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From hot to warm

Future trend: temperature-reduced asphalt

Asphalt is a hot thing: The mixing process usually occurs at temperatures of 160 °C – an energy-intensive process that involves high costs and impacts the environment. The alternative to conventional asphalt production is temperature-reduced asphalt, also known as low-temperature asphalt, warm asphalt or warm mix asphalt.

The production of temperature-reduced asphalt is not a new topic – the process was already tested back in the 1990s. Today, with road construction authorities also focusing on issues such as CO2 balance, protecting resources and reducing the energy input, everyone is talking about temperature-reduced asphalt. As a company that thinks and acts with a focus on sustainability, Benninghoven reacted to these requirements early on and developed optimum technological solutions for supplying the market with temperature-reduced asphalt.

Temperature-reduced asphalt is asphalt that is produced and processed at a low temperature without any negative impact on its properties.

Pioneer for new paths

While the temperature reduction of mastic asphalt has been mandatory since 2008 for health and safety reasons (from 250 to 230 °C), temperature-reduced rolled asphalt has not yet become established in Germany – in contrast to the US and some European countries, where up to 40 % of the installed asphalt is produced at reduced temperatures. Benninghoven offers convincing solutions for this. Asphalt mixing plants from Benninghoven are in use worldwide and prove that the high quality demands with regard to the asphaltic mixture, the economic efficiency and the existing regulations for climate protection and health and safety can be combined perfectly.

At a glance

What is temperature-reduced asphalt?

In short, these are asphaltic mixtures produced at a temperature between 110 and 130 °C. Hot asphalt, on the other hand, is typically produced between 140 and 180 °C – usually with bitumen at 160 °C as a binder. A clear advantage: The reduced-temperature mixtures can be conveniently produced and processed in the conventional manner.

Good reasons for temperature-reduced asphalt

20 to 40 °C less make the crucial difference

Environmental protection and resource protection

Enormous potential for energy savings

In its Asphalt Guide on the topic of temperature-reduced asphalt, the German Asphalt Association states that substantial savings in the resource and emissions balance can be achieved with a temperature reduction of 30 °C .

Example of a daily production of 2,000 t of asphalt

Deutscher Asphaltverband e.V., asphalt Leitfaden, Temperaturabgesenkte Asphalte [Asphalt Guide, Low-Temperature Asphalts – published by the German Asphalt Association]

Health and safety

Less strain during production and processing

Hot processing of bitumen releases vapours and aerosols. Even small temperature reductions result in a significant reduction of the vapours and aerosols, protecting the workers during production and also during transport and processing. At the same time, the heat output is reduced.

Lowering the workplace limits

Temperature-reduced asphalt is a substantial factor in achieving the workplace limit of 1.5 mg/m³ for bitumen, which will become binding in 2024.

The pivotal point: reducing the bitumen viscosity

The bitumen requires a temperature of at least around 140 °C to achieve good wetting and coating of the aggregates in the mixer. Below this temperature, it is too viscous. To lower the temperature during asphalt production, the bitumen viscosity has to be reduced temporarily. This is achieved by adding water (foam bitumen) or additives.

When the hot bitumen is mixed with water, the resulting water vapour expands suddenly – the bitumen foams and the volume increases manifold. This larger surface allows for better wetting of the aggregates in the mixer. This means that the mineral is coated well even at a lower temperature. Another option for lowering the bitumen viscosity is to add solid or liquid additives.

Substantial energy reduction

A comparison of the temperature level during the production of hot asphalt, temperature-reduced asphalt and cold asphalt shows that the temperature can be reduced by up to 40 °C by using foam bitumen, ensuring a high mixture quality even in the range between 110 and 130 °C. At the same time, energy consumption and CO2 emissions are also significantly reduced.

The fast way to temperature-reduced asphalt

Our solutions for you

Solution 1: the Benninghoven foam bitumen module as an uncomplicated retrofit

Technical feasibility is much easier to achieve than asphalt mixing plant owners often think: The weighing and mixing section is simply expanded with the Benninghoven foam bitumen module, consisting of a bitumen pump, expansion chamber, pipes, injection bar and water dosing. With the Benninghoven “Plug & Work” solution, retrofitting is possible at any time, even on existing plants.

Plug & Work

Thanks to pre-configured interfaces, the foam bitumen module can easily be connected to the mixer cabinet and the bitumen weigh hopper.

Gentle on the material

The lower thermal stress is gentle on the components and ensures lower wear on the asphalt mixing plant. At the same time, the lower production temperature reduces thermal ageing of the binder.

Water – quickly accessible basis

The water required for the foam bitumen module is usually easily accessible at any asphalt mixing plant. The addition of water is cheap and safe.

“Foam bitumen is the medium of choice for temperature-reduced asphalt. Benninghoven has a high level of expertise in this area and can also integrate the technology into existing plants.”

Matthias Lenarz, Team Leader Bitumen

Solution 2: adding additives directly into the mixer

Smaller quantities of solid additives are added through the powder/granulate dosing system. Up to two liquid additives can be added through the adhesive system.