News

The Re-Road final conference, held on Tuesday 13th November 2012 at the THON hotel City Centre in Brussels, attracted over 75 people from the project member institutes, industry and policy partners and other key stakeholders.

 Moderated by FEHRL Secretary General, Steve Phillips, the conference gave a comprehensive overview of the different areas covered by the project, divided up into the following sessions:

• Introduction and setting the scene
• Dismantling and Handling Strategies
• Sampling and Characterisation
• Mix Design
• Environmental Criteria
• Cost effective recycling

 Introduction and setting the scene

Project Coordinator Björn Kalman of VTI opened the conference by giving key details about the project. He reminded the audience that some 18 partners were involved in Re-Road, including 11 research institutes, four academic institutions, two associations and one contractor. Today one third of reclaimed asphalt ends up as unbound material where neither the binder nor the special aggregates used for surface layers make a difference. These wasted materials have to be replaced with new material for asphalt production. The situation differs greatly across Europe as there are some examples of countries where almost everything is reused, but also examples of where almost everything ends up in unbound layers. However, there are still questions about the quality of asphalt produced with recycled material and the project itself covers all areas of recycling.
Following this introduction, Egbert Beuving of the European Asphalt Pavement Association (EAPA) gave an overview of the current status of asphalt re-use and recycling in Europe. The re-use of recycled asphalt (RA) started a long time ago in the 1950s, was spurred on by the energy crisis in 1973-1974 due to bitumen savings and started on a 100% basis in 1976 in the Netherlands. The subject has been dealt with since many years and several techniques are now available, including batch mixing plant (hot) reuse, drum mixer plant (hot) reuse, plant with parallel drum (hot) reuse and cold mix recycling/reuse. In Europe more than 300 million tonnes of asphalt are produced at more than 4,000 stationary asphalt plants and 750 mobile plants. He stressed that asphalt is 100% re-usable/recyclable, recycling is important, and that road authorities can stimulate recycling as they are the owner of the RAP and are also responsible for it. Legislation can also stimulate recycling, as has been seen in the Netherlands.
Following this comprehensive overview, Konrad Mollenhauer of TU Braunschweig gave a presentation on the related DIRECT-MAT project (also see http://direct-mat.fehrl.org), which aimed to collect knowledge to improve recycling of many materials in roads including asphalt concrete.. He outlined the several research needs that were identified that were also relevant to Re-Road. The conference then continued with five technical sessions covering presentations on each of the technical areas which related closely to the project’s five technical Work Packages.
Dismantling and Handling Strategies Thomas Gabet of IFSTTAR kicked off this session by explaining about the Production of Reclaimed Asphalt by milling operations and the influence of milling parameters influenced the properties of the reclaimed material.
He was followed by Erik Nielsen of DRD who outlined the Handling and Introduction to the Mixing Process. He spoke about RA processing and RA management at the mixing plant, highlighting the steps in recycling RA, as well as limitations and potential problems. He gave the details of a number of case studies and summarised that high levels of recycling can be achieved but a lower percentage is also advantageous, as long as down grading is avoided.
Sampling and Characterisation Thomas Gabet of IFSTTAR again took the lead in this session and gave details on a study on Sampling of Reclaimed Asphalt. A sampling process should be adapted to the origin of stockpile and a level of recycling. He showed that a simplified sampling procedure with roof-shaped piles and a shovel was a good alternative to the traditional splitting method. He was followed by his colleague Virginie Mouillet of IFSTTAR who presented the characterisation of RA. This study aimed to develop suitable extraction and recovery methods for RA with PmB, propose testing procedures for characterisation of the binder of RA. She concluded the importance of the nature of the RA binder and the necessity of collecting data to define the threshold values for the binder properties.
Mix Design Erik Nielsen of DRD outlined the details of a Survey on Laboratory Mixing Practices. Countries responding to the questionnaire highlighted the difference in everyday laboratory mix design. Some producers do not even use laboratory mixing at all. The results showed that laboratory mixing is seldom adjusted to mimic precise conditions at the asphalt plant. Following this, Konrad Mollenhauer of TU Braunschweig talked about “Laboratory Aging Procedure to Evaluate RA Compatibility and Multiple Recycling”, which compared different ageing procedures and showed that it was possible to restore the initial properties of polymer modified asphalt even after the material had been aged and recycled three times with a mixing ratio of 1:1 (RA to new material). Next, Joelle De Visscher of BRRC talked about the Impact of RA on Asphalt Mix Design and Laboratory Performance on the mix quality and the mix performance test results. A number of different laboratory mixing procedures are used in Europe. The study concluded that the differences between the tested procedures were not significant compared to precision of the tests methods used to characterise asphalt materials.
Environmental Criteria This session included the following presentations: Environmental Characterisation of RA – Waterborne Emissions – Anja Enell, SGI. A comparison between different leaching techniques and results from ecotoxicity tests on leachates is presented. Risk Assessment – Waterborne Emissions – Ciaran McNally, UCD. The risk assessment was done with leaching data and a sophisticated statistical modelling approach. Field validation on leaching from a stockpile of RA showed that there could be potentially high leaching associated with RA in unbound state. Environmental Characterisation of RA – Airborne Emissions – Vincent Gaudefroy, IFSTTAR. An ingenious procedure to study fume emissions that occurs in the asphalt plant and during laying was presented. Risk Assessment – Airborne Emissions – Ola Wik, SGI. The results from the fume generator, calibrated with literature data on emissions at production sites made it possible to make a risk assessment of airborne emissions. One conclusion of the study was that RA does not change total emission but quality of fumes. Life Cycle Assessment – Matthew Wayman, TRL. The goals for the LCA study was to determine the most appropriate material management strategy for RA and at the micro level, identify product level parameters that have a significant impact on the product’s environmental performance. Some of the conclusions were: Recycling asphalt to bound courses should be maximised Recycling should be prioritised over other environmental initiatives (e.g. warm mixing) since it yields greater benefits Durability is potentially very significant and preservation of the road surface should be considered alongside any environmental initiative
Cost effective recycling This session aimed at concluding all the previous session and outlining the next steps. Ian Carswell of TRL gave an overview entitled Field Performance of Surface Asphalt Courses Containing RA, which gave the following recommendations for implementation: Quantities of up to 10% could be added on a routine basis provided RA stockpiles separate surfacing materials from other layers. Higher quantities can be added on a scheme specific basis where the existing surfacing is of a consistent nature and the recycling can be undertaken with minimum amount of processing and testing. In situ recycling can extend the life of the existing surface course and the treatment can be repeated. Comparable performance can be achieved, but good quality control is needed for in situ recycling to ensure the right amount of additives and mixing occurs (and that the road has sufficient bearing capacity).
Performance Modelling Finally, Sabine Werkmeister & Markus Oeser of Techical University Dresden (TUD) outlined the Performance Modelling work carried out. They highlighted that they aimed to model the performance of RA and to study the pavement life as well as the sensitivity to damage by developing a numerical tool that can be used to design pavements incorporating RA.

Click here to take a look at all the presentations given during the event and the photos of the speakers and participants. A breakdown of statistics of participants per country is also included.