key areas corresponding to three task groups to develop advanced solutions to this urgent research need (Figure 1):

Figure 1Graphical Concept of TC APD

  • Prepare a Literature Review: The current information on the design and performance of the APMs and paving composites containing APMs is fragmented. Therefore, a comprehensive review to support the activity of other task groups is needed. This work will serve as a basis for the conclusive publication of the TC effort either as a STAR or as a topical collection in Materials and Structures (M&S).
  • Address the Design and Performance of paving composites containing APMs, using a multi-scale approach looking at binders, intermediate scale (i.e., mastic/mortar/fine matrix), and with a target focus on mixtures. Hence, the main goal of this task group is to explore the best approach for adapting existing procedures currently used by technologists, such as blend design, performance-engineered mix design, manufacturing, testing, and modeling.
  • Evaluate the Field Performance of paving composites containing APMs. To the applicants' knowledge, such an aspect was never addressed in RILEM TCs from cluster F despite the strategic importance of verifying the behavior of paving materials in the field. In this sense, the reference national road authority and the access to existing testing sections and accelerated pavement testing facilities of the chair and co-chair of the proposed TC, respectively, offer a unique opportunity for exploring this essential aspect.

TC APD will work to impress a transformative shift in the culture prevailing within the road pavement sector. Identifying an urgent imperative to advance and extensively demonstrate solutions that transcend conventional bituminous materials, along with the promotion of widespread adoption, is of paramount importance. Realizing these objectives necessitates the integration of a global vision with pragmatic initial steps that embrace interdisciplinarity, thereby leading to solid recommendation outputs. For such a purpose, the coordinated work of the proposed new TCs APD and APS offers a unique opportunity to maximize research and practical, valuable outputs for engineers, practitioners, and authorities in this unfamiliar area of investigation. Therefore, TC APD represents an optimal international collaborative arena that can take a substantial and recognizable stride toward addressing critical aspects associated with an advanced performance-engineered design of paving composites natively conceived with alternative paving materials. Consequently, the new TC will embrace members beyond the traditional domains of civil engineering and materials science, as shown by the interdisciplinary roster of interested parties toward the end of this proposal.

Essential References                                                                                                              

  1. Cannone Falchetto A., Poulikakos L., Pasquini E., Wang D. Editors. Valorisation of Waste and Secondary Materials for Roads, State-of-the-Art Report of the RILEM TC 279-WMR. RILEM State of the Art Reports, volume 38, 2023.
  2. Wang D., Baliello A., Poulikakos L. D., Vasconcelos K., Kakar M. R., Giancontieri G., Pasquini E., Porot L., Tušar M., Riccardi C., Pasetto M., Lo Presti D., Cannone Falchetto A. (2022). Rheological properties of asphalt binder modified with waste polyethylene: An interlaboratory research from the RILEM TC WMR. Resour Conserv Recycl 186: 106564. https://doi.org/10.1016/j.resconrec.2022.106564
  3. Hugener M., Wang D., Cannone Falchetto A. et al. Recommendation of RILEM TC 264 RAP on the evaluation of asphalt recycling agents for hot mix asphalt. Mater Struct 55, 31 (2022). https://doi.org/10.1617/s11527-021-01837-0

Terms of reference

The TC will be active for 5 years (2024-2028) and is planned to be implemented with 3 work packages, as presented in Figure 2:

Figure 2Flow Chart on the organization of TC APD

  • WP1 – Coordination involves overseeing daily project management activities and engaging with partners, members, and industry stakeholders to foster constructive dialogues among participants. This WP encompasses tasks such as acquiring and managing materials, establishing a shared material database, organizing periodic meetings, and ensuring timely reporting. Particular attention will be devoted to the coordination and collaboration with the work of TC APS, proposed in parallel with TC APD and other ongoing TCs within RILEM Cluster F and other clusters beyond if an opportunity arises.
  • WP2 – The research encompasses the activity of the three Task Groups (TG) listed below and described in Section 4:

TG1 – Literature review and STAR

TG2 – Design and performance of paving composites containing APMs

TG3 – Field evaluation of paving composites containing APMs

  • WP3 – Communication focuses on establishing virtual platforms (i.e., Microsoft Teams) to facilitate internal collaborations among team members and fostering scientific dissemination through journal papers and technical conferences. Moreover, extensive public engagement will be conducted by creating an online information page (i.e., Google Sites) and/or social media pages (i.e., LinkedIn).

The leadership structure of the proposed Technical Committee (TC) comprises a Chair and Deputy Chair, who will oversee WP1 and WP3, respectively. WP2 will be executed with the support of the Task Groups (TGs) leaders. The selection of themes for each TG serves as a foundational step towards achieving the global vision outlined in Section 2 while also building upon activities initiated in the previous RILEM TC 279-WMR.

It is essential to highlight that although the TG structure draws from the previous TC's activity, the scope, objectives, and aims of the proposed TC APD markedly differ from the existing and most recent TCs in the domain of asphalt materials (e.g., TC 272-PIM, 278-CHA, 264-PAR, 280-CBE, and TC 295-FBB) as moving toward a more comprehensive vision of alternative paving materials. TG1 will mainly focus on bibliographical research; TG2 will be heavily based on interlaboratory activity (ILA) as the core TG of the TC APD; TG3 will combine bibliographical research, data mining, and, toward the end, possibly prepare a limited number of testing cells for short term field evaluation in selected countries and locations (U.S. and Finland as a start). The principal applicant of this proposal has successfully implemented ILA in TC 279-WMR [1] and TC 264-RAP [3]. Therefore, based on previous experience with TC 279-WMR and its large membership and participation, an estimated active involvement of 15 to 20 laboratories in the ILA is expected. Furthermore, participant laboratories are anticipated to represent diverse geographical locations, spanning all continents worldwide, as reported later in the proposal in the list of interested participants. They encompass more senior members, young (doctoral students and researchers), and new members, as in the case of the proposed deputy chairs, TG leaders, and the industry. Concerning the latter, the activity of TG2 and TG3 will be of high interest to the industry as they directly connect to the use of materials from diverse production processes at the source and with the performance of novel paving composites containing APMs at the end. These are highly relevant for materials and paving mixture producers and for the road authorities and departments of transportation for their performance. Substantial cooperation with the proposed parallel TC APS will be sought to maximize the ILA activates concerning material and possibly apply the design procedure to be developed in TC APD TG2 into the corresponding TG2 Recyclability of TC APS.

The proposed timeline of the TC activities is listed hereafter:

  • September 2023: Approval of the new TC by TAC
  • November 2023: Presentation of the new TC at the annual Cluster F meeting in Lyon, France
  • Spring 2024: Kick-off meeting, work program approval, and assignment of group leaders at NCAT, U.S.
  • Fall 2024: Annual meeting, discussion, and approval of work plan
  • Spring 2025: TG meetings, update of deliverables, and work plan
  • Fall 2025: Annual meeting, discussion of results, presentation of achievements
  • Spring 2026: TG meetings, data evaluation, presentations, papers
  • Fall 2026: Annual meeting, discussion of results, presentation of achievements
  • Spring 2027: TG meetings, data evaluation, presentations, papers
  • Fall 2027: Annual meeting, discussion of results, presentation of achievements
  • Spring 2028: TG meetings, data evaluation, presentations, papers
  • Fall 2028: Annual meeting, concluding remarks, final report, presentations of final results
  • Spring-Summer 2028: Final TCAPD Symposium in conjunction with TC APS and other RILEM TCs

Increased attendance and engagement will be supported through hybrid meetings (in-person and online). Along with the work schedule mentioned above, TC and TG leaders will actively promote and disseminate TC activities and output in various venues such as the European Asphalt Technology Association and Eurobitume, the Transportation Research Board – TRB and the Association of Asphalt Paving Technologists - AAPT meetings, and the ASCE Engineering Mechanics Institute – EMI, NRRA, in the United States, the Conference on Pavements in Southern Africa, the Ibero Latin American Asphalt Congress, and the Australian Flexible Pavement Association events.

Detailed working programme

Brief descriptions of each task group of the "Research" work package and their related activity are provided next. 

TG1: Literature Review and STAR

The objectives of this TG are to 1) prepare an up-to-date knowledge basis on the use of APMs internationally and 2) coordinate the preparation of the final summary document of the research effort either in the form of a traditional STAR manuscript or a topical collection of papers in M&S at the end of the activities of the proposed TC. For this purpose, TG1 will work on two main activities: a) preparing a comprehensive literature review addressing design techniques, blend, preparation and manufacturing, performance evaluation methods, and testing solutions for paving composites with and without APMs that could be considered in the development of TG2; b) together with this activity, TG1 will lead the preparation of the STAR / topical collection of papers, coordinating the contribution of TG2 and TG3. The decision on which publication means to select (STAR or papers collection) will be agreed upon among the participants to the TC.

Proposed Chair: Dr. Maria Chiara Cavalli – KTH, Sweden.

TG2: Design and performance of paving composites containing APMs

The objective of TG2 is to define a performance-engineered design method for paving composites containing APMs. The activity of this TG will benefit from the literature review of TG1 and the work conducted in TC 279-WMR from TG1 and TG2 on bituminous blends characterization and especially by TG3 on mixtures. As anticipated, selected candidate APMs of interest to this investigation are bio-binders, recycled tire rubber, and recycled plastic, where bio-binders represent an element of novelty compared to the previous TC 279-WMR. Therefore, aspects such as thermomechanical properties of the blends and composites, developing new approaches and methodologies for design, manufacturing, and testing the incorporation of APMs with a multi-scale approach are part of the present TG with an ultimate focus on the mixture level. The research activity of TG2 is expected to be beneficial for the corresponding work conducted in the TG2 Recyclability of TC APS, where the design aspect will be essential. Therefore, robust cooperation across the two proposed TCs is envisioned.

Proposed Chair: Dr. Salvatore Mangiafico, ENTPE – University of Lyon, France. 

TG3: Field evaluation of paving composites containing APMs

The objective of TG3 is to summarize the field performance of paving composites containing APMs already tested or in existing testing sites while possibly preparing a limited number of field cells with new paving composites containing APMs that will be designed using the method proposed by TG2.

The activity of this TG will be initially devoted to the literature review and data mining from different international sources such as past research, road authorities, and departments of transportation to generate more structured information on the currently available field performance of this family of materials. Artificial intelligence will be considered to determine macro trends if a large amount of data can be collected. In addition, by leveraging the available field data from roads already designed with APMs in the Nordics with short (3-4 years) repaving cycles and experimental test sections at well-established accelerated pavement testing facilities in the United States, TG3 will attempt to prepare a limited number of field-testing cells paved with composites containing APMs for short term monitoring with the opportunity for longer-term evaluation for follow-up TC RILEM activities.

Proposed Chair: Dr. Krishna Prapoorna, IIT Tirupati, India.

A co-chair for each Task Group was also identified. The co-leaders agreed to support the coordination effort and activities of the corresponding TG leaders and guarantee the continuity of the research work over the entire duration of the TC.

Technical environment

TC APD marks the initial step toward the independence of the paving industry on natural and fossil-based raw materials. Former TC 279-WMR participants and partners from the industry, road authorities, and research institutions have acknowledged the need for such a research effort with an approach that would eventually eliminate the discrimination between conventional, secondary, and alternative materials. The proposed TC APD will build upon the extensive and pioneering contributions of TC 279-WMR with the specific objective of advancing the research on design and performance related to the incorporation of APMs. The new TC APD emphasizes its distinctive and innovative aspects compared to TC 279-WMR, specifically:

  • No dedicated methodology for mix design was investigated during TC 279-WMR, making this task an essential step to maximize the performance of paving composites with APMs, identify tailored testing methods, define correct manufacturing conditions, assess the validity of existing modeling techniques, etc.
  • Field evaluation was not addressed in the predecessor TC. Therefore, the opportunity of structuring data currently available filed data and the possibility of preparing a limited number of test cells paved with composites containing APMs for short and, potentially, long-term (in a follow-up TC) evaluation is highly valuable.

The proposed TC will benefit from the research and output of former RILEM TCs, such as TC 237-SIB, 241-MCD, 272-PIM, 252-CMB, and 264-RAP, addressing fracture mechanics, testing methods, performance evaluation, chemo mechanics, and recycling. Furthermore, efforts will be made to foster a solid collaboration with TC APS proposed in parallel with TC APD and robust cooperation with the following ongoing TCs:

  • TC 295-FBB - Fingerprinting bituminous binders using physicochemical analysis concerning material fingerprinting and characterization (TG1 and TG2)
  • TC 308-PAR - Performance-based Asphalt Recycling, in terms of manufacturing procedures (TG4) mixture performance
  • TC 307-PPB - Physicochemical effects of polymers in bitumen for characterization (TG1).

At the same time, TC APD and TC APS will establish a sound foundation for potential follow-up technical committees that can rely on the TCs' output and deliverables, such as for the long-term monitoring of potential field testing cells.

The proposed TC aligns with RILEM's mission, as it seeks to advance the field of more sustainable material design for road infrastructure by developing novel methods, conducting international and multidisciplinary activities, including literature and interlaboratory studies open to new members, and disseminating its output in publications and recommendations. In addition, the proposed research area holds significant interest and relevance for the road industry while offering valuable guidance to agencies and industries using unfamiliar paving materials. Given its focus and objectives, the proposed TC is ideally suited to be categorized under Cluster F of RILEM.

TC APD will leverage existing partnerships and make meaningful contributions within the well-established international network. To expand its global platform, the TC will actively seek to include members from regions beyond Europe and establish solid national and international relationships with associations, such as FEHRL, PIARC, ISO, ISAP, AAPT, TRB, AAPA, NRRA, AASHTO, ASTM, NAPA, CEN, EAPA, ACI, and Eurobitume.

Expected achievements

  • Direct benefits of the TC:
    • A comprehensive review of the current performance-engineered design solution for paving materials.
    • Development of performance-engineered design procedures for paving composites containing APMs.
    • An organized set of information on the field performance of existing paving mixtures containing APMs.
    • Possible new testing cells designed with APMs paving composites.
    • A first approach to support state and national transportation agencies and authorities in the design process of paving composites designed with APMs.
  • Outcomes/products of TC:
    • Thematic issue/Papers in Materials and Structures on the activity of the TC/TGs.
    • RILEM recommendations on the performance-engineered design procedures for paving composites containing APMs and initial field performance evaluation.
    • Data set on the past and existing field experience with paving composites containing APMs
    • Short courses and web-based training modules to be used as educational and implementation tools by academia, industry, and highway agencies.
  • Organization of Events and Publication:
    • State-of-the-Art Report or topical collection of papers in M&S on the work of TC APD
    • Papers in M&S or RILEM Technical Letters on the activity of the TC/TGs.
    • Organization of an international workshop (possibly in the form of a summer or winter school) in coordination with TC APS
    • Recommendation(s) on the performance-engineered design procedures for paving composites containing APMs and field performance.
    • Organization of a major symposium towards the end of the TC.

Group of users

  • Academics, road authorities, departments of transportation, and standardization committees.
  • Equipment producers, testing laboratories, and track/field testing facilities.
  • Material producers and construction equipment manufacturers.
  • Professionals and practitioners.

Specific use of the results

The demand for incorporating APMs into paving composites has increased considerably over the years at the research and application level, as demonstrated by the TC 279-WMR research. While this goes toward the circularity of resources, it also requires a solid approach with scientific bases. The availability of natural and fossil-based resources is limited; therefore, the need for achieving performance in the laboratory and field with alternative solutions is urgent. Dedicated performance-engineered approaches are needed at the design and field evaluation levels to successfully incorporate APMs into paving composites for durable, long-lasting roads.

Scientific-wise, the impact of the TC will be significant as it will advance the understanding of the design and performance evaluation process, starting from the materials components of the paving composites natively prepared with APMs (bio-binders, recycled tire rubber, and recycled plastic) and their response: rheological behavior, fracture evolution, fatigue, and aging, deterioration, etc. These materials typically undergo downcycling, incineration, or landfilling, making their utilization in paving composites a potential source of positive environmental and economic impacts. The outcomes of this research will serve as a basis for enhancing national and international standards, facilitating the exchange of data and expertise among stakeholders. Moreover, the results will contribute to establishing a global reference point for further advancements in this field. The State-of-the-Art report, recommendations, and research papers produced by the TC will also serve as a valuable educational resource for young researchers and engineers, representing a significant asset for the next generation of leaders in this field.