Rubber modification of road construction bitumen and asphalt

What is "GRM by CTS"?

A lot of knowledge on the topic of “rubber modification of bitumen and asphalt” and years of patient tests were needed to develop the concentrated rubber-modified bitumen granulates “GRM by CTS”. GRM stands for Granulate Rubber Modified. GRM by CTS is produced from buffing dusts with additivation specially manufactured for CTS, bitumen and bulking agents with specific properties in a complex and controlled manufacturing process. Due to the fact that the polymers from the buffing dust used are optimally decomposed and combined with the bitumen matrix, the asphalts manufactured with GRM by CTS can be installed immediately after production. Today, GRM by CTS safely fulfils all the requirements set by the “Technical conditions of delivery for rubber-modified bitumen, TL RmB-StB, By; 2010 Edition” and “E GmBA – Recommendations on rubber-modified bitumen and asphalt; 2012 Edition”.

At the asphalt mixing plant, GRM by CTS is added directly to the mixing process along with aggregates and road construction bitumen. The asphalt pavements designed in this way show the greatest advantage: a long useful life. In the event of proper application and corresponding dosage, it can increase by 40 – 50% on average (compared to asphalt pavements with conventional formulae) e.g. in the case of porous asphalt. Evaluations of existing roads confirm this.
The GRM by CTS rubber-modified bitumen granulates are demixing-stable. They are delivered by lorry and can be stored long-term at the asphalt mixing plant without concern in the event of an appropriate environment. The dosage takes place directly into the asphalt mixer. Usually, no changes are required to the usual asphalt production.

Use of GRM by CTS in the Flüster-Asphalt®

The high efficiency of GRM by CTS 40/20 impresses particularly in the production of Flüster-Asphalt®. (Porous asphalt, PA).

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Origin and success of GRM by CTS

Until 2005, rubber-modified bitumen was available only as a “liquid product”. From an asphalt technology perspective, this “liquid product” brought very good results. However, this positive impression was clouded by a series of negative accompanying circumstances:

  • It was storable only to a limited extent,
  • available in complete TTFs only and,
  • therefore usable in a limited radius of production
  • and sensibly as of a certain size of construction measure.

Since 2005, the product GRM by CTS has now been available in granulate form. Thus, it is now possible to expand the transportation radius around the whole world and to increase storability considerably.

Additionally, even the first tests showed that the new granulate possessed even better properties than the liquid variant. This led to the production department at CTS Bitumen GmbH focusing heavily on GRM by CTS. The success of the new product resulted in a huge increase in the marketed quantity of rubber-modified bitumen of CTS Bitumen GmbH:

Further information

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Use of GRM by CTS in the Flüster-Asphalt®

Flüster-Asphalt® is the concept for noise-reducing asphalt construction methods. CTS Bitumen has trademarked the name and it stands for noise-optimised porous asphalts designed with rubber-modified CTS bitumen.

Thanks to many years of experience and a great deal of practical knowledge (since the beginning of the 1980s, CTS has occupied itself intensively with the problems related to porous asphalt) as well as the high quality level of CTS’s rubber-modified binding agents, a significantly extended useful life was achieved as a result. With the background of more than 4,000,000 m² installed PA in Germany, an average useful life of approximately 14 years was determined. You will find more information on this on our reference page. In the case of comparable roads formulated with traditional, higher-modified PmB A 40/100-65, an average useful life of only 9-10 years lay time was established.

Long-term, effective noise reduction is dependent on many factors: hollow content, structure of the asphalt, flatness and retention of the surface texture. Noise-reducing asphalts manufactured with CTS Bitumen also show better noise-technical results over a longer period. On the laboratory scale, this statement can be proved by the results of the Cantabro test. Here, the effectively measures grain loss provides a good starting point regarding the permanence of hollow-rich asphalt.

In the Cantabro test, asphalt test bodies are stressed on a defined basis and the grain loss determined. Test bodies manufactured with GRM by CTS 40/20 shine with a typical grain loss of approximately 10 M %. In comparison, the PmB, type PmB A 40/100-65, also show small average grain losses in the scale of 10 – 15 M %. Currently, hot-liquid rubber-modified bitumens show significantly higher grain losses (> 30 M %). The reason is simple. For occupational health and safety reasons, production must take place at a low temperature level. As a consequence, this results in a non-optimal decomposition of the polymers of the buffing dusts used.

In the Cantabro test, the PmB A (PmB A 40/100-65) and GRM by CTS 40/20 show low to very low grain losses. The question arises: are these products equivalent? No, as the documented useful lives speak in favour of rubber-modified bitumens from CTS. Here, too, a simple answer is possible: ageing, oxidation by oxygen, the influence of the climate and UV light afflicts PmB A considerably more quickly and intensively than comparable rubber-modified binding agents. (e.g.: RmB G)

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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