Astec Green Pac for Batch Plants

The benefits of warm mix asphalt such as reduced energy consumption, lowered emissions, and elimination of visible smoke are well-known in the asphalt paving industry. Warm mix technology allows mix to be prepared and placed at lower temperatures, typically 30˚C to 50˚C lower than conventional hot mix. To achieve this, the viscosity of the bitumen must remain low at the reduced temperatures. Maintaining a low viscosity at lower temperatures allows mix to flow freely through storage, transfer and placement equipment and is more easily worked by hand.

Unfortunately, many technologies for warm mix production rely on additives, special bitumens, special procedures and/or special bitumen delivery systems to achieve low viscosities at low temperatures. The additives are expensive and add significant cost per ton of mix.

Astec warm mix Green Pac systems eliminate the need for expensive additives and special bitumens by mixing a small amount of water into the bitumen to create microscopic bubbles. These small bubbles act to reduce the viscosity of the bitumen coating on the rock allowing the mix to be handled and worked at lower temperatures.

The Green Pac system for batch plants comprises a bitumen foam manifold assembly and a skid mounted water delivery system. The Green Pac system foam bar is mounted remotely from the pugmill eliminating the problem of nozzle blockage common with other foaming systems.

Bitumen is pumped to the Green Pac system either from the main bitumen supply via a metering system or alternatively drawn from the bitumen weigh kettle.

Water is delivered to the Green Pac system using a positive displacement piston pump capable of accurately metering water into the system.

Water is injected into the bitumen through a series of all stainless steel injectors located above corresponding foaming chambers within the Green Pac system foam bar. Bitumen flows through the foaming chambers where water and bitumen are thoroughly mixed to produce mechanically foamed bitumen. The foamed bitumen flows from the Green Pac manifold down a delivery pipe to the pugmill mixer.

Astec can retrofit warm mix systems to continuous mix and batch plants from any manufacturer, bringing the benefits of the Astec warm mix system to all asphalt pavement plant configurations.

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