Warm Asphalt Mixes By Adding a Synthetic Zeolite.

The European Union target has been defined to reduce the CO2 emissions between 1990 and 2010 with 15 %. In Germany the Mitteldeutsche Hartstein-Industrie AG and EUROVIA have developed a method to produce hot mix asphalt for road construction at lower temperatures. At the same time it was an objective that this asphalt should be able to be applied and compacted at the lower temperatures without any loss in workability and quality. The concept has been further developed and introduced also in France and the US. The reduction of production and application temperatures of hot mix asphalt means a significant environmental contribution in reducing energy consumption. And by reducing the fumes a significant improvement of the working environment is obtained. The principle of the process is based on the special structure of aspha-min. This creates the ability to store crystalline water into the pores of the molecules. By adding aspha-min in the pre-heated mixture of sand and stone at the same time as the bitumen is being introduced, a water based vapour is created. This creates a controlled foaming effect, which then creates an increased volume of the binder in the mix. The extremely fine foam is creating micro pores, which again are creating a higher workability of the mix. Doing so the mix is obtaining a higher ability to be compacted, which was previously only possible at higher temperatures. A successful application is obtained after a homogeneous addition of the aspha -min. Mixing takes place between 130. and 140.C. It is important that the aspha-min particles are loosing its water content in several steps and not all at once. Until cooling down to approximately 100 .C (212 .F) the possibility to compact the mix was observed. The workability of the mix is increased without changing the temperature. Furthermore no separation of the binder takes place in the mixing process which means that good adhesion between binder and aggregates is obtained. All test sections, which have been constructed so far, demonstrate that the asphalt mix produced with aspha-min does not perform differently from regular asphalt mixes produced without aspha -min. The paper describes results of test sections and reports on the results of laboratory investigations. For the covering abstract see ITRD E135448.