Article by Robert Weibold

etra seminar 2015Last week we had the pleasure to attend the seminar “flex & the city”: Rubberised Asphalt and Recycled Tyre Products and Applications for Roads and Urban Furniture, which took place in Treviso (Italy) on October 22nd. The seminar was organized by ETRA (the European Tyre Recycling Association) in co-operation with ANTEL (the National Association of Local Authority Technicians) and ARGO (the Italian Recyclers Assoiation). 

etra seminar 2015.2The seminar was designed to illustrate the many uses of recycled tyre rubber in road and urban furniture applications, highlighting the flexibility of use and the high performance of the materials. The programme brought together representatives from the tyre recycling sector with the operators and developers, as well as the technicians involved in public works, as speakers and discussants. The audience included developers, implementers, engineers and technicians in the public and private sectors who design and install public works, as well as ETRA and ARGO members who produce and provide the raw materials for the projects.

After an introduction by Dr. Valerie Shulman (Secretary General of ETRA) about what tyre is, relevant aspects and norms to the tyre recycling sector, Bruno Marabotto from Isoleco presented his work on using tyre derived textile for the production of insulation panels for the construction industry. He stressed that the panels are particularly sound insulating and exceeding norms by almost 10%. An additional benefit, which he outlined, is heat insulation.

Dr. Maurizio Guadagnini from Sheffield University presented then his work on steel fibres (EU funded ECOLANE project, 2005-2008), and tyre textile fibre, as well as rubber powder in concrete applications (EU funded ANAGENNISI project, 2014-2017). He explained that in all of his work the key is to find a balance between deformation levels versus mechanical properties for various applications.

Eng. Andrés Macho, who represents the Environmental Ministry of Spain, presented interesting but disappointing numbers on usage of rubber powder in asphalt. There was a peak of 4,163 tons used in 2010, before and after the average was just 1,500 tons per year.

Raffaele Filippi, representing the road authority of Veneto province, presented his experiences on using rubber powder in various road projects. They have noted major reductions in vibration which protects nearby buildings, less noise and a longer road life. Initially there has been a problem with the smell of the rubber during the construction process. Once the “luke warm technique” was applied the problem disappeared.

The same findings were shared by Ing. Marco Benso, from Torino province, and Ing. Christiano Rebecchi, from Cremona province, who added that the roads show better grip behaviour.

Dr. Davide Lo Presti from Nottingham University shared his extensive experience in using rubber powder in asphalt applications by applying the “wet process”. He stressed particularly one reason for crumb rubber modifiers (CRM) not being more widely used, which is a similar one as for standard Polymer Modified Bitumen. Both products need agitated storage tanks which adds cost and technological upgrading compared to conventional ones used for standard asphalt. The issue with standard asphalt rubber is that the storage temperature tends to separate (usually sink) CRM so quickly that they are not good enough. If the CRM separates from the bitumen matrix, the binder loses its modification and the plants need to clean the tanks continuously but even worse they can have great damage in the pipes. With an analogy, if you serve a tea with sugar directly from the pot, you want to make sure that tea has got the sugar. If the sugar stays in the pot, you won’t enjoy your sweet tea and you will also need to wash the pot for further use. Despite the issue of agitated storage tanks Dr. Presti confirmed the remarks by Mr. Macho, Mr. Filippi and Rebecchi about the many positive effects of rubber powder in asphalt applications.

It is actually the opposite. Asphalt plants have the same issue with Polymer Modified Bitumen and they already have agitated storage tanks. The issue with standard asphalt rubber is that the storage temperature CRM tends to separate (usually sink) so quickly that they are not good enough. If the CRM separates from the bitumen matrix, the binder loses its modification and the plants need to clean the tanks continuously but even worst they can have great damage in the pipes. With an analogy, if you serve a tea with sugar directly from the pot, you want to make sure that Tea has got the sugar. If the sugar stays in the pot, you won’t enjoy your sweet tea and you will also need to wash the pot for further use.

Finally Giorgio Macor from Bagigi presented his work on superficially modifying rubber powder and its benefits for using it in polymer modified bitumen. Bagigi is chemically bonding the asphalt and rubber powder instead of physically mixing the blend, which results in better compaction, higher performance, lower emission, lower viscosity, and increased stability.

Overall, flex & the city was a well organized event with plenty of interesting presentations!

We are looking forward to ETRA’s yearly conference in Brussels in March 2016.