Basics of Cold-Mix Applications with Asphalt Emulsions

What is the difference between “dense graded” and “open-graded” emulsion mixes?

Dense-graded mixtures contain aggregate that have been selected to include fine material and filler. When compacted the mixture has only low air voids and is essentially impermeable to water. Open-graded mixtures contain aggregate without the very finest materials and when compacted have high voids and are permeable to water. Because of its high fines content the aggregate in dense graded mixes is generally more reactive towards asphalt emulsion and demands slow-setting grades than open-graded mixtures.

Why should I use cold emulsion mix rather than hot mix?

Cold mixes use less energy and produce fewer emissions than hot mixes. Cold mix plants are lower cost, simpler and more mobile than hot mix plants and emulsion mixes lend themselves to on-site and in-place manufacture. The ability to stockpile material for future use leads to less waste and reworking than with hot mix.

How should I select the emulsion for cold mix?

Emulsion selection is on the basis of laboratory mix designs. Mix designs ensure that the emulsion is compatible with the aggregate and that the mixture is durable. Slow-setting emulsions are generally used for dense mixes and medium-setting emulsions for open-graded mixes. Your emulsion supplier can adjust the emulsion formulation if necessary to best suit the aggregate and application.

What are the advantages of warm mix?

Asphalt emulsion can be used in a conventional hot mix plant but require lower mix temperatures. The advantage is greatly reduced emissions and less hardening of the asphalt binder. The higher viscosity of the base binder at the mix temperature allows thicker films to be deposited on open-graded aggregates.

Where can I learn more about cold-mix applications using asphalt emulsions?

You can order AEMA’s Basic Asphalt Emulsion CD-Rom right here on this web site – just click here.

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