Advancing Roadbuilding Sustainability with Warm Mix Asphalt

The increased use of warm mix asphalt (WMA) is making a positive impact on the world around us.

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By utilizing lower temperatures, WMA reduces emissions of volatile organic compounds (VOCs) and other gases. Moreover, this ever-evolving method offers several benefits. They include the ability to take advantage of higher percentages of recycled asphalt (RAP) and extended pavement life through modified binders and additives.

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The Rise of WMA

WMA has become an essential component for road roadbuilding companies committed to sustainability. WMA, also known as low temperature asphalt (LTA), has gained significant popularity in various regions.

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In France in 2019, about 40% of new road construction projects and 70% of road maintenance/rehabilitation projects used WMA, according to the French Road Federation. WMA comprised 40% of all asphalt pavement mixtures produced in the U.S. in 2018, according to a survey conducted by the National Asphalt Pavement Association (NAPA).

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The growth can be attributed to advancements in plant technology that enable efficient WMA manufacturing – and result in high-quality mixes, too.

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Ammann’s Commitment to WMA

Ammann has demonstrated a strong commitment to WMA. The company has thoroughly researched and examined the WMA process – from the plant all the way through compaction – to ensure success on the jobsite. As a result, Ammann has secured a number of patents related to recycling and WMA production.

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Benefits of WMA

Improving technology has facilitated the manufacturing of asphalt at decreased temperatures. This results in lower energy consumption per tonne of production – and reduced emissions at the plant and on project sites.

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WMA also utilises RAP. Ammann’s proprietary heating process gently raises the temperature of RAP, lessening fuel burn and emissions while protecting the bitumen. Independent research supports this approach.

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The benefits of WMA are significant.

-??????WMA reduces fumes throughout the process – from the plant, to transfers to trucks and the paver, and even at the auger and behind the screed. This is a welcome result for workers and local residents.

-??????Fuel consumption is reduced. It is estimated that each tonne of WMA produced saves 1.5 kg of fuel oil when compared with the hot-mix process.

-??????The reduced fuel usage results in CO2 reductions of 4 kg to 5 kg per tonne.

-??????The foamed bitumen mixes well with RAP, creating even more environmental benefits.

-??????Fewer compaction passes are required because of the narrow compaction window.

-??????The final product is almost identical to hot-mix asphalt in terms of ease of compaction and smoothness.

-??????The mixes generally hold up as well as their higher-heated brethren. Asphalt life might even be extended due to the gentle treatment of the binder.

-??????WMA is lower on the plasticity range, which is helpful when paving on steep inclines.

-??????Warm mix can utilise organic additives, such as zeolite, and inorganic additives, including crystalline.

-??????The paving process is quicker, primarily because of fewer compaction passes. This enables a quicker return to normal traffic flow.

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The Role of Ammann’s as1 Control System

The Ammann as1 Control System serves as the brains of the plant, offering modules that address fuel burn, emissions and other sustainability concerns. The system is also a great fit for asphalt producers who want to employ WMA.

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The as1 Dynamic Recycling Addition (RAD) module allows operators to easily modify the RAP ratio during production, ensuring the WMA remains compactible. An integrated wizard guides the operator through the recipe input process, simplifying adjustments to the RAP ratio.

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Foam is the Future

The as1 plays an important role in foaming in both batch and continuous plants. Ammann Foam? works without any chemical additives and also can be retrofitted to existing plants with minimal effort.

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WMA involves an extra processing step. Bitumen heated to about 160o C is blended with cold tap water. The cold water instantly evaporates, creating a bitumen foam that is then injected into the mixer, where it blends well with heated aggregates. The WMA process varies slightly from that of cold asphalt, where the aggregates are not mixed with bitumen and other additives.

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Advanced Paving

Premium Ammann pavers feature PaveManager 2.0, a technologically advanced, automated HMI system that provides operators with permanent feedback about the paving project to allow real-time adjustments.

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This responsiveness ensures the paver is operating at peak efficiency to place the asphalt properly – and in a timely manner that will enable compaction.

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Intelligent Compaction with ACE

Ammann Compaction Expert (ACE), Ammann’s proprietary Intelligent Compaction system, assists operators in monitoring progress and achieving quality goals. Ultimately, it helps ensure that asphalt placed at a lower temperature is still properly compacted.

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On the sustainability front, ACE helps verify targets are met with the fewest passes of the roller. This reduces fuel burn, emissions and operating costs.

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WMA Promotes a Greener World

Many asphalt producers consider the WMA process to be cost-neutral, primarily because of the extra step required to develop the foam. But costs continue to fall as the use of WMA becomes more prevalent – and therefore more routine.

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Another way of looking at this: WMA generates a number of environmental benefits at no additional cost.

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