BACKGROUND: Many AASHTO standard methods of test require the measurement of temperature. Some of these methods have specified a means for temperature measurement depending upon the application. Liquid-in-glass thermometers as specified by ASTM E1, Standard Specification for ASTM Liquid-in-Glass Thermometers, has often been specified and used by testing laboratories. Generally, these liquid-in-glass thermometers use mercury or a mixture of mercury and thallium, or dyed ethyl alcohol for measurements at extremely low temperatures. Mercury and thallium are considered materials hazardous to human health and the environment; their use in such applications is of concern. There are alternatives to liquid-in-glass thermometers that provide different levels of accuracy, precision, response time, ease of calibration, and practicality of use. Among potential alternatives are platinum resistance thermometers, thermistors, thermocouple devices, and infrared (non-contact) thermometers. There was a need to identify such alternatives and evaluate their appropriateness for use in AASHTO standard methods of test that require the measurement of temperature, and to develop a recommended AASHTO standard practice for the selection of temperature-measuring devices. Such a standard practice will help test laboratories identify and use temperature-measuring devices that are well suited for the test and pose no potential health hazard.
OBJECTIVE: The objective of this research was to develop a recommended AASHTO Standard Practice for Selection of Temperature Measuring Devices. These devices are intended for use, in lieu of liquid-in-glass thermometers, in conducting tests on transportation materials in accordance with AASHTO standard methods of test.
STATUS: Research is complete; final report has been forwarded to the AASHTO Committee on Materials and Pavements for consideration and possible adoption. (NCHRP Staff: Amir N. Hanna).