Warm Mix Asphalt Systems

ASTEC

W A R M M I X A S P H A L T S Y S T E M S

ASTECWarm Mix Systems for Continuous Mix and 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 50˚F to 100˚F lower than conventional hot mix. To achieve this, the viscosity of the asphalt cement (AC) 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 asphalt cement, special procedures and/or special AC delivery systems to achieve low viscosities at low temperatures. The additives are expensive and add significant cost per ton of mix. Astec warm mix systems eliminate the need for expensive additives and special asphalt cement by mixing a small amount of water into the AC to create microscopic bubbles. These small bubbles act to reduce the viscosity of the AC coating on the rock allowing the mix to be handled and worked at lower temperatures.

Water is delivered to the system using a positive displacement piston pump capable of accurately metering water into the system. Using feedback controls, pump speed is modulated to maintain the appropriate flow of water based upon the flow of AC. PLC controls provide for smooth and consistent water flow as production rates increase or decrease.

Water is injected into the liquid AC through a series of all stainless steel injectors located above corresponding foaming chambers. AC flows through the foaming chambers where water and AC are thoroughly mixed to produce mechanically foamed AC.

A skid-mounted corrosion-free water reservoir is provided with an automatic filling valve. If supply water is lost, a low-water alarm alerts plant personnel so the problem may be resolved quickly without wasting mix.

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.

Improved Workability • No Smoke • No Smell • Longer Pavement Life • Lower Fuel Consumption Higher Percentage Recycle Mix with Standard Grade of Asphalt • Higher Production Rates

Easily work the low-viscosity mix by hand.

A. Water manifold.B. Water lines. C. Liquid AC manifold.

A skid-mounted corrosion-free water reservoir is included with warm mix system packages. An optional cold weather package is available to pre-vent damage to components when temperatures drop below freezing.

For more information on Astec’s warm mix asphalt systems please visit www.astecinc.com.

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C

B

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Improved Workability • No Smoke • No Smell • Longer Pavement Life • Lower Fuel Consumption Higher Percentage Recycle Mix with Standard Grade of Asphalt • Higher Production Rates

Though the system is compact, it has been designed with the plant crew in mind. The self-cleaning water injectors require only periodic inspection and may be removed and replaced from the top of the unit without removing the front cover. Foaming chambers have no moving parts.

AC MANIFOLDField-proven and highly reliable.

Photo: Roadtec RP-190 paver laying warm mix from an Astec warm mix system. Notice no visible smoke emissions.

AIRCLOSEDAIR

OPENED

WATER IN

FOAMED AC OUTWATER ON

LIQUID AC OUTWATER OFF

LIQUIDAC IN

LIQUIDAC IN

AIRCLOSEDAIR

OPENED

WATER IN

LIQUIDAC IN

LIQUIDAC IN

ASTEC, INC. an Astec Industries Company4101 JEROME AVENUE • CHATTANOOGA, TN 37407 USA • 423.867.4210 • FAX 423.867.4636 • astecinc.com

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