NCHRP 20-7
Proposed Research Needs Statement
COMP Technical Subcommittee 2b Liquid Asphalts
Lyndi D Blackburn, Chair of TS2b
May 11, 2018
TITLE
Updating the Thermometer Requirements for AASHTO Standards
BACKGROUND/NEEDS STATEMENT
Precise andaccurate temperature measurement is an essential requirement for many AASHTO standard test methods. At present, this requirement is primarily met by the use of liquid-in-glass thermometers specified by ASTM E1, Standard Specification for ASTM Liquid-in-Glass Thermometers. Generally, the liquid used in these is mercury or a mixture of mercury and thallium, although dyed ethyl alcohol is selected when measurements at extremely low temperatures are needed.
Both mercury and thallium are classified as materials hazardous to human health and the environment. There is a concerted effort by regulatory agencies to curtail or eliminate their use in all types of industrial and scientific applications and processes. While mercury thermometers meeting ASTM E1 are still commercially available, NIST no longer provides calibration service for them and an increasing number of state DOTs have prohibited their use.
Low-hazard liquid-in-glass thermometers, standard and industrial platinum resistance thermometers, thermistors, thermocouple devices, and infrared (non-contact) thermometers are potential alternatives to liquid-in-glass thermometers in AASHTO test methods. These alternatives vary greatly in accuracy, precision, response time, ease of calibration and use, and cost from mercury and mercury-thallium thermometers and each other. Adopting them into general AASHTO practice will need to be examined to determine the unique temperature measurement requirements of each test method and any potentially needs for validation, ruggedness testing, or inter-laboratory studies of alternative measurement devices.
Several AASHTO standards have wording after the ASTM E1 thermometer that states that a “suitable alternative” to the mercury or mercury-thallium thermometer can be used. However, this wording leaves a great deal open to interpretation. While the end user may believe that a particular alternative is suitable for their purpose, it may not meet the intended accuracy requirements of the standard, or may not be suitable for the range of temperatures they are measuring. Overall the need exists to develop an AASHTO Standard Practice on the guidance for selection and use of thermometers. There currently exists an urgent need to identify all of the AASHTO Standards that require thermometers and to update them to provide specific alternatives to the traditional liquid-in-glass thermometers.
OBJECTIVES
The objectives of this research are to identify the AASHTO standards will require modifications, to provide alternatives to the traditional liquid-in-glass thermometers, and to develop an AASHTO standard practice for selection and use of thermometers.
WORK TASKS
Tasks anticipated in this project include the following:
(1)Identify and classify current AASHTO standard methods of test that specify the use of ASTM E1 liquid-in-glass thermometers containing mercury or mercury-thallium mixtures;
(2)Determine alternatives in those methods to replace liquid-in-glass thermometers with temperature measurement devices that provide equivalent accuracy, precision, measurement range, and response time at reasonable cost and ease of use;
(3)Provide suggested wording for those standards determined in Task 1 for the alternatives determined in Task 2;
(4)Determine if further study is needed for validation, ruggedness testing, or inter-laboratory studies of alternative measurement devices;
(5)Provide a report including the results of Tasks 1, 2, and 3; and
(6)Provide a draft AASHTO standard for guidance on selection and use for thermometers.
URGENCY
This research need is urgent due to the health and safety issues associated with the current use of liquid-in-glass thermometers containing mercury and thallium, materials classified as hazardous to human health, and to provide alternative temperature measurement devices that provide equivalent accuracy, precision, measurement range, and response time at reasonable cost and ease of use.
FUNDING REQUESTED AND TIME REQUIRED
It is estimated that this research will take 12 months to complete and will require $100,000.
CONTACT PERSON
Lyndi D. Blackburn, P.E.
Alabama Department of Transportation
3700 Fairground Road; Montgomery, AL 36110
Phone: 334-206-2203
Fax: 334-264-6263
Email: