Navigating the EPA’s TCE Phase‑Out for Asphalt Labs
BY Jason Wielinski, P.E. and Wes Cooper
Editor’s Note: Reporting around the industry in late summer 2025 may have added some confusion to the discussion of when trichloroethylene (TCE) was banned. As early as Dec. 21, 2023, AASHTO petitioned EPA to grant the industry a 20-year phase-out period to allow state DOTs time “to investigate alternative methods for asphalt testing with the goal of eliminating TCE from their testing protocols.” Read more about that here. By Dec. 17, 2024, our industry was included in the final ruling’s 10-year phase-out period. See paragraph two below for more detailed information.
The Environmental Protection Agency (EPA) proposed a rule in 2023 to prohibit the production and use of trichloroethylene (TCE) in many industrial applications, including asphalt testing. After a period of comment review and discussion, the EPA published its final ruling in December 2024 in favor of a TCE ban.
To alleviate issues with immediately banning TCE from asphalt labs, a phase-out period has been identified: five years for open systems (this would include centrifuges and reflux systems used in binder extraction from asphalt mixtures) and 10 years for closed systems (this would include auto-extractors). However, those organizations continuing to use TCE during this phase-out period will be required to monitor and document procedures on training employees and establishing a Workplace Chemical Protection Program (WCPP).
ASTM D8159 currently allows for the use of tetrachlorethylene (PCE) and methylene chloride (DCM) as suitable alternatives.
The transition away from TCE will affect asphalt laboratories in several ways, including binder solubility testing and solvent-based extraction and recovery. Fortunately, options are available to asphalt labs to make the necessary adjustments in light of these rulemaking directives and concerns. To that end, the following insights are offered from the Asphalt Institute as a means of assisting asphalt test labs during the transition away from the use of TCE.
Asphalt Binder Solubility
TCE is still the primary solvent used for ensuring that an asphalt binder is relatively free of non-organic mineral matter. The two most common test methods for this type of determination (often referred to as the “Solubility Test”) are AASHTO T 44 (Solubility of Bituminous Materials) and ASTM D2042 (Standard Test Method for Solubility of Asphalt Materials in Trichloroethylene or Toluene). AASHTO T 44 lists TCE or trichloroethane (TCA) as the allowable solvents, while ASTM D2042 permits both TCE and toluene. Of the two test methods, AASHTO T 44 is the most widely used in the United States but is the most restrictive in that it only allows for the use of chlorinated solvents.
In 2016, AASHTO T111 (Standard Method of Test for Mineral Matter or Ash in Asphalt Materials), commonly referred to as the “Ash Test,” began to replace solubility testing in AASHTO specifications for anionic, cationic and polymer-modified asphalt emulsions. ASTM emulsified asphalt specifications followed suit in 2020, allowing for the use of either D2042 or D8078 (Standard Test Method for Ash Content of Asphalt Binder and Emulsified Asphalt Residues). A primary reason for this change was to eliminate testing difficulties related to polymer-modified residues. For example, latex-modified residues are known to “gel” on the crucible during solubility testing, plugging the filter pad and making the test procedure difficult or even impossible to perform.
Like solubility testing, the Ash Test is meant to ensure that paving binders and emulsified asphalt residues are relatively free of mineral matter. Whereas the Solubility Test involves dissolving organic matter with a solvent, the Ash Test uses a muffle furnace to incinerate all organic material, leaving behind a percentage of inorganic mineral matter. The Ash Test procedure accommodates more complex binders while removing the risks associated with the use of chlorinated solvents.
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Solvent Extraction and Recovery of Asphalt Binder
The impact of the TCE ban may be felt more acutely for labs who perform solvent-based extraction and recovery of binder from asphalt mixtures. One alternative is to replace the use of TCE with toluene as outlined in ASTM D2172 (Standard Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures) and ASTM D7906 (Standard Practice for Recovery of Asphalt Binder from Solution Using Toluene and the Rotary Evaporator).
Toluene does not carry the same long-term exposure risks as TCE and is thought to be easier to remove from the binder during the recovery process. However, the flash point of toluene is notably lower than TCE (around 40°F); thus, labs must ensure that storage and handling procedures are updated, and engineering controls are put in place to mitigate any fire risk. For many agencies and organizations, the increased flammability risk makes toluene a non-starter. Additionally, the low flash point means that toluene is incompatible with the closed-loop systems used in auto-extractors.
Where does this leave labs who depend on auto-extraction systems? ASTM D8159 (Standard Test Method for Automated Extraction of Asphalt Binder from Asphalt Mixtures) currently allows for the use of tetrachlorethylene (PCE) and methylene chloride (DCM) as suitable alternatives. Like TCE, PCM and DCM are chlorinated solvents that carry their own risk to human health; if labs make the switch to either of these solvents, care should be taken, including proper personal protective equipment (PPE) such as appropriately rated chemical-resistant gloves, exposure monitors and solvent respirators. Engineering controls are also vital, including walk-in fume hoods to house extraction systems or snorkel vents that limit exposure to fumes.
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The Road Ahead
Implementation of changes will be context-specific, and while innovation may lead to any number of viable alternatives, it will likely take time for these to emerge in the market. Undoubtedly, there will be more questions to arise and challenges that the asphalt industry will face over the course of the TCE transition period. Working together and sharing knowledge can help everyone who depends on these solvents for accurate binder characterization and quality control.
Jason Wielinski is an Asphalt Institute regional engineer based in Ohio. Wes Cooper is the laboratory manager and senior research scientist at the Asphalt Institute Laboratory in Lexington, Kentucky.
Read next: What Asphalt Labs Must Do to Comply With the TCE Ban