Greentire Develops Asphalt Additive

Greentire

The Greentire-Activa project has devised a powder for end-of-life tyres.

Sustainable Asphalt Project by Greentire

It is an additive that wins in sustainability and traction, in a circular economy perspective. The project saw the collaboration of Greentire and Activa, led by the team of Engineer Francesco Santella, gave birth to a special additive for high-performance asphalts. Research started from an assumption: it has long been known, that it was possible to make high-performance asphalts containing rubber recovered from end-of-life tyres, but the common process took place with a procedure called "wet". A peculiar characteristic of the "wet" method is that the mixing between bitumen and rubber powder must be carried out at high temperature and conducted with the aid of special equipment.

The  alternative, "dry" process, involves the use of the powder in the form of an aggregate which integrates the traditional aggregate, adding it directly to the asphalt mixing plant, during the mixing phase of the bituminous conglomerate. The "dry" process creates a higher consumption of rubber, around ten times higher than the "wet" process. Nevertheless, the "dry" process is less successful in the application due to the need for careful preparation of the conglomerate, the adoption of specific laying and compaction conditions and a suitable and accurate formulation of the design granulometric curve.

Last year Greentire announced the start of a project with Activa, which involved engineer Santella and her team in the creation of a bitumen additive containing powder derived from ELTs. And after months of work the research ended positively, with the creation of a crosslinking additive capable of creating a bond between bitumen and ELT through the “dry” process, that is with the addition of the rubber powder directly to the mixer.

The possibility of having an additive capable of solving the mixing  problem is an advantage from many points of view and, above all, its lower production costs. The new generation additive is obtained with an innovative technological process and has unique characteristics, since it is not classified as dangerous for human health or the environment. The main action is to energetically lower the interfacial tension between bitumen and ELT; this action manifests itself with an effective ELT / bitumen bond and with a marked increase in the workability of the bituminous mixture.

As part of the research, the elastic and viscous behaviour of the asphalt created was also studied, ie the ability to withstand permanent deformations and fatigue failure, through a series of technical and scientific tests. In a comparison with traditional asphalts, it emerges that the bitumen made with the additive containing ELT has better physical, mechanical and rheological performances compared to the traditional bitumen. Greater flexibility at low temperatures, greater stiffness at high temperatures, greater resistance to loads and higher fatigue recovery.

But it is a particular component that makes it worthy of note. It is a project that fully embraces the cardinal principles of the circular economy, as highlighted by the president of Greentire, Roberto Bianco. “The research project with Activa best embodies what is one of the Greentire's mission, namely, to promote the market for the recovery of raw materials derived from ELTs, finding new commercial applications ". Bianco then adds: “Good research like this has allowed us to significantly expand the field of application of the powders from ELTs, in the name of the circular economy which must always be the main route to follow for us and for those who deal with material recovery and recycling.

"I can anticipate from now on that, shortly, we will be engaged again in a further research project that will originate from the results of the first project with Activa", concluded the president of Greentire.

About the author

Ewan has been editor of Retreading Business since 2006 and of Tyre & Rubber Recycling since the magazine was founded. During this period he has become an expert on the global tyre recycling sector. He has many years' experience as an automotive journalist including a period at Tyres & Accessories.

 

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