Re-Road – Optimizing the Potential in Recycling of Asphalt In a former number of this magazine (Nordic No. 1, 2009) thereb was an appetizer concerning the start of a European project "Re- Road – End of Life Strategies of Asphalt Pavements" running from 2009–2012. The project consortium involves eighteen partners of which four originates from the Nordic countries. Apart from the VTI, which also holds the role of project coordinator through Björn Kalman, the Swedish Geotechnical Institute, Peab Asfalt AB and Danish Road Institute participate in the research project which is funded by the EU Commission under the 7th framework programme.
The technical part of the project is divided into five work packages: • WP1 Sampling and Characterization of Reclaimed Asphalt (RA) • WP2 Impact of RA quality and characteristics on mix design and performance of asphalt containing RA • WP3 Environmental performance of RA • WP4 RA processing and RA management at the mixing plant • WP5 Performance modelling of RA.
In the initial reference to Re-Road in this magazine we had just passed the "kickoff" meeting, but now the first interim reports to support the further activities of the project are in the tube for review and the last quality check before publication outside the consortium. As work package leader of WP4, I will here mention specifically an interim report in the format of a small survey which WP4 performed to provide background information of WP2.
The tasks for WP4 are closely related to practical application in the road sector, and the partners of that work package have good connections to asphalt producers and contractors. WP2 was involved in developing an optimum laboratory mixing procedure to obtain the best possible characterization of impact of reclaimed asphalt on mix design. As an initial starting point – apart from the European standard for laboratory mixing EN 12697-35 – WP2 was interested in the present experience for performing laboratory mixing – especially when reclaimed asphalt was introduced. By drawing on the industry contacts of the partners of WP4, a small survey was put together for practise of laboratory mixing to establish an appropriate mix design for materials including reclaimed asphalt. The deadline was rather tight as an initial sampling of practise was to be presented to WP2 12 May 2009 though the sampling was continued until October 2009 to harvest additional contributions.
The report contains more than 22 responses from six countries (Belgium, Denmark, Germany, Slovenia, Sweden and United Kingdom). The number of responses does not on the surface reveal the coverage in each country, but in general a major, if not a total market share, is represented by the responses, so the report gives a reasonable trend of the present state of the art.
The responses cannot be taken andsummarized over the total range as some points are dependent on type of plant (batch plant or drum mixer and how the reclaimed asphalt is introduced), the market
Reclaimed asphalt – slabs from utility works ready to be processed and re-used.
situation in which the company operates, availability to RA and local acceptance of RA in mixes – especially surface layers. But certain lessons can be learnt from the survey and 13 statements are highlighted in the report. A few of them will be mentioned here, yet it will be necessary to go through the responses to the questionnaire for a more thorough examination of the individual items. • Marshall mix design is still the predominant method of performing mix optimization. • Almost all companies use heated and predried reclaimed asphalt in laboratory mixing irrespective if they use cold feed addition of RA in the asphalt plant. • Almost all companies aim for a homogeneous mixed asphalt material in the laboratory even though it means longer mixing times in the laboratory than in the asphalt plant. • A few companies do not use laboratory mixing for mix design at all, but optimize mix design through full scale production based on experience and knowledge of the characteristics of the constituents. • Only a very few responses claim that their laboratory mixing procedure is linked closely to the conditions of the local asphalt plant. • In general, mixing temperatures – both in laboratory and in the plant – are selected based on binder viscosity or preselected from experience depending of the grade of binder.
