iMAS Innovative mastic asphalt for energy and emissions savings
Production of asphalt mixes in Austria spends around 4.2m GJ in energy per year. The largest portion of energy is needed due to high temperatures for mixing in asphalt plants. This problem applies even more for mastic asphalt since the production temperature ranges between 230°C and 250°C and is thus 50°C to 100°C higher than for regular hot mix asphalt. Reducing this temperature has a large potential for better energy efficiency in asphalt production. Starting in the 1990s, a large number of products (agents) and methods for temperature reduction of asphalt mixes have been developed. These products and methods are successfully used for standard asphalt mixes in a number of European countries, e.g. Switzerland (16%), Sweden (7%), France (3%) and the USA (21%), where a significant share of asphalt mixes are produced with low-temperature technology. In Austria, on the other hand, no significant amount of low-temperature asphalt is used. In addition, there is only very limited knowledge and experience with low-temperature technology in mastic asphalts. Thus, low temperature additives are used for mastic asphalts without optimizing production and mix design of the mastic asphalt. Due to high production temperatures of regular mastic asphalt, gases and aerosols are emitted with reported harmful effects on worker's health.
The central object of the research project is the development of innovative, low-temperature mastic asphalt mixes up to market-readiness. Besides conventional methods for temperature reduction by mixing waxes into bitumen, an innovative method by well-defined substitution of usually used crushed by rounded aggregate in the mix is planned. Investigations within a still on-going research project (EMA – high efficiency low emission mastic asphalt) show that by combining the effects of waxes and rounded aggregates, temperature reduction of up to 50°C are possible, while the quality of the mix stays at a high level. These innovative mixes will be further optimized in the lab and will then be realized in a conventional asphalt mix plant in larger scale. First experience for practice construction will be gathered by installing test fields with the innovative mixes. Subsequently, a test section on the public road network within Vienna will be constructed using conventional and innovative mastic mixes. This will help to evaluate the actual temperature reduction and workability in practice, as well as performance under climate and traffic by continuous condition assessment. We want to reach “30+/20+/20+” not only in the lab but also in the field: a temperature reduction of more than 30°C and a reduction in energy consumption and greenhouse gas (GHG) emissions by more than 20%.
In addition, long-term effects will be investigated by physicochemical and life-cycle analysis to assess further saving potentials due to higher durability of innovative mastic asphalt mixes because of reduced thermal loading at production. For the life-cycle analysis realistic data will be available from the asphalt mixing plant, the construction of the test section and the continuous condition assessment. Thus, by showing that the technology is applicable for practical use as well as energetic and economic effects can be proven for real-life production, incentives are created to enhance the share of low-temperature mastic asphalts in Austria to 75% by 2020.
