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Recycled Asphalt Mixes


Recycled Asphalt Mixes

Mixes can be made with 100% recycled asphalt pavement (RAP). These mixes are economically and environmentally friendly. Recycled asphalt mixes utilize RAP that can be crushed, graded, mixed, and laid on-site using custom-engineered rejuvenating emulsions.

Design Criteria

When designing a recycled asphalt mix, a number of factors have to be examined and assessed to ensure a proper mixture will be placed that will perform for its intended service life. The following factors can have a tremendous effect on the performance of a recycled asphalt mix: RAP material, virgin aggregate shape and type, mix workability, coating ability, and residual asphalt content.

RAP Material: 

The RAP material is typically processed RAP taken from milling operations. The material can be split into coarse and fine RAP then blended back to make a better gradation. The physical properties of the recycled material (asphalt content, gradation of RAP, gradation of extracted RAP, and recovered penetration) should be determined.

Virgin Aggregate Shape and Type: 

The overall shape of the virgin aggregate can influence the quantity of aggregate as well as the amount of asphalt emulsion to be used. The more graded the aggregate is, the higher the emulsion quantity needed. The compatibility of the emulsion used with the aggregate is critical.

Mix Workability: 

The emulsion used should give the finished mix enough workability to be placed in a homogeneous condition and be designed for the intended method of processing, be it immediate placement or in a stockpile for future use.

Coating Ability: 

The asphalt emulsion should have the ability to coat the fine aggregate in the mix (passing the 4.75 mm sieve) without the fine aggregate balling up. With some emulsions, the use of mixing water will aid in coating fine particles. The use of emulsions containing solvent will aid in coating and dust penetration as well as aid in the workability of the mix.

Asphalt Residual in the Emulsion:

The quantity of asphalt residual in the emulsion can affect the quantity of asphalt emulsion needed to coat the aggregate. The lower the residual, the higher the quantity of asphalt emulsion needed.

During the design process, two key factors are needed: a well-coated mix and a mix with adequate strength and stability to be able to handle the expected traffic load and volume.

A recycled asphalt mix typically requires an emulsion content of 1.0 to 4.0% (depending on the design parameters), a minimum of 2500 N stability at 25°C, and air voids of 7 to 11%.


Asphalt Emulsions:

Several factors have to be taken into account when choosing the emulsion to be used. The type and grade of emulsion required is affected by the RAP material, the virgin aggregate, the emulsion’s coating ability, the compatibility between materials, the mixing method used, the environmental conditions, and the laying and compaction process. The most widely used grades of asphalt emulsion in recycled asphalt mixes are SS-1, CSS-1, MS-2, CMS-2, HF150, and HF150M. In recent years, proprietary emulsions including rejuvenating emulsions have been developed for use in these recycled mixes.

Mix Aggregate:

The virgin aggregate used in blended recycled asphalt mixes can be processed or semi-processed crusher, pit, or bank run aggregates. Most are graded from a maximum size of 25 mm, have very low clay content, and do not have an excessive amount of material passing the 75 µm sieve. The recycled asphalt material can be screened or unscreened RAP material from grinding projects or processed RAP piles.  It is preferable to fractionate the RAP and recombined as necessary to have a better control over its final gradation and the overall mix properties.

Performance Guidelines

In order to construct a proper, well-designed recycled asphalt mix, the following guidelines should be followed:

Safety Data Sheets

DescriptionPdf File
SDS – Anionic Medium Setting Emulsion
SDS – Anionic Rapid Setting Emulsion
SDS – Anionic Slow Setting Emulsion
SDS – Cationic Emulsion Breaking Agent
SDS – Cationic Medium Setting Emulsion
SDS – Cationic Quick Setting Emulsion
SDS – Cationic Rapid Setting Emulsion
SDS – Cationic Slow Setting Emulsion
SDS – Rapid Curing Cutback

Related Resources

DescriptionPdf File
Research – 100 Percent Recycled Asphalt Paving, Our Experience
Research – A Laboratory Investigation of the Compaction of Dense Graded Asphalt Concrete
Research – Recycling: A Laboratory Study
Research – Rubber Asphalt Mixes using Warm Mix Technology
Product Data Sheet – HF-150P
Product Data Sheet – HF-150S
Specialty Process Overview – EverLife Recycle®
Fact Sheet – EverLife Recycle®
Product Data Sheet – HF-250S

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