AASHTO T 317:04(2018) Standard Method of Test for Prediction of Asphalt-Bound Pavement Layer Temperatures.
Analysis of deflection data from asphalt pavements almost always requires that the detlections or analysis results be adjusted for the effects of temperature. Measuring the temperature at depth requires that a hole be drilled into the pavement, partially filled with fluid, and the temperature measured with handheld devices. Alternatively, thermistors may be permanently installed at various locations. These processes are time consuming. resulting in a limited number of temperature measurements.
5.2. Current deflection testing equipment is often equipped with surface-temperature—sensing devices, for example, an infrared thermometer that measures the surface temperature at every test location. To adequately adjust the deflection or deflection results for the effects of temperature, the temperature at some depth must be known.
5.3. Utilization of this method results in a significant savings in time over the conventional practice of manually drilling holes into the pavement, and it results in a significant increase in the volume of temperature data (one pavement temperature for each test point).
5.4. The BELLS temperature prediction model was based on temperature measurements made with surf’ace temperature measurements between 0 and 40°C during the unfrozen times of’ the year. Application of BELLS outside of those conditions is not recommended. BELLS has been verified using the LTPP database at both mid-depth and third-depth temperature points. The use of BELLS to predict temperatures at depths shallower than the third point is not recommended.
6.1.1. The surface temperature measurement device can be an IR thermometer mounted on a deflection device, a handhcld IR thcrmomctcr, or a surface contact thermometer. The temperature measurement device should be calibrated according to the manufacturer’s recommendations.
Note 1—The JR surface temperature is the most significant variable in the BELLS regression equation presented in Section 7.1.1. Thus, it is important that users verify the calibration of the surface temperature measurement device in the application of the equation (FHWA-HRT-06- 132).AASHTO T 317 pdf download.