Switzerland: asphalt regeneration explained by EMPA

The Federal Materials Testing and Research Laboratory reveals how road networks are improved in a circular economy...

asphalt regeneration: road construction sites open
Road construction sites open on a Swiss road artery (Photo: EMPA)

Recycle or not? Asphalt recycled and rebuilt into a new version of pavement? This is the dilemma that has been hovering lately along the road arteries of the Switzerland.

A country, according to the latest estimate for 2021 made by World Bank, of 8,703 million inhabitants, spread over an area of ​​41.285 square km, and with a global road artery 83.274 km long.

Of these, approximately 1.544 km are motorway. And this latest data is collected and published byFederal Statistical Office three years ago, in November 2020.

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asphalt regeneration: the "Co-Creating Circular Futures
The “Co-Creating Circular Futures” is a project to introduce children to the circular economy
(Photo: EMPA)

Circular economy and recycling: the strong local "belief".

Il Swiss country he believes a lot in the recycling policy, in the circular economy and in the advantages that the latter offers on the scale.

However, we must not overlook technical aspects, issues and problems when we have to talk about the construction, modification and renovation of a road pavement.

Which is why it is right to highlight all the advantages that would derive from the use of recycled asphalt.

However, it is equally important not to overlook some barriers, even small ones, that can still be encountered.

THEEMPA, the Federal Materials Testing and Research Laboratory, thanks to the arduous work of one of its researchers, Martins Zaumanis, recently carried out research whose results were handed down and explained by the author himself a few weeks ago.

It is necessary to start from a first relevant figure: there are approximately 750 thousand tons of old asphalt collected and thrown into landfills. Quantity that contributes to the formation of black and decidedly polluting mountains.

This poses enormous risks to our environment. Which is why, the svizzeria they decided they had to take action.

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asphalt regeneration
A mountain of old asphalt, thrown into landfill and waiting to be disposed of or recycled (Photo: EMPA)

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The Confederation and all Cantons they “sing” unanimously: “Yes to the clearing of these black mountains of asphalt, in favor of intense recycling and restoration work, without ifs and buts, of all the recycled asphalt on our roads”.

The consequences of this type of operation would be evident to everyone: first of all, a significant saving of money would be obtained on possible new road and motorway works.

Secondly, local citizens would travel on roads remade or modified thanks to already recycled materials and the addition of new materials.

The ad hoc solution to offer, thus, a sustainable mobility on better road surfaces and with a more resistant structure.

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asphalt regeneration
An open construction site for the resurfacing of road surfaces (Photo: Pixabay)

Regenerated asphalt: Martins Zaumanis' point

Do some doubts arise when it is necessary to understand how old and new materials can flow and coexist together?

The search forEMPA explains this in detail: asphalt is made up of a mixture of aggregate substances and bitumen which, sometimes, is modified with polymers.

This modification is made with the aim of having a decidedly resistant asphalt; resistance which is a vital requirement especially when talking about road networks with high vehicle traffic.

Going deeper into the processing phases in detail and starting from the quantity of asphalt recycled and to be regenerated (RAP), Martins Zaumanis he claims: "In the best case scenario, during the manufacturing process, the original aggregate remains intact and less dust is produced, the so-called filling material which, otherwise, would make it difficult to reuse the old asphalt."

During the field testing phases, different processing methods were tested with the aim of making it as easy as possible to reuse old asphalt, which is usually more difficult to reproduce than a pavement designed and built for the first time.

Recently, always in Switzerland, it was decided to impose a minimum of restrictions on the use of the flooring Regenerated Asphalt (RAP). Restrictions based on the fact that, as asphalt ages, it becomes rigid.

In such a situation, all the old materials may not be compatible with the new materials.

Incompatibility which would be found during the mixing process and which would cause the formation of granules, even of medium-large dimensions.

Martins Zaumanison this point he states: “In addition to the size of the granules and the pulverized content, the initial quantity and conditions of the bitumen also have a lot of weight, but depending on the cases that arise, they can vary considerably.”

And yet: “It would be necessary to put into practice some specific test methods to examine the available material and identify any cracks or plastic deformations. The tests carried out and the pilot projects experimented so far, however, have pushed manufacturers to strongly believe in the use of regenerated asphalt (RAP).”

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Asphalt regeneration
A stretch of road along the town of Uster in the Swiss canton of Zurich (Photo: Christian Friker/SchweizMobil)

The tests in Uster and along the Lukmanier Pass

Martins Zaumanis focuses, in particular, on two specific tests which took place, respectively, in the district of Uster (Canton of Zurich) and along the Lukmanier Pass (crossing point between the Cantons of Grisons and Ticino).

During the first test, that of Uster, it was possible to introduce, as the researcher himself explains, a percentage of RAP of 30 percent in the layer of fairly damaged road surface.

Uster has a particularly busy road network. For road sections of this type, it is feasible to insert a quantity of RAP aggregates that varies between 40 percent and 50 percent.

However, to further increase the content of RAP aggregates or Regenerated Asphalt Paving, he specifies Martins Zaumanis, it would be useful to insert pieces of asphalt with a modified binder and high polymer content.

The Lukmanier Pass, compared to the Uster road artery, is not heavily trafficked, but it is alive weather conditions quite rigid. Just think that we are at an altitude of around 1.900 metres.

With such an obvious altitude, strong temperature variations are frequent and the latter can cause cracks in the road surface.

It is precisely in road sections like this, explains the EMPA researcher, that it is necessary to work on an asphalt with a high content of RAP aggregates which would thus allow it to resist these conditions.

Thus, during the works, two layers of asphalt were placed: the first layer had approximately 70 percent RAP aggregates; the second layer, placed on top of the first, had RAP aggregates of about 85 percent.

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asphalt regeneration
Example of a road network with a pavement, structurally speaking, modern (Photo: Pixabay)

Regenerated asphalt: the role of study and innovation

As often happens in various fields, even in the world of infrastructures both study and innovation play a particularly significant role. In fact, we want to simplify the various work processes and thus achieve the set objectives.

Il recycling of materials, including road material and the design and modification of roads with the addition of some innovative materials, worked together with old and already used materials, is what various companies operating in this sector want.

Among them, it stands out Solid Earth; company that focuses all its attention on ecological infrastructures and makes recycling and circular economy its daily bread.

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asphalt regeneration: a small Swiss village
Construction site open and at work on a road that crosses a small Swiss village (Photo: EMPA)