The technology
State of the art of rubber modification of bitumen & asphalt

Our production of rubber-modified bitumen granulates is the latest level of development. In addition to maximum reliability, high performance reserves and above-average durability, the advantages lie in the problem-free and process-reliable application. 

  • In the use of rubber-modified binding agents, today it is possible to make use of a long background of experience with many different asphalt pavements.
  • The first large-scale findings come from the United States. As early as the 1970s, large-scale tests were performed in Arizona. 10 years later, the wave swept to Europe via Belgium and France and later to Germany and Austria.
  • In all the applications at the time, pre-produced, hot-liquid rubber-modified bitumen was successfully used
  • In parallel to this development, attempts were also made to establish simpler, so-called dry processes. However, this never asserted itself quality-wise, as the polymers from the rubber could not be mobilised sufficiently due to the absence of mixing temperatures and dwell times. Therefore, the optimal embedding of the polymers into the bitumen matrix was missing in these systems.
  • When it came to use in Europe, the hot-liquid rubber-modified binding agents were initially focused on application in porous asphalts due to the high workload. There in particular, the qualitative advantages showed themselves very clearly within short lay times. And what also cannot be ignored in this connection is that the clients’ willingness to bear additional costs was greater in this application.
  • In Austria, the Inn Valley Motorway was the first measure to be equipped with a porous asphalt cover. Successful, as the installed OPA achieved a lay time of 17 years. In Germany, the first applications took place in 1986. The A8 motorway in Saarland and Neuherbergstraße in the city of Munich.
  • To this day, CTS Bitumen GmbH has provided the rubber-modified bitumen for more than 3,700,000 m2 PA in the Free State of Bavaria alone.
  • Currently, i.e. for the last 15 approximately, rubber-modified bitumen granulates have marked the qualitative summit of rubber modification. In many construction measures, these have proved their worth in practice, are already showing exceptional useful lives and are shining thanks to  high efficiency in the installed asphalts.
  • Trend towards demixing? Overdemanded bitumen conveying systems of the asphalt mixing plant? Just foreign words for GRM by CTS.
  • Standard binding agents cannot always meet all requirements.  Since the 1970s, there has therefore been intensive occupation with the matter of how to counteract the massive damage (e.g.: material loss, crack susceptibility, thinning). The problem is intensified by many other factors, such as the increasing traffic load, especially the rising heavy traffic proportion, by the “rail-guided” lorry traffic as well as by climatic changes. Only by designing efficient and long-lasting asphalt pavements are the right answers found. Especially since implementation can stem the cost explosion.
  • The solution is obvious: for special demands, only the best possible binding agents can be used. And this can succeed only through a change, i.e. modification of the standard bitumen. In Germany, approximately 30% of all binding agents used are modified.

This charts shows an example of the suboptimal decomposition of individual rubber particles at low temperatures and short dwell times in the reaction vessel (170°C and approx. 2 hours). The decomposition is not complete. Valuable resources are wasted and the performance in the asphalt is effective only to a limited extent. Reason: The polymers do not achieve the volume aimed for and the viscosity of the thus achievable binding agent, i.e. possible thickness of the binding agent films is insufficient.

Clear differences are visible here. The decomposition of the rubber particles is carried out at a reaction temperature of approximately 200°C and a dwell time of at least five hours, hermetically sealed. Result: The optimal and computer-controlled decomposition ensures high efficiency in the asphalt. In each case, the product viscosity is so high that thick binding agent films (durability!) are safely achieved and the addition of binding agent substrates in the asphalt is usually not required.

Advantages

  • Mature products with sufficient long-term experience (> 25 years).
  • Products achieve the specification requirements of the applicable regulations.
  • A special dosing device is not required.
  • Viscosity-modifying additives can be added to the asphalt.
  • Products are ready to use. A so-called “maturation period” in the pre-fabricated silo of the asphalt mixing plant is not required.

Disadvantages

  • Not a storage-stable product. The demixing process begins during delivery. Therefore, the bitumen tank urgently needs to be equipped with a mixing system.  The bitumen conveying system (pumps, bitumen scales and dosage, all lines) must be adapted according to the viscosity. Therefore, it may be necessary to invest in the asphalt mixing plant.
  • Delivery in complete TTFs (25 tonnes) only.
  • The use of RC material at the same modification level is not possible, as ready-to-use rubber-modified bitumen with a higher modification level can no longer be handled at the asphalt mixing plant.
  • Due to prescribed temperature restrictions in production, the polymers from the buffing dust used may no longer be optimally decomposed. This means that an insufficient and fluctuating viscosity level is reached. The consequence: binding agent may run out during use in the PA and the stone mastic asphalt. This production deficiency must therefore be balanced out by adding fibres. The expected asphalt performance does not occur.

Advantages

  • Mature products with sufficient long-term experience (> 10 years).
  • Products achieve the specification requirements of the applicable regulations.
  • The polymers are already decomposed on the production side. Only thus are the resources used optimally. For this reason also, the asphalts manufactured with CTS GRM are immediately usable. A so-called “maturation period” in the pre-fabricated silo of the asphalt mixing plant is therefore not required.
  • Products are nearly unlimited in terms of storability at the asphalt mixing plant.
  • RC material can be used without any problem.
  • An addition of viscosity-modifying additives (in the asphalt or as road construction bitumen with ready additivation) is possible.
  • Small and very small quantities of rubber-modified bitumen granulate are also orderable.
  • Simple delivery by lorry, train, container, big bag. The bagged cargo is packaged as desired by the customer.

Disadvantages

  • Requires own dosing equipment.
  • Alternative: manual or semi-automatic bag feed. Disadvantage: high personal workload.

In the eco-balance carried out in 2020, the GRM-bitumen mixtures perform as ecologically very advantageous.
(see download)

We would be happy to send you our detailed reference lists via e-mail.
Please request it via our contact form.

CTS Blog

CTS, based in Buch am Erlbach, Bavaria (Germany), has been involved in the development and improvement of rubber-modified bitumen for road construction since 1985. Among other things, we developed porous asphalt into "Flüsterasphalt®". As one of the first market participants in the field of rubber modification, we claim to be the technology leader today. After many years of research and continuous development, CTS Bitumen was able to present an absolutely innovative new development: rubber-modified bitumen granulates. This achievement sets new standards and is characterised worldwide by unproblematic handling, transport and above-average performance.

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