Subject matter

Bituminous materials can have very different long term properties, depending on the one hand on the source they come from and on the other the refining process (mechanical process) they were extracted with. Yet most of the research towards enhanced properties of bituminous materials is split into separate efforts towards understanding its chemistry or its mechanics. Connecting these two research fields into a joined chemo-mechanical understanding could lead to major improvements in the material’s sustainability. This proposed RILEM committee will thus be focusing on developing a robust and fundamental understanding by focusing on connecting the chemistry of bitumen to its mechanics. Taking a chemo-mechanical approach in itself is not a new concept. Much can therefore be learned by studying the successful application of such an approach to other materials (e.g. concrete or biomedical materials) as well as from recent developments in the nano-scale material characterization from RILEM TC-231 NBM. Since the long term response of asphalt mixtures under varying environmental (i.e. moisture, UV and oxygen) and mechanical (i.e. traffic) loading is crucial, having a fundamental understanding of the combined chemo-mechanical properties can greatly enhance the material’s sustainability and functionality. Thus, in developing chemo-mechanical characterization techniques on the nano- and micro-scale, the material’s variability from crude-source to crude-source and its sensitivity to temperature and humidity need to be taken into consideration.

The new TC will build up on the knowledge gained by the TC 231 NBM concentrating on questions and new developments governed by the need for universally applicable and physically sound fundamental chemo-mechanical characterization and testing methods. Part of this effort will focus on the development of uniform specimen preparation procedures for a variety of bituminous materials from different sources and refineries at the nano- and micro-structural level. More specifically, the TC will be concerned with:

(i) Identifying chemo-mechanically coupled properties of selected bituminous materials (literature study, STAR),

(ii) Quantifying dominant parameters of the selected chemo-mechanical properties by following uniform experimental procedures (round robin)

(iii) Developing and testing the influence of specimen preparation techniques (round robin)

(iv) Recommending appropriate tools and techniques for the chemo-mechanical characterization (recommendations)

The chemo-mechanically coupled properties that will be investigated by the committee will be based on a literature survey of existing knowledge in the bituminous materials field as well as other building and non-building materials. The literature review will be documented in a State-of-The-Art-Report. After selecting properties and hypothesizing the appropriate chemo-mechanical processes, the TC will focus on identifying these via experimental procedures. For this the committee will perform a round-robin study focusing on specimen preparation and experimental results to refine the test protocol and set the boundary conditions. This will lead to detailed recommendations for improved and potentially new standards.

In order to help in developing such chemo-mechanical understanding of bituminous materials, a concentrated effort is needed by a RILEM Technical Committee. Given the complexity of the topic, to ensure that this new TC will be able to make significant advances, it is important that the TC focuses its efforts from the very beginning. To this end, it can build on some of the recent publications. In 2009 a first International Workshop on Chemo-Mechanics of Bituminous Materials was organized[Editor: N.Kringos, ISBN: 978-94-90284-04-6] in which the current state-of-the-art on the topic was summarized by international experts. Furthermore, in the recent RILEM TC on Nano-technology based bituminous materials (231-NBM) various findings related to chemo-mechanical couplings were made and documented in a State-of-the-Art report and papers. A mid-way TC Workshop was organized at EMPA in Switzerland in May 2010 in which the current findings of the TC were discussed and a common roadmap was laid out. One of the TC outputs was an extensive state-of-the-art survey of the available test methods for multi-scale characterization. The TC 231-NBM is hosting the international RILEM Symposium on Multi-Scale Modeling and Characterization of Infrastructure Materials in Stockholm, Sweden, June 2013. In this Symposium the TC231-NBM researchers as well as experts from all over the world on concrete, asphalt and geomaterials will present their current findings on multi-scale characterization and modeling. The Proceedings of this Symposium will also be used as a starting document of the new RILEM TC.

The TC will limit its work on bitumen and mastics (including fillers), based on a maximum of 5 different sources.

Terms of reference

The new TC will be active for 5 years (2013-2018). The TC will perform a combination of literature review, experimental workand test protocol descriptions. It will also start developing some theories that could results in new models in subsequent research efforts. The TC will be inaugurated at the RILEM Symposium on Multi-Scale Modeling and Characterization of Infrastructure Materials, to be held in Stockholm, Sweden in June 2013, where a wider audience will therefore be exposed to the intentions of the TC and have the opportunity to join in on the efforts. In addition, the current experts in the field will also be invited to participate in the TC through mailings and personal contacts. At the end of the TC in 2018, a Symposium is planned to report on the findings of the TC.

In order to achieve the goals outlined above, the new TC intends to perform its work within the following task groups (TG):

TG 1 Chemo-Mechanical Coupling Identification

This TG will focus on identifying and analyzing the dominant coupled chemo-mechanical properties of selected bituminous materials through a literature review (including chemo-mechanical research done in other materials). Its outcome will be the basis for the material and test selection in TG2. TG1 will start in 2013 and will develop its intermediate report after 6 months.In this, the general identification of the possible chemo-mechanical couplings will be given and recommendations will be made for the focus of TG2 and TG3. After these initial findings , TG1 will continue to further develop the background theories that would allow for future modeling and testing efforts. The results of this will be reported in 2014. TG1 will also give support toTG2 and TG3 with regard to the dominant parameters of the tests and sample preparations for the test. So although its duration will be from 2013 – 2017, most of its activities are expected to be in 2013-2015. TG1 will develop a comprehensive paper on its findings, expected in 2014-2015 and coordinate the relevant session(s) at the Symposium planned in 2018.

TG 2 Chemo-Mechanical Laboratory Characterization

This TG will be performing the experimental characterization of the coupled chemo-mechanical characteristics as identified byTG1. The outcome of this TG will be the selection, testing and recommendation of appropriate tools and techniques for thecoupled chemo-mechanical characterization of bituminous materials. TG2 will start its activities directly at the start of the TCin 2013. Since at this time the results of TG1 are not yet available, it will first spend 6 months on reviewing the available equipment for the possible chemo-mechanical characterization. It will do this, partly, based on the equipment survey done by TC -231 NBM. Beginning of 2014, when TG1’s report will be available, TG2 will combine its results and develop a roadmap for the relevant laboratory characterization methods. A round-robin is expected to start mid-2014. In mid-2015 a Workshop will be organized in which the mid-term results and challenges of TG2 will be presented to the other TC members (and other invited researchers). Based on the outcomes of this Workshop, in 2015 and 2016 the experiments will be completed. In 2017 the results of the performed experiments are expected. TG2 will develop recommendations on its findings, expected in 2017 and coordinate the relevant session(s) at the end Symposium in 2018.

TG 3 Environmental Susceptibility Investigation

Since this TC is focusing on connecting the chemistry of the bitumen to its mechanics, effect of the environment (e.g. ageing,moisture conditioning, freeze-thaw, UV) is highly important and will be investigated by TG3. The work from this TG will be done in parallel to TG 2, and will focus on inspecting and documenting the influence of specimen conditioning in relation to the history dependence of the materials. TG3 will start its activities in parallel to TG2, though its activities will intensify as soon as the actual experimental set-ups are selected by TG2. TG3 will critically evaluate the needed specimen conditioning in the selected tests from TG2. TG3 will take part in the Workshop in mid-2015, in which its mid-results and activities will be presented. In 2017 the results of the developed specimen conditioning evaluation are expected. TG3 will also develop a comprehensive paper on its findings and recommendations, expected in 2017 and coordinate the relevant session(s) at the end Symposium in 2018.

Detailed working programme

Spring 2013: Approval of new TC by TAC

June 2013: Kick-off meeting in Stockholm during the RILEM Symposium on Multi-Scale Modeling and Characterization of Infrastructure Materials. Approval of work program and assignment of group leaders.

September 2013: Meeting to discuss its plans with the other Asphalt Scientists in Chicago during the Annual Asphalt RILEM TC meeting.

During 2013: Individual meetings by TG’s, finalizing proposal of working plan, evaluation of other possible synergistic activities, identification of missing expertise/experts that could be affiliated with the TC.

Spring 2014: 1st Annual meeting of new TC for a discussion & approval of individual working plans, concepts and achievements, approval of draft workshop plan, evaluate date and place for the 1st Workshop, define scientific committee.

During 2014: Individual meetings by TG’s, finalizing proposal of working plan, preparation of workshop, evaluation of the synergistic activities in other material fields, plan workshop program, evaluate draft of TG1 paper.

Spring 2015: 1st Workshop of new TC: Bring together experts from the bituminous binder and mixture community and key experts from materials science, polymer science, and surface chemistry to define best candidate laboratory characterization techniques for binders and mixtures, along with optimal specimen preparation methods for chemo-mechanical characterization of bituminous materials.

During 2015: Individual meetings by TG’s; adjust individual work plan based on outcome from workshop (e.g. additional literature reviews, material distribution for testing, testing, first evaluations)

Spring 2015: 2nd Annual meeting of new TC: Discussion & approval of individual working plans, concepts and achievements, evaluate workshop; start planning 1st Int’l Symposium (1st announcement, call for papers)

During 2016: Individual meetings by TG’s; follow individual work plan (.e.g. data evaluation, draft reports, first presentations and draft papers); organizing 1st Int’l Symposium 2018.

Spring 2017: 3rd Annual meeting of new TC: Discussion of progress & achievements; planning and approval of presentations, reports and papers, evaluate & approval of individual working plans, concepts and achievements, finalize workshops; start planning 1st Int’l Symposium 2018 (acceptance of abstracts).

During 2017: Individual meetings by TG’s; follow individual work plan (e.g. data evaluation, draft reports, first presentations and draft papers discussions); organizing 1st Int’l Symposium 2018. 

Spring 2018: 4th Annual meeting of new TC: Discussion of progress & achievements; planning and approval of presentations, papers, recommendations and reports; organizing 1st Int’l Symposium 2018 (acceptance of papers).

Spring 2018: Int’l Symposium on Chemo-Mechanics of Bituminous Materials

During 2018: Individual meetings by TG’s (discussion on end reports).

Autumn 2018: 5th Annual meeting (Concluding); final report; presentation of the results during annual RILEM meeting.