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Cutback Asphalt and Emulsified Asphalt

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Discussion Paper Possible Control Measures on Volatile Organic Compounds (VOC) Concentration Limits in Cutback Asphalt and Emulsified Asphalt

What are cutback asphalt and emulsified asphalt?

Cutback asphalt and emulsified asphalt are used for a number of applications involving road construction. In preparing these products, asphalt cement is mixed with either a petroleum diluent to produce cutback asphalt or with emulsifiers, water, and sometimes petroleum diluent to produce emulsified asphalt. Once the liquefied asphalt cement is applied during road construction, the diluent petroleum solvent (in the case of asphalt cutbacks) and water (in the case of asphalt emulsions) evaporates leaving the residual asphalt cement to perform its function.

  • Emulsified asphalt is produced by dispersing tiny globules of asphalt cement into water treated with a small quantity of emulsifying agent. The water comprises the continuous phase and the globules of asphalt cement make up the discontinuous phase. The emulsion setting rate will determine the different grades for emulsified asphalt.
    • Rapid setting (RS)
    • Medium setting (MS)
    • Slow setting (SS)
    • Quick setting (QS)
  • Cutback asphalts is produced by mixing asphalt cement with a petroleum diluent. Cutback asphalt is classified into three groups depending on the relative speed of evaporation of the petroleum diluent.
    • Rapid curing (RC)
    • Medium curing (MC)
    • Slow curing (SC)

Applications of cutback asphalt and emulsified asphalt

Emulsified asphalt and cutback asphalt products are used in a variety of road construction applications. The applications of asphalt products include:

  • Plant mix (open-graded, dense-graded, sand);
  • Road mix (mixed in place), including mining with open- and dense-graded aggregate, sand, sandy soil;
  • Surface treatment, including fog, sand, chip, sandwich, and slurry seals, micro surfacing and cape seal;
  • Asphalt applications including prime and tack coat, dust palliative, crack filler;
  • Maintenance mix;
  • Cold in place recycling; and
  • Full-depth reclamation.

There are numerous grades of emulsified asphalt and cutback asphalt products that can be used for a given application. The product grade selected for a given road construction project varies depending on project and performance objectives, agency specifications, as well as field conditions including available aggregate, weather, temperature, and performance.

Volatile organic compounds in cutback asphalt and emulsified asphalt

Different types of cutback asphalt and emulsified asphalt products are associated with different emission factors of volatile organic compounds (VOCs) as shown in the following table:

Table 1. Estimated Emission Factors for Product Groupings

Emulsified asphalt
Product GroupEmission Factor[1]
Low or no VOC emulsions0.5%
High float surface treatment emulsions1.5%
High float mixing grade emulsions3.0%
Prime15%
Cutback asphalt
Product GroupEmission Factor[1]
Rapid cure (RC)28%
Medium cure (MC)15%
Slow cure (SC)3.5%

Note: An emission factor is a representative value that relates the quantity of a pollutant released to the atmosphere with an activity associated with the release of that pollutant.

Estimates of VOC emissions from cutback asphalt and emulsified asphalt

Based on the Environment Canada study[2] and 2010 end user survey, the information concerning usage and emissions of cutback asphalt and emulsified asphalt in Canada is summarized below:

  • An estimated 301 kilotonnes (kt) of liquefied asphalt was used in 2009, of which
    • 256 kt was emulsified asphalt;
    • 45 kt was cutback asphalt.
  • A total of 8.8 kilotonnes (kt) of VOC was emitted in 2009, of which
    • 3.6 kt was emulsified asphalt;
    • 5.2 kt was cutback asphalt.
  • With this information it can be observed that cutback asphalt is responsible for 60% of the total emissions of VOC, even if it only represents 15% of the total use of liquefied asphalts in Canada.

Previous and current activities addressing VOCs

Federal Agenda for Reduction of Emissions of VOCs from Consumer and Commercial Products

In March 2004, the Ministers of the Environment and of Health published the Federal Agenda for the Reduction of VOC Emissions from Consumer and Commercial Products. The 2004 Federal Agenda outlined the Government of Canada's plan to develop regulations under the Canadian Environmental Protection Act, 1999 to set VOC emission standards for specific consumer and commercial products. The first step to implement the 2004 Federal Agenda was completed with the commitment to develop three sets of regulations for consumer and commercial products, as announced in the April 26, 2007, Regulatory Framework for Air Emissions. This was followed by the development in 2008 and publication in 2009 of two regulations to limit the VOC content in automotive refinishing products and architectural coatings, and continuing work on the third regulation, which is for certain consumer products in Canada.

Potential additional measures to reduce emissions of VOCs from consumer and commercial products

In June of 2010, Environment Canada published a discussion paper on the proposed renewal of the Federal Agenda for the Reduction of Volatile Organic Compounds (VOCs) from Consumer and Commercial Products. The discussion paper outlines a number of possible initiatives for the Government of Canada to take in order to reduce VOC emissions from consumer and commercial products during the year 2010 to year 2020 period. The "cutback asphalt and emulsified asphalt" category was identified as one possible area for the development of reduction measures by the Government of Canada.

More general VOC background information is available on our VOC Web page.

Path forward

Environment Canada is now proceeding with the development of a risk management instrument under the Canadian Environmental Protection Act, 1999 to reduce the emissions of VOC from this sector. Information regarding this risk management instrument and its development will be posted on our VOC web page.

How can I stay informed?

Join our mailing list by sending an email with your full contact information and stating which topic is relevant to your firm to vocinfo@ec.gc.ca. When updates are made to the Web page, you will be notified.

Consultation and information sessions

A consultation session on possible control measures to establish VOC concentration limits from asphalt products was held on Tuesday, March 27, 2012, in Toronto. A discussion document that outlines the background information and discusses potential approaches is available here. Two presentations were given in Fredericton, on Sunday, October 15, 2012. One to the Chief Engineers' Council of the Transportation Association of Canada and one to the Soils and Materials Standing Committee and Pavements Standing Committee.

Contact information

Questions and inquiries can be directed to Environment Canada as follows:

Telephone: 819-956-1669
Fax: 1-888-391-3695 or 819-953-3132
Email: vocinfo@ec.gc.ca
Website: Environment Canada


[1] Technical and Economic Study on VOC Emissions from Emulsified and Cutback Asphalts in Canada, Environmental Health Strategies, Environment Canada, October 2010.

[2] Technical and Economic Study on VOC Emissions from Emulsified and Cutback Asphalts in Canada, Environmental Health Strategies, Environment Canada, October 2010.